以不同氢氧化物做碱源合成B-EU-1/ZSM-5复合分子筛,并比较各平衡阳离子的结构导向作用及其形貌特征,发现钠离子的导向作用最强,且合成复合分子筛的表面较光滑、无明显晶面界限.对合成样品进行了TG-DTG、N2吸附–脱附和NH3-TPD分析.结果表明:双模板剂一步法合成的复合分子筛模板剂脱除的失重率为5.67%,小于机械复合分子筛的失重率7.31%,复合分子筛的比表面积、孔容和微孔平均孔径均有所增大,同时其酸强度、酸量都增大,有利于二甲苯优先从复合分子筛的孔道结构中扩散出来.将分子筛应用于甲醇转化制二甲苯催化反应,结果显示,双模板剂一步法合成的复合分子筛催化产物油相中芳烃的选择性最高达到66.72%,芳烃中二甲苯的含量为46.15%,二甲苯中对二甲苯的含量达到30.75%.这是由于B-EU-1/ZSM-5催化剂的特殊孔道结构具备择形效应,使得分子动力学直径较小的二甲苯分子优先从其孔道中扩散出来.
B-ZSM-5/EU-1 composite zeolite was synthesized with different hydroxides as alkaline materials. It was found that guiding role of sodium was the strongest by comparing structure-directing effect and appearance character-istics. The surface of B-ZSM-5/EU-1 composite zeolite was smooth without obvious crystal limits. The synthetic sam-ples were investigated by TG-DTG, N2 adsorption-desorption and NH3-TPD. The results show that the template weight loss rate of dual-mode-one-step composite zeolite is 5.67% , which is lower than that of mechanical composite zeolite (7.31%). The specific surface area, pore volume and microporous average pore size have significantly enlarged,meanwhile the amount and strength of acid have also increased, which will be favorable for the aromatization trend of methanol and the priority diffusion of xylene from the composite zeolite. The performance of the composite zeolite catalyst was evaluated in conversion of methanol to xylene. The results show that the selectivity of aromatics in the oil phase reaches 66.72% by using a dual-mode composite zeolite as a catalyst, of xylene in the aromatics reaches 46.15%, and of p-xylene in the xylene reaches 30.75%. The above results can be attributed to special pore structure for the catalytic reaction, which benefits for the priority diffusion of xylene with a smaller particle size from the B-EU-1/ZSM-5 zeolite.
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