Aerosol-assisted synthesis of nano-sized ZSM-5 aggregates
Nano-sized ZSM-5 aggregates with interparticle mesopores was synthesized by an aerosol-assisted method. The amorphous aluminosilicate powder was used as a precursor, which was obtained by an aerosol process from an aqueous solution of the silicon and aluminium sources. The amorphous powder was crystallized in an autoclave with the structure-directing agent tetrapropylammonium hydroxide. No extra water was added in this step. The synthesis was performed in an extremely dense system, hence the amount of both template and waste water can be significantly reduced. The formation of the nanocrystalline MFI zeolite is mainly based on the liquid phase transformation in a supersaturation system. The nano-sized ZSM-5 aggregates were composed of nanocrystals with a size of 50–100 nm. Compared with the ZSM-5 zeolite synthesized by a conventional hydrothermal method, the nano-sized ZSM-5 aggregates exhibits a higher BET surface area, external surface area, and total pore volume and better Al species distribution. This nanocrystalline ZSM-5 zeolite shows a higher catalytic activity and stability in catalytic cracking of 1,3,5-triisopropylbenzene.