载体Al/Si比对Cu-ZnO-ZrO2催化剂上CO2加氢合成甲醇的影响

用直接合成法制备了不同铝硅物质的量比Al-SBA-15(β)(β=n(Al)/n(Si)=0,0.02,0.03,0.05)介孔分子筛,并采用浸渍法制备了金属负载量m=35%的CZZ/Al-SBA-15(β)负载型介孔催化剂,考察了Al/Si比对负载催化剂结构和性能的影响。采用N_2吸附-脱附、X射线衍射(XRD)、H_2程序升温还原(H_2-TPR)、CO_2吸附(CO_2-TPD)、NH3吸附(NH3-TPD)和透射电子显微镜(TEM)等手段对样品进行了表征,在固定床反应器上评价了其CO_2加氢合成甲醇的催化性能。实验结果表明,CZZ/Al-SBA-15(β)具有介孔结构,Al的引入不但增加了载体表面酸性位点,同时还提高了催化剂表面铜分散度(DCu%)和铜比表面积(SCu)以及促进了Cu~+-O-Zn活性位的形成,从而大大提高了催化剂的活性。其中CZZ/Al-SBA-15(0.03)催化剂的甲醇选择性达到26%,与不掺铝的CZZ/Al-SBA-15(0)催化剂相比,甲醇选择性提高了11%,但随着掺Al量的继续增加,酸性太强,CO_2吸附能力下降,活性反而降低。

Influence of Al/Si Ratio of Catalyst Support on CO2 Hydrogenation to Methanol Catalyzed by Cu-ZnO-ZrO2

A series of mesoporous aluminosilicate supports (Al-SBA-15(β),β=n(Al)/n(Si)=0,0.02,0.03, 0.05)with diverse Al/Si molar ratios were prepared,and CuO-ZnO-ZrO nanoparticles were loaded on Al-SBA-15 sup-ports by a simple impregnation method (CZZ/Al-SBA-15 (β),m=35%).The effect of Al/Si ratios of mesoporous support on structure and properties of the supported catalysts were investigated by employing N2 adsorption-desorp-tion,X-ray diffraction (XRD),transmission electron microscopy (TEM),H2 temperature programmed reduction (H2-TPR),CO2 temperature-programmed desorption (CO2-TPD)and N2 O titration technique (N2 O-RFC)to deter-mine the textual structure and physicochemical properties of CZZ/Al-SBA-1 5 (β)samples.The catalytic activities of these catalysts for CO2 hydrogenation to methanol were determined in a fixed-bed reactor.Experimental results showed that CZZ/Al-SBA-1 5 (β)has a mesoporous structure,the addition of Al not only increased the surface acid sites of the supports,but also improved the DCu%,SCu of the samples and promoted the formation of Cu+-O-Zn active sites.CZZ/Al-SBA-15(0.03)catalyst showed a high methanol selectivity (26%),which increases by 11% compared with non-doped aluminum CZZ/Al-SBA-15(0)catalyst.However,the overdoping of Al element results in an unduly high acidity of support,thus attenuating CO2 absorption and catalytic activity.