CO_2 utilization as an oxidant in the dehydrogenation of ethylbenzene to styrene over MnO_2-ZrO_2 catalysts

摘要

MnO_2-ZrO_2 binary oxide catalytic system was applied for the effective utilization of CO_2 as an oxidant in the ethylbenzene dehydrogenation (EBD) to styrene monomer (SM). MnO_2-ZrO_2 oxides were prepared by co-precipitation method and characterized as solid solution mixture having surface area more than 100~2 g~(-1). 10% MnO_2-ZrO_2 mixed oxide catalyst exhibited conversion of 73% with the selectivity of 98% at 650 ℃. The MnO_2-ZrO_2 binary oxides were X-ray amorphous whereas the individual oxides (MnO_2 and ZrO_2) having much lower surface areas were crystalline in nature. As a result, MnO_2-ZrO_2 binary oxides exhibited greatly elevated catalytic activity for the conversion of ethylbenzene (EB) than those of individual oxides in the presence of CO_2. However, in the absence of CO_2 poor catalytic activity and stabilities were observed. Gradual enhancement of activities were demonstrated in the higher CO_2 to EB ratios. Hence, CO_2 had a profound role as a soft oxidant by improving both activity and stability in the EBD over MnO_2-ZrO_2 mixed oxide catalysts.