Chemistry Form Four: Chapter 9 - Contact Process

A brief summary of the Contact Process:

• 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.

Attention:  If the sulphur trioxide is added directly to water an acid mist forms which is difficult to contain because the reaction to form sulphuric acid solution is very exothermic!

Click below video for further explanation of Contact Process.