Effect of Phase Composition of Tungsten Carbide on its Catalytic Activity for Toluene Hydrogenation
Commercially important hydrogenation reactions make use of precious noble metal catalysts which are becoming increasingly scarce, and the search for capable alternative catalysts prevails. Transition metal carbides of group IV-VI metals show similar catalytic behavior to platinum and are $103/kg low...
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ndltd-UMASS-oai-scholarworks.umass.edu-masters_theses_2-21742021-10-28T05:22:18Z Effect of Phase Composition of Tungsten Carbide on its Catalytic Activity for Toluene Hydrogenation Rane, Aditya Commercially important hydrogenation reactions make use of precious noble metal catalysts which are becoming increasingly scarce, and the search for capable alternative catalysts prevails. Transition metal carbides of group IV-VI metals show similar catalytic behavior to platinum and are $103/kg lower in price than the precious metal catalysts. Tungsten carbide, studied in this work, can form in different stoichiometries and phase compositions depending upon synthesis methods. Synthesis of high surface area tungsten carbide with control over its phase composition remains a challenge currently. In this work, the novel isothermal synthesis method of tungsten carbide (WC, W2C) in a CH4/H2 carburization atmosphere with synthesis temperature and presence or absence of a silica support in the catalyst precursor (WO3) as process variables was investigated. The amounts of CO and H2O formed during synthesis corresponded to the amount of oxygen in the WO3 precursor. The catalysts were further characterized by X-ray diffraction to determine phase composition and crystallite size, by scanning electron microscopy to determine morphology, and by CO chemisorption to determine metallic surface area. X-ray diffraction analysis indicated the carbide catalysts to contain W2C, WC, and metallic W phases. The use of a silica-supported precursor favored the formation of a nearly phase pure, high surface area W2C rich catalyst whereas high synthesis temperature and absence of silica precursor favored formation of a low surface area WC rich catalyst. Further, the catalysts were tested for steady state activity at a W/F (weight catalyst/toluene feed rate) of 0.20-0.30 h-1, addition of H2 to a total pressure of 21 bar absolute and 250 °C, and the effect of phase composition and surface area on the activity was studied. This work resulted in the successful synthesis of 4 tungsten carbide catalysts with varying phase compositions and surface areas and correlation of their compositions and surface areas with their corresponding toluene hydrogenation activities. 2021-10-20T17:58:38Z text application/pdf https://scholarworks.umass.edu/masters_theses_2/1133 https://scholarworks.umass.edu/cgi/viewcontent.cgi?article=2174&context=masters_theses_2 http://creativecommons.org/licenses/by/4.0/ Masters Theses ScholarWorks@UMass Amherst Tungsten carbide catalyst synthesis phase composition toluene hydrogenation structure-activity catalyst characterization Catalysis and Reaction Engineering |
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Tungsten carbide catalyst synthesis phase composition toluene hydrogenation structure-activity catalyst characterization Catalysis and Reaction Engineering |
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Tungsten carbide catalyst synthesis phase composition toluene hydrogenation structure-activity catalyst characterization Catalysis and Reaction Engineering Rane, Aditya Effect of Phase Composition of Tungsten Carbide on its Catalytic Activity for Toluene Hydrogenation |
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Commercially important hydrogenation reactions make use of precious noble metal catalysts which are becoming increasingly scarce, and the search for capable alternative catalysts prevails. Transition metal carbides of group IV-VI metals show similar catalytic behavior to platinum and are $103/kg lower in price than the precious metal catalysts. Tungsten carbide, studied in this work, can form in different stoichiometries and phase compositions depending upon synthesis methods. Synthesis of high surface area tungsten carbide with control over its phase composition remains a challenge currently. In this work, the novel isothermal synthesis method of tungsten carbide (WC, W2C) in a CH4/H2 carburization atmosphere with synthesis temperature and presence or absence of a silica support in the catalyst precursor (WO3) as process variables was investigated. The amounts of CO and H2O formed during synthesis corresponded to the amount of oxygen in the WO3 precursor. The catalysts were further characterized by X-ray diffraction to determine phase composition and crystallite size, by scanning electron microscopy to determine morphology, and by CO chemisorption to determine metallic surface area. X-ray diffraction analysis indicated the carbide catalysts to contain W2C, WC, and metallic W phases. The use of a silica-supported precursor favored the formation of a nearly phase pure, high surface area W2C rich catalyst whereas high synthesis temperature and absence of silica precursor favored formation of a low surface area WC rich catalyst. Further, the catalysts were tested for steady state activity at a W/F (weight catalyst/toluene feed rate) of 0.20-0.30 h-1, addition of H2 to a total pressure of 21 bar absolute and 250 °C, and the effect of phase composition and surface area on the activity was studied. This work resulted in the successful synthesis of 4 tungsten carbide catalysts with varying phase compositions and surface areas and correlation of their compositions and surface areas with their corresponding toluene hydrogenation activities. |
author |
Rane, Aditya |
author_facet |
Rane, Aditya |
author_sort |
Rane, Aditya |
title |
Effect of Phase Composition of Tungsten Carbide on its Catalytic Activity for Toluene Hydrogenation |
title_short |
Effect of Phase Composition of Tungsten Carbide on its Catalytic Activity for Toluene Hydrogenation |
title_full |
Effect of Phase Composition of Tungsten Carbide on its Catalytic Activity for Toluene Hydrogenation |
title_fullStr |
Effect of Phase Composition of Tungsten Carbide on its Catalytic Activity for Toluene Hydrogenation |
title_full_unstemmed |
Effect of Phase Composition of Tungsten Carbide on its Catalytic Activity for Toluene Hydrogenation |
title_sort |
effect of phase composition of tungsten carbide on its catalytic activity for toluene hydrogenation |
publisher |
ScholarWorks@UMass Amherst |
publishDate |
2021 |
url |
https://scholarworks.umass.edu/masters_theses_2/1133 https://scholarworks.umass.edu/cgi/viewcontent.cgi?article=2174&context=masters_theses_2 |
work_keys_str_mv |
AT raneaditya effectofphasecompositionoftungstencarbideonitscatalyticactivityfortoluenehydrogenation |
_version_ |
1719491447735975936 |