SELECTIVE CATALYTIC REDUCTION OF NO WITH NH3 OVER ACTIVATED CARBONS .1. EFFECT OF ORIGIN AND ACTIVATION PROCEDURE ON ACTIVITY

The activity for the selective catalytic reduction of NO with NH3 (SCR) of a suite of different activated carbons has been studied in the temperature range 373-550 K. The effect of origin (bituminous coal, peat, plum stones, and olive pits), activation agent (steam, CO2), and degree of activation was investigated by activity measurements. In general, the SCR activity, which is relatively high at 373 K, decreases with increasing temperature, and for some carbons increases again above 450 K. Two types of SCR processes are operative. In the lower temperature range, the narrow microporosity affects the rate by increased adsorption of NO, resulting in higher local concentrations. In the higher temperature range, oxygen functional groups determine the SCR activity level. Precursors yielding narrow microporous carbons result in better activities below 450 K. Steam-activated carbons gave higher SCR activity above 450 K than CO2-activated carbons.