To see the other types of publications on this topic, follow the link: Ni-Based catalysts.
Dissertations / Theses on the topic 'Ni-Based catalysts'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 dissertations / theses for your research on the topic 'Ni-Based catalysts.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
Miranda, Morales Bárbara Cristina. "HYDROGENOLYSIS OF GLYCEROL OVER NI-BASED CATALYSTS." Doctoral thesis, Universitat Rovira i Virgili, 2014. http://hdl.handle.net/10803/284041.
Full textAbstract:
La demanda de energía en el mundo va en aumento año a año. Los sistemas de producción y patrones de consumo actuales son insostenibles. Existe la necesidad de desarrollar nuevas formas de satisfacer no sólo, la demanda de energía y producción de compuestos químicos, sino también de encontrar una forma de hacerlo que sea amigable con el ambiente. El glicerol, como recurso biomásico, representa una alternativa a esto. El catalizador cumple un papel clave en el mecanismo de rompimiento de los enlaces C-C y C-O del glicerol, y modula la selectividad hacia los productos deseados. Debido a esto, el presente trabajo de investigación desea contribuir en el desarrollo de catalizadores para su aplicación en la transformación catalítica de glicerol a productos químicos de alto valor. Además, ayudar al entendimiento de la relación entre la estructura del catalizador y la actividad catalítica. La atención de esta investigación se centra en la conversión de glicerol sobre catalizadores de níquel, cuya principal desventaja es su baja estabilidad debido a la deposición de carbón. Cómo mejorar la estabilidad de los catalizadores de níquel es aún un tema de debate. Se estudió la conversión catalítica de glicerol en fase gas sobre un catalizador de Ni/γ-Al2O3 a presión atmosférica, 573 K y en presencia de hidrógeno en un reactor de lecho fijo. La temperatura de reducción del catalizador fue empleada como parámetro para evaluar su efecto sobre la actividad catalítica. Además, el efecto de la introducción de Cu en el catalizador de Ni/γ-Al2O3 sobre la conversión del glicerol fue también estudiado. Diferentes razones atómicas Ni/Cu (8/1, 4/1, 2/1, 1/1, 1/2, 1/4, 1/8) fueron estudiadas.World demand for energy, chemicals and products is increasing every year. Current production systems and consumption patterns are now unsustainable. New alternative ways must be developed to satisfy not only the energy needs and the production of chemicals but also for a more friendly effect on the environment. Biomass resources such as glycerol represent one alternative to this. The catalyst role in the mechanism of the cleavage of the C-C and C-O bonds which modulates the routes in the glycerol conversion is the key to control the selectivity to target products. Because of that, this research work wishes to contribute with the development of catalysts for the catalytic transformation of glycerol to high value-added chemicals, and to understand the catalyst structure relationship with the catalytic performance. The attention of the present research is devoted to the glycerol hydrogenolysis over Ni based catalysts. The catalytic conversion of glycerol in gas phase over Ni/γ-Al2O3 catalyst at atmospheric pressure and 573 K in the presence of hydrogen in a fixed bed reactor was studied. Different reduction temperatures of the Ni samples were used as parameter to evaluate its effect on the catalytic performance. Then, the effect of Cu introduction into Ni in the catalytic glycerol conversion was also studied. Different Ni/Cu atomic ratios of 8/1, 4/1, 2/1, 1/1, 1/2, 1/4, 1/8 were studied.
2
Cárdenas-Arenas, Andrea. "Ni-based catalysts supported on CeO2 for CO2 valorisation." Doctoral thesis, Universidad de Alicante, 2021. http://hdl.handle.net/10045/115053.
Full textAbstract:
Esta Tesis Doctoral se ha enfocado en el diseño y síntesis de catalizadores de NiO-CeO2 para la metanación de CO2 y el reformado seco de metano, como alternativas para la revalorización de CO2. Concretamente, se ha estudiado el mecanismo de reacción de la metanación de CO2 sobre sistemas catalíticos NiO-CeO2 y se han optimizado los sitios activos implicados en esta reacción. Además, se ha estudiado la influencia de la morfología de los catalizadores NiO-CeO2 en su comportamiento catalítico para la reacción de metanación de CO2 utilizando diferentes tipos de materiales, como nanopartículas, nanopartículas soportadas, 3DOM, catalizadores macroporosos convencionales y xerogeles de carbón. Finalmente, se ha diseñado un catalizador basado en nanopartículas y se ha estudiado sus propiedades catalíticas para la reacción de reformado seco de metano.
3
Albarazi, Abdulkader. "Development of Ni-based catalysts for methane dry reforming application." Paris 6, 2013. http://www.theses.fr/2013PA066814.
Full text
4
Houache, Mohamed Seif Eddine. "Efficient Nanostructured Ni-Based Catalysts for Electrochemical Valorization of Glycerol." Thesis, Université d'Ottawa / University of Ottawa, 2020. http://hdl.handle.net/10393/41208.
Full textAbstract:
The biodiesel industry produces millions of kilograms of low-value glycerol, which must be either stored or disposed of, creating environmental concerns. Even though glycerol is utilized as a raw material within various industries its supply is still superior to the demand. Upgrading this biodiesel by-product into value-added products using electrochemical technologies is a promising approach and will make biodiesel production more environmentally friendly with added financial benefits.
Precious metals are the state-of-the-art electro-catalysts for the oxidation of organic compounds, and so are a logical choice for the electro-oxidation of glycerol. Two factors that hinder their use in this regard for commercial applications include their cost and susceptibility to poisoning by the carbonyl (CO) species formed during the electro-oxidation process. The use of inexpensive transition metals as the principal metals in a catalyst composite is thus appealing, leading to the selection of nickel (Ni). Furthermore, its high activity, anti-poison ability and long-term stability in alkaline solutions make it an attractive candidate for glycerol electrooxidation reaction (GEOR).
The main thrust of this work is to develop a deeper understanding of the factors involved in controlling the selectivity of the product reaction without 3 carbon cleavage on non-precious metal surfaces.
To overcome a trial-and-error approach, we took advantage of modern synthesis and characterization techniques for metal alloy nanoparticles and advances in rapid identifications and quantifications of products based on infrared spectroscopy. These tools were expected to provide the foundation for the detailed understanding of GEOR mechanism hence would pave the way for the rational design of catalysts to produce specific high value-added chemicals.
We cared out extensive research to determine the effect of size, morphology, shape, support, experimental conditions and catalyst preparation methods on the catalytic performance of Ni. The thesis aims to demonstrate how the selectivity of unsupported Ni nanoparticles for GEOR can be improved via interaction of Ni with low noble and transition metals content. Enhanced selectivity towards C3 and C2 products such as glycerate, lactate, oxalate and tartronate, was achieved by simply adding less than 20 atomic percent of any of bismuth (Bi), Pd or Au onto Ni nanoparticles. Furthermore, the composition effect of carbon supported NiₓM₁₋ₓ (M = Bi, Pd and Au) nanomaterials were combined with Pt/C and commercial silver nanoparticles for cathodic hydrogen production and CO₂ electro-reduction, respectively. These rich-phase of Ni(OH)₂ catalysts were highly active and selective towards C-C bond breaking products leading to 100% selectivity of formate after 1 hr electrolysis and 100% conversion of glycerol after 24 hr at +1.55 V. Lastly, the first principles calculations based on the density functional theory (DFT) insights provided an explanation to understand the electronic structure, magnetism and reactivity of our catalysts. Core@shell (Mm@Nin) nanoparticles of 13-, 54- and 55-atoms with different elements concentrations matched the experimental results and assisted us with a better understanding of some of the microscopic phenomena involved with the reactivity of bimetallic nanoparticles.
5
Mukka, Mayuri. "Parametric study of the partial oxidation of propane over Ni and Pt based catalysts." Morgantown, W. Va. : [West Virginia University Libraries], 2010. http://hdl.handle.net/10450/11243.
Full textAbstract:
Thesis (M.S.)--West Virginia University, 2010.Title from document title page. Document formatted into pages; contains xiii, 130 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 125-129).
6
González, Arcos Angélica Viviana. "RhPt and Ni based catalysts for fuel reforming in energy conversion." Doctoral thesis, KTH, Kemisk teknologi, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-160026.
Full textAbstract:
Although current trends in global warming are of great concern, energy demand is still increasing, resulting in increasing pollutant emissions. To address this issue, we need reliable renewable energy sources, lowered pollutant emissions, and efficient and profitable processes for energy conversion. We also need to improve the use of the energy, produced by existing infrastructure. Consequently, the work presented in this thesis aims at investigating current scientific and technological challenges in energy conversion through biomass gasification and the alternative use of fossil fuels, such as diesel, in the generation of cleaner electricity through auxiliary power units in the transport sector. Production of chemicals, syngas, and renewable fuels is highly dependent on the development and innovation of catalytic processes within these applications. This thesis focuses on the development and optimization of catalytic technologies in these areas. One of the limitations in the commercialization of the biomass gasification technology is the effective catalytic conversion of tars, formed during gasification. Biomass contains high amounts of alkali impurities, which pass on to the producer gas. Therefore, a new material with alkali tolerance is needed. In the scope of this thesis, a new catalyst support, KxWO3 – ZrO2 with high alkali resistance was developed. The dynamic capability of KxWO3 – ZrO2 to store alkali metals in the crystal structure, enhances the capture of alkali metals "in situ". Alkali metals are also important electronic promoters for the active phase, which usually increases the catalysts activity and selectivity for certain products. Experimental results show that conversion of 1-methylnaphathalene over Ni/KxWO3 – ZrO2 increases in the presence of 2 ppm of gas-phase K (Paper I). This support is considered to contribute to the electronic equilibrium within the metal/support interface, when certain amounts of alkali metals are present. The potential use of this support can be extended to applications in which alkali "storage-release" properties are required, i.e. processes with high alkali content in the process flow, to enhance catalyst lifetime and regeneration. In addition, fundamental studies to understand the adsorption geometry of naphthalene with increasing temperature were performed in a single crystal of Ni(111) by STM analyses. Chapter 9 presents preliminary studies on the adsorption geometry of the molecule, as well as DFT calculations of the adsorption energy. In relation to the use of clean energy for transport applications, hydrogen generation through ATR for FC-APUs is presented in Papers II to V. Two promoted RhPt bimetallic catalysts were selected in a previous bench scale study, supported on La2O3:CeO2/d – Al2O3 and MgO : Y2O3/CeO2 – ZrO2. Catalyst evaluation was performed in a fullscale reformer under real operating conditions. Results showed increased catalyst activity after the second monolithic catalyst due to the effect of steam reforming, WGS reaction, and higher catalyst reducibility of the RhxOy species in the CeO2 – ZrO2 mixed oxide, as a result of the improved redox properties. The influence of sulfur and coke formation on diesel reforming was assessed after 40 h on stream. Sulfur poisoning was evaluated for the intrinsic activity related to the total Rh and Pt area observed after exposure to sulfur. Sulfur concentration in the aged catalyst washcoat was observed to decrease in the axial direction of the reformer. Estimations of the amount of sulfur adsorbed were found to be below the theoretical equilibrated coverage on Rh and Pt, thus showing a partial deactivation due to sulfur poisoning.QC 20150213
7
Moni, Lucky. "Ni(II) and Pd(II) based catalysts for α-olefin polymerisation." Master's thesis, University of Cape Town, 1999. http://hdl.handle.net/11427/9955.
Full text
8
Yan, Wei. "Nickel-based Catalysts for Urea Electro-oxidation." Ohio University / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1391419479.
Full text
9
Cao, Pengfei. "The development of Ni based catalysts for carbon dioxide reforming of methane." Thesis, University of Nottingham, 2017. http://eprints.nottingham.ac.uk/46876/.
Full textAbstract:
Recently, with the rapid development of human society, meeting energy demand and controlling climate change are becoming urgent issues. Carbon dioxide (dry) reforming of methane (DRM) has been considered as a promising technology as it utilizes greenhouse gas to provide high value added liquid fuel and chemicals coupling with a Fischer-Tropsch (F-T) process. In other words, this process can both improve supply of liquid fuel and eliminate global warming issues. Since deactivation of catalysts is the major obstacle for commercialization of this approach, deep understanding of this process and development of catalysts with high activity and stability are necessary to be studied. Firstly, a comprehensive thermodynamic analysis of DRM and its side reactions was performed to get a deep understanding of this process. Low CH4/CO2 ratios improve CH4 conversion and CO selectivity, but have negative influence on CO2 conversion and H2 selectivity. While, CH4 conversion, CO2 conversion (T ≥ 630°C), H2 selectivity CO selectivity and carbon formation are all enhanced at high pressures. Severe carbon formation is found at the temperature range of 546 and 703 °C, and carbon free regime is suggested under operating conditions of T ≥ 1000 °C, CH4/ CO2 mole ratio = 1 and pressure = 0.1 MPa. In addition, an index about the relationship of H2/CO mole ratio and operating conditions was established in this study. It is beneficial in both process efficiency and economics in practice as the index can be used to guide the selection of appropriate operating conditions to tune H2/CO mole ratio in syngas to satisfy different requirements of different F-T processes. As drying process has big influence on structure formation of catalysts, the effects of oven drying and vacuum freeze drying on the performance of Ni/Al2O3 in DRM were investigated. The sublimation process in vacuum freeze drying increased the BET surface area but maintain small and uniform pore structure which protect NiO particle from aggregation. Besides, since the solid ice settled nickel nitrate salt in preparation stage, the aggregation of NiO after calcination is also suppressed. Comparing to oven dried catalyst (OD-Cat), anti-deactivation of vacuum freeze dried catalyst (VFD-Cat) was enhanced, which is due to small Ni particle size and high Ni dispersion. The CO2-TPD analysis shows that the amount of basicity on catalyst VFD-Cat is more than it on catalyst OD-Cat, which helps to eliminate coke formation by enhanced the adsorption and activation of CO2. Furthermore, less carbon deposition and less graphic degree coke was detected on spent catalyst VFD-Cat. Overall, vacuum freeze drying technique is suggested to synthesis catalysts for DRM to improve its stability and resistance of coke formation. In this study, the effects of calcination method (i.e. microwave and furnace) on activity and stability of catalyst Ni/Al2O3 were also studied. Microwave calcined catalyst (MC-Cat) showed a better catalytic performance than furnace calcined catalyst (FC-Cat) because of a slow deactivation rate. Because of the advantage of homogeneous volume heating in microwave calcination process, lager total surface area of catalyst and smaller Ni particle with uniform size were observed on catalyst MC-Cat than it on catalyst FC-Cat. Moreover, the amount of basic sites on catalyst MC-Cat was increased under microwave heating, which is contribution to coke formation with less amount and lower graphic degree. Therefore, microwave calcination is suggested to improve the resistance of catalytic deactivation caused by coke deposition. Additionally, the energy saving is more than 90% for microwave calcination in this case as microwave heating is a fast and energy efficiency. To improve the stability of catalyst Ni/γ-Al2O3 in carbon dioxide reforming of methane, K2CO3 was introduced as a promoter to enhance the coke resistance of catalyst. From the results, catalyst promoted with K2CO3 (K-Ni-Al) showed a relative high activity and stability in 100 h of DRM reaction. During long term test, the activity decreased at first 20h then became stable. As K2CO3 has advantages such as high specific heat, good thermal stability, strong basicity and fast heat transfer, it can increase basicity on the surface, control Ni particle size during both reduction and reaction stages, and increase the number of active metallic Ni by weaken the metal-support interactions. Moreover, it was found that that K2CO3 could react with carbon deposition, which could build a micro-cycle to eliminate coke formation.
10
Pegios, Nikolaos [Verfasser], Regina [Akademischer Betreuer] Palkovits, and Matthias [Akademischer Betreuer] Wessling. "Ni-based catalysts for the dry reforming of methane / Nikolaos Pegios ; Regina Palkovits, Matthias Weßling." Aachen : Universitätsbibliothek der RWTH Aachen, 2018. http://d-nb.info/117652805X/34.
Full text
11
Pegios, Nikolaos Verfasser], Regina [Akademischer Betreuer] [Palkovits, and Matthias [Akademischer Betreuer] Wessling. "Ni-based catalysts for the dry reforming of methane / Nikolaos Pegios ; Regina Palkovits, Matthias Weßling." Aachen : Universitätsbibliothek der RWTH Aachen, 2018. http://d-nb.info/117652805X/34.
Full text
12
Daoura, Oscar. "Towards anti-coking and anti-sintering Ni@Silica based catalysts for the dry reforming of methane." Electronic Thesis or Diss., Sorbonne université, 2019. http://www.theses.fr/2019SORUS679.
Full textAbstract:
Le reformage à sec du méthane est un processus de conversion de CH4 et CO2 en H2 et CO ou gaz de synthèse avec un rapport molaire de 1, lequel peut servir comme matière première pour la production de carburant liquide par Fischer-Tropsch. Les catalyseurs à base de nickel sont des candidats prometteurs pour cette réaction. Ils présentent une très bonne activité, sont peu coûteux et sont plus disponibles en comparaison avec les matériaux à base de métaux nobles, mais ils se désactivent par frittage et dépôt du coke. La stabilisation de Ni par confinement et/ou par amélioration de la dispersion et de l'interaction des nanoparticules avec la silice font/fait partie des méthodes les plus efficaces et moins coûteuses pour lutter contre la désactivation lors du reformage, ce qui correspond à l’objectif principal de ce travail. Ainsi, de nouveaux catalyseurs à base de Ni, ont été synthétisés, caractérisés et testés en catalyse de reformage à sec de CH4. Trois points principaux ont été examinés: (i) Le test de l’efficacité de nouveaux supports mésoporeux (MCF) en variant la nature des précurseurs de Ni (sels ou colloïdes) incorporés par imprégnation ou synthèse directe après ajustement du pH, (ii) la préparation de monolithes mésoporeux de type SBA-15 avec une très bonne dispersion de Ni incorporé par voie « one-pot », (iii) le contrôle de la dispersion, de la taille des particules de Ni et donc de l’interaction avec de la silice non poreuse via la formation de phyllosilicates de Ni. Au final, les monolithes de type SBA-15 incluant Ni par voie « one-pot » et les particules de Ni0 issues de la réduction des phyllosilicates se sont avérés être les catalyseurs les plus performantsDry reforming of methane is a process for the conversion of CH4 and CO2 into “syngas”, a gaseous mixture of H2 and CO (with a molar ratio value of 1) that can serve as feedstock for the production of liquid fuel by the mean of Fischer-Tropsch procedure. Nickel-based catalysts are promising candidates for this reaction displaying high activity, lower cost and wider availability than noble metal-based materials but deactivating by sintering and/or coke deposition. Stabilization of Ni0 nanoparticles within siliceous supports either by confinement and/or by improving their dispersion and interaction with the support are among the best and the less expensive methods to overcome the deactivation in dry reforming which represents the main objective for this work. Here, new stable nickel-based catalysts were synthesized, characterized and tested in dry reforming. Three main issues were examined: (i) Testing the efficiency of new mesoporous supports (mesocellular silica foams) using different nickel precursors (salt or colloidal form) incorporated by impregnations or pH adjustment assisted one-pot methods, (ii) designing highly dispersed nickel-based mesoporous monoliths through an original sol-gel method (iii) controlling the nickel size, dispersion and therefore its interaction with the support onto non-porous silica carriers by the mean of phyllosilicates. Monoliths of the SBA-15 type incorporating Ni0 by a one-pot method, and Ni0 obtained through the reduction of nickel phyllosilicates turned out to be the most stable and efficient catalysts
13
Yu, Zhiqiang. "Transient Studies of Ni-, Cu-Based Electrocatalysts in CH4 Solid Oxide Fuel Cell." Akron, OH : University of Akron, 2007. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=akron1194625466.
Full textAbstract:
Dissertation (Ph. D.)--University of Akron, Dept. of Chemical Engineering, 2007."December, 2007." Title from electronic dissertation title page (viewed 03/12/2008) Advisor, Steven S. C. Chuang; Committee members, Lu-Kwang Ju, Edward Evans, W. B. Arbuckle, Stephen Z. D. Cheng; Department Chair, Lu-Kwang Ju; Dean of the College, George K. Haritos; Dean of the Graduate School, George R. Newkome. Includes bibliographical references.
14
Pane, Flavia. "Kinetic analysis of Phenol Steam Reforming over Rh and Ni-Co based catalysts: identification of reaction’s pathway." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2022.
Find full textAbstract:
Great research efforts have been made during the last decades for the development and production of sustainable energy through renewable sources.Hydrogen has been considered a clean fuel and it can be produced from biomass,whose pyrolysis leads to the production of bio-oil that contains many components,which are the most renewable energy carriers.Phenol is the major component of the bio-oil and its catalytic steam reforming provides a promising technique for hydrogen production.The present work provides an extensive kinetic study of the mechanisms that occurs in the PSR,where the effect of temperature,space-time and partial pressure of the reactants(phenol and water)is investigated using two different catalysts over the same support.Due to the good metal-support interaction,Rh and Ni-Co active metals and γ-Al2O3 support have been selected and they were found to be appropriate catalysts with long-term stability for the hydrogen production via PSR,with Rh presenting the better performance in respect to transient metal-based catalysts.Identification of primary and secondary products revealed the reaction mechanism to be affected by the metal.On Rh, phenol is adsorbed with its aromatic ring in parallel with Rh,suggesting that the C-C bond activation is leading the reaction mechanism;on Ni-Co is observed the phenol dissociative adsorption producing phenoxyl and benzene species,suggesting the O-H and C-O bond activation happens first,followed by decomposition and reforming reactions.At lower temperatures,phenol dehydrogenation,dehydroxylation and decomposition were found to be the main reaction pathways,whereas at higher temperatures reforming and water gas shift reactions became enhanced.The excess of water was able to promote the WGS reaction.Time-on-stream studies at 500°C revealed Rh/γ-Al2O3 to have a good balance between stability,activity and selectivity.Oxidation of spent catalysts were also performed,in order to identify the type of carbonaceous deposits.
15
Law, Yeuk Ting. "Investigation of reaction networks and active sites in ethanol steam reforming reaction over Ni and Co-based catalysts." Phd thesis, Université de Strasbourg, 2013. http://tel.archives-ouvertes.fr/tel-00869963.
Full textAbstract:
Bimetallic catalysts have been widely exploited to improve the performance of various catalytic reactions. Understanding the surface properties and in particular, bimetallic interaction and support effect of the catalytic components is an important step towards rational catalyst design. In this thesis, Ni-Co thin film on polar ZnO single crystal was studied as a model catalyst for ethanol steam reforming reaction. The aim is to provide fundamental understanding of how the surface characteristics of the catalyst influence the mechanism and the efficiency of the reaction. This study focused firstly on the study of the interaction between Ni and Co in oxidative environment using Xray photoelectron spectroscopy (PES). Oxidation of Co is favoured over nickel and the surface is enriched with cobalt oxide. Secondly, Ni-Co thin film supported on polar Zn and O terminated ZnOwas studied by synchrotron based PES. The as deposited layer interacts readily with ZnO and Co is partially oxidized upon deposition, even at room temperature. The interaction of ethanol with Ni- Co/ZnO-Zn was studied by thermal desorption spectroscopy (TDS). Ethanol decomposes in different pathways on Ni and Co, in which C-C bond scission and methane production are favoured on Ni/ZnO-Zn while dehydrogenation is favoured on Co/ZnO-Zn. Finally, Ni-Co powder was studied byin-situ ambient pressure PES under reaction conditions in order to clarify the correspondence between the active state of the catalyst and the reaction activity. The product selectivity on Co catalyst is distinctly different from Ni and Ni-Co. Also, the decomposition of methyl group and the high amount of CO produced over Co is likely to be the cause for its high level of carbon deposition.
16
Wilson, Karen E. "Investigations into the role of α-amino acids as chiral modifiers for Ni-based enantioselective heterogeneous hydrogenation catalysts." Thesis, University of St Andrews, 2011. http://hdl.handle.net/10023/3108.
Full textAbstract:
The hydrogenation of β-ketoesters over chirally modified Ni catalysts is a celebrated and thoroughly researched example of an enantioselective heterogeneous catalytic reaction. Enantioselective heterogeneous processes, although extremely attractive in terms of fewer complications in the separation of products from the catalyst, are hindered in their viability as industrial applications due to the lack of detailed knowledge on how chirality is conferred to the metal surface. Surface science techniques have afforded substantial progress into determining mechanisms between modifier, reactant and catalyst to explain the source of enantioselectivity of the system. In this study, a combination of solution and ultra-high vacuum (UHV)-based experiments allow a more realistic interpretation of the surface chemistry underpinning the catalytic reaction as the key step in achieving enantioselective performance is the adsorption of chiral modifiers from solution. The behaviour of (S)-aspartic acid and (S)-lysine on Ni{111} and their interaction with the prochiral β-ketoester methylacetoacetate is investigated in this study to understand their potential as chiral modifiers for the system. In UHV, scanning tunnelling microscopy (STM), reflection absorption infrared spectroscopy (RAIRS), and temperature programmed desorption (TPD) are used to analyse the conformation and order of the amino acids on the metal, and their thermal stability. Additionally, liquid-solid interface RAIRS and X-ray photoelectron spectroscopy (XPS) are used to examine the modified Ni surface, prepared under aqueous conditions, to give an accurate representation of the catalytic studies. It has been found highly likely that, for (S)-aspartic acid modified Ni{111}, enantioselective sites exist at step or step/kink defects, formed by corrosive leaching of the Ni substrate. Conversely, lysine appears to bind with a high sticking probability to Ni, in the form of lysine islands, and does not appear to etch the Ni chirally. Finally, similar experiments have been carried out on Au{111}, where lysine was found to chiral restructure the surface and form nanofingers, and 2D Ni clusters grown on Au{111} in order to investigate the formation of possible metal-organic frameworks.
17
Gehrtz, Paul Henry [Verfasser], and Ivana [Akademischer Betreuer] Fleischer. "Pd- and Ni-based catalysts for mild C-S bond activation and formation / Paul Henry Gehrtz ; Betreuer: Ivana Fleischer." Tübingen : Universitätsbibliothek Tübingen, 2020. http://d-nb.info/120277394X/34.
Full text
18
Gehrtz, Paul [Verfasser], and Ivana [Akademischer Betreuer] Fleischer. "Pd- and Ni-based catalysts for mild C-S bond activation and formation / Paul Henry Gehrtz ; Betreuer: Ivana Fleischer." Tübingen : Universitätsbibliothek Tübingen, 2020. http://d-nb.info/120277394X/34.
Full text
19
Karam, Leila. "New routes of preparation of active and stable mesoporous Ni-alumina based catalysts for methane dry reforming and CO2 methanation." Electronic Thesis or Diss., Sorbonne université, 2019. https://accesdistant.sorbonne-universite.fr/login?url=https://theses-intra.sorbonne-universite.fr/2019SORUS163.pdf.
Full textAbstract:
Le reformage à sec du méthane (DRM) est un processus qui convertit simultanément CH4 et CO2 en un mélange gazeux de H2 et de CO appelé syngas. Les catalyseurs à base de Ni sont particulièrement prometteurs mais ils ne sont pas stables en raison du frittage du Ni et du dépôt de coke. Dans cette thèse, nous avons développé deux voies de synthèse de catalyseurs mésoporeux à base de Ni-Al2O3 dans lesquels Ni est stabilisé dans l'oxyde, ce qui donne une activité et une stabilité élevées en DRM. Des techniques physicochimiques complémentaires ont été appliquées pour identifier les propriétés des matériaux à toutes les étapes de préparation et d'activation. La première approche comprend la synthèse « EISA one-pot » de matériaux mésoporeux Ni-Mg-Al2O3. L’échantillon à base de 15% en poids de Mg (charge optimale) contribue à une dispersion élevée et homogène de Ni et de Mg tout en préservant la qualité structurale de la matrice Al2O3 mésoporeuse. La basicité accrue renforce l'activité et la stabilité. La seconde méthode consiste à synthétiser des matériaux mésoporeux Ni-Al2O3 innovants en utilisant une structure organométallique (MOF) comme matrice sacrificielle. Cette procédure permet la formation de petites nanoparticules de Ni stabilisées de manière homogène dans le support de grande surface spécifique, insensibles au frittage et à la formation de nanotubes de carbone lors de la réaction de DRM. Les tests catalytiques complétés par des calculs thermodynamiques montrent l’efficacité des matériaux synthétisés non seulement pour le reformage à sec du méthane, mais également pour la méthanation du CO2 et le reformage à sec de biogaz issu de pyrolyseDry reforming of methane (DRM) is a process that converts CH4 and CO2 gases into syngas, a gaseous mixture of H2 and CO. Ni based catalysts proved to be suitable for the reaction due to their good activity, wider availability and lower cost than noble-based materials. However, these catalysts are not stable due to Ni sintering and coke deposition. In this thesis we developed two different synthesis routes of mesoporous Ni-Al2O3 based catalysts that can occlude Ni inside the pores achieving high activity and stability in DRM. A set of complimentary physicochemical techniques was systematically applied to thoroughly investigate the materials properties at all steps of preparation and activation. The first approach embraces synthesis of mesoporous Ni-Mg-Al2O3 materials by one-pot EISA strategy. Results demonstrate that 15 wt% Mg (optimum loading) based sample contribute to high and homogenous dispersion of both Ni and Mg, preserving ordered mesoporous Al2O3 walls. The good structural and textural characteristics in addition to the enhanced basicity reinforce activity and stability. The second method involves synthesizing new mesoporous Ni-Al2O3 materials using metal-organic framework as sacrificial template. This procedure results in small Ni nanoparticles homogeneously dispersed and stabilized within the high surface area support resisting sintering and inhibiting carbon nanotubes formation during reforming reaction. Based on catalytic tests completed by thermodynamics calculations, the synthesized materials proved to be eficient not only for dry reforming of methane, but also for CO2 methanation reaction and dry reforming of waste pyrolysis products
20
Hasrack, Golshid. "Tailoring Selectivity with Different Plasma Sources." Electronic Thesis or Diss., Sorbonne université, 2022. http://www.theses.fr/2022SORUS402.
Full textAbstract:
L'un des plus grands défis de l'humanité en ce siècle est la lutte contre l'augmentation constante des gaz à effet de serre dans l'atmosphère, en particulier du dioxyde de carbone CO2. Diminuer ou stabiliser ces émissions en développant des solutions innovantes afin de capter et transformer (CCU) le CO2 inévitablement produit par les gaz sont challenges majeurs pour les prochaines décennies. Dans cette étude, nous nous concentrerons sur la réaction de méthanation du CO2 (réaction de Sabatier) comme une approche prometteuse pour la réduction du CO2 puisque le méthane généré peut être facilement stocké dans le réseau de gaz existant ou utilisé comme matière première pour la production de produits chimiques précieux. En évitant les conditions critiques, comme les hautes températures et pressions nécessaires dans l'approche thermique conventionnelle et en augmentant les exigences d'une production flexible par énergie renouvelable, il est possible de combiner la technologie plasma avec la catalyse. Malgré le fait que les principes généraux de la catalyse par plasma soient décrits dans la bibliographie, il s'agit encore d'un nouveau domaine de recherche avec de nombreux aspects non résolus à découvrir. Ainsi, dans ce travail, nous tenterons de montrer certains de ces aspects en étudiant l'impact des effets de promotion sur les propriétés du plasma dans un réacteur plasma à décharge à barrière diélectrique "DBD" à lit fixe, permettant de mettre en évidence la synergie entre le plasma et le catalyseur. Cette thèse, en tant qu'étude multidisciplinaire, se concentrera dans un premier temps sur l'effet des promoteurs et leur chargement optimal sur le catalyseur Ni/CeO2 pour la réaction de méthanation du CO2 en présence du plasma. Dans un deuxième temps, cette série de catalyseurs sera intentionnellement supportée sur des zéolites HUSY afin d'étudier l'effet des propriétés physico-chimiques du catalyseur à base de zéolite sur l'efficacité énergétique de la méthanation du CO2. Ce travail permettra d'établir une nouvelle méthodologie pour sélectionner les catalyseurs à base de zéolite les plus appropriés en termes d'efficacité énergétique pour la méthanisation du CO2 par plasma DBD. De cette façon, nous espérons ouvrir de nouvelles perspectives pour améliorer la synergie entre le plasma et le matériau de garnissage, afin de contribuer à la transition vers un avenir durableOne of the greatest challenges for humanity in this century is the fight against the constant increase of greenhouse gases in the atmosphere, in particular carbon dioxide CO2. Declining or stabilizing these emissions by developing innovative solutions in order to capture and transform (CCU) the inevitably gas produced CO2 are major challenges for the next decades. Here in this study, we will focus on the CO2 methanation reaction (Sabatier reaction) as a promising approach for CO2 reduction since the generated methane can be readily stored in the existing gas network or used as raw materials for valuable chemical production. By avoiding the critical conditions of high temperatures and pressure needed in conventional thermal approach and intersecting the requirements for flexible production by renewable energy can be achieved by combining plasma technology with catalysis. Despite the fact that the general principles of plasma catalysis are described, it is yet a new field of research with many unsolved aspects to be discovered. Hence, in this work, we will attempt to show some of these aspects by studying the impact of promotional effects on plasma properties in a packed bed Dielectric Barrier Discharge “DBD” plasma reactor, which allow to highlight the synergy between plasma and the catalyst. This PhD thesis as a multidisciplinary study, first will focus on the effect of promoters and their optimum loading on Ni/CeO2 catalyst for the CO2 methanation reaction in the presence of the plasma. In the second step this series of catalysts will be intentionally supported on HUSY zeolites to investigate the effect of physicochemical properties of the zeolite-based catalyst on the energy efficiency of CO2 methanation. This work will grant a new methodology to select the most appropriate zeolite-based catalysts in terms of energy efficiency for DBD plasma catalytic CO2 methanation. Under this way, we hope to open new insights to further improve the synergy between the plasma and the packing material, in order to help with the transition towards a sustainable future
21
Ehrmaier, Andreas [Verfasser], Johannes A. [Akademischer Betreuer] Lercher, Johannes A. [Gutachter] Lercher, and Klaus [Gutachter] Köhler. "Dimerization of 1-Butene on Ni Based Solid Catalysts / Andreas Ehrmaier ; Gutachter: Johannes A. Lercher, Klaus Köhler ; Betreuer: Johannes A. Lercher." München : Universitätsbibliothek der TU München, 2019. http://d-nb.info/1191897273/34.
Full text
22
Arapova, Marina. "Synthesis and properties of the Ni-based catalysts for the valorization of ethanol and glycerol via steam reforming reaction for hydrogen production." Thesis, Strasbourg, 2017. http://www.theses.fr/2017STRAF031/document.
Full textAbstract:
Les trois familles catalytiques à base de perovskites contenant du Ni: massives [[LnFe1-x-yNiyMxO3-δ] (Ln=La, Pr; B=Co, Mn, Ru), sur support [mLnNi0.9Ru0.1О3/nMg-γ-Al2O3] (Ln = La, Pr) et structuré [mLaNi0.9Ru0.1О3/nMg-γ-Al2O3/mousses structurées] ont été synthétisés, caractérisés et testés dans les réactions de vaporeformage de l'éthanol et de glycérol. Les effets de la composition chimique et de la méthode de synthèse sur les propriétés structurelles et texturales, ainsi que sur la réductibilité des échantillons initiaux ont été évalués. L'utilisation préférentielle de Pr, Ni et Ru dans la composition de catalyseur a été démontrée pour toutes les familles. Le rôle essentiel de la modification du support γ-Al2O3 avec ≥ 10%mass de Mg introduit par imprégnation humide pour le catalyseur supporté a également été prouvé. Des catalyseurs de la composition optimale fournissant une activité élevée dans le vaporeformage de l'éthanol et du glycérol à T = 650 °C ont été trouvés: le meilleur catalyseur massif à base du précurseur PrFe0.6Ni0.3Ru0.1O3 fournit une activité élevée pendant au moins 7 h, grâce à la facilité de leur réduction et les propriétés d'oxydoréduction de l'oxyde de praséodyme formé. Les catalyseurs sur support 10-20% PrNi0.9Ru0.1O3/10-15%Mg-γ-Al2O3 fournissent le meilleur rendement en hydrogène (~ 90%) et la stabilité pendant ~ 20 heures. Le catalyseur structuré optimisé à base de la plaquette Ni-Al métallique fournit le rendement stable en hydrogène 80-87% dans l’oxy-vaporeformage d'éthanol dans les mélanges concentrés (concentration d'éthanol de 30%) dans un réacteur pilote pendant 40 heures. Les résultats obtenus rendent ces systèmes catalytiques structurés très prometteurs à utiliser dans les générateurs électrochimiques à base de piles à combustible avec l'utilisation de ressources renouvelables peu coûteuses comme bio-huileThe three catalytic families based on Ni-containing perovskites: massive [LnFe1-x-yNiyMxO3-δ] (Ln=La, Pr; B=Co, Mn, Ru), supported [mLnNi0.9Ru0.1О3/nMg-γ-Al2O3] (Ln = La, Pr) and structured [mLaNi0.9Ru0.1О3/nMg-γ-Al2O3/structured foams] were synthesized, characterized and tested in the reactions of the ethanol and glycerol steam reforming. The effects of the chemical composition and synthesis method on the structural and textural properties, as well as on reducibility of initial samples were evaluated. The preferred use of Pr, Ni and Ru in the catalyst composition was shown for all families. The essential role of the effective γ-Al2O3 support modification with the ≥10 % wt. of Mg introduced by wetness impregnation for the supported catalyst was also proved. Catalysts of the optimal composition providing a high activity in steam reforming of both ethanol and glycerol at T= 650 °С were found: the best massive catalyst based on the PrFe0.6Ni0.3Ru0.1O3 precursor provides high activity for at least 7 hours, which is explained by the ease of their reduction and the oxidation-reduction properties of the praseodymium oxide formed. Supported 10-20% PrNi0.9Ru0.1O3/10-15%Mg-γ-Al2O3 provide the greatest yield of hydrogen (~ 90%) and stability for ~ 20 hours. Structured catalyst based on the metal Ni-Al platelet provides the yield of hydrogen 80-87% in oxy-steam and steam reforming of ethanol in the concentrated mixtures (ethanol concentration of 30%) in a pilot reactor for 40 hours. The results obtained make these structured catalytic systems very promising to use in electrochemical generators based on fuel cells with the use of inexpensive renewable resource – bio-oil
23
Burger, Thomas [Verfasser], Kai-Olaf Martin [Akademischer Betreuer] Hinrichsen, Luca [Gutachter] Lietti, Kai-Olaf Martin [Gutachter] Hinrichsen, and Hartmut [Gutachter] Spliethoff. "COx Methanation over Ni-Al-Based Catalysts: Development of CO2 Methanation Catalysts and Kinetic Modeling / Thomas Burger ; Gutachter: Luca Lietti, Kai-Olaf Martin Hinrichsen, Hartmut Spliethoff ; Betreuer: Kai-Olaf Martin Hinrichsen." München : Universitätsbibliothek der TU München, 2021. http://d-nb.info/1237815754/34.
Full text
24
Bednarczuk, Lukasz. "Ni-based catalysts for H2 production from ethanol steam reforming: Effect of the support and use of CO2 as regenerating agent and reactant." Doctoral thesis, Universitat de Barcelona, 2017. http://hdl.handle.net/10803/400828.
Full textAbstract:
In this work, the effect of CO2 on the hydrogen production under substoichiometric ethanol steam reforming (ESR) conditions over nickel based catalysts was studied. A special emphasis was focused on the application of carbon dioxide as a reactant under the CO2-assisted substoichiometric ethanol steam reforming. Moreover, CO2 was applied as regenerating agent to reduce the amount of carbonaceous deposits, which formation is a main drawback of the nickel catalysts. The obtained results were related with the physical-chemical properties of the catalysts.
A series of nickel catalysts supported on single metal oxides (MgO, Al2O3, Y2O3, La2O3 and ZrO2), and on binary (ZrO2-Y2O3, ZrO2-La2O3) and ternary systems (Y2O3-ZrO2-La2O3) was prepared. The supports of the catalysts were prepared by a pseudo sol-gel method using active carbon as templating agent.
The catalysts were characterized by ICP-AES for chemical analysis, physisorption of nitrogen (BET), powder X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and temperature-programmed reduction with H2 (H2-TPR). The surface density and strength of basic centres were determined from calorimetry of CO2 adsorption and temperature programmed desorption of CO2 (TPD-CO2) experiments.
A relationship between the surface area of Ni/ZrO2-Y2O3, Ni/ZrO2-La2O3 and Ni/ZrO2-Y2O3-La2O3 and the Zr content in the catalysts was found. Catalysts with higher Zr content showed higher values of surface area, independently of the components of the support.
The analysis of the reducibility of the catalysts showed that, for yttrium- and lanthanum-containing catalysts, the H2-consumption values largely exceeded those expected for NiO reduction to Ni0. This was related with the partial reduction of the supports due to the presence of superficial oxygen vacancies and/or with the presence of La2O2CO3.
Catalytic behaviour of all catalysts was studied under ESR conditions (ethanol/water = 1.0/1.6, molar ratio), at 600 ° C. The catalysts supported on single metal oxides were also tested under substoichiometric CO2-assisted ethanol steam reforming (CDESR) (ethanol/CO2/water = 1.0/1.6/1.6, molar ratios), at 600 ° C. In all cases, CO2 was also applied as a regenerating agent in order to remove carbon deposits.
The catalysts were active under the tested conditions; the main product was hydrogen (40-70% mol/mol). Carbon monoxide, methane, ethene, carbon dioxide and acetaldehyde were also obtained as a function of the catalyst and the reaction conditions used. Application of CO2-treatments to partially deactivated catalysts allowed to recover partially or totally the catalytic performance.
The spent catalysts were characterized in order to determine changes of the crystalline phases (powder XRD) and surface composition (XPS). The amount and the characteristics of the carbon deposits formed under the reaction conditions were determined using temperature programmed oxidation with mass spectrometer (TPO-MS) and Raman and diffuse reflectance infrared Fourier transform spectrometry analysis (DRIFTS).
For catalysts supported on single oxides, the effect of CO2 introduction as reactant is related with the basic characteristics of catalysts. After CDESR, Ni/La2O3 showed a lower amount and less ordered carbon deposits than after ESR. This was related with possible formation of La2O2CO3, which could participate in gasification of the carbon deposits.
Application of CO2-treatments during ESR resulted an effective way in the regeneration of Ni/La2O3, Ni/Y2O3, Ni/ZrO2-Y2O3, Ni/ZrO2-La2O3 and Ni/ZrO2-Y2O3-La2O3 catalysts. The partial removal of carbon deposits through the reverse Boudouard reaction is related with the surface density of rather strong basic sites of the catalysts. Ni/12Zr29Y13La exhibited the smallest carbon formation under substoichiometric ESR with intermediate CO2-treatments and the formed carbon deposits were poorly ordered. This catalyst was tested under long-time substoichiometric ESR test (280 h). Using periodic CO2-treatments for regeneration, a continuous operation of Ni/12Zr29Y13La under 100% ethanol conversion with a H2 yield of about 65% during a long-term ESR experiment was achieved.En este trabajo se han estudiado catalizadores de níquel soportado para la producción de hidrógeno a partir del reformado subestequiométrico de etanol con vapor. En el mismo se analiza el efecto de la introducción de CO2 como reactivo, realizando un reformado asistido con CO2 en condiciones subestequiometricas de agua/etanol. El objetivo principal del estudio fue relacionar el comportamiento catalítico de los catalizadores con las propiedades físico-químicas de los soportes usados. Además, se hizo énfasis en la aplicación del dióxido de carbono como agente regenerador de los catalizadores con el fin de reducir la presencia de depósitos carbonosos, que es el problema más común de los catalizadores de níquel. Atendiendo a los objetivos mencionados, se preparó y caracterizó una serie de catalizadores de níquel soportado sobre óxidos simples (MgO, Al2O3, Y2O3, La2O3 y ZrO2), y sobre sistemas binarios (ZrO2-Y2O3, ZrO2-La2O3) y ternarios (ZrO2-Y2O3-La2O3), con diversas composiciones. Para los catalizadores preparados se determinó las propiedades fisicoquímicas de superficie, como el área BET expuesta (fisisorción de N2), la densidad y fuerza de los centros básicos (TPD-CO2, calorimetría de adsorción de CO2) y la composición atómica (XPS). Se determinó las diferentes fases cristalinas presentes (XRD) y su reducibilidad (H2-TPR). El comportamiento catalítico de todos los catalizadores se estudió en condiciones de reformado subestequiométrico de etanol con vapor (etanol/agua = 1.0/1.6, ratio molar), a 600 °C. Adicionalmente, con los catalizadores soportados sobre óxidos simples se hicieron ensayos bajo condiciones de reformado subestequiométrico de etanol con vapor y asistido con CO2 (etanol/CO2/agua = 1.0/1.6/1.6, ratio molar). Todos los catalizadores preparados resultaron activos bajo las condiciones de reacción; el producto principal fue H2. Se obtuvo también CO, CH4, C2H4, CO2 y acetaldehído, en diferentes proporciones en función del catalizador y las condiciones de reacción. Los catalizadores usados fueron caracterizados mediante XRD, XPS, espectroscopias Raman e infrarroja y experimentos de oxidación a temperatura programada (TPO-MS), determinando la cantidad y las características de los depósitos carbonosos formados bajo las condiciones de reacción. El efecto en el comportamiento catalítico de la introducción de CO2 con reactivo se ha podido relacionar con las características básicas de los catalizadores. La aplicación de CO2 como agente de reactivación resultó efectiva en la disminución de la cantidad de depósitos carbonosos para los catalizadores Ni/La2O3, Ni/Y2O3, Ni/ZrO2-Y2O3, Ni/ZrO2-La2O3 y Ni/ZrO2-Y2O3-La2O3. El catalizador Ni/12Zr29Y13La mantuvo conversión completa de etanol, y rendimiento hacia H2 de alrededor de 65%, bajo condiciones de reformado subestequiométrico de etanol mediante la aplicación de tratamientos periódicos de regeneración con CO2.
25
Gumus, Rhoda Habor. "Synthesis gas production from biogas using Ni-based catalyst." Thesis, Loughborough University, 2005. https://dspace.lboro.ac.uk/2134/33769.
Full textAbstract:
As a result of global climate changes brought about by human activity, more sustainable sources of energy are being sought as alternatives to fossil fuels. Biomass is of particular interest as a sustainable source of energy since it does not contribute to net CO2 emissions. Reforming of methane derived from biomass with CO2 may form the basis of an efficient means to produce synthesis gas which has many applications m the petrochemical and allied industries. The objective of this study was the investigation of CO2 reforming of methane (simulating biogas) over effective supported nickel catalysts capable of long term operation without significant loss of activity and stability.
26
Lu, Fei. "Electrochemically Induced Urea to Ammonia on Ni Based Catalyst." Ohio University / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1502235953529178.
Full text
27
Sanja, Panić. "Fizičko-hemijske i katalitičke osobine ugljeničnih nanocevi sintetisanih metodom katalitičke hemijske depozicije iz gasne faze – korelacija sa osobinama primenjenih katalizatora na bazi prelaznih metala (Fe, Co, Ni)." Phd thesis, Univerzitet u Novom Sadu, Tehnološki fakultet Novi Sad, 2014. http://www.cris.uns.ac.rs/record.jsf?recordId=89673&source=NDLTD&language=en.
Full textAbstract:
Postojanje ugljeničnih nanocevi (UNC), kao jedne od brojnih alotropskih modifikacija ugljenika, zabeleženo je još pre više od pola veka. Međutim, do prave eksplozijeinteresovanja za ovu vrstu nanomaterijala je došlo tek 1991. godine kada ih je "ponovo" otkrio japanski naučnik S. Iijima. Od tada, zbog svojih izuzetnih fizičko-hemijskih osobina, UNC počinju da privlače pažnju naučne javnosti i spajaju istraživače iz različitih oblasti sa zajedničkim imeniteljem - nanotehnologija. Otkriće UNC je u znatnoj meri omogućilo razvoj visoke tehnologije u oblastima kao što su elektronika, optika, kompozitni materijali, kataliza, zaštita životne sredine, itd. Danas, primena nanocevi sve više doprinosi lakšoj implementaciji principa održivog razvoja u pomenute oblasti. Kataliza je polje od dvostrukog interesa, jer je jedan od načina dobijanja UNC upravo katalitički, a osim toga i same cevi su interesantne kao nosač novog katalizatora.Istraživanje čiji su rezultati prikazani u okviru ove doktorske disertacije je obuhvatilo više oblasti proučavanja UNC, počevši od razvoja metode za njihovu sintezu, preko prečišćavanja i funkcionalizacije finalnog proizvoda, pa do primene nanocevi u dva procesa od značaja za oblast zaštite životne sredine.Razvoj katalitičke metode sinteze UNC započet je primenom vertikalnog cevnog kvarcnog reaktora, iz CO i CH4 kao izvora ugljenika, pri čemu su u reakciji testiranimonometalni katalizatori na bazi Fe, Co i Ni na Al2O3 kao nosaču (I serija katalizatora). Rezultati ovih preliminarnih eksperimenata su pokazali malu aktivnost I serije monometalnih katalizatora, što se može pripisati, kako neadekvatnoj hidrodinamici reaktora i loše odabranim reakcionim parametrima, tako i neodgovarajućoj veličini katalitičkih čestica i načina njihovog pakovanja u vertikalnomreaktoru. Shodno tome, u cilju postizanja boljeg prinosa nanocevi, dalji eksperimenti sinteze izvedeni su u horizontalnom reaktoru u struji C2H4 i u prisustvu II serijemonometalnih katalizatora sa Al2O3 i SiO2 kao nosačima, koji se u odnosu na I seriju razlikuju po udelu aktivne faze i veličini čestica katalizatora (praškast oblik). Katalizatori II serije su pokazali zadovoljavajuću aktivnost u reakciji sinteze UNC, a rezultati karakterizacije dobijenih uzoraka nanocevi ukazuju na različit uticaj nosača katalizatora na morfologiju sintetisanih nanocevi. Shodno ostvarenom prinosu ugljenika, a u cilju optimizacije reakcionih parametara, katalizator na bazi Fe sa SiO2 kao nosačem je odabran kao reprezentativan za ispitivanje uticaja vremena trajanja sinteze UNC, kao i zapreminskog udela C2H4 u smeši sa azotom, na prinosnanocevi i selektivnost procesa. Optimizacija reakcionih uslova je u daljoj fazi rada dovela do uvođenja bimetalnih katalizatora sa istim tradicionalnim nosačima – Al2O3 i SiO2. Najveći prinos ugljenika ostvaren je na katalizatorima sa Fe i Co kao aktivnom fazom, bez obzira na vrstu nosača. UNC sintetisane na pomenutim katalizatorima su karakterisane u ciljuispitivanja uticaja primenjenih nosača na njihove fizičkohemijske osobine, pa je shodno tome i predložen vršni mehanizam njihovog rasta. Rezultati ispitivanja kvaliteta sintetisanih UNC su ukazali da primena SiO2, kao nosača katalizatora, za razliku od Al2O3, favorizuje rast UNC boljeg površinskog i ukupnog kvaliteta. S obzirom na raznolikost mogućnosti primene UNC, istraživanja u tom smeru zahtevaju čiste UNC, pa su shodno tome proizvodi sinteze prečišćeni metodom tečne oksidacije. Rezultati fizičko-hemijske karakterizacije prečišćenih UNC su ukazali na efikasnost primenjene metode sa aspekta uklanjanja prisutnog katalizatora, ali i na njen različit uticaj na strukturu, odnosno kvalitet prečišćenih uzoraka. Kao posledica promena unutar strukture UNC, kao i različitog stepena njihove funkcionalizacije, ukupni kvalitet prečišćenih nanocevi je, u zavisnosti od primenjenog nosača katalizatora, promenjen u odnosu na odgovarajuće neprečišćene uzorke.Poslednjih godina se posebna pažnja poklanja nanomaterijalima koji se mogu primeniti za uklanjanje različitih polutanata iz životne sredine, kako u funkciji adsorbenata, tako i u funkciji katalizatora. U okviru ove doktorske disertacije obuhvaćena je primena UNC kao adsorbenta za uklanjanje insekticida tiametoksama iz vode, kao i njihova primena kao nosača katalizatora u reakcijidenitracije vode. Rezultati eksperimenata adsorpcije su pokazali da UNC, prethodno tretirane u ccHNO3, predstavljaju dobar adsorbent za uklanjanje insekticida tiametoksama iz vodenog rastvora. Odabir procesnih parametara za proučavanje kinetike adsorpcije, adsorpcione ravnoteže, kao i termodinamike procesa izvršen je primenom frakcionog faktorskog dizajna na dva nivoa, 5 1 V 2 , a dobijeni rezultati su ukazali da je pomenuti proces adsorpcije spontan i kontrolisan uglavnom unutrašnjom difuzijom molekula insekticida u mezopore uzorka UNC. Performanse katalizatora sa UNC kao nosačem su testirane u reakciji katalitičke denitracije, pri čemu su dobijeni rezultati pokazali da se novoformirani katalizator karakteriše zadovoljavajućom disperznošću sa udelombimetalnih Pd-Cu nanočestica koje omogućavaju 60% konverzije nitratnog jona.The existance of carbon nanotubes (CNTs), as one of the carbon allotropes, was noted over half century ago. However, the true interest for these nanomaterials appeared at 1991, when they were "redescovered" by Japanese scientist S. Iijima. Since then, due to their unique physico-chemical properties, CNTs begin to attract attention of the scientific community and to gather researchers from different areas within the common field of interest – nanotechnology. The CNTs discovery substantially enabled the high technology development in the fields such as electronics, optics, composite materials, catalysis, environmental protection, etc. Nowdays, the application of nanotubes is increasingly contributing to easier implementation of sustainable development principles in the above mentioned areas. Catalysis is the field of double interest – one of the CNTs synthesis method is catalytical, and the nanotubes can also be used as the support of the new catalyst.The research, which results are shown within this PhD Thesis, includes few different CNTs research fields, starting from the synthesis method development, over the purification and functionalization of the final product, to the application ofnanotubes in two processes of significance for the field of environmental protection.The development of the CNTs catalytic synthesis method was started by the use of vertical quartz tube reactor, in the flow of CO and CH4 as the carbon source, and in the presence of monometallic catalysts based on Fe, Co and Ni at Al2O3 as the support (the first series of catalysts). The results of these preliminary experiments have shown the low activity of these monometallic catalysts, which can be attributed to the inadequate reactor hydrodynamics and selected reaction parameters, as well as the inadequate size of the catalytic particles and the type of their packing in the vertical reactor. Consequently, in order to achieve the higher nanotubes yield, further synthesis experiments were carried out in a horizontal reactor in the flow of C2H4 as the carbon source, and in the presence of the second series of monometallic catalysts with Al2O3 and SiO2 as the supports. The catalysts of the second series have shown satisfactory activity in the CNTs synthesis reaction, and the results of the obtained samples characterization idicate a different influence of the catalyst support on the synthesized CNTs morphology. In order to optimize the reaction parameters, Fe/SiO2 catalyst was chosen as a representative to examine the effect of the CNTs synthesis duration, as well as the volume percentage of C2H4 in the mixture with nitrogen to the CNTs yield and process selectivity. In a further phase of work, the optimization of thereaction parameters led to the introduction of the bimetallic catalysts with the same traditional supports, Al2O3 and SiO2. The highest carbon yield was achieved over Fe, Co based catalysts, regardless of the type of the catalyst support. CNTs synthesized over the above mentioned catalysts were characterized in order to study the effect of the used supports on their physico-chemical properties, and consequently the CNTs tip growth mechanism was proposed. The results of quality examination of the synthesized CNTs showed that the use of SiO2, as a catalyst support, unlike Al2O3, favors the growth of nanotubes of better surface and overall crystalline quality. In view of the diversity of possible CNTs applications, investigation in that direction requires purified CNTs and accordingly the final CNTs products were purified by liquid oxidation method. The results of physico-chemical characterization of the purified CNTs showed that the applied purification method was effective in terms of removing the present catalyst, but on the other hand it had different influence on the structure and quality of the purified samples. As a consequence of CNTs structural changes, as well as their different degree of functionalization, the overall crystalline quality of the purified nanotubes, originating from different catalyst supports, was changed in comparison to the corresponding unpurified samples. Over the past few years, special attention was focused onnanomaterials that can be applied as adsorbents or catalysts for the removal of various pollutants from the environment. This PhD Thesis considers the use of CNTs, as adsorbent, for the removal of insecticide thiamethoxam from water, as well as their use as catalyst support for water denitration reaction. The results of adsorption experiments have shown that the CNTs, pretreated in ccHNO3, represent a good adsorbent for the removal of thiamethoxam from the aqueous solutions. Theselection of the process parameters in order to study the adsorption kinetics and equilibrium, as well as the thermodynamics of the process, was conducted using thefractional factorial design at two levels, 5 1 V 2 . The obtained results showed that the adsorption process is spontaneous and controlled mainly by an internal diffusion of molecules of insecticide in the mesopores of CNTs. The performance of the catalyst with the CNTs as the support were tested in catalytic water denitration reaction, whereby the results showed that the newly formed catalyst is characterized by satisfactory dispersion of Pd-Cu bimetallic nanoparticles which enable the 60% conversion of nitrate ions.
28
Liu, Xiu. "Production d'hydrogène par reformage à sec de méthane sur catalyseurs au Ni à base de CeO2, CeO2 modifiée avec Zr ou Al, et nano-matériaux Mg-Al-O." Electronic Thesis or Diss., Centrale Lille Institut, 2021. http://www.theses.fr/2021CLIL0032.
Full textAbstract:
La demande en hydrogène, en tant que produit chimique et énergie, augmente, mais les principales méthodes de production d'hydrogène ne sont ni durables ni respectueuses de l'environnement. La production d'hydrogène à partir de ressources renouvelables (comme le biogaz composé principalement de CH4 et de CO2) est requise. Le reformage à sec du méthane (DRM) est une méthode prometteuse pour produire H2 et CO à partir des gaz. Dans cette thèse, des catalyseurs à base de Ni, CeNiXOY, CeZr0.5NiXOY, CeAl0.5NiXOY, et AlMg2NiXOY sont étudiés pour la réaction de reformage à sec du méthane. L'effet de la température de réaction, de la teneur en Ni, du prétraitement in situ sous H2, de la masse de catalyseur, de la calcination et du rapport CO2/CH4 sont analysés. Sur certains composés choisis, des tests de stabilité à long terme sont aussi reportés. L’optimisation des performances catalytiques avec une formation réduite de carbone, sont obtenues sur des catalyseurs partiellement réduits. Diverses méthodes de caractérisation sont utilisées pour analyser les propriétés physico-chimiques des catalyseurs, telles que XRD, Raman, XPS et TPR. Certains catalyseurs sont également caractérisés après la réaction catalytique (DRM) pour analyser leur évolution. Enfin, un site actif impliquant des espèces Ni en interactions fortes avec d'autres cations est proposé. Ce site est obtenu sur un catalyseur partiellement réduit impliquant des lacunes anioniques, des espèces O2- et des cationsThe demand for hydrogen, as a chemical product and as energy is increasing, but the main hydrogen production methods are unsustainable and not environmentally friendly. Hydrogen production from renewable resources (such as biogas mainly composed of CH4 and CO2) is required. Dry reforming of methane (DRM) is a promising method to produce H2 and CO from greenhouse gases. In this thesis, Ni-based CeNiXOY, CeZr0.5NiXOY, CeAl0.5NiXOY, and AlMg2NiXOY catalysts are studied in dry reforming of methane reaction. The effect of reaction temperature, Ni content, in situ H2 pretreatment, mass of catalyst, calcination, and CO2/CH4 ratio are studied. Moreover, long duration stability tests are reported on some chosen samples. The optimized catalytic performance associated with resistance to carbon formation is obtained on partially reduced catalysts. Various physicochemical characterizations are used to analyze the properties of the catalysts, such as XRD, Raman, XPS, and H2-TPR. Some chosen catalysts are also characterized after DRM reaction to analyze their evolution. Finally, an active site involving Ni species in close interactions with other cations is proposed. It is related to a partially reduced catalyst involving anionic vacancies, O2- species, and cations
29
Coe, Neil J. "A study of Ni based fuel reforming anodes for solid oxide fuel cells." Thesis, Keele University, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.343244.
Full textAbstract:
The anode material in a conventional design of solid oxide fuel cell (SOFC) operating above 1123 K is typically made from NiO/Zirconia. NiO/Zirconia anodes are known to perform well in hydrogen but exhibit difficulties when natural gas is used as a fuel. Natural gas is much cheaper than hydrogen and widely available but causes carbon deposition and deactivation of the NiO/Zirconia SOFC anode. One objective of this work was to prepare and characterize NiO/Zirconia anodes both as powders and as applied to extruded zirconia tubes. The problem of carbon deposition when NiO/Zirconia anodes operate in methane, the main component of natural gas, was investigated. Another aim was to address the problem of coking with an effort to moderate carbon deposition by using additives to the NiO/Zirconia anode. Temperature programmed reduction (TPR) was used to study the reaction characteristicso f NiO/Zirconia anodes.T he carbon depositedo n thesea nodesa fter methane decomposition and reforming was characterized using temperature programmed oxidation (TPO). The anodes were placed in a reactor (stainless-steel, alumina or zirconia) tube in a test assembly developed for an extruded tubular SOFC. The reactor inlet was connected to a flexible gas handling system and the exhaust to a continuously sampling mass spectrometer. This system also allowed simultaneous study of electrical and catalytic measurementsThe various conditions for methane reforming have been shown to influence the character of carbon deposited and the quantity deposited. Conditions such as anode calcination temperature, anode reduction regime, reforming temperature and reforming time have all been shown to influence the reactions occuring on the anode including carbon deposition, subsequently characterized by TPO. NiO/Zirconia powders have also been shown to behave differently from NiO/Zirconia anodes adhered to zirconia tubes. An alkali metal additive has been shown to moderate carbon deposition and improve cell performance. Small additions of Li, typically 1 mol %, to the Ni/Zirconia anode cause a decrease in carbon deposition after reforming at temperatures of 1123 K and 1173 K. The activation energy of surface carbon removed by oxygen is lowered by approximately 50 kJ mot' for the 1 mol % Li doped Ni/Zirconia anode compared to the undoped powder. Anodes doped with Li displayed greater cell performances. The improvements seen with these additives show that their use could offer a viable alternative to conventional anodes in current SOFC systems. Tubular solid oxide fuel cells have been tested in a custom built rig whereby electronic and catalytic measurements can be sampled simultaneously. This was used to monitor the influence of drawing current on the reactions occurring on the anode. The presence of alkali Li on the doped Ni anode surface has been shown to interfere with surface reactions under electrochemical load/steam reforming
30
Junges, Fernando. "Novel catalyst systems based on Ni(II), Ti(IV), and Cr(III) complexes for oligo-and polymerization of ethylene." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2005. http://hdl.handle.net/10183/6358.
Full textAbstract:
Le complexe de Brookhart Ni(α-diimine)Cl2 (1) (α-diimine = 1,4-bis(2,6- diisopropylphenyl)-acenaphthenediimine) a été caractérisé après impregnation sur silice (S1) et a silices modifié avec MAO (4,0, 8,0 et 23,0 wt.% Al/SiO2 appelé S2, S3 et S4, respectivement). Le traitement de ces composés greffé avec MAO produit des catalyseurs actifs pour la polymérisation de l'éthylène. Un haute activité catalytique a été obtenue en utilisant le système supporté 1/S3 (196 kg de PE/mol[Ni].h.atm; toluene, Al/Ni = 1000, 30ºC, 60 min et pression atmosphérique d'éthylène). Les effets des conditions de la polymérisation ont été testés avec le catalyseur greffé S2 et la meilleure activité catalytique a été obtenue avec le solvant hexane, MAO comme cocatalyseur, la proportion molaire Al/Ni de 1000 et à la température de 30°C (285 kg de PE/mol[Ni].h.atm). Quand la réaction a été conduite selon la méthodologie in situ, l'activité a pratiquement doublé et les polymères ont montré des propriétés semblables. Les polymères produits par les catalyseurs supportés ont montré l'absence de température de fusion, resultats senblables à seux obtenus avec les systèms homogène par analyse DSC. En revanche, le polymères obtenus avec les système greffé presentent selon les courbes GPC une (MwD) polydispersité qui varie de 1,7 à 7,0. Un mélange de polyéthylène lineaire et ramifié (BPE/LPE) préparé utilisant les complexes Ni(α-diimine)Cl2 (1) (α-diimine = 1,4-bis(2,6-diisopropylphenyl)- acenaphthenediimine) et {TpMs*}TiCl3 (2) (TpMs* = hydridobis(3-mesitylpyrazol-1-yl)(5- mesitylpyrazol-1-yl)) greffés in situ sur silice modifiée avec MAO (4,0 wt. -% Al/SiO2, S2). Les réactions de polymérisation ont été exécutées dans le toluène à deux températures différentes (0 et 30°C), variant la fraction molaires du nickel (xNi), et utilisan MAO comme cocatalyseur externe. A toutes les températures, les activités montrent une tendence de variation linéaire avec xNi et indiquent l´absence d´effet synerque entre les espéces de nickel et du titane. Des activités les plus elèvees ont été trouvées à 0°C. Les températures de fusion pour les mélanges de polyéthylène produits à 0 °C diminuent alors que xNi augmente l'indiquant une bonne compatibilité entre les phases du polyéthylène obtenues avec les deux catalyseurs. La température de fusion des mélanges de polyéthylène dépendre de l'ordre selon lequel les catalyseurs ont été greffés sur la silice modifiée avec MAO. L'immobilisation initiale de 1 sur le support (2/1/S2) produit des polymères avec une temperature de fusion (Tm) inférieure à celle des polymère obtenus lorsque le titane a etè greffé inicialment 1/2/S2. L´observation des polyèthylènes obtenus avec les deux systèms (2/1/S2 et 1/2/S2) par microscopie electronique à balayage (SEM) a montré la formation de polymére sphérique montrant que la morphologie sphérique du support à été reproduite. Sont décrits la synthèse, la caractérisation et les propriètès catalytique pour l'oligomerization de l'éthylène de quatre composés organometalliques du CrIII possèdante les ligands (([bis[2-(3,5-dimethyl-1-pyrazolyl)ethyl]amine]chromiun(III)chloride (3a), [bis[2- (3,5-dimethyl-l-pyrazolyl)ethyl] benzylamine]chromiun(III)chloride (3b), [bis[2-(3,5- dimethyl-l-pyrazolyl)ethyl]ether] chromiun(III)chloride (3c), [bis[2-(3-phenyl-lpyrazolyl) ethyl]ether]chromiun(III)chloride (3d)). Concernent l'oligomerization, exception faite du composè 3a, tous les complexe du chrome se sont montré actif après activation avec MAO et les FR obtenues ont une effet differencie à celles atteintes avec CrCl3(thf)3. La coordination d´un ligand tridentatè sur le centre metallique ne provoque pas de changements considérables sur la formation des C4 et C6, mais la montantè de C8 est diminuèe et celles des C10 et +C12 ont ètè augmentèes. Les polymères produits par le catalyseur 3a à 3 et 20 atm d'éthylène possèdent, selon les analyses par DSC la températures de fusion de 133,8 et 136ºC respectivement. Ceci indique que dans les deux cas la production de polyèthylène de haut densité. Effectivement le masse molar moyenne, obtenus par GPC, est de 46647 g/mol avec Mw/Mn = 2,4 (3 atm). Le système 3c/MAO a montré des valeurs de FR, activité et sélectivité à α-olefins differents selon la pression d´éthylène utilisèe. Se qui montré une grand sensibilitè à la concentration d´éthylène solubilisè.The complex of Brookhart Ni(α-diimine)Cl2 (1) (α-diimine = 1,4-bis(2,6- diisopropylphenyl)-acenaphthenediimine) has been characterized after impregnation on silica (S1) and MAO-modified silicas (4.0, 8.0 and 23.0 wts.% Al/SiO2 called S2, S3 and S4, respectively). The treatment of these heterogeneous systems with MAO produces some active catalysts for the polymerization of the ethylene. A high catalytic activity has been gotten while using the system supported 1/S3 (196 kg of PE/mol[Ni].h.atm; toluene, Al/Ni = 1000, 30ºC, 60 min and atmospheric pressure of ethylene). The effects of polymerization conditions have been tested with the catalyst supported in S2 and the best catalytic activity has been gotten with solvent hexane, MAO as cocatalyst, molar ratio Al/Ni of 1000 and to the temperature of 30°C (285 kg of PE/mol[Ni].h.atm). When the reaction has been driven according to the in situ methodology, the activity practically doubled and polymers showed some similar properties. Polymers products by the supported catalysts showed the absence of melting fusion, results similar to those gotten with the homogeneous systems by DSC analysis. But then, polymers gotten with the transplanted system present according to the GPC’s curves the polydispersity (MwD) varies between 1.7 and 7.0. A polyethylene blend (BPE/LPE) was prepared using the complex Ni(α-diimine)Cl2 (1) (α-diimine = 1,4-bis(2,6-diisopropylphenyl)-acenaphthenediimine) and {TpMs*}TiCl3 (2) (TpMs* = hydridobis(3-mesitylpyrazol-1-yl)(5-mesitylpyrazol-1-yl)) supported in situ on MAO-modified silica (4.0 wts. -% Al/SiO2, S2). Reactions of polymerization of ethylene have been executed in the toluene in two different temperatures (0 and 30°C), varying the molars fraction of nickel (xNi), and using MAO as external cocatalyst. To all temperatures, the activities show a linear variation tendency with xNi and indicate the absence of the effect synergic between the species of nickel and the titanium. The maximum of activity have been found at 0°C. The melting temperature for the blends of polyethylene produced at 0 °C decrease whereas xNi increases indicating a good compatibility between phases of the polyethylene gotten with the two catalysts. The melting temperature for the blends of polyethylene showed be depend on the order according to which catalysts have been supported on the MAO-modified silica. The initial immobilization of 1 on the support (2/1/S2) product of polymers with a melting temperature (Tm) lower to the one of the polymer gotten when the titanium has been supported inicially (1/2/S2). The observation of polyethylenes gotten with the two systems (2/1/S2 and 1/2/S2) by scanning electron microscopy (SEM) showed the spherical polymer formation showing that the spherical morphology of the support to been reproduced. Are described the synthesis, the characterization and the catalytic properties for the oligomerization of the ethylene of four organometallics compounds of CrIII with ligands ([bis[2-(3,5-dimethyl-1-pyrazolyl)ethyl]amine] chromium (III) chloride (3a), [bis[2-(3,5- dimethyl-l-pyrazolyl)ethyl]benzylamine] chromium (III) chloride (3b), [bis[2-(3,5-dimethyl-lpyrazolyl) ethyl]ether] chromiun(III)chloride (3c), [bis[2-(3-phenyl-lpyrazolyl) ethyl]ether]chromiun(III)chloride (3d)). In relation of the oligomerization, at exception made of the compounds 3a, all complex of the chromium showed be active after activation with MAO and the TOF gotten have one effect differentiated to those formed with CrCl3(thf)3. The coordination of a tridentate ligand on the metallic center doesn't provoke any considerable changes on the formation of the C4 and C6, but the amount of C8 are decrease and the C10 and C12+ have increased. The Polymers produced by the catalyst 3a to 3 and 20 bar of ethylene have, according to analyses by DSC, the temperatures of fusion of 133,8 and 136ºC respectively. It indicates that in the two cases the production of high density polyethylene. The molar mass, gotten by GPC, is 46647 g/mols with MwD = 2,4 (3 bar). The system 3c/MAO showed values of TOF, activity and selectivity to different α-olefins according to the pressure of ethylene uses. Himself that shown a big sensibility to the concentration of ethylene solubilized.
31
Bidurukontham, Aditya V. "Development of Porous Nickel Electro-Catalysts for Photo-Water Splitting Using Zn, Co, Mn and NH4+ Based Precursors." University of Toledo / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1310131764.
Full text
32
Sperger, Theresa [Verfasser], Franziska [Akademischer Betreuer] Schönebeck, and Dieter [Akademischer Betreuer] Enders. "Combined experimental and computational studies of ligand-based selectivities in Pd- and Ni-catalysis / Theresa Sperger ; Franziska Schoenebeck, Dieter Enders." Aachen : Universitätsbibliothek der RWTH Aachen, 2018. http://d-nb.info/1194184332/34.
Full text
33
Clark, Joshua Patrick. "A multinuclear solid state nuclear magnetic resonance investigation of the preparation of Co, Pt and Ni based hydrogenation catalyst systems." Thesis, University of Warwick, 2017. http://wrap.warwick.ac.uk/106443/.
Full textAbstract:
It was known highly dispersed Co (HDC) catalysts for Fischer-Tropsch applications could be synthesised from either Co metal or CoCO3 precursors. Both synthesis routes were known to precipitate Co oxide nanoparticles from solution onto a support via Co(III) ammine complexes. The synthesis pathway was not known. Using solid state NMR and single crystal X-ray diffraction (XRD) a suite of Co(III) complexes have been characterised. The HDC catalyst synthesis from Co metal produced the Co(III) complex which was identified as [(Co(NH3)3)2(μ-OH)2(μ-CO3)](CO3)∙5H2O via single crystal XRD. The 59 Co solid state NMR then confirmed the precipitant from the CoCO3 route was the same complex. The characterisation of a suite of Co(III) complexes of differing oxo coordination has been obtained. It was observed that each oxo coordinating ligand increased the NMR chemical shift by ~800 ppm. For a single oxo coordination a disparity of ~1000 ppm was also observed due to effects from the anion, crystallographic water and type of oxo coordination. Spin-spin coupling with the 59 Co nucleus was observed to occur for bidentate carbonate and ammine ligands yielded ǀ2 J( 59 Co, 13 C)ǀ of 1-10 Hz and ǀ1 J( 59 Co, 15 N)ǀ of 56-75 Hz. The bonding of monodentate and bridging carbonate ligands was observed to be ionic in nature lacking the spin-spin coupling. It was hypothesised Co oxide nanoparticles precipitated from Werner’s complex, [Co((μ-OH)2Co(NH3)4)3](SO4)3∙9H2O. This was observed in the solid state NMR studies at 14518 ppm. From the time resolved 59 Co solution state NMR measurements of the HDC catalyst syntheses a resonance was observed at 14300 ppm. This was assigned to the central Co oxo coordinated environment of Werner’s complex. In conjunction with observations of chemical shifts coinciding with known precursors to Werner’s complex, it has been possible to suggest a reaction pathway. It was concluded that [Co(NH3)5CO3]+ and [Co(NH3)4CO3]+ eventually become Werner’s complex before precipitating out of solution as Co oxide nanoparticles. The study of Pt and Ni hydrogenation catalyst precursors on α-alumina, γ-alumina, silica and titania have been undertaken. From the Pt materials, it was observed oligomeric Pt oxide structures deposited on the supports. The 195 Pt NMR measurements of these oligomeric structures showed disorder due to a mix of hydroxyl and O bridges in addition to preferential orientations. These orientations were thought to arise from the formation of sheet like structures. All measurements were compared to PtO2, the 195 Pt measurement of which produced an axial symmetric lineshape due to chemical shift anisotropy yielding a Ω of 3916(100) ppm, κ of -1.00(8) and a δiso of 4607(100) ppm. Finally, 27 Al measurements of the γ-alumina support showed reactions with nitric acid occurred. This formed an aluminium nitrate species on the surface which was removed with heat treatment. It was also concluded AlO(V) sites were preferential binding points for the Pt oxide. The AlO(V) 27 Al NMR resonance was seen to disappear with heat treatment, it has been proposed AlO(V) converts to AlO(VI) with the addition of Al–O– Pt bonds.
34
H, Moud Pouya. "Catalytic Conversion of Undesired Organic Compounds to Syngas in Biomass Gasification and Pyrolysis Applications." Doctoral thesis, KTH, Kemiteknik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-213368.
Full textAbstract:
Reliable energy supply is a major concern and crucial for development of the global society. To address the dependency on fossil fuel and the negative effects of this reliance on climate, there is a need for a transition to cleaner sources. An attractive solution for replacing fossil-based products is renewable substitutes produced from biomass. Gasification and pyrolysis are two promising thermochemical conversion technologies, facing challenges before large-scale commercialization becomes viable. In case of biomass gasification, tar is often and undesired by-product. An attractive option to convert tar into syngas is nickel-based catalytic steam reforming (SR). For biomass pyrolysis, catalytic SR is in early stages of investigation as a feasible option for bio-crude conversion to syngas. The focus of the thesis is partly dedicated to describe research aimed at increasing the knowledge around tar reforming mechanisms and effect of biomass-derived impurities on Ni-based tar reforming catalyst downstream of gasifiers. The work focuses on better understanding of gas-phase alkali interaction with Ni-based catalyst surface under realistic conditions. A methodology was successfully developed to enable controlled investigation of the combined sulfur (S) and potassium (K) interaction with the catalyst. The most striking result was that K appears to lower the sulfur coverage and increases methane and tar reforming activity. Additionally, the results obtained in the atomistic investigations are discussed in terms of naphthalene adsorption, dehydrogenation and carbon passivation of nickel. Furthermore, the thesis describes research performed on pyrolysis gas pre-conditioning at a small-industrial scale, using an iron-based catalyst. Findings showed that Fe-based materials are potential candidates for application in a pyrolysis gas pre-conditioning step before further treatment or use, and a way for generating a hydrogen-enriched gas without the need for bio-crude condensation.Tillförlitlig energiförsörjning är en stor utmaning och avgörande för utvecklingen av det globala samhället. För att ta möta beroendet av fossil råvara och de negativa effekter som detta beroende medför för klimatet finns ett stort behov av en övergång till renare energiråvaror. En attraktiv lösning är att ersätta nuvarande fossil råvara med produkter från biomassa. Förgasning och pyrolys är två lovande teknologier för termokemisk omvandling av biomassa. Kommersialisering av dessa teknologier är inte helt problemfritt. I fallet förgasning så behöver, bl.a. oönskade tyngre kolväten (tjära) hanteras innan den producerade orenade produktgasen kan användas i syntesgastillämpningar. Ett effektivt alternativ för detta är gaskonditionering vid höga temperaturer, baserade på katalytisk ångreformering med en nickelkatalysator. Katalytisk ångreformering är en möjlig teknik för omvandling av bioråvara, producerad från pyrolys av biomassa, till syntesgas. Avhandlingen fokuserar delvis på att beskriva den forskning som utförts för att öka kunskapen kring mekanismer för tjärreformering och effekterna av föroreningar från biomassan på en nickelkatalysator nedströms förgasare. Arbetet bidrar till en bättre förståelse av hur alkali i form av kalium (K) i gasfasen upptas, jämviktas och växelverkar med ytan hos nickelkatalysatorn under fullt realistiska förhållanden. Inledningsvis utvecklades en metod för att möjliggöra kontrollerade studier av den kombinerade effekten av S och K, vilken inkluderar exakt dosering av alkali till en produktgas, eliminering av transienter i katalysatoraktiviteten samt katalysatorkarakterisering. Det mest lovande resultatet är att K både sänker ytans svavelinnehåll och ökar aktiviteten för omvandlingen av metan och tjära. För att ytterligare fördjupa kunskaperna i mekanismerna för tjärnedbrytning utfördes experimentella och teoretiska ytstudier på en enkristallnickelyta med naftalen som modellförening. Resultat avseende naftalenadsorption, dehydrogenering av naftalen och kolpassivering av nickelytan diskuteras. Därutöver så beskriver avhandlingen den forskning som utförts inom förkonditionering av pyrolysgas med en järnkatalysator för varsam deoxygenering av biooljan och vätgasproduktion. Detta utfördes vid en småskalig industriell anläggning. De experimentella studierna visar att den undersökta järnkatalysatorn resulterar i en vätgasberikad gas och att den är en potentiell kandidat för tillämpning i ett förkonditioneringssteg.
QC 20170830
35
Melo, Jarbas Almeida de. "Catalisadores a base de Cu, Ni e Mg suportados em Al2O3 aplicados à gaseificação de etanol em meio contendo água em condições supercríticas." Universidade Federal de Goiás, 2018. http://repositorio.bc.ufg.br/tede/handle/tede/8981.
Full textAbstract:
Submitted by Liliane Ferreira (ljuvencia30@gmail.com) on 2018-10-15T15:41:01Z
No. of bitstreams: 2
Dissertação - Jarbas Almeida de Melo - 2018.pdf: 7287109 bytes, checksum: 8e33ba1a3ef2d679e03ecdb4e368b53c (MD5)
license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5)Approved for entry into archive by Luciana Ferreira (lucgeral@gmail.com) on 2018-10-16T10:13:44Z (GMT) No. of bitstreams: 2 Dissertação - Jarbas Almeida de Melo - 2018.pdf: 7287109 bytes, checksum: 8e33ba1a3ef2d679e03ecdb4e368b53c (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5)
Made available in DSpace on 2018-10-16T10:13:44Z (GMT). No. of bitstreams: 2 Dissertação - Jarbas Almeida de Melo - 2018.pdf: 7287109 bytes, checksum: 8e33ba1a3ef2d679e03ecdb4e368b53c (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Previous issue date: 2018-09-28
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES
In this work the synthesis of catalysts was carried out with the objective of H2 production from gasification of ethanol in medium containing water under supercritical conditions. Based on reports from the literature, Cu, Ni and Mg were selected as components for the active phase, alumina (Al2O3) as catalysts support. The catalysts were prepared from aqueous solutions of nitrate salts precursors of Cu, Ni and Mg. The catalysts were characterized by X-ray fluorescence (FRX), scanning electron microscopy, thermogravimetric and thermal differential analysis (TG/ATD), X-ray diffraction (DRX) and textural analysis by N2 adsorption / desorption isotherms at -196 ° C. The TG/ATD analysis indicated that the calcination of the catalytic precursors was sufficient for the removal of water and decomposition of the nitrates of the metal salts precursors of the active phase. In the FRX analysis, the increase in the concentration of the metals in relation to the nominal values after the synthesis of the catalysts was characterized, with an increase of 20 to 40% depending on the metal due to the loss of water from the alumina support. The FRX analysis of the catalysts used in the catalytic tests shows that there was no significant leaching during the gasification process. DRX analysis have characteristic results that the metals are in amorphous form or dispersed in the form of small crystallites. Textural analysis of N2 adsorption / desorption isotherms indicated a reduction of approximately 60% in the specific surface area between the alumina and the calcined alumina and the specific area values between the alumina and the metal catalysts were kept close. The catalytic tests were performed at a pressure of 25 MPa and at temperatures of 400 to 650 ° C. A 10/1 molar water / ethanol solution was fed. In the catalytic tests H2, CH4, CO, CO2, C2H4, C2H6, C2H4O were obtained. The highest ethanol conversions were obtained at the temperature of 650 ° C for the catalysts NiO/Al2O3 and NiO-MgO/Al2O3, both 81%. The highest yield was 0.41 mol H2 / mol ethanol fed to the NiO / Al2O3 catalyst, at a temperature of 600 ° C. The highest selectivity at the temperature of 600 ° C was 39%, obtained by the NiO/Al2O3 catalyst.
Neste trabalho foi realizada a síntese de catalisadores com o objetivo da produção de H2 a partir da gaseificação de etanol em meio contendo água em condições supercríticas. A partir de relatos da literatura, foram selecionados Cu, Ni e Mg como componentes para a fase ativa e a alumina (Al2O3) como suporte dos catalisadores. Os catalisadores foram preparados a partir de soluções aquosas de sais de nitrato precursores de Cu, Ni e Mg. Os catalisadores foram caracterizados por fluorescência de raios X (FRX), microscopia eletrônica de varredura (MEV), análises termogravimétrica e térmica diferencial simultânea (TG/ATD), difração de raios X (DRX) e análise textural por isotermas de adsorção/dessorção de N2 a -196°C. As análises de TG/ATD indicaram que a calcinação dos precursores catalíticos foi suficiente para a remoção da água e decomposição dos nitratos dos sais metálicos precursores da fase ativa. Nas análises de FRX ficou caracterizado o aumento da concentração dos metais em relação aos valores nominais, após a síntese dos catalisadores, com acréscimo de 20 a 40 % dependendo do metal, devido à perda de água do suporte de alumina. As análises FRX dos catalisadores utiilzados nos testes catalíticos mostraram que não houve lixiviação considerável durante o processo de gaseificação. Análises de DRX apresentaram resultados característicos de que os metais se encontram na forma amorfa ou dispersos na forma de pequenos cristalitos. Os resultados foram coerentes com as imagens de microscopia eletrônica de varredura. Análises textural por isotermas de adsorção/dessorção de N2 indicaram uma redução de aproximadamente 60% na área superficial específica entre a alumina e a alumina calcinada e mantiveram-se próximos os valores de área específica entre a alumina e os catalisadores metálicos. Os testes catalíticos foram realizados a uma pressão de 25 MPa e nas temperaturas de 400 a 650 °C. Foi alimentada uma solução de água/etanol na razão de 10/1 molar. Nos testes catalíticos foram obtidos H2, CH4, CO, CO2, C2H4, C2H6, C2H4O. As maiores conversões de etanol foram obtidas na temperatura de 650 °C para os catalisadores de NiO/Al2O3 e NiO-MgO/Al2O3, ambas 81 %. O maior rendimento obtido foi de 0,41 mol H2/mol etanol alimentado para o catalisador de NiO/ Al2O3, na temperatura de 600 °C. A maior seletividade na temperatura de 600 °C foi de 39 %, obtida pelo catalisador de NiO/Al2O3.
36
Caliman, Cristiano Carrareto. "Estudo da eletro-oxidação de álcoois em catalisadores do tipo PtSnNiTi para aplicação em células a combustível." Universidade Federal do Espírito Santo, 2013. http://repositorio.ufes.br/handle/10/6746.
Full textAbstract:
Made available in DSpace on 2016-12-23T14:41:51Z (GMT). No. of bitstreams: 1
Cristiano Carrareto Caliman.pdf: 1377803 bytes, checksum: 0d1fc0aca431a76f5b63c8fea41daa6d (MD5)
Previous issue date: 2013-03-06Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
Electrocatalysts of type C/PtSnNiTi were prepared by thermal decomposition of polymeric precursors. The physico-chemical and electrochemical characterization of the electrocatalysts was performed by different techniques: X-ray diffraction, transmission electron microscopy, cyclic voltammetry and chronoamperometry. The X-ray diffraction results showed that the electrocatalysts comprise mainly Pt metal with face-centered cubic crystal structure and particle sizes ranging from 1.8 to 8.3 nm. In transmission electron microscopy analysis the average particle sizes observed were between 4 and 6 nm. The electrocatalysts were evaluated in the absence and presence of ethanol and glycerol in sulfuric acid medium. All showed activity towards alcohols oxidation. Furthermore, the Pt50Sn20Ni25Ti5 electrocatalyst showed the best results of cyclic voltammetry and chronoamperometry in presence of glycerol and ethanol respectively. The greater potency density obtained in cell tests was 20 mW/cm2 for the composition Pt50Sn20Ni25Ti5. Cyclic voltammetry data obtained in this study indicate that the addition of Ni and Ti in PtSn electrocatalysts increases its electrocatalytic activity toward alcohols oxidation
Eletrocatalisadores do tipo C/PtSnNiTi foram preparados por decomposição térmica dos precursores poliméricos. As caracterizações físico-química e eletroquímica foram feitas por diferentes técnicas: Difração de raios X, Microscopia eletrônica de transmissão, Voltametria cíclica, Cronoamperometria, Teste de célula e Teste de energia de ativação. Os resultados de difração de raios X mostraram que os catalisadores são principalmente compostos por Platina cúbica de face centrada e com tamanhos de partícula variando de 1,8 a 8,3 nm. Nas análises de microscopia eletrônica de transmissão foram observados tamanhos médios de partícula entre 4 e 6 nm. Os eletrocatalisadores foram avaliados na presença e ausência de etanol e glicerol em ácido sulfúrico. Todos mostraram atividade na oxidação dos álcoois. Além disso, a composição Pt50Sn20Ni25Ti5 apresentou os melhores resultados de voltametria cíclica e cronoamperometria na presença de glicerol e etanol. A maior densidade de potência obtida nos testes de célula foi de 20 mW/cm2 para a composição Pt50Sn20Ni25Ti5. De modo geral, os dados de voltametria cíclica obtidos nesse estudo indicam que a adição de Ni e Ti em catalisadores PtSn aumenta a atividade catalítica destes frente a oxidação de álcoois
37
You, Sheng Mu. "Metal organic frameworks as efficient photosensitizer for TiO₂ nanoarray anode and application to water splitting in PEC cells Fe/Ni Bimetallic organic framework deposited on TiO₂ nanotube array for enhancing higher and stable activity of oxygen evolution reaction Novel nano-architectured water splitting photoanodes based on TiO₂-nanorod mats surface sensitized by ZIF-67 coatings Surface sensitization of TiO₂ nanorod mats by electrodeposition of ZIF-67 for water photo-oxidation Electrochemically capacitive deionization of copper (II) using 3D hierarchically reduced graphene oxide architectures." Thesis, université Paris-Saclay, 2020. http://www.theses.fr/2020UPASF015.
Full textAbstract:
Les réserves de combustibles fossiles diminuent et leur utilisation illimitée depuis la révolution industrielle a généré de profonds changements du climat, notamment des cycles de la température atmosphérique. Stocker l'énergie solaire sous forme d'hydrogène produit par dissociation de l'eau est un moyen idéal pour combattre le réchauffement climatique. Les matériaux de la famille des «metal organic framework» (MOF) commencent à être utilisés comme photo-électrocatalyseurs, notamment pour la photo-dissociation de l'eau. Leur porosité extrêmement élevée et leur grande polyvalence, tant chimique que structurelle, les désignent comme des candidats potentiels pour faciliter l'absorption du rayonnement solaire et catalyser la dissociation de l'eau dans les cellules photoélectrochimiques. En contrôlant la composition chimique et le dopage du linker utilisé dans le MOF, il est possible d'ajuster l'énergie de la bande interdite, de favoriser la fonctionnalisation sur des substrats très variés ou encore d'ajuster leur résistance à la corrosion dans divers environnements chimiques. Ce sont donc des matériaux d'un grand intérêt pour la catalyse, l'électrocatalyse ou la photo-électro-catalyse. D'autre part, le TiO₂ nano-structuré, par exemple sous forme de tapis d’épaisseur micrométrique de nanotubes ou de nanofils, parfois appelé TNA, est un matériau bien adapté à la construction de photoanodes pour le dégagement d'oxygène en milieu aqueux. Il a déjà été largement étudié et décrit dans la littérature. Au cours de notre thèse, nous avons fabriqué des matériaux composites constitués de MOF de métaux de transition (Ni, Co, Fe) déposés sur TNA (TDNR et TNTA). Pour cela, nous avons utilisé une méthode électrochimique d'électrodéposition. Cela nous a permis de déposer des nanoparticules métalliques sur du TNA à potentiel fixe - 1,0 V puis de les transformer par réaction chimique avec des ligands organiques (BTC, BDC, et 2MZ) par voie thermo-thermique. Les matériaux obtenus présentent une activité électrocatalytique significative et une excellente durabilité photoélectrochimique. Ces matériaux composites ont été utilisés avec succès comme phase active dans des photo-électrodes pour la réaction de dégagement d'oxygène moléculaire (OER)The fossil fuel reserves are dwindling and their unrestricted use has generated profound changes in Earth's surface temperature and climate. Storing solar energy in the form of hydrogen produced by dissociation of water is an ideal way to mitigate global warming. Materials from the “metal organic framework” (MOF) family are starting to be used as photo-electrocatalysts, especially for photo-dissociation of water. Their extremely high porosity and their great versatility, both chemical and structural, designate them as potential candidates to facilitate the absorption of solar radiation and catalyze the dissociation of water in photoelectrochemical cells. By controlling the chemical composition and doping of the linker used in the MOF, it is possible to adjust the band gap energy, to favor the functionalization on very varied substrates or even to adjust their resistance to corrosion in various chemical environments. They are therefore materials of great interest for catalysis, electrocatalysis or photo-electro-catalysis. On the other hand, nano-structured TiO₂, for example in the form of nanotube or nanowire mats, sometimes called TiO₂ nanoarray (TNA), is a material very suitable for the construction of photoanodes for the evolution of oxygen in aqueous medium. It has already been extensively studied and described in the literature. During our thesis, we manufactured composite materials made up of MOFs of transition metals (Ni, Co, Fe) deposited on TNA (network of nanotubes or nanowires). For this we used an electrochemical method of electrodeposition (cyclic voltammetry). This allowed us to deposit metallic nanoparticles on TNA with fixed potential - 1.0 V and then transform them by chemical reaction with organic ligands (1,3,5-benzenetricarboxylic acid, BTC, 1,4-benzenedicarboxylic acid, BDC and imidazole, 2MZ) by thermal-thermal route. The materials obtained exhibit significant electrocatalytic activity and excellent photoelectrochemical durability. These composite materials have been successfully used as an active phase in photo-electrodes for the oxygen release reaction (OER)
38
Tseng, Ya-Chun, and 曾雅君. "Sequential Decarbonylation of Furfural Using Ni-based Catalysts." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/69w92r.
Full textAbstract:
碩士國立臺灣科技大學
化學工程系
106
Abstract Furfural can be obtained from biowaste and can be used as a platform chemical for producing valuable chemicals. The furfural conversion using various metal catalysts indicates that furfural can lead to different useful chemicals economically and competitively. The product distribution can be altered by the type of metal, reaction temperature and hydrogen concentration. Instead of precious metal, the cheap nickel-based catalysts are examined in this study. Our previous study shows that nickel particle size can result in different catalytic activity, product selectivity and C3 can be obtained through sequential decarbonylation of furfural. In this study, we confirm the reaction pathway of sequential decarbonylation to C3 and the effect of hydrogen concentration is examined. The Ni/SiO2 catalysts are inactive without hydrogen while decarbonylation selectivity can be increased significantly with hydrogen concentration decrease. However, the decrease of hydrogen concentration also leads to more serious catalyst deactivation. In order to increase the resistance of coke formation, we have two strategies modifying the Ni catalyst to prevent the coke. Although Ni catalysts with K doping have higher hydrogenation products, Ni/K1-SiO2 shows the higher stability and maintains high C3 selectivity. It might indicate that doping K might block the active site for decarbonylation reaction. Extensive studies regarding doping B in Ni catalyst have been considered. In our case, NiB/SiO2 shows high stability and has high C3 selectivity with high H2 concentration in FFR reaction, but not really promote the stability with lower H2 concentration in FFR reaction. Keywords:Furfural, decarbonylation, Ni catalyst, potassium, boron, C3
39
Shaikh, Ali Anaam. "Development of Non-Noble Metal Ni-Based Catalysts for Dehydrogenation of Methylcyclohexane." Diss., 2016. http://hdl.handle.net/10754/621931.
Full textAbstract:
Liquid organic chemical hydride is a promising candidate for hydrogen storage and transport. Methylcyclohexane (MCH) to toluene (TOL) cycle has been considered as one of the feasible hydrogen carrier systems, but selective dehydrogenation of MCH to TOL has only been achieved using the noble Pt-based catalysts. The aim of this study is to develop non-noble, cost-effective metal catalysts that can show excellent catalytic performance, mainly maintaining high TOL selectivity achievable by Pt based catalysts. Mono-metallic Ni based catalyst is a well-known dehydrogenation catalyst, but the major drawback with Ni is its hydrogenolysis activity to cleave C-C bonds, which leads to inferior selectivity towards dehydrogenation of MCH to TOL. This study elucidate addition of the second metal to Ni based catalyst to improve the TOL selectivity. Herein, ubiquitous bi-metallic nanoparticles catalysts were investigated including (Ni–M, M: Ag, Zn, Sn or In) based catalysts. Among the catalysts investigated, the high TOL selectivity (> 99%) at low conversions was achieved effectively using the supported NiZn catalyst under flow of excess H2. In this work, a combined study of experimental and computational approaches was conducted to determine the main role of Zn over Ni based catalyst in promoting the TOL selectivity. A kinetic study using mono- and bimetallic Ni based catalysts was conducted to elucidate reaction mechanism and site requirement for MCH dehydrogenation reaction. The impact of different reaction conditions (feed compositions, temperature, space velocity and stability) and catalyst properties were evaluated. This study elucidates a distinctive mechanism of MCH dehydrogenation to TOL reaction over the Ni-based catalysts. Distinctive from Pt catalyst, a nearly positive half order with respect to H2 pressure was obtained for mono- and bi-metallic Ni based catalysts. This kinetic data was consistent with rate determining step as (somewhat paradoxically) hydrogenation of strongly chemisorbed intermediate originating from TOL. DFT calculation indicated that Zn metal prefers to occupy the step sites of Ni where unselective C–C bond breaking was considered to preferentially occur, explaining suppression of hydrogenolysis activity. Additionally, it confirmed that the H-deficient species at methyl position group (C6H5CH2) was stable on the surface, making its hydrogenation being rate determining step, consistent with positive order in H2 pressure on TOL formation rate. This may explain the conclusive role by H2 in facilitating desorption of the H-deficient surface species that was produced through further dehydrogenation of TOL.
40
Lin, Ya-Chi, and 林雅淇. "Olefins Polymerization based on Ni（Ⅱ）Catalysts with Amino-Pyridine Ligands." Thesis, 2002. http://ndltd.ncl.edu.tw/handle/30242568600729234899.
Full textAbstract:
碩士國立臺灣大學
化學研究所
90
A family of catalysts based on the nickel (Ⅱ) complexes bearing new bidentate amino-pyridine ligands for ethylene polymerization is revealed. The metal complexes are prepared by ligand substitution reactions of Ni(DME)Br2 (DME = 1,2-dimethoxyethane) with the synthesized amino-pyridine. The bidentate ligands and metal can constitute the five- and six-membered metallocycles. The single-crystal X-ray crystallographic analysis shows that the coordination sphere around the metal canter is disposed in tetrahedral, trigonal bipyramidal or square planar configuration. The angles of N-Ni-N’ are 81±2° in the five-membered metallocycles; and are 98±0.5° in the six-membered metallocycles. The SQUID data confirm that the electronic configuration of the nickel complexes has two unpaired electrons. The title catalysts activated by methylaluminoxane (MAO) are found to efficiently convert ethylene to polyethylene (PE) with the TOF of 103~105 g/mol Ni．h. The complexes with five-membered metallocycles exhibit better activity than those with six-membered metallocycles. The yielded PE are of relatively low molecular weight (1000~3000), low branch number (＜100) and high crystallinity, comparing with the PE products obtained in use of the nickel catalysts bearing other amine-imine bidentate ligands in this lab. The electronic and steric effects of the amino-pyridine ligands substantially influence the catalytic activity of polymerization. In a case using the catalyst with the ketamine pyridine ligand, the activity is one order of magnitude greater than the analogous catalyst with the aldamine pyridine ligand. The reaction conditions for polymerization are also crucial. The reaction activity depends on the amount of MAO used, and is proportional to the ethylene pressure in the region of 14 to 21 bar. The temperature effect is examined in the range of 0~70 ℃, and it is found that the activity is optimized at 35 ℃with TOF = 843 kg of polymer/mol of cat．h.
41
Wang, Shih-Kai, and 王世凱. "Homopolymerization and copolymerization of tert-butyl methacylate and norbornene with Ni-based/MAO catalysts." Thesis, 2001. http://ndltd.ncl.edu.tw/handle/81076786183620472488.
Full textAbstract:
碩士國立交通大學
應用化學系
89
The homopolymerization and copolymerization of tert-butyl methacylate (tBMA) and norbornene (NB) with nickel (Ⅱ) acetylacetonate [Ni(acac)2] in combination with methylaluminoxane (MAO) were systematically investigated in this study. This catalytic system shows a higher activity towards homopolymerization of both norbornene and tert-butyl methacrylate. For random copolymerization, an increase in the initial tert-butyl methacrylate leads to gradual loss of activity relative to nobornene homopolymerization. On the other hand, a drastic loss of activity, relative to tert-butyl methacrylate homopolymerization, was found for very low feed contents of norbornene. These results are qualitatively interpreted using the trigger coordination mechanism proposed by Ystenes. From the NMR analysis, the fully saturated structure of polynorbornene indicates that these two monomers polymerize by an ethylenc type addition reaction. Determination of reactivity ratios indicates a much higher reactivity for norbornene than tBMA (rNB=5.4 and rtBMA=0.0196), which is interpreted by the corordination mechanism. From the thermal analyses of DSC and TGA, these acrylate-norbornene copolymers exhibit glass transition temperature (Tg) ranging from 100℃ to 250℃ depending on compositions and have an anhydrate bond formating from 200℃ to 250℃. Finally, these copolymers are transparent as amorphous with higher polarity relative to other cyclo-olefin copolymer and more solvable materials in organic solvent.
42
Chen, Chan-Zen, and 陳長仁. "A Comparative Study on Methane Reforming of Carbon Dioxide over Some Ni-based Catalysts." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/59123644744671448472.
Full textAbstract:
碩士國立成功大學
化學工程學系碩博士班
95
The process of carbon dioxide reforming of methane (CH4 + CO2 → 2CO + 2H2), which consumes two greenhouse gases and produces synthesis gas, is worth developing. In this study, the catalysts with high catalytic activity for this reaction were investigated. The research included two parts. In the first part, the influencing factors for preparing the perovskite-type catalysts were investigated and the proper preparation parameters were determined. The activity tests of several kinds of catalysts were carried out in the second part, and the catalyst with the best performance and coke resistance was picked up. In addition, the physical and chemical properties of catalysts were characterized to find their effect on the catalytic activity. When perovskite-type catalysts were prepared by the sol-gel method, the main affecting factors are ratio of citric acid to metal ion, ratio of citric acid to ethylene glycol, pH value calcination temperature and heating rate. In this study, each factor was changed individually to determine its effect on catalyst performance. SEM and XRD were used to characterize the catalysts. The results show that when the ratio of citric acid to metal ion is between 3 and 4 and that of citric acid to ethylene glycol is 1 in the preparation of catalyst precursor, the catalyst particles are smaller and more uniform. For calcination process, the temperature should be raised to 700℃ with heating rate of 10℃/min and held for 2 hours to get the smallest (<100 nm) and most completely crystallized catalyst particles. The result of activity tests reveal that the optimal Ni loading in Ce0.75Zr0.25O2 is 5 wt%. Among several noble metals tested, Ru with Ru/Ni=0.1 added to this catalyst, the highest activity could be obtained. The activity tests of hydrotalcite-like catalyst, Ni-Mg-Al, with different metal ratios show that the activity was the highest when the ratio of Ni/Mg/Al equals to 1/5/2. These two catalysts can produce CO and H2 at 400℃. Their conversions remained constant during an on-stream of 30 hours at 600℃. This fact suggests that these catalysts can impede carbon deposition and have excellent durability.
43
Cheng-HanLin and 林成翰. "One-step Hydro-conversion of Palm Oil into Renewable Jet Fuels over Ni-based Catalysts." Thesis, 2019. http://ndltd.ncl.edu.tw/handle/9pxsuv.
Full text
44
Liu, Ming-Chung, and 劉明宗. "Preparation and Characterization of Sputtered Ni and Co Based Catalysts for Thermal CVD Grown Carbon Nanotubes." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/52685504061340501720.
Full textAbstract:
碩士國立臺灣海洋大學
材料工程研究所
94
Abstract In this study, we present a new effective method of synthesizing carbon nanotubes (CNTs) using metallic catalysts synthesized by r.f. sputtering technique. Base on the widely used immiscible principle, Co and Cu (Co-Cu), Ni and C (Ni-C) as well as Co, Cu and C (Co-Cu-C) were chosen as the sputtering targets to form catalyst films on the silicon substrate, followed by Thermal CVD for growing CNTs. The results of AES, XPS and SIMS showed that the catalyst films have Cu, Co and Ni elements and minor contaminants. The precise compositions of these films were also revealed by SIMS measurements. Combined with XRD results, we demonstrated that the insoluble elements were supersaturated in Ni and Cu solid solutions. SEM results proved that the crystallite sizes of the films were approximately 20-30 nm, and the diameters of CNTs were about 50-100 nm. Raman spectra of CNTs showed two typical peaks of D and G bands, respectively, which suggested that the CNTs grown on the films are multi-wall CNTs with lattice distortion and other defects. TEM results showed that the diameter of multi-wall carbon nanotubes were approximately 25-50 nm. TEM results also suggest that metallic particles can be observed on the top of CNTs, which agreed well with the top growth mechanism. Additionally, the films were thermally annealed at different elevated temperatures for various times in order to gain different local particle sizes, which were found closely related to subsequent CNT diameters grown on these catalyst films. In a conclusion, CNTs can be readily grown on the as-sputtered metallic catalyst films and the diameter of CNTs could be controlled by the crystallite sizes of the films through the top growth mechanism.
45
Liu, Hsin Yi, and 劉欣宜. "Hydrogen production by low temperature partial oxidation of butane over Ni-based catalysts modified by platinum." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/20928666575881686418.
Full text
46
Chiang, Chao-Lung, and 江昭龍. "Preparation, Characterization, and CO2 Conversion Efficiencies of Ni-Ga and Cu-based Catalysts for Methanol and Dimethyl Ether Formations." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/mstzzr.
Full textAbstract:
博士元智大學
化學工程與材料科學學系
106
In this study, catalytic nickel-gallium (Ni5Ga3) and Cu-based catalysts (CuO-ZnO-Al2O3, CZA) have been prepared with co-precipitation methods. Supported nickel-gallium and Cu-based catalysts have also been obtained by ultrasonic-stirring with supports including silica gel (SiO2), protonated Y-type zeolite (HYZ) and protonated Beta-type zeolite (HBZ) in a slurry form. Crystal structures and morphologies of catalysts have been investigated and observed by X-ray diffraction (XRD) and field-emission scanning electronic microscopy (FE-SEM), confirming that nickel-gallium and Cu-based catalysts were Ni5Ga3 and CuO-ZnO-Al2O3 structure. FE-SEM microphotos have shown that supports could maintain the particle size being uniform in the durations of MeOH and DME formations. X-ray photon spectroscopy (XPS) spectra indicated that the effective component in Ni-Ga and Cu-based catalysts were respectively gallium and copper species. Oxidation state and bond distances of metal and its neighbour atoms were analyzed by X-ray absorption near-edge structure (XANES)/Extended X-ray absorption fine structure (EXAFS). It displayed that the oxidation states of gallium were Ga(0) and Ga(III) before and after MeOH formation, but nickel remained Ni(0). For Cu-based catalyst, the oxidation states of copper and zinc were Cu(II) and Zn(II), respectively. The inverse relationship of bond distances of metal (Ni5Ga3: Ni and Ga; CZA: Cu and Zn) and its neighbour atoms during the reaction were exhibited in EXAFS excluding Ni5Ga3/SiO2, CZA/HYZ, and CZA/HBZ. It demonstrated that structure, morphology, chemical composition, and fine structure of catalyst could be remained during MeOH/DME formation by dispersing nickel-gallium and Cu-based catalysts onto supports. In addition, the produced species sorts and their concentrations have been respectively analyzed using a dual fixed-bed catalyst-filled column reactor with an online FTIR (Fourier transformed infrared spectrum) and GC (gas chromatograph) spectra at the terminal to obtain the conversion of feedstock and the selectivity/yield of products. Online FTIR and GC spectra show that catalytic performances of catalysts at a constant pressure and variable temperatures (P=50 bar, T=150, 250, and 350 oC) of Ni-Ga and Cu-based catalysts have been enhanced after nickel-gallium and Cu-based catalyst dispersed onto supports. The highest MeOH yield could reach to 62.1 (150 oC), 84.7 (250 oC), and 82.5% (350 oC) by using Ni5Ga3/SiO2. The highest DME yield of CZA was 60.2%; it could be raised to 71.5% (CZA/HYZ) by loading onto HYZ, but lowered to 31.8% by supporting onto HBZ (CZA/HBZ). Rate equilibrium constants of MeOH formation were 0.150 (150oC), 0.473 (250 oC), and 0.477 h-1 (350 oC) that were much higher than theoretical values of 4.67×10-4 (150 oC), 2.22×10-5 (250 oC), and 2.47×10-6 (350 oC) h-1 by using Ni5Ga3 catalyst. Activation energies of MeOH formation using Ni5Ga3 and Ni5Ga3/SiO2 were 3.21 and 2.72 kJ/mol, respectively. In terms of DME formation, the highest rate equilibrium constant using CZA was 1.65×103 L/mol-h. It could be raised to 2.26×103 L/mol-h L/mol-h after supporting onto HYZ (CZA/HYZ), but lowered to 0.70×103 L/mol-h using CZA/HBZ. Activation energies of DME formation using CZA, CZA/HBZ, and CZA/HYZ were respectively 2.04, 2.26, and 1.16 kJ/mol. In addition, Gibbs energies of MeOH formation were 6.67 (150 oC), 3.26 (250 oC), and 3.83 (350 oC) kJ/mol that were much lower than theoretical values including 26.97 (150 oC), 46.59 (250 oC), and 66.87 (350oC) kJ/mol. The Gibbs energies of DME formation by using CZA, CZA/HBZ, and CZA/HYZ were respectively -40.07, -40.00, and -40.67 kJ/mol that were much lower than theoretical values of -12.64, -9.96, and -7.28 kJ/mol. Eventually, the cost assessment for a 10-TPD (ton per day) off-gas utility process of a petrochemical refinery plant showed that the daily income was USD$ 5,002,359/d with 3.49 years of payback.
47
Guan, Shih-Hau, and 管仕豪. "Studies of Carbon-Carbon Bond Formation Reactions Based on Ni(II) and Pd(II) Catalysts Bearing Nitrogen-Containing Hetero-functional Bidentate Ligands." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/64240078354258185606.
Full textAbstract:
博士國立臺灣大學
化學研究所
95
In this thesis, carbon-carbon bond formations are studied through three kinds of reactions: styrene polymerization, cross-couplings and nucleophilic additions. A new series of Ni(II) complexes [(N,N'')NiBr2] bearing bidentate amino-oxazoline ligands have been synthesized and applied for polymerization of styrene. With cocatalyst, MAO, these Ni(II) complexes 4 are highly efficient catalysts for styrene polymerization with activities up to ~107 g / mol [Ni] × h under optimized conditions, which possess the best performance among the catalytic Ni systems now. Effects of the structures of catalysts and the reaction parameters on the activities and characteristic properties for the polymers have been discussed here. From the 13C NMR data, the degree of stereoregularity of the synthesized polystyrene could be moderately controlled by the chiral center in the oxazoline ring although atactic polymers were generally obtained by these Ni(II) catalysts. The neutral Pd(II) complexes [(N,N'')PdCH3Cl] 5 and the cationic complexes [(N,N'')PdCH3L]+ 7 were prepared for studying the mechanism for polymerization. For the neutral Pd complexes, their coordination chemistry, dynamic behavior, geometric isomerization, and reactivity toward alkynes have been studied herein. Furthermore, reactions of cationic Pd complexes with styrene, which led to the η3-π-benzyl Pd(II) complexes, made the possible mechanism of the polymerization of styrene for the Ni(II) system. Neutral Pd(II) complexes were synthesized and involved nitrogen-containing ligands, such as mono-oxazolines, amino-oxazolines and pyridyl-pyrazoles. Among them, the chloromethylpalladium(II) complex with bidentate pyridyl-pyrazole ligands exhibited excellent activities toward Heck coupling reactions with high TONs up to 95,000,000, comparable to the palladacycle systems. In addition, the pyridyl-azolate ligands are good candidates for catalytic Suzuki-Miyaura cross-coupling reactions. In the presence of Pd(OAc)2, KF as base, and such ligands in EtOH, the couplings of aryl bromides with phenylboronic acids could proceed with high conversions at room temperature in the air. Under the same conditions, it could slowly couple aryl chloride with phenylboronic acids, which is rare for Pd catalysts with bidentate nitrogen donor ligands. Finally, we synthesized a series of cationic allylpalladium(II) complexes bearing asymmetric amino-oxazoline ligands. The isomer interconversion is demonstrated by NOESY spectra to show a syn-syn, anti-anti exchange. Nucleophilic attacks to the Pd complexes would result in the linear and branched products. The regioselectivity is strongly dependent on the steric/electronic properties of the nucleophiles and the polarity of the used solvents.
48
Guan, Shih-Hau. "Studies of Carbon-Carbon Bond Formation Reactions Based on Ni(II) and Pd(II) Catalysts Bearing Nitrogen-Containing Hetero-functional Bidentate Ligands." 2007. http://www.cetd.com.tw/ec/thesisdetail.aspx?etdun=U0001-1108200716185900.
Full text
49
Wierenga, TS. "N-heterocyclic carbene-based Pd and Ni complexes and their applications to the activation of alkylnitriles." Thesis, 2019. https://eprints.utas.edu.au/31480/1/Wierenga_whole_thesis.pdf.
Full textAbstract:
α-Cyanocarbanion complexes are an interesting class of complexes that contain a nitrile ligand featuring a deprotonated α-carbon. Chapter 1 gives an overview of the various synthetic methods, bonding modes and applications that have been established in the literature. Of particular interest is the role these complexes have as intermediates in the formation of various different compounds including the synthetically versatile β-hydroxynitriles.
One example of a catalyst that can be used to synthesise a range of β-hydroxynitriles from the corresponding aldehydes under base free conditions is the POCOP pincer complex [{2,6-(iPr\(_2\)PO)\(_2\)C\(_6\)H\(_3\)}Ni(CH\(_2\)CN)]. DFT calculations outlined in Chapter 2 indicated some of the key features of the complex in relation to its catalytic performance. These were that the –CH\(_2\)CN ligand isomerises to yield the active N-bound catalyst in solution, the trans donation effect of the phenyl ring lowers the energy of the transition state of the reaction and the rate determining transition state involves a 5 coordinate intermediate and therefore the steric hindrance of the phosphine substituent influences the performance.
Chapter 3 describes a series of bis(NHC) palladium(II) complexes (NHC = N-heterocyclic carbene) of the type [{(RIm)\(_2\)CH\(_2\)}Pd(NCMe)\(_2\)][PF\(_6\)]\(_2\) with different N-substituents which were reacted with NaOH in CH\(_3\)CN. Two different products were formed under similar conditions. [{(RIm)\(_2\)CH\(_2\)}Pd(CH\(_2\)CN)\(_2\)] was observed for both the R = Me and 2,4,6-trimethyphenyl (Mes) substituent while [{([RIm]\(_2\)CH\(_2\))Pd(μ–CH\(_2\)CN)}\(_2\)][PF\(_6\)]\(_2\) was observed for both the R = Mes and 2,6-diisopropylphenyl substituent. The two initial products that were not formed under these conditions could be synthesised under modified conditions. Complexes of the type [{(MesIm)\(_2\)CH\(_2\)}Pd(NCR)\(_2\)][PF\(_6\)]\(_2\) where R = CH\(_2\)CH\(_3\) and CH\(_2\)CH\(_2\)CH\(_3\) were also synthesised, however, subsequent conversion to the corresponding [{(RIm)\(_2\)CH\(_2\)}Pd(CHRCN)\(_2\)] was not successful.
In Chapter 4 a range of NHC-containing pincer complexes were synthesised due to their close structural similarity to the successful POCOP complex and therefore may result in successful catalytic applications under similar reaction conditions. These complexes contain two NHC ligands bridged by either a pyridine or phenyl ring. [CNC\(^{iPr}\)Pd(CH\(_2\)CN)][SbF\(_6\)] was synthesised from the corresponding NCMe complex following the same method used for the bis(NHC) complexes. [C^C^C\(^{Me}\)Pd(NCMe)][SbF\(_6\)] was prepared from the previously reported Br complex. However attempts to form the corresponding –CH\(_2\)CN complex were not fruitful.
A number of alternative synthetic approaches were attempted for the desired non methylene linked phenyl based complex using various ligand modifications. Initially reactions were based on the pro-ligands of the type [1,3-{(R)ImH}\(_2\)Ph]X\(_2\) where R = CH\(_3\) and X = I or R = nBu and X = Br were reacted in various approaches, however, due to the difficulty of the three C–H metallations an alternative pathway was pursued. This strategy investigated the preparation of a phenyl–OTf based pro-ligand, however, due to difficulties in synthesising the pro-ligand an alternative approach was needed.
A series of pro-ligands of the type [2,6-(RImH)\(_2\)1-BrPh]X\(_2\) where R = CH\(_3\) and X = I or R = nBu, Ad and X = Br were synthesised from 2-bromo-1,3-difluorobenzene. The desired [CCC\(^{nBu}\)PdBr] was then successfully prepared from the corresponding pro-ligand in good yield. This provided an alternative synthetic pathway to that previously developed for these complexes, although the yield was lower, the lack of a zirconium transfer reagent and the use of air-stable starting materials and higher atom efficiency make this method advantageous to previous literature methods. The catalytically relevant –NCMe derivative was synthesised, however, the attempted formation of the –CH\(_2\)CN ligated complex was not successful. [CCC\(^{nBu}\)NiCl] was also synthesised from the corresponding pro-ligand which then was reacted further to form the catalytically relevant NiNCMe complex.
The catalytic studies described in Chapter 5 explored the C–C coupling of benzaldehyde and CH3CN to yield 3-hydroxy-3-phenylpropionitrile. Various bis(NHC) and NHC containing pincer –CH\(_2\)CN complexes were tested, however, no reaction was observed. For the pincer complexes in which the –CH\(_2\)CN complex could not be succesfully synthesised, the –NCMe complex was used as a pre-catalyst in solution with a catalytic amount of NaOH to prepare the required complex in situ. However, the yield of the product was identical to the background reaction performed in the absence of the transition metal catalyst.
50
Chen, Hsin-Hsien, and 陳幸賢. "SiC Based Catalyst Supports Fabricated from Luffa Cylindrica and Their Application in Ni-catalyzed CO Oxidation." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/49228707470187062594.
Full textAbstract:
碩士大同大學
材料工程學系(所)
96
The purpose of this study is to compare the effects of three supports for Ni catalyst: SiC prepared from Luffa Cylindrica,γ-Al2O3 prepared by the sol-gel method and SiC coated with γ-Al2O3. The supports were dripped with different concentration Ni(NO3)2 by incipient wetness impregnation method to produce supported Ni catalysts. The Luffa Cylindrica was first transformed into charcoal by carbonization in N2 atmosphere. Proper proportion of Si was then reacted with porous charcoal to form porous SiC with the structure of Luffa Cylindrica. The SiC was immersed in Al(OH)3 prepared by sol-gol method, and then dried and calcined. SiC support withγ-Al2O3 coating was formed. Supported Ni catalysts was prepared by dripping Ni(NO3)2 solution of different concentration into the supports (impregnation method). After dried, calcined and reduced in H2/N2 atmosphere, supported Ni catalysts were obtained. The results pointed out that the support of SiC with 15wt% Ni had Ni well dispersed. Ni particles begun to agglomerate when Ni was 30 wt％. The agglomeration was significant when Ni was 40 wt%. The agglomeration reduced the activity of Ni. Ni catalysts supported onγAl2O3-SiC or γAl2O3 did not agglomerate, and the catalysts activity increased monotonically with Ni content. After SiC was coated with γ-Al2O3, specific surface area increased ( from 16 m2/g to 131 m2/g), and partial large pores shrank, and some small pores (~1 μm) were closed. This resulted in decreasing Ni content into supports. Thus, when comparing the different supports with 30 wt％ Ni, and Ni/ SiC catalyst activity was better than Ni/γAl2O3-SiC. Comparing CO oxidation reaction activity of different supports with different Ni content, it showed that catalyst Ni/γAl2O3- SiC with 60 wt％ Ni had the highest catalytic activity( T50 = 265 ℃). For Ni/SiC,the highest activity occurred when Ni was 30％( T50 =272 ℃ ).