Monolithic ZnxCe1−xO2 catalysts for catalytic synthesis of dimethyl carbonate from CO2 and methanol
In this paper, a series of ZnxCe1−xO2 (x = 0.00, 0.05, 0.10, 0.15, and 0.20) nanoparticles were synthesized via an aqueous-phase coprecipitation method. The ZnxCe1−xO2 nanoparticles were coated on honeycomb ceramics to prepare monolithic catalysts, and the catalytic activity of the monolithic catalysts was investigated for the direct synthesis of dimethyl carbonate (DMC) from CO2 and methanol in a continuous tubular fixed-bed reactor. The as-prepared catalysts were fully characterized by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), N2 adsorption/desorption isotherms, H2-temperature-programmed reduction (H2-TPR), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and CO2-temperature-programmed desorption (CO2-TPD). The characterization results showed that doping Zn ions into the ceria lattice formed a fluorite-like solid solution and modified the structure and surface properties of the catalysts. Among all the monolithic ZnxCe1−xO2 catalysts, the monolithic Zn0.10Ce0.90O2 catalyst showed the highest catalytic activity with a methanol conversion of 20.5% with DMC selectivity of 82.1% at 160 °C and 2.4 MPa in the absence of any dehydrating agents. This superior catalytic activity was mainly attributed to a series of better properties, such as larger specific surface area (i.e. 179.9 m2 g−1), higher oxygen vacancy concentration, and the unique structure of the monolithic catalyst (e.g., removing by-product of water in time). This study provides a valuable design strategy for highly efficient direct synthesis of DMC using monolithic catalysts in the fixed-bed reactor.
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