A new process has been developed to oxidize CO at low temperatures (<423 K) in vent streams that also contain halogenated compounds and water, A PdCl2-CuCl2 catalyst supported on carbon was successfully implemented to treat the oxidation reactor vent stream of a terephthalic acid plant that contained water, CH3Br and other organic compounds in addition to CO. The CH3Br remained intact during the treatment and did not deactivate the catalyst. In this catalyst system, palladium remained as a molecular Pd(II) species while solid Cu2Cl(OH)(3) was the active copper phase. The formation of stable Cu2Cl(OH)(3) was essential for activity and stability of the catalyst, After obtaining a stable catalytic activity for six months in a pilot plant test with a side stream of real vent gases, the first installation and operation of the process were made successfully to handle 50,000 Nm(3)/h of vent stream in a terephthalic acid plant.