EFFECT OF PRESSURE ON NOX ADSORPTION BY ACTIVATED CARBONS

Exposing activated carbons to nitric oxide and oxygen at temperatures between 295 and 400 K leads to the conversion of the NO to NO2 at the carbon surface and the adsorption of NO2. In the current study, the co nversion and adsorption kinetics of the NO to NO2 reaction were examin ed at total pressures between 1 and 28 bar using a commercially availa ble activated carbon. Up to 144 mg of NO2/g of carbon was adsorbed at 28 bar and 343 K, of which 115 mg of NO2/g of carbon was reversibly ad sorbed-desorbed during repeated pressurization-depressurization cycles . The amount of NO2 adsorbed at 17 bar and 373 K was similar to the am ount adsorbed at 1 bar and 343 K, whereas it was 3-4 times greater tha n the amount adsorbed at 1 bar and 373 K. Analysis of the adsorption i sotherm suggested the mechanism of NO2 uptake was associated with micr opore filling with a monolayer of adsorbed NO2 formed at a total gas p ressure near 10 bar. Time profiles for the desorption of NO2, CO2, and O-2 during pressure release and temperature-induced desorption sugges ted the influence of critical temperatures and pressures of the adsorb ed gases and that van der Waals adsorption forces are important during adsorption and condensation within the pores of the carbon.