Catalytic Oxidation of Benzyl Alcohol by Gold Nanoparticles on Carbon Residue–Modified CoAlO_x Spinel

Stable and efficient gold catalysts can be alternative candidates to catalyze the primary alcohol oxidation for the sustainable chemical industry. We have synthesized a series of Au catalysts supported by spinel CoxAl-C modified with carbon skeleton for the alkali-free aerobic oxidation of benzyl alcohol. The influences of the Co/Al molar ratio and the residual carbon on the surface structure of gold catalysts were studied and correlated with their catalytic behavior. Characterizations including XRD, XPS and UPS, SEM and TEM, and N2 adsorption–desorption were operated to understand the chemical composition and surface metal states in different catalysts. The results suggested that under an appropriate Co/Al ratio, Au/Co1Al-C has a higher amount of Auδ+ induced by the promoted electronic environment. The presence of Co2+/Co3+ contributed to the formation of oxygen vacancies. The residual carbon skeleton increased the surface area and decreased the overall work function of the catalyst with an accelerated charge transfer between Au and the adsorbate. The faster alkali-free conversion rate of benzyl alcohol was achieved by Au/Co1Al-C and Au/Co2Al-C even under quite low temperatures. Approximately 82% benzaldehyde yield was obtained by Au/Co1Al-C with a TOF value of 2056 h–1 at 80 °C.