TEMPERATURE-STAGED LIQUEFACTION OF SELECTED TURKISH COALS

Four Turkish coals, along with two American coals for comparison, were liquefied at various temperature-staged conditions in bench-scale microautoclave reactors, 9,10-Dihydrophenanthrene was used as a strong donor solvent, and ammonium tetrathiomolybdate was added to some reactions as a catalyst precursor for the in situ generation of a hydrogenation catalyst. The combination of a potent hydrogen donor and good catalyst were sufficient to provide conversions greater-than-or-equal-to 90% (d.a.f. basis) for all coals in this study. The most important role of the solvent is in the initial breakdown of the coal. A catalyst is important for upgrading of the initial products, but it is also active in promoting hydrogen transfer from the solvent to the coal. For reactions of Can lignite in the absence of catalyst, most of the hydrogen transferred to the coal derives from the solvent; when a sulfided molybdenum catalyst is added, most of the hydrogen consumed comes from gas-phase H2. Oil (hexane-solubles) yield increases linearly with increasing hydrogen consumption. The best results in the present study were a 98.8% conversion with 72.2% oil yield, which were obtained with Seyit Omer lignite with 2:1 solvent:coal ratio, added catalyst, and 30 minutes each at 275 and 425-degrees-C.