Abstract: The invention relates to a process for recovering the transition metal component of catalysts used in the hydroconversion of heavy hydrocarbonaceous materials. In accordance with the invention, a slurry of a transition metal catalyst and hydrocarbon is catalytically desulfurized resulting in a desulfurized product and a solid residue containing the transition metal. The transition metal may be recovered by coking the residue and then dividing the coker residue into two portions are combusted with the flue dust from the first combustion zone being conducted to the second combustion zone. The flue dust from the second combustion zone is treated with ammonia and ammonium carbonate in order to obtain ammonium molybdate.