As can be inferred from the description of the surface chemistry of silica, one of the major adsorption applications of silica is the adsorption of polar molecules (see Chapter 6) [16].
On the other hand, many practical catalysts consist of one or several active components deposited on a high surface area support.
In heterogeneous catalysis, transition metal nanoparticles are supported on different substrates and utilized as catalysts for different reactions, such as hydrogenations and enantioselective synthesis of organic compounds [163], oxidations and epoxidations [164], and reduction and decomposition [151].
For example, a porous silica xerogel is a good support for Co in the Fischer–Tropsch catalysts for the diesel fuel conversion of syngas [165]. The surface decoration of partially agglomerated amor- phous silica nanospheres with SnOx nanocrystals of diameter 3–6nm to produce extremely small, tin oxide nanostructures on a silica nanosurface to produce improved catalysts was as well demonstrated [166]. Besides, in various organic syntheses, catalytic hydrogenation is carried out in a liquid phase using a metal, such as Pd, Pt, or Rh supported, in silica as the catalyst [167–170].