Coal liquefaction with solvent augmentation by heavy oil residues in presence of disposable iron catalyst

Coal liquefaction experiments were carried out in batch autoclaves with Point of Ayr coal, a process-derived recycle solvent and heavy oil residues (HORs) under a range of conditions. Before the experiments iron sulfide was precipitated on to the coal, mostly at 6 wt% Fe, and the experiments were carried out under a modest hydrogen overpressure. Two HORs were used, namely the highly aliphatic Forties AR and the more aromatic decant oil produced from fluidized catalytic cracking of oil. The influence of amount of HOR added, temperature and time on the percentage dissolution of coal was considered and related to the I-I-donor contents of the various solvents measured by a chemical test using sulfur as a hydrogen acceptor. It was found that an augmented solvent mixture containing 20 wt% decant oil in process-derived recycle solvent (PDRS) produced the greatest conversion values under the optimum conditions of 400 degrees C for 1 h, with synergistic action in terms of hydrogen transfer. The coal liquid produced from repeat solvent augmentation experiments with decant oil was subjected to hydrocracking with simulated solvent recycle, and the changes in composition of the liquid product were considered, particularly in relation to the fate of the main hydrogen donors present in process-derived recycle solvents. Reasonable conversion to lower-boiling-point material was found, but the H-donor content was not made up to its original value. There was an indication that the PDRS was hydrocracked preferentially relative to the decant oil. Copyright (C) 1996 Elsevier Science Ltd.