An experimental study of the effect of ionic liquids on the low temperature oxidation of coal

Fourier transform infrared spectroscopy (FTIR) and constant heating rate experiments were performed to study the low temperature oxidation of coal treated by an ionic liquid, 1-allyl-3-methylimidazolium chloride. The inerting effect of the ionic liquid toward the low temperature oxidation process is discussed. The results show that: (1) The hydroxyl content associated with hydrogen bonds, the aliphatic methyl content, the methylene group content, and the ether oxygen bond content are reduced in the treated coal. At the same time the content of aromatic CC bonds is constant but these chemical bonds weaken and some substituted aromatic hydrocarbon content increases while other types decrease. This demonstrates that (AMIm)Cl dissolves and destroys the coal surface microstructure; (2) The oxygen consumption of the treated coal is less than what is seen in raw coal. The CO, CO2, C2H4, and C2H6 content from the treated coal is reduced compared to the untreated coal; (3) The apparent activation energy for the oxidizing reaction is different in the treated and raw coals. Micro-structural changes and macroscopic gas production allow us to conclude that (AMIm)Cl can effectively inhibit low temperature oxidation of coal.