(a) What are the components of the reaction mixture following the water-gas shift reaction?

(b) Explain how zeolites (Gallery,) are used to purify the${\mathbf{\text{H}}}_{\mathbf{\text{2}}}$formed

Carbon monoxide and water vapour react to generate carbon dioxide and hydrogen in the water-gas shift reaction:

${\mathbf{\text{CO +H}}}_{\mathbf{\text{2}}}\mathbf{\text{O}}\mathbf{\rightleftharpoons }{\mathbf{\text{CO}}}_{\mathbf{\text{2}}}\mathbf{\text{+ H}}$

Zeolites are crystalline solids comprised of silicon, aluminium, and oxygen that have cavities and channels inside where cations, water, and/or tiny molecules can live. They're also known as molecular sieves.

a) The water-gas shift reaction is a reaction that produces when the product mixture of water and carbon monoxide is heated to${400}^0\mathrm{C}$ over an iron or cobalt oxide catalyst.

${\text{H}}_{\text{2}}\text{O(g) + CO(g)}\rightleftharpoons {\text{CO}}_{\text{2}}{\text{(g) +H}}_{\text{2}}\text{(g)}$

This reaction is exothermic and therefore can be recycled.

The mixture is passed through liquid water, where${\text{CO}}_{\text{2}}$ is dissolved, or through $\text{CaO}$, generating ${\text{CaCO}}_{\text{3}}$, to purify the${\text{H}}_{\text{2}}$ gas.

b) Zeolites are utilised to purify the${\text{98\%H}}_{\text{2}}$ gas further. Zeolites are synthetic aluminosilicates made up of small polyhedrons with voids of varying size cavities.

The smaller molecules of${\text{H}}_{\text{2}}$ flow through, but the larger molecules are held in the zeolite cavities. A high purity$\text{99.9\%}$ hydrogen gas can be obtained in this manner.