EFFECT OF COKING-BURNING OFF CYCLE ON THE PROPERTIES OF Pt/Al_2O_3 AND PtSn/Al_2O_3 CATALYSTS Ⅱ. THE SURFACE REACTIVITY OF REGENERATED CATALYSTS
Fan Yi-ning, Zang Jing-ling and Lin Li-wu(Dalian Institute of Chemical Physics, Academia Sinica, Dalian 116023)
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.