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

Activated carbon fibres (ACFs) have been used for the selective catalytic r eduction (SCR) of NO with NH3 in the temperature range 100-400 degrees C. A model flue gas (700 ppm, NO, 800 ppm, NH3, 3 vol.% O-2 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 degrees C. The presence of water in the hu e gases dramatically diminishes the NO reduction activity at temperatures b elow 250 degrees C. On the other hand, the presence of O-2 shows a positive effect on conversion. NO reduction activity of ACFs can be enhanced by mea ns of different pre-treatments which introduce new superficial groups in th e fibres. Among all the treatments studied, the best results were obtained by oxidation of the fibres followed by reaction with NH3. The reaction 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. (C) 2000 Elsevier Science B.V. All right s reserved.