Effect of Sn addition on n-butane dehydrogenation over alumina-supported pt catalysts prepared by co-impregnation and sol-gel methods

Abstract

n-Butane dehydrogenation, Butadiene production n-Butane dehydrogenation was investigated over alumina-supported Pt catalysts modified with Sn. Preparation of this catalyst by conventional co-impregnation method with HH 2PtCl 6 and SnCl 2 mixed solution (Pt 3Sn/Al 2O 3 catalyst), resulted in considerable loss of amount of Sn during calcination. Therefore, SnO 2-Al 2O 3 was prepared by the sol-gel method and Pt was then deposited on this support (Pt/SnO 2-Al 2O 3 catalyst). This procedure prevented loss of Sn at the calcination step. In addition, Pt/SnO 2-Al 2O 3 demonstrated a remarkable promotion effect of Sn compared with Pt-Sn/Al 2O 3. CO adsorption was higher on Pt/SnO 2-Al 2O 3 than on Pt-Sn/Al 2O 3. Sn present in the oxidized state was dispersed on the support surface of Pt/SnO 2-Al 2O 3. XRD measurements suggested that an inactive PtSn 2 phase was formed and particle growth occurred in Pt 3Sn/Al 2O 3. XRD peaks from Pt were not observed for Pt/SnO 2-Al 2O 3, suggesting the formation of highly dispersed Pt 3Sn. This study showed that highly dispersed tin oxides on the support surface retarded side reactions and formation of Sn-rich PtSn 2 particles, resulting in high activity for n-butane dehydrogenation.