CATALYST PERFORMANCE IN RESID CONTAINING RECYCLE SOLVENTS

A number of problems were encountered in evaluating catalyst performan ce in full-range liquefaction recycle solvents containing sizable amou nts of resid, unconverted coal and ash. In a liquefaction plant in whi ch only distillate products are produced, resid is recycled to extinct ion. In such a configuration the feed to the plant will contain a dist illate to coal ratio of less than one with the remaining portion of th e solvent made up of residual material having reduced donor capacity. In recycle solvents obtained from the Wilsonville pilot plant, which w ere produced when running in the distillate-only mode, the presence of an insoluble fraction that was easily converted into THF insoluble ma terial was found in the residual fraction of all the Wilsonville recyc le solvents that have been tested in our laboratory. When using these recycle solvents for evaluating catalysts, conversion of this residual fraction leads to abnormally high coal conversions even under the mil dest of conditions. The presence of catalysts that have accumulated in all of the recycle solvents masks the effect of added fresh catalysts on both dissolution of the coal and 565 degrees C+ resid conversion. Results from this study have shown that catalyst testing in these solv ents requires careful control of the components in the residual fracti on. Results from liquefaction of Wyodak coal in recycle solvents conta ining up to 1060 mg freshly added Mo per kg maf coal indicates that co al conversion, pentane solubles and 565 degrees C- distillate yields i ncrease as Mo concentration increases. The activity of recycled Mo is much greater than freshly added Mo. Exceptional activity with nanomete r-size iron oxide in the absence of any Mo was also observed.