Synthesis and Catalytic Performances of Mesoporous Zeolites Templated by Polyvinyl Butyral Gel as the Mesopore Directing Agent

The mesoporous zeolites with BEA and MEL topology were synthesized by using polyvinyl butyral gel as the mesopore directing agent. The PVB/silica composite was readily prepared by sol−gel technique and then used as precursor for the synthesis of mesoporous zeolites. Upon the direct hydrothermal crystallization of PVB/silica composite, the silica was transformed into zeolite, whereas the PVB gel was incorporated in the zeolite crystals. Calcination of the obtained PVB/zeolite composite yielded the opening of micropores and mesopores in zeolites, respectively. The characterization techniques confirmed that the obtained porous materials consisted of well-defined microporosity and irregular mesoporosity. The mesoporous zeolites exhibited higher conversion and enhanced resistance toward deactivation in the cracking of 1,3,5-trimethylbenzene and 1,2,4-trimethylbenzene, as compared with conventional zeolites. The improved catalytic activity can be attributed to the more efficient diffusion of reactants and products in the crystals with the help of mesopores.