金属／分子筛催化剂的卤化氢处理对环己烯加氢转化的影响Ⅱ．Re／H-ZSM-5催化剂

Effect of Hydrohalogenation of Metal/Zeolite Catalysts for Cyclohexene Hydroconversion Ⅱ. Rhenium/H-ZSM-5 Catalysts

用HCl或HF对Re/H-ZSM-5催化剂进行了后处理,并在50～400℃用连续流动反应器研究了催化剂对环己烯加氢转化反应的影响.与HCl处理相比,HF处理显著提高了催化剂上环己烯加氢生成环己烷以及甲基环戊烯加氢生成甲基环戊烷的催化活性,这主要是因为HF处理催化剂具有较高的铼分散度、酸中心数及酸强度.Re/H-ZSM-5(HF)催化剂上最高的酸中心强度使其具有最高的加氢裂化活性及最低的环己烯脱氢生成环己二烯活性.在未处理的Re/H-ZSM-5催化剂上,沉积在分子筛载体孔道和空穴中非骨架Al和Si的量最少,因而对生成芳烃的脱氢反应具有最高活性.卤化氢处理催化剂上二甲苯异构体的相对产量表明:HF处理催化剂上,对二甲苯产量高于间二甲苯;HCl处理催化剂上,间二甲苯和对二甲苯产量基本相当;在未处理的催化剂上,间二甲苯量产量比对二甲苯高.此外,上述所有催化剂上的邻二甲苯产量均约等于对二甲苯与间二甲苯之和.

A post-preparation treatment of the Re/H-ZSM-5 catalyst with HCl or HF was performed, and its elfect on cyclohexene hydroconversion reactions at 50-400 ℃ in a continuous flow reactor was investigated. The HF treatment significantly improved the catalytic activity for cyclohexene hydrogenation to cyclohexane and methylcyclopentenes to methylcyclopentane in comparison to the HCl treatment. This is principally attributed to the higher Re dispersion and enhancement of the acid site number and strength. Thereupon occurs the highest hydrocracking activity and the lowest dehydrogenation activity for cyclohexene to cyclohexadienes on Re/H- ZSM-5（HF） by virtue of the highest strength of acid sites. The untreated Re/H-ZSM-5 catalyst exhibited the highest dehydrogenation activity for aromatics production, which may be attributed to the lowest quantity of extraframework Al and Si depositing in the pores and cavities of the zeolite support. Industrially, the relative amounts of xylene isomers produced on the hydrohalogenated catalysts are of interest. The amount of D-xylene was higher than m-xylene on the HF-treated catalyst; m- and D-xylenes presented almost equal values on the HCl-treated catalyst l m-xylene exceeded D-xylene on the untreated catalyst. O-xylene is almost equal to the sum of p- and m-xylenes in all cases.