Net Zero Commitment
NITROGEN OXIDES AND NITROUS OXIDE: Environmental Impact and Mitigation Strategies in the Nitric Acid Industry
The nitrogen oxides (NO and NO2) which make up NOx have long been known as precursors of acid rain and smog. While ever more stringent emission limits apply in many countries there are still quite a large number industrial plants which have no abatement equipment installed.
Nitrous oxide (N2O) is a powerful greenhouse gas with significant global warming potential (GWP) on a 100-year time horizon. As per different sources NO2 GWP correlates from 273 (Intergovernmental Panel on Climate Change, Sixth Assessment Report [1]) to 310 as per EU’s emissions trading system (ETS) and regulations on its third commitment period [2].
In any event, it can be concluded that the GWP of N₂O is significantly higher than that of CO₂, meaning that nitrous oxide is a very potent GHG.
In the Ostwald process for manufacturing nitric acid, ammonia (NH3) undergoes a reaction with air in the presence of a catalyst made from precious metals, typically an alloy of platinum and rhodium (Pt-Rh), which is configured as a gauze pack within the ammonia oxidation reactor of nitric acid facilities. Nitrous oxide (N2O) is formed as an unwanted by-product in the oxidation of ammonia over the platinum-rhodium gauzes in the ammonia burner. The following reactions take place: