Liquefaction of low-rank coals with hydriodic acid and microwaves

A novel method for the chemical liquefaction of low-rank coals in relatively moderate conditions and short reaction times is presented. Using concentrated hydriodic acid as the reaction medium, microwaves as the energy source, and reaction times of 20 min at 230 degrees C, up to 50% of the organic carbon of coal can be extracted with THF. The study of the process shows that temperature of the reaction and time are the main factors affecting the desulfurization process. The redox potential and the nucleophilicity of the concentrated hydriodic acid were the driving force of the reaction as experiments with other acids or lower acid concentrations gave worse results.