Synthesis of n-Butanol From Ethanol Catalyzed by Pd@UiO-66 With Ligand Defects
UiO-66-xHAc 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-xHAc supports through an impregnation-reaction method to obtain Pd@UiO-66-xHAc catalysts,whose catalytic performance in the synthesis of n-butanol from ethanol was evaluated.By use of various characterization techniques such as N2 physical adsorption-desorption isotherm,X-ray diffraction analysis(XRD),transmission electron microscopy(TEM),NH3 temperature-programmed desorption(NH3-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.
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