Choice Of Carrier For PGM Catalysts

The main function of carrier is to extend the surface area of the metal. When supported on high surface area carrier such as activated carbon the catalytic metal is present in the form of discrete crystallites and this will give very high catalyst surface area per unit weight of metal. The support should be stable at the temperature used and should not react with the solvents and reaction products.

Carrier characteristics are the functions of particle size, shape, pore volume, pore size distribution, surface area, activation procedure and material base.

Activated carbon is mainly used as a support for catalyst in liquid phase reaction. Carbon supported catalysts are prepared in two physical forms dry or paste. Repetition catalyst generally contains 50-55% by weight of water which is held in pore structure of carbon. Generally the surface area of different carbons can range from 700 m2/gm to over 1500 m2/gm.
This carrier have a lower surface area than activated carbon usually in range of 5 m2/gm to 30 m2/gm. It is used for selective hydrogenation or low porosity support to minimize adsorption of high value products.
This is used instead of carbon when excessive loss of expensive reactants by adsorption must be prevented.When more than one reation is possible Alumina supported PGM Catalyst may prove to be more selective than the same metal supported on carbon. It have surface area within range of 100 m2/gm to 400 m2/gm.
It is particularly suitable as a support for Palladium when selective deactivation catalyst will be needed. It is required when a support of low adsorption or of a basic nature is required.
It is another low surface area catalyst support. This is a dense material and requires powerful agitation of the reaction system to ensure uniform dispersal of catalyst. Traditionally Palladium on Barium sulfate is used in ROSENMUND REACTION.
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