Isobutane Dehydrogenation over Metal (Fe, Co, and Ni) Oxide and Sulfide Catalysts: Reactivity and Reaction Mechanism

• Published in: ChemCatChem 2014-08, Vol.6 (8), p.2305-2314
• Main Authors: Wang, Guowei, Gao, Chuancheng, Zhu, Xiaolin, Sun, Yanan, Li, Chunyi, Shan, Honghong
• Format: Article
• Language: English
• Subjects: dehydrogenation; isobutane; metal oxides; metal sulfides; Sulfur; supported catalysts
• ISSN: 1867-3880; 1867-3899
• DOI: 10.1002/cctc.201402173

Silica‐supported metal oxide and sulfide catalysts of Fe, Co, and Ni were evaluated comparatively for the catalytic dehydrogenation of isobutane. The results of the activity test and temperature‐programmed reduction of hydrogen characterization indicate that metal oxides, except Fe2O3, are easily reduced to metal ensembles, which are extremely active for alkane hydrogenolysis and lead to the formation of a considerable amount of methane and coke. However, the dehydrogenation performance was significantly improved after sulfidation treatment. The introduction of sulfur affects the catalysts in two ways: one is the geometric effect, which dilutes the aggregated metallic species and reduces hydrogenolysis activity, and the other is the electronic effect, which facilitates the desorption of olefin and increases the product selectivity. Moreover, the reaction mechanism is explored by using the proposed model of the interaction between isobutane and sulfide catalysts. Finally, sulfur loss and partial coke deposition are determined to be the main reasons for catalyst deactivation. Benefits of sulfur: The introduction of sulfur into metal oxide catalysts dilutes and separates the aggregated metallic species. As a result, hydrogen atoms in isobutane molecules bond with sulfur atoms neighboring metallic species on the catalyst surface and thus the carbon–hydrogen bonds weaken and break. Subsequently, isobutene and hydrogen are released to the gas phase as final products.