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Selective Oxidation of Amino Alcohols to Amino Acids over Au Supported on Monoclinic ZrO2: Dominant Active Sites and Kinetic Study

Au supported on monoclinic ZrO2 (Au/m-ZrO2) prepared by deposition–precipitation method showed excellent catalytic performance in the aerobic oxidation of amino alcohols to amino acids, i.e., glycine, alanine, serine, β-alanine, and 2-aminobutyric acid. The Au particle size and valence distribution of the gold species were adjusted by calcination temperature, as demonstrated by XRD, TEM, UV–vis DRS, XPS, and H2-TPR, which significantly influenced the catalytic activity but not the selectivity of amino acids. Metallic gold atoms on the surface were shown to be the active sites by the correlation between reaction rate per mole of metallic Au and Au particle size. The kinetics of oxidation of monoethanolamine (MEA) was studied in detail, and the results indicated that MEA oxidation is a first-order reaction with an activation energy of 52.8 kJ·mol–1.