Run ZBF was conducted to determine the amount of sulfur and nitrogen removal from SRC-I/process solvent mixture in the absence of a hydrotreating catalyst. Negligible nitrogen and sulfur removal resulted from this experiment. The hydrogen content of the coal liquid increased slightly over that of the feedstock. In similar studies using other coal liquids some sulfur removal (10 to 40%) was noted under non-catalyzed conditions. Several commercial NiMo supported catalysts were analyzed for silica contents using atomic absorption. These results revealed that catalysts with large micropore size structures also contain high silica content (up to 22.5 weight percent). Several short duration runs (12 to 110 hours) were conducted in the CLTU to gather data on catalyst coking mechanisms. Using the SRC material mixed with a process solvent or creosote oil (30 weight percent SRC), solid materials were observed to form and precipitate in the latter portions of the reactor bed. The reactor system was modified to prevent the accumulation of these incompatible solids which would result in premature termination of the experimental runs. In the catalyst regeneration study (HDN-30, NiMo), a spent catalyst was regenerated and then used to hydrotreat a coal liquid consisting of 10% Synthoil II liquid mixed with raw anthracene oil. This regenerated catalyst gave equal and somewhat superior performance with respect to heteroatom removal compared to that of the fresh catalyst. A second regeneration of this same catalyst loading has been conducted and the regenerated catalyst is being prepared for a third cycle. The spent catalyst lost approximately 33% of its total surface area, yet regeneration recovered 97% of the fresh catalyst area.