- Solid sulfur, S(s), is burned in air to form sulfur dioxide gas.
- The gases are mixed with more air then cleaned by electrostatic precipitation to remove any particulate matter.
- The mixture of sulfur dioxide and air is heated to 450 degree Celcius and subjected to a pressure of 101.3 - 202.6 kPa (1 -2 atmospheres) in the presence of a vanadium catalyst (vanadium (V) oxide) to produce sulfur trioxide, with a yield of 98%.
- Any unreacted gases from the above reaction are recycled back into the above reaction.
- Sulfur trioxide is dissolved in 98% (18M) sulfuric acid to produce disulfuric acid or pyrosulfuric acid, also known as fuming sulfuric acid or oleum.
- Water is then added to the oleum to produce 98% of sulphuric acid.
Click below video for further explanation of Contact Process.