Ceria nanostructured catalysts for conversion of methanol and carbon dioxide to carbonate

In this study, ceria (CeO2) with three different shapes (nanooctahedra, nanocubes, nanorods) was synthesized via hydrothermal method and evaluated for carbonylation reaction. Off these three nanostructures, the nanorod ceria was doped with CaO, NiO, CuO, and CoO by wet impregnation method. The obtained catalysts were characterized by X-ray diffraction (XRD), NH3/CO2-TPD, X-ray fluorescence (XRF), Fourier Transform Infrared Spectroscopy (FTIR), and N2 physisorption to determine the crystal size and phases, acid-base properties, metal loading, and surface properties. The materials were used as catalyst for activation of CO2 and methanol carbonylation reaction to dimethyl carbonate (DMC) at 140 °C and 30 bar for a reaction duration of 3 h. Our results indicated that the shape of the nanostructured ceria influences the DMC yield with the CeO2 nanorod catalyst producing the highest DMC yield (1.6 mmol) followed by nanooctahedra (1.5 mmol) and nanocubes (1.0 mmol). Moreover, the catalytic tests showed 100% DMC selectivity and the catalytic activities showed a decreasing trend in the following order: CeO2 > CoO/CeO2 > NiO/CeO2 > CaO/CeO2 > CuO/CeO2. The materials characterization and evaluation results suggested that CeO2 nanorod (111) interface enhanced the surface basicity and activity of CO2 hydrogenation to methanol while the CeO2 octahedral sites improved the stability of catalyst. The reusability of the CeO2 was tested by conducting four consecutive cycles and it was noted that the catalytic activity of CoO/CeO2 remained relatively stable with small changes after each run. © 2019