Effect Of Nitrogen Doping On Reduction Of NO With Metal/Activated Carbon

The ever-growing energy demands due to raising global population and continuing lifestyle improvements have placed indispensable emphasis on fossil fuels. Combustion of fossil fuels leads to the emission of harmful gaseous pollutants.NO_x can result in primary pollutant,besides,it can also result in some secondary pollution. It can react with other materials in the atmosphere in certain condition,producing some secondary pollutants such as NO₃^-,O₃ and cellular particles,which lead to the problems of smog formation,ground level ozone,acid rain and eutrophication of the water body.The hazards of secondary pollution are more harmful than that of primary pollution,and it can make great hazards to health and entironment,so it has been regarded as the main object in the treatment of air pollution.The pollution of NO_x from industrial sources is serious,and these sources usually locate in some cities and industrial areas,The discharge port of industrial sources are low and the concentration of NO_x is high,so the hazardness is severe,therefore.It's urgent to harness the high concentration NO_x from industry.At present,there are many technologies to deal with NO_x such as SCR,SNCR, Photocatalytic Oxidation,denitration with reburning,and biochemical treatment. They have both advantages and disadvantages,so the development of the efficient and economical technology is an interesting subject in the field.In recent years,a new technology of catalytic reduction using activated carbons as reducing agent interests the researchers.Compared with the gaseous reducing agents(such as ammonia, methane),activated carbons can have good performance in the reduction of NO. Moreover,they are cheap and free of secondary pollution besides abundant sources, which make them a well applicable perspective in the field of denitration.There are usually metal minerals in the carbon precursor,which could make potential effect on nitrogen doping,and also could make cooperative effect with the surface nitrogen species.In this paper,some activated carbons were modified by nitrogen doping and the regularity for change of the surface physicochemical characters was studied with kinds of measurement technologies such as elemental analyzer,XPS,TGA and so on.At the same time,the reduction of NO with the modified carbons was investigated in a fixed-bed reactor.Combined with the above analysis of the surface chemistries,the mechanisms of the reduction of NO with the modified carbons were studied in details.Results showed that: 1.The effect of both nitrogen doping on the surface chemistries is significant. When the carbons had been annealed,the oxygen content decreased greatly,while the surface nitrogen content increased.The active site for nitrogen doping by annealing in ammonia is C-OH,and most incorporated nitrogen atoms locate at the edges of graphene structures,especially in the form of N-6 and N-5.The existence of Fe₂O₃ particles can facilitate the nitrogen doping,and C=O is the active site for the nitrogen doping,and most incorporated nitrogen atoms locate especially in the form of N-6 (N-X).2.The beginning reaction temperature of NO with the nitrogen-doped carbon reduction was lower than that with the carbon reduction by 200℃.Compared with the pure carbon,both the reactivity and selectivity of the modified carbons increased greatly.It may be attributed to the surface nitrogen species as catalytic centers.3.Some activated carbons loading metals(K,Fe,Mn,Co,Ni and Cu)were modified by nitrogen doping.Comparing the performance in the reduction of NO,the catalytic activity of Fe/activated carbon is excellent,besides,the Fe/activated carbon that was incorporated both nitrogen showed excellent activity for the reduction of NO. So,Fe/activated carbon was selected as the subject to study the cooperative effect of Fe₂O₃ and the surface nitrogen species for the reduction of NO.4.The carbon that was incorporated both nitrogen and Fe₂O₃ showed excellent activity for the reduction of NO in the presence of oxygen,and the NO conversion was higher than 40%at 500℃,which was due to the cooperative effect of Fe₂O₃ and the surface nitrogen species.Moreover the selectivity of modified carbon increased by 40%～60%.