Dimethyl ether synthesis via methanol over metal oxide catalysts supported on zeolite Y in a fixed bed reactor

Dimethyl ether (DME) has recently been suggested as a clean alternative fuel for diesel engines instead of diesel, and as fuel additive and family cooking gas instead of liquefied petroleum gas (LPG) with much lower NOx emission, near-zero smoke production, and less engine noise compared with traditional diesel fuels [1, 2]. In view of DME’s potential as a clean alternative diesel fuel, much consideration should be given to the production of DME in large quantities. At present, DME is produced by methanol dehydration over solid acid catalysts such as γ -alumina and zeolites: 2CH3OH → CH3OCH3 + H2O (ΔG = -12.1 kJ/mole at 250 oC) Or by direct production of DME from syngas over a hybrid catalyst, which is composed of a methanol synthesis catalyst and a solid acidcatalyst. However, they produce undesired side products including hydrocarbons and coke causing catalyst deactivation and ultimately stopping the process of dehydration. Recent studies have shown that the main reason for the catalyst deactivation (i.e. coke deposition) has been due to existence of strong acid sites on it. In other words, catalysts including medium to weak acid sites are desirable for DME production [3]. Therefore, researchers are trying to modify the catalyst structure and/or formulation in order to optimize the DME production as well as improve the catalyst stability. It is known thatthe modified Y zeolite by various metals which has low acidic sites is the better catalyst than the pure HY [4]. In this study, we investigated the performance of catalytic activity of modified Y zeolites by different metals for production of the DME from methanol through wet impregnation of it by several metals. Their catalytic activities were investigated at the several temperatures and compared for determination of the best condition for DME production .