Rapid synthesis of zeolite catalysts for methanol to olefin conversion by the precursor heating method

Abstract

Rapid synthesis of a zeolite which has catalytic activity for methanol conversion into C 2~C 4 olefins with high selectivity has been studied. Firstly, the crystallization of ZSM-34 class zeolite, using choline as the organic ingredient at 100°C for 131 days (standard method) has been followed by measurements of XRD, SEM, BET surface area and catalytic activity. An amorphous precursor of spherical shape was formed from the gel mixture within three days and intergrowth of zeolite crystals occurred in the spherical precursor. Optimum selectivity for olefin formation was obtained with a zeolite crystallized over 25 days. In order to reduce the crystallization time, we tried heating directly the gel at a constant rate of 2.8°C min −1 to 200° C and maintaining it at this temperature for 2 h (direct heating method). However, the catalyst life for methanol conversion was shortened. On the other hand, when the precursor was heated at a constant rate of 1.7°C min −1 to 190° C and maintained at this temperature for 0.5 h (precursor heating method), the resulting zeolite exhibited a better performance than zeolites prepared by the standard and direct heating methods.