Oxidative carbonylation of methanol to dimethyl carbonate over Cu/AC catalysts prepared by microwave irradiation: Effect of La and Zr promoters

Abstract

Copper catalysts with a loading of 16.7 wt%, supported on activated carbon (AC) with the addtion of La or Zr, have been prepared by microwave heating methods and tested for the oxidative carbonylation of methanol to dimethyl carbonate (DMC). X-ray diffraction (XRD, temperature-programmed reduction (TPR), XPS), and scanning electron micrographs (SEM) have been carried out to examine the bulk and surface properties of the carbon-supported copper catalysts. It is found that the addition of La or Zr promoters favours the auto-reduction of copper precursors to metallic copper and leads to smaller and even nanoparticle-size Cu distributed on the surface of the carbon support which exhibt promising space-time yield of DMC of 480.2 and 585.2 mg·g^-1·h^-1, respectively. Meanwhile, the selectivity of DMC reached 95.7 and 90.3% and higher conversion of CH₃OH of approximately4.0 and 4.7% have been achieved surprisingly, even after five sets of relevant experiments. The improved catalytic performance of Cu/AC with the addition of La or Zr in the DMC synthesis is due to the presence of more metallic copper, more evenly distributed over the surface of the carbon support, with a significantly reduced particle size as compared with no La or Zr promoter.