Thermal and catalytic liquefaction of high ash Indian coals: Kinetics, mechanism, and product characterization

Abstract In this study, the direct coal liquefaction (DCL) of high‐ash Indian coals was studied. The DCL experiments were carried out with a 1 wt.% Fe 2 O 3 catalyst in a 200 mL reactor within a temperature range of 400–450°C, using tetrahydronaphthalene (tetralin) as solvent. The process yielded gas, liquid, and residue, along with water. The liquid fraction was classified as hexane soluble (oil), toluene soluble (asphaltene), and tetrahydrofuran soluble (pre‐asphaltene). The maximum conversions were 72.57 and 67.45 wt.%, and the oil yields of 42.33 and 39.43 wt.% were observed for lignite coal at 60 min of residence time and 450°C for catalytic and thermal liquefaction, respectively. For the maximum concentration of pyrite of 29.43% in lignite coal, the oil yield was maximum. A hypothetical six‐lumped kinetic model was employed. The activation energy values were in the range of 50–300 kJ/mol. The gas sample analysis indicated that methane production was peaking at 51.31 vol.%.