Nitrogen-containing carbons from phenol-formaldehyde resins and their catalytic activity in NO reduction with NH3

Porous carbons with controlled nitrogen contents were prepared from phenol-formaldehyde resins impregnated with different amounts of m-phenylenediamine. The chemical compositions of the resin precursors and the resulting carbons were characterized. Comparison of results from X-ray photoelectron spectroscopic and elemental analysis showed that the nitrogen functional groups in the carbons are more numerous in the internal part and are mainly of the pyridine type. The catalytic activity of the carbons in NO reduction with NH3 increased upon nitrogen impregnation. The activity showed a clear correlation with the nitrogen content obtained using X-ray photoelectron spectroscopy, indicating that the reaction mainly occurred at the external part of the carbon particles. Under a low temperature regime (< 140 degreesC), the reaction was dominated by the equilibrium adsorption of the reactants, which rendered a negative apparent activation energy, while chemical interactions on the surface controlled the reaction at higher temperatures. The effects of the impregnated nitrogen atoms were suggested, due to the introduction of extra electron to the aromatic rings in carbon, to promote the adsorption of NO, as well as to activate the adsorbed species. (C) 2002 Elsevier Science Ltd. All rights reserved.