Catalytic Properties

Transition metals and their compounds exhibit good catalytic properties. They have proven to be good homogeneous and heterogeneous catalysts, partly because of their ability to participate in different oxidation-reduction steps of catalytic reactions. These steps involve changes in the oxidation states of these metal ions. Compounds of Fe, Co, Ni, Pd, Pt, Cr, etc. are used as catalysts in a number of reactions. Their compounds enhance the rate of the chemical reactions.

In homogeneous catalysis reactions, the metal ions participate by forming unstable intermediates. In heterogeneous catalysis reactions, on the other hand, the metal provides a surface for the reactants to react.

Examples :

1. $\mathrm{MnO_2}$ acts as a catalyst for decomposition of $\mathrm{KClO_3}$.
2. In manufacture of ammonia by Haber's process, Mo/Fe is used as a catalyst.
3. Co-Th alloy is used in Fischer Tropsch process in the synthesis of gasoline.
4. Finely divided Ni, formed by reduction of the heated oxide in hydrogen, is an extremely efficient catalyst in hydrogenation of ethene to ethane at 140 $\mathrm{^{0}C}$.

Commercially, hydrogenation with nickel as catalyst is used to convert inedible oils into solid fat for the production of margarine.

5. In the contact process of industrial production of sulfuric acid, sulphur dioxide and oxygen from the air react reversibly over a solid catalyst of platinised asbestos. …