改性催化剂对甲苯烷基化反应的影响探讨

引入几种金属和非金属元素作为改性剂,发现采用硅铝比为400的含镧分子筛为最佳分子筛母体,能形成体积较大的镧氧四面体,与硅氧四面体和铝氧四面体共同形成沸石骨架,改变了分子筛的孔径结构,增大了邻、间、对二甲苯间扩散速率的差别,有利于对二甲苯选择性的提高。选择镁为改性元素,随着氧化镁含量的增加,甲苯对位选择性逐渐上升。当氧化镁计算含量为20%时,甲苯的转化率为19.7%,对位选择性为90.6%。该催化剂体系可以满足以甲苯和甲醇为原料直接合成高纯度对二甲苯的需要。

Influence of Modified HZSM-5 Catalysts on Alkylation Reaction of Toluene with Methanol

A series of HZSM-5 zeolite catalysts modified with B, Mg and Ti elements were prepared by the impregnation method. Alkyiation reaction Of toluene with methanol to p-xylene was carried out over these catalysts. According to the research, when the ratio of Si to Al is 400 the La-0 the seolite catalysts can improve the characters of pore structure, increasing the selectivity of p-xylene. MgO is mainly deposited on the external surface of HZSM-5. If the calculated concentration of MgO reaches 20% or p-xylene selectivity is sig nifieanfly improved to 90.7%; andre conversion 19,7% ,owing to effect of La and Mg.