Why are heterogeneous catalysts calcined?

Most of the literature I read says to calcine heterogeneous catalysts when preparing them. When synthesizing heterogeneous catalysts, what is the reason for calcining them? 




For **heterogeneous catalysis** calcining of the catalyst allows for the following:


* mechanically and thermodynamically stable macrostructure (matrix) with defined geometry, surface and pore size;
* predictable activity based on calcining regime (generally, there is a temperature peak for maximum activity, and further extreme temperature treatment often lowers catalyst's activity);
* pure composition without traces of organics and majority of other undesired impurities;
* production convenience and scalability (for example, metal oxide catalyst manufacturing process can be easily implemented within mining and processing plants);
* when distributed over support, more uniform distribution of metal oxide is achieved, and upon slow treatment crystallinity of the catalyst can also be tweaked.


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One of the most important reasons to calcine a catalyst preparation is to decompose the impregnated metal salts. This includes decomposition of nitrates, chlorides, carbonates and organic chelates, leaving a metal or metal oxide on the support surface.


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