Question

Write the various steps involved in manufacture of H₂SO₄ by contact process.

Answer 1

Contact process for manufacturing of sulphuric acid(H₂SO₄):

Steps involved in the manufacturing of sulphuric acid are as stated below:

1. Preparation of sulphur dioxide.
2. Conversion of sulphur dioxide into sulphur trioxide.
3. Conversion of sulphur trioxide formed into concentrated H₂SO₄.

Step 1: Preparation of sulphur dioxide:

SO₂ is prepared by burning sulphur in the presence of excess air so that the product combines with oxygen which is helpful for the next stage.

S(s) + O₂ (g) → SO₂(g)

Step 2: Preparation of sulphur trioxide:

Sulphur trioxide is formed when sulphur dioxide reacts with oxygen in a ratio of 1:1 at a temperature of 400 °C – 450°C and a pressure of 1-2 atm in the presence of V₂O₅ as a catalyst. This reaction is reversible in nature.

2SO₂(g) + O₂(g) ⇌ 2SO₃(g)

Step 3: Preparation of concentrated sulphuric acid:

The sulphur trioxide formed is first made to react with concentrated sulphuric acid. Sulphur trioxide cannot be dissolved in water directly as it leads to the formation of fog. The product obtained after this reaction is known as oleum. The oleum obtained is then dissolved in water to obtain concentrated sulphuric acid.

H₂SO₄ + SO₃(g) → H₂S₂O₇(l)

H₂S₂O₇(l) + H₂O(l) → 2H₂SO₄