Direct synthesis of b-axis oriented H-form ZSM-5 zeolites with an enhanced performance in the methanol to propylene reaction

A b-axis oriented microsized H-form ZSM-5 zeolite with a thinness of approximately 300-500 nm along the b-axis direction was prepared for the methanol to propylene (MTP) reaction by a two stage hydrothermal crystallization method with ammonium hydroxide as the base source and glucose as an additive. Ammonium hydroxide contributed to the direct synthesis of H-form ZSM-5 zeolite after calcination to remove the template and decompose the NH4+-form zeolite, thus removing the need for further ion-exchange and calcination steps. Glucose was beneficial to the formation of the thin hierarchical b-axis oriented ZSM-5 zeolites. The b-axis oriented H-form ZSM-5 catalyst exhibited a longer catalyst lifetime and a higher propylene selectivity in the MTP reaction compared to that of ZSM-5 made by a conventional method. The better catalytic performance was ascribed to the relatively low content of strong acid sites especially those on the external surface of the b-axis oriented microsized ZSM-5 catalyst.