Dimethyl carbonate synthesis over ZnO–CaO bi-functional catalysts

•ZnO-CaO catalyst exhibited an interesting DMC yield (41.2 %) with the Zn/Ca molar ratio of 4:1.•ZnO-CaO catalysts with suitable acidic/basic sites were beneficial for the DMC synthesis, attributing to the synergistic effect between ZnO and CaO.•A bi-functional mechanism for the DMC synthesis over ZnO-CaO catalysts was proposed.

ZnO–CaO catalysts were prepared and tested for the synthesis of dimethyl carbonate (DMC) from urea and methanol. Meaningfully, the bi-functional catalysts ZnO–CaO exhibited noticeable DMC yield (41.2%) with the Zn/Ca molar ratio of 4:1, which might ascribe to the synergistic effect between ZnO and CaO. The plausible mechanism for the DMC synthesis was as follows: urea was activated to generate metal isocyanato group on the acid sites and subsequently nucleophilic attacked by the activated methanol on the basic sites.

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