Hydrothermal Synthesis of H-ZSM-5 Catalysts Employing Mixed Template Method and its Application in Conversion of Methanol to Light Olefins

The hydrothermal synthesis of H-ZSM-5 catalysts for application in methanol to olefin (MTO) reaction was performed by partial and total substitution of tetrapropyl ammonium hydroxide (TPAOH) with equivalent amount of the less expensive tetrapropyl ammonium bromide (TPABr) template. Five H-ZSM-5 zeolites were synthesized using silicic acid and sodium aluminate with various proportions of TPAOH and TPABr, constant TPA+ concentration (0.04M) and initial gel pH (10.5). Increasing molar ratio of TPAOH in initial gel from 0.33 to 3 decreased the purity of H-ZSM-5, and affected its crystallinity and particle size. The catalytic performance tests were conducted in fixed-bed reactor at 480¬°C with a feed WHSV of 0.9¬h-1. All the catalysts exhibited approximately similar methanol conversion though their propylene selectivities and products distributions were dependent on the template composition. This work verified that despite providing the same TPA+ and OH- concentrations in the initial gel, the samples with different properties could form using diverse template combinations