论文部分内容阅读
考察了交换剂和改性处理对HZSM-5沸石在甲苯乙基化反应中对位选择性的影响,检测了反应初级产物的组成,用原位TPD法研究了沸石表面酸中心的催化性质。结果表明,孔径和酸性分布都是影响沸石对位选择性的重要因素,但是表面酸性的调变对提高HZSM-5沸石的对位选择性更为重要。对-甲乙苯是甲苯乙基化反应的初级产物,在表面异构化反应后生成间-甲乙苯。烷基化和异构化两种反应活性中心在酸强度上的差异很小,仅仅是所处位置不同。由于改性处理同时抑制了这两类活性中心,使HZSM-5沸石在甲苯乙基化反应中的对位选择性上升而活性下降,表现出反向变化关系。
The effect of exchange agent and modification treatment on the selectivity of HZSM-5 zeolite in toluene ethylation was investigated. The composition of the primary products was investigated. The in situ TPD method was used to study the catalytic nature of zeolite acid sites. The results show that both pore size and acidity distribution are important factors affecting the para-position selectivity of zeolite, but the modulation of surface acidity is more important to improve the para-selectivity of HZSM-5 zeolite. Para-ethylbenzene is the primary product of the toluene ethylation reaction, producing meta-ethylbenzene after the isomerization reaction. Alkylation and isomerization of the two reactive centers in the acid intensity difference is very small, just the location is different. Due to the modification treatment and the inhibition of these two kinds of active centers, the activity of HZSM-5 zeolite in para-ethylation of toluene increased and the activity decreased, showing a reverse relationship.