溶胶-凝胶自燃烧法制备的CuO-ZnO/Al_2O_3及催化二氧化碳加氢制甲醇的性能研究

Preparation of CuO-ZnO/Al_2O_3 by Sol-gel Auto-combustion Method and Its Catalytic Property for Methanol Synthesis from CO_2 Hydrogenation

采用溶胶-凝胶自燃烧法,以柠檬酸为燃料制备了多种CuO-ZnO/Al2O3催化剂.利用N2静态吸附(BET)、X射线衍射(XRD)、扫描电子显微镜(SEM)、X-射线光电子能谱(XPS)和H2程序升温还原(H2-TPR)等方法研究了柠檬酸与硝酸盐比例关系对催化剂物化性质,形貌和还原性能的影响.并将其用于二氧化碳加氢制甲醇反应,考察催化剂的CO2转化率,甲醇选择性以及甲醇时空收率等催化性能.实验结果表明,当柠檬酸用量等于化学计量比时,CuO-ZnO/Al2O3催化剂的催化性能最好,当柠檬酸用量大于化学计量比时,催化性能次之,且变化不大,但当柠檬酸用量小于化学计量比时,催化性能明显降低.这一结果与其物化性质和还原性能有关,当柠檬酸用量等于或大于化学计量比时,催化剂中CuO颗粒较小,分散均匀,且分散度高.

Various CuO-ZnO/Al2O3 catalysts have been synthesized by citric acid sol-gel auto-combustion method and their performances for methanol synthesis from CO2 hydrogenation have been investigated. The effects of citric acid/nitrate ratio on physieochemical, morphologies and catalytic properties were studied by BET, XRD, SEM, XPS and H2-TPR. Catalytic activities of the prepared catalysts for methanol synthesis were tested in fixed-bed flow reactor. The results indicated that when 100% of stoichiometrie amount of citric acid was used, the CuO-ZnO/Al2O3 catalyst exhibited an optimum catalytic behavior. The catalyst showed relatively smaller particle size, higher surface area and more uniform Cu dispersion.