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

Abstract

Sulphur dioxide and soot produced during coal combustion are the main air pollution sources and increased emission of PM 2.5 (particle matter with an aerodynamic diameter less than or equal to 2.5 mm) in China. In this investigation, two imidazolium ionic liquids (ILs), namely, 1-butyl-3-methyl imidazolium bisulphate ([C 4 C 1 im][HSO 4 ]) and 1-carboxymethyl-3-methylimidazolium bisulphate([HOOCCH 2 mim][HSO 4 ]), were used to remove sulphur from coal combined with 30 % hydrogen peroxide (H 2 O 2 ) based on chemically oxidative desulphurization. The experimental results indicate that H 2 O 2 played a dominant role in removing inorganic sulphur but only partially decreased organic sulphur. The [C 4 C 1 im][HSO 4 ]-H 2 O 2 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][HSO 4 ]-H 2 O 2 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, -CH 3 , -CH 2 -, and-OH declined, while ÀCOOH increased after the IL-H 2 O 2 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.

Ionic liquids as alternative solvents for energy conservation and environmental engineering

“…have examined over the ability of oxidative desulphurization of coal, as the sulfur dioxide and soot which emerges out during the combustion of coal are the main sources of air pollution. In their investigation, they have used imidazolium based ILs, namely, 1-butyl-3-methylimidazolium bisulfate and 1-carboxymethyl-3methylimidazolium bisulfate to extract sulfur from coal [37] Patra et al analyzed the effect of nitro groups on desulfurization efficiency of benzyl substituted imidazolium-based ionic liquids. The liquid-liquid microextraction approach was adopted and the parameters influencing extraction efficiency, such as the effect of IL volume, concentration and rotation period, were extensively studied.…”

Comparison of three methods for the sequential extraction of lignite pretreated by ionic liquid

“…[15,16] Ionic liquids are also used to investigate coal properties. [17,18] Li et al treated coals with ionic liquids of different concentrations to study the changes in pore characteristics and fractal dimension. [19] The results show that the total pore volume of coal samples treated with ionic liquid is larger than that of the coal sample treated with water.…”

Experimental Study on Organic Sulfur Removal in Bituminous Coal by a 1-Carboxymethyl-3-methyl Imidazolium Bisulfate Ionic Liquid and Hydrogen Peroxide Solution

“…They also found that the mixture of the [HOOCCH 2 mim][HSO 4 ]–30% H 2 O 2 solution can remove 16.76% of organic sulfur, and imidazolium ionic liquids are more efficient than the pyridinium ones. 26 …”