Phosphomolybdic acid (PMA) and nickel, cobalt and potassium salts of PMA have been found to be very effective catalyst precursors for direct liquefaction of Wyodak coal when impregnated onto the feed coal. PMA was sulfided at the temperatures of 125-450 degrees C, and analyzed by a variety of analytical techniques. The catalytic activities of these partially sulfided phosphomolybdates were determined both when added as particulate material directly to the reaction mixture and when impregnated from aqueous solutions onto coal. The THF and resid conversions with the sulfided materials were higher when impregnated onto coal, however presulfiding is detrimental to catalyst precursor performance. The effectiveness of these materials was related to their physical characteristics and elemental and structural compositions. THF and resid conversions of oil-agglommerated Wyodak coal impregnated with PMA were also determined. (C) 2000 Elsevier Science B.V. All rights reserved.