Question

Describe the manufacture of H 2 SO 4 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.

Answer 2

The contact process is the current method of producing sulfuric acid in the high concentrations needed for industrial processes. Platinum used to be the catalyst for this reaction; however, as it is susceptible to reacting with arsenic impurities in the sulphur feedstock, vanadium(V) oxide (V2O5) is now preferred.