甲烷在Mo/HZSM-5催化剂上的脱氢聚合反应

对不同Mo含量的Mo／HZSM－5催化剂的结构进行了表征，并对这些催化剂的甲烷非氧气氛下的转化反应进行了考察．催化剂的BET比表面积及酸性随Mo含量的增加而降低，当Mo含量大于5％时，Mo对ZSM－5分子筛的晶型有影响，并出现MoO3物相．甲烷在700℃时可高选择性地生成苯和乙烯，最佳Mo含量大约为2％．纯的MoO3或HZSM－5上该反应几乎不进行，因此，可能是分散的钼氧离子和分子筛的酸中心是甲烷转化的活性中心，只有二者的协同作用才能促进甲烷的转化．反应后催化剂中的钼物种被还原了．催化剂上的积炭可能是催化剂失活的主要原因之一，烧炭后催化剂活性基本恢复．

Structure of Mo/HZSM-5 Catalysts and Their Reactivities of Methane Dehydro-oligomerization under Non-oxidizing Conditions

The structures of Mo/HZSM-5 catalysts with different molybdenum loadings were characterized and the reaction performances of methane dehydro-oligomerization over these catalysts were investigated. It was found that the BET surface areas, micropore volumes as well as the surface acidities of the catalysts decreased with the increasing of molybdenum loading. When the molybdenum loading was greater than 5%, molybdenum would impose significant influence on the crystalline structure of HZSM-5 zeolite and MoO3 phase would appear. The optimum molybdenum content for the conversation of methane to benzene and ethylene was about 2%. The synergistic effect between molybdenum-oxygen species and the acidic sites of HZSM-5 plays an important role in the catalysis conversion of methane as both MoO3 and HZSM-5 alone showed little reactivity. The molybdenum species were reduced and the acidic sites were covered by carbonaceous substances after the deactivation of catalysts. The carbon deposition seems to be the predominant reason for the catalyst deactivation because the catalyst activity could be rejuvenated after burning off coke.