In Situ IR Spectroscopic Studies of the CO Oxidation Reaction Over a Ruthenium Model Catalyst PDF Download

Author: Attila Farkas
Publisher:
ISBN:
Category :
Languages : en
Pages : 210

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Author: Chundi Cao
Publisher:
ISBN:
Category :
Languages : en
Pages :

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Catalytic partial oxidation (CPO) has received considerable interest recently both as a way to utilize remote natural gas resources and to provide H[subscript]2 for a fuel cell. Studies on the reactions at lower temperatures and transient conditions were performed, which can provide insights on the mechanism of CPO at high reactions, particularly on the role of the chemical and physical state of the noble metal catalyst. In this work, ignition of methane CPO on Pt/Al[subscript]2O[subscript]3 and Rh/Al[subscript]2O[subscript]3 catalysts and methanol CPO on Pt/Al[subscript]2O[subscript]3 catalysts were studied using in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). The ignition mechanism study of CH4 on Pt/Al[subscript]2O[subscript]3 showed that oxygen mainly covers the surface until ignition. Competition between the two reactants is assumed. The heat of adsorption of oxygen is a key factor for ignition of the methane partial oxidation reaction on Pt/Al[subscript]2O[subscript]3. The ignition mechanism on Rh/Al[subscript]2O[subscript]3 was found to be different from Pt/Al[subscript]2O[subscript]3. The oxidation state of the catalyst changed significantly as the temperature was raised towards the ignition. An oxidized rhodium state, Rh[superscript]n+, progressively formed as the temperature was increased while Rh[superscript]0 decreased. In addition, a greater amount of Rh[supercript]n+ was found when the oxygen concentration in the feed was higher. From these results, it is hypothesized that ignition of methane CPO on Rh/Al[subscript]2O[subscript]3 is related to the accumulation of the Rh[superscript]n+ state. Dissociation adsorption of methanol occurs on both Al2O3 and Pt/Al[subscript]2O[subscript]3. It is suggested that formate was one of the important intermediates in the reaction pathway. Oxygen species play a key role in the formation of formate on the catalysts, and it also affects the product composition. Formate mainly decomposed into CO, which is the dominant source for CO[subscript]2 production in the reactions at higher temperatures.

Author: Annemie Bogaerts
Publisher: MDPI
ISBN: 3038977500
Category : Technology & Engineering
Languages : en
Pages : 248

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Plasma catalysis is gaining increasing interest for various gas conversion applications, such as CO2 conversion into value-added chemicals and fuels, N2 fixation for the synthesis of NH3 or NOx, methane conversion into higher hydrocarbons or oxygenates. It is also widely used for air pollution control (e.g., VOC remediation). Plasma catalysis allows thermodynamically difficult reactions to proceed at ambient pressure and temperature, due to activation of the gas molecules by energetic electrons created in the plasma. However, plasma is very reactive but not selective, and thus a catalyst is needed to improve the selectivity. In spite of the growing interest in plasma catalysis, the underlying mechanisms of the (possible) synergy between plasma and catalyst are not yet fully understood. Indeed, plasma catalysis is quite complicated, as the plasma will affect the catalyst and vice versa. Moreover, due to the reactive plasma environment, the most suitable catalysts will probably be different from thermal catalysts. More research is needed to better understand the plasma–catalyst interactions, in order to further improve the applications.

Author: Erin Melissa Duffy
Publisher:
ISBN:
Category :
Languages : en
Pages : 0

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This work focuses on a well-known molecular water oxidation catalyst, [Ru(tpy)(bpy)(OH2)]2, the simplest of a large family of ruthenium-based catalysts. Although there have been numerous chemical investigations of this catalyst's activity in the past decade, direct structural information and corresponding molecular level insight had not been achieved. Presented here are some of the first spectroscopic studies of this catalyst and isolated intermediates of the reaction pathway, where previously proposed molecular structures are confirmed and key intermolecular interactions that influence reactivity are probed First, the [Ru(tpy)(bpy)(OH2)]2 catalyst is investigated in the form of controlled, size-selected water clusters in the gas phase, which simulate the interaction of the catalyst in aqueous solution, its typical operating phase. Using infrared spectroscopy, we probe the OH stretches of the aqua ligand and surrounding water molecules, which elucidates the strength of these interactions. With support from theoretical calculations, we gain insight into structural changes that occur upon solvation. These structural details provide valuable molecular level information about how the catalyst activates water molecules to initiate the catalytic cycle. Next, the first electrochemical intermediate of the catalytic cycle, [Ru(tpy)(bpy)(OH)]2+, is discussed. Similarly to the aforementioned work, we probe key solvent interactions of this species that forms after a one electron, one proton oxidation step. By comparing the results of these experiments to those of the previous study, we learn how the complex's reactivity changes after the first reaction step in the cycle and the implications for its progression through further oxidation steps. Finally, the proposed final intermediate of the water oxidation cycle, [Ru(tpy)(bpy)(O2)]2+, is investigated. This species consists of an O2 molecule bound to the Ru center, and its release as the final reaction product also triggers the regeneration of the initial catalyst. The binding orientation of the O2 moiety had previously been debated due to a lack of experiments that probed this complex directly, and disagreement between the indirect information acquired experimentally and theoretical calculations. Here, we exploit our mass-selective technique and isotopic substitution of O2 to definitively identify the O-O stretch in the far infrared region and confirm the bidentate interaction of O2 with Ru.

Author: Andrzej Koleżyński
Publisher: Springer
ISBN: 3030013553
Category : Science
Languages : en
Pages : 529

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This book reviews various aspects of molecular spectroscopy and its application in materials science, chemistry, physics, medicine, the arts and the earth sciences. Written by an international group of recognized experts, it examines how complementary applications of diverse spectroscopic methods can be used to study the structure and properties of different materials. The chapters cover the whole spectrum of topics related to theoretical and computational methods, as well as the practical application of spectroscopic techniques to study the structure and dynamics of molecular systems, solid-state crystalline and amorphous materials, surfaces and interfaces, and biological systems. As such, the book offers an invaluable resource for all researchers and postgraduate students interested in the latest developments in the theory, experimentation, measurement and application of various advanced spectroscopic methods for the study of materials.

Author: Shi-Gang Sun
Publisher: Elsevier
ISBN: 0080489060
Category : Science
Languages : en
Pages : 559

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In-Situ Spectroscopic Studies of Adsorption at the Electrode and Electrocatalysis is a new reference on in-situ spectroscopic techniques/applications, fundamentals of electrocatalysis at molecule level, and progresses within electrochemical surface science. Presenting both essential background knowledge at graduate level and original research within the fields of spectroscopy, electrochemistry, and surface science. Featuring 15 chapters by prominent worldwide scholars, based on their recent progress in different aspects of in-situ spectroscopy studies, this book will appeal to a wide audience of scientists. In summary this book is highly suitable for graduates learning basic concepts and advanced applications of in-situ spectroscopy, electrocatalysis and electrode adsorptions. * Written by the most active scientists in the fields of spectroscopy, electrochemistry and surface science* Essential background knowledge for graduate students* A modern reference of cutting-edge scientific research

Author: Kwang-Ho Park
Publisher:
ISBN:
Category : Carbon monoxide
Languages : en
Pages : 522

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Author: Lin Gao
Publisher:
ISBN:
Category : Automobiles
Languages : en
Pages : 172

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Author: Daniel J. Dwyer
Publisher:
ISBN:
Category : Language Arts & Disciplines
Languages : en
Pages : 384

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Presents an excellent overview of the impact of surface science on the field of catalysis. Explores the exciting new advances in surface science and catalysis, which for the first time allow for direct spectroscopic and kinetic observation of surface reactions. Twenty-two chapters cover fundamental aspects of catalytic reactions at surfaces, applications of surface probes to the study of catalytic reactions and kinetics, and novel aspects of catalytic reactions at surfaces. Highlights the success of surface science techniques in the study of industrially important catalytic processes, including hydrogenation of CO to produce hydrocarbons and methanol, the oxidation of methane to methanol, and conversions of CO to carbon dioxide.

Author: Piet W.N.M. van Leeuwen
Publisher: Springer Science & Business Media
ISBN: 0306469472
Category : Science
Languages : en
Pages : 291

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In the last decade there have been numerous advances in the area of rhodium-catalyzed hydroformylation, such as highly selective catalysts of industrial importance, new insights into mechanisms of the reaction, very selective asymmetric catalysts, in situ characterization and application to organic synthesis. The views on hydroformylation which still prevail in the current textbooks have become obsolete in several respects. Therefore, it was felt timely to collect these advances in a book. The book contains a series of chapters discussing several rhodium systems arranged according to ligand type, including asymmetric ligands, a chapter on applications in organic chemistry, a chapter on modern processes and separations, and a chapter on catalyst preparation and laboratory techniques. This book concentrates on highlights, rather than a concise review mentioning all articles in just one line. The book aims at an audience of advanced students, experts in the field, and scientists from related fields. The didactic approach also makes it useful as a guide for an advanced course.