Study Of Direct Synthesis Of Dmc From CO₂and Methanol On The Composite Oxide Catalysts

With the increasing attention to global warming and energy crisis, the utilization of CO2becomes more and more important. Carbon dioxide has attracted more and more intense attention for its advantages including the wide source and the low cost etc. One-step synthesis of DMC using CO2and CH3OH as raw materials, has the vital significance in synthetic chemistry, effective use of C1resources, cost reduction, sustainable development and so on. This catalytic conversion of CO2has become one of the hottest topics in the catalysis field.As one kind of the heterogeneous catalyst, metal oxide catalyst has many advantages, such as the easier to separation from the liquid phase products thus recycle the catalysts, and the relavtively high catalytic activity for one-step synthesis of DMC using CO2and CH3OH as raw materimals.In our experiment, we prepared a series of ceria-zirconia composite catalysts by different preparation methods including co-precipitation and citric acid sol-gel method, and found that the ceria-zirconia composite catalysts prepared by citric acid sol-gel method exhibited higher catalytic performance. Ce0.8Zr0.2O2prepared by two different methods, whose optimal calcinations temperature was600℃, exhibited the best activity. The optimal reaction temperature was150℃for one-step synthesis of DMC from CO2and CH3OH on different ceria-zirconia composite catalysts prepared by two different methods, and higher reaction pressure was more advantageous to the direct synthesis reaction. In addition, the structures of these catalysts were characterized by XRD and H2-TPR. The characterization results suggested that the Ce0.8Zr0.2O2catalyst, which was prepared by two different methods, were formed stable solid solution, and the catalyst exhibited excellent high-temperature thermal stability. The catalysts including CeO2and Ce0.8Zr0.2O2solid solution exhibited a better reduction performance compared with ZrO2catalyst. Ce0.8Zr0.2O2solid solution catalyst, which was prepared by citrate sol-gel method, was more reducible at the low temperature than the CeO2catalysts and Ce0.8Zr0.2O2prepared by co-precipitation method. Finally, the catalytic performance of the other metals modified Ce0.8Zr0.2O2were evaluated.