沸石分子筛中复杂异构化反应的Monte　Carlo模拟研究　Ⅲ．孔口失活对反应行为的影响

Monte Carlo Simulation of Complex Isomerization in Zeolites Ⅲ.Effect of Pore Entrance Deactivation upon Reaction Performance

用Ｍｏｎｔｅｃａｒｌｏ方法模拟了沸石分子筛中的复杂异构化反应ＡＢＣ，考察了孔口失活对反应性能的影响．发现孔口失活对产物选择性和反应有效因子的影响取决于反应的Ｔｈｉｅｌｅ模数．可分为三种情况：（１）在低Ｔｈｉｅｌｅ模数下，影响不明显；（２）在中等Ｔｈｉｅｌｅ模数下，有一定的影响，且随孔口活性位失活率的增加，某种产物的选择性线性增加而有效因子线性下降，但二者变化幅度均不大；（３）在较高Ｔｈｉｅｌｅ模数下，影响显著．随着孔口活性位失活率的增加，某种产物选择性明显增加，有效因子明显下降．

In the present paper,the complex isomerization,A B C,over zeolite catalysts was simulated by means of the Monte Carlo technique which account for the elementary processes of adsorption,diffusion, reaction and desorption in zeolites.The effect of pore entrancer deactivation upon the reaction performance was investigated.The results showed that the dependence of the product selectivity and effectiveness upon the frequency of the pore entrance deactivation,X(%),can be classified into three cases by the magnitude of Thiele modulus:(1) independent of X(%),at lower Thiele modulus,(2)linear with X(%)at medium Thiele modulus, and(3) obviously dependent on X(%)at higher Thiele modulus.This means that the product selectivity of the complex isomerization can be improved by pore entrance deactivation when the reaction is operated in diffusion-controlled region.However,effectiveness of the zeolite catalysts at higher Thiele modulus is already small,and it will be decreased further by the pore entrance deactivation.Therefore,to obtain higher selectivity and keep suitable activity,the pore entrance of zeolite catalysts should be modified properly.