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Abstract In order to meet the stringent environmental and industrial legislation on fuel specifications, sulfur compounds have to be removed efficiently from fuels. The requirement to produce ultralow-sulfur fuels (S < 10 ppm) has stimulated many works in the area of conventional hydro-desulfurization (HDS) method. Oxidative desulfurization (ODS), as an alternative or complementary technology to HDS for deep desulfurization, is conducted with high selectivity and reactivity to sterically hindered S compounds under mild reaction conditions. In the ODS process, using an appropriate oxidant in the presence of a catalyst, organic sulfur compounds can be oxidized selectively to their corresponding sulfoxides and sulfones, which can be easily removed by different separation methods. Having great catalytic characteristics, polyoxometalate materials have been utilized as a vital class of catalysts for deep desulfurization of fuels. In the past few decades, ODS of fuels using polyoxometalate as catalyst has drawn much attention, and various studies have been carried out in this area. Here, we give a critical review for the removal of sulfur compounds from liquid fuels (mostly from diesel and model fuels) by ODS via homogeneous and heterogeneous polyoxometalate catalysts.

Densities and viscosities of solutions of poly(ethylene glycol) (PEG) in water and ethanol and solutions of poly(propylene glycol) (PPG) in ethanol were measured at (293.2, 308.2, 313.2, 318.2, 328.2, 333.2, and 338.2) K. The number-average molecular weights for PEG were 200, 300, and 6000, and that for PPG was 2025. The density and viscosity data were fitted by second- and third-order polynomial equations, respectively, with respect to mass fraction of polymer at each temperature.