LIQUEFACTION BEHAVIOR OF A SPANISH SUBBITUMINOUS - A COAL UNDER DIFFERENT CONDITIONS OF HYDROGEN AVAILABILITY

A Spanish subbituminous A coal was liquefied in a 250-ml autoclave for 1 h, at 17 MPa hydrogen pressure and 400 rpm stirring speed. The liqu id products were fractionated into oils, asphaltenes, and preasphalten es using pentane, toluene and THF as extractive solvents. The effect o f hydrogen availability on liquefaction yields was explored using diff erent tetralin:coal ratios under different temperatures. The results a re compared with those obtained in earlier studies [1,2], under differ ent hydrogen pressures and tetralin:coal ratios, and with other solven ts and with catalysts. Total conversion, asphaltenes, preasphaltenes a nd oils increase while gases decrease when the tetralin:coal ratio is raised, not observing further conversion over 2:1, 3:1, 4:1 and 6:1 ra tios, at 400, 425, 450 and 475 degrees C, respectively. Retrogressive reactions are produced at 475 degrees C for tetralin:coal ratios under 4:1 but not for higher ones. In order to obtain the highest conversio n (approximate to 84%), which coincides with vitrinite + exinite conte nt, 475 degrees C and 6:1 or higher tetralin:coal ratios have to be us ed. Such or higher conversions, can be obtained with more appropriate operating conditions (425 degrees C, 3:1 solvent:coal ratio) if better solvents or active catalysts are used. (C) 1998 Elsevier Science B.V. All rights reserved.