Why does a palladium nitrate solution form precipitates after being stored for a long time?
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Hydrogenation catalysts often use metal palladium as the active component; generally, palladium nitrate is used, and what is available on the market is usually a solution of palladium nitrate. However, over time, precipitation occurs in such solutions. Does anyone know why this happens? Please advise. We suspect it might be palladium hydroxide, but it does not dissolve when nitric acid is added – what exactly is going on?
When preparing the palladium nitrate solution, sufficient nitric acid should be added to maintain a strong acidic environment in order to ensure stability. If nitric acid is not added to maintain a strong acidic environment, palladium nitrate will gradually decompose into basic palladium nitrate; in some cases, palladium hydroxide may even form. Palladium hydroxide loses water to become palladium oxide, which is very difficult to dissolve – it does not dissolve in water nor in nitric acid, but it can dissolve in hydrochloric acid.
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