Question

Describe the manufacture of H₂SO₄ by contact process?

Answer 1

Sulphuric acid is manufactured by the contact process. It involves the following steps:
Step (i):
Sulphur or sulphide ores are burnt in air to form SO2.
Step (ii):
By a reaction with oxygen, SO₂ is converted into SO3 in the presence of V2O₅ as a catalyst.

Step (iii):
SO3 produced is absorbed on H₂SO₄ to give H₂S₂O₇ (oleum).

This oleum is then diluted to obtain H₂SO₄ of the desired concentration. In practice, the plant is operated at 2 bar (pressure) and 720 K (temperature). The sulphuric acid thus obtained is 96-98% pure.