Reaction of NO with carbonaceous materials: 2. Effect of oxygen on the reaction of NO with ashless carbon black

The reaction rate in the reaction of NO with an ashless carbon black was considerably enhanced in the presence of oxygen. A similar effect has also been observed in the reaction of NO with the oxidized carbon black. The creation of more active sites on the carbon surface in the reaction with oxygen and NO 2 (produced by the reaction of NO with O 2) is proposed to be responsible for this enhancement. A lower apparent activation energy was observed in the reaction of NO with the oxidized carbon black than with the unmodified carbon black. It was found that the adsorption of NO is restrained to some extent on the carbon black surface mostly covered by carbon–oxygen (C(O)) complexes. However, the adsorption of NO and the formation of products at ca. 40°C were enhanced only when C(O) complexes of higher thermal stability were left on the surface. Hence, the more thermally stable C(O) complexes are assumed to play an important role in the enhancement of the reaction rate by activating the neighboring carbon atoms.