The role of different nitrogen functional groups on the removal of SO2 from flue gases by N-doped activated carbon powders and fibres

SO2 removal from flue gases by carbonaceous materials is determined by their behaviour as catalysts for SO2 oxidation into SO3 or H2SO4 in the presence of O-2 or O-2 and steam, respectively. Previous studies have demonstrated that nitrogen (N) functional groups are active sites for the adsorption and oxidation of SO2, although the nature of the N groups with the higher activity had not been established yet. For this reason, in the present work a number of activated carbons (AC) and activated carbon fibres (ACF) doped with N atoms have been prepared using different methods. The number and nature of these N groups have been assessed by XPS. The materials prepared have a wide range of nitrogen content, which is distributed into different chemical species. In this way, we were able to determine the effect of the N content and the role of the different N-containing functional groups on the catalytic activity for SO2 oxidation. The results confirm that, although the pore volume and the pore size distribution strongly influence the catalytic activity, the presence of N species at the surface increases the catalytic activity. They also demonstrate that, among the different N functional groups, pyridinic nitrogen is the most active for this reaction. (C) 2003 Elsevier Ltd. All rights reserved.