Kinetic studies of ethane dehydrogenation using carbon dioxide as mild oxidant over gallium aluminum mixed oxide
Date
2020
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Publisher
University of Delaware
Abstract
The development of a stable catalyst with high reactivity and selectivity for ethane dehydrogenation has been a long-studied topic in the field of energy research. The synergetic effect of the mixed gallium and aluminum oxide had been studied in this work. We identified an optimized composition of the mixed oxide prepared via the co- precipitation method at a surface Ga/Al ratio of 0.1 and conducted a series of kinetic measurements on different surface Ga loadings. The kinetic parameters are found to be sensitive to the surface composition. The reaction order on ethane is close to 1 for gamma- Al2O3 and surface Ga/Al ratios lower than 0.1, while it is close to 0.7 for ratio above 0.1 and pure Ga2O3. We also evaluated the effects of utilizing CO2 as the mild oxidant in ethane dehydrogenation. Based on the kinetic experiments as well as the catalyst characterization, we propose that CO2 does not directly participate in the ethane dehydrogenation. On the other hand, it serves as a mild oxidant oxidizing the carbonaceous components produced via side cracking reactions and extends the lifetime of the catalyst by decelerating the propagation of graphitic coke. ☐ The development of a stable catalyst with high reactivity and selectivity for ethane dehydrogenation has been a long-studied topic in the field of energy research. The synergetic effect of the mixed gallium and aluminum oxide has been investigated in this thesis: we identified an optimized composition of the mixed oxide prepared via the co-precipitation method at a surface Ga/Al ratio of 0.1 and conducted a series of kinetic measurements on different surface Ga loadings. The kinetic parameters are sensitive to the surface composition. The reaction order on ethane is close to 1 for gamma- Al2O3 and surface Ga/Al ratios lower than 0.1, while it is close to 0.7 for ratio above 0.1 and pure Ga2O3. We also evaluated the effects of utilizing CO2 as the mild oxidant in ethane dehydrogenation. Based on the kinetic experiments as well as the catalyst characterization, we propose that CO2 does not directly participate in the ethane dehydrogenation. On the other hand, it serves as a mild oxidant oxidizing the carbonaceous components produced via side cracking reactions and extends the lifetime of the catalyst by decelerating the propagation of graphitic coke.
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Keywords
Aluminum oxide, Ethane dehydrogenation, Gallium oxide, Kinetics