影响铂铼催化剂性能的某些因素

EFFECTS OF RARE EARTH AND SULFUR AND PREPARATION CONDITIONS ON PROPERTIES OF PtRe/AI_2O_3 REFORMING CATALYST

铂铼重整催化剂虽然早已工业化,但其性能仍在不断改进,其作用机理也仍在不断深入的探讨中。一般认为,铂铼催化剂的性能与其制备条件密切相关。认为,高温焙烧可提高催化剂的活性和稳定性。而Charcosset等的看法是,焙烧削弱了铂铼的相互作用,对还原过程中生成铂铼合金不利。近来还有不少文献报导了担体的浸渍方式对铂铼催化剂的影响。在铂铼中加入第三金属以及研究予硫化的报导也很多。

The properties of PtRe/Al_2O_3 reforming catalyst were studied at atmospheric pressure and 500℃ using pulse microcatalytic reactor and transmission electron microscopy (TEM). Conversions of n-heptane and methylcyclopentane were used as probe reactions. Results show that calcination of catalysts before reaction has significant effect on. selectivity patterns for both PtRe/Al_2O_3 and PtReNd/Al_2O_3.Mechanical mixtures of PtRe or PtReRE/Al_2O_3 and A1_2O_3 showed noticeably higher selectivity for isomerization and lower cracking selectivity, compared with coimpregnated PtRe or PtReRE/Al_2O_3.Observation by TEM showed that rare earth reduces the size of surface metal aggregates which are responsible for aromatization. Presulfidation significantly reduced cracking selectivities and enhaced selectivities for both isomerization and aromatization for the catalysts investigated here.