활성이 저하된 촉매를, 일산화 탄소 및/또는 수소를 함유하는 환원성 가스로 접촉 처리한다. 또, 상기 환원성 가스로 접촉 처리한 후, 산화성 가스로 접촉 처리하면 보다 효과적으로 촉매를 부활할 수 있다. 염소 제조용 촉매로서는, 루테늄 촉매, 특히 산화루테늄을 함유하는 촉매가 바람직한 대상이 된다.
A catalyst having decreased activity is subjected to a contact treatment with a reducing gas containing carbon monoxide and/or hydrogen. Also, the catalyst can be effectively activated by being treated by contacting with an oxidizing gas after having been treated by contacting with the reducing gas. As the catalyst for production of chlorine, a ruthenium catalyst, particularly a catalyst containing ruthenium oxide is suitably activated.