The role of different nitrogen functional groups on the removal of SO 2 from flue gases by N-doped activated carbon powders and fibres

Abstract

SO 2 removal from flue gases by carbonaceous materials is determined by their behaviour as catalysts for SO 2 oxidation into SO 3 or H 2SO 4 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 SO 2, 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 SO 2 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.