K_2O助剂对合成碳酸二甲酯用Cu-Ni/ZrO_2-SiO_2催化剂的吸附和催化性能的影响

Effect of K_2O on Adsorption and Reaction of CO_2 and CH_3OH over Cu-Ni/ZrO_2-SiO_2 Catalyst for Synthesis of Dimethyl Carbonate

用等体积浸渍法制备了ZrO2 SiO2 (ZrSiO)表面复合氧化物负载的Cu Ni催化剂 ,并用IR ,TPR ,TPD及微反技术考察了K2 O助剂对CO2 和CH3OH在Cu Ni/ZrSiO催化剂表面上的吸附及合成碳酸二甲酯 (DMC)反应性能的影响 .结果表明 :加入K2 O助剂使CO2 在催化剂表面上的吸附增强 ,当n(K) /n(Cu +Ni) =15 %时 ,CO2 在催化剂表面上吸附后生成K2 CO3;CH3OH在催化剂表面上的解离吸附态 (CH3O-和H+)的吸附减弱 ;CO2 和CH3OH在Cu Ni/ZrSiO催化剂表面上反应的主要产物为DMC ,H2 O ,CO和CH2 O ;随着K2 O助剂的加入 ,反应转化率及DMC选择性提高 ,副产物 (CO和CH2 O)的选择性下降 .根据实验结果 ,探讨了K2 O对催化剂表面活性中心电荷分布的影响 .

ZrO 2-SiO 2(ZrSiO) supported Cu-Ni-K 2O 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 K 2O on adsorption and reaction of CO 2 and CH 3OH over the catalyst was studied. The results showed that the addition of K 2O has obvious influence on the charge distribution of active sites on Cu-Ni/ZrSiO catalyst, and increases the intensity of CO 2 horizontal adsorption state, while descends the intensity of dissociation state of methanol. When the K 2O content n(K)/n(Cu+Ni) is above 15%, K 2CO 3 is formed on the catalyst. Moreover, the main reaction products of CO 2 and CH 3OH on Cu-Ni-K 2O/ZrSiO catalyst are still DMC, H 2O, CO and CH 2O, and with the addition of K 2O, the conversion of reactants and the selectivity for DMC increase, but the selectivity for by-products decreases.