Homogeneous and Heterogeneous Catalysis
The phenomenon of catalysis can be divided into two main types – homogeneous and heterogeneous catalysis, on the bases of the number of phases present in the reaction mixture (A phase is a homogeneous part of a system).
When the catalyst is present in the same phase as the reactants, the phenomenon is called homogeneous catalysis. For example :
(i) Nitric oxide catalyses the oxidation of sulphur dioxide to sulphur trioxide in the lead chamber process.
(ii) Hydrogen ions catalyse the inversion of cane sugar
When the catalyst is present in a phase other than that of reactants the phenomenon is called heterogeneous catalysis. For example :
(i) Iron (s) catalyses the formation of NH3 gas.
(ii) In contact process for the manufacture of sulphuric acid, platinized asbestos is used as the catalyst