不同硅铝比小晶粒ZSM-5分子筛的合成及催化苯甲醇烷基化反应性能

SYNTHESIS OF SMALL PARTICLE SIZE ZSM-5 ZEOLITE WITH DIFFERENT Si Al RATIO AND ITS CATALYTIC ACTIVITY FOR BENZENE METHANOL ALKYLATION

采用简单的原位水热合成法制备了5种硅铝比不同的小晶粒多级孔ZSM-5分子筛,并对制备的小晶粒多级孔ZSM-5分子筛进行了X射线衍射、NH_(3)程序升温脱附和N_(2)吸附-脱附等表征分析,考察了不同硅铝比的ZSM-5分子筛催化苯甲醇烷基化反应的性能。结果表明:合成的5种不同硅铝比的ZSM-5分子筛具有多级孔结构,呈现不规则的颗粒状,晶粒尺寸较小,颗粒聚集形成蜂窝状;随着硅铝比升高,分子筛的比表面积和孔体积增大、酸强度减小、酸量降低。在470℃、0.5 MPa、质量空速2 h^(-1)、苯甲醇摩尔比1∶1条件下,不同硅铝比ZSM-5分子筛催化苯甲醇烷基化反应的结果表明:随着分子筛硅铝比升高,苯转化率和二甲苯选择性提高,乙苯选择性降低;当分子筛硅铝比为150、反应时间为72 h时,苯转化率最高为62.92%,二甲苯选择性为37.38%,乙苯选择性为0.81%;该ZSM-5分子筛运行1200 h后仍具有良好的活性,应用前景较好。

Five kinds of Si/Al ratio ZSM-5 zeolites with small particle size and hierarchical pore were prepared by simple in-situ hydrothermal methods.XRD,N_(2)adsorption-desorption,NH_(3)-TPD,Py-IR and SEM were used to characterize the prepared ZSM-5.The catalytic performance of ZSM-5 zeolites with different Si Al ratio for benzene methanol alkylation was investigated.The results showed that the ZSM-5 zeolites with different Si/Al ratio had multi-stage pore structure,irregular particle shape,small crystal size and honeycomb shape.Under the conditions of 470℃,0.5 MPa(H_(2))and mass space velocity 2 h^(-1),n(methanol)∶n(benzene)=1∶1,the alkylation of benzene with methanol catalyzed by ZSM-5 zeolites with different Si/Al ratio was studied.The results showed that the conversation of benzene was 62.92%,the selectivity of xylene was 37.38%,and the selectivity of ethylbenzene 0.81%when the n(SiO_(2))n(Al_(2)O_(3))was 150 and the reaction time was 72 h.The ZSM-5 still has good activity after 1200 h operation and has a good application prospect.