Confined Ruthenium Nanoparticles as an Effective Catalyst for Aerobic Oxidation of Aqueous Ethanol to Acetic Acid
Hongyi Ding, Xiang Qi, Xuehai Yun, Jingmin Ge, Ye Tian, Xiaodong Lei, Fazhi Zhang
Abstract
Confined ruthenium nanoparticle catalyst, Ru/Mg1–xFexO, is easily prepared by hydrogen reduction of a Mg2+Fe3+Ru3+-layered double hydroxides (MgFeRu-LDHs) precursor at controlled temperature. The hydrogen reduction temperature has an enormous effect on sample composition, structure, and morphology. A precipitation-embedding mechanism is proposed for preparation process of Ru catalyst. Ru0 is initially precipitated from LDHs precursor and is accompanied by the transformation from the LDHs precursor into sjoegrenite. With reduction temperature rises, Ru nanoparticles are implanted by weak crystalline Mg1–xFexO. Ru/Mg1–xFexO sample reduced at 300 °C has higher catalytic performance for aerobic oxidation of ethanol, with ethanol conversion 94.1% and acetic acid selectivity 95.6%. We speculate that MgO breaks the O–H bond, ruthenium breaks the C–H bond, and FeOx provides lattice oxygen and oxygen vacancies to promote the catalytic cycle. The confinement effect increases the effective contact between the catalytic active site and the substrate, which contributes to O2 activation and ethanol adsorption.