Question

What is the role of adsorption in heterogenous catalysis?

Answer 1

The role of heterogeneous catalysts can be explained in terms of adsorption of reactants on the surface of the catalyst.

The adsorption helps the reaction in the following ways:

(i) Adsorption increases the concentration of reactants on the surface of the catalyst. Due to increased concentration of the reactants, the reactions proceed rapidly.

(ii) Adsorbed molecules get dissociated to form active species like free radicals which react faster than molecules.

(iii) The adsorbed molecules are not free to move about and, therefore, they collide with other molecules on the surface.

(iv) The heat of adsorption evolved acts as energy of activation for the reaction (chemisorption).

Example: Adsorption of molecules of the reactant at the active site.

Occurrence of chemical reaction on the surface of catalyst

Desorption of product molecules
Example: