Effort of ionic liquids with [HSO4]- on oxidative desulphurization of coal

Sulphur dioxide and soot produced during coal combustion are the main air pollution sources and increased emission of PM2.5 (particle matter with an aerodynamic diameter less than or equal to 2.5 mu m) in China. In this investigation, two imidazolium ionic liquids (ILs), namely, 1-butyl-3-methyl imidazolium bisulphate ([C(4)C(1)im][HSO4]) and 1-carboxymethyl-3-methylimidazolium bisulphate([HOOCCH(2)mim][HSO4]), were used to remove sulphur from coal combined with 30 % hydrogen peroxide (H2O2) based on chemically oxidative desulphurization. The experimental results indicate that H2O2 played a dominant role in removing inorganic sulphur but only partially decreased organic sulphur. The [C(4)C(1)im][HSO4]-H2O2 solution is able to remove 47.44 % of the total sulphur in coal and nearly 100 % of the inorganic sulphur while the [HOOCCH(2)mim][HSO4]-H2O2 solution can remove 16.76 % of organic sulphur with a weaker ability to reduce inorganic components. According to the FTIR spectra analysis, the results show that the proportion of -SH, -CH3, -CH2-, and-OH declined, while -COOH increased after the IL-H2O2 treatment due to the oxidation enhancement in the presence of ionic liquids. Sulphur element compositions were measured using XPS, and the results also show that ionic liquids are favourable for improving the oxidation of -SH, -S-, and thiophene into sulphoxide and sulphone, which were extracted during the ionic liquid phase.