Catalysis For C1 Chemistry Oxidative Coupling Of Methane Using Nanofiber Catalysts And Discovery Of Catalysts For Atmospheric Reduction Of Co2 To Methanol
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Catalysis For C1 Chemistry Oxidative Coupling Of Methane Using Nanofiber Catalysts And Discovery Of Catalysts For Atmospheric Reduction Of Co2 To Methanol
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Author : Bahman Zohour
language : en
Publisher:
Release Date : 2017
Catalysis For C1 Chemistry Oxidative Coupling Of Methane Using Nanofiber Catalysts And Discovery Of Catalysts For Atmospheric Reduction Of Co2 To Methanol written by Bahman Zohour and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2017 with categories.
The goal of this research is to explore novel catalytic material and systems for effective conversion of C1 feed. Catalysis of C1 chemistry is of critical importance for the clean production of fuels and chemicals and future energy sustainability. Herein, two processes were studied: In the first section, a comprehensive study of oxidative coupling of methane (OCM) using novel nanofiber catalysts of mixed metal oxides was undertaken and in the second section, direct catalytic conversion of carbon dioxide (CO2) to methanol was studied, which resulted in discovery of a superior catalytic system for CO2 hydrogenation to methanol. Section 1: Utilization of natural gas as an alternate chemical feedstock to petroleum has been a highly desirable but difficult goal in industrial catalysis. Accordingly, there has been a substantial interest in the oxidative coupling of methane (OCM), which allows for the direct catalytic conversion of methane into economically valuable C2+ hydrocarbons. OCM is a complex reaction process involving heterogeneous catalysis intricately coupled with gas phase reactions; hence, despite decades' worth of research, it has yet to be commercialized. The lack of progress in OCM is primarily due to the following reasons: 1. The absence of a highly active and robust catalyst that can operate at lower temperatures; and 2. Our inadequate understanding of the underlying detailed chemical kinetics mechanism (DCKM) of the OCM process, which impedes the undertaking of quantitative simulations of novel reactor configurations and/or operating strategies. To address these issues, we undertook the following program of studies: 1. Further improved the synthesis of novel nanofiber catalysts by electrospinning, building on the early discovery that La2O3-CeO2 nanofibers were highly active and robust OCM catalysts; 2. Applied our novel microprobe sampling system to OCM reactors for the acquisition of spatially resolved species concentration and temperatures profiles within the catalytic zone. Our novel sampling approach led to the important discovery that H2 is produced very early in the OCM catalytic zone, an observation that was completely missed in all prior studies. The application of our novel microprobe system to a dual-bed OCM reactor also demonstrated the feasibility to significantly improve C2+ product yields to 21% (from 16% for single bed) which we plan to further improve by considering more sequential beds; 3. Outlined development and validation of new generation of DCKM for the OCM process using the high-information content of spatial concentration profiles obtained in part 2. Most importantly, to improve the current DCKM literature by considering surface reactions that result in early H2 formation. Validated DCKM represent highly valuable numerical tools that allow for the prediction of the OCM performance of different reactor configurations operating under a broad range of conditions, e.g. high pressures, porous wall reactors etc. Consequently, this new generation of comprehensive DCKM based on the sampling profiles, detailed in this report, will be of considerable use in improving the yields of useful products in the OCM process; 4. Explore novel conditions that include oxygen-feed distributed packed bed OCM reactors and coupled catalytic and non-thermal plasma OCM reactors, again to further push the yields for useful C2+ products. The details of the proposed approach for implementing such reactor configurations and development of a new generation of DCKM for the OCM process is outlined in the future work, Chapter 4, of section 1 of the report. Section 2: Direct catalytic conversion of carbon dioxide to liquid fuels and basic chemicals, such as methanol, using solar-derived hydrogen at or near ambient pressure is a highly desirable goal in heterogeneous catalysis. When realized, this technology will pave the way for a sustainable society together with decentralized power generation. Here we report a novel class of holmium (Ho) containing multi-metal oxide Cu catalysts discovered through the application of high-throughput methods. In particular, ternary systems of Cu-GaOx-HoOy > Cu-CeOx-HoOy ~ Cu-LaOx-HoOy supported on -Al2O3 exhibited superior methanol production (10x) with less CO formation than previously reported catalysts at atmospheric pressure. Holmium was shown to be highly dispersed as few-atom clusters, suggesting that the formation of tri-metallic sites could be the key for the promotion of methanol synthesis by Ho.
Solar Energy Mediated Methane Conversion Over Nanometal And Semiconductor Catalysts
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Author : Hui Song
language : en
Publisher: Springer Nature
Release Date : 2020-11-30
Solar Energy Mediated Methane Conversion Over Nanometal And Semiconductor Catalysts written by Hui Song and has been published by Springer Nature this book supported file pdf, txt, epub, kindle and other format this book has been release on 2020-11-30 with Science categories.
This book demonstrates that solar energy, the most abundant and clean renewable energy, can be utilized to drive methane activation and conversion under mild conditions. The book reports that coupling solar energy and thermal energy can significantly enhance methane conversion at mild temperatures using plasmonic nanometal-based catalysts, with a substantial decrease in apparent activation energy of methane conversion. Furthermore, this book, for the first time, reports the direct photocatalytic methane oxidation into liquid oxygenates (methanol and formaldehyde) with only molecular oxygen in pure water at room temperature with high yield and selectivity over nanometals and semiconductors (zinc oxide and titanium dioxide). These findings are a big stride toward methane conversion and inspire researchers to develop strategies for efficient and selective conversion of methane to high-value-added chemicals under mild conditions.
Catalysis And The Mechanism Of Methane Conversion To Chemicals
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Author : Toshihide Baba
language : en
Publisher: Springer Nature
Release Date : 2020-04-18
Catalysis And The Mechanism Of Methane Conversion To Chemicals written by Toshihide Baba and has been published by Springer Nature this book supported file pdf, txt, epub, kindle and other format this book has been release on 2020-04-18 with Science categories.
This book introduces various types of reactions to produce chemicals by the direct conversion of methane from the point of view of mechanistic and functional aspects. The chemicals produced from methane are aliphatic and aromatic hydrocarbons such as propylene and benzene, and methanol. These chemicals are created by using homogeneous catalysts, heterogeneous catalysts such as zeolites, and biocatalysts such as enzymes. Various examples of methane conversion reactions that are discussed have been chosen to illustrate how heterogeneous and homogenous catalysts and biocatalysts and/or their reaction environments control the formation of highly energetic species from methane contributing to C-C and C-O bond formation.
Metal Oxide Nanofiber Catalysis
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Author : Daniel Patrick Noon
language : en
Publisher:
Release Date : 2015
Metal Oxide Nanofiber Catalysis written by Daniel Patrick Noon and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2015 with categories.
The synthesis of solids with finely turned nanostructures that offer superior catalytic performance is a major challenge in heterogeneous catalysis for gas phase reactions. Industrial catalysts are almost universally composed of quasi-spherical nanoparticles, or powders plagued with particle agglomeration, migration and sintering problems that lead to deactivation. In this work, quasi-cylindrical nanofibers are electrospun and extensively utilized for the oxidative coupling of methane (OCM), as well as for propylene epoxidation and the catalytic partial oxidation (CPO) of methane. Electrospun nanofibers of metal oxides may be tuned to have high surface areas but typically possess no internal porosity, reducing diffusion limitations that would lengthen the exposure of target intermediate oxidation products to unselective catalysis. Additionally, experiments and density functional theory (DFT) studies have previously shown that pentagonal Ag nanowires exhibit higher selectivity than conventional particles in ethylene epoxidation since their surfaces are terminated mainly by the (100) surface facet rather than the lowest energy (111) facet that dominates particles. Hence, nanofibers may elevate catalytic performance in broad range of partial oxidation reaction schemes. Research into the oxidative coupling of methane, or, the catalytic conversion of methane to ethane and ethylene by molecular oxygen, almost exclusively utilized powders and failed to result in viable catalyst despite four decades of intense, global efforts. Accordingly, the use of catalytic nanofibers provides a potentially fruitful path towards a solution. Here, nanofiber fabrics of La2O3-CeO2 were electrospun and used in fixed bed OCM reactors to achieve 70% selectivity and 16% yield for C2+ hydrocarbons at a CH4/O2 feed ratio of 7 and remarkably low feed temperature of 470 ?C. Powders of La2O3-CeO2 documented in the literature exhibit similar selectivity and yield, but with the feed at 715 ?C. The electrospun fabrics used in this research were found to have dense nanofibers of diameters typically within the 20 - 200 nm range and, accordingly, surface areas of 10 - 20 m2/g as well as thinner fibers tending towards both higher C2+ selectivity and CH4 conversion. While performing reaction engineering studies using the aforementioned fabrics, it was found that designing reactors comprising dual catalytic La2O3-CeO2 fabric beds with inter-stage O2 injection and cooling pushes yields to 21%. Moreover, a novel in-situ microprobe sampling technique for acquiring spatial temperature and concentration profiles within these OCM reactors was developed, providing a means to formulate and validate detailed chemical kinetic mechanisms. This has led to the discovery of prompt H2 formation in OCM, a feature previously unidentified that may break ground in mechanism refinement. Additionally, spatial concentration and temperature profiles were acquired in fixed bed reactors comprising La2O3-CeO2 fabrics doped with varying levels of Ir and fed CH4/O2 mixtures to gain insight into the transition from OCM to the catalytic partial oxidation of methane. It was found that, in general, OCM and CPO appear to occur both in parallel and sequentially in a fixed bed, evidenced by the temporary rise and subsequent destruction of C2+ hydrocarbons when the catalyst is doped with 0.05 wt% Ir. Clearly, this sampling technique has broad applicability in catalysis research over a limitless number of reactions for the acquisition of comprehensive data sets potentially useful for formulating and refining detailed chemical kinetic mechanisms (DCKM), thus furthering a fundamental understanding of the catalysis and advancing faster towards the development of higher performing materials.
Plasma Catalysis
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Author : Annemie Bogaerts
language : en
Publisher: MDPI
Release Date : 2019-04-02
Plasma Catalysis written by Annemie Bogaerts and has been published by MDPI this book supported file pdf, txt, epub, kindle and other format this book has been release on 2019-04-02 with Technology & Engineering categories.
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.
Catalytic Conversion Of Carbon Monoxide And Methane Over Metal And Metal Oxide Catalysts
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Author : Wenchi Liu
language : en
Publisher:
Release Date : 2018
Catalytic Conversion Of Carbon Monoxide And Methane Over Metal And Metal Oxide Catalysts written by Wenchi Liu and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2018 with categories.
Catalysis is of vital importance in a wide range of areas including energy processing and chemical production. Catalytic conversion of C1 sources such as carbon monoxide and methane to make hydrocarbon fuels and oxygenated products has far reaching implications especially in the context of the gradual depletion of crude oil resource and the potential surge in the natural gas production in the coming decades. The control over reaction activity and selectivity for the conversion CO and CH4 in the Fischer–Tropsch synthesis and oxidative coupling of methane (OCM) have received tremendous attention and have been proved challenging. This dissertation focuses on the catalytic conversion of CO (Fischer–Tropsch synthesis) using supported cobalt based bimetallic nanoparticle model catalysts and the oxidative coupling of methane with noble metal promoted metal oxide catalysts. Using colloidal synthesis, a series of cobalt based bimetallic nanoparticles Co–M (M = Mn, Ru, Rh, and Re) with well-defined sizes, shapes, and compositions were obtained. Detailed synthesis procedures were presented and key synthetic parameters were discussed. The as-synthesized nanoparticles were subjected to extensive in-situ X-ray spectroscopy studies using ambient pressure X-ray photoelectron spectroscopy (AP-XPS) and X-ray absorption spectroscopy (XAS) under catalytic relevant conditions. Composition wise, the results indicate the surface concentration of Co on the as-synthesized Co–M bimetallic particles is slightly less than the bulk atomic Co %. While oxidation treatment led to a slight increase of the surface Co, major effect was seen after the reduction treatment where surface segregation of the second metal resulted in a drastic decrease of the surface Co content. The effect is more pronounced at elevated reduction temperatures. Under reaction conditions, the surface compositions remained similar to those after the reduction treatment at high temperatures. Among the bimetallics tested, the Co–Mn system is relatively less susceptible to surface reconstructions induced by oxidation and reduction treatments. In addition, the reducibility of Co was also shown to be modified depending on the second metal present and Re was proved to be most efficient in leading to a facile reduction of Co. Catalytic performance of the bimetallic catalysts supported on mesoporous silica MCF–17 indicates a positive effect in the catalytic activity for Co–Rh and Co–Mn systems, while Co–Re and Co–Cu showed decreased activity. Less pronounced promotion effect of the second metal on the product distribution was observed with only a slight increase in the selectivity towards C5+ products. The selectivities for CH4 and C5+ of the various Co–M bimetallic catalysts generally resemble those of pure Co catalysts. Although in extremely low selectivity, alcohols were also formed with Co–Rh and Co–Cu bimetallic catalysts. The appearance of longer chain alcohol such as propanol, which was not present for pure Co catalysts, is an evidence for potential synergistic promotion. For oxidative coupling of methane (OCM), the promotion effect of noble metals (Pt, Ir, and Rh) on the performance of MnxOy-Na2WO4/MCF–17 catalysts was investigated. The introduction of noble metals had little effect on the surface area and phase composition of the original catalyst but led to a more reduced nature of the surface oxide species. Catalytic study revealed an enhanced selectivity towards both C2 and C3 hydrocarbons as compared to the undoped MnxOy-Na2WO4/MCF–17 catalyst in the order of Rh-doped > Ir-doped > Pt-doped samples together with a lower olefin to paraffin ratio. A more optimized strength of interaction between the carbon intermediates and the catalyst surface was suggested, which in combination with the improved reducibility of Mn and W species are believed to be responsible for the improved performance. In addition, monodispersed leaf-like manganese–tungsten–oxide (Mn–W–Ox) nanoparticles and hydroxylated hexagonal boron nitride (h-BN) were synthesized and used as novel catalysts in OCM reaction. Preliminary results indicate that the MCF–17 supported Mn–W–Ox nanoparticle catalyst showed a CH4 conversion of 5.4% and C2 selectivity of 42% with good stability over time. On the other hand, hydroxylated h-BN exhibited good activity (~20% CH4 conversion) with moderate selectivity towards C2 hydrocarbons (20%–30%). However, the hydroxylated h-BN catalysts faced serious deactivation, which was not eliminated by lowering the reaction temperature or the oxygen concentration in the reaction gas feed.
Mechanistic Studies On The Oxidative Coupling Of Methane
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Author : Chunlei Shi
language : en
Publisher:
Release Date : 1993
Mechanistic Studies On The Oxidative Coupling Of Methane written by Chunlei Shi and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1993 with categories.
Methane Conversion By Oxidative Processes
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Author : Wolf
language : en
Publisher: Springer
Release Date : 2013-11-13
Methane Conversion By Oxidative Processes written by Wolf and has been published by Springer this book supported file pdf, txt, epub, kindle and other format this book has been release on 2013-11-13 with Technology & Engineering categories.
A reasonable case could be made that the scientific interest in catalytic oxidation was the basis for the recognition of the phenomenon of catalysis. Davy, in his attempt in 1817 to understand the science associated with the safety lamp he had invented a few years earlier, undertook a series of studies that led him to make the observation that a jet of gas, primarily methane, would cause a platinum wire to continue to glow even though the flame was extinguished and there was no visible flame. Dobereiner reported in 1823 the results of a similar investigation and observed that spongy platina would cause the ignition of a stream of hydrogen in air. Based on this observation Dobereiner invented the first lighter. His lighter employed hydrogen (generated from zinc and sulfuric acid) which passed over finely divided platinum and which ignited the gas. Thousands of these lighters were used over a number of years. Dobereiner refused to file a patent for his lighter, commenting that "I love science more than money." Davy thought the action of platinum was the result of heat while Dobereiner believed the ~ffect ~as a manifestation of electricity. Faraday became interested in the subject and published a paper on it in 1834; he concluded that the cause for this reaction was similar to other reactions.
Catalytic Oxidative Coupling Of Methane To C2 Hydrocarbon
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Author : Mohd Ridzuan Nordin
language : en
Publisher:
Release Date : 1989
Catalytic Oxidative Coupling Of Methane To C2 Hydrocarbon written by Mohd Ridzuan Nordin and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1989 with Catalysis categories.
Photocatalytic Conversion Of Methane And Reduction Of Co2 With H2o
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Author : Xiang Yu
language : en
Publisher:
Release Date : 2019
Photocatalytic Conversion Of Methane And Reduction Of Co2 With H2o written by Xiang Yu and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2019 with categories.
Photocatalysis is one of the key technologies for clean energy and environmental applications. The number of applications based on photocatalysis has increased dramatically for the past two decades. Photocatalytic activation of C-H bonds is an emerging field. Methane is a promising source of energy with a huge reserve and is considered to be one of the alternatives to non-renewable petroleum resources because it can be converted to valuable hydrocarbon feedstocks and hydrogen through appropriate reactions. However, due to its high stability, high energy is usually consumed for its conversion, which remains a problem to be solved. Methane conversion and reaction mechanism occurring on metal-heteropolyacid-titania nanocomposites were investigated in Chapters 3 and 4. Oxidation of methane has been carried out for more than a century. Since oxygen is a very reactive molecule, methane can react very rapidly with molecular oxygen and is prone to total oxidation till CO2. Therefore, it is difficult to obtain a desired product with high yield and high selectivity. We report here direct and selective photocatalytic highly-selective oxidation of methane to carbon monoxide under ambient conditions. The composite catalysts on the basis of zinc, tungstophosphoric acid and titania exhibit exceptional performance in this reaction, high carbon monoxide selectivity and quantum efficiency of 7.1% at 362 nm. The reaction is consistent with the Mars-Van Krevelen type sequence and involves formation of the surface methoxy-carbonates as intermediates and zinc oxidation-reduction cycling. In the past few decades, extensive research has focused on the direct conversion of methane to alcohols or higher hydrocarbons. The current processes of converting methane to alcohols or olefins are complex and expensive, because they require an intermediate step of reforming methane to syngas. Although the direct conversion of methane to more valuable products has significant environmental and potential commercial value, there is no commercial scale process available. We uncovered highly selective (>90%) quantitative photochemical direct conversion of methane to ethane at ambient temperature over silver-heteropolyacid-titania nanocomposites. The ethane yield from methane reaches 9 % on the optimized materials. High quantum efficiency, high selectivity and significant yield of ethane combined with excellent stability are major advantages of methane quantitative synthesis from methane using the photochemical looping approach. The rise in atmospheric carbon dioxide and the depletion of fossil fuel reserves have raised serious concerns about the subsequent impact of CO2 on the global climate and future energy supply. The use of abundant solar energy to convert carbon dioxide into fuel, such as carbon monoxide, methane or methanol, solves both problems simultaneously and provides a convenient method of energy storage. Chapter 5 addresses a new efficient catalyst for selective CO2 to CO conversion. The zinc containing phosphotungstic acid-titania nanocomposites exhibited exceptional high activity reaching 50 μmol CO/g·h and selectivity (73%) in the CO2 photocatalytic reduction to CO in the presence of water. The in-situ IR experiments suggest that reaction involves zinc bicarbonates containing hydroxyl groups. The decomposition of these zinc bicarbonate species under irradiation leads to the selective production of carbon monoxide and oxygen. In photocatalytic reactions, the difference in catalyst morphology usually has a significant effect on the photocatalytic performance. Chapter 6 studied the effect of monoclinic bismuth vanadate (BiVO4) crystals with controlled ratio of {010} and {110} facets for photocatalytic reduction of CO2 by H2O. The reaction under irradiation is significantly enhanced by selective photo-deposition of Cu and Co co-catalysts over different facets providing Z-scheme charge flow.