Finally, the effects of reaction conditions were investigated on conversion of low-rank coals using a Texas subbituminous coal. To find the optimum reaction conditions which can minimize the retrogressive reactions while enhancing hydrogenation, several reaction conditions such as single-staged liquefaction (SSL) and temperature-programmed liquefaction (TPL) were compared. The effect of reaction solvents on the liquefaction was also studied using hydrogendonor solvents (e.g. tetralin and decalin), a non-donor solvent (e.g. 1-methylnaphthalene) and a recycle solvent (Wilsonville middle distillate). Ammonium tetrathiomolybdate (ATTM) was chosen as the catalyst precursor. Three impregnation methods, including preswelling, incipient wetness and slurrying were applied to investigate the effect of impregnation methods on the activity of the catalyst for liquefaction of the Texas subbituminous coal.

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