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以尿素为沉淀剂,采用均相沉淀法成功制备了层状Cu/Zn/Al水滑石化合物.将前驱体材料经焙烧、还原后得到Cu/ZnO/Al_2O_3催化剂,并将其用于CO_2加氢合成甲醇反应.采用X射线衍射(X-ray diffraction,XRD)、热重(thermogravimetric,TG)分析、扫描电镜(scanning electron microscope,SEM)、X射线荧光(X-ray fluorescence,XRF)分析、N_2吸附、H_2程序升温还原(H_2-temperature program reduction,H_2-TPR)、氧化亚氮(N_2O)反应吸附、CO_2程序升温脱附(CO_2-temperature program desorption,CO_2-TPD)技术对所制备的样品进行表征.结果表明,相对于传统共沉淀法,以尿素作为沉淀剂,通过均相沉淀法所制备的前驱体的结晶度更高、催化剂比表面积更大、金属Cu的分散度更好.另外,采用回流处理可以获得更好的效果.活性评估结果表明,O_2转化率随金属Cu比表面积的增大而增加,而甲醇选择性则与催化剂表面碱性位的分布有关.因此,采用尿素回流处理均相沉淀法制备的Cu/ZnO/Al_2O_3催化剂的甲醇收率最高.
The layered Cu / Zn / Al hydrotalcite compound was successfully prepared by homogeneous precipitation using urea as precipitating agent.The Cu / ZnO / Al 2 O 3 catalyst was obtained by calcination and reduction of the precursor material, and was used for the hydrogenation of CO 2 The synthesis of methanol was studied by X-ray diffraction (XRD), thermogravimetric (TG) analysis, scanning electron microscope (SEM) and X-ray fluorescence (XRF) H 2 -TCP, H 2 -TPR, CO 2 -TPD and CO 2 -TPD were applied to the prepared samples The results show that compared with the traditional coprecipitation method, the precursors prepared by the homogeneous precipitation method have higher crystallinity, higher specific surface area and better dispersibility of metal Cu with urea as the precipitating agent.In addition, The results of the activity evaluation showed that the O 2 conversion rate increased with the increase of Cu specific surface area and the selectivity of methanol was related to the distribution of basicity sites on the catalyst surface.Therefore, Homogeneous precipitation process was refluxed for maximum yield of methanol Prepared Cu / ZnO / Al_2O_3 catalyst.