Continuous hydrogenation of CO₂-derived ethylene carbonate to methanol and ethylene glycol at Cu-MoO_x interface with a low H₂/ester ratio

The Cu-based catalysts have been widely employed in the hydrogenation of CO₂-derived ethylene carbonate (EC) to methanol (MeOH) and ethylene glycol (EG), but still suffered from some problems such as excess hydrogen/ester ratio, unsatisfactory MeOH selectivity and catalyst stability & deactivation. Herein, a MoO_x-promoted Cu/SiO₂ catalyst, which was prepared via a one-pot modified hydrothermal method and derived from copper phyllosilicate precursors, exhibited superior catalytic performance (89% MeOH yield and 99% EG yield) and good stability (>150 h) at a H₂/EC ratio (20). Remarkably, the turnover frequency (TOF) and space time yield of MeOH (STY_MeOH) reached up to 17.5 h⁻¹ and 0.207 g⋅g_cat⁻¹⋅h⁻¹, respectively, which are among the highest values in the literature data. The characterization results and kinetic studies revealed that modification of Cu species by MoO_x obviously changed the electronic properties of Cu species, reduced the activation energy and enhanced the Cu⁺/(Cu⁰ + Cu⁺) ratios. Such modification may lead to possible formation of Cu-O-Mo bond between Cu species and MoO_x species located on the periphery of Cu-MoO_x interface, which might strengthen the adsorption and activation of EC, stabilize the Cu nanoparticles, and thus improve the selectivity to MeOH and catalyst stability. In addition, MoO_x decoration had obvious effect on the strength and quantity of the surface acid sites.