Zeolite composite prepared by quasi-in situ interzeolite conversion approach

The design of zeolites with optimized textural properties is a continuous goal. Here, we report a composite comprising mesoporous ultra-stable zeolite Y (USY) and nanosized Zeolite Socony Mobil-5 (ZSM-5) with enhanced acid site accessibility and pore connectivity through quasi-in situ interzeolite conversion in a solvent-free medium. The preparation of the composite begins with a spatial and elemental-biased dissolution of USY with impregnated tetrapropylammonium hydroxide (TPAOH). This results in a hierarchical zeolite with increased mesopore volume and improved pore connectivity. Simultaneously, the solute provides all the necessary nutrients for the growth of ZSM-5 zeolite. Due to the constrained mass transfer during the quasi-solid-state dissolution, the resulting ZSM-5 crystals are as small as 10 nm and intimately connected with the USY zeolite. The advantageous synergy between zeolites Y and ZSM-5 in the composite was demonstrated through the methanol-to-olefin reaction and the cracking of n-hexane.