【摘要】 <正> 通过离子改性、水热处理、表面毒化及预积炭等方法均可提高ZSM-5沸石的择形催化性能.上述方法在改变沸石孔道结构时也明显地改变了沸石的表面酸性质.近年来,采用化学修饰的方法对沸石表面和孔口进行调变的研究已有一些报导.杨儒等用硅烷或SiCl₄等进行气相硅烷化,除缩小孔口尺寸外,还产生了骨架脱铝补硅作用,导致表面酸性质发生变化.王清遐等用正硅酸乙醇浸渍(ZSM-5沸石,随着硅的载入量增加,催化剂酸量和反应活性均降低,而对位选择性增加.Murakami用正硅酸甲更多还原

【Abstract】 The external surface of ZSM-5 zeolite catalysts was chemically modified by liquid-phase deposition of silicon alkoxide, and their surface acidic property, pore structure and catalytic performance were characterized by XRD, IR, TPD, the effective diffusivity of micropore, adsor-ptivity for n-hexane and cyclohexane as well as the alkylation of toluene with ethanol. The results indicated that the thin .layer of silica deposit covered the external surface of ZSM-5 zeolite without the substitution of framework aluminium by silicon atom, and that the surface acidity and catalytic activity changed slightly with increasing the amount of silica deposited, but the effective diffusivity of micropores and the adsorption amount of cyclohexane decreased significantly, thus, the p-selectivity for ethylation of toluene increased markedly.更多还原