Letteratura scientifica selezionata sul tema "Catalysie"
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Articoli di riviste sul tema "Catalysie"
1
Zhao, Xiaodan, e Lihao Liao. "Modern Organoselenium Catalysis: Opportunities and Challenges". Synlett 32, n. 13 (11 maggio 2021): 1262–68. http://dx.doi.org/10.1055/a-1506-5532.
Testo completoAbstract (sommario):
AbstractOrganoselenium catalysis has attracted increasing interest in recent years. This Cluster highlights recent key advances in this area regarding the functionalization of alkenes, alkynes, and arenes by electrophilic selenium catalysis, selenonium salt catalysis, selenium-based chalcogen-bonding catalysis, and Lewis basic selenium catalysis. These achievements might inspire and help future research.1 Introduction2 Electrophilic Selenium Catalysis3 Selenonium Salt Catalysis4 Selenium-Based Chalcogen-Bond Catalysis5 Lewis Basic Selenide Catalysis6 Conclusion
2
Dagorne, Samuel. "Recent Developments on N-Heterocyclic Carbene Supported Zinc Complexes: Synthesis and Use in Catalysis". Synthesis 50, n. 18 (28 giugno 2018): 3662–70. http://dx.doi.org/10.1055/s-0037-1610088.
Testo completoAbstract (sommario):
The present contribution reviews the synthesis, reactivity, and use in catalysis of NHC–Zn complexes reported since 2013. NHC-stabilized Zn(II) species typically display enhanced stability relative to common organozinc species (such as Zn dialkyls), a feature of interest for the mediation of various chemical processes and the stabilization of reactive Zn-based species. Their use in catalysis is essentially dominated by reduction reactions of various unsaturated small molecules (including CO2), thus primarily involving Zn–H and Zn–alkyl derivatives as catalysts. Simple NHC adducts of Zn(II) dihalides also appear as effective catalysts for the reduction amination of CO2 and borylation of alkyl/aryl halides. Stable and well-defined Zn alkoxides have also been prepared and behave as effective catalysts in the polymerization of cyclic esters/carbonates for the production of well-defined biodegradable materials. Overall, the attractive features of NHC-based Zn(II) species include ready access, a reasonable stability/reactivity balance, and steric/electronic tunability (through the NHC source), which should promote their further development.1 Introduction2 NHC-Supported Zinc Alkyl/Aryl Species2.1 Synthesis2.2 Reactivity and Use in Catalysis3 NHC-Supported Zinc Hydride Species3.1 Synthesis3.2 Reactivity and Use in Catalysis4 NHC-Supported Zinc Amido/Alkoxide Species4.1 Synthesis4.2 Use in Catalysis5 NHC-Supported Zinc Dihalide Species5.1 Synthesis5.2 Use in Catalysis6 Other NHC-Stabilized Zn Species7 Conclusion
3
Ding, Bo, Qilin Xue, Hong-Gang Cheng, Qianghui Zhou e Shihu Jia. "Recent Advances in Catalytic Nonenzymatic Kinetic Resolution of Tertiary Alcohols". Synthesis 54, n. 07 (2 dicembre 2021): 1721–32. http://dx.doi.org/10.1055/a-1712-0912.
Testo completoAbstract (sommario):
AbstractThe kinetic resolution (KR) of racemates is one of the most widely used approaches to access enantiomerically pure compounds. Over the past two decades, catalytic nonenzymatic KR has gained popularity in the field of asymmetric synthesis due to the rapid development of chiral catalysts and ligands in asymmetric catalysis. Chiral tertiary alcohols are prevalent in a variety of natural products, pharmaceuticals, and biologically active chiral compounds. The catalytic nonenzymatic KR of racemic tertiary alcohols is a straightforward strategy to access enantioenriched tertiary alcohols. This short review describes recent advances in catalytic nonenzymatic KR of tertiary alcohols, including organocatalysis and metal catalysis.1 Introduction2 Organocatalysis2.1 Peptide Catalyst2.2 Chiral Phosphoric Acid Catalyst2.3 Chiral Lewis Base Catalyst2.4 Chiral Quaternary Ammonium Salt Catalyst3 Metal Catalysis3.1 Mixed La-Li Heterobimetallic Catalyst3.2 Rh Catalyst3.3 Hf Catalyst3.4 Pd Catalyst3.5 Cu Catalyst3.6 Ag Catalyst4 Conclusion and Outlook
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Li, Feng, e Hao Li. "Spatial compartmentalisation effects for multifunctionality catalysis: From dual sites to cascade reactions". Innovation & Technology Advances 2, n. 1 (12 marzo 2024): 1–13. http://dx.doi.org/10.61187/ita.v2i1.54.
Testo completoAbstract (sommario):
Catalysis plays a key role in the production of fuels, industrial chemicals and the chemical transformation of fine chemicals. As society faces increasing environmental pollution and energy crises, tandem catalysis has attracted increasing attention as an outstanding model due to its sustainability and environmental friendliness. Compared with traditional stepwise synthesis methods, tandem catalysis not only can couple several different reactions together, but also does not require the separation of intermediates, which provides new ideas for improving reaction activity, regulating product selectivity and developing new methods for catalysis. In order to catalyse cascade reactions efficiently, it is crucial to design suitable multifunctional catalysts, which should contain at least two active sites and achieve spatial separation. Here, we introduce the realisation and application of spatial segregation of metal, acidic and basic sites with examples to provide further insight into the indispensable role of active site compartmentalisation effects in tandem catalysis. In addition, this study highlights the challenges and issues associated with such catalysts, emphasising the importance of effective catalyst enhancement and environmentally sustainable catalytic transformations. The results of the study are intended to provide guidance for the development of rational and efficient catalysts.
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Shi, Chunjie, Xiaofeng Yu, Wei Wang, Haibing Wu, Ai Zhang e Shengjin Liu. "The Activity and Cyclic Catalysis of Synthesized Iron-Supported Zr/Ti Solid Acid Catalysts in Methyl Benzoate Compounds". Catalysts 13, n. 6 (2 giugno 2023): 971. http://dx.doi.org/10.3390/catal13060971.
Testo completoAbstract (sommario):
The catalytic activity and cyclic catalysis of different methyl benzoates were studied by using a series of Lewis solid acid catalysts. The iron-supported zirconium/titanium solid acid catalysts were characterized using FTIR, SEM, XRD, and BET. The details of catalytic activity and cyclic catalysis verified that the catalyst catalyzed the reactions of 31 benzoic acids with different substituents and methanol. In addition, the mechanism was revealed according to the microstructure, acid strength, and specific surface area of the catalysts, and the yields of methyl benzoates by the GC-MS. Zr ions had significant effects on the catalytic activity of the catalyst. A certain proportion of Fe and Ti ions additionally enhanced the catalytic activity of the catalyst, with the catalyst-specific composition of Fe:Zr: Ti = 2:1: 1 showing optimal catalytic activity. A variety of substituents in the benzene ring, such as the electron-withdrawing group, the electron-donating group, large steric hindrance, and the position of the group on the benzene ring, had regular effects on the catalytic activity of the methyl benzoates. An increase in the catalyst activity occurred owing to the increases in the catalyst surface and the number of acid sites after the Fe ion was added. The catalytic activity remained unchanged after the facile recycling method was performed.
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Clerici, Mario G. "Zeolites for Fine Chemical Production State of Art and Perspectives". Eurasian Chemico-Technological Journal 3, n. 4 (10 luglio 2017): 231. http://dx.doi.org/10.18321/ectj573.
Testo completoAbstract (sommario):
The paper analyses the role of catalysis and that of renewable resources in the frame of a sustainable development. The possible uses of natural feedstocks for chemical production and the application of catalytic<br />methods to their transformations are reviewed, with emphasis on carbohydrates and vegetable oils and on zeolite catalysts, respectively. The problems arising from the embedment of active sites on the catalyst<br />surface are discussed, with the aid of specific examples taken from oxidation and acid catalysed reactions.
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Zhang, Meng. "A Novel Energy Band Match Method and a Highly Efficient CuO–Co3O4@SiO2 Catalyst for Dimethyl Carbonate Synthesis from CO2". Science of Advanced Materials 13, n. 1 (1 gennaio 2021): 115–22. http://dx.doi.org/10.1166/sam.2021.3848.
Testo completoAbstract (sommario):
The present research on dimethyl carbonate (DMC) synthesis from CO2 was short of effective theoretical guidance and catalyst design was also blind. A kind of regular relationship was found from catalyst structure calculation and activity experiments. Therefore, a novel energy band matching method was proposed. After substantial verification experiments, it was proved to be correct. Whether one certain catalyst has catalytic activity can be judged predictably according to this novel method. Novel and efficient catalysts can be designed or selected on the basis of designer's wishes. Based on this method, three efficient catalysts were prepared and CuO–Co3O4@SiO2 catalyst had the best catalytic performance. In a word, once it is applied in catalysts research, there will be a huge progress in catalysis and materials science fields.
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Jankovič, Ľuboš, e Peter Komadel. "Catalytic Properties of a Heated Ammonium-Saturated Dioctahedral Smectite". Collection of Czechoslovak Chemical Communications 65, n. 9 (2000): 1527–36. http://dx.doi.org/10.1135/cccc20001527.
Testo completoAbstract (sommario):
A series of acid catalysts was prepared by heating of NH4-saturated montmorillonite at 200-600 °C for 24 h. Their catalytic activity was tested in acetylation of 3,4,5-trimethoxybenzaldehyde with acetic anhydride. This reaction is sufficiently sensitive to modification of the catalyst and thus suitable for testing catalytic activity of modified montmorillonites. Most of the prepared catalysts were able to catalyse the test reaction and produce diacetate in higher than 50% yields. The most active catalyst was obtained after heating at 300 °C. It was slightly less effective than commercially available acid-activated K10 catalyst.
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Zhuang, Huimin, Bili Chen, Wenjin Cai, Yanyan Xi, Tianxu Ye, Chuangye Wang e Xufeng Lin. "UiO-66-supported Fe catalyst: a vapour deposition preparation method and its superior catalytic performance for removal of organic pollutants in water". Royal Society Open Science 6, n. 4 (aprile 2019): 182047. http://dx.doi.org/10.1098/rsos.182047.
Testo completoAbstract (sommario):
A vapour deposition (VD) method was established for preparation of the UiO-66-supported Fe (Fe/UiO-66) catalyst, which provided the first case of the metal-organic framework (MOF)-supported Fe catalyst prepared by using the vapour-based method. The Fe loading was around 7.0–8.5 wt% under the present preparation conditions. The crystal structure of UiO-66 was not obviously influenced by the Fe loading, while the surface area significantly decreased, implicating most of the Fe components resided in the pores on UiO-66. The results for the methyl orange (MO) removal tests showed that MO in aqueous solution can be removed by UiO-66 by adsorption, and in contrast, it can be oxidized by H 2 O 2 with the catalysis of Fe/UiO-66. Further catalytic tests showed that Fe/UiO-66 was rather effective to catalyse the oxidation of benzene derivatives like aniline in water in terms of chemical oxygen demand (COD) removal efficiency. The catalytic test results for Fe/UiO-66 were compared to those of Fe/Al 2 O 3 with the same Fe loading and to the catalysts reported in the literature. This paper provides a general strategy for VD preparation of MOF-supported Fe catalyst on the one hand, and new catalysts for removing organic pollutants from water, on the other hand.
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Motokura, Ken, e Kyogo Maeda. "Recent Advances in Heterogeneous Ir Complex Catalysts for Aromatic C–H Borylation". Synthesis 53, n. 18 (9 aprile 2021): 3227–34. http://dx.doi.org/10.1055/a-1478-6118.
Testo completoAbstract (sommario):
AbstractAromatic C–H borylation catalyzed by an Ir complex is among the most powerful methods for activating inert bonds. The products, i.e., arylboronic acids and their esters, are usable chemicals for the Suzuki–Miyaura cross-coupling reaction, and significant effort has been directed toward the development of homogeneous catalysis chemistry. In this short review, we present a recent overview of current heterogeneous Ir-complex catalyst developments for aromatic C–H borylation. Not only have Ir complexes been immobilized on support surfaces with phosphine and bipyridine ligands, but Ir complexes incorporated within solid materials have also been developed as highly active and reusable heterogeneous Ir catalysts. Their catalytic activities and stabilities strongly depend on their surface structures, including linker length and ligand structure.1 Introduction and Homogeneous Ir Catalysis2 Heterogeneous Ir Complex Catalysts for C–H Borylation Reactions3 Other Heterogeneous Metal Complex Catalysts for C–H Borylation Reactions4 Summary and Outlook
Tesi sul tema "Catalysie"
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Grieco, Francesco. "Le rôle de la poussière carbonée dans le milieu interstellaire en tant que catalyseur pour la formation de molécules et la croissance des grains". Electronic Thesis or Diss., CY Cergy Paris Université, 2024. http://www.theses.fr/2024CYUN1306.
Testo completoAbstract (sommario):
Cette thèse présente une étude complète de l'interaction entre les grains de poussière et diverses espèces en phase gazeuse dans le milieu interstellaire. Les principaux résultats impliquent l'utilisation de surfaces comme la glace et le coronène, une surface qui ressemble aux hydrocarbures aromatiques polycycliques (PAH), avec des éléments H et O en phase gazeuse. Nous étudions comment les grains de poussière peuvent catalyser la formation de nouvelles molécules par des processus comme l'adsorption, la diffusion, les réactions de surface et la désorption dans des conditions typiques du milieu interstellaire.La thèse comprend trois chapitres expérimentaux (4, 5 et 6), réalisés au LERMACYU en utilisant la configuration FORMOLISM, qui sont complétés par deux études théoriques (chapitres 8 et 9), menées avec les codes Cloudy et Nautilus à l'UGent. Les expériences se concentrent sur le rôle que jouent les différentes surfaces de grains de poussière et les couches de glace sur les énergies de liaison (BE) des molécules (chapitre 4), sur la formation expérimentale de H2 sur le coronène jusqu'à 250 K (chapitre 5) et sur la formation d'eau solide sur la poussière à des températures allant jusqu'à 85 K (chapitre 6). Plusieurs implications astrophysiques sont également discutées.Les résultats présentés au chapitre 5 montrent comment H2 peut se former dans des nuages moléculaires avec des températures de poussière >20 K et cela est extrêmement pertinent pour expliquer l'efficacité de H2 et de la formation d'étoiles dans les galaxies à fort décalage vers le rouge. Le chapitre 6 donne de nouvelles perspectives sur la formation de manteaux de glace qui pourraient se former à une température plus élevée que celle démontrée précédemment,étant un moyen significatif d'expliquer l'appauvrissement en O élémentaire en phase gazeuse observé dans de telles conditions. De plus, la disparition des PAH lors de la transition des nuages diffus aux nuages denses pourrait s'expliquer par le fait que les grains de poussière commencent à être recouverts par des couches de glace. Dans le chapitre 8, nous étudions l'effet de la formation expérimentale de H2 à haute température sur les PAH sur la localisation du front de dissociation (DF) dans une image PDR classique, en le modélisant avec Cloudy. À partir d'une implémentation de base des résultats expérimentaux du chapitre 5 dans le code, il a été difficile de quantifier cet effet. Cela souligne combien il reste encore beaucoup de travail à faire sur les modèles pour mieux correspondre aux observations. Dans le chapitre 9, certaines questions concernant l'appauvrissement en O dans les nuages translucides et la croissance des grains introduites au chapitre 6 sont abordées avec Nautilus. En utilisant une stratégie innovante, nous avons pu reproduire les appauvrissements en C et O dans des conditions de nuages translucides en les verrouillant dans deux espèces de surface distinctes lors de l'adsorption, reproduisant le rapport de structure moléculaire des carbonates organiques. Cette thèse montre l'incroyable nature catalytique des PAH et leur capacité à permettre des processus de chimisorption pour la formation de molécules à des températures de poussière élevées. Il s'agit d'un résultat important qui peut être lié aux nouvelles découvertes rapportant la possibilité d'avoir une croissance des grains à des nH plus faiblesThis Thesis presents a comprehensive study of the interaction between dust grains andvarious gas-phase species in the ISM. The main results involve the use of surfaces likeices and coronene, a surface that resembles polycyclic aromatic hydrocarbons (PAHs),with gas-phase H and O elements. We investigate how dust grains can catalyze the formation of new molecules through processes like adsorption, diffusion, surface reactions and desorption in typical ISM conditions.The Thesis includes three experimental Chapters (4, 5 and 6), performed at LERMACYUby using the FORMOLISM setup, that are complemented by two theoretical studies(Chapters 8 and 9), conducted with Cloudy and Nautilus codes at UGent. The experiments focus on the role that different dust grain surfaces and ice layers have onthe Binding Energies (BEs) of molecules (Chapter 4), on the experimental formation ofH2 on coronene up to 250 K (Chapter 5) and on the formation of solid water on dustat temperatures up to 85 K (Chapter 6). Several astrophysical implications are alsodiscussed.The results presented in Chapter 5 show how H2 can form in molecular clouds with dusttemperatures >20 K and this is extremely relevant to explain the efficient H2 and starformation in high redshift galaxies. Chapter 6 gives new insights on the formation oficy mantles that could be forming at higher temperature than previously demonstrated,being a significant way to explain the gas-phase elemental O depletion observed in suchconditions. Moreover, the disappearance of PAHs in the transition from diffuse to denseclouds could be explained by the dust grains starting to be covered by ice layers. InChapter 8 we study the effect of the high temperature experimental H2 formation onPAHs on the location of the dissociation front (DF) in a classical PDR picture, bymodelling it with Cloudy. From a basic implementation of the experimental results ofChapter 5 in the code, it has been challenging to quantify such effect. This underlineshow a lot of work still needs to be done on models to better match observations. InChapter 9 some questions regarding O depletion in translucent clouds and grain growthintroduced in Chapter 6 are addressed with Nautilus. By using an innovative strategy,we were able to reproduce C and O depletions in translucent cloud conditions by lockingthem in two separate surface species upon adsorption, reproducing the molecular structure ratio of organic carbonates.This Thesis shows the incredible catalytic nature of PAHs and their capacity to enablechemisorption processes for the formation of molecules at high dust temperatures. Thisis an important result that can be linked to the new discoveries reporting the possibilityof having grain growth at lower nH
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Fiske, Thomas Haukli. "Correlation of Catalyst Morphology with Attrition Resistance and Catalytic Activity of Fischer-Tropsch Catalysts". Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for kjemisk prosessteknologi, 2013. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-22778.
Testo completoAbstract (sommario):
Three alumina based support materials for the Fischer-Tropsch synthesis (FTS) catalyst has been prepared and investigated. The three support materials were prepared in order to obtain different mechanical strengths, henceforth denoted weak, medium and strong support. Magnesium modified γ-alumina support material calcined at 950°C and 1050°C were prepared as the medium and strong support respectively, whereas the unmodified alumina was used as the weak support. The modified support materials were both prepared by the incipient wetness impregnation method to obtain 10 wt .% Mg. Several batches were prepared to gain enough material for the planned experiments.Each of the support materials were subject to one crushing process in order to try to alter the particle morphology. The chosen method was determined based on the results from the specialization project. In this project, one method gave a larger change in morphology than other methods. Therefore a ball mill was the method of choice. Unprocessed samples and samples subjected to the ball mill for the three different materials were tested for attrition in an attrition rig, and characterized in terms of morphology using a particle analyzer. The different fractions were also analyzed with respect to particle morphology using an environmental scanning electron microscope (ESEM). FTS catalysts with 12 wt. % Co and 0,5 wt. % Re were prepared from the weak and the medium support materials, both unprocessed and milled fractions, using the incipient wetness impregnation. These four catalyst samples were tested for dispersion using a chemisorption experiment, and for activity and selectivity using a dedicated setup. Results from the particle analyzer showed that the morphology had not been altered as much as expected. Most change in shape occurred for the medium strength support material, but the observed alteration was much less than observed for the same experiment in the specialization project. For the weaker and stronger support, only a slight change was observed, and for the strong support material this change was in the direction of rounder particles. This is probably due to the excellent mechanical strength of the strong support, which leads to grinding of the kinks and corners of the particles and not the breakage of whole particles to smaller and more uneven fragments. With such relative small differences in morphology between the unprocessed and the milled materials, correlations of morphology with other parameters are difficult to obtain. The same correlation as from the specialization project, with rounder particles having a higher attrition resistance, was observed. A slight degree of correlation was also found between particle morphology and dispersion, where more uneven particles gave a slightly higher value of cobalt dispersion.
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Paliga, James Francis. "Developing Earth-abundant metal-catalysts for hydrofunctionalisation". Thesis, University of Edinburgh, 2018. http://hdl.handle.net/1842/31115.
Testo completoAbstract (sommario):
The iron-catalysed hydromagnesiation of styrene derivatives has been developed further from previous publications, expanding the electrophile scope to enable the regioselective formation of new carbon-carbon and carbon-heteroatom bonds (Scheme A1). A commercially available pre-catalyst and ligand were used to give an operationally simple procedure that did not require prior synthesis of a catalyst. This work also investigated the hydromagnesiation of dienes, using a screen of ligands commonly used in transition metal catalysis. An investigation into the magnesium-catalysed hydroboration of olefins was also carried out. Although mostly unsuccessful, it was demonstrated that in the presence of a magnesium catalyst, a small amount of vinyl boronic ester could be formed from an alkyne (Scheme A2). Simple magnesium salts were also investigated for the reduction of carbonyls. Lastly, this work explored the titanium-catalysed hydrosilylation of olefins, using a novel activation method developed within the group (Scheme A3). The results were compared to those published previously using traditional organometallic activation methods and attempts at identifying conditions to improve chemoselectivity were carried out.
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Large, Benjamin. "Activation sélective de naphtalènes et synthèse d'architectures polycycliques étendues". Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLV070/document.
Testo completoAbstract (sommario):
Comme le naphtalène a récemment émergé comme un socle fondamental en chimie médicinale, le développement de méthodologies menant à des plateformes fonctionnalisées basées sur du naphtalène est devenu un centre d’intérêt majeur de la communauté scientifique. En effet, des conditions expérimentales optimisées sur le benzène ou d’autre noyaux aromatiques ne peuvent pas toujours être transposées au naphtalène. Ces dernières peuvent parfois conduire à des résultats différents, possiblement dû à l’aromaticité plus faible de ce bicycle aromatique.Dans ce contexte, cette thèse s’articule autour du naphtalène et de ses dérivés. Des méthodes variées permettant une fonctionnalisation sélective de différentes positions de cette plateforme, ainsi que des stratégies de synthèses d’architectures polycycliques ont été développées.Notre attention s’est ensuite portée sur des précurseurs du naphtalène, en particulier sur les tetralones. En utilisant une méthode basée sur l’utilisation d’un groupe directeur éphémère, la position 8 de ce bicycle a été arylée, et les différents composés ainsi obtenus ont pu être convertis en d’autre plateformes polycycliques. En complément, des calculs DFT ont permis d’expliquer la régiosélectivité observée lors de la synthèse de fluorenones étendues, et d’étudier le mécanisme d’arylation dirigée des tetralonesBecause naphthalene has recently emerged as a fundamental platform in medicinal chemistry, the development of methodologies leading to diversely functionalised naphthalene-based platforms has become a prime concern of the scientific community. Indeed, experimental conditions previously optimised for benzene and other aromatic rings cannot always be applied to naphthalene. These methods can sometimes lead to different results, as a consequence of the lower aromaticity of the naphthalene core.In this context, this thesis is dedicated to the naphthalene and its derivatives. Various methods to selectively functionalise the different positions of the naphthalene core and synthetic pathways to extended polycyclic architectures were developed.Next, we focused on naphthalene precursors, especially on tetralones. Using a strategy involving a transient directing group, the position 8 of these bicycles was successfully arylated and the resulting compounds were successfully converted into other polycyclic platforms. In addition, DFT calculation have been used to explain the regioselectivity observed during the synthesis of extended fluorenones, and to study the mechanism of directed arylation of tetralones
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Meyer, Simon [Verfasser]. "Carbide Materials as Catalysts and Catalyst Supports for Applications in Water Electrolysis and in Heterogeneous Catalysis / Simon Meyer". München : Verlag Dr. Hut, 2014. http://d-nb.info/1058284967/34.
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Hruby, Sarah Lynn. "Catalytic domains in porous catalysts". [Ames, Iowa : Iowa State University], 2009.
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McGregor, James. "Heterogeneous catalytic hydrogenation and dehydrogenation : catalysts and catalytic processes". Thesis, University of Cambridge, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.612796.
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Richardson, John Michael. "Distinguishing between surface and solution catalysis for palladium catalyzed C-C coupling reactions: use of selective poisons". Diss., Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/22704.
Testo completoAbstract (sommario):
This work focuses on understanding the heterogeneous/homogeneous nature of the catalytic species for a variety of immobilized metal precatalysts used for C-C coupling reactions. These precatalysts include: (i) tethered organometallic palladium pincer complexes, (ii) an encapsulated small molecule palladium complex in a polymer matrix, (iii) mercapto-modified mesoporous silica metalated with palladium acetate, and (iv) amino-functionalized mesoporous silicas metalated with Ni(II). As part of this investigation, the use of metal scavengers as selective poisons of homogeneous catalysis is introduced and investigated as a test for distinguishing heterogeneous from homogeneous catalysis. The premise of this test is that insoluble materials functionalized with metal binding sites can be used to selectively remove soluble metal, but will not interfere with catalysis from immobilized metal. In this way the test can definitely distinguish between surface and solution catalysis of immobilized metal precatalysts.
This work investigates three different C-C coupling reactions catalyzed by the immobilized metal precatalysts mentioned above. These reactions include the Heck, Suzuki, and Kumada reactions. In all cases it is found that catalysis is solely from leached metal. Three different metal scavenging materials are presented as selective poisons that can be used to determine solution vs. surface catalysis. These selective poisons include poly(vinylpyridine), QuadrapureTM TU, and thiol-functionalized mesoporous silica. The results are contrasted against the current understanding of this field of research and subtleties of tests for distinguishing homogeneous from heterogeneous catalysis are presented and discussed.
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Gill, Christopher Stephen. "Novel hybrid organic/inorganic single-sited catalysts and supports for fine chemical and pharmaceutical intermediate synthesis". Diss., Atlanta, Ga. : Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/28218.
Testo completoAbstract (sommario):
Thesis (M. S.)--Chemical Engineering, Georgia Institute of Technology, 2009.Committee Chair: Jones, Christopher; Committee Member: Agrawal, Pradeep; Committee Member: Teja, Amyn; Committee Member: Weck, Marcus; Committee Member: Zhang, John.
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Nguyen, Joseph Vu. "Design, synthesis, and optimization of recoverable and recyclable silica-immobilized atom transfer radical polymerization catalysts". Diss., Georgia Institute of Technology, 2005. http://hdl.handle.net/1853/6860.
Testo completoAbstract (sommario):
Despite the growing interest in heterogeneous polymerization catalysis, the majority of the polymerization catalysts used industrially are single-use entities that are left in the polymer product. Recoverable and recyclable polymerization catalysts have not reached the industrial utility of single-use catalysts because the catalyst and product separation have not become economical. The successful development of recyclable transition metal polymerization catalysts must take a rational design approach, hence academic and industrial researchers need to further expand the fundamental science and engineering of recyclable polymerization catalysis to gain an understanding of critical parameters that allow for the design of economically viable, recoverable solid polymerization catalysts.
Unfortunately, the rapid development of Atom Transfer Radical Polymerization over the past 10 years has not resulted in its wide spread industrial practice. Numerous reports regarding the immobilization of transition metal ATRP catalysts, in attempts to increase its applicability, have extended the fundamentals of recyclable polymerization catalysis. However, for industrial viability, more research is required in the area of how the catalyst complex immobilization methodology and support structure affect the catalyst polymerization performance, regeneration, and recyclability. A comprehensive rational catalyst design approach of silica-immobilized ATRP catalyst was undertaken to answer these questions and are discussed here.
Libri sul tema "Catalysie"
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International Symposium on Catalyst Deactivation (8th 1999 Brugge, Belgium). Catalyst deactivation 1999: Proceedings of the 8th International Symposium, Brugge, Belgium, October 10-13, 1999. Amsterdam: Elsevier, 1999.
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1937-, Anderson James A., e Fernández Garcia Marcos, a cura di. Supported metals in catalysis. London: Imperial College Press, 2005.
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J, Thomas W., a cura di. Principles and practice of heterogeneous catalysis. Weinheim: VCH, 1996.
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Ma, Zhen, e Sheng Dai, a cura di. Heterogeneous Gold Catalysts and Catalysis. Cambridge: Royal Society of Chemistry, 2014. http://dx.doi.org/10.1039/9781782621645.
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1959-, Regalbuto John R., a cura di. Handbook of catalyst preparation. Boca Raton: Taylor & Francis, 2007.
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H, Bartholomew Calvin, a cura di. Fundamentals of industrial catalytic processes. 2a ed. Hoboken, N.J: Wiley, 2005.
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Wijngaarden, R. J. Industrial catalysis: Optimizing catalysts and processes. Weinheim: Wiley-VCH, 1998.
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1934-, Davis Burtron H., e Occelli Mario L. 1942-, a cura di. Fischer-Tropsch synthesis, catalysts and catalysis. Boston: Elsevier, 2007.
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Furimsky, Edward. Catalysts for upgrading heavy petroleum feeds. Amsterdam: Elsevier, 2007.
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Furimsky, Edward. Catalysts for upgrading heavy petroleum feeds. Amsterdam: Elsevier, 2004.
Cerca il testo completoCapitoli di libri sul tema "Catalysie"
1
Gao, Yuanfeng, Hong Lv, Yongwen Sun, Han Yao, Ding Hu e Cunman Zhang. "Enhancement of Acidic HER by Fe Doped CoP with Bimetallic Synergy". In Proceedings of the 10th Hydrogen Technology Convention, Volume 1, 465–74. Singapore: Springer Nature Singapore, 2024. http://dx.doi.org/10.1007/978-981-99-8631-6_45.
Testo completoAbstract (sommario):
AbstractCompared to single metal site catalysis, the bimetallic synergistic strategy can exploit the complementary ability of different active sites for active species uptake and desorption to develop excellent catalysts. Pure phase metal phosphides are a disadvantage as a promising electrocatalyst for platinum-free hydrogen precipitation with either too strong or too weak adsorption of hydrogen. Here, synthetic Fe-doped CoP particles anchored with MWCNTs, which exhibited excellent catalytic performance for HER, required an overpotential of 123 mV to reach 10 mA cm−2, with a Tafel slope of 58.8 mV dec−1. It was found experimentally that Fe doping improved the conductivity of the catalyst regulated the electronic structure of CoP, and optimized the overall hydrogen adsorption energy of the catalyst. The difference in hydrogen adsorption strength of Fe, Co is used to break the symmetry constraint of single active center and improve the intrinsic activity of the catalyst, a strategy that can be used to guide the preparation of inexpensive and high performance catalysts.
2
Deng, Jiayao, Xiao Hu, Gnauizhi Xu, Zhanfeng Deng, Lan Yang, Ding Chen, Ming Zhou e Boyuan Tian. "The Preparation of Iridium-Based Catalyst with Different Melting Point-Metal Nitrate and Its OER Performance in Acid Media". In Proceedings of the 10th Hydrogen Technology Convention, Volume 1, 61–68. Singapore: Springer Nature Singapore, 2024. http://dx.doi.org/10.1007/978-981-99-8631-6_6.
Testo completoAbstract (sommario):
AbstractOxygen evolution reaction (OER) is the main factor limiting the large-scale development of proton-exchange membrane (PEM) hydrogen production. It is urgent to develop catalysts with excellent OER catalytic performance and stability. Herein, several Iridium-based catalysts were prepared by simple mixing and calcination, the OER properties of catalysts with different melting points of nitrates as calcinating additives were investigated. The RbNO3 treated catalyst displayed a low overpotential(η) of 297.6 mV versus RHE, which is lower than the catalyst calcinated without nitrate (323.8 mV vs. RHE). Moreover, the RbNO3 treated catalyst displayed good acid stability over 20 h Chronopotentiometric test. The high OER catalytic activity and stability of RbNO3 treated catalyst may be attribute to the smaller nanoparticle morphology, pure IrO2 structure and high electrochemical surface area (ECSA), which increase the number of active sites and the intrinsic catalytic activity. This work indicated that the catalyst with excellent OER performance can be obtained by selecting nitrate with moderate melting point as the calcinating additive. Nitrates (like RbNO3) treated catalyst with excellent catalytic activity and stability has good application prospect in hydrogen production of PEM water splitting.
3
Pennington, John. "Catalysts and Catalysis". In An Introduction to Industrial Chemistry, 309–49. Dordrecht: Springer Netherlands, 1996. http://dx.doi.org/10.1007/978-94-011-0613-9_12.
Testo completo
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Pennington, J. "Catalysts and Catalysis". In an introduction to Industrial Chemistry, 304–47. Boston, MA: Springer US, 1991. http://dx.doi.org/10.1007/978-1-4615-6438-6_11.
Testo completo
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Lloyd, Lawrie. "Catalytic Cracking Catalysts". In Handbook of Industrial Catalysts, 169–210. Boston, MA: Springer US, 2011. http://dx.doi.org/10.1007/978-0-387-49962-8_5.
Testo completo
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Duan, Lunbo, e Lin Li. "Oxygen Carrier Aided Gasification (OCAG)". In Oxygen-Carrier-Aided Combustion Technology for Solid-Fuel Conversion in Fluidized Bed, 79–96. Singapore: Springer Nature Singapore, 2023. http://dx.doi.org/10.1007/978-981-19-9127-1_5.
Testo completoAbstract (sommario):
AbstractGasification is regarded as an effective clean utilization technology of solid fuel, which can convert the chemical energy of solid fuel into gaseous fuel. However, the primary gas products contain not only the essential gas products, but also an unacceptable amount of tars, which will cause operational problems such as blockage of downstream equipment during gasification. Catalysts are often used after the gasifier to catalyze tar in the pyrolysis product gas. However, the activity ofcatalysts generally declines over time, as they will be poisoned by prolonged exposure to an atmosphere containing elements such as sulfur, chlorine and alkali metals. In addition, under the condition of high tar content, carbon deposition may form on the surface of catalyst, which leads to the deactivation of catalyst. The oxygen carrier particles of natural ores not only can transport oxygen, but also contain various metal elements that can be used as catalysts for tar cracking. Introduce the OCs to replace inert bed materials may not only provide a cheap catalyst for the technology, but also complete the transfer of oxygen between the two reactors, this process is oxygen carrier aided gasification (OCAG).
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Shao, Z., e Y. H. Deng. "2.1.1 General Principles of Metal/Organocatalyst Dual Catalysis". In Dual Catalysis in Organic Synthesis 2. Stuttgart: Georg Thieme Verlag, 2020. http://dx.doi.org/10.1055/sos-sd-232-00002.
Testo completoAbstract (sommario):
AbstractMetal/organocatalyst dual catalysis is a privileged catalytic strategy which involves both a metal-based catalyst and an organocatalyst to catalyze the organic transformation. Based on the type of activation of substrates with both catalysts, there are seven kinds of dual catalysis; namely cooperative catalysis, cascade catalysis, sequential catalysis, double activation catalysis, restorative catalysis, bifunctional catalysis, and multiple relay catalysis. The generic activation of the metal-based catalyst and the organocatalyst applied in the dual-catalytic system is summarized. In these dual-catalytic approaches, the advantages of both metal catalysis and organocatalysis are converged to achieve many transformations that were previously inaccessible or challenging by any single-catalyst paradigm, to develop new reactions, to discover unique reaction mechanisms, and even to allow for stereodivergent synthesis.
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Bowker, Michael. "The reactive interface". In The Basis and Applications of Heterogenuous Catalysis. Oxford University Press, 1998. http://dx.doi.org/10.1093/hesc/9780198559580.003.0001.
Testo completoAbstract (sommario):
This chapter provides a background of catalysis, which is an extremely important phenomenon for the modern industrial economy. It is a process whereby a reaction occurs faster than the uncatalysed reaction, the reaction being accelerated by the presence of a catalyst. Industrial catalysis can be divided into two broad types: heterogeneous and homogeneous. Most large-scale, industrially catalysed processes are of the former type, and the widespread recent application of catalysis to car emission control uses such solid catalysts in contact with the gas phase exhaust stream. For these kinds of reaction, the nature of the interface is crucial for the efficiency of the process. The nature of the top layer of atoms determines how fast a catalytic reaction takes place and small amounts of additives can reduce or enhance the reaction. The chapter then details the catalytic cycle and the adsorption on surfaces.
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Engel, Paul. "2. Making things happen—catalysis". In Enzymes: A Very Short Introduction, 12–26. Oxford University Press, 2020. http://dx.doi.org/10.1093/actrade/9780198824985.003.0002.
Testo completoAbstract (sommario):
‘Making things happen—catalysis’ examines chemical catalysis, considering what makes a reaction go or not go and how enzymes catalyse particular chemical reactions. This process is not unique to living systems, although enzymes are both more potent and more selective than catalysts encountered elsewhere in chemistry. A catalyst is an agent that speeds up a chemical reaction but remains unchanged itself at the end of the process. Since a catalyst is not altered or used up, it can be used over and over again.
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Haynes, Anthony. "Transition Metal Catalysed Methanol Carbonylation". In Contemporary Catalysis: Science, Technology, and Applications, 793–822. The Royal Society of Chemistry, 2017. http://dx.doi.org/10.1039/9781849739900-00793.
Testo completoAbstract (sommario):
The production of acetic acid, via the transition metal catalysed carbonylation of methanol, is well established as a major commercial application of homogeneous catalysis. Since the 1960s, when a cobalt-based catalyst was first used industrially by BASF, methanol carbonylation processes have continuously evolved and improved. Notably, Monsanto developed a rhodium/iodide catalyst system, variants of which have been operated by a number of companies. More recently, the journey down group 9 of the periodic table was completed by the commercialisation of an iridium/iodide based catalyst system by BP Chemicals. This chapter deals with the fundamental chemistry underlying these processes. The catalytic mechanisms are discussed in the context of the activity, selectivity and stability of rhodium and iridium catalysts, together with examples from the recent literature of attempts to improve catalyst behaviour. Approaches such as catalyst immobilisation, ligand modification and promoter effects are described. The importance of mechanistic understanding, accomplished through a range of experimental and theoretical studies, is emphasised.
Atti di convegni sul tema "Catalysie"
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Zhang, Aihua. "EXPERIMENTAL STUDY ON THE APPLICATION OF MACHINE LEARNING METHOD IN CATALYTIC MATERIALS". In Topics In Chemical & Material Engineering (TCME). Volkson Press, 2023. http://dx.doi.org/10.26480/smmp.01.2023.24.27.
Testo completoAbstract (sommario):
Machine learning has emerged as a powerful tool for analyzing complex data sets and making predictions in a wide range of applications, including catalysis. Bycombining statistical methods, algorithms, and computational power, machine learning can help identify patterns and relationships in catalytic systems that are difficult or impossible to discern using traditional approaches. This can lead to more efficient and effective catalyst design, optimization, and prediction of catalytic activity. Machine learning has already been successfully applied to various aspects of catalysis, including catalyst discovery, reaction mechanism identification, and kinetic modeling. The continued integration of machine learning with catalysis research holds great promise for advancing our understanding of catalytic systems and developing new and improved catalysts for important industrial processes.
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Furuya, Tomiaki, Terunobu Hayata, Susumu Yamanaka, Junji Koezuka, Toshiyuki Yoshine e Akio Ohkoshi. "Hybrid Catalytic Combustion for Stationary Gas Turbine: Concept and Small Scale Test Results". In ASME 1987 International Gas Turbine Conference and Exhibition. American Society of Mechanical Engineers, 1987. http://dx.doi.org/10.1115/87-gt-99.
Testo completoAbstract (sommario):
Catalytic combustion for gas turbine applications has been investigated. Its significant advantages in reducing combustor emissions, particularly nitrogen oxides (NOx), have been shown. One of the main problems in regard to developing a catalytic combustor is the durability of catalysts, because the catalysts deteriorate during high temperature operation, which is normal for current gas turbines and near future gas turbines. The hybrid catalytic combustion concept has advantages concerned with catalyst durability. This paper shows its concept and small scale test results. This hybrid catalytic combustion concept comprises the following steps; premix fuel and air for a catalyst-packed zone; operate catalysts at rather low temperatures, to prolong catalyst life; add fresh fuel into the stream at the catalyst-packed zone outlet, where gas phase combustion occurs completely without a catalyst; add dilution air into the stream at the gas phase combustion zone outlet with a by-pass valve. Experimental data and analyses indicated that this hybrid catalytic combustion has a potential of being applicable to current gas turbines (turbine inlet temperature is about 1100°C) and near future gas turbines (turbine inlet temperature is about 1300°C).
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Hui, K. S., Christopher Y. H. Chao, C. W. Kwong e M. P. Wan. "Performance of Transition Metal Ions Exchanged Zeolite 13X in Greenhouse Gas Reduction". In ASME 2007 International Mechanical Engineering Congress and Exposition. ASMEDC, 2007. http://dx.doi.org/10.1115/imece2007-41360.
Testo completoAbstract (sommario):
This study investigated the performance of multi-transition metal (Cu, Cr, Ni and Co) ions exchanged zeolite 13X catalysts on methane emission abatement, especially at methane level of the exhaust from natural gas fueled vehicles. Catalytic activity of methane combustion using multi-ions exchanged catalyst was studied under different parameters: mole % of metal loading, inlet velocity and inlet methane concentration at atmospheric pressure and 500 °C. Performance of the catalysts was investigated and explained in terms of the apparent activation energy, number of active sites and BET surface area of the catalyst. This study showed that the multi-ions exchanged catalyst outperformed the single-ions exchanged and the acidified 13X catalysts. Lengthening the residence time could also lead to higher methane conversion %. Catalytic activity of the catalysts was influenced by the mole % of metal loading which played important roles in affecting the apparent activation energy of methane combustion, active sites and also the BET surface area of the catalyst. Increasing mole % of metal loading in the catalyst decreased the apparent activation energy for methane combustion and also the BET surface area of the catalyst. In view of these, there existed an optimized mole % of metal loading where the highest catalytic activity was observed.
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Jayasuriya, Jeevan, Arturo Manrique, Reza Fakhrai, Jan Fredriksson e Torsten Fransson. "Experimental Investigations of Catalytic Combustion for High-Pressure Gas Turbine Applications". In ASME Turbo Expo 2006: Power for Land, Sea, and Air. ASMEDC, 2006. http://dx.doi.org/10.1115/gt2006-90986.
Testo completoAbstract (sommario):
Catalytic combustion has proven to be a suitable alternative to conventional flame combustion in gas turbines for achieving Ultra-Low Emission levels (ULE). In the process of catalytic combustion, it is possible to achieve a stable combustion of lean fuel/air mixtures which results in reduced combustion temperature in the combustor. The ultimate result is that almost no thermal-NOx is formed and the emissions of carbon monoxide and hydrocarbon emissions are reduced to single-digit limits. Successful development of catalytic combustion technology would lead to reducing pollutant emissions in gas turbines to ultra-low levels at lower operating costs. Since the catalytic combustion prevents the pollutant formations in the combustion there is no need for costly emission cleaning systems. High-quality experimental data of combustion catalyst operations at gas turbine working conditions and validated numerical models are essential tools for the design and development of catalytic gas turbine combustors. The prime objective of the work presented in this paper was to obtain catalytic operational data under said conditions. Experimental investigations were carried out to determine the operational data on different types of combustion catalysts against different fuel types at gas turbine operational conditions. A pilot-scale 100 k W high-pressure combustion test facility was used for the experimental investigations of catalytic combustion under real gas turbine conditions. Combustor pressure can be maintained at any desired level between 1 to 35 bars. The maximum combustion air supply is 100 g/s, which can be electrically preheated up to 600°C and humidified up to 30% of weight as required by test conditions. Catalysts used in the test facility are highly active noble metal catalysts for ignition purposes and thermally stable metal oxide catalysts for continuing reactions. Tests are conducted as the testing of single catalyst segments or combinations of several segments. The measurements taken are flow rates (air/fuel ratio) temperatures (inlet, surface and the outlet of each catalyst segment), pressure (combustor) and emissions of NOx, CO and UHC. This paper presents the design of the high-pressure catalytic combustion test facility and an experimental comparison of methane combustion over Pd on alumina and Pd/Pt (bi-metal) on alumina catalysts at varying pressure levels up to 20 bars. The catalysts concerned were cylindrical shaped (35 mm in diameter and 20 mm in height) honeycomb type fully coated catalysts. The results showed that the Pt/Pd on alumina catalysts is better in low temperature ignition and combustion stability over the Pd on alumina catalysts. Emission measurements showed that the fuel conversion over the tested Pt/Pd on alumina catalyst was around 10% while fuel conversion over a similar Pd on alumina catalyst (geometry and capacity) was only 4%. Fuel conversion rates showed the tendency to be further reduced (over the same catalysts) against increasing pressure.
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Wu, Quanwen, Wenhua Luo, Daqiao Meng, Jinchun Bao e Jingwen Ba. "High Efficient Detritiation Catalysts for Fusion Safety". In 2018 26th International Conference on Nuclear Engineering. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/icone26-81269.
Testo completoAbstract (sommario):
Tritium is indispensable to the fusion reactor engineering, and it must be seriously defended because of its radioactivity and permeability. The method of catalytic oxidation and absorption is the most widely used process for tritium cleanup so far, in which detritiation catalyst is of great importance. The poor stability caused by the agglomeration of noble metal limits the life of detritiation catalysts. Here, Anti–Ostwald Ripening is used to prepare single-atom detritiation catalysts S-Pt/Ce0.7Zr0.3O2 for tritium (HT, DT and T2) oxidation. Single-atom dispersed Pt ensures the catalytic activity and decreased the economic cost. The strong metal-support interaction (SMSI) keeps Pt from aggregating, thus increases the working life of catalyst. And Pd based catalyst supported by a cation ordered κ-Ce2Zr2O8 is prepared for tritiated methane (CH4-xTx) oxidation. Tritiated methane is mostly oxidized by Pd/κ-Ce2Zr2O8 at about 450 °C, which is at least 50 °C lower than normal catalysts (such as Pd/Al2O3).
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Kawakami, Takashi, Tomiaki Furuya, Yukio Sasaki, Toshiyuki Yoshine, Yutaka Furuse e Mitsunobu Hoshino. "Feasibility Study on Honeycomb Ceramics for Catalytic Combustor". In ASME 1989 International Gas Turbine and Aeroengine Congress and Exposition. American Society of Mechanical Engineers, 1989. http://dx.doi.org/10.1115/89-gt-41.
Testo completoAbstract (sommario):
This paper contains results of a structural feasibility study on honeycomb ceramic materials used for catalytic combustors in power gas turbines. Extruded cordierite honeycomb substrates are widely used as catalyst carriers in automotive exhaust systems, because of their excellent thermal shock resistance. For gas turbines, however, the ceramic catalyst carriers should retain the reliability at high temperature. In a hybrid catalytic combustor, which handles both catalysis and gas phases combustion, cordierite honeycomb structures (melt at 1445°C) can be adopted as the catalyst carrier, because the auxiliary gas phase combustion makes catalyst temperature lower than the conventional catalytic combustor. During this study, cordierite honeycomb (200 square cells/in2) tensile tests were carried out at high temperatures up to 1000°C. Using the finite element method, stresses in a cell wall were analyzed. The honeycomb cell wall mechanical strength was derived by comparing the experimental and analytical results. Also, combustor honeycomb cell stresses were calculated under typical oprerating conditions. Consequently, it was shown that it is sufficiently feasible to use the cordierite honeycomb structure as a catalyst carrier for hybrid catalytic combustors.
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Aktaş, Fatih, Kiran G. Burra e Ashwani K. Gupta. "Polyethylene Terephthalate Gasification Using CO2: Impact of SFCC Catalyst Contact Mode and Amount". In ASME 2024 Power Conference. American Society of Mechanical Engineers, 2024. http://dx.doi.org/10.1115/power2024-138167.
Testo completoAbstract (sommario):
Abstract The influence of spent fluid catalytic cracking (sFCC) catalyst on CO2-assisted gasification of polyethylene terephthalate (PET) was investigated at 900 °C using a semi-batch fixed-bed reactor. The effects of catalyst amount and contact mode on the release of synthesis gas (syngas) and char yields were studied. sFCC catalysis increased the maximum syngas yield by about 45% and energy yield by 60% in comparison to non-catalytic gasification. High syngas energy was extracted during CO2-assisted catalytic gasification, revealing the efficacy of sFCC and CO2 in PET conversion. The efficiency comparison with different amounts of catalyst revealed that the catalyst is more effective in a quasi-in-situ mode wherein the catalyst was located downstream of the feedstock sample at approximately 1.5 to 2 cm. This mode resulted in effective thermal cracking of the sample without posing limitations on the solid-solid heat transfer. Catalytic gasification using CO2 produced 1.2 times more combustible gas than the feedstock mass, implying CO2 consumption of more than 0.2 grams to create combustible gases (such as H2 and CO). The results reveal that co-utilization of PET wastes, sFCC catalyst, and CO2 can help provide energy-efficient carbon sequestration and waste management for sustainable energy recovery.
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Inoue, Shuhei, Takeshi Nakajima, Kazuya Nomura e Yoshihiro Kikuchi. "Selective Synthesis of Single-Walled Carbon Nanotubes by Blending Catalysts". In ASME/JSME 2007 Thermal Engineering Heat Transfer Summer Conference collocated with the ASME 2007 InterPACK Conference. ASMEDC, 2007. http://dx.doi.org/10.1115/ht2007-32524.
Testo completoAbstract (sommario):
Single-walled carbon nanotubes are considered the most attractive material and a lot of synthesis processes are developed. Among these synthesis processes chemical vapor deposition processes are considered to be most suitable for macroscopic production. In many CVD processes the alcohol catalytic CVD process can be the best process because it can produce very pure nanotubes without any purification. However, cobalt is essential as a catalyst that makes the flexibility of catalysts restricted. In this paper, our investigation mainly focused on as follows: The efficiency of combined catalysts with/without cobalt. The diameter distributions against catalysts density. The electrical states of catalysts near Fermi level. Consequently, almost all of cobalt containing catalysts worked well, and the diameter distributions were proportional to the particle size. Efficient catalysts had enough states around Fermi level and the cobalt-less efficient catalyst cluster model showed the similar density of state to the cobalt cluster. Thus, noticing to the DOS, other efficient catalysts can be discovered and the diameter distribution will be controllable by adjusting temperature, a catalyst size, and a catalyst combination without any complicated techniques and facilities.
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Manrique Carrera, Arturo, Jeevan Jayasuriya e Torsten Fransson. "Staged Lean Catalytic Combustion of Gasified Biomass for Gas Turbine Applications: An Experimental Approach to Investigate Performance of Catalysts". In ASME Turbo Expo 2013: Turbine Technical Conference and Exposition. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/gt2013-95339.
Testo completoAbstract (sommario):
Emission demands for gas turbine utilization will become more stringent in the coming years. Currently different techniques are used to reach low levels of NOx emissions. One possible solution is the Staged Lean Catalytic Combustion. In this concept a catalysts arrangement is used to generate high temperature combustion gases. The high temperature gases could be used to feed a second combustion stage in which more fuel is injected. In this work a series of experiments were performed at the Catalytic Combustion High Pressure Test Facility at the Royal Institute of Technology (KTH) in Sweden. The fuel used was a simulated gasified biomass and the catalytic combustor consisted of an arrangement of different catalysts, e.g. bimetallic, hexaaluminates, and perovskites catalysts. These were used as, ignition catalyst, medium temperature catalyst and high temperature catalyst respectively. The tests were performed between 5 and 13.5 bar, and the overall conversion varied between 60% and 70% and the temperature of flue gases could reach 750°C and contains high level of oxygen. The determining factor to control the exit gas temperature was the richness of the mixture (λ value). On the other hand, the increased pressure had a moderate negative effect in the overall fuel conversion. This effect is stronger at leaner mixtures compared to richer ones. Moreover, λ value and also pressure affected the temperature distribution along the reactor. The utilization of a lean catalytic combustion approach makes possible the use of a post catalytic combustion. In this region additional fuel is injected to fully burn the exiting gases and increase the exit temperature to the desired levels. This staged lean catalytic combustion approach could resemble moderate levels exhaust gas recirculation techniques and/or high air temperature combustion and it is also briefly examined in the present work.
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Karkanis, Anastasios N., Pantelis N. Botsaris e Panagiotis D. Sparis. "A Catalyst Surface Control Automation System for Emission Reduction During Cold Start". In ASME 2004 Internal Combustion Engine Division Fall Technical Conference. ASMEDC, 2004. http://dx.doi.org/10.1115/icef2004-0865.
Testo completoAbstract (sommario):
This paper presents and discusses experimental data obtained during test simulating the test cycle ECE-15 for a relatively simple method for the reduction of pollutant emissions during a cold start. During a cold start the volume of the exhaust gases is considerably smaller than the ones under full load. Therefore, only a small portion of the catalyst active surface is used to process the gases at the cold start phase. After the light-off at the initial surface the exhaust gases pass from the total catalytic surface which is already pre-heated from the first phase. The experimental results presented here indicate that there is a reduction of the pollutant emissions during the cold start of an engine. The developed system uses the 20% of the catalyst active surface during start-up and the rest of the catalyst surface after this phase, controlled by a proper automation system. At the cold start phase the system focusing the gas flow towards the center core of the monolith, so there is a quicker warm-up of the catalyst and a faster initiation of catalysis in this area. So when the remaining ceramic body of the catalytic converter is used, it is already warmed and the catalysis starts almost immediately.
Rapporti di organizzazioni sul tema "Catalysie"
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Olsen, Daniel, Bryan Hackleman e Rodrigo Bauza Tellechaea. PR-179-16207-R01 Oxidation Catalyst Degradation on a 2-Stroke Lean-Burn NG Engine - Washing. Chantilly, Virginia: Pipeline Research Council International, Inc. (PRCI), maggio 2019. http://dx.doi.org/10.55274/r0011586.
Testo completoAbstract (sommario):
Oxidation catalysts are often utilized to reduce carbon monoxide, formaldehyde, and volatile organic compounds in order to meet emissions regulations for large bore natural gas engines. These catalysts degrade over time and need to be replaced or regenerated to maintain emissions compliance. This work evaluates the effectiveness of catalyst regeneration, or catalyst washing. The evaluation is performed by utilizing field and laboratory slip streams combined with catalyst module performance (reduction efficiency) measurements and catalyst material surface analysis to quantify catalyst poisons.
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Stevens e Olsen. PR-179-12214-R01 CO Sensor Experimental Evaluation for Catalyst Health Monitoring. Chantilly, Virginia: Pipeline Research Council International, Inc. (PRCI), settembre 2014. http://dx.doi.org/10.55274/r0010827.
Testo completoAbstract (sommario):
Oxidation catalysts and three-way catalysts can be used to reduce the amount of CO present in engine exhaust. For 2-stroke lean-burn engines, the oxidation catalyst degrades over time be-cause of the buildup of poisons such as sulfur, zinc, phosphorous, and calcium. Three-way cata-lysts used with stoichiometric engines also degrade over time. Emissions analyzers are often used to evaluate the degradation of oxidation catalysts and three-way catalysts, but it can be very time consuming and expensive. Ideally, a simple sensor system would be beneficial for operating companies to determine if the catalyst were out of compliance according to normal operating standards. An ECM CO sensor and recording device was acquired for testing. The CO sensor system was evaluated for its ability to monitor post-catalyst CO concentration. The results show that this CO sensor system is ineffective at monitoring post-catalyst CO concentration.
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Badrinarayanan e Olsen. PR-179-11201-R01 Performance Evaluation of Multiple Oxidation Catalysts on a Lean Burn Natural Gas Engine. Chantilly, Virginia: Pipeline Research Council International, Inc. (PRCI), agosto 2012. http://dx.doi.org/10.55274/r0010772.
Testo completoAbstract (sommario):
Two-way catalysts or oxidation catalysts are the common after-treatment systems used on lean burn natural gas engines to reduce CO, VOCs and formaldehyde emissions. The study evaluates the performance of oxidation catalysts from commercial vendors for varying catalyst temperature and space velocity. For this study, a part of the exhaust from a Waukesha VGF-18 GL lean burn natural gas engine was flowed through a catalyst slipstream system to assess the performance of the oxidation catalysts. The slipstream is used to reduce the size of the catalysts and to allow precise control of temperature and space velocity. Analyzers used include Rosemount 5-gas emissions bench, Nicolet Fourier Transform Infra-Red spectrometer and HP 5890 Series II Gas Chromatograph. The oxidation catalysts were degreened at 1200oF (650oC) for 24 hours prior to performance testing. The reduction efficencies for the emission species varied among the oxidation catalysts tested from different vendors. Most oxidation catalysts showed over 90% maximum reduction efficiencies on CO, VOCs and formaldehyde. VOC reduction efficiency was limited by poor propane emission reduction efficiency at the catalyst temperatures tested. Saturated hydrocarbons such as propane showed low reduction efficiencies on all oxidation catalysts due to high activation energy. Variation in space velocity showed very little effect on the conversion efficiencies. Most species showed over 90% conversion efficiency during the space velocity sweep. Adding more catalyst volume may not increase the reduction efficiency of emission species. Varying cell density showed very little effect on performance of the oxidation catalysts. The friction factor correlation showed the friction factor for flow through a single channel is inversely proportional to cell density.
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Olsen e Neuner. PR-179-12207-R01 Performance Measurements of Oxidation Catalyst on an Exhaust Slipstream. Chantilly, Virginia: Pipeline Research Council International, Inc. (PRCI), agosto 2013. http://dx.doi.org/10.55274/r0010800.
Testo completoAbstract (sommario):
Oxidation catalysts are effective at reducing CO, formaldehyde, and VOCs as long as the catalyst temperature is above the light-off temperature for each species. It is important to understand the effects of temperature and space velocity on regulated species in order to effectively apply oxidation catalyst technology to lean burn engines, in particular 2-stroke engines that typically have lower exhaust temperatures. Various catalysts were tested on an exhaust slipstream coupled to a 4-stroke lean-burn engine which allows tests to be conducted at different temperatures and flow rates. The effect of the oxidation catalysts on NO2 and odor are also discussed.
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Olsen. PR-179-10203-R01 Characterization of Oxidation Catalyst Performance - VOCs and Temperature Variation. Chantilly, Virginia: Pipeline Research Council International, Inc. (PRCI), giugno 2012. http://dx.doi.org/10.55274/r0010753.
Testo completoAbstract (sommario):
Oxidation catalysts are typically specified to reduce carbon monoxide (CO), Hazardous Air Pollutants (HAPs) and/or Volatile Organic Compounds (VOCs) from lean-burn engines. The application of catalysts to HAPs and VOC destruction is more recent, so greater effort has been placed on optimizing for CO oxidation than HAPs or VOC oxidation. In general, the catalysts consist of a porous, high surface area -alumina carrier material on a ceramic (typically cordierite) or stainless steel substrate. Although the alumina has some effectiveness in oxidation at high temperature, its primary role here is to provide a high surface area support for a well dispersed layer of platinum (Pt) and/or palladium (Pd) which provides numerous catalytic sites for oxidation activity. This work extends the current knowledge-base for application of oxidation catalysts in three areas: (1) species specific removal efficiencies, (2) temperature dependence, and (3) space velocity.
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Swanson, Dr Larry, e Christopher Samuelson. PR-362-06208-R01 Evaluation of Byproduct Emissions from Gas Turbine SCR Catalyst. Chantilly, Virginia: Pipeline Research Council International, Inc. (PRCI), febbraio 2009. http://dx.doi.org/10.55274/r0010978.
Testo completoAbstract (sommario):
The primary objective of the test program was to evaluate byproduct emissions at steady state and transient operating conditions for two commercially available SCR catalysts used in gas turbine applications. Both NOX removal efficiency and ammonia slip behavior were also examined to validate expected catalyst trends and activity. Even though the study replicated expected field catalyst process conditions as well as possible (e.g., flue gas temperatures, space velocities, and inlet species concentrations), the data and results are from pilot-scale testing only, and consequently may differ from actual gas turbine field tests.
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Defoort, Willson e Olsen. L51849 Performance Evaluation of Exhaust Catalysts During the Initial Aging on Large Industrial Engines. Chantilly, Virginia: Pipeline Research Council International, Inc. (PRCI), giugno 2001. http://dx.doi.org/10.55274/r0011213.
Testo completoAbstract (sommario):
An investigation of catalyst performance during the initial aging process, providing insight into the deactivation rate of the catalyst and assisting in predicting the operational lifetime of the catalyst was preformed. The information gained through the test program provides a mechanism to assist in developing new technologies geared at reducing engine emission while providing improvements in efficiency, reliability, and operability for the aging industrial reciprocating engine fleet. Two natural gas lean burn engines, a 2-stroke, large bore slow speed and a 4-stroke medium bore medium speed, were operated at pre-determined conditions in conjunction with an oxidation catalyst. The aging process of the catalysts was observed. The research concluded that the catalyst performance is much lower than anticipated,particularly in relation to the aging process. During the aging process for the large bore 2-stroke engine (about 200 hours) the catalyst efficiency drops from 95% to 80% for CO and from 75% to 45% for CH2O. Results for the medium bore 4-stroke engine are better as a result of nearly 200°F higher catalyst temperatures. During aging (approximately 150 hours) the catalyst efficiencies are reduced from 99.2 to 97.7% for CO and from undetectable post catalyst levels (essentially 100% removal) to 67% for CH2O.
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Rioux, Robert M. Dynamic Chemical and Structural Changes of Heterogeneous Catalysts Observed in Real Time: From Catalysis-Induced Fluxionality to Catalytic Cycles. Fort Belvoir, VA: Defense Technical Information Center, novembre 2014. http://dx.doi.org/10.21236/ada613847.
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Bauza, Rodrigo, e Daniel Olsen. PR-179-20200-R01 Improved Catalyst Regeneration Process to Increase Poison Removal. Chantilly, Virginia: Pipeline Research Council International, Inc. (PRCI), giugno 2021. http://dx.doi.org/10.55274/r0012106.
Testo completoAbstract (sommario):
In this work, the details of catalyst poison deposition are studied, and new catalyst restoration methods are explored. Lubrication oil makes its way through the combustion chamber and into the exhaust system, depositing poisons onto the catalyst and degrading catalyst performance. To estimate the degradation rate of the units and to find the best restoration method, two identical alumina-platinum oxidation catalysts were used in a dual setting, combining a field degradation engine and a laboratory testing engine. In order to find the best restoration process, the combination of both baking and washing is tested with poison deposition and performance analysis, and a hydrogen reduction is tested for the restoration of the platinum crystallites. The units were aged, then restored with the industry-standard washing procedure, then aged again until reaching non-compliance with emissions standards, and then restored a second time with a modified version of the industry-standard washing process that combines baking and washing. There is a related webinar.
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Delgass, William Nicholas, Mahdi Abu-Omar, James Caruthers, Fabio Ribeiro, Kendall Thomson e William Schneider. Catalysis Science Initiative: Catalyst Design by Discovery Informatics. Office of Scientific and Technical Information (OSTI), luglio 2016. http://dx.doi.org/10.2172/1260972.
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