handbook of carbon, graphite, diamond and fullerenes

242 Carbon, Graphite, Diamond, and Fullerenes
4.3 Catalyst Support
Catalysts are used on a very large scale in many industrial processes
and are an essential part of modern chemical industry. They are characterized
by their activity, selectivity, and recycling capability.
A common group of catalysts are the platinum-group metals which
have become essential factors in many industrial processes such as gasphase
oxidation, selective hydrogenation of petrochemical and pharmaceutical
feedstocks, fuel cells for power generation, and many others. Other
common catalysts are iron, nickel, and some transition metals.
These catalysts are in the form of a thin film deposited on a support.
The main function of the support is to extend the surface area. However,
the support can also alter the rate and the course of the reaction to some
degree. The support must be stable at the use temperature and must not
react with the solvents, reactants, or by-products.
The two major support materials are activated carbons (commonly
called activated charcoal) and activated alumina. Activated carbons
impregnated with palladium, platinum, or other metal salts are common in
most liquid-phase reactions.
Activated alumina has a lower surface area (75 vs. 350 m 2 /g) and is
less adsorptive than charcoal. It is also noncombustible (as opposed to
charcoal), which is an advantage in regeneration and the burning of
carbonaceous residue.