Low temperature selective catalytic reduction of NO over modified activated carbon fibres

Activated carbon fibres (ACFs) have been used for the selective catalytic reduction (SCR) of NO with NH3 in the temperature range 100–400°C. A model flue gas (700 ppmv NO, 800 ppmv NH3, 3 vol.% O2 and He to balance) was used in all experiments. Among all the ACFs studied, polyacrilonitrile (PAN)-based ACFs showed the highest NO reduction activity which is ascribed to the effect of nitrogen functionalities existing on the surface of this material. The curve of NO conversion versus temperature exhibits a minimum in the temperature range 150–200°C. The presence of water in the flue gases dramatically diminishes the NO reduction activity at temperatures below 250°C. On the other hand, the presence of O2 shows a positive effect on conversion. NO reduction activity of ACFs can be enhanced by means of different pre-treatments which introduce new superficial groups in the fibres. Among all the treatments studied, the best results were obtained by oxidation of the fibres followed by reaction with NH3. action rate seems to be first-order with respect to NO and zero-order with respect to NH3. A Langmuir-type dependence between NO conversion and oxygen concentration was observed.