焙烧温度对MnZnOx物化性质及催化性能的影响

采用湿化学共沉淀法制备了MnZnO_x固溶结构催化剂,考察了焙烧温度对催化剂物化性质和催化性能的影响。采用X射线衍射（XRD）、X射线光电子能谱（XPS）、N₂吸附-脱附、CO₂-TPD（程序升温脱附）及H₂-TPR（程序升温还原）等手段对不同焙烧温度下催化剂物化性质进行了分析表征。结果表明,焙烧温度对MnZnO_x晶相组成、孔结构性质、二氧化碳吸附特性及表面氧空位浓度等物化性质影响较大。500 ℃焙烧条件下制得的MnZnO_x催化剂形成了具有丰富的表面氧空位、较大的二氧化碳吸附量和介孔孔容且溶质组分分散均匀的固溶结构。在反应压力为3.0 MPa、反应空速（GHSV）为14 400 mL/（g·h）、V（氢气）∶V（二氧化碳）∶V（氮气）=72∶24∶4条件下,MnZnO_x催化剂于380 ℃表现出优异的催化性能,甲醇选择性为86.1%、二氧化碳转化率为16.0%、甲醇时空产率（STY）达0.68 g_MeOH /（h·g_cat）。

Effect of calcination temperature on physicochemical properties and catalytic performance of MnZnOx

The rapid development of global industry had aggravated a large amount of greenhouse gas(CO₂)emissions.It is of great significance to convert CO₂to methanol by reduction and activation of high energy hydrogen molecules.Wet chemical co-precipitation strategy was employed to fabricate the MnZnOxsolid solution catalyst which realized the hydrogenation of CO₂to methanol and the influence of calcination temperature on physicochemical properties and catalytic performance of the catalysts were fully investigated in this paper.X-ray diffraction(XRD),X-ray photoelectron spectroscopy(XPS),N2 adsorptiondesorption,CO₂-TPD and H2-TPR techniques were used to characterize the physicochemical properties of the catalysts calcined at various temperature.The results showed that the calcination temperature had significant impact on the crystalline phase compositions,pore structure properties,CO₂adsorption characteristics and surface oxygen vacancy concentrations of MnZnOx.Although the homogeneous solid solution structure could be formed at lower temperature,the crystallinity of the main crystal phase ZnO was inferior.Too high calcination temperature made the solute component MnxOycrystallize in the form of Mn₃O₄ and the mixed crystal phase of Mn₃O₄ and ZnO was formed in the structure,resulting in the decrease of specific surface area and mesoporous pore volume.MnZnOxcatalyst calcinated at 500℃had a solid solution structure with abundant surface oxygen vacancy,large CO₂adsorption and mesoporous pore volume and uniform dispersion of solute components.Under the conditions as follows:reaction pressure of 3.0 MPa,reaction space velocity(GHSV)of 14400 mL/(g·h)and V(H2)∶V(CO₂)∶V(N2)=72∶24∶4,the MnZnOxat 380℃exhibited excellent catalytic performance with methanol selectivity of 86.1%,CO₂conversion of 16.0%and methanol STY of 0.68 g MeOH/(h·gcat).