Methane-to-methanol Conversion Over Zeolite Cu-SSZ-13, and Its Comparison with the Selective Catalytic Reduction of NOx with NH31 PDF Download
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Languages : en
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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: 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: 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: James Temple Cobb
Publisher:
ISBN:
Category : Hydrocarbons
Languages : en
Pages : 40
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Author: Vladimir Arutyunov
Publisher: Elsevier
ISBN: 0444632514
Category : Technology & Engineering
Languages : en
Pages : 321
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Direct Methane to Methanol: Foundations and Prospects of the Process offers a state-of-the-art account of one of the most interesting and potentially commercial technologies for direct conversion of natural gas into valuable chemicals. The book thoroughly explains the complex and unusual chemistry of the process, as well as possible applications for direct methane to methanol (DMTM). It covers topics involving thermokinetics, pressure, direct oxidation of heavier alkanes, and more, and provides detailed appendices with experimental data and product yields. This book provides all those who work in the field of gas processing and gas chemistry with the theory and experimental data to develop and apply new processes based on direct oxidation of natural gas. All those who deal with oil and natural gas production and processing will learn about this promising technology for the conversion of gas into more valuable chemicals. - Reviews more than 350 publications on high-pressure, low-temperature oxidation of methane and other gas phase hydrocarbons - Contains rare material available for the first time in English - Explains the reasons of previous failure and outlines the way forward for commercial development of the conversion technology - Presents a deep theoretical knowledge of this complex conversion process
Author: Amy J. Knopp
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Category :
Languages : en
Pages :
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Author: Unni Engedahl
Publisher:
ISBN:
Category :
Languages : en
Pages : 36
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Author: Eduardo E. Wolf
Publisher: Springer
ISBN:
Category : Science
Languages : en
Pages : 566
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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.
Author: Yu Shao
Publisher:
ISBN:
Category :
Languages : en
Pages : 254
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