Designing Alkaline-Rich Ba/MnO2 Catalysts for Efficient Oxidative Coupling of Alcohols and Amines at Low Temperatures

Abstract

In this work, a series of alkaline earth metal-modified manganese oxide catalysts were prepared via the impregnation method and applied to the oxidative coupling reaction of alcohols and amines to imine. The prepared catalysts were characterized by X-ray diffraction (XRD), N2-adsorption, field emission-scanning electron microscopy (FE-SEM), H2 temperature-programmed reduction (H2-TPR), NH3-temperature-programmed desorption (NH3-TPD), CO2-temperature-programmed desorption (CO2-TPD) and X-ray photoelectron spectroscopy. Among the catalysts, Ba/MnO2 showed the best catalytic performance in the reaction, which possess highest Mn3+/Mn4+ ratio, surface weak basic sites and a relat[*Corresponding author. Email: baoqiang@nepu.edu.cn (Qiang Bao)] ively small number of weak acidic sites. Lattice oxygen mobility and Mn3+/Mn4+ ratio were found to play the important roles in the catalytic activity of aerobic reactions. The weak and medium basic sites on the catalyst surface can further promote the alcohol-amine oxidative coupling process, as they serve as active centers for the activation of benzyl alcohol, which is the rate-determining step for this oxidative coupling reaction.