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Hydrogenation Catalysts

Be careful! Fire hazard!

Palladium-Charcoal

Palladium-charcoal is self igniting in its reduced form! To oxidise it separate the catalyst from the reaction mixture and add hydrogen peroxide with stirring. The mixture will foam vigorously after a short induction period and will develop a lot of heat. (Use a high beaker and do not deactivate more than 10 g at the same time.)

Raney-Nickel Catalyst

Raney-Nickel catalyst is pyrophoric and thus has to be deactivated. Small quantities may be collected first covered with water. Do not deactivate more than 100 g at the same time.

To the catalyst 25 % hydrochloric acid is added in a beaker of sufficient size (2 l for 100 g of catalyst). On warming up the mixture the nickel will slowly dissolve. You may speed up the reaction very much by carefully adding 30 % hydrogen peroxide solution. Be very careful with the oxidising agent since the reaction will otherwise become too vigorous. Use the acid sparingly and add slowly more and more just to keep the reaction running and to avoid formation of gelatineous coagulum which may cover still reactive catalyst. For 100 g of the catalyst aproximately 400 ml of acid are required. The reaction is finished if there is no more black precipitation and a clear green solution is yielded.

Add a saturated hydrogencarbonate solution until there is no more foaming. Sodium carbonate is less suitable since the carbonate particles are enclosed by the gelatineous precipitation and will not react. The precipitation consists of basic nickel carbonate and is filtered off. Since the dust of nickel salts is carcinogenic put the still wet material in a separate bottle and clean all used equipment immediately.

The price for this deactivation is that the weight increases aproximately 8 times.

The filtrate may be flushed down the drain if it is clear and colorless. The mother liquor tends to form further precipitations and has then to be filtered another time. According to the local regulations (Indirekteinleiterverordnung des Landes Berlin) the concentration of nickel in the waste water must not exceed  0,2 mg/l.