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用氨的热失重及吡啶的中毒实验研究了PHZSM-5/Al_2O_3及PMgHZSM-5/Al_2O_3沸石催化剂的酸性,发现改性后的HZSM-5型催化剂的强酸中心减弱,弱酸中心变化不大,并且经P、Mg改性后的酸分布变化比P改性后要明显,实验结果说明这主要是由于P或P、Mg进入了沸石的孔道内,并占据孔口的强酸中心部位以及发生孔口部分阻塞的缘故,这一效应抑制了对-甲乙苯异构化反应,从而提高了甲苯乙基化的对位选择性。
The acidity of PHZSM-5 / Al_2O_3 and PMgHZSM-5 / Al_2O_3 zeolites catalysts was investigated by the thermogravimetric analysis of ammonia and pyridine poisoning. The results showed that the strong acid sites of the modified HZSM-5 catalysts decreased and the weak acid sites did not change much The results show that the change of acid distribution after P and Mg modification is more obvious than that after P modification. The experimental results show that this is mainly due to P or P and Mg entering the pores of the zeolite and occupying the strong acid center of the orifice and the orifice Partially blocked, this effect suppresses the isomerization reaction of p-methyl ethylbenzene, thereby increasing the para-toluidine para-para selectivity.