Effect of K₂O on adsorption and reaction of CO₂ and CH₃OH over Cu-Ni/ZrO₂-SiO₂ catalyst for synthesis of dimethyl carbonate

ZrO₂-SiO₂(ZrSiO) supported Cu-Ni-K₂O catalyst for synthesis of dimethyl carbonate (DMC) was prepared by using isovolumetric impregnation. Based on IR, TPR, TPD and micro-reactor techniques, the effect of K₂O on adsorption and reaction of CO₂ and CH₃OH over the catalyst was studied. The results showed that the addition of K₂O has obvious influence on the charge distribution of active sites on Cu-Ni/Zr-SiO catalyst, and increases the intensity of CO₂ horizontal adsorption state, while descends the intensity of dissociation state of methanol. When the K₂O content n(K)/n(Cu+Ni) is above 15%, K₂CO₃ is formed on the catalyst. Moreover, the main reaction products of CO₂ and CH₃OH on Cu-Ni-K₂O/ZrSiO catalyst are still DMC, H₂O, CO and CH₂O, and with the addition of K₂O, the conversion of reactants and the selectivity for DMC increase, but the selectivity for by-products decreases.