Question

Reactions in zeolites catalyst depend on:
A. pores
B. apertures
C. size of cavity
D. all of the above

Answer 1

A catalyst is a chemical substance which increases the rate of the reaction without being consumed in the reaction. Actually it lowers the energy of activation required for preceding the chemical change in forward direction.

Complete step by step answer: Zeolites are microporous family of aluminosilicates consisting of $Al$, $Si$, $O$ ($Al{O_4}^{5 - }$ and $Si{O_4}^{4 - }$) and metals like $Ti$, $Sn$, and $Zn$. The formula of the minerals found in nature is $N{a_2}A{l_2}S{i_3}{O_{10}}.2{H_2}O$. Zeolites have the tendency to accommodate various types of cations like $N{a^ + }$, ${K^ + }$, $C{a^{2 + }}$, $M{g^{2 + }}$.
The preparation of zeolites includes a two step process. At first the sodium aluminate, sodium hydroxide and deionised water are mixed and allowed to stir at room temperature until the solution becomes homogeneous. Then after the aqueous colloidal silica was added to the reaction mixture and was agitated to yield the sodium aluminate catalyst.
Zeolites are used in the pharmaceutical and petrochemical industry due to successful generation of compounds using cracking and isomerisation processes. The factors responsible for the properties of the zeolites catalyst are:
Pores: The porosity of zeolites make them useful in a variety of synthetic reactions. The catalyst is often known as a shape selective catalyst. They exist as linear branched and ring structures.
Apertures: The aperture of zeolites includes three-dimensional frameworks of $Si{O_4}^{4 - }$​ and $Al{O_4}^{5 - }$​ tetrahedra which are linked through oxygen bridges. They form a closed packed crystal lattice structure as here eight tetrahedrally coordinated silicon or aluminium atoms and eight oxygen atoms are present. Thus the aperture of the catalyst becomes more stable due to such coordination.
Size of cavity: The size of the cavity is essential to accommodate various types of cations with variable sizes. Zeolites are classified by their structural units which compose frameworks like rings or polyhedra. The cavities have diameters in the range about $2$ to $8$ angstroms, which allows easy movement of ions between the cavities.
Thus the correct option is D, i.e. reactions in zeolites catalyst depend on all the above.

Note: Zeolites were used as ion-exchange agents, catalysts, and molecular filters in a range of industrial processes and home based appliances. The viruses are removed from ground water using zeolites based filtration method.