Important Features of Solid Catalysts
Activity The activity of a catalyst depends upon the strength of chemisorption to a large extent. The adsorption should be reasonably strong but not so strong that they become immobile and no space is available for other reactants to get adsorbed.
Selectivity The selectivity of a catalyst is its ability to direct a reaction to yield a particular product, e. g., starting with Hz and CO using different catalysts, we get different products.
Shape – selective catalysis The catalytic reaction that depends upon the pore structure of the catalyst and the size of the reactant and product molecules is called shape-selective catalysis.
Cracking Isomerization of hydrocarbons in the presence of zeolites is an example of shape-selective catalysis.
An important zeolite catalyst used in the petroleum industry is ZSM-S. lt converts alcohols directly into gasoline.
Enzyme Catalysis
Enzymes are complex nitrogenous organic compounds which are produced by living plants and animals. They are actually protein molecules of high molecular mass and form colloidal solutions in water.
They are also known as biochemical catalysis.