助剂对CuO-ZnO-Al_2O_3催化剂在CO_2加氢制甲醇反应中性能的影响

采用共沉淀法制备了CuO-ZnO-Al2O3催化剂,并以金属氧化物为助剂对其进行了改性,在固定床连续流动反应装置上考察了6种助剂改性的CuO-ZnO-Al2O3催化剂对CO2加氢合成甲醇反应的催化性能。采用N2静态吸附、X射线衍射、H2-程序升温还原等方法对催化剂进行了表征。实验结果表明,用ZrO2或Ag2O改性CuO-ZnO-Al2O3催化剂后,在240℃、2.0MPa、重时空速3600h-1、n(H2):n(CO2)=3:1的反应条件下,CO2转化率提高了约2个百分点,甲醇选择性提高了约4个百分点,甲醇收率提高了约1个百分点;ZrO2改性增大了CuO-ZnO-Al2O3催化剂的比表面积,提高了催化剂表面Cu物种的分散度;Ag2O改性可能使CuO-ZnO-Al2O3催化剂产生了新的活性中心Ag+。

Effect of Promoter on Performance of CuO-ZnO-Al2O3 Catalyst for CO2 Hydrogenation to Methanol

CuO-ZnO-Al2O3 catalysts were prepared by co-precipitation and modified by addition of metal oxides as promoters.Effects of six chosen promoters on catalytic performance of the catalyst for hydrogenation of CO2 to methanol were studied in a fixed-bed plug flow reactor.Under reaction condition of 240 ℃,2.0 MPa,WHSV 3 600 h-1 and n(H2):n(CO2) 3:1,ZrO2-doped and Ag2O-doped CuO-ZnO-Al2O3 catalysts enhanced CO2 conversion by about 2 percentage points,methanol selectivity by about 4 percentage points,methanol yield by about 1 percentage point,correspondingly.Study of the catalysts by means of BET,XRD and H2-TPR indicated that doping of ZrO2 improved the specific surface area of catalyst and dispersion of copper on catalyst surface,and doping of Ag2O provided additional Ag+ active sites on CuO-ZnO-Al2O3 catalyst.