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Producing Sulfuric Acid

Producing Sulfuric Acid: The Contact Process

Tetraoxosulphate (VI) acid, other known as sulphuric acid (\(\text{H}_{2}\text{SO}_{4}\)) is produced from sulfur, oxygen and water through the Contact process. In the first step, sulfur is burned to produce sulfur dioxide (\(\text{SO}_{2}\)):

\(\text{S}(\text{s}) + \text{O}_{2}(\text{g})\) \(\to\) \(\text{SO}_{2}(\text{g})\)

This is then oxidised to sulfur trioxide (\(\text{SO}_{3}\)) using oxygen in the presence of a vanadium(V) oxide catalyst:

\(2\text{SO}_{2}(\text{g}) + \text{O}_{2}(\text{g})\) \(\rightleftharpoons\) \(2\text{SO}_{3}(\text{g})\)

Finally the sulfur trioxide is treated with water to produce sulfuric acid with a purity of \(\text{98}\) – 99%:

\(\text{SO}_{3}(\text{g}) + \text{H}_{2}\text{O}(\text{l})\) \(\to\) \(\text{H}_{2}\text{SO}_{4}(\text{l})\)


Heavy chemicals are chemicals used extensively in industries and are. produced in very large quantities. Tetraoxosulphate (VI) acid is an example of a heavy chemical. Fine chemicals are chemicals produced in small quantities for specific purposes. and to a very high degree of purity. 

The contact process is the current method of producing sulfuric acid in the high concentrations needed for industrial processes. Platinum used to be the catalyst for this reaction; however, as it is susceptible to reacting with arsenic impurities in the sulfur feedstock, vanadium(V) oxide (V2O5) is now preferred. This process was patented in 1831 by British vinegar merchant Peregrine Phillips. In addition to being a far more economical process for producing concentrated sulfuric acid than the previous lead chamber process, the contact process also produces sulfur trioxide and oleum.

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