添加碱金属助剂对负载型铂锡催化剂长链烷烃脱氢反应性能的影响

Effects of Alkali Promoters on Catalytic Properties of Alumina-Supported Pt-Sn Catalysts for Long-Chain Paraffin Dehydrogenation

采用微型催化反应装置 ,结合氢化学吸附、吡啶吸附的红外光谱、热重分析和程序升温还原等物理化学手段 ,研究了添加碱金属助剂对负载型Pt Sn/γ Al2 O3催化剂的长链烷烃 (C10 ～C13)脱氢反应性能、表面酸性、金属表面性质以及负载组分与载体之间相互作用的影响 .发现添加一定量的Li+和Na+可以减少催化剂的积炭量 ,提高催化剂的金属表面裸露度 ,从而改善催化剂的脱氢反应稳定性 .而添加碱性较强的K+和Cs+虽可以提高催化剂的抗积炭性能 ,但破坏了Pt Sn Al2 O3之间的相互作用 ,使锡组分易被还原 ,催化剂的活性表面减小 ,从而抑制了催化剂的脱氢反应活性 .

The influence of alkali metal ion promoters on the catalytic properties of Pt-Sn/gamma -Al2O3 catalysts for the long-chain paraffin (C(10)similar toC(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/gamma -Al2O3 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/gamma -Al2O3 catalyst. Tin oxides in the Pt-Sn-Cs/gamma -Al2O3 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.