REMOVAL OF DEPOSITED PALLADIUM

PURPOSE:In preparing a carbonyl compound by bringing an olefin type unsaturated hydrocarbon and oxygen into contact with a catalyst comprising palladium and copper, to remove deposit witout damaging a reactor and to prevent reduction in function, by washing a palladium-containing material deposited on the reactor to be used with a mixed acid of nitric acid and hydrochloric acid having a specific composition. CONSTITUTION:In preparing a carbonyl compound by bringing an olefin type unsaturated hydrocarbon, e.g., ethylene, etc. as a raw material into contact with oxygen in the presence of a uniform solution catalyst comprising a palladium compound, e.g., palladium chloride, and a compound of poly-valent metal, e.g., iron, copper, or managenese, palladium-containing deposit attached to the inner wall face of a reactor made of tianium in the production device is washed with a mixed acid consisting of >=1wt% nitric acid and 1-30wt%, preferably >=3wt% hydrochloric acid, so that deposited palladium is removed.