配体缺陷Pd@UiO-66催化乙醇合成正丁醇

Synthesis of n -Butanol From Ethanol Catalyzed by Pd@UiO-66 With Ligand Defects

选择乙酸作为调节剂,采用溶剂热合成法制备含有不同配体缺陷数量的UiO-66-xHAc载体,通过浸渍-反应法将金属Pd封装入UiO-66-xHAc中,得到了一系列Pd@UiO-66-xHAc催化剂,考察了其催化乙醇合成正丁醇的反应性能。通过N2物理吸附-脱附、X射线衍射(XRD)、透射电子显微镜(TEM)、氨气程序升温脱附(NH3-TPD)、热重分析(TG)等表征技术,发现改变乙酸用量时,配体缺陷数量会随着乙酸用量的提高而增加,同时催化剂的Lewis酸的强度和数量也随之线性增加。虽然增加乙酸用量能够提升乙醇的转化效率,但是过量的Lewis酸量反而会促进乙醚等副产品的生成。当使用Pd@UiO-66-50HAc催化剂时,在温度为250℃、压力为2 MPa、LHSV为4 h^(-1)的反应条件下,乙醇转化率可以达到60.1%,同时正丁醇的选择性达到40.5%,正丁醇的收率达到24.2%。

UiO-66-x HAc supports with different quantities of ligand defects were prepared using acetic acid as a modulator by a solvothermal method.Subsequently,Pd metals were encapsulated in these UiO-66-x HAc supports through an impregnation-reaction method to obtain Pd@UiO-66-x HAc catalysts,whose catalytic performance in the synthesis of n-butanol from ethanol was evaluated.By use of various characterization techniques such as N_(2)physical adsorption-desorption isotherm,X-ray diffraction analysis(XRD),transmission electron microscopy(TEM),NH 3 temperature-programmed desorption(NH 3-TPD),and thermogravimetric analysis(TG),it has been found that the increase in the amount of acetic acid results in a corresponding increase in the number of ligand defects,as well as the strength and concentration of Lewis acids present in the catalysts.Although increasing the amount of acetic acid can enhance the conversion of ethanol,an excess amount of Lewis acid tends to promote the formation of by-products such as ethyl ether.When using the Pd@UiO-66-50HAc catalyst,under reaction conditions of temperature 250℃,pressure 2 MPa,and LHSV 4 h^(-1),the conversion of ethanol can reach 60.1%,while the selectivity and yield of n-butanol is up to 40.5%and 24.2%,respectively.