Kinetics of the oxidation of carbon black by NO2: Influence of the presence of water and oxygen Original Research Article

In a fixed bed reactor, the rate of carbon black oxidation by NO2 is significant for temperatures above 300°C, leading to NO, CO and CO2 formation. The presence of O2 in the feed gas increases the rate of oxidation, as well as the presence of water. A cumulative effect is observed when both water and oxygen are present. An oxygen balance shows that oxygen atoms of water molecules are not consumed. Water acts as a catalyst for the C–NO2 reaction. A kinetic mechanism in which intermediate nitro-oxygenated species are formed in the presence of NO2 during an initial step is in agreement with all these observations. Oxygen and NO2 are able to react with these species at 300°C. A parametric study of the effects of the temperature, NO2, O2 and H2O concentrations was performed. With a one-dimensional model of NO2 consumption along the thickness of the carbon black bed, kinetic constants were derived and a phenomenological law was proposed, accounting for the effect of the presence of oxygen and water.