Contact Process

The contact process is the principal industrial method for manufacturing sulfuric acid at the high concentrations industry requires, passing sulfur dioxide and oxygen over a catalyst, now generally vanadium oxide, to form sulfur trioxide. The British vinegar merchant Peregrine Phillips patented the process in 1831, making it considerably cheaper than the existing lead chamber method, and the American chemist John Brown Francis Herreshoff developed an improved catalytic version of it for his company in 1890, while the German chemist Eugen de Haen patented a related process using sulfur dioxide, oxygen and vanadium oxide catalysts in 1901. Chemists at the German company BASF found in 1914 that reducing the catalyst's particle size below five thousand microns sharply improved its efficiency, an advance that helped make the vanadium-catalyzed contact process the industry standard it remains today.