Segui questo link per vedere altri tipi di pubblicazioni sul tema: Catalysts – Analysis.
Articoli di riviste sul tema "Catalysts – Analysis"
Cita una fonte nei formati APA, MLA, Chicago, Harvard e in molti altri stili
Vedi i top-50 articoli di riviste per l'attività di ricerca sul tema "Catalysts – Analysis".
Accanto a ogni fonte nell'elenco di riferimenti c'è un pulsante "Aggiungi alla bibliografia". Premilo e genereremo automaticamente la citazione bibliografica dell'opera scelta nello stile citazionale di cui hai bisogno: APA, MLA, Harvard, Chicago, Vancouver ecc.
Puoi anche scaricare il testo completo della pubblicazione scientifica nel formato .pdf e leggere online l'abstract (il sommario) dell'opera se è presente nei metadati.
Vedi gli articoli di riviste di molte aree scientifiche e compila una bibliografia corretta.
1
Lomic, Gizela, Erne Kis, Goran Boskovic e Radmila Marinkovic-Neducin. "Application of scanning electron microscopy in catalysis". Acta Periodica Technologica, n. 35 (2004): 67–77. http://dx.doi.org/10.2298/apt0435067l.
Testo completoAbstract (sommario):
A short survey of various information obtained by scanning electron microscopy (SEM) in the investigation of heterogeneous catalysts and nano-structured materials have been presented. The capabilities of SEM analysis and its application in testing catalysts in different fields of heterogeneous catalysis are illustrated. The results encompass the proper way of catalyst preparation, the mechanism of catalyst active sites formation catalysts changes and catalyst degradation during their application in different chemical processes. Presented SEM pictures have been taken on a SEM JOEL ISM 35 over 25 years of studies in the field of heterogeneous catalysis.
2
Su, Shu Hua, Shi Ye Feng, Yuan Fang Zhao, Qiang Lu, Wei Liang Cheng e Chang Qing Dong. "Comparison of Three Types of NH3-SCR Catalysts". Applied Mechanics and Materials 130-134 (ottobre 2011): 418–21. http://dx.doi.org/10.4028/www.scientific.net/amm.130-134.418.
Testo completoAbstract (sommario):
The selective catalysis reduction (SCR) is one of the most promising technologies for NOx reduction at present. There are three types of NH3-SCR catalysts in the market, honeycomb catalyst, plate-types catalyst and corrugated catalyst. This paper firstly describes the preparation of the three types of catalysts, and then analyzes their performance. The analysis indicates the catalyst structure plays an important role on their performance. The honeycomb catalyst and plate-type catalyst are widely utilized in world’s coal power station, which should be due to their excellent capabilities of ash prevention, wear resistance and anti-poisoning.
3
Samoilov, N. A., M. S. Melgunov e V. A. Zhilina. "Analysis of the performance of the industrial Co-Mo catalyst for hydrotreatment". Kataliz v promyshlennosti 19, n. 5 (17 settembre 2019): 345–50. http://dx.doi.org/10.18412/1816-0387-2019-5-345-350.
Testo completoAbstract (sommario):
The process of hydrotreatment of diesel fuel (fraction 180–320 °C) over fresh and spent (after two-year operation in an industrial reactor) Co-Mo catalyst was studied. It was established that the sulfur contents were rather close to one another in the diesel fuel samples treated using the fresh and spent catalysts, even though the specific surface area was 40 % smaller in the spent catalyst compared to that in the fresh sample. Dependence of effective constant keff of hydrodesulfurization on the temperature of low-temperature hydrotreatment (below 320–330 °C) was characteristic of the kinetic range of heterogeneous catalysis complicated by external diffusion resistance. When the temperature was elevated up to 420 °C, the process of diesel hydrotreatment transferred to the external diffusion region. Activation energies of hydrodesulfurization were comparable over the spent and fresh catalysts (81.1 and 80.5 kJ/mol, respectively). A hypothesis of the specific catalyst deactivation was discussed.
4
Tišler, Zdeněk, Pavla Vondrová, Kateřina Hrachovcová, Kamil Štěpánek, Romana Velvarská, Jaroslav Kocík e Eliška Svobodová. "Aldol Condensation of Cyclohexanone and Furfural in Fixed-Bed Reactor". Catalysts 9, n. 12 (14 dicembre 2019): 1068. http://dx.doi.org/10.3390/catal9121068.
Testo completoAbstract (sommario):
Aldol condensation reaction is usually catalysed using homogeneous catalysts. However, the heterogeneous catalysis offers interesting advantages and the possibility of cleaner biofuels production. Nowadays, one of the most used kinds of heterogeneous catalysts are hydrotalcites, which belong to a group of layered double hydroxides. This paper describes the aldol condensation of cyclohexanone (CH) and furfural (F) using Mg/Al mixed oxides and rehydrated mixed oxides in order to compare the catalyst activity after calcination and rehydration, as well as the possibility of its regeneration. The catalysts were synthesized by calcination and subsequent rehydration of the laboratory-prepared and commercial hydrotalcites, with Mg:Al molar ratio of 3:1. Their structural and chemical properties were determined by several analytical methods (inductively coupled plasma analysis (ICP), X-ray diffraction (XRD), diffuse reflectance infrared Fourier transform spectroscopy (DRIFT), specific surface area (BET), thermogravimetric analysis (TGA), temperature programmed desorption (TPD)). F-CH aldol condensation was performed in a continuous fixed-bed reactor at 80 °C, CH:F = 5:1, WHSV 2 h−1. The rehydrated laboratory-prepared catalysts showed a 100% furfural conversion for more than 55 h, in contrast to the calcined ones (only 24 h). The yield of condensation products FCH and F2CH was up to 68% and 10%, respectively. Obtained results suggest that Mg/Al mixed oxides-based heterogeneous catalyst is suitable for use in the aldol condensation reaction of furfural and cyclohexanone in a fixed-bed reactor, which is an interesting alternative way to obtain biofuels from renewable sources.
5
Crozier, P. A., e M. Pan. "Quantitative nano-characterization of heterogeneous catalysts". Proceedings, annual meeting, Electron Microscopy Society of America 53 (13 agosto 1995): 398–99. http://dx.doi.org/10.1017/s0424820100138361.
Testo completoAbstract (sommario):
Heterogeneous catalysts can be of varying complexity ranging from single or double phase systems to complicated mixtures of metals and oxides with additives to help promote chemical reactions, extend the life of the catalysts, prevent poisoning etc. Although catalysis occurs on the surface of most systems, detailed descriptions of the microstructure and chemistry of catalysts can be helpful for developing an understanding of the mechanism by which a catalyst facilitates a reaction. Recent years have seen continued development and improvement of various TEM, STEM and AEM techniques for yielding information on the structure and chemistry of catalysts on the nanometer scale. Here we review some quantitative approaches to catalyst characterization that have resulted from new developments in instrumentation.HREM has been used to examine structural features of catalysts often by employing profile imaging techniques to study atomic details on the surface. Digital recording techniques employing slow-scan CCD cameras have facilitated the use of low-dose imaging in zeolite structure analysis and electron crystallography. Fig. la shows a low-dose image from SSZ-33 zeolite revealing the presence of a stacking fault.
6
Bergbreiter, David E., Andrew Kippenberger e Zhenqi Zhong. "Catalysis with palladium colloids supported in poly(acrylic acid)-grafted polyethylene and polystyrene". Canadian Journal of Chemistry 84, n. 10 (1 ottobre 2006): 1343–50. http://dx.doi.org/10.1139/v06-076.
Testo completoAbstract (sommario):
Grafts of poly(acrylic acid) on polyethylene powder (PE-g-PAA) or polystyrene (PS-g-PAA) can be used to support Pd(0) crystallites that function like a homogeneous Pd(0) catalyst in some reactions. These Pd–PE-g-PAA catalysts were active in allylic substitution reactions in the presence of added phosphine ligand. A catalyst analogous to the Pd–PE-g-PAA powder catalyst on polystyrene (Pd–PS-g-PAA) was similarly active for allylic substitution and could also be used in Heck reactions at 80–100 °C in N,N-dimethylacetamide (DMA). Analysis of the product solutions for Pd leachate and a correlation of the Pd leaching with product formation in the allylic substitution chemistry for both types of catalysts suggests that the active catalysts in these reactions are leached from the support. In the case of the allylic substitution reaction, external triphenylphosphine and substrate together are required for the chemistry and Pd leaching.Key words: catalysis, palladium, allylic substitution, grafted polystyrene, supported catalysts.
7
du Plessis, Hester, Roy Forbes, Werner Barnard, Alta Ferreira e Axel Steuwer. "In situ reduction study of cobalt model Fischer-Tropsch synthesis catalyst". Acta Crystallographica Section A Foundations and Advances 70, a1 (5 agosto 2014): C948. http://dx.doi.org/10.1107/s2053273314090512.
Testo completoAbstract (sommario):
Fischer-Tropsch (FT) synthesis is an important process to manufacture hydrocarbons and oxygenated hydrocarbons from mixtures of carbon monoxide and hydrogen (syngas). The catalysis process occurs on for example cobalt metal surfaces at elevated temperatures and pressures. A fundamental understanding of the reduction pathway of supported cobalt oxides, and the intermediate species present during the activation, can assist in developing improved industrial supported cobalt catalysts. Measurements were done during in-situ hydrogen activation of a model Co/alumina catalyst using in-situ synchrotron X-ray powder diffraction and pair-distribution function (PDF) analysis. Strong metal-support interactions between the Co and the support1 can make the catalyst more stable towards sintering. The supported cobalt oxide catalyst precursors have to undergo reductive pre-treatments before their use as FT catalysts. During activation the cobalt oxides evolve, resulting in the formation of metallic cobalt depending on temperature, pressure of activation gases, concentration, time of exposure etc. The effect of hydrogen activation treatments on model catalysts were reported previously [1,2], however analysis of the alumina support phases was excluded from the interpretation by subtraction and normalisation. The PDF refinement accounted for all cobalt present in the catalyst sample and after reduction mainly Co(fcc) with a little Co(hcp) was found to be present. This is a novel approach to in situ PDF analysis of catalysts containing a mixture of phases [3].
8
van Slagmaat, Christian A. M. R., Khi Chhay Chou, Lukas Morick, Darya Hadavi, Burgert Blom e Stefaan M. A. De Wildeman. "Synthesis and Catalytic Application of Knölker-Type Iron Complexes with a Novel Asymmetric Cyclopentadienone Ligand Design". Catalysts 9, n. 10 (22 settembre 2019): 790. http://dx.doi.org/10.3390/catal9100790.
Testo completoAbstract (sommario):
Asymmetric catalysis is an essential tool in modern chemistry, but increasing environmental concerns demand the development of new catalysts based on cheap, abundant, and less toxic iron. As a result, Knölker-type catalysts have emerged as a promising class of iron catalysts for various chemical transformations, notably the hydrogenation of carbonyls and imines, while asymmetric versions are still under exploration to achieve optimal enantio-selectivities. In this work, we report a novel asymmetric design of a Knölker-type catalyst, in which the C2-rotational symmetric cyclopentadienone ligand possesses chiral substituents on the 2- and 5-positions near the active site. Four examples of the highly modular catalyst design were synthesized via standard organic procedures, and their structures were confirmed with NMR, IR, MS, and polarimetry analysis. Density functional theory (DFT) calculations were conducted to elucidate the spatial conformation of the catalysts, and therewith to rationalize the influence of structural alterations. Transfer- and H2-mediated hydrogenations were successfully established, leading to appreciable enantiomeric excesses (ee) values up to 70%. Amongst all reported Knölker-type catalysts, our catalyst design achieves one of the highest ee values for hydrogenation of acetophenone and related compounds.
9
Thongboon, Surached, Pacharaporn Rittiron, Danusorn Kiatsaengthong, Thanaphat Chukeaw e Anusorn Seubsai. "Propylene Epoxidation to Propylene Oxide Over RuO2, CuO, TeO2, and TiO2 Supported on Modified Mesoporous Silicas". Journal of Nanoscience and Nanotechnology 20, n. 6 (1 giugno 2020): 3466–77. http://dx.doi.org/10.1166/jnn.2020.17408.
Testo completoAbstract (sommario):
Direct gas phase epoxidation of propylene to propylene oxide (PO) using O2 is a challenging problem in catalysis research. Silica-supported ruthenium-copper-based catalysts have been recently reported to be promising for propylene epoxidation. In this work, mesoporous silica supports modified with RuO2, CuO, and TeO2 with and without TiO2 were investigated for propylene epoxidation to PO. The prepared catalysts were divided into two groups. The first group consisted of mesoporous silica supports modified with RuO2, CuO, and TeO2, and the second group consisted of the same components as the first group but adding TiO2. The prepared supports and catalysts were characterized using BET surface area analysis and other advanced instrument techniques. It was found that the catalyst made with RuO2 and TeO2 impregnated onto porous silica modified with CuO and TiO2 (denoted as RuTe/CuTiSi) exhibited an excellent PO formation of 344 gPO h−1 kg−1cat, which was superior to that of the other prepared catalysts. Moreover, the addition of TiO2 into the catalyst greatly improved the PO formation rate and the arrangement of active components in the catalyst and strongly influenced catalytic performance.
10
Shareef, Muhammad Faizan, Muhammad Arslan, Naseem Iqbal, Nisar Ahmad e Tayyaba Noor. "Development of Hydrotalcite Based Cobalt Catalyst by Hydrothermal and Co-precipitation Method for Fischer-Tropsch Synthesis". Bulletin of Chemical Reaction Engineering & Catalysis 12, n. 3 (28 ottobre 2017): 357. http://dx.doi.org/10.9767/bcrec.12.3.762.357-362.
Testo completoAbstract (sommario):
This paper presents the effect of a synthesis method for cobalt catalyst supported on hydrotalcite material for Fischer-Tropsch synthesis. The hydrotalcite supported cobalt (HT-Co) catalysts were synthesized by co-precipitation and hydrothermal method. The prepared catalysts were characterized by using various techniques like BET (Brunauer–Emmett–Teller), SEM (Scanning Electron Microscopy), TGA (Thermal Gravimetric Analysis), XRD (X-ray diffraction spectroscopy), and FTIR (Fourier Transform Infrared Spectroscopy). Fixed bed micro reactor was used to test the catalytic activity of prepared catalysts. The catalytic testing results demonstrated the performance of hydrotalcite based cobalt catalyst in Fischer-Tropsch synthesis with high selectivity for liquid products. The effect of synthesis method on the activity and selectivity of catalyst was also discussed. Copyright © 2017 BCREC Group. All rights reservedReceived: 3rd November 2016; Revised: 26th February 2017; Accepted: 9th March 2017; Available online: 27th October 2017; Published regularly: December 2017How to Cite: Sharif, M.S., Arslan, M., Iqbal, N., Ahmad, N., Noor, T. (2017). Development of Hydrotalcite Based Cobalt Catalyst by Hydrothermal and Co-precipitation Method for Fischer-Tropsch Synthesis. Bulletin of Chemical Reaction Engineering & Catalysis, 12(3): 357-363 (doi:10.9767/bcrec.12.3.762.357-363)
11
Shareef, Muhammad Faizan, Muhammad Arslan, Naseem Iqbal, Nisar Ahmad e Tayyaba Noor. "Development of Hydrotalcite Based Cobalt Catalyst by Hydrothermal and Co-precipitation Method for Fischer-Tropsch Synthesis". Bulletin of Chemical Reaction Engineering & Catalysis 12, n. 3 (28 ottobre 2017): 357. http://dx.doi.org/10.9767/bcrec.12.3.762.357-363.
Testo completoAbstract (sommario):
This paper presents the effect of a synthesis method for cobalt catalyst supported on hydrotalcite material for Fischer-Tropsch synthesis. The hydrotalcite supported cobalt (HT-Co) catalysts were synthesized by co-precipitation and hydrothermal method. The prepared catalysts were characterized by using various techniques like BET (Brunauer–Emmett–Teller), SEM (Scanning Electron Microscopy), TGA (Thermal Gravimetric Analysis), XRD (X-ray diffraction spectroscopy), and FTIR (Fourier Transform Infrared Spectroscopy). Fixed bed micro reactor was used to test the catalytic activity of prepared catalysts. The catalytic testing results demonstrated the performance of hydrotalcite based cobalt catalyst in Fischer-Tropsch synthesis with high selectivity for liquid products. The effect of synthesis method on the activity and selectivity of catalyst was also discussed. Copyright © 2017 BCREC Group. All rights reservedReceived: 3rd November 2016; Revised: 26th February 2017; Accepted: 9th March 2017; Available online: 27th October 2017; Published regularly: December 2017How to Cite: Sharif, M.S., Arslan, M., Iqbal, N., Ahmad, N., Noor, T. (2017). Development of Hydrotalcite Based Cobalt Catalyst by Hydrothermal and Co-precipitation Method for Fischer-Tropsch Synthesis. Bulletin of Chemical Reaction Engineering & Catalysis, 12(3): 357-363 (doi:10.9767/bcrec.12.3.762.357-363)
12
Panurin, Nikita A., Natalya Yu Isaeva, Ekaterina B. Markova, Tatiana F. Sheshko, Alexander G. Cherednechenko, Alena S. Savchenko, Yulia Samoilenko e Garry Z. Kaziev. "Efficiency of using heteropoly compounds of the type (NH4)2[Co(H2O)4]2[Mo8O27]∙6H2O as catalysts for the production of ethylene". Butlerov Communications 60, n. 11 (30 novembre 2019): 85–92. http://dx.doi.org/10.37952/roi-jbc-01/19-60-11-85.
Testo completoAbstract (sommario):
Carrying out heterogeneous acid catalysis with the use of heteropoly compounds has received considerable attention due to the great economic and environmental benefits. In spite of this, its industrial application is limited as there are difficulties in catalyst regeneration (settling) caused by its relatively low thermal stability. The aim of present work was to search and select catalysts related to the class of heteropoly compounds for propane cracking, to test the selectivity of the prosses as well as to discuss possible approaches for solving the problem of catalyst deactivation, that can contribute to achieve stable characteristics of solid heteropoly catalysts. Among these approaches are: the development of new catalysts with high thermal stability, the modification of catalysts to promote coke combustion, the inhibition of coke formation on heteropoly compound catalysts during the process, carrying out the reactions in supercritical media and also the cascade reactions using a multifunctional heteropoly catalyst. The obtained catalyst was also studied by physicochemical methods to get deep knowledge about which features of these compounds influence on the catalytic activity. A highly active and selective catalyst for ammonium octomolybdenocobaltate(II) ammonium (NH4)2[Co(H2O)4]2[Mo8O27]∙6H2O was synthesized for cracking associated petroleum gases. The qualitative, quantitative, and structural composition as well as the specific surface area of the obtained catalyst was established by the methods of X-ray diffraction, X-ray phase and fluorescence analysis. It was revealed that ammonium octomolybdenocobaltate(II) crystallizes in a triclinic syngony with cell parameters: а = 8.6292(9) Å b = 9.4795(10) Å c = 12.2071(13) Å α = 104.326(2)° β = 109.910(2)° γ = 100.820(2)°.
13
Nugrahaningtyas, Khoirina Dwi, Nining Rahmawati, Fitria Rahmawati e Yuniawan Hidayat. "Synthesis And Characterization Of CoMo/Mordenite Catalyst For Hydrotreatment Of Lignin Compound Models". Open Chemistry 17, n. 1 (19 dicembre 2019): 1061–70. http://dx.doi.org/10.1515/chem-2019-0120.
Testo completoAbstract (sommario):
AbstractThe synthesis of CoMo/Mordenite (CoMo/MOR) catalysts was conducted using a co-impregnation method at a various Co/Mo ratios. The produced catalysts were then characterized by X-ray diffraction, total acidity analysis, and scanning electron microscopy. The activity of the catalyst in a hydrotreatment reaction was evaluated by applying the catalyst as a reduced-catalyst to the hydrocracking (HC) reaction of anisole molecules. Analysis of the diffraction data using the Le Bail refinement technique showed that the metal phase was successfully impregnated into the MOR. In addition, increasing the metal content resulted in an increase in the acidity of the catalysts and changed the morphology of the catalysts from homogeneous to heterogeneous with larger particle size. According to the data of GCMS, it is known that the catalysts successfully removed methyl group of anisole molecules. Hydrotreatment reaction with the prepared-catalyst produced 4.77% of phenols. It is 122 % higher than the reaction with MOR catalyst.
14
Cary, Eve Oleta. "Explaining Overheating in China through Institutional Analysis (1992–2010)". Asian Survey 51, n. 3 (1 maggio 2011): 540–58. http://dx.doi.org/10.1525/as.2011.51.3.540.
Testo completoAbstract (sommario):
Economic overheating is a significant and recurring problem in modern China. This paper analyzes the many factors causing overheating and argues that there are systemic and largely structural explanations for overheating that arise from a number of theorized catalysts, including a bureaucratic catalyst and a historical catalyst.
15
Limlamthong, Mutjalin, Nithinart Chitpong e Bunjerd Jongsomjit. "Influence of Phosphoric Acid Modification on Catalytic Properties of γ-χ Al2O3 Catalysts for Dehydration of Ethanol to Diethyl Ether". Bulletin of Chemical Reaction Engineering & Catalysis 14, n. 1 (15 aprile 2019): 1. http://dx.doi.org/10.9767/bcrec.14.1.2436.1-8.
Testo completoAbstract (sommario):
In this present work, diethyl ether, which is currently served as promising alternative fuel for diesel engines, was produced via catalytic dehydration of ethanol over H3PO4-modified g-c Al2O3 catalysts. The impact of H3PO4 addition on catalytic performance and characteristics of catalysts was investigated. While catalytic dehydration of ethanol was performed in a fixed-bed microreactor at the temperature ranging from 200ºC to 400ºC under atmospheric pressure, catalyst characterization was conducted by inductively coupled plasma (ICP), X-ray diffraction (XRD), N2 physisorption, temperature-programmed desorption of ammonia (NH3-TPD) and thermogravimetric (TG) analysis. The results showed that although the H3PO4 addition tended to decrease surface area of catalyst resulting in the reduction of ethanol conversion, the Al2O3 containing 5 wt% of phosphorus (5P/Al2O3) was the most suitable catalyst for the catalytic dehydration of ethanol to diethyl ether since it exhibited the highest catalytic ability regarding diethyl ether yield and the quantity of coke formation as well as it had similar long-term stability to conventional Al2O3 catalyst. The NH3-TPD profiles of catalysts revealed that catalysts containing more weak acidity sites were preferred for dehydration of ethanol into diethyl ether and the adequate promotion of H3PO4 would lower the amount of medium surface acidity with increasing catalyst weak surface acidity. Nevertheless, when the excessive amount of H3PO4 was introduced, it caused the destruction of catalysts structure, which resulted in the catalyst incapability due to the decrease in active surface area and pore enlargement. Copyright © 2019 BCREC Group. All rights reservedReceived: 28th March 2018; Revised: 7th August 2018; Accepted: 15th August 2018; Available online: 25th January 2019; Published regularly: April 2019How to Cite: Limlamthong, M., Chitpong, N., Jongsomjit, B. (2019). Influence of Phosphoric Acid Modification on Catalytic Properties of g-c Al2O3 Catalysts for Dehydration of Ethanol to Diethyl Ether. Bulletin of Chemical Reaction Engineering & Catalysis, 14 (1): 1-8 (doi:10.9767/bcrec.14.1.2436.1-8)Permalink/DOI: https://doi.org/10.9767/bcrec.14.1.2436.1-8
16
Ma, Yubo, Zhixian Gao, Tao Yuan e Tianfu Wang. "Kinetics of Dicyclopentadiene Hydroformylation over Rh–SiO2 Catalysts". Progress in Reaction Kinetics and Mechanism 42, n. 2 (maggio 2017): 191–99. http://dx.doi.org/10.3184/146867817x14821527549013.
Testo completoAbstract (sommario):
The hydroformylation of dicyclopentadiene (DCPD) to monoformyltricyclodecenes (MFTD) represents a key intermediate step in the conversion of the C5 fraction derived from the petrochemical process to value-added fine chemicals, for example, diformyltricyclodecanes and tricyclodecanedimethylol. Although both heterogeneous and homogeneous catalysts can catalyse this reaction, the heterogeneously catalysed pathway has received significantly less attention due to its lower catalytic activities. We demonstrate in this work that a low Rh loaded heterogeneous 0.1% Rh–SiO2 catalyst can present a similar performance relative to the homogeneous Rh(PPh3)Cl, a reference catalyst for this reaction. Furthermore, an extensive kinetic study of DCPD hydroformylation to MFTD using heterogeneous 0.1% Rh–SiO2 catalysts has been performed. A series of kinetic experiments was carried out over a broad range of conditions (temperature: 100–120 °C; pressure: 1.5–5 MPa; catalyst-to-reactant mass ratio: 0.02–0.05; PPh3 concentration: 5–12.5 g L−1). A kinetic analysis was carried out, indicating the activation energy for the reaction to be 84.7 kJ mol−1. DCPD conversion and MFTD yield could be optimised to be as high as 99% at 0.1% Rh loading, a DCPD/catalyst mass ratio of 25, a PPh3 concentration of 10 g L−1, a reaction time of 4 h and a reaction pressure of 4 MPa.
17
Xiao, Tiancun, Tara Shirvani, Oliver Inderwildi, Sergio Gonzalez-Cortes, Hamid AlMegren, David King e Peter P. Edwards. "The Catalyst Selectivity Index (CSI): A Framework and Metric to Assess the Impact of Catalyst Efficiency Enhancements upon Energy and CO2 Footprints". Topics in Catalysis 58, n. 10-11 (2 luglio 2015): 682–95. http://dx.doi.org/10.1007/s11244-015-0401-1.
Testo completoAbstract (sommario):
AbstractHeterogeneous catalysts are not only a venerable part of our chemical and industrial heritage, but they also occupy a pivotal, central role in the advancement of modern chemistry, chemical processes and chemical technologies. The broad field of catalysis has also emerged as a critical, enabling science and technology in the modern development of “Green Chemistry”, with the avowed aim of achieving green and sustainable processes. Thus a widely utilized metric, the environmental E factor—characterizing the waste-to-product ratio for a chemical industrial process—permits one to assess the potential deleterious environmental impact of an entire chemical process in terms of excessive solvent usage. As the many (and entirely reasonable) societal pressures grow, requiring chemists and chemical engineers not only to develop manufacturing processes using new sources of energy, but also to decrease the energy/carbon footprint of existing chemical processes, these issues become ever more pressing. On that road to a green and more sustainable future for chemistry and energy, we note that, as far as we are aware, little effort has been directed towards a direct evaluation of the quantitative impacts that advances or improvements in a catalyst’s performance or efficiency would have on the overall energy or carbon (CO2) footprint balance and corresponding greenhouse gas (GHG) emissions of chemical processes and manufacturing technologies. Therefore, this present research was motivated by the premise that the sustainability impact of advances in catalysis science and technology, especially heterogeneous catalysis—the core of large-scale manufacturing processes—must move from a qualitative to a more quantitative form of assessment. This, then, is the exciting challenge of developing a new paradigm for catalysis science which embodies—in a truly quantitative form—its impact on sustainability in chemical, industrial processes. Towards that goal, we present here the concept, definition, design and development of what we term the Catalyst Sensitivity Index (CSI) to provide a measurable index as to how efficiency or performance enhancements of a heterogeneous catalyst will directly impact upon the fossil energy consumption and GHG emissions balance across several prototypical fuel production and conversion technologies, e.g. hydrocarbon fuels synthesized using algae-to-biodiesel, algae-to-jet biofuel, coal-to-liquid and gas-to-liquid processes, together with fuel upgrading processes using fluidized catalytic cracking of heavy oil, hydrocracking of heavy oil and also the production of hydrogen from steam methane reforming. Traditionally, the performance of a catalyst is defined by a combination of its activity or efficiency (its turnover frequency), its selectivity and stability (its turnover number), all of which are direct manifestations of the intrinsic physicochemical properties of the heterogeneous catalyst itself under specific working conditions. We will, of course, retain these definitions of the catalytic process, but now attempt to place discussions about a catalyst’s performance onto a new foundation by investigating the effect of improvements in the catalyst’s efficiency or performance on the resulting total energy and total CO2 footprint for these prototypical fuel production and fuel conversion processes. The CSI should help the academic and industrial chemical communities, not only to highlight the current ‘best practice catalysts’, but also draw specific conclusions as to what energy and CO2 emissions saving one could anticipate with higher efficiency/higher performance from heterogeneous catalysts in a particular fuel synthesis or conversion process or technology. Our aim is to place discussions about advances in the science and technology of catalysis onto a firm foundation in the context of GHG emissions. We believe that thinking about (and attempting to quantify) total energy and CO2 emissions reductions associated with advances in catalysis science from a complete energy life cycle analysis perspective is extremely important. The CSI will help identify processes where the most critical advances in catalyst efficiency are needed in terms of their potential impact in the transition to a more sustainable future for fuel production and conversion technologies.
18
Gould, S. A. C., e M. L. Occelli. "Analysis of fluidized cracking catalysts by Atomic Force Microscopy". Proceedings, annual meeting, Electron Microscopy Society of America 53 (13 agosto 1995): 424–25. http://dx.doi.org/10.1017/s042482010013849x.
Testo completoAbstract (sommario):
In the United States, five million barrels of oil per day or one third of all processed crude oil is catalytically converted with fluidized catalysts, a process which requires 500 tons of catalyst daily. Given these immense quantities, a small percentage difference in the efficiency of the oil conversion to liquid fuel can result in a savings of many millions of barrels of oil annually. In this study we have used a contact mode atomic force microscope (AFM) to study to topography of a set of fluidized cracking catalysts (FCC) from the μm level down to the atomic. We selected this technique because it is believed that the cracking in the FCCs occurs mainly on the catalysts top 10-15 μm suggesting a surface which contains numerous pores, something the AFM can well characterize.We obtained our FCC (GRZ-1) from Davison. The FCC is generated so that it contains and estimated 35% rare earth exchaged zeolite Y, 50% kaolin and 15% binder.
19
Kumakura, Makoto, Hoshimitsu Kiribayashi, Takahiro Saida, Shigeya Naritsuka e Takahiro Maruyama. "In situ XANES Analysis of Co and Ni Catalysts during Single-Walled Carbon Nanotube Growth". MRS Advances 3, n. 1-2 (2018): 13–18. http://dx.doi.org/10.1557/adv.2017.636.
Testo completoAbstract (sommario):
ABSTRACTIn situ X-ray absorption near edge structure (XANES) measurements were conducted to elucidate the chemical states of Co and Ni catalysts during single-walled carbon nanotube (SWCNT) growth via chemical vapor deposition (CVD). XANES spectra indicated that both Co and Ni catalysts partially oxidized before heating. It was found that Co catalysts formed carbides during the SWCNT growth. In contrast, Ni catalysts remained metallic state even after the SWCNT growth had begun. These results indicate that during SWCNT growth, carbon atoms dissolve into Co particles, whereas for Ni particles, they diffuse on the surface region. It was concluded that the growth mechanisms of SWCNTs formed by CVD differed for either Co or Ni catalyst.
20
Kang, Myung Jong, e Young Soo Kang. "Efficient Approaches on Photochemical CO2 Reduction to Alcohol by Solar Light with Functional Multi-layered Membrane Catalysts". MRS Advances 3, n. 55 (2018): 3271–80. http://dx.doi.org/10.1557/adv.2018.418.
Testo completoAbstract (sommario):
ABSTRACTSimple and efficient approach for artificial photosynthesis of CO2 reduction into ethanol with flexible functional multi-layered membrane catalysts is suggested. The g-C3N4 and BiVO4 particle were synthesized by self-condensation and hydrothermal method. g-C3N4 membrane catalyst and g-C3N4/BiVO4 layered membrane catalyst were fabricated by casting and shaping of Nafion polymer mixture. XRD, FT-IR and XPS analyses proved that the intrinsic properties of g-C3N4 and BiVO4 were maintained after fabricating flexible functional multi-layered membrane catalyst. The interfacial contact between g-C3N4 and BiVO4 particles in flexible membrane catalyst for efficient transport of photogenerated electron was revealed by TEM and photoelectrochemical analysis. Finally, photochemical CO2 reduction reaction was performed with flexible functional multi-layered membrane catalysts. The g-C3N4 membrane catalysts produced 147 μM of ethanol during 12 hrs of CO2 reduction reaction while the g-C3N4/BiVO4 layered membrane catalysts produced 256 μM of ethanol during 12 hrs of CO2 reduction reaction. This is due to the higher solar light harvesting and efficient hole-charge separation from functional multi-layered BiVO4 membrane catalyst leading to the higher electron transport rate to g-C3N4 membrane catalysts, promoting the CO2 reduction reaction on the surface of g-C3N4 membrane catalyst.
21
Sanaa Tareq, Sarhan, Mohd Izham Saiman, Taufiq-Yap Yun Hin, Abdul Halim Abdullah e Umer Rashid. "The Impact of Hydrogen Peroxide as An Oxidant for Solvent-free Liquid Phase Oxidation of Benzyl Alcohol using Au-Pd Supported Carbon and Titanium Catalysts". Bulletin of Chemical Reaction Engineering & Catalysis 13, n. 2 (11 giugno 2018): 373. http://dx.doi.org/10.9767/bcrec.13.2.1204.373-385.
Testo completoAbstract (sommario):
The solvent free oxidation of benzyl alcohol was conducted employing Au and Pd supported catalysts, while utilizing hydrogen peroxide 35% (H2O2) as the oxidant, H2O2 is very cheap, mild, and an environment friendly reagent, which produced water as the only by-product. Various proportions of Au-Pd catalysts on carbon and titanium oxide activated as supports were synthesized through the use of sol immobilization catalyst synthesis technique. Characterization of the synthesized catalysts was performed using X-Ray Diffraction (XRD), Brunauer-Emmett-Teller (BET), Field Emission Scanning Electron Microscopy (FESEM), and Transmission Electron Microscopy (TEM). It was found that the synthesized Au-Pd/ activated carbon catalyst was beneficial for the solvent free oxidation of benzyl alcohol after its containing high surface area measuring 871 m2g-1. Analysis of the TEM data and particle dimension revealed smaller and narrower particle size of 1 wt%. Thus, the distribution of Au-Pd/C was attained. Carbon-supported bimetallic catalysts presented a higher conversion compared to catalysts that are supported titanium oxide (TiO2) for for the oxidation reaction of benzyl alcohol. It was determined that this technique was a suitable process for catalyst synthesis with high selectivity, same distribution of the particle size and activations. Copyright © 2018 BCREC Group. All rights reservedReceived: 8th May 2017; Revised: 22nd February 2018; Accepted: 6th March 2018; Available online: 11st June 2018; Published regularly: 1st August 2018How to Cite: Sanaa Tareq, S., Saiman, M.I., Yun Hin, T.Y., Abdullah, A.H., Rashid, U. (2018). The Impact of Hydrogen Peroxide as An Oxidant for Solvent-free Liquid Phase Oxidation of Benzyl Alcohol using Au-Pd Supported Carbon and Titanium Catalysts. Bulletin of Chemical Reaction Engineering & Catalysis, 13 (2): 373-385 (doi:10.9767/bcrec.13.2.1204.373-385)
22
Li, Boyu, Abhishek Raj, Eric Croiset e John Z. Wen. "Reactive Fe-O-Ce Sites in Ceria Catalysts for Soot Oxidation". Catalysts 9, n. 10 (28 settembre 2019): 815. http://dx.doi.org/10.3390/catal9100815.
Testo completoAbstract (sommario):
This study investigates the role of oxygen vacancy on Fe-doped CeO2 catalyst activity for soot oxidation. The oxygen vacancy was assessed through Ce3+ content. The Fe content was varied between 0 and 30% for two catalyst preparation methods, co-precipitation (CP) and solution combustion synthesis (SCS). X-ray photoelectron spectroscopy indicates that ceria exists as both Ce4+ and Ce3+, while iron is present only as Fe3+. The catalyst’s activity was evaluated by ignition (T10) and combustion (T50) temperatures using thermogravimetric analysis. Optimum Fe contents yielding the highest activity were found to be 10% and 5% for CP and SCS catalysts, respectively. The surface area and morphology showed a moderate effect on catalyst activity, because catalytic soot oxidation involves solid–solid contact. More importantly, regardless of the fabrication method, it was found that Ce3+ content, which is closely related to oxygen vacancies, plays the most important role in affecting the catalyst activity.
23
Susanto, Bambang Heru, e Joshua Raymond Valentino Siallagan. "Analysis of NiMoP/γ-Al2O3 Catalyst Preparation with Impregnation and Microwave Polyol Methods for Bio-Jet Production". Materials Science Forum 1000 (luglio 2020): 257–64. http://dx.doi.org/10.4028/www.scientific.net/msf.1000.257.
Testo completoAbstract (sommario):
Bio-Jet could be produced by the synthesis of vegetable oil through the hydrodeoxygenation, decarboxylation, decarbonization, and catalytic cracking process. Physical characteristics, activities, and selectivity of the catalyst used will determine the rate, conversion, and yield of the reaction that being carried out. This study aims to compare and obtain the best characteristics of NiMoP/γ-Al2O3 catalysts synthesized using two types of preparation, impregnation and microwave polyol methods, which will be used for bio-jet production. The impregnation method takes more than 24 hours for catalyst preparation, while microwave polyols that use microwaves can synthesize catalysts faster. Both catalysts have almost the same loading on the weight of the catalyst, which in the microwave polyol method has a more dispersed promotor and active site, although the crystallinity level is deficient and tends to be amorphous compared to the impregnation method with high crystallinity. In bio-jet synthesis reaction with operating conditions of 5% catalyst loading by comparison to Coconut Oil, 400°C, and 15 bar, the conversion, yield, and selectivity of catalyst impregnation were 91.705%, 47.639%, and 84.511%, while microwave polyol catalysts were 90.296%, 42.752%, and 82.517%, respectively. In conclusion, microwave polyol provides a more effective and efficient preparation method.
24
Kumaran, P., S. Mohanamurugan, P. Shankar, R. Vijay e R. Narayanan. "Experimental Analysis of Different Packed Bed Catalysts for Lean NOx Traps (LNT)". Applied Mechanics and Materials 787 (agosto 2015): 677–81. http://dx.doi.org/10.4028/www.scientific.net/amm.787.677.
Testo completoAbstract (sommario):
In LNT Catalysts, oxidizing agents are added for reducing the levels of NOxemission. In the current work three sets of LNT catalysts were prepared by dipping them in three independent solutions containing i) Barium nitrate, ii) Copper nitrate + Silver nitrate, iii) Copper nitrate + Ferric nitrate + Barium nitrate. These three catalysts were then tested in dual-cylinder four-stroke Simpson 217 DI Diesel engine coupled to electrical dynamometer with wire wound resistance loading device. LNT process was studied and performance of the various chemicals used to reduce the NOx emission under various load conditions in lean burn engine was evaluated. 60% NOx conversion was obtained for LNT catalyst coated with barium + copper +ferric nitrate.
25
Suprapto, Suprapto, Tikha Reskiani Fauziah, Meiske S. Sangi, Titie Prapti Oetami, Imroatul Qoniah e Didik Prasetyoko. "Calcium Oxide from Limestone as Solid Base Catalyst in Transesterification of Reutealis trisperma Oil". Indonesian Journal of Chemistry 16, n. 2 (13 marzo 2018): 208. http://dx.doi.org/10.22146/ijc.21165.
Testo completoAbstract (sommario):
CaO catalysts were synthesized from limestone by thermal decomposition and coprecipitation methods. The CaO and MgO reference catalysts were also synthesized for comparison. The catalysts were characterized by X-ray diffractometer (XRD) and the analysis result was refined by Rietica software. CaO catalyst obtained by coprecipitation method has higher purity of CaO and lower MgO content than those of calcined CaO. The catalysts were also characterized by Fourier Transform Infrared (FTIR) spectroscopy. FTIR spectra showed that the catalysts can be easily hydrated and carbonated in air. The catalytic activity of the catalyst was studied in transesterification reaction of Reutealis trisperma (Kemiri Sunan) oil with methanol. Transesterification reaction was carried out at oil to methanol molar ratio 1:1 and 1% of catalyst at 60 °C for 2 h. Catalytic activity of CaO catalyst obtained by coprecipitation was higher than calcined CaO. The methyl ester yield obtained from synthesized CaO, CaO from coprecipitation, calcined CaO, and synthesized MgO catalysts were 56.13; 37.74; 15.97; and 3.61%, respectively.
26
Sarosh, A., A. Hussain, E. Pervaiz e M. Ahsan. "Computational Fluid Dynamics (CFD) Analysis of Phthalic Anhydride’s Yield Using Lab Synthesized and Commercially Available (V2O5/TiO2) Catalyst". Engineering, Technology & Applied Science Research 8, n. 2 (19 aprile 2018): 2821–26. http://dx.doi.org/10.48084/etasr.1954.
Testo completoAbstract (sommario):
V2O5/TiO2 is an important catalyst used in many industrial reactions like selective oxidation of o-xylene to phthalic anhydride, selective catalytic reduction of NOx, selective oxidation of alkanes, etc. The partial oxidation of o-xylene to synthesize phthalic anhydride is an exothermic reaction and leaves hot spots on the catalyst’s surface. The yield of phthalic anhydride strongly depends on the activity and stability of the catalyst. In this work, a computational fluid dynamics (CFD) analysis has been conducted to compare the yield of lab prepared catalyst with the commercially used catalyst. This work is first attempt to simulate V2O5/TiO2 catalyst for cracking heavy hydrocarbons in the petrochemical industry using k- ε turbulence and species transport models in CFD. The results obtained are in the form of scaled residuals, area-weighted average, and contours of pressure and temperature. Simulation results of lab synthesized and commercially used catalysts, applying finite volume method (FVM) are compared, which emphasize the scope of CFD modeling in the catalytic cracking process of petrochemical industry.
27
Mohd Zabidi, Noor Asmawati, Tuan Syahylah Tuan Sulong e Sardar Ali. "Synthesis and Characterization of Cu/ZnO Catalyst on Carbon Nanotubes and Al2O3 Supports". Materials Science Forum 916 (marzo 2018): 139–43. http://dx.doi.org/10.4028/www.scientific.net/msf.916.139.
Testo completoAbstract (sommario):
CO2 conversion into valuable chemicals is an attractive option to deal with the increasing CO2 concentration in the atmosphere. In this study, Cu/ZnO catalyst was synthesized on multi-walled carbon nanotubes (MWCNTs) and Al2O3 supports via incipient wetness impregnation method. The physicochemical properties of the catalysts were investigated using TEM, XRD, N2 adsorption-desorption analysis, H2-TPR and XPS. The performance of the synthesized catalysts in a CO2 hydrogenation reaction was evaluated in a fixed-bed reactor at 503 K, 22.5 bar and H2:CO2 ratio of 3:1. TEM images showed that Cu/ZnO nanoparticles were deposited inside the CNTs as well as on the exterior walls of the CNTs. The average CuO crystallite size on Al2O3 and CNTs supports was 15.7 and 11 nm, repectively. Results of H2-TPR studies showed that the reducibility of the catalyst was improved on the CNTs support. XPS analysis confirmed the presence of Cu2+ in the samples, however, the binding energy of Cu 2p3/2 peak on the Al2O3 support was shifted to higher value compared to that of CNTs support. Products obtained from the CO2 hydrogenation reaction in the presence of these catalyts were methanol, ethanol, methyl formate and methane. The CO2 conversion of around 23% was obtained using both types of catalysts, however, Cu/ZnO on CNTs resulted in higher yield of methyl formate compared to that of Al2O3-supported catalyst.
28
Lindner, J., A. Sachdev, M. A. Villa-Garcia e J. Schwank. "A high resolution and Analytical Electron Microscopy study of novel solid state hydrodesulfurization catalysts". Proceedings, annual meeting, Electron Microscopy Society of America 47 (6 agosto 1989): 264–65. http://dx.doi.org/10.1017/s0424820100153294.
Testo completoAbstract (sommario):
The removal of sulfur from petroleum feedstocks is of great importance to the oil industry. The process, known as hydrodesulfurization (HDS), is typically catalyzed by Group VIB metal oxides. The workhorse of the industry today is an alumina supported CoO-MoO3 catalyst. Recently, several models have been proposed for the active site responsible for HDS activity, but despite extensive research efforts there is still no clear relationship between structure and activity. We have prepared promoted and non-stoichiometric catalyst samples via a novel solid state synthesis route. These catalysts are not only quite active in the HDS of thiophene, but are also more thermally stable and consequently easier to characterize than the standard HDS materials prepared by wet chemistry methods. Most studies on HDS catalysts rely on bulk techniques for characterization analysis, however, these do not provide any information at the microscopic level where catalysis occurs. For that reason we have used analytical and high resolution electron microscopy to obtain information at the atomic level, coupled with bulk techniques such as x-ray diffraction and surface area measurements. The objective was to develop a link between the microstructure of our solid state catalysts and their HDS activity.
29
Vostrikova, N. M., E. D. Kravtsova e Y. V. Vostrikova. "Analysis of the Engineering Process of Reforming Dead Catalysts for the Extraction of Platinum Group Metals". Materials Science Forum 989 (maggio 2020): 468–73. http://dx.doi.org/10.4028/www.scientific.net/msf.989.468.
Testo completoAbstract (sommario):
The analysis of the engineering process of reforming dead catalysts for the extraction of platinum group metals has been carried out. Fully-dead catalyst, having passed several cycles of regeneration and entitled to utilization, has the considerable carbonaceous deposits, both on external and internal surfaces. Their content averages 5.0% of the mass of the catalyst. The research objectively consisted in selection of the sweet roasting modes, promoting the fullest removal of the dense carbonaceous deposits from the surface of the dead platinum-rhenium catalysts. The kinetics research of carbonaceous removal deposits from the surface of the catalyst was carried out in a pipe-still heater; oxygen content, duration and temperature of sweet roasting being varied. The maximum temperature during the research reached 950°C, the maximum duration of isothermal holding didn't exceed 6 hours. The extent of carbonaceous deposits removal was calculated by changing sample weight. The kinetic curves were approximated by high-order polynomials, which made it possible to obtain a diagram, illustrating the degree of organic deposits removal, depending on temperature and firing time. It is shown that in the environment enriched to 30-35 vol. % oxygen, the engineering process of catalysts for regeneration is possible to be carried out at 650 °C, with holding for 2 hours at a specified temperature. The alternative of sweet roasting is the air blowing of dead catalysts at temperature of 800 °C within an hour. Both modes guarantee the complete removal of the dense carbonaceous deposits from the surface of the dead catalyst.
30
Abedin, Md Ashraful, Swarom Kanitkar, Nitin Kumar, Zi Wang, Kunlun Ding, Graham Hutchings e James J. Spivey. "Probing the Surface Acidity of Supported Aluminum Bromide Catalysts". Catalysts 10, n. 8 (3 agosto 2020): 869. http://dx.doi.org/10.3390/catal10080869.
Testo completoAbstract (sommario):
Solid acid catalysis is an important class of reactions. The principal advantages of solid acid catalysts as compared to their corresponding fluid acids include minimal waste and ease of product separation. One type of these catalysts is based on aluminum bromide (Al2Br6), which is a stronger Lewis acid than Al2Cl6. In this report, Al2Br6 is grafted on commercial mesoporous silica (CMS), SBA-15 and silica gel to create a solid catalyst similar to the silica-supported Al2Cl6 superacid. These supported Al2Br6 catalysts were characterized by NH3-Temperature Programmed Desorption (TPD), pyridine Diffuse Reflectance for Infrared Fourier Transform Spectroscopy (DRIFTS) and Magic Angle Spinning Nuclear Magnetic Resonance (MAS NMR). Formation of acid sites was confirmed and quantified with NH3-TPD. Both Lewis and Brønsted sites were observed with DRIFTS using pyridine as a probe molecule. In addition, thermal stability of acid sites was also studied using DRIFTS. 27Al MAS NMR analysis showed tetrahedral, pentahedral and octahedral co-ordination of Al, confirming that Al2Br6 reacted with –OH groups on silica surface. Performance of these catalysts was evaluated using acid-catalyzed 1-butene isomerization. Conversion above 80% was observed at 200 °C, corresponding to thermodynamic equilibrium.
31
Rosário, Roberta Lopes do, Ronaldo Costa Santos, Alan Silva dos Santos, Alexandre Carvalho, Sylvette Brunet e Luiz Antônio Magalhães Pontes. "Niobium oxide (Nb2O5) as support for CoMo and NiW catalysts in the hydrodesulfurization reaction of 3-methylthiophene". Research, Society and Development 9, n. 11 (2 dicembre 2020): e74391110307. http://dx.doi.org/10.33448/rsd-v9i11.10307.
Testo completoAbstract (sommario):
The efficiency of niobium oxide as catalytic support of hydrodesulfurization (HDS) catalysts (CoMo and NiW) has been investigated in the HDS of a model molecule representative of sulfur compounds present in FCC gasoline (3-methylthiophene: 3MT). The NiW catalyst presented higher catalytic activity than CoMo calcined and non-calcined catalyst, however a better ratio pentane/pentene has been achieved by CoMo catalysts, which implies a lower formation of hydrogenated products. Indeed, the activity order for the catalysts evaluated is: NiW/Nb2O5 > CoMo/Nb2O5 calcined support > CoMo/Nb2O5 non-calcined support, despite the ratio pentane/pentene which has the inverse order. Furthermore, textural and chemical characterization techniques have been performed. From NH3-TPD analysis it was observed an acidity profile with a predominance of weak/strong and weak/moderate acid for CoMo and NiW catalysts, respectively. Meanwhile, the BET analysis has shown a low specific surface area for the catalysts supported by niobium oxide. Concerning the structure characteristic, the XRD analysis has suggested an amorphous phase in all catalysts analyzed.
32
Shtyka, O., Z. Dimitrova, R. Ciesielski, A. Kedziora, G. Mitukiewicz, J. Leyko, W. Maniukewicz, A. Czylkowska e T. Maniecki. "Steam reforming of ethanol for hydrogen production: influence of catalyst composition (Ni/Al2O3, Ni/Al2O3–CeO2, Ni/Al2O3–ZnO) and process conditions". Reaction Kinetics, Mechanisms and Catalysis 132, n. 2 (4 marzo 2021): 907–19. http://dx.doi.org/10.1007/s11144-021-01945-6.
Testo completoAbstract (sommario):
AbstractEthanol steam reforming was studied over Ni supported catalysts. The effects of support (Al2O3, Al2O3–ZnO, and Al2O3–CeO2), metal loading, catalyst activation method, and steam-to-ethanol molar feed ratio were investigated. The properties of catalysts were studied by N2 physisorption, TPD-CO2, X-ray diffraction, and temperature programmed reduction. After activity tests, the catalysts were analyzed by TOC analysis. The catalytic activity measurements showed that the addition either of ZnO SSor CeO2 to alumina enhances both ethanol conversion and promotes selectivity towards hydrogen formation. The same effects were observed for catalysts with higher metal loadings. High process temperature and high water-to-ethanol ratio were found to be beneficial for hydrogen production. An extended catalyst stability tests showed no loss of activity over 50 h on reaction stream. The TOC analysis of spent catalysts revealed only insignificant amounts of carbon deposit.
33
Akinlolu, Kayode, Bamgboye Omolara, Tripathi Shailendra, Akinsiku Abimbola e Ogunniran Kehinde. "Synthesis, characterization and catalytic activity of partially substituted La1−xBaxCoO3 (x ≥ 0.1 ≤ 0.4) nano catalysts for potential soot oxidation in diesel particulate filters in diesel engines". International Review of Applied Sciences and Engineering 11, n. 1 (aprile 2020): 52–57. http://dx.doi.org/10.1556/1848.2020.00007.
Testo completoAbstract (sommario):
AbstractThe sol gel method was used in preparing a series of A site partially substituted La1−xBaxCoO3 (x ≥ 0.1 ≤ 0.4) perovskite catalysts coded LBC1, 2, 3, and 4 and their potential as catalysts for soot oxidation were evaluated. The Brunauer–Emmett–Teller (BET), Inductively Coupled Plasma Atomic Emission Spectroscopy (ICPAES), Thermogravimetric/Differential Thermal Analysis (TGA/DTG), X-ray analysis (XRD) were used in characterizing the prepared perovskite catalyst. The result shows that at (x≥ 0.2 ≤ 0.4), there was an increase in surface area when we compare it with that of x = 0. The increase in surface area helps in increasing the catalytic performance of the catalyst. Also, when evaluating the catalytic performance of the synthesized catalysts, it was observed that doping the perovskite catalysts helped in the general improvement of the catalytic performance for soot oxidation. The best performance in this research study with a T50 of 484 °C was observed at x = 0.2 catalyst (LBC2). This shows that the non-noble perovskite catalysts prepared in this research study has the potential to replace the noble metal based catalysts used presently in the diesel automotive industry.
34
Bateni, Hamed, e Chad Able. "Development of Heterogeneous Catalysts for Dehydration of Methanol to Dimethyl Ether: a Review". Kataliz v promyshlennosti 18, n. 4 (23 luglio 2018): 6–30. http://dx.doi.org/10.18412/1816-0387-2018-4-6-30.
Testo completoAbstract (sommario):
Dimethyl ether (DME) is a promising multisource and multipurpose clean fuel and value-added chemical synthesized from syngas. This process can be either performed in a single stage (direct process) using a dual catalysis system or a two stage (indirect process) where syngas is first converted into methanol and then dehydrated to produce DME. While the dehydration reaction has been studied extensively over multiple decades, to date no review has been conducted on the catalysts involved in the methanol dehydration reaction. This work demonstrates the state of the art in catalyst preparation and analysis for this application. The dominant catalysts are studied extensively in this work, including γ-Al2O3and various zeolites, such as ZSM-5, Y, beta and mordenite as well as their relevant modifications. Additionally, silicaalumina, mesoporous silicates, aluminum phosphate, silicoaluminophosphates, heteropoly acids (HPAs), metal oxides, ion exchange resins and quasicrystals are discussed in this work, owing to the wide variety of catalysts available and studied for the purposes of methanol dehydration to DME.
35
LIU, JINGYUE. "Nanometer-resolution Auger electron spectroscopy and microscopy of small particles". Proceedings, annual meeting, Electron Microscopy Society of America 51 (1 agosto 1993): 720–21. http://dx.doi.org/10.1017/s042482010014943x.
Testo completoAbstract (sommario):
Small metal particles have peculiar physical and chemical properties and they are especially important in catalysis. A detailed understanding of catalytic processes requires knowledge of both the microstructure and the microchemistry of the catalyst system. Although nanometer scale surface topography of supported catalysts can be studied with secondary electron (SE) signals, a chemically specific and surface sensitive signal such as Auger electrons must be used to extract compositional information about the surface species. Auger electron (AE) spectroscopy (AES) and scanning Auger microscopy (SAM) have been widely used for surface and catalyst characterization. In order to observe the active phases (small particles) of supported catalysts, it is necessary, however, to have nanometer scale resolution in SAM images.With significant improvement in detection efficiency of low energy secondary electrons by employing magnetic parallelizers in our UHV scanning transmission electron microscope (STEM), known as MIDAS (a Microscope for Imaging, Diffraction and Analysis of Surfaces), a spatial resolution of approximately 3 nm in SAM images has been achieved on bulk samples.
36
Howe, Alexander G. R., Rhodri Maunder, David J. Morgan e Jennifer K. Edwards. "Rapid Microwave-Assisted Polyol Synthesis of TiO2-Supported Ruthenium Catalysts for Levulinic Acid Hydrogenation". Catalysts 9, n. 9 (5 settembre 2019): 748. http://dx.doi.org/10.3390/catal9090748.
Testo completoAbstract (sommario):
One wt% Ru/TiO2 catalysts prepared by a one-pot microwave-assisted polyol method have been shown to be highly active for Levulinic acid hydrogenation to γ-Valerolactone. Preparation temperature, microwave irradiation time and choice of Ru precursor were found to have a significant effect on catalyst activity. In the case of Ru(acac)3-derived catalysts, increasing temperature and longer irradiation times increased catalyst activity to a maximum LA conversion of 69%. Conversely, for catalysts prepared using RuCl3, shorter preparation times and lower temperatures yielded more active catalysts, with a maximum LA conversion of 67%. Catalysts prepared using either precursor were found to contain highly dispersed nanoparticles <3 nm in diameter. XPS analysis of the most and least active catalysts shows that the catalyst surface is covered in a layer of insoluble carbon with surface concentrations exceeding 40% in some cases. This can be attributed to the formation of large condensation oligomers from the reaction between the solvent, ethylene glycol and its oxidation products, as evidenced by the presence of C-O and C = O functionality on the catalyst surface.
37
Al-asadi, Mohammed, e Norbert Miskolczi. "High Temperature Pyrolysis of Municipal Plastic Waste Using Me/Ni/ZSM-5 Catalysts: The Effect of Metal/Nickel Ratio". Energies 13, n. 5 (10 marzo 2020): 1284. http://dx.doi.org/10.3390/en13051284.
Testo completoAbstract (sommario):
This work is dedicated to the high temperature pyrolysis of municipal plastic waste using Me/Ni/ZSM-5 catalysts. Catalysts were synthetized by wet impregnation. In addition to nickel, synthetic zeolite catalysts contain calcium, ceria, lanthanum, magnesia or manganese. Catalysts were prepared and tested using 0.1, 0.5 and 2.0 Me/Ni ratios. Catalyst morphology was investigated by SEM and surface analysis. Higher concentrations of second metals can block catalyst pore channels due to the more coke formation, which leads to smaller surface area. Furthermore, the chemicals used for the impregnation were among the catalyst grains, especially in case of 2.0 Me/Ni ratios. For pyrolysis, a horizontal tubular furnace reactor was used at 700 °C. The highest hydrogen and syngas yields were observed using ceria- and lanthanum-covered catalysts. The maximum production of syngas and hydrogen (69.8 and 49.2 mmol/g raw material) was found in the presence of Ce/Ni/ZSM-5 catalyst with a 0.5 Me/Ni ratio.
38
Chomboon, Tanakit, Weerit Kumsung, Metta Chareonpanich, Selim Senkan e Anusorn Seubsai. "Chromium-Ruthenium Oxides Supported on Gamma-Alumina as an Alternative Catalyst for Partial Combustion of Methane". Catalysts 9, n. 4 (4 aprile 2019): 335. http://dx.doi.org/10.3390/catal9040335.
Testo completoAbstract (sommario):
Catalyst screening of γ-Al2O3-supported, single-metal and bimetallic catalysts revealed several bimetallic catalysts with activities for partial combustion of methane greater than a benchmark Pt/γ-Al2O3 catalyst. A cost analysis of those catalysts identified that the (2 wt%Cr + 3 wt% Ru)/γ-Al2O3 catalyst, denoted as 2Cr3Ru/Al2O3, was about 17.6 times cheaper than the benchmark catalyst and achieved a methane conversion of 10.50% or 1.6 times higher than the benchmark catalyst based on identical catalyst weights. In addition, various catalyst characterization techniques were performed to determine the physicochemical properties of the catalysts, revealing that the particle size of RuO2 became smaller and the binding energy of Ru 3d also shifted toward a lower energy. Moreover, the operating conditions (reactor temperature and O2/CH4 ratio), stability, and reusability of the 2Cr3Ru/Al2O3 catalyst were investigated. The stability test of the catalyst over 24 h was very good, without any signs of coke deposition. The reusability of the catalyst for five cycles (6 h for each cycle) was noticeably excellent.
39
Ledakowicz, Stanisław, Lech Nowicki, Jerzy Petera, Jarosław Nizioł, Paweł Kowalik e Andrzej Gołębiowski. "KINETIC CHARACTERISATION OF CATALYSTS FOR METHANOL SYNTHESIS". Chemical and Process Engineering 34, n. 4 (1 dicembre 2013): 497–506. http://dx.doi.org/10.2478/cpe-2013-0040.
Testo completoAbstract (sommario):
Abstract The results of activity studies of four catalysts in methanol synthesis have been presented. A standard industrial catalyst TMC-3/1 was compared with two methanol catalysts promoted by the addition of magnesium and one promoted by zirconium. The kinetic analysis of the experimental results shows that the Cu/Zn/Al/Mg/1 catalyst was the least active. Although TMC-3/1 and Cu/Zn/Al/Mg/2 catalysts were characterised by a higher activity, the most active catalyst system was Cu/Zn/Al/Zr. The activity calculated for zirconium doped catalyst under operating conditions was approximately 30% higher that of TMC-3/1catalyst. The experimental data were used to identify the rate equations of two types - one purely empirical power rate equation and the other one - the Vanden Bussche & Froment kinetic model of methanol synthesis. The Cu/ZnO/Al2O3 catalyst modified with zirconium has the highest application potential in methanol synthesis.
40
Santoso, Aman, Ida Bagus S. Sumari, Novia Nina Safitri, Anugrah Ricky Wijaya e Daratu Eviana Kusuma Putri. "Activation of Zeolite from Malang as Catalyst for Plastic Waste Conversion to Fuel". Key Engineering Materials 851 (luglio 2020): 212–19. http://dx.doi.org/10.4028/www.scientific.net/kem.851.212.
Testo completoAbstract (sommario):
Plastic pollution is an environmental problem that has not resolved until now. Pyrolysis is able to be a solution to reduce plastic waste. The use of catalysts will reduce heating temperatures, speed up processing time, and increase product yield. Natural zeolite has the potency as a catalyst in pyrolysis process due to its micropore structure, high acidity and thermal stability. The purpose of this research is to determine the effect of active zeolite catalyst on the polypropylene pyrolysis. The main process of this study is pyrolysis of polypropylene (PP) plastic waste without catalysts and with natural zeolite catalysts which were non-activated and activated. Natural zeolites were activated by HF, HCl and NH4Cl. The well result of this research is represented by the yield, viscosity, calorific value, FTIR and GC-MS analysis. Based on the results of diffractogram analysis, natural zeolites catalyst in this study is included in modernite minerals crystalline. The ratio of Si/Al in zeolite before activation was 7.07 and the acidity was 0.697 g/mmol. After the activation process, the ratio of Si/Al and zeolite acidity increased by 62.181% and 43.84%. The use of active natural zeolite catalysts in pyrolysis PP could reduce the total reaction time by 57.14%. Pyrolysis products with active zeolite catalyst compared to without catalysts had clearer color and higher heating value, compared to pirolysis without catalyst. Based on function group analysis with FTIR, the mixture of hydrolyzed compounds containing successive functional groups are-C-H (alkanes), double bond of C=C, hydroxyl-OH group which can be determined as phenol (ArOH), alcohol (ROH), and carboxylic acid (RCOOH). The GC-MS analysis showed that pyrolysis products are composed of a mixture of alkanes, cycloalkanes, alkenes, carboxylic acids with aromatic rings, and ketones. The pyrolysis products without catalysts consist of 5-11 (C5-C11) carbon atoms, whereas the range of carbon atoms of pyrolysis products with active zeolite catalysts was 6-24 (C6-C24).
41
Stevanovic, Sanja, Dusan Tripkovic, Dejan Poleti, Jelena Rogan, Amalija Tripkovic e Vladislava Jovanovic. "Microwave sinthesys and characterization of Pt and Pt-Rh-Sn electrocatalysts for ethanol oxidation". Journal of the Serbian Chemical Society 76, n. 12 (2011): 1673–85. http://dx.doi.org/10.2298/jsc110405166s.
Testo completoAbstract (sommario):
Carbon supported Pt and Pt-Rh-Sn catalysts were synthesized by microwave-polyol method in ethylene glycol solution and investigated for the ethanol electro-oxidation reaction. The catalysts were characterized in terms of structure, morphology and composition by employing XRD, STM and EDX techniques. STM analysis indicated rather uniform particles and particle size of below 2 nm for both catalysts. XRD analysis of the Pt/C catalyst revealed two phases, one with the main characteristic peaks of face centered cubic crystal structure (fcc) of platinum and another related to graphite like structure of carbon support Vulcan XC-72R. However, in XRD pattern of the Pt-Rh-Sn/C catalyst diffraction peaks for Pt, Rh or Sn cannot be resolved, indicating an extremely low crystallinity. The small particle sizes and homogeneous size distributions of both catalysts should be attributed to the advantages of microwave assisted modified polyol process in ethylene glycol solution. Pt-Rh- Sn/C catalyst is highly active for the ethanol oxidation with the onset potential shifted for more than 150 mV to negative values and with currents nearly 5 times higher in comparison to Pt/C catalyst. The stability tests of the catalysts, as studied by the chronoamperometric experiments, reveal that the Pt-Rh-Sn/C catalyst is evidently less poisoned then Pt/C catalyst. The increased activity of Pt-Rh-Sn/C in comparison to Pt/C catalyst is most probably promoted by bifunctional mechanism and the electronic effect of alloyed metals.
42
Fakeeha, Anis Hamza, Ahmed Aidid Ibrahim, Muhammad Awais Naeem, Wasim Ullah Khan, Ahmed Elhag Abasaeed, Raja L. Alotaibi e Ahmed Sadeq Al-Fatesh. "Methane decomposition over Fe supported catalysts for hydrogen and nano carbon yield". Catalysis for Sustainable Energy 2, n. 1 (31 dicembre 2015): 71–82. http://dx.doi.org/10.1515/cse-2015-0005.
Testo completoAbstract (sommario):
AbstractProduction of hydrogen, being an environmentally friendly energy source, has gained a lot of attention in the recent years. In this article, iron-based catalysts, with different active metal loadings, supported over magnesia and titania are investigated for hydrogen production via catalytic decomposition of methane. The catalytic activity and stability results revealed that magnesia supported catalysts performed better than titania supported catalysts. Hydrogen reduction temperature of 500°C was obtained suitable for catalyst activation. For magnesia supported catalysts, only higher loadings i.e., 30% and 40% Fe-Mg catalysts showed reasonable activity, while all titania supported catalysts presented less activity as well as deactivation. Among all the catalysts, 30% Fe/MgO catalyst displayed better activity. The formation of carbon nanofibers was evidenced from morphological analysis. FESEM and TEM images showed the generation of nonuniform carbon nanofibers with broader diameter. The catalysts were characterized using different techniques such as BET, H2-TPR, O2-TPO, XRD, TGA, FESEM and TEM.
43
Okon, Edidiong, Habiba Shehu e Edward Gobina. "An Experimental Analysis of Lactic Acid Esterification Process Using Langmuir-Hinshelwood Model". Key Engineering Materials 733 (marzo 2017): 36–41. http://dx.doi.org/10.4028/www.scientific.net/kem.733.36.
Testo completoAbstract (sommario):
In this study, esterification of lactic acid and ethanol to produce ethyl lactate using different cation-exchange resin catalysts was performed at 100 °C. The catalysts used for the esterification process were amberlyst 16 and dowex 50W8x cation-exchange resins. Two simplified mechanisms based on Langmuir-Hinshelwood model were employed to describe the components that adsorbed most on the surface of the catalysts. Fourier Transform Infrared (Nicolet iS10 FTIR) was employed to verify the rationality of the mechanisms. FTIR of the esterification product reflected C=O, H=O and C=C bonds on the spectra confirming water and ethanol as the most adsorbed components. The kinetic study of the retention time and the peak areas of the esterification produced with the different catalysts were compared using an autosampler gas chromatography/mass spectrometry (autosampler GC-MS). The chromatogram of the esterification product catalysed by amberlyst 16 showed a faster elution at 1.503 mins with the peak area of 1229816403 m2 in contrast to the dowex 50W8x. The BET surface area and BJH pore size distribution of the resin catalysts were determined using liquid nitrogen adsorption (Quantachrome, 2013) at 77 K. The BET surface area results of amberlyst 16 resin catalysts was found to be 1.659m2/g compared to 0.1m2/g for the dowex 50W8x. The BJH results of the catalysts exhibited a type IV isotherm with hysteresis confirming that the materials were mesoporous with pore size in the region of 2 – 50 nm.
44
Li, Yandong, Guangfen Liang, Chengrui Wang, Yanhong Fang e Huamei Duan. "Effect of Precipitated Precursor on the Catalytic Performance of Mesoporous Carbon Supported CuO-ZnO Catalysts". Crystals 11, n. 6 (22 maggio 2021): 582. http://dx.doi.org/10.3390/cryst11060582.
Testo completoAbstract (sommario):
As part of concepts for chemical energy storage of excess chemical energy produced from renewable sources, we investigated the performance of CuO/ZnO catalysts supported on mesoporous carbon to convert CO2 hydrogenation to methanol. In this work, mesoporous carbon was used as the catalyst support for CuO-ZnO catalysts. Four catalysts with different precipitated precursors were synthesized and analyzed by N2-physisorption, X-ray diffraction (XRD), thermogravimetric analysis (TG-DTG), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results show that catalyst CZ-in situ had the highest turnover frequency (TOF) (2.8 × 10−3 s−1) and methanol production rate (0.8 mmol g−1·h−1). The catalysts for co-precipitation of copper and zinc on carbon precursors are more active. Cu/ZnO domains that are accessible to the reactant gas are another reason for the catalysts being active. The Cu-ZnO interface is crucial to methanol catalyst activity.
45
Alayat, Abdulbaset, Elena Echeverria, Farid Sotoudehniakarani, David N. Mcllroy e Armando G. McDonald. "Alumina Coated Silica Nanosprings (NS) Support Based Cobalt Catalysts for Liquid Hydrocarbon Fuel Production From Syngas". Materials 12, n. 11 (4 giugno 2019): 1810. http://dx.doi.org/10.3390/ma12111810.
Testo completoAbstract (sommario):
The effects of Al2O3 coating on the performance of silica nanospring (NS) supported Co catalysts for Fischer–Tropsch synthesis (FTS) were evaluated in a quartz fixed-bed microreactor. The Co/NS-Al2O3 catalysts were synthesized by coating the Co/NS and NS with Al2O3 by an alkoxide-based sol-gel method (NS-Al-A and NS-Al-B, respectively) and then by decorating them with Co. Co deposition was via an impregnation method. Catalysts were characterized before the FTS reaction by the Brunauer–Emmett–Teller (BET) method, X-ray diffraction, transmission electron microscopy, temperature programmed reduction, X-ray photoelectron spectroscopy, differential thermal analysis and thermogravimetric analysis in order to find correlations between physico-chemical properties of catalysts and catalytic performance. The products of the FTS were trapped and analyzed by GC-TCD and GC-MS to determine the CO conversion and reaction selectivity. The Al2O3 coated NS catalyst had a significant affect in FTS activity and selectivity in both Co/NS-Al2O3 catalysts. A high CO conversion (82.4%) and Σ > C6 (86.3%) yield were obtained on the Co/NS-Al-B catalyst, whereas the CO conversion was 62.8% and Σ > C6 was 58.5% on the Co/NS-Al-A catalyst under the same FTS experimental condition. The Co/NS-Al-A catalyst yielded the aromatic selectivity of 10.2% and oxygenated compounds.
46
Yang, Rui Qin, Xi Kun Gai, Chuang Xing, Jian Wei Mao e Cheng Xue Lv. "Performance of Cu-Based Catalysts in Low-Temperature Methanol Synthesis". Advanced Materials Research 1004-1005 (agosto 2014): 1623–26. http://dx.doi.org/10.4028/www.scientific.net/amr.1004-1005.1623.
Testo completoAbstract (sommario):
The reactions of the methanol synthesis were conducted from the CO/CO2/H2 on the Cu-based catalysts using different solvent at 443 K and 3.0 MPa. The alcohol solvent had the activity in the low-temperature methanol synthesis reaction. The activity of the Cu-based catalyst with ZnO as carrier was higher than that of the catalyst with CeO2, Al2O3, or TiO2 as carrier separately in the reaction. The addition of the CeO2 to the Cu/ZnO catalysts improved the copper species dispersion, so that it was easier for the reduction of the Cu/CeO2-ZnO catalyst than that of the Cu/ZnO catalyst according to the TPR analysis. The variation trend of the BET surface area and the copper surface area was consistent with those of the activity for the Cu/ZnO and the Cu/CeO2-ZnO catalysts in the reaction. The activity of the Cu/CeO2-ZnO catalyst was higher than that of the Cu/ZnO catalyst in the reaction.
47
Hamzah, Noraini, Wan Nor Roslam Wan Isahak, Nadia Farhana Adnan, Nor Asikin Mohamad Nordin, Mohamad Bin Kassim e Mohd Ambar Yarmo. "Catalytic Activity and Physical Properties of Nanoparticles Metal Supported on Bentonite for Hydrogenolysis of Glycerol". Advanced Materials Research 364 (ottobre 2011): 211–16. http://dx.doi.org/10.4028/www.scientific.net/amr.364.211.
Testo completoAbstract (sommario):
Catalysts prepared from a variety of noble metal (Os, Ru, Pd and Au) supported on bentonite using impregnation method were studied and it found these series catalyst system gave different activity and selectivity. Among these catalysts, Os/bentonite and Ru/bentonite catalyst showed high activity in glycerol hydrogenolysis reaction at 150°C, 2.0 MPa initial hydrogen pressure for 7 hours. TEM analysis revealed that these nanometal particles catalyst have different in size and result showed that Os and Ru which have smaller average size in range 1-3 nm gave high activity which are 54.1% and 61.2% respectively. In contrast, less activity was obtained when using Pd/bentonite (29.0%) and Au/bentonite (27.8%) catalyst and TEM result showed that Pd and Au nanoparticles have large average particles size (8-10) nm. NH3-TPD analysis revealed that Ru/bentonite and Os/bentonite catalyst gave high total acidity and this behaviour contribute to high activity of the catalyst. This study revealed that size of nanoparticles and catalyst acidity play an important role in the activity and selectivity in glycerol hydrogenolysis reaction. These catalysts were also characterized by BET, XRD and XPS in order to get some physicochemical properties of the catalyst.
48
Alsalme, Ali, Aliyah A. Alsharif, Hamda Al-Enizi, Mujeeb Khan, Saad G. Alshammari, Mshari A. Alotaibi, Rais Ahmad Khan e Mohammed Rafiq H. Siddiqui. "Probing the Catalytic Efficiency of Supported Heteropoly Acids for Esterification: Effect of Weak Catalyst Support Interactions". Journal of Chemistry 2018 (24 luglio 2018): 1–10. http://dx.doi.org/10.1155/2018/7037461.
Testo completoAbstract (sommario):
Supported heteropoly acids are an interesting class of solid acid catalysts which possess flexible structure and super acidic properties essentially required for the oil-based biodiesel production. In this study, a series of catalysts containing 25 wt.% of heteropolytungstate (HPW) supported on various clays or SiO2 were prepared, and their catalytic efficiency was evaluated for esterification of acetic acid with heptanol. The as-prepared catalysts were characterized by various techniques including FT-IR spectroscopy, thermogravimetric analysis, X-ray diffraction, scanning electron microscopy, and BET. The catalytic efficiency of both bulk and supported HPW catalysts for the esterification activity strongly depends on the type of support and amount of catalyst; the bulk HPW catalyst and the catalyst supported by kaolinite with 25 wt.% of HPW exhibited highest activity. In order to study the effect of temperature on conversion, all the catalysts were subjected to different reaction temperatures. It was revealed that esterification activity of both bulk and supported HPW catalysts strongly depends upon the temperature variations of the reaction. Besides, the effect of leaching of active sites on the catalysts performance for biodiesel production was also evaluated by inductively coupled plasma studies (ICP). The kaolinite-supported catalyst (25% HPW/kaolinite) demonstrated higher amount of leaching which is also confirmed by the significant decrease in its catalytic activity when it is used for the second time. However, the higher activity demonstrated by HPW/kaolinite maybe because of some homogeneous reaction indicating a weak catalyst support interaction (WCSI) resulting in the leaching of the catalyst during the test. Furthermore, the effects of other reaction variables such as catalyst loading and reaction time on the conversion of acetic acid were also studied.
49
Lanre, Mahmud S., Ahmed S. Al-Fatesh, Anis H. Fakeeha, Samsudeen O. Kasim, Ahmed A. Ibrahim, Abdulrahman S. Al-Awadi, Attiyah A. Al-Zahrani e Ahmed E. Abasaeed. "Catalytic Performance of Lanthanum Promoted Ni/ZrO2 for Carbon Dioxide Reforming of Methane". Processes 8, n. 11 (20 novembre 2020): 1502. http://dx.doi.org/10.3390/pr8111502.
Testo completoAbstract (sommario):
Nickel catalysts supported on zirconium oxide and modified by various amounts of lanthanum with 10, 15, and 20 wt.% were synthesized for CO2 reforming of methane. The effect of La2O3 as a promoter on the stability of the catalyst, the amount of carbon formed, and the ratio of H2 to CO were investigated. In this study, we observed that promoting the catalyst with La2O3 enhanced catalyst activities. The conversions of the feed, i.e., methane and carbon dioxide, were in the order 10La2O3 > 15La2O3 > 20La2O3 > 0La2O3, with the highest conversions being about 60% and 70% for both CH4 and CO2 respectively. Brunauer–Emmett–Teller (BET) analysis showed that the surface area of the catalysts decreased slightly with increasing La2O3 doping. We observed that 10% La2O3 doping had the highest specific surface area (21.6 m2/g) and the least for the un-promoted sample. The higher surface areas of the promoted samples relative to the reference catalyst is an indication of the concentration of the metals at the mouths of the pores of the support. XRD analysis identified the different phases available, which ranged from NiO species to the monoclinic and tetragonal phases of ZrO2. Temperature programmed reduction (TPR) analysis showed that the addition of La2O3 lowered the activation temperature needed for the promoted catalysts. The structural changes in the morphology of the fresh catalyst were revealed by microscopic analysis. The elemental compositions of the catalyst, synthesized through energy dispersive X-ray analysis, were virtually the same as the calculated amount used for the synthesis. The thermogravimetric analysis (TGA) of spent catalysts showed that the La2O3 loading of 10 wt.% contributed to the gasification of carbon deposits and hence gave about 1% weight-loss after a reaction time of 7.5 h at 700 °C.
50
Gutiérrez-Ortega, Norma, Esthela Ramos-Ramírez, Alma Serafín-Muñoz, Adrián Zamorategui-Molina e Jesús Monjaraz-Vallejo. "Use of Co/Fe-Mixed Oxides as Heterogeneous Catalysts in Obtaining Biodiesel". Catalysts 9, n. 5 (29 aprile 2019): 403. http://dx.doi.org/10.3390/catal9050403.
Testo completoAbstract (sommario):
Catalyst-type mixed metal oxides with different compositions and Co/Fe ratios were obtained from layered double hydroxides to be used as heterogeneous catalysts in the production of biodiesel. The effect of the Co/Fe ratio on the precursors of the catalysts was analyzed, considering their thermal, textural and structural properties. The physicochemical properties of the catalysts were determined by thermogravimetric analysis (differential scanning calorimetry and thermogravimetric), X-ray diffraction, Fourier-transform infrared spectroscopy, Scanning Electron Microscopy-Energy Dispersive X-ray spectroscopy and N2-physisorption. The conversion to biodiesel using the different catalysts obtained was determined by diffuse reflectance infrared Fourier-transform spectroscopy and 1H-Nuclear magnetic resonance spectroscopy, allowing us to correlate the effect of the catalyst composition with the catalytic capacity. The conditions for obtaining biodiesel were optimized by selecting the catalyst and varying the percentage of catalyst, the methanol/oil ratio and the reaction time. The catalysts reached yields of conversion to biodiesel of up to 96% in 20 min of reaction using only 2% catalyst. The catalyst that showed the best catalytic activity contains a mixture of predominant crystalline and amorphous phases of CoFe2O4 and NaxCoO2. The results suggest that cobalt is a determinant in the activity of the catalyst when forming active sites in the crystalline network of mixed oxides for the transesterification of triglycerides, with high conversion capacity and selectivity to biodiesel.