Effects of Pb and Mg doping in Al 2O 3-supported Pd catalyst on direct oxidative esterification of aldehydes with alcohols to esters

Abstract

An investigation was carried out of oxidative esterification of aldehydes with alcohols and oxygen to corresponding esters over Pb, Mg-doped Al 2O 3-supported Pd catalyst. This catalyst was prepared by impregnating method and characterized by X-ray diffraction, differential scanning calorimetry, X-ray photoelectron spectroscopy, and transmission electron microscopy. The results showed that Pd atoms with Pb atoms formed bimetallic Pd 3Pb crystals, and Mg existed on the support as MgO with electron effect on Pd 3Pb crystals. The reactions of aldehyde with alcohol in the presence and absence of oxygen over the doped and undoped Pd catalysts were examined to evaluate the effects of Pb and Mg. It was found that the doping agents Mg had positive effect on reaction rate acceleration only in the presence of oxygen, Pb or the collaboration of Pb and Mg had positive effect on reaction rate acceleration and selectivity enhancement in the presence of oxygen or not.