Download or read book Density Functional Theory and Kinetic Study of Catalytic Methane Conversion and Ammonia Decomposition written by Domoina Fanomezana Holiharimanana and published by . This book was released on 2023 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The price fluctuation and depletion of crude oil have led to the fervent interest in finding alternatives that can satisfy our increasing need for energy. In the past decades, two primary approaches are seen as promising ways to remedy our dependence on crude oil: first, the use of natural gas, primarily methane, to produce high-value hydrocarbons, and second, the use of ammonia as a hydrogen carrier. In this dissertation, we used density functional theory (DFT) calculation and kinetic modeling to investigate methane activation and C-C coupling on WC as well as the ammonia decomposition over the CoNi alloy surface. From our methane conversion project, we investigated the reactivity of W-terminated WC(0001) and WC(112 ̅0) surface toward methane activation and conversion to produce C2 moieties using DFT. We first calculate the intermediates binding energies and activation and reaction energies of methane dissociation. We found that WC(112 ̅0) is better at dissociating the first C-H bond than WC(0001). Our results also indicate that the surface is likely populated by (CH)ads species. The mobility of (CH)ads species on both surfaces allows the possibility of C-C coupling, resulting in a precursor for higher hydrocarbon formation. Our results also demonstrate that the WC(0001) surface favors the production of the (C2H2)ads species, whereas the WC(112 ̅0) surface dissociates CHx completely, resulting in coke formation. Thus, methane dissociates readily on the WC surfaces whereas the formation of the C2 species is sensitive to the surface structure. The DFT study on ammonia decomposition has been performed in close collaboration with the experimental study. A highly active catalyst consisting of CoNi alloy nanoparticles well-dispersed on a MgO-CeO2-SrO mixed oxide support with potassium promotion exhibited a performance matching that of the Ru-based catalysts. Extensive characterization in combination with the DFT results revealed that the CoNi alloy surface and metal/oxide interfaces are the active sites for catalytic decomposition of ammonia. Moreover, the much improved catalytic activity stems mainly from the presence of interface where the recombinative desorption of nitrogen has been greatly enhanced. These have been demonstrated by examining the detailed elementary steps of ammonia decomposition on the Co, Ni, Co2Ni, CoNi2 (111) surfaces and at the CeO2/Co2Ni interface. We calculated the binding energies of intermediates and the activation energies of each elementary step in ammonia decomposition. We found that on the Co, Ni, Co2Ni, CoNi2 surfaces, N-N bond formation is the rate-determining step, with the CoNi alloy surfaces having a lower activation energy than the pure metal surfaces. Over the CeO2/Co2Ni interface, however, N-H bond dissociation becomes rate-determining. The high catalytic activity at the CeO2/Co2Ni interface originates from the localized charge polarization due to alloying and the presence of the oxide which drastically facilitates N2* formation. We then integrated the DFT-calculated adsorption and activation energies in the microkinetic modeling of ammonia decomposition on the Co, Co2Ni, CoNi2, and Ni surfaces, focusing on the alloying effect. Two cases were investigated: ammonia decomposition in the 1) absence and 2) presence of product re-adsorption. In both cases, we determined the turnover frequencies, the apparent activation energies, the steady-state coverages, the degree of rate control, and the reaction orders. Our results show that in both cases, the alloys have higher catalytic performance than the pure metals. We also found that as the temperature increases, ammonia decomposition switches from being limited by N-N (and N-NH) bond formation to N-H bond dissociation. This change of mechanism is predicted to occur at lower temperatures on the alloy surfaces. In the case of hydrogen re-absorption, the surface H* adatom retards the last N-H bond-breaking step, resulting in the high coverage of NH* species on the surfaces, making N-NH coupling an alternative pathway for N2 formation. Furthermore, our microkinetic results show that alloying Ni with Co reduces the effect of hydrogen inhibition at high hydrogen partial pressures. In summary, this dissertation provides information for the design of efficient catalysts toward methane conversion and ammonia decomposition.

Download or read book Density Functional Theory Studies on the Structural Evolution and Catalytic Reactivity of Molybdenum based Catalysts for Methane Conversion written by Tianyu Zhang and published by . This book was released on 2019 with total page 216 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Direct Hydroxylation of Methane written by Kazunari Yoshizawa and published by Springer Nature. This book was released on 2020-10-29 with total page 167 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book focuses on theoretical and computational studies by the editor’s group on the direct hydroxylation of methane, which is one of the most challenging subjects in catalyst chemistry. These studies of more than 20 years include gas-phase reactions by transition-metal oxide ions, enzymatic reactions by two types of methane monooxygenase (soluble and particulate MMO), catalytic reactions by metal-exchanged zeolites, and methane C–H activation by metal oxide surfaces. Catalyst chemistry has been mostly empirical and based on enormous experimental efforts. The subject of the title has been tackled using the orbital interaction and computations based on extended Hückel, DFT, and band structure calculations. The strength of the theoretical studies is in the synergy between theory and experiment. Therefore, the group has close contacts with experimentalists in physical chemistry, catalyst chemistry, bioinorganic chemistry, inorganic chemistry, and surface chemistry. This resulting book will be useful for the theoretical analysis and design of catalysts.

Download or read book Metallic Nanostructures written by Yujie Xiong and published by Springer. This book was released on 2014-10-31 with total page 304 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book details the design for creation of metal nanomaterials with optimal functionality for specific applications. The authors describe how to make desired metal nanomaterials in a wet lab. They include an overview of applications metal nanomaterials can be implemented in and address the fundamentals in the controlled synthesis of metal nanostructures.

Download or read book Fundamental Mechanistic Studies of Formic Acid Decomposition on Transition Metals written by Sha Li and published by . This book was released on 2015 with total page 382 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Ab Initio DFT Modeling of the Oxidation of Methane on Transition Metal Catalysts written by George Psofogiannakis and published by . This book was released on 2007 with total page 358 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Studies in Reaction Kinetics Density Functional Theory and Catalysis written by Thomas A. Manz and published by . This book was released on 2005 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Plasma Catalysis written by Annemie Bogaerts and published by MDPI. This book was released on 2019-04-02 with total page 248 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.

Download or read book Theoretical Investigation of Catalytic Methane Cracking and Carbon Nanotube Growth written by Jingde Li and published by . This book was released on 2014 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Computational Study of Heterogeneous Catalytic Systems Kinetic and Structural Insights from Density Functional Theory written by Reisel Millán Cabrera and published by . This book was released on 2020 with total page 290 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Computational Insight Into Catalytic Hydrogenation of Nitrogen and Carbon Monoxide written by Andrew J. Medford and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Computational modeling is becoming an increasingly important tool in the design of heterogeneous catalysts. This thesis explores recent advances in the atomic-scale computational design of catalytic materials. Nitrogen hydrogenation is used to illustrate the core concepts in part I, and these concepts are applied to a wide range of carbon monoxide hydrogenation reactions in part II. Nitrogen hydrogenation, or ammonia synthesis, is one of the most important catalytic processes ever discovered. Industrial-scale ammonia synthesis enabled the mass production of fertilizers which are now used to produce approximately half of the global food supply. Ammonia synthesis is also a well-studied and relatively simple catalytic reaction, and has served as a bellwether reaction for computation in heterogeneous catalysis. Part I of this thesis revisits the ammonia synthesis reaction. Chapter 2 discusses the importance of ammonia synthesis and heterogeneous catalysis in general. Chapter 3 introduces density functional theory (DFT), the workhorse method in quantum-mechanical studies of catalytic materials. Chapter 4 examines how DFT energies can be combined with kinetic modeling in order to gain insight into catalytic trends and design strategies for ammonia synthesis. Chapter 5 applies a novel method for uncertainty quantification and error propagation in order to demonstrate the robustness of the computational catalyst design against uncertainty in the DFT calculations. Hydrogenation of carbon monoxide (CO) is a complex process with many potentially valuable products including methane, methanol, and higher hydrocarbons and alcohols. These reactions will play an increasingly important role in the global economy as fossil resources are exhausted and replaced by more sustainable synthetic fuels. Part II of the thesis applies many of the concepts introduced in part I to CO hydrogenation reactions. Chapter 6 examines the production of ethanol from synthesis gas (CO and H2) and applies the techniques of chapter 4 in order to map the activity and selectivity trends across transition-metal (211) surfaces. Several alloys are identified as promising catalysts for selective ethanol synthesis, including CoCu and CoPt alloys. Chapter 7 combines computational methods and experiments to provide insight into the complex selectivity patterns of CO hydrogenation over rhodium catalysts, indicating that the reaction is structure sensitive and that rhodium catalysts are intrinsically selective toward acetaldehyde rather than ethanol. Chapter 8 and chapter 9 examine CO hydrogenation over non-metallic catalysts (Mo2C and ZnO), revealing the importance of surface termination and the fundamentally different surface reactivity of transition-metal compounds.

Download or read book Understanding Catalytic Activity Trends for NO Decomposition and CO Oxidation Using Density Functional Theory and Microkinetic Modeling written by Hanne Falsig and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Iron and Cobalt Catalysts written by Wilson D. Shafer and published by MDPI. This book was released on 2020-06-23 with total page 414 pages. Available in PDF, EPUB and Kindle. Book excerpt: Since the turn of the last century when the field of catalysis was born, iron and cobalt have been key players in numerous catalysis processes. These metals, due to their ability to activate CO and CH, haev a major economic impact worldwide. Several industrial processes and synthetic routes use these metals: biomass-to-liquids (BTL), coal-to-liquids (CTL), natural gas-to-liquids (GTL), water-gas-shift, alcohol synthesis, alcohol steam reforming, polymerization processes, cross-coupling reactions, and photocatalyst activated reactions. A vast number of materials are produced from these processes, including oil, lubricants, waxes, diesel and jet fuels, hydrogen (e.g., fuel cell applications), gasoline, rubbers, plastics, alcohols, pharmaceuticals, agrochemicals, feed-stock chemicals, and other alternative materials. However, given the true complexities of the variables involved in these processes, many key mechanistic issues are still not fully defined or understood. This Special Issue of Catalysis will be a collaborative effort to combine current catalysis research on these metals from experimental and theoretical perspectives on both heterogeneous and homogeneous catalysts. We welcome contributions from the catalysis community on catalyst characterization, kinetics, reaction mechanism, reactor development, theoretical modeling, and surface science.

Download or read book Industrial Applications of Molecular Simulations written by Marc Meunier and published by CRC Press. This book was released on 2016-04-19 with total page 413 pages. Available in PDF, EPUB and Kindle. Book excerpt: The field of quantum and molecular simulations has experienced strong growth since the time of the early software packages. A recent study, showed a large increase in the number of people publishing papers based on ab initio methods from about 3,000 in 1991 to roughly 20,000 in 2009, with particularly strong growth in East Asia. Looking to the futu

Download or read book AB Initio Study of Organometallic Phthalocyanine Catalysts for the Conversion of Methane to Methanol written by Chase Ferrone and published by . This book was released on 2022 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Methane’s low energy density and contribution to the greenhouse gas effect has emphasized the importance of converting methane to methanol. In this work, organometallic, single transition metal active site heterogeneous phthalocyanine catalysts have been designed to activate methane in a single step process. Copper and cobalt phthalocyanines, supported by TiN and BN substrates, have been studied using ab initio density functional theory (DFT) implemented in the Vienna ab initio software package (VASP). Titanium nitride (TiN) has potential as a substrate due to its metallic-like behavior and favorable optical properties.

Download or read book Reviews in Computational Chemistry Volume 31 written by Abby L. Parrill and published by John Wiley & Sons. This book was released on 2018-11-06 with total page 368 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Reviews in Computational Chemistry series brings together leading authorities in the field to teach the newcomer and update the expert on topics centered on molecular modeling, such as computer-assisted molecular design (CAMD), quantum chemistry, molecular mechanics and dynamics, and quantitative structure-activity relationships (QSAR). This volume, like those prior to it, features chapters by experts in various fields of computational chemistry. Topics in Volume 31 include: Lattice-Boltzmann Modeling of Multicomponent Systems: An Introduction Modeling Mechanochemistry from First Principles Mapping Energy Transport Networks in Proteins The Role of Computations in Catalysis The Construction of Ab Initio Based Potential Energy Surfaces Uncertainty Quantification for Molecular Dynamics

Download or read book The Fundamentals of Density Functional Theory written by and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 205 pages. Available in PDF, EPUB and Kindle. Book excerpt: Density functional methods form the basis of a diversified and very active area of present days computational atomic, molecular, solid state and even nuclear physics. A large number of computational physicists use these meth ods merely as a recipe, not reflecting too much upon their logical basis. One also observes, despite of their tremendeous success, a certain reservation in their acceptance on the part of the more theoretically oriented researchers in the above mentioned fields. On the other hand, in the seventies (Thomas Fermi theory) and in the eighties (Hohenberg-Kohn theory), density func tional concepts became subjects of mathematical physics. In 1994 a number of activities took place to celebrate the thirtieth an niversary of Hohenberg-Kohn-Sham theory. I took this an occassion to give lectures on density functional theory to senior students and postgraduates in the winter term of 1994, particularly focusing on the logical basis of the the ory. Preparing these lectures, the impression grew that, although there is a wealth of monographs and reviews in the literature devoted to density func tional theory, the focus is nearly always placed upon extending the practical applications of the theory and on the development of improved approxima tions. The logical foundadion of the theory is found somewhat scattered in the existing literature, and is not always satisfactorily presented. This situation led to the idea to prepare a printed version of the lecture notes, which resulted in the present text.