A detailed study of postconsumer polymer coliquefaction with lignite influenced by two acidic and two oil-soluble catalyst precursors is presented in this article. The conversion of reacting solids into gaseous and liquid products was determined in four initial series of coprocessing experiments performed with and without catalysts on a suite of four heavy organic solvents. Based on the results obtained, two newer series of experiments were also designed and carried out, aimed at the optimization of this complex transformation using this time lignite oxidatively pretreated. It was found that the mentioned hydroconversion is a promising way of hydrocarbon synthesis and that oxidatively pretreated lignite proved superior to the raw material. It was also found that the oil-soluble catalysts employed indicated a particularly noticeable activity increase, influencing, thus, the efficacy of the conversions achieved. (C) 2000 John Wiley & Sons, Inc.