Which of the following is used as a catalyst in contact process?

$V_2O_5$

The correct answer is Option (2) → $V_2O_5$

The Contact Process is the industrial method used for the manufacture of sulphuric acid (H₂SO₄).

The key step in this process is the oxidation of sulphur dioxide (SO₂) to sulphur trioxide (SO₃).

2SO₂ + O₂ ⇌ 2SO₃

This reaction is slow under normal conditions, therefore a catalyst is required to increase the rate of reaction.

The catalyst used in the contact process is vanadium pentoxide (V₂O₅). It acts as an oxidation catalyst, facilitating the conversion of SO₂ to SO₃ efficiently at about 450°C and moderate pressure.

Earlier, platinum was used as a catalyst, but it was replaced by V₂O₅ because:

• It is cheaper
• It is less easily poisoned by impurities such as arsenic compounds
• It provides high catalytic efficiency

Therefore, vanadium pentoxide (V₂O₅) is used as the catalyst in the contact process.

Option-wise Explanation

Option 1 Finely divided iron

This is incorrect. Finely divided iron is used as a catalyst in the Haber Process, which is used for the industrial manufacture of ammonia (NH₃) from nitrogen and hydrogen.

Option 2 V₂O₅

This is correct. Vanadium pentoxide is the catalyst used in the contact process to oxidize sulphur dioxide (SO₂) into sulphur trioxide (SO₃).

Option 3 Cu₂Cl₂

This is incorrect. Cuprous chloride (Cu₂Cl₂) is used in the Deacon’s process, which is used for the manufacture of chlorine gas from hydrogen chloride (HCl).

Option 4 Ni in presence of H₂

This is incorrect. Nickel in presence of hydrogen is used as a catalyst in hydrogenation reactions, such as the conversion of vegetable oils into fats.