Catalyst color issue
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I would like to ask everyone: which metals have relatively high contents in catalysts of different colors? For example, do green, black, and yellow represent higher contents of those respective metals? Additionally, what are the methods for depositing metal during catalyst preparation?
Catalysts made from Au, Mn, Cu, Fe, etc. have been used; since the content of such metals in the catalysts is generally not very high, their color does not usually reflect the color corresponding to the metal’s oxidation state. I think iron catalysts are dark brown in color, copper is slightly gray-green, and things like palladium on carbon are black; I can’t remember exactly after such a long time. Methods: Impregnation and precipitation are commonly used; other methods such as ion exchange and thermal melting have not been tried.
Red usually indicates iron poisoning. Black is basically carbon that hasn’t burned completely. You can search for relevant forum posts; there’s a lot of information available there!
It depends on the type of catalyst; if it is a hydrogenation catalyst, different metal types and contents will result in different colors.
Our workshop recently had a pink catalyst; I don’t know what happened