Give the principal involved in manufacture of sulphuric acid by contact process. How does concentrated h2so4 react with (1) c and (2) caf
Answers
Sulphuric acid is prepared by contact process all over the world. Preparation of sulphuric acid by contact process is based upon the catalytic oxidation of SO2 to SO3.Following steps are involved in the preparation of H2SO4-
1.Preparation of SO2.
2.Purification of SO2.
3.Oxidation of SO2.
4.Absorption of SO3.
5.Dilution of oleum
CONDITIONS NECESSARY FOR MAXIMUM YIELD OF SO3:
2SO2 + O2----------> 2SO3 + 45Kcal
Oxidation of SO2 is a reversible and exothermic process in which volume of product is less than the volumes of reactants. In order to obtain maximum amount of SO3, on applying Le-Chatelier’s Principle following conditions are necessary:
1. Concentration:- Excess of O2.
2.Temperature- A decrease in temperature favours reaction in forward direction. Optimum temperature for this process is 450 degC to 500 degC.
3.Pressure- Since volumes of reactants are greater than the product, therefore, according to Le-Chatelier’s Principle a high pressure is favourable.Optimum pressure is about 1.5 to 1.7 atmosphere.
4.Use of catalyst-At low temperature, rate of reaction decreases, so as to increase rate of reaction ,a catalyst vanadium pentaoxide (V2O5) is used.