Synergic Effect of Manganese Oxide on Ceria Based Catalyst for Direct Conversion of CO2 to Green Fuel Additive: Catalyst Activity and Thermodynamics Study

The relationships between structure and activity in heterogeneous catalysis have created a demand for new preparation routes for improved surface properties. In the present study, a number of Manganese-Cerium catalysts with varying manganese contents were prepared using a surfactant-template method and tested for CO2 conversion in dimethyl carbonate (DMC) synthesis at elevated temperature and CO2 pressure. The ManganeseCerium catalysts were characterized by N-2-sorption, XRD, CO2-TPD, NH3-TPD, SEM, TEM and Raman spectroscopy. The catalytic activity was closely related to the acidic and basic sites of the synthesized catalysts. The basic sites are responsible for the activation of CO2 and contribute to the formation of methoxy groups in the reaction. The weak and moderate acidic sites are responsible for the activation of methanol. It was found that the Ce-1-Mn-0.125 catalyst has the highest basicity and acidity compared to Ce-1-Mn-0.25 and Ce-1-Mn-1 catalysts. The optimization of the reaction conditions was investigated batchwise at various reaction parameters including reaction time and temperature. The reusability of the catalyst and the effect of the amount of manganese on the catalytic activity of Manganese-Cerium catalysts were also investigated. In addition, the calculation of the Gibbs free energy and heat of reaction was performed using chemical equilibrium modeling.