What is the primary mechanism for NOx formation?

The primary mechanism for the formation of nitrogen oxides (NOx) is the oxidation of nitrogen in air, especially at high temperatures typical of combustion processes. During combustion, nitrogen, which is an abundant component of the air, combines with oxygen to form various nitrogen oxides. This process is particularly prevalent in high-temperature environments, such as those found in internal combustion engines and industrial burners.

As combustion occurs, the extreme heat facilitates the breaking of bonds within nitrogen molecules, allowing them to react with oxygen. This reaction produces nitric oxide (NO) and nitrogen dioxide (NO2), both of which are categorized as NOx. This understanding is crucial for mitigating NOx emissions, as it emphasizes the link between combustion temperatures and NOx formation, leading to the implementation of strategies aimed at controlling these emissions.

The other options do not accurately capture the primary mechanism behind NOx formation: exposure to low temperatures would not facilitate oxidation, while burning excess fuel typically leads to incomplete combustion and different emissions; increased pressure in the combustor may impact combustion efficiency but isn’t a direct cause of NOx formation.