Alcohol-assisted synthesis of high-silica zeolites in the absence of organic structure-directing agents

Abstract

In this work, we show for the first time that high-silica zeolites (MFI, TON, MTT, and *MRE) could be synthesized from a combined strategy of both zeolite seeding and alcohol filling in the absence of organic structure-directing agents (OSDAs). High-silica ZSM-5 zeolites with Si/Al ratios ranging from 38 to 240 (TF-Al-ZSM-5) could be synthesized via this route. The key to the success of this technique was the employment of an aluminosilicate precursor with a fully 4-coordinated aluminum species as the initial source, wherein the rearrangement and condensation of the silicate species, rather than the aluminate species, occurred during zeolite crystallization. In addition, heteroatoms, such as Fe and B, could be incorporated into the zeolite frameworks. Catalytic tests for the methanol-to-propylene (MTP) reaction exhibited good catalytic performance for TF-Al-ZSM-5, which was comparable to that of the aluminosilicate ZSM-5 zeolite synthesized with OSDAs. Hence, this method offers viable opportunities for the industrial production and catalytic application of high-silica zeolites in the future.