REDUCTION OF NO WITH NH3 IN WET AIR AT ROOM-TEMPERATURE OVER ACTIVE-CARBON FIBERS FURTHER ACTIVATED WITH SULFURIC-ACID

Reduction of NO with NH3 was studied at ambient temperature over active carbon fibers (ACFs) further activated with sulfuric acid. among ACFs, pitch based one (OG-5 A) further activated at 400-degrees-C for 4 h showed the highest activity in a temperature range of 25-200-degrees-C. It is of value to point that this particular ACF maintained the activity for reduction of NO at 25-degrees-C in air of 100% humidity. Other ACFs lost their activities almost completely under the above condition. Such prohibiting effects of humidity were reduced at higher reaction temperatures. The active sites for NH3 and NO are briefly discussed based on the TPD analyses of oxygen containing groups on the ACF surface. The retardation by humidity is related to the hydrophobic nature of the ACF surface. Such a property may be governed by the size of carbon hexagonal plane as well as kinds and numbers of surface oxygen groups. Thus, the highest activity of pitch based ACF further activated at 400-degrees-C is qualitatively explained based on the adsorption amount of NH3, activation ability for NO, and the hydrophobic nature.