How does the contact process use catalysis to manufacture sulfuric acid?

The contact process is the modern industrial method for manufacturing sulfuric acid. A critical stage in this process is the oxidation of sulfur dioxide to sulfur trioxide, which is an exothermic and reversible reaction.12

To increase the rate of this oxidation without decreasing the yield, a catalyst—typically vanadium pentoxide ($V_2{O}_5$)—is employed on an inert support. The process involves passing a mixture of sulfur dioxide and oxygen through a catalytic converter containing multiple catalyst beds.23

As the gas mixture passes over these beds, the catalyst facilitates the conversion of sulfur dioxide into sulfur trioxide. After the initial stages, the gas is cooled and the sulfur trioxide is absorbed into sulfuric acid. A final pass through the last reaction bed ensures a conversion rate of greater than 99 percent. This efficient use of catalysis is essential for the large-scale, cost-effective production of the acid.2