双模板条件下介孔结构ZSM-5沸石的合成

THE SYNTHESIS OF MESOPOROUS ZEOLITE ZSM-5 BY USING DUAL TEMPLATES

在具有介观大小的聚乙烯醇水溶性高分子模板（PVA）和小分子有机铵四乙基溴化铵（TPABr）共同存在条件下，合成了具有介孔结构的ZSM-5沸石晶体，合成产物通过XRD、N2吸附～脱附、SEM、FT-IR和DTG等手段进行了表征。结果表明，双模板条件下合成的ZSM-5沸石晶体比常规采用小分子四乙基溴化铵单模板合成样品含有更多的介孔，且合成体系中随PVA加入量的增多，样品所包含的介孔率增加。介孔的形成可能是由于沸石的溶胶对高分子物质PVA产生吸附并将其包裹进胶粒中，经过高温焙烧除去PVA后的结果。与传统的沸石晶体材料相比，这些发达的介孔结构可大大提高其大分子的可接近性。

A novel and facile synthesis route to hierarchical mesoporous zeolite ZSM-5 with pore diameters in narrow distribution is reported. In the synthesis route using a mixture of mesoscale water-soluble polymers （PVA） and small organic ammonium salts （TPABr） were used together as template. The obtained materials were characterized by X-ray diffraction, nitrogen adsorption, scanning electron microscopy, FT-IR spectroscopy and thermogravimetric analysis. The prepared ZSM-5 zeolites contain higher mesoporosity in addition to the instrinsic crystalline microporosity than conventional zeolites, and the content of mesoporosity introduced in the zeolite ZSM-5 gradually increased with PVA amount increase in the gel. The formation of mesopore may be resulted from the adsorption of PVA into ZSM-5 crystals and subsequent removal of PVA by burning. In comparison with conventional zeolites, the presence of abundant mesopores in the mesoporous ZSM-5 zeolite can improve the accessibility of large molecules.