Fabrication of Au Nanoparticles Supported on One-Dimensional La₂O₃ Nanorods for Selective Esterification of Methacrolein to Methyl Methacrylate with Molecular Oxygen

Abstract

Here we demonstrate a simple and cost effective synthetic route for selective esterification of aldehydes with high productivity in the presence of molecular oxygen (O2) on a gold supported lanthanum oxide (Au/La2O3) nanoparticle catalyst. Au nanoparticles with sizes of 2–7 nm supported on 1D La2O3 nanorods with diameters between 20 and 50 nm were synthesized by a room-temperature surfactant-assisted single-step preparation method. The as-synthesized catalyst was thoroughly characterized by powder XRD, SEM, HR-TEM, H2-TPR, XPS, TGA/DTA, FTIR, BET, EXAFS, and UV–visible spectroscopy. This prepared nanostructured catalyst was found to be highly effective in the liquid phase synthesis of methyl methacrylate (MMA) via direct oxidative esterification of methacrolein (MA) with a high turnover number of ∼1136. The effect of various reaction controlling parameters like reaction temperature, pressure, and time of reaction was investigated and studied. High methacrolein conversion of 89% with high methyl methacrylate selectivity of 98% was attained without the use of any external additives. The synergistic effect between the surface AuNPs and La2O3 nanorods plays an important role toward the activity of the catalyst.