Disclosed is a method for separating a chlorine-containing species from an aqueous solution of the chlorine-containing species in a catalytic hydrocarbon conversion process that includes the step of oxidizing a spent chloride-containing hydrocarbon conversion catalyst, the spent hydrocarbon conversion catalyst including a hydrocarbon residue formed thereon. The oxidizing forms a flue gas including chlorine-containing species, water, and oxides of carbon. The method further includes contacting the flue gas with a water scrubbing stream to dissolve at least a portion of the chlorine-containing species in the water scrubbing stream to form an aqueous acid solution and contacting the aqueous acid solution with a hygroscopic liquid to generate dehydrated hydrogen chloride gas. Still further, the method includes contacting the dehydrated hydrogen chloride gas with additional spent chloride-containing hydrocarbon conversion catalyst to sorb chlorine onto the additional spent chloride-containing hydrocarbon conversion catalyst.