6533b823fe1ef96bd127ea25

RESEARCH PRODUCT

Control of catalytic properties of ZSM-5 made by fast and template- free synthesis.

subject

description

Abstract The fast template-free synthesis of ZSM-5 was accomplished in both static and stirred autoclaves employing sodiumwaterglass.silica hydrogel and pyrogenic silicas as silica sources. Highly pure crystalline ZSM-5 was obtained in the sodiumwaterglass reaction system in the stirred autoclaves without seeds within 3 hours. Addition of 2% (w/w) of seeds reduced the reaction time to 2 hours. The catalytic activity and shape selectivity of the H-ZSM-5, tested by the disproportionation of ethylbenzene, was found to be largely controlled by the synthesis parameters and by the posttreatments. The homogeneous aluminum distribution across the crystals achieved by this synthetis route resulted in a greater shape selectivity compared to those with an uneven aluminum distribution being prepared by adding templates. Various kinds of posttreatments, e.g. “alkaline calcination”, led to an additional enhancement of the shape selectivity yielding up to 99% of p-isomer in the ethylbenzene disproportionation reaction.