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 wthin 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.