Reactions which depends on the pore size of the catalyst and shape and size of the reactant is called shape selective catalyst.
Shape-selective catalysis by zeolite
Zeolites are microporous crystalline solids with well-defined structures. Generally, they contain silicon, aluminium and oxygen in their framework and cations,
water and/or other molecules within their pores. zeolites are used in petrochemical cracking, ion-exchange (water softening and purification),
and in the separation and removal of gases and solvents. Other applications are in agriculture, animal husbandry and construction.