摘要
对经CF_2Cl_2处理了不同时间的HZSM-5分子筛,采用XRD,IR,XPS,SEM和TPD等方法考察了其结构和表面性质的变化。发现B酸位减少的同时,中等强度的B酸位的分数有所提高,沸石表面不但脱铝也有脱硅现象发生。这种改性的HZSM-5分子筛对异丙苯裂化反应及偏三甲苯-甲醇烷基化合成均四甲苯反应的活性、选择性及催化剂的稳定性都有良好的促进作用。
The physical and chemical changes of HZSM-5 zeolites treated with CCl2-F2 for different times were studied by using XRD, XPS, SEM, IR, TPD and BET weight methods. Their catalytic behavior and reaction mechanism were determined and discussed. It was found that the fraction of Bronsted acid sites decreased, while the fraction of Bronsted acid sites of medium acidity increased after treatment with CC12F2. The surface of zeolite was not only dealuminated but also desiliconated. The activity for cumene cracking of all the modified zeolite catalysts was increased. The selectivity for 1,2,4,5-tetrame-thylbenzene by the alkylation of 1,2,4-trimethylbenzene with methanol on HZSM-5 samples treated with CC12F2 for 2 and 5min was higher than that of untreated HZSM-5. This fact testified strongly the IR results which indicated that the fraction of B acid sites of medium acidity was increased by the treatment of HZSM-5 with CC12F2.
基金
国家自然科学基金
