In the contact process, concentrated sulphuric acid instead of water is used to absorb the sulphur trioxide gas produced.One of the reasons suggested online is that the reaction between sulphur trioxide and water is highly exothermic.
But I have these concerns:
- Both the reaction between sulphur trioxide with concentrated sulphuric acid and that between oleum and water are exothermic
- If the reaction is too exothermic, a coolant can be applied in the industrial process
So, I propose two possible reasons.
- The two previously mentioned are less exothermic
- More concentrated sulphuric acid can be produced by the reaction between concentrated sulphuric acid and sulphur trioxide, hence the process can become more economical
What should be the best explanation for why water is not used to absorb sulphur trioxide?