Platinum-tin Catalysts For Dehydrogenation Of Mixed Light Hydrocarbons Into Isobutene

Butene is an important raw material in petrochemical industry. Particularly, the most valuable butene is isobutene, becanse of its lively nature.Nowadays, most of the isobutene is obtained as by-product of gasoline production by both thermal and catalytic cracking processes. Due to the growing demand for isobutene, the research of butane dehydrogenation to isobutene becomes a key research field in petrochemical industry. The paper studied the process of using mixed light hydrocarbons as raw material to produce isobutene with Pt-Sn/Al₂O₃ as a catalyst. In this paper, the effects of active components, supports and metal oxide promoters on the structure and the mixed light hydrocarbons dehydrogenation performance of Pt-Sn/Al₂O₃ catalyst were investigated. Moreover, the Pt-Sn-Ag/Al₂O₃ catalyst's reaction conditions were discussed.Firstly, a series of metal oxide promoters (Sn, Zn, Fe) can improve the performance of Pt/γ-Al₂O₃ for butane dehydrogenation. Fe can significantly improve the stability of the catalyst, Zn has a prominent role to improve the selectivity of isobutene, and Sn can improve the yield of isobutene, while the catalyst can maintain good stability. And the Pt content and Pt/Sn atomic ratio of Pt-Sn/γ-Al₂O₃ on the dehydrogenation performance were studied.Secondly, the different supports and metal oxide promoters can affect performance on Pt-Sn/γ-Al₂O₃ catalysts in butane dehydrogenation. In the support of Pt-Sn/γ-Al₂O₃ catalyst, the bigger pore volume and average pore size can help to improve the conversion of dehydrogenation catalysts, a wide pore size distribution is favorable to improve the selectivity of the catalyst. The addition of MgO can reduce the surface acidity in the support of Al₂O₃, and improve dehydrogenation selectivity and stability.In this work, a series of metal oxide promoters (Fe, La, Ag, Zn ang Mg) can improve the performance of Pt-Sn/γ-Al₂O₃ for butane dehydrogenation. Metal oxides promoters can greatly increase the disperstion and stability of Pt particles, and help to to maintain the oxidative state of tin in reaction, which may further increase the stability of catalyst. The addition of Mg and Ag, can significantly suppress the formation of coke on the catalyst and greatly promote the selectivity of isobutene, and improve the catalyst stability and selectivity.Finally, the dehydrogenation performance of the novel three components catalysts Pt-Sn-Ag/γ-Al₂O₃ were studied. The results indicated that when T=600℃and GHSV=1000 h^-1, the performance of Pt-Sn-Ag/γ-Al₂O₃ was the best. The deactivation and regeneration of catalyst were discussed by comparison with the fresh catalyst.