Effects of Alkali Promoters on Catalytic Properties of Alumina-Supported Pt-Sn Catalysts for Long-Chain Paraffin Dehydrogenation
QIU Anding 1, FAN Yining 1* , MA Yongfu 2, WU Peicheng 2, CHEN Yi 1 (1 Department of Chemistry, Nanjing University, Nanjing 210093, China; 2 Research Institute, Nanjing Linear Alkyl Benzene Plant, Nanjing 210046, China)
The influence of alkali metal ion promoters on the catalytic properties of Pt-Sn/γ-Al 2O 3 catalysts for the long-chain paraffin (C 10 ～C 13 ) dehydrogenation has been studied by H 2 chemisorption, infrared spectroscopy (IR), thermogravimetry (TG), temperature-programmed reduction (TPR) and microreactor testing. The results show that adding Li + and Na + to the Pt-Sn/γ-Al 2O 3 catalyst can improve its selectivity and stability for the paraffin dehydrogenation by decreasing the amount of coke formed on the catalysts and increasing the fraction of bare metallic Pt surface after carbon deposition. However, the addition of K + and Cs + with higher basicity leads to a remarkable decrease in the catalytic activity of the Pt-Sn/γ-Al 2O 3 catalyst. Tin oxides in the Pt-Sn-Cs/γ-Al 2O 3 catalyst can be easily reduced to metallic tin, which might form alloy particles with Pt, so that the H 2 uptake and the catalytic activity of the catalyst decrease drastically.