阳离子改性HZSM-5沸石上低碳醇反应历程的TPSR-MS研究

用ＴＰＳＲ－ＭＳ技术研究了Ｃｕ，Ｚｎ和Ｇａ改性Ｈ－ＺＳＭ－５沸石的活性中心性质及Ｃ１～Ｃ４醇的反应历程。结果表明，Ｚｎ－和Ｇａ－ＺＳＭ－５有两种芳构化活性中心，即Ｂ酸和Ｚｎ，Ｇａ活性物种；甲醇在Ｃｕ－ＺＳＭ－５上只生成二甲醚、ＣＯ和ＣＯ２，而在Ｚｎ－ＺＳＭ－５上芳构化反应历程为：（１）醇经由醚脱水生成烯烃，Ｃ２～Ｃ４醇学可单分子脱水生成烯烃；（２）烯烃中间物齐聚，齐聚物通过氢转移和脱氢途径环化、芳

TPSR-MS STUDIES ON THE REACTION PATHS FOR LOWER ALCOHOLS CONVERSION OVER CATION-MODIFIED HZSM-5 ZEOLITES

The active sites and the conversion pathway of C1-C4 alcohols over Cu-, Zn- and Ga-modified HZSM-5 zeolites have been studied by TPSR-MS technique.There are two kinds of aromatization active sites on Zn-and Ga-ZSM-5 zeolites, i.e.the Bronsted acid sites and the dehydrogen-ating active sites related to Zn and Ga species.Cu-ZSM-5 is less active for methanol conversion to hydrocarbons,but active for methanol decomposition.It is also found that over Zn-ZSM-5, methanol is accessible to and adsorbed on the Zn species, thus forming more aromatics than other alcohols.The reaction paths for lower alcohols conversion over the modified zeolites are as follows; (1) lower alkenes formation through dimolecular and monomolecular (except methanol) dehydration; (2) lower alkenes inter-conversion, oligomerization, oligomer cyclization and aromatization via H-transfer and dehydrogenation; ( 3 ) methanol decomposition catalyzed by Zn and Cu species.The contribution of the different reaction pathways varies with the modifying cations and reactants used.