聚苯基甲基硅氧烷改性ZSM-5分子筛上的甲苯择形歧化反应

以聚苯基甲基硅氧烷为改性剂,采用化学液相沉积法对ZSM-5分子筛催化剂进行改性修饰,考察改性催化剂的甲苯择形歧化反应性能。采用XRD、BET、NH 3-TPD表征改性催化剂的孔结构和酸性质。结果表明,聚苯基甲基硅氧烷作为改性剂可以增加催化剂的弱酸中心和中强酸中心酸量,同时缩小催化剂的平均孔径,改性程度与改性次数有关。改性催化剂用于甲苯歧化反应可以增加对二甲苯的选择性,对二甲苯选择性的增加程度与改性次数有关,改性次数增多,对二甲苯选择性增加越显著,同时甲苯转化率越低,副反应越多。

Selective disproportionation of toluene on polyphenylmethylsiloxane modified ZSM-5 zeolite

The ZSM-5 zeolite catalyst was modified by chemical liquid deposition with polyphenylmethylsiloxane(PPMS) as modifier and tested in toluene disproportionation reaction.The properties of the modified catalyst were characterized by XRD,BET and NH₃-TPD.The results showed that PPMS as a modifier could increase the amount of weak acid centers and medium strong acid in the catalyst,and reduce the average pore diameter of the catalyst.The pore size and degree of modification were related to modification times.Selectivity of p-xylene increased over the modified catalyst.The increasing degree of selectivity of p-xylene was related to modification times.When modification times increased,the selectivity of p-xylene was higher,the conversion of toluene was lower,and side reactions were more.