Atmospheric-pressure temperature-programmed reduction study of high-sulfur coals reduced in a potassium liquid ammonia system

Abstract

Two high-sulfur coals have been subjected to an atmospheric-pressure temperature-programmed reduction study (AP-TPR). The studies were performed on both raw and potassium/liquid ammonia reduced samples. The reduction of coals in the potassium/liquid ammonia system was shown to induce conversion of sulfide and disulfide groups into thiol groups. AP-TPR studies performed with addition of the reducing mixture provided evidence for the presence of different types of thiols. The possibility of cleavage of the C-S bonds in thiophenes was indicated. A favorable effect of the reducing mixture on sulfur recovery was observed in the AP-TPR method, while the calcium compounds occurring in coal were found to be responsible for significant deformation of the kinetograms obtained. The effect of extraction with dichloromethane on sulfur compounds in coal was established, leading to a supposition of sulfur being mainly bonded with the macromolecular part of coal.