CeO2/Beta composite catalysts in dimethyl carbonate synthesis from CO2: effect of preparation method on surface oxygen species

Two kinds of CeO2/Beta composite catalysts were prepared by precipitation method (CeB-p) and hydrothermal method (CeB-h), respectively. The physicochemical properties of all samples were studied in detail by combining XRD, XPS, SEM, TEM, N-2 sorption, NH3-TPD and CO2-TPD techniques. CeB-p catalyst exhibited a higher dimethyl carbonate (DMC) yield than the CeB-h catalyst at the similar conditions for DMC synthesis from CO2 and methanol. This enhanced activity of CeB-p catalyst was attributed to enhanced acid-base properties modulated by abundant surface lattice oxygen species rather than oxygen vacancies. Compared with the inertly adsorbed methoxy induced by the oxygen vacancy enriched CeB-h, abundant surface lattices oxygen species in CeB-p catalyst facilitated the formation of weakly absorbed methoxy species, which resulted in the shift of the rate-determining step and the reduction of reaction energy barrier. This study offered guidance for the rational design and fabrication of high-performance DMC synthesis catalysts based on CeO2/Beta composite.