Propane dehydrogenation on single site gallium on silica catalyst
Light alkane dehydrogenation is gaining increasing importance due to the discovery of shale gas. Gallium based catalysts such as Ga/HZSM-3 and Ga2O3 have been used to dehydrogenate propane to propylene. However, the exact nature of the active site for propane dehydrogenation on Gallium based catalysts is still debated in literature. This work is aimed at understanding the nature of active site in Ga/SiO2 catalyst for propane dehydrogenation. The Ga/SiO2 catalyst is active and selective for propane dehydrogenation reaction. It is shown that Ga +3 site co-ordinated with four O atoms is the most active form of Gallium during the propane dehydrogenation reaction. The catalyst is subjected to different pretreatment conditions and it is observed that the pretreatment with H2 at 650°C results in lower initial rates for propane dehydrogenation. The Ga/SiO2 catalyst is studied using operando X-Ray Absorption Spectroscopy, in-situ Fourier Transform Infrared Spectroscopy and X-Ray Photoelectron Spectroscopy. Reduction of the catalyst at 650°C resulted in the formation of a reduced Gallium species which results in lower rates of propane dehydrogenation. These reduced Gallium species were found to be unstable under conditions of propane dehydrogenation and get reoxidized to Ga+3. It is proposed that the reduced Gallium species has the form of Gallium hydride which is less active for propane dehydrogenation.
Ribeiro, Purdue University.
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