固体酸催化剂上的甲苯硝化反应

研究了ＨＭ，ＨＺＳＭ－５和其它几种固体酸催化剂上的甲苯硝化反应，发现高硅铝比ＨＺＳＭ－５沸石的活性及对位选择性最高，甲苯转化率达６５％，ｐ／ｏ比达０．７８．通过考察沸石晶粒大小、酸性强弱、脱铝程度和阳离子交换等因素对反应活性和选择性的影响，发现该反应主要在沸百孔内进行，对位选择性与沸石的孔径存在一定对应关系．沸石催化剂除能促进ＨＮＯ３解离成ＮＯ外，对甲苯也有活化和富集作用，因而反应活性与催化剂的酸性有关，适当增加沸石的亲油性也有利于提高硝化反应活性．

NITRATION OF TOLUENE ON SOLID ACID CATALYSTS

he nitration of toluene in liquid phase with nitric acid on HM,HZSM-5 and some other solid acid catalysts has been studied. HZSM-5zeolite with high Si/Al ratio displays the highest catalytic activity andpara-selectivity for the nitration reaction, i. e. toluene conversion 65%and p/o ratio 0. 78. The effects of zeolite crystal size, acidity, dealumination and canon exchange on the catalytic activity and para-selectivityfor the reaction have been investigated in detail. It has been confirmedthat the nitration reaction proceeds in the zeolite pore channel, and thepara-selectivity for the reaction is closely related to the pore size of thecatalyst. The nitration of toluene with HNO3 is accelerated by the catalyst via the enhancement of the dissociation of HNO3 to form NO2 andalso the activation and adsorption of toluene on the catalyst, therefore,the catalytic activity is dependent on not only the acidic properties of thesolid acid catalyst, but also the increase in hydrophobicity of the catalyst, which is advantageous to the reaction.