Synthesis of mesoporous MFI zeolite using PVA as a secondary template

We have developed a new facile synthesis method for a uniform mesoporous MFI zeolite using poly vinyl alcohol with surface activity (PVA, MW: 13,000-23,000, 87-89 % hydrolyzed) as a secondary template. The PVA concentration in precursor solutions was optimized for the formation of mesopores in zeolite crystals. The PVA molecules were not incorporated into zeolite crystals when the precursor mixture contained 1.5 wt% of PVA. Neither MFI zeolite structures nor mesopores were formed in the case of adding a large amount of PVA (4.5 wt%) into the precursor mixture, suggesting that the high PVA density in the solution inhibited a crystallization of MFI zeolite. Meanwhile, in the medium PVA contents condition (3.0 wt%), uniform mesopores with a size of 15 nm were formed in the zeolite single crystals. The mesopore size was approximately in accord with the end-to-end distance of PVA molecule, which implies that one PVA molecule was embedded in one mesopore in the crystallization process. Furthermore, the mesoporous MFI zeolite showed a higher catalytic performance on 1,3,5-trimethylbenzene cracking than the other samples.