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

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