Transformations of sulphur compounds in high-sulphur coals during reduction in the potassium/liquid ammonia system☆

The two types of high-sulphur coals Mequinenza and Illinois No. 6, in the initial form and subjected to potassium/liquid ammonia reduction, were analysed by atmospheric pressure–temperature programmed reduction (AP–TPR) method. It has been shown that preliminary demineralisation was beneficial for AP–TPR measurements because of the removal of calcium compounds. The reduction of sulphides and disulphides in the potassium/liquid ammonia system was found to lead to formation of aromatic and aliphatic thiols. The presence of the latter is better manifested in the AP–TPR kinetograms when the measurements are performed in the presence of a special reducing mixture. It has been shown that the coal reduction in the potassium/liquid ammonia system apart from transformations of non-thiophene sulphur groups also leads to breaking up of the C–S bonds in some thiophene systems.