Carbon fibres have been used for the low temperature selective catalytic re
duction of NO with NH3 at temperatures in the range 100-400 degrees C. The
carbon fibres were obtained by pyrolysis of polyarylamide fibres (Nomex(R)
and Kevlar(R)) at temperatures of 700 degrees C and 850 degrees C. NO reduc
tion degrees in the range 40-80% were achieved with the carbonised fibres.
No significant improvement in NO reduction was found by activating the carb
onised fibres. The Nomex-based carbon fibres show higher NO reduction degre
es than Kevlar-based ones. The presence of oxygen enhances NO conversion, p
robably due to oxidation of NO to NO2. The change in concentration of NO an
d NH3 (at NK3/NO > 1) hardly affects NO conversion. A minimum in the variat
ion of NO conversion with temperature was observed for both types of sample
s, being more marked for the Kevlar-based carbon fibres. At temperatures be
low 250 degrees C, the presence of water exerts a significant inhibitory ef
fect upon NO reduction. Low-density carbon fibre-based monoliths prepared b
y agglomeration of carbonised Nomex fibres were used for NO reduction and a
similar performance to that of the carbonised fibres was found. (C) 1999 E
lsevier Science B.V. All rights reserved.