Hydrogenating supercritical coal extraction with toluene, tetralin, molecular hydrogen and their mixtures

Abstract

Hydrogenating extraction of bituminous coal and lignite was investigated using toluene as extracting solvent, and molecular hydrogen and/or tetralin as hydrogenating agent. In non-isothermal experiments a fixed bed of coal was slowly heated from ambient temperature to 550 °C in a stream of pressurized toluene/H 2/tetralin mixture, and the extraction rates were continuously measured over the entire temperature range. The measured extraction rate profiles showed characteristic differences depending on the combination of solvent and hydrogenating agent. These differences were interpreted and compared with the thermodynamic phase behaviour of the solvent-H 2 system, to understand the physical and chemical steps involved in the complex mechanism of hydrogenating coal extraction. The fact that the addition of hydrogen during extraction had a negative effect on coal conversion and extract yield was also explained.