Nitrogen Dioxide (NO2) : measurement and control

Emissions of nitrogen oxides (eg NO2) into our atmosphere have become a global problem. Everywhere, researchers and developers are working on better and more accurate simulation and measurement methods, as well as improving catalysts. This research is aimed at both fixed combustion processes (power plants, steel production, chemical-based materials ...) and mobile applications in the automotive sector with the aim of reducing NO2 by selective catalytic reduction (Selective Catalytic Reduction - SCR). Ammonia or ammonia-forming compounds (urea) are added to form pure nitrogen and water. NOx is the generic term used to describe the main nitrogen oxides present in air pollution. It includes various nitrogen oxides: nitrogen monoxide (NO) and nitrogen dioxide (NO2). Here, we are mainly interested in the radicals of NO2 and its dimer nitrogen peroxide N2O4. Nitrogen dioxide NO2 is toxic and its emissions into our environment should be kept as low as possible. However, NO2 is a byproduct of many combustion processes, so that industrial technical developers as well as developers of preventive medicine and labor are confronted with this substance. However, this equilibrium also raises the problem of measuring and controlling gas flows that contain NO2 in higher concentrations. This is particularly the case when pure NO2 is used, which is in equilibrium with its dimeric form N2O4, itself dependent on the temperature and the pressure and, moreover, sensitive to the conditions of light and surface area (at 27 ° C only 20% NO2, for 80% N2O4 dimer). The mixture is very sensitive to moisture and, in the presence of moisture, it is likely to react in nitric acid (HNO3) and nitrous acid (HNO2), which are extremely corrosive.

NO2 gas mixtures

For research on combustion processes producing NO2 emissions or for testing / developing new catalysts, it is necessary to be able to accurately calculate the flow rate of gaseous mixtures containing NO2. This applies not only to catalysis but also to the effects of NO2 on the organism and the environment, since NO2, by its reactivity, is extremely toxic.