Preparation of Sulphuric Acid (H2SO4)

Production of Sulphuric Acid (H₂SO₄)


Sulphuric acid is an important chemical used in industry. It is also known as 'King of chemicals'. Sulfuric acid is manufactured by contact process. Contact process Involves the following steps.



Preparation of Sulphurdioxide (SO₂)

SO₂ is prepared by burning sulphur or sulphide ore in excess of air. It is done in a sulphur burner.

S + O₂  ----------->  So₂

So₂ produced is purified by passing it through

1. Dust precipitator (which removes dust from gas)

2. Water scrubber (which removes soluble impurities)

3. Drying tower (which removes moisture)

4. Arsenic purifier (which removes arsenic impurities)


Oxidation of SO₂ to SO₃

Purified SO₂ gas coming out from arsenic purifier is preheated and admitted to catalytic converter filled with catalyst V₂O₅. In catalytic chamber the following reversible reaction take place and is known as Contact process.

2SO₂ + O₂  <========>  2SO₃  

According to Le-chatelier's principle, to obtain maximum yield of SO₃, low temperature, high pressure and excess of oxygen are required. The optimum condition for the above reaction are
1. a temperature of 720 K
2. a pressure of 2 atm
3. high concentration of reactant
4. Vanadium Pentoxide (V₂O₅) as catalyst


Conversion of SO₃ into Sulfuric acid H₂SO₄


The SO₃ from catalytic converter is absorbed in about 98% H₂SO₄ resulting in oleum (H₂S₂O₇).

SO₃ + H₂SO₄  ----------->  H₂S₂O₇


SO₃ is not directly absorbed in water because it results in mist formation and further absorption become difficult. Oleum is then diluted with water to get Sulphuric acid (H₂SO₄) of desired concentration.

H₂S₂O₇  +  H₂O  ------------>  2H₂SO₄