Gold/Fe_<i>x</i>La_<i>y</i>-CeO_<i>z</i> Composite Oxides for Oxidative Esterification of Methacrolein: Effects of Highly Active Oxygen Species Based on Strong Metal–Support Interaction

Oxidative esterification of aldehydes in alcohols by one step has been of great interest. Gold catalysts are efficiently employed to produce methyl methacrylate (MMA) from methacrolein (MAL) with methanol (MeOH). A series of FexLay-CeOz composite oxides (FLC) were synthesized by impregnation method. Au/FLC catalysts were prepared by depositing Au nanoparticles on FLC using a modified deposition precipitation method. The effect of Fe–La composite oxide (FLO) with different molar ratio of Fe to La on the catalytic performance was detailed investigated. The results of H2-TPR and TEM revealed that the introduction of FLO led to the formation of strong metal–support interaction (SMSI) on the surface of Au/FLC catalyst. XPS, O2-TPD, Raman spectroscopy, and FTIR spectroscopy indicated that Au/FLC surface exhibited enhanced electron transfer and a higher abundance of active oxygen species compared to Au/CeO2. CO2-TPD and NH3-TPD analysis reveal that the incorporation of dopant enhances the abundance of strong basic sites in the catalyst. Au/FLC catalyst exhibited high activity under across various substrate concentrations especially in base-free environment. When the molar ratio of Fe to La was 1:1 as well as Au/MAL = 0.05 mol %, the conversion of MAL reaches 97.5%, the selectivity of MMA is 95.3%, and the turnover frequency (TOF) achieved at 487.5 h–1 with optimal performance. The excellent activity of Au/FLC can be attributed to the abundant active oxygen species and basic sites on its surface. The kinetics of gas–liquid–solid heterogeneous catalytic oxidative esterification reactions were studied. Additionally, a possible reaction mechanism was proposed.