Heterogeneous reactions of NO2 and NO-O2 on the surface of carbons

The interactions of nitrogen oxides with carbons differing in the chemical structure of surface functional groups were studied using in situ FTIR combined with the measurements of catalytic activity. Microporous carbon samples with similar pore size distribution were prepared from cellulose. The structure and coverage of adsorbates during reactions at temperatures between 295 and 573 K are determined by FTIR. No significant changes in NOx reaction with carbon surface were found by oxidation of the carbonized film. During the study of the reaction of NO/O-2 mixture with carbons, the infrared absorption bands for the surface species formed are similar to the IR bands observed after the reaction of carbon samples with NO2. For both reactions, surface species, including C-NO2, C-ONO, C-NCO and anhydride structures are formed. Catalytic NOx reduction by carbons has been investigated in the temperature range 295-623 K in the flow reactor equipped with an FTIR gas analyzer. As the surface of carbon is exposed to NO2 gaseous NO is formed. The reduction of NO2 to N-2 without the use of an externally supplied reductant can be achieved with microporous carbons. Significant NO2 conversion to N-2 occurred at 623 K on both oxidized and non-oxidized carbons. (C) 2002 Elsevier Science Ltd. All rights reserved.