Ammoniakoxidation

Ammoniakoxidation, also known as ammonia oxidation, is a catalytic chemical reaction in which ammonia (NH₃) is converted to nitrogen oxides, primarily nitric oxide (NO). The process forms the core of the industrial Ostwald process for the production of nitric acid, a key component in fertilizers, explosives, and various chemical syntheses.

The reaction is typically carried out in a fixed‑bed reactor using a platinum‑rhodium alloy catalyst at temperatures between 800 °C and 950 °C and atmospheric pressure. The overall stoichiometry can be expressed as 4 NH₃ + 5 O₂ → 4 NO + 6 H₂O. Subsequent oxidation of NO to nitrogen dioxide (NO₂) and absorption in water yields nitric acid (HNO₃). Reaction selectivity and catalyst lifetime are strongly influenced by the presence of impurities, especially sulfur compounds, which can poison the catalyst surface.

Developed in the early 20th century by Wilhelm Ostwald, the process has been refined to improve energy efficiency and reduce emissions. Modern plants often incorporate heat recovery systems and staged combustion to lower the overall energy demand. Environmental considerations focus on minimizing NOx release, as nitrogen oxides contribute to atmospheric pollution and ozone formation. Catalytic after‑treatment and selective catalytic reduction (SCR) are employed to meet stringent emission standards.

Ammoniakoxidation remains a cornerstone of the chemical industry, providing a reliable route from inexpensive ammonia to high‑value nitric acid while driving ongoing research into more robust catalysts and greener process designs.