柠檬酸辅助固相研磨法制备铜基催化剂及在CO_2加氢合成甲醇反应中的性能研究

通过柠檬酸辅助固相研磨法制备铜基催化剂,采用XRD、TPR、TG-DSC、SEM、BET、TEM、XPS、CO_2-TPD等手段对催化剂性能进行表征.结果表明室温固相研磨的前驱体在惰性气体N_2中焙烧使体系中的CuO绝大部分被原位还原成Cu~0,不需外加H_2还原,直接制得了C/I-Cu/ZnO催化剂,催化剂具有中孔.利用高压固定床连续反应装置对催化剂活性进行了评价,结果表明,柠檬酸用量、前驱体焙烧温度、焙烧升温速率等条件对催化剂活性产生影响,当C_6H_8O_7/(Cu+Zn)摩尔比为1.2/1并Cu/Zn摩尔比1/1,前驱体在N_2中以3 K·min~(-1)升温速率于623 K焙烧3 h,制得的C/I-Cu/ZnO催化剂比表面积最大,Cu~0粒径最小,在CO_2加氢合成甲醇反应中表现出最佳的活性,CO_2转化率、甲醇选择性和产率分别达到了28.28%、74.29%和21.01%.与外加H_2还原的C/H-Cu/ZnO催化剂相比,原位还原C/I-Cu/ZnO催化剂比表面积较大,Cu~0的粒径较小,活性较高.

Preparation of Cu-based Catalyst by Solid-phase Grinding Method with Citric Acid Assisting and Performance Research in Methanol Synthesis Reaction from CO2 Hydrogenation

The Cu-based catalyst was direct prepared by a solid state grinding method with citric acid assisting. The catalysts were characterized by the means of XRD, TPR, TG-DSC, SEM, BET, TEM, XPS, CO₂-TPD etc. The results showed that when the precursor obtained by solid state grinding at room temperature was calcined in N₂ inert atmosphere, the C/I-Cu/ZnO catalyst with mesoporous structure was obtained directly since most of CuO had been reduced in-situ to Cu⁰ without further H₂ reduction. The catalyst activity was tested by using high pressure fixed bed continuous reaction device. The results showed that the catalyst activity was affected by the citric acid amount, precursor calcination temperature and calcination heating rate. When C₆H₈O₇/(Cu+Zn) molar ratio was 1.2/1 (Cu/Zn=1/1, molar ratio), the precursor was calcined in N₂ atmosphere at 623 K for 3 h with calcination heating rate of 3 K·min^-1, the C/I-Cu/ZnO catalyst was obtained with the maximum surface area and smallest particle size of Cu⁰. This catalyst showed the best catalytic activity in the methanol synthesis reaction from CO₂ hydrogenation, and the CO₂ conversion, the selectivity and yield of methanol up to 28.28%, 74.29% and 21.01%, respectively. The in-situ reduction C/I-Cu/ZnO catalyst showed a large surface area, small Cu⁰ particle size and high catalytic activity compared with the traditional catalyst reduced by additional H₂.