Effect of ultrasonic irradiation and/or halogenation on the catalytic performance of γ-Al₂O₃ for methanol dehydration to dimethyl ether

Dimethyl ether (DME) is amongst one of the most promising alternative, renewable and clean fuels being considered as a future energy carrier. In this study, the comparative catalytic performance of the halogenated γ-Al₂O₃ prepared from two halogen precursors (ammonium chloride and ammonium fluoride) is presented. The impact of ultrasonic irradiation was evaluated in order to optimize both the halogen precursor for the production of DME from methanol in a fixed bed reactor. The catalysts were characterized by SEM, XRD, BET and NH₃-TPD. Under reaction conditions where the temperature ranged from 200 to 400 ℃ with a WHSV =15.9 h^-1 was found that the halogenated catalysts showed higher activity at all reaction temperatures. However, the halogenated alumina catalysts prepared under the effect of ultrasonic irradiation showed higher performance of γ-Al₂O₃ for DME formation. The chlorinated γ-Al₂O₃ catalysts showed a higher activity and selectivity for DME production than fluorinated versions.