Desulfurization of coal using four ionic liquids with [HSO4

Abstract

Sulfur dioxide produced from Coal-fire power plant are the main sources of air pollution and PM2.5 (the aerodynamic diameter less than or equal to 2.5 μm) which may result in multiple short term and long term health impacts. In this investigation, four ionic liquids, i.e. 1-butyl-3-methyl imidazolium bisulfate([C4C1im][HSO4]), 1-carboxymethyl-3-methylimidazolium bisulfate([HOOCCH2mim][HSO4]), N-butylpyridinium bisulfate([C4Py][HSO4]) and 1-carboxymethyl-3-methylpyridinium bisulfate([HOOCCH2Py][HSO4]), were used to remove sulfur from coal combining with 30% hydrogen peroxide (H2O2) based on chemically oxidative desulfurization. The experimental results of FTIR and XPS indicate that ionic liquids could enhance the oxidation of organic sulfur in H2O2, where [HOOCCH2mim][HSO4]-H2O2 solution can remove 16.76% of organic sulfur, much better than the single 30% H2O2 aqueous solution. Generally, imidazolium ionic liquids are more favorable for organic sulfur removal compared to pyridinium ones. Carboxyl group tethered on imidazolium cation could improve the oxidability of H2O2 due to the formation of peroxycarboxylic acid group. The stronger intramolecular H-bonding interaction of pyridinium ionic liquids is the structural reason for their relatively weak sulfur removal ability.