A catalyst is prepared by adding a water soluble aliphatic polyhydroxy compound such as a polyhydroxy alcohol or a carbohydrate (e.g., sucrose) to an aqueous solution of chromic acid and subsequently introducing the resulting mixture into a hydrocarbon material. The hydrocarbon-containing mixture is heated in the presence of hydrogen sulfide to convert the chromium catalyst precursor to a solid chromimum-containing catalyst. Hydroconversion processes utilizing the catalyst to convert oil, coal, and mixtures thereof are also provided.