Contact process

Contact Process an industrial process for the manufacture of sulfuric acid. Concentrated sulfuric acid, (approx. 18 moles/L), is produced in ton quantities in the following way:

1. Step 1: Sulfur is burnt in air to produce sulfur dioxide, SO₂. This reaction releases a large amount of heat which is used to generate steam and electricity.
2. Step 2: The sulfur dioxide is oxidized to sulfur trioxide, SO₂,on a vanadium pentoxide catalyst.
3. Step 3: The sulfur trioxide is dissolved in concentrated sulfuric aid to produce oleum (fuming sulfuric acid, H₂S₂O₇.
4. Step 4: The oleum is reduced in strength by adding water to produce twice as much sulfuric acid as used in the previous step.