Abstract:

Catalytic oxidative desulfurization (ODS) of model oil and commercial oil samples was investigated using an air-assisted performic acid oxidation system with a phase transfer or emulsion catalyst comprising a quaternary ammonium salt-based heteropolyoxometalate. Different emulsion catalysts with a Keggin type heteroployoxometalate anion (containing W, Mo, and V) and cetyltrimethylammonium bromide cation were prepared and characterized by X-ray fluorescence, Fourier transform infrared spectroscopy, and scanning electron microscopy. [C₁₆H₃₃N(CH₃)₃]₃[PW₉Mo₃O₄₀] was the most effective catalyst in the current oxidation system, which reduced the sulfur content of the model oil from 1275 μg/g to 57 μg/g. The reactivity order of different model sulfur compounds was thiophene < dibenzothiophene < 4,6-dimethyldibenzothiophene. The ODS of model sulfur compounds followed first order kinetics with apparent activation energy from 29 to 27 kJ/mol. The catalysts also performed efficiently in the ODS of the industrial oil samples, including untreated naphtha, light gas oil, heavy gas oil, and Athabasca oil sands derived bitumen, for which sulfur removal rates were 83%, 85%, 68% and 64%, respectively.

Key words: Catalytic oxidative desulfurization, Performic acid oxidation, Emulsion catalyst, Heteropolyoxometalate, Air oxidation