不同助剂对CuO-ZnO/SBA-15催化CO_2加氢制甲醇性能影响的研究

以硅质骨架结构介孔分子筛SBA-15为载体,采用浸渍法合成CuO-ZnO/SBA-15(CZ/SBA-15)、CuO-ZnO-MnO_2/SBA-15(CZM/SBA-15)、CuO-ZnO-ZrO_2/SBA-15(CZZ/SBA-15)三组多孔催化剂,在固定床反应器上评价了各组催化剂催化CO_2加氢合成甲醇的性能,同时结合N_2吸附-脱附(BET)、X射线衍射(XRD)、H_2程序升温还原(H_2-TPR)、程序升温脱附(H_2-TPD、CO_2-TPD)、N_2O滴定、X射线光电子能谱(XPS)、透射电子显微镜(TEM)等表征研究了不同助剂对CO_2催化加氢制甲醇的影响。结果表明,催化剂中的金属氧化物改变了SBA-15分子筛载体的孔径大小和比表面积;催化剂CuO-ZnO-MnO_2/SBA-15、CuO-Zn O-ZrO_2/SBA-15中铜的分散度(D_(Cu))和比表面积(A_(Cu))更大,表面CuO粒径更小,更易被还原;相比Mn-O簇,Zr-O簇为增强了碱性位点,提高了甲醇选择性。此外,CuO-ZnO-ZrO_2/SBA-15具有更高的氧空位浓度,催化活性更好,其甲醇选择性为25.02%,与CuO-ZnO/SBA-15、CuO-ZnO-Mn O_2/SBA-15相比分别提高了28%和136.9%,催化效果最好。

Effect of additive on CuO-ZnO/SBA-15 catalytic performance of CO2 hydrogenation to methanol

Three kinds of porous catalysts CuO-ZnO/SBA-15 (CZ/SBA-15), CuO-ZnO-MnO₂/SBA-15 (CZM/SBA-15) and CuO-ZnO-ZrO₂/SBA-15 (CZZ/SBA-15) were synthesized by impregnation method with a siliceous framework mesoporous molecular sieve SBA-15. The performance of all catalysts for catalytic hydrogenation of CO₂ to methanol was evaluated on a fixed bed reactor, combined with N₂ adsorption-desorption (BET), X-ray diffraction (XRD), H₂ temperature-programmed reduction (H₂-TPR), temperature programmed desorption (H₂-TPD, CO₂-TPD), N₂O titration, X-ray photoelectron spectroscopy (XPS) and transmission electron microscope (TEM). The results show that the introduction of metal oxide in the catalyst changes the pore size and specific surface area of the SBA-15 molecular sieve support. The CuO-ZnO-MnO₂/SBA-15 and CuO-ZnO-ZrO₂/SBA-15 have high copper dispersion (D_Cu%), large specific surface area (S_Cu), small surface CuO particle size, and easy to be reduced. Compared with the Mn-O cluster, the Zr-O cluster enhances the basic site and improves the methanol selectivity. In addition, CuO-ZnO-ZrO₂/SBA-15 has the highest oxygen vacancy concentration and better catalytic activity among three catalysts. The methanol selectivity of CuO-ZnO-ZrO₂/SBA-15 is 25.02%, which is 28% and 136.9% higher than those of CuO-ZnO/SBA-15 and CuO-ZnO-MnO₂/SBA-15, respectively.