Structure-Activity Relationships of Au/Al2O3 Catalyst for the Selective Oxidative Esterification of 1,3-Propanediol and Methanol

Graphical The efficient aerobic oxidative esterification reaction of 1,3-propanediol and methanol to form methyl 3-hydroxypropionate in the presence of 1.5 wt. % Au/Al 2 O 3 catalysts prepared using the deposition-precipitation or colloid-deposition method were investigated. Preparation methods and calcination temperature of catalyst played important role in improving the catalytic activity in this work. 1.5 wt. % Au/Al 2 O 3 catalysts were prepared using the deposition-precipitation or colloid-deposition method and calcined at different temperatures for the selective oxidative esterification reaction of 1,3-propanediol and methanol to form methyl 3-hydroxypropionate (3-HPM). The catalysts were characterized by nitrogen adsorption, transmission electron microscopy (TEM), X-ray diffraction (XRD), UV-Vis diffuse reflectance spectroscopy, X-ray photoelectron spectra (XPS), CO 2 temperature-programmed desorption (CO 2 -TPD) and NH 3 temperature-programmed desorption (NH 3 -TPD). The effect of the calcination temperature of the catalyst prepared by the deposition-precipitation method on the catalytic performance for the selective oxidative esterification of 1,3-propanediol was studied. The results showed that the conversion of 1,3-propanediol and the selectivity of 3-HPM increased at first and then decreased with the increase of the calcination temperature of catalyst. The highest conversion of 1,3-propanediol and selectivity of 3-HPM at the optimal calcination temperature of 350 °C were 92.0% and 88.5%, respectively. Considering the effects of preparation method and calcination temperature, it could be concluded that the metallic Au nanoparticles with appropriate particle size in coordination with the suitable amount of weak and middle acid and base sites, were favorable to the oxidative esterification of 1,3-propanediol and methanol to 3-HPM. Moreover, we found that the 1.5 wt. % Au/Al 2 O 3 catalyst could be effectively recovered without obvious decline of the catalytic properties.