A desolidification process enables the isolation and extraction of solid additives from an unreacted petroleum residue stream. In a hydrocracking process that mixes a solid additive with a petroleum residue feedstock to convert the petroleum residue to higher-value distillates, the desolidification process enables the recovery of the unreacted petroleum residue for conversion to a saleable product. The desolidification process involves the mixture of one or more solvents with a slurry in which solids are integrated in the petroleum residue to generate a mixture having a decreased density and viscosity as compared to the slurry, which facilitates removal of the solids.