Question

What are zeolites? Give one example.

Answer 1

Hint: Zeolites are the crystalline solid structures made up of silicon, aluminum, and oxygen and form a network of cavities and channels inside which cations, water molecules, and/or small molecules. In other words, they are microporous aluminosilicate minerals and are commercially used as adsorbents and catalysts.

Complete step by step answer:
Zeolites are hydrated three-dimensional aluminosilicates containing a network of channels within their structure.
They are sometimes also known as ‘molecular sieves’
Because of their specific pore size, they permit only smaller or similar size molecules to pass, bigger ones are left out.
Currently, there are 232 identified zeolites. Out of these, 40 are natural and others are synthesized.
Synthetic zeolites are more popular on the commercial level because of two reasons: first is that natural ones have impurities like Ferric ions and sulfate ions, etc. Secondly, the synthetic ones can be customized to have uniform pore size while the natural ones have some non-uniformity in channels.
ZSM-5 is the most popular synthetic zeolite. It is made up of pentasil units.
In Greek, zeolite means “boiling stone”. This name was given because it gives steam when heated (this is because of the presence of water molecules in the channels).
Zeolites have to be activated before they can be used and it is done by heating it to drive off the adsorbed moisture and other gases.


Note:
There are various uses of zeolites:
Zeolites can be used to remove the hardness of the water. When the hard water sample is made to pass through zeolite channels the calcium and magnesium ions get replaced by sodium ions.
They can be used as a catalyst. For example, it catalyses isomerization of meta-xylene to para-xylene.
Zeolites are also used as catalyst support. For example, during the formation of gasoline.