Catalytic NO reduction with NH3 over carbons modified by acid oxidation and by metal impregnation and its kinetic studies

The catalytic effects of carbon in NO reduction with NH3 at low temperatures (<200°C) were examined using mineral matter free carbon derived from phenol–formaldehyde resin. The carbon was found to have little catalytic activity in the reaction, in contrary to other previous studies. The activity was considerably enhanced by oxidation with nitric acid and exceedingly enhanced upon impregnation with Cu and Fe. At a NO concentration of 640 ppm and a specific velocity of ca. 10 000 h−1, complete conversion of NO can nearly be achieved using the catalyst that has been impregnated with Cu. Kinetic studies on the reactions over the metal-impregnated carbons show that the apparent reaction orders with respect to NO and NH3 are ca. 0.65 and 0.1, respectively, and the apparent activation energies are 41 and 35 kJ mol−1 for carbons impregnated with Cu and Fe, respectively. The Mars–van Krevelen model gives a satisfactory simulation of the experimental data, which suggests that the NO reduction is governed by a redox mechanism in which the metal–carbon complexes serve as the catalytic centers for the transference of oxygen from NO and/or O2 to NH3.