ABSTRACT
The oxidation of sulphur dioxide is thermodynamically controlled, and there are some gross similarities with ammonia synthesis, in that both are exothermic and do not rely on catalyst selectivity. Oxidation of sulphur dioxide for sulphuric acid manufacture is the earliest example of a catalytic process being worked on an industrial scale, and sulphuric acid is produced on a larger scale than any other chemical. Silver catalyst in various forms has been used commercially for several decades, and the limitation of both conversion and selectivity are largely imposed by process operating conditions rather than inherent catalytic properties. The oxidation of sulphur dioxide was probably the first catalytic process operated on a full commercial scale. Initially ammonia oxidation on a commercial scale was linked with coal coking, which gave rise to by-product ammonia liquor in reasonable quantities. The first ammonia oxidation nitric acid plant operating on by-product ammonia and using platinum sponge catalyst opened in 1908 at Gerthe, Westphalia.
