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

Abstract In a fixed bed reactor, the rate of carbon black oxidation by NO 2 is significant for temperatures above 300°C, leading to NO, CO and CO 2 formation. The presence of O 2 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–NO 2 reaction. A kinetic mechanism in which intermediate nitro-oxygenated species are formed in the presence of NO 2 during an initial step is in agreement with all these observations. Oxygen and NO 2 are able to react with these species at 300°C. A parametric study of the effects of the temperature, NO 2 , O 2 and H 2 O concentrations was performed. With a one-dimensional model of NO 2 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.