Surfactant-directed mesoporous zeolites with enhanced catalytic activity in tetrahydropyranylation of alcohols: Effect of framework type and morphology

- The influence of zeolite topology and morphology on the catalytic behaviour in tetrahydropyranylation of alcohols was investigated.
- Variables include nanosponge vs. bulk morphology, zeolite type (BEA, MTW, MFI), Si/Al and the size of reactant molecules (methanol, 1-octanol, cyclohexanol and 2-adamantanol).
- Due to the high accessibility of active sites and facile diffusion of reactant and product molecules BEA nanosponges showed enhanced catalytic performance (TON = 529-827) compared with conventional analogue (TON = 198-375).

Nanosponge zeolite beta was hydrothermally synthesized using multi-quarternary ammonium surfactant as a meso-micro hierarchical structure directing agent. The nanosponge morphology of the beta zeolite consisted of randomly interconnected nanocrystals with thickness of 10-20 nm. The beta nanosponges with highly mesoporous structure exhibited enhanced catalytic activity in tetrahydropyranylation of alcohols (methanol, 1-octanol, cyclohexanol and 2-adamantanol) when compared with the conventional beta zeolites and nanosponge zeolites of MTW and MFI framework types. The enhanced catalytic performance (∼60% conversion with 90-100% selectivity towards tetrahydropyranyl ether and over two times higher initial rate compared to other zeolites) of hierarchical beta nanosponges can be attributed to the high accessibility of acid sites and facile diffusion of reactants and products through the mesopores.

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