Effect of γ-alumina content on catalytic performance of modified ZSM-5 for dehydration of crude methanol to dimethyl ether

Abstract

The effect of γ-alumina as a binder on the catalytic performance of Na-modified ZSM-5 was investigated by using the dehydration of methanol to dimethyl ether (DME). A series of modified ZSM-5 catalysts were prepared with/without γ-alumina and the activity of each catalyst was examined in the dehydration of crude methanol to DME using a fixed-bed reactor at the reaction pressure of 10 atm and LHSV of 10 h −1. The surface and pore characteristics were investigated by Ar adsorption and the acid properties were studied by TPD of ammonia and FT-IR of adsorbed pyridine. Though the addition of γ-alumina lowered the activity of NaHZSM-5, it broadened the operative temperature range (OTR), thereby resulting in more stable catalysts. The ZSM-5 containing 70% of γ-alumina was found to be an efficient catalyst, exhibiting quite high activity as well as wide OTR. This beneficial effect is ascribed to the adequate dilution of the strong acid sites of ZSM-5 in the γ-alumina matrix.