Mechanism study on the influence of surface properties on the synthesis of dimethyl carbonate from CO2 and methanol over ceria catalysts
The direct synthesis of dimethyl carbonate(DMC)from CO2 and methanol has attracted much at-tention as an environmentally benign and alternative route for conventional routes.Herein,a series of cerium oxide catalysts with various textural features and surface properties were prepared by the one-pot synthesis method for the direct DMC synthesis from CO2 and methanol,and the struc-ture-performance relationship was investigated in detail.Characterization results revealed that both of surface acid-base properties and the oxygen vacancies contents decreased with the rising crystallinity at increasingly higher calcination temperature accompanied by an unexpectedly vol-cano-shaped trend of DMC yield observed on the catalysts.In situ diffuse reflectance infrared Fouri-er transform spectroscopy(DRIFTS)studies indicated that the adsorption rate of methanol is slow-er than that of CO2 and the methanol activation state largely influences the formation of key inter-mediate.Although the enhanced surface acidity-basicity and oxygen vacancies brought by low-temperature calcination could facilitate the activation of CO2,the presence of excess strongly basic sites on low-crystallinity sample was detrimental to DMC synthesis due to the preferred for-mation of unreactive mono/polydentate carbonates as well as the further impediment of methanol activation.Moreover,with the use of 2-cyanopyridine as a dehydration reagent,the DMC synthesis was found to be both influenced by the promotion from the rapid in situ removal of water and the inhibition from the competitive adsorption of hydration products on the same active sites.
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