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Selective oxidation of water-containing ethanol in the presence of excess ethanol provides a one-step preparation of ethyl acetate. Acetic acid is formed from the oxidation of ethanol catalyzed by a supported Pd catalyst and is further catalytically esterified to ethyl acetate by the protons dissociated from acetic acid. The difference of the catalytic performance between hydrophilic and hydrophobic Pd catalysts was investigated by a continuous fixed-bed reactor run at 95 °C, 35.4 atm, and a air/ethanol molar ratio of 2.37. The experimental results indicated that, after the induction period, the conversion of ethanol catalyzed by a styrene−divinylbenzene copolymer (SDB)-supported Pd catalyst is more than 20 times that catalyzed by a γ-alumina-supported Pd catalyst at a weight hourly space velocity (WHSV) of 2.4 h-1. However, it may be caused by weak metal−support interactions and the formation of palladium(II) acetate during the reaction. For the Pd/SDB catalysts, the Pd clusters were leached out concomitantly with the growth of Pd particles. Inductively coupled plasma (ICP) optical emission spectroscopy characterizing the fresh and used catalysts shows that about 10% of Pd was leached after 60 h on stream. Extended X-ray absorption fine structure (EXAFS) spectroscopy results further indicate that the average particle size of the Pd clusters on SDB support increases from 6 to 20 Å.

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