The Influence of Activated Carbon Type on NOx Adsorptive Capacity

Abstract

The selective capture of NOx from combustion flue gas by the use of commercially produced activated carbons at typical stack temperatures is reported. This adsorption is independent of whether the NOx is NO, NO2 or a mixture. The NOx adsorption capacities can be as great as 0.15 g NOx/g carbon if O2 is present as a co-reactant. NO2 is the species stored within the carbon and can be released by temperature induced desorption at 140°C. Adsorption capacities are dependent on the type of activated carbon used. Thermogravimetry/mass spectrometry was used to determine adsorptive capacity of several commercially available activated carbons produced from coal, coconut, and petroleum pitch precursors. The range of their N2 BET surface areas was between 400 to 2000 m2/g. Although, carbons with high adsorption capacity contained similar C, N, and O contents, proximate analyses, surface areas and micropore volumes, no significant correlations were found between chemical and physical properties and the NOx adsorptive capacity. One possibly important characteristic of the carbons correlated with NOx adsorption capacity was specific and narrow pore size distribution with an effective pore diameter of 0.56 nm.