Oxidative Desulfurization Of Molybdovanadophosphate-based Ionic Liquid Catalyst

The massive emissions of oxysulphide and sulfate particulates from transportation fuel combustion, which lead to serious environmental pollution like acid rain and haze. Therefore, stringent fuel standards have been established to reduce the sulfur content. However, the traditional hydrodesulfurization technology can hardly cope with the challenges brought about by the increasingly stringent fuel standards. So the non-hydrodesulfurization technologies have attracted increasing attention. Nowadays, oxidative desulfurization(ODS) has become the hot topic and is regarded as one of the most promising techniques due to the mild reaction conditions and the high sulfur removal efficiency.Heteropoly acids(HPAs) are wildly used as catalysts in an oxidative desulfurization process because of their high catalytic activities. However, when hydrogen peroxide is used in ODS, there will produce the water-oil interface, which resulting the increase of the mass transfer resistance and the decrease of catalytic desulfurization effect. Meanwhile, it’s difficult to reclaim the HPAs. In order to solve the problems mentioned above, heteropolyacid-based ionic liquid and SBA-15 supported heteropolyacid-based ionic liquid were prepared, and their catalytic performance in the extractive catalytic oxidative desulfurization process(ECODS) was studied by using hydrogen peroxide as the oxidant and acetonitrile as the extraction agent. The innovations can be divided into the following two parts:(1) Three Keggin-type heteropolyacid-based catalysts, [C3H3N2(CH3)(C2H4)]5PMo10V2O40([C2MIM]PMo V2), [C3H3N2(CH3)(C4H8)]5PMo10V2O40([C4MIM]PMo V2) and [C3H3N2(CH3)(C6H12)]5PMo10V2O40([C6MIM]PMo V2), were synthesized by reacting molybdovanadophosphoric acid with imidazolium bromides and characterized by Uv-vis, FTIR, XRD, 1H NMR and TG-DTA. Their catalytic desulfurization efficiencies were investigated in the ECODS, which followed the order: [C2MIM]PMo V2 < [C4MIM]PMo V2 < [C6MIM]PMo V2. The factors influencing the efficiency of sulfur removal were studied by using [C6MIM]PMo V2 as catalyst. Under the optimal conditions, a nearly 100% sulfur removal efficiency was achieved. The catalyst could be recycled six times without significant loss in catalytic desulfurizationefficiency.(2) A series of catalysts, ionic liquid modified SBA-15(ILSBA) doped with H5PMo10V2O40(HPMo V2) have been synthesized and characterized by FTIR、XRD、TEM、BET and TG-DTA. The catalysts were used for the removal of dibenzothiophene(DBT) in model oil. The influence factors of desulfurization efficiency have been studied systematically including the reaction temperate, the reaction time, the loading amount of molybdovanadophosphoric acid, the amount of oxidant and catalyst. It was observed that the sulfur content of DBT can be reduced from 500 ppm to 2 ppm under the selected condition. Moreover, the catalytic activity for different sulfur compounds was mainly affected by the electron density of sulfur atom, the lower the electron density, the sulfur is harder to be removed. What is more, the catalyst could be recycled 7 times with a high sulfur removal efficiency above 97%, which could be ascribed to the strong electrostatic interaction between ILSBA and HPMo V2.