Abstract: The selective oxidation of methane to methanol over Pd/C catalysts generated from a PdCl2 precursor was investigated in oleum. Characterization of the catalysts was performed byX-raydiffraction,X-rayphotoelectron spectroscopy, high-resolution transmission electron microscopy, and CO adsorption. The major product in the oxidation reaction was methyl bisulfate, which was then hydrolyzed into methanol. Methane conversion of 23.6% with methanol selectivity of 69.5% and yield of 16.4% was achieved under the optimum conditions of 5%Pd/C, 30 μmol Pd, reaction temperature 180 ℃, methane pressure 4.0 MPa, reaction time4 h, and 50% sulfur trioxide concentration. After facile separation with the reactants and pretreatment, the catalyst could be reused several times with considerable stability. The selective oxidation of methane catalyzed by Pd/C catalysts in oleum possibly involved an electrophilic substitute mechanism. The catalytic performance was related to the Pd loading, dispersion, and particle size.

Key words: palladium, activated carbon, supported catalyst, methane, selective oxidation, methanol, oleum