PURPOSE: To remove industrially and advantageously chlorine in liquid 1,2- dichloroethane, by introducing a specific amount of ethylene into the 1,2- dichloroethane containing the chlorine, and catalytically reacting them in the presence of a catalyst supporting a specified amount of a metal chloride on a porous carrier under specific conditions.

CONSTITUTION: ≥2mol, particularly 3W10mol, based on 1mol chlorine, ethylene 2 is introduced into liquid 1,2-dichloroethane 1 containing the chlorine, and catalytically reacted at 40W160°C, particularly 40W120°C and 10W500hr-1, particularly 10W200hr-1 space velocity in the presence of a catalyst supporting ≤0.5wt%, preferably 0.1W0.5wt%, particularly 0.1W0.3wt% metal chloride, particularly ferric chloride or cupric chloride on a porous carrier, particularly active carbon or alumina in a reactor (A) to remove the chlorine corroding equipment, and causing abnormal reaction in the above-mentioned liquid 1 industrially and advantageously as compared with the conventional method. The resultant treated solution 3 can be directly fed to the thermal decomposition step.