Could you please tell me the main reasons to why we actually do calcination and reduction after the synthesis of a catalyst by impregnation.
Thank you in advance for your answers.
For compounds like platinum oxide, the active catalyst is finely divided platinum metal and the oxide is reduced before use. The metal is highly reactive and highly flammable so that the oxide is made and the active, reduced metal is used in situ. Oxidized species are easier to store and prepare than the active catalyst and precatalysts are commonly used in many reactions.
In impregnation method the materiel can be taken as metal precursor it contains nitrates or chlorides with the drop wise addition of support with water metal precursors to form their hydroxides and these material calcined to form their constituent metal oxides (MO). The metal oxide can be reduced by using H2 gas or hydrogenating reagent such as Hydrazine to form reduced metal.
Neus Blanch Raga What about if you would like to increase the amount of active metal on the support with a second impregnation? at which stage the calcination needs to be done, after the first wet impregnation or at the end of the second impregnation?