Abstract: Catalyst beds in refinery reactors require periodic change out due to build-up of contamination and loss of activity. The instant invention mists a liquid chemical solvent in nitrogen carrier gas to solubilize oils and heavy hydrocarbons and to further desorb light hydrocarbons and remove hydrogen sulfide (H2S), to effect decontamination. This process can be advantageously combined with nitrogen cool-down processes in preparation for catalyst unloading.