Direct Conversion of Methane-to-methanol in Cu-exchanged Small-pore Zeolites PDF Download
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Author: Unni Engedahl
Publisher:
ISBN:
Category :
Languages : en
Pages : 36
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Author: Unni Engedahl
Publisher:
ISBN:
Category :
Languages : en
Pages : 36
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Author: Bahar Ipek
Publisher:
ISBN: 9781369351538
Category : Copper
Languages : en
Pages : 223
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The adverse impact of atmospheric greenhouse gases and our heavy dependence on petroleum for materials and energy are an urgent call for sustainable methods in energy generation and chemical synthesis. Hydrogen fuel-cell vehicles are zero emission cars that run on compressed hydrogen stored in tanks at 70 MPa. Due to the volume and safety concerns, there is a need for a safer, lightweight and economical onboard hydrogen storage system with a target capacity of 5.5 wt.%. At the same time, efficient utilization of the increasingly important shale gas via methane conversion into valuable and more easily transportable liquid products in small-scales could help reduce our dependence on petroleum. Current methods for converting methane into chemicals involve synthesis gas production, economical only at large scale. Therefore, direct methane conversion into value added products such as methanol has been an important goal for the field of catalysis. There have been developments in selective methanol production using Cu-exchanged zeolites at mild conditions, however the low yields and the absence of a selective catalytic process leave a large room for research in this field. In this thesis, both challenges were investigated using Cu-exchanged small-pore zeolites with crystallographic and spectroscopic experiments focused on the material Cu-SSZ-13. H2 adsorption capacity that more than triple the capacity of the best metal-organic-frameworks (MOFs), reaching 0.05 wt.% were achieved at 30 °C and 1 atm using Cu(I)-SSZ-13 and Cu(I)-[B]-SSZ-13 with adsorption enthalpy around -20 kJ mol-1. The strong interaction of Cu(I)-SSZ-13 with H2 was also monitored using IR spectroscopy and neutron diffraction. In the second part of the thesis, Cu-exchanged SSZ-13, -SSZ-16 and SSZ-39 were tested for methanol formation and found to form methanol in quantities that are more than double the amounts produced by Cu-ZSM-5, the most investigated alternative. The active sites for methane activation on Cu-SSZ-13 and Cu-SSZ-39 were identified using optical spectroscopy and theory, while the optimum conditions for the formation of higher concentrations of the active site were reported. Finally, a new catalytic methanol production process was investigated using CH4, N2O, and steam on Cu-SSZ-13, and conditions for achieving higher selectivity were suggested.
Author: Kimberly Tam Dinh
Publisher:
ISBN:
Category :
Languages : en
Pages : 169
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The selective conversion of methane to liquid oxygenated compounds is a grand challenge in catalysis. Although natural gas can be processed industrially in large-scale facilities, new catalytic processes are required that economically directly convert methane to liquid products in small-scale units to exploit highly abundant but difficult-to-access gas reserves. Our group recently reported the first instance of a continuous, gas phase catalytic process for the direct conversion of methane to methanol using copper-exchanged zeolites by feeding only methane, water, and oxygen at 473 K. While this continuous system is an attractive route for the mild conversion of methane to value-added products, fundamental understanding of the reaction pathway and active site is necessary to engineer improved catalysts and an improved process. Thus, my thesis has investigated the fundamental kinetics and active site requirements for continuous partial methane oxidation and using this knowledge to design an improved process. First, a reaction pathway and a [Cu-O-Cu]2+ motif as the active site were identified for the selective catalytic conversion of methane to methanol. Kinetic analysis on copper-exchanged SSZ-13 zeolites across a range of Cu loadings and Al spatial distributions revealed the reaction pathway is initiated by rate-limiting C-H bond scission of methane. Water is kinetically inconsequential, but required for methanol desorption. Carbon dioxide is generated from the sequential over oxidation of partially oxidized intermediates and downstream methanol oxidation. Selective partial oxidation was achieved with catalyst samples of high Al content and moderate Cu content (Cu/cage
Author: Amy J. Knopp
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Author: Unni Engedahl
Publisher:
ISBN: 9789179055653
Category : Density functionals
Languages : en
Pages :
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Author: Karthik Narsimhan
Publisher:
ISBN:
Category :
Languages : en
Pages : 147
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As production of shale gas has increased greatly in the United States, the amount of stranded shale gas that is flared as carbon dioxide has become significant enough to be considered an environmental hazard and a wasted resource. The conversion of methane, the primary component of natural gas, into methanol, an easily stored liquid, is of practical interest. However, shale wells are generally inaccessible to reforming facilities, and construction of on-site, conventional methanol synthesis plants is cost prohibitive. Capital costs could be reduced by the direct conversion of methane into methanol at low temperature. Existing strategies for the partial oxidation of methane require harsh solvents, need exotic oxidizing agents, or deactivate easily. Copper-exchanged zeolites have emerged as candidates for methanol production due to high methanol selectivity (> 99%), utilization of oxygen, and low reaction temperature (423-473 K). Despite these advantages, three significant shortcomings exist: 1) the location of surface intermediates on the zeolite is not well understood; 2) methane oxidation is stoichiometric, not catalytic; 3) there are few active sites and methanol yield is low. This work addresses all three shortcomings. First, a new reaction pathway is identified for methane oxidation in copper-exchanged mordenite zeolites using tandem methane oxidation and Koch carbonylation reactions. Methoxy species migrate away from the copper active sites and adsorb onto Bronsted acid sites, signifying spillover on the zeolite surface. Second, a process is developed as the first instance of the catalytic oxidation of methane into methanol at low temperature, in the vapor phase, and using oxygen as the oxidant. A variety of commercially available copper-exchanged zeolites are shown to exhibit stable methanol production with high methanol selectivity. Third, catalytic methanol production rates and methane conversion are further improved 100- fold through the synthetic control of copper speciation in chabazite zeolites. Isolated monocopper species, directed through the one-pot synthesis of copper-exchanged chabazite zeolites, correlates with methane oxidation activity and is likely the precursor to the catalytic site. Together, these synthetic methods provide guidelines for catalyst design and further improvements in catalytic activity.
Author: I. Chorkendorff
Publisher: John Wiley & Sons
ISBN: 3527605649
Category : Science
Languages : en
Pages : 469
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Until now, the literature has offered a rather limited approach to the use of fundamental kinetics and their application to catalytic reactions. Subsequently, this book spans the full range from fundamentals of kinetics and heterogeneous catalysis via modern experimental and theoretical results of model studies to their equivalent large-scale industrial production processes. The result is key knowledge for students at technical universities and professionals already working in industry. '... such an enterprise will be of great value to the community, to professionals as well as graduate and undergraduate students attempting to move into the field of modern catalysis and kinetics. I strongly recommend you publish this book based on the proposal.' - Prof. Dr. G. A. Samorjai, University of California 'Both authors are well respected specialists, with a very long record of original top-quality work and an international reputation. A book from these authors will be considered an authoritative piece of work, I definitely support this project and I am looking forward to use the book when published.' - Prof. Dr. D. E. Resasco, University of Oklahoma 'I wholly support the proposed project. The authors are very competent young colleagues and there is a real need for such a textbook' - Prof. Dr. G. Ertl, Fritz-Haber-Institut, Max-Planck-Gesellschaft, Berlin
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: Joaquín Pérez Pariente
Publisher: Springer
ISBN: 3319989057
Category : Science
Languages : en
Pages : 316
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This volume provides the reader with the most up-to-date and relevant knowledge on the reactivity of metals located in zeolite materials, either in framework or extra-framework positions, and the way it is connected with the nature of the chemical environment provided by the host. Since the first report of the isomorphous substitution of titanium in the framework of zeolites giving rise to materials with unusual catalytic properties, the incorporation of many other metals have been investigated with the aim for developing catalysts with improved performance in different reactions. The continuous expansion of the field, both in the variety of metals and zeolite structures, has been accompanied by an increasing focus on the relationship between the reactivity of metal centers and their unique chemical environment. The concepts covered in this volume are of interest to people working in the field of inorganic and physical chemistry, catalysis and chemical engineering, but also for those more interested in theoretical approaches to chemical reactivity. In particular the volume is useful to postgraduate students conducting research in the design, synthesis and catalytic performance of metal-containing zeolites in both academic and application contexts.
Author: James Temple Cobb
Publisher:
ISBN:
Category : Hydrocarbons
Languages : en
Pages : 40
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