CO2加氢制低碳醇CuFe基催化剂中的Mn助剂效应

采用共沉淀法制备了一系列Mn掺杂的CuFeZnK催化剂, 研究了Mn助剂对催化剂的结构及催化CO₂加氢制低碳醇合成性能的影响. 结果表明, 引入适量的Mn(质量分数2.1%)能有效提高低碳醇的选择性和时空收 率(STY), 在320 ℃和5 MPa的条件下, CO₂的转化率为29.4%, 低碳醇选择性(CO-free)达到23.2%, 时空收率达到41.1 mg·{\mathrm{g}}_{\mathrm{c}\mathrm{a}\mathrm{t}}^{-\mathrm{1}}·h^?1, 且低碳醇在总醇中的比例达到96.9%. 利用X射线衍射(XRD)、 N₂吸附-脱附实验、 X射线光电子能谱(XPS)、 透射电子显微镜(TEM)和氢气程序升温还原(H₂-TPR)等手段对制得催化剂进行表征, 结果表明, 适量Mn可以起到结构助剂的作用, 减小Cu颗粒尺寸的同时促进Fe₅C₂相的形成, 从而构建丰富的Cu-Fe₅C₂活性界面, 用于低碳醇合成. 而过量的Mn反而会堵塞催化剂的孔道, 覆盖活性位点, 降低了催化性能.

Effect of Mn Promoter on CuFe-based Catalysts for CO2 Hydrogenation to Higher Alcohols

A series of Mn promoted CuFe based catalysts with different Mn contents was synthesized with the co-precipitation method. The promoting effect of Mn on CuFe based catalyst in CO₂ hydrogenation to higher alcohol（HA） was studied. The catalytic results show the HA selectivity and space time yield（STY） could be effectively improved by introducing moderate Mn. The optimized catalyst denoted as 2.1MCFZ-K with 2.1%（mass fraction） Mn content exhibits the best catalytic performance with CO₂ conversion of 29.4%， HA selectivity（CO-free） of 23.2%， HA space time yield of 41.1 mg·{\mathrm{g}}_{\mathrm{c}\mathrm{a}\mathrm{t}}^{-\mathrm{1}}·h^?1， and C₂₊OH/ROH fraction of 96.9% at 320 ℃ and 5 MPa. X-ray diffraction（XRD）， N₂ sorption experiments， X-ray photoelectron spectroscopy（XPS）， transmission electron microscopy（TEM） and H₂ temperature-programmed reduction（H₂-TPR） experiments reveal that Mn as a structural promoter with moderate content can reduce the particle size of Cu and promote the formation of Fe₅C₂ active phase， thus fabricating rich Cu-Fe₅C₂ active interface for HA synthesis. Overly high Mn content can block active sites， inhibiting the catalytic activity.