摘要
应用C_2H_4-H_2滴定方法考察了Pt/Al_2O_3和PtSn/A1_2O_3催化剂经过n-C_4H_(10)积炭反应及氧烧炭循环后催化剂金属中心的变化。发现随循环次数增加,Sn对Pt表面的分割作用减弱,催化剂单铂中心减少而多铂中心增加。积炭催化剂的程序升温表面反应进一步揭示了多次循环后PtSn/Al_2O_3催化剂上烃分子脱氢深度增加,表面含炭物加氢活性减弱。表明经过循环积炭-烧炭处理的双金属PtSn催化剂一定程度地表现出Pt/Al_2O_3催化剂的性质。
C2H4-H2 titration, TPO and TPSR are used to study the effect of coking-burning off cycle 011 the surface reactivities of Pt/Al2O3 and PtSn/A;2O3 catalysts. By C2H4-H2 titration, two kinds of active site are identified on PtSn catalyst, the Pt-Pt site on which the chemisorbed hydrogen can react with ethylene to form ethane and the Pt-Sn site on which no reaction takes place.It is found that the titration percentage of chemisorbed hydrogen (HT%) on PtSn catalyst increases with coking-burning off treatment going on. TPO curves show that Tm of the two peaks on fresh PtSn catalyst is higher than that on Pt/Al2O3, while a same peak appears at 380℃ for the regenerated Pt and PtSn catalysts. The carbonaceous deposits on the regenerated PtSn catalyst following n-C4H10 reaction at 500℃ are deeply dehydrogenated, and are similar to that on Pt/Al2O3 to some extent.
