The optimum conditions for methanol conversion to dimethyl ether over modified sulfated zirconia catalysts prepared by different methods

Sulfated zirconia (SZ) and two promoted 1%Mn/SZ catalysts which have been prepared via sol gel (Mn/SZ-S) and impregnation (Mn/SZ-I) methods were studied. The morphology of the catalysts was characterized by XRD, BET, NH₃-TPD, ICP, SEM and FT-IR analysis. The conversion of methanol to dimethyl ether and hydrocarbons was carried out in the temperature range of 120−300 °C. The Mn/SZ-S showed the highest activity due to the high surface area with suitable acidity. The optimum condition of Mn/SZ-S catalyst was investigated at 200 °C and LHSV of 0.02 h⁻¹ in a time range from 30 to 210 min. It was found that the total conversion decreased from 80.18% to 53.26% at 210 min. The reusability of this catalyst was studied at the optimum condition up till four cycles for 1 h. The characterization of the reused catalyst showed a significant change in the structure and surface acidity due to the blockage of the surface acid sited by carbonaceous materials.