Contact process

The contact process is an industrial method for producing sulfuric acid by catalytically oxidizing sulfur dioxide to sulfur trioxide, then absorbing the product in concentrated sulfuric acid.

Sulfur dioxide oxidation: The reaction of sulfur dioxide with oxygen to form sulfur trioxide. This reversible, exothermic reaction is the process’s central conversion step.
Sulfur dioxide: A colorless, pungent gas produced by burning sulfur or roasting sulfide ores. It is the sulfur-bearing feed that the process converts into sulfur trioxide.
Fertilizer: A material added to soil or plants to supply essential nutrients. Sulfuric acid made by this process is used to produce phosphate fertilizers.
Peregrine Phillips: A British vinegar manufacturer who patented a catalytic sulfuric acid process in 1831. His patent established the process’s catalytic oxidation principle.
Vanadium(V) oxide: An inorganic compound used as a catalyst in industrial sulfur dioxide oxidation. It catalyzes the key oxidation while tolerating operating conditions better than platinum.
Sulfur trioxide: A reactive oxide of sulfur with the formula SO₃. It is the immediate product of oxidation and the precursor absorbed to make acid.
Phosphate fertilizer: A fertilizer supplying phosphorus, commonly manufactured by acidulating phosphate rock. Sulfuric acid reacts with phosphate rock in a major downstream use.
Platinum catalyst: Platinum used to accelerate sulfur dioxide oxidation in early contact-process plants. Early plants used platinum before vanadium catalysts became the practical standard.
Le Chatelier's principle: A rule predicting how an equilibrium shifts when conditions such as pressure or temperature change. It explains why temperature and pressure choices balance conversion, rate, and cost.
Chemical equilibrium: A state in which forward and reverse reactions occur at equal rates. Sulfur trioxide formation is reversible, limiting conversion in a single pass.

Linked from 12 pages