Effect of Support on Oxidative Esterification of 2,5-Furandiformaldehyde to Dimethyl Furan-2,5-dicarboxylate

Abstract

One-step oxidative esterification of 2,5-furandiformaldehyde (DFF) derived from biomass to prepare Dimethyl Furan-2,5-dicarboxylate (FDMC) not only simplifies the catalytic process and increases the purity of the product, but also avoids the polymerization of 5-hydroxymethylfurfural (HMF) at high-temperature conditions. Gold supported on a series of acidic oxide, alkaline oxide, and hydrotalcite was prepared using colloidal deposition to explore the effect of support on the catalytic activities. The Au/Mg3Al-HT exhibited the best catalytic activity, with 97.8% selectivity of FDMC at 99.9% conversion of DFF. This catalyst is also suitable for oxidative esterification of benzaldehyde and furfural. X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and CO2 temperature programmed desorption (CO2-TPD) were performed to characterize the catalysts. The results indicated that the medium and strong basic sites in the catalysts benefited for the absorption of intermediate agents and facilitated the oxidative esterification of aldehyde groups, while neutral or acidic supports tended to produce an acetal reaction. It is worth noting that basicity on the support surface reduced the electronic state of the Au nanoparticle (Auδ−) and, thus, enhanced the catalytic selectivity of oxidative esterification. This finding demonstrated that the support plays a crucial role in oxidative esterification.