Direct liquefaction of Mukah Balingian low-rank Malaysian coal: optimization using response surface methodology

Coal liquefaction of low-rank coals is of interest because of the formation of a liquid fuel with lower molecular weight and a higher H/C ratio than those of the parent coal, which itself is difficult to use. This study determined the optimum conditions for liquefaction of Mukah Balingian (MB) low-rank Malaysian coal using a supercritical water-tetralin mixture. Response surface methodology (RSM) based on central composite rotatable design (CCRD) was applied to optimize the combination effect of two important reaction variables, i.e. reaction temperature (degrees C) and solvent mixture ratios. The reaction was performed via a high-temperature, high-pressure batch-wise reactor system. A total of 13 individual experiments were conducted and the results showed that the RSM based on CCRD is very applicable to the coal liquefaction process studied in this system. The predicted optimum conditions for liquefaction of MB coal was 450 degrees C reaction temperature and 30 : 70 water-tetralin ratio, resulting in coal conversion and an oil yield of 70.6 and 66.1%, respectively. (C) 2010 Curtin University of Technology and John Wiley & Sons, Ltd.