GB922021A - Recovery of palladium from catalysts - Google Patents

Abstract

Palladium is recovered from a deactivated catalyst by stripping the palladium from the support by slurrying with hydrochloric acid and passing chlorine gas in to form a palladium-containing solution, removing insoluble materials from the solution and precipitating palladium from the solution by the addition of a more electropositive metal, e.g. aluminium or magnesium. Prior to treatment the catalyst may be cleaned either by washing with an organic solvent, e.g. xylene followed by steam heating to remove the solvent or by heating in air, both steps being followed by washing with an alkaline reducing agent. The palladium recovered may be further purified by dissolving it in hydrochloric acid while passing chlorine gas in and filtering to removing insolubles. Ammonium hydroxide is then added to the filtrate and the mixture warmed to redissolve the palladium complex and give Pd(NH3)4 Cl2. Insolubles are again filtered off and the filtrate acidified with hydrochloric acid to give Pd(NH3)2 Cl2 as a precipitate. This precipitate is then either treated with hydrazine hydrate or heated in hydrogen to give pure palladium. The recovered or refined palladium may be dissolved in hydrochloric acid whilst passing gaseous chlorine through the mixture to give a solution of palladium chloride for the production of a catalyst by the methods described in Specifications 718,306, 746,385, 760,737 and 922,022. Specification 456,070 also is referred to.ALSO:Palladium is recovered from a deactivated catalyst by stripping the palladium from the support by slurrying with hydrochloric acid and passing chlorine gas in to form a palladium-containing solution, removing insoluble materials from the solution and precipitating palladium from the solution by the addition of a more electropositive metal, e.g. aluminium or magnesium. Prior to treatment the catalyst may be cleaned either by washing with an organic solvent, e.g. xylene, followed by steam heating to remove the solvent or by heating in air, both steps being followed by washing with an alkaline reducing agent. The palladium recovered may be further purified by dissolving it in hydrochloric acid while passing chlorine gas in and filtering to removing insolubles. Ammonium hydroxide is then added to the filtrate and the mixture warmed to redissolve the palladium complex and give Pd(NH3)4Cl2. Insolubles are again filtered off and the filtrate acidified with hydrochloric acid to give Pd(NH3)2Cl2 as a precipitate. This precipitate is then either treated with hydrazine hydrate or heated in hydrogen to give pure palladium. Specifications 456,070, 718,306, 746,385, 760,737 and 922,022 are referred to.