Influence of ZnO doping and calcination temperature of nanosized CuO/MgO system on the dehydrogenation reactions of methanol

摘要

Pure and doped catalysts were prepared with ZnO dopant concentration (0.04–0.08?mol) by wet impregnation method followed by calcination at 350–650?°C. The prepared solids were characterized by X-ray diffraction, N2-adsorption at ?196?°C and the methanol conversion as the catalytic probe reaction. The results revealed that the crystallite size and ordering of CuO phase decrease by ZnO-doping for samples calcined at 350–550?°C. Opposite trends were observed by increasing ZnO amount to 0.08?mol (i.e. 9.21?wt%). The specific surface area (SBET) and the catalytic activity of pure catalyst increase by increasing the calcination temperature to 550?°C and/or increasing the amounts of ZnO up to certain extent reaching to a maximum at 7.07?wt% ZnO; above this concentration catalytic activity of doped samples decreases. But at calcination temperature above 550?°C, the catalytic activity and selectivity decrease. The prepared catalysts are selective towards formaldehyde and methyl formate formation.