Influence Of Activated Carbon’s Carbonyl And Carbonyl-active Metal Interaction On Desulfurization And Denitrification And Its Mechanism

Activated carbon dry desulfurization and denitrification integrated technology has been regarded as better application potential in low-temperature non-electric industries,such as sintered tail gas of steel plants,which is due to it can achieve simultaneous removal of multiple pollutants,basically no secondary pollution,low water consumption and easy regeneration etc.The surface of activated carbon（AC）is critical aspect of affecting its desulfurization and denitrification activity,which can as the active center for adsorption and oxidation.Its well-developed surface area and richer pore structure are conducive to the diffusion and transfer of molecules.Additionally,oxygen-containing functional groups are favor to improve the dispersion of active metals on the AC’s surface,thus promoting its desulfurization and denitrification performance.Recent publications have shown that carbonyl（C=O）is related to the desulfurization and denitrification activity of AC linearly,however,there is still lack of direct experimental evidence to qualitatively and quantitatively analyze its role and mechanism during desulfurization and denitrification.The maximum difficulty mainly owing to the complexity of the AC’s surface and nearly without achieve to decouple the combined effects of pore structure and surface functional groups,which makes it difficult for conducting independent studies of single functional groups.Therefore,the selection of suitable model compounds and the grafting of quantitative functional groups can achieve the decoupling of pore structure and surface functional groups,and further elucidate the mechanism of carbonyl on activated carbon-active metal interactions.The results of the study will guile the high-performance AC preparation and provide theoretical guidance for the targeted preparation of high-performance desulfurization and denitrification AC,which has good application prospects.In this study,carbon nanotubes（CNTs）were used as model materials to simulate the basic constitutive structure of AC,and carbonyl was modified onto the carbon surface by non-covalent bonding to achieve active metal loading by isovolumetric impregnation.The interaction of carbonyl and typical active metal Mn and its influence mechanism on the performance of desulfurization and denitrification were revealed by FTIR,XPS,XRD and Raman characterization,and the conclusions were as following:（1）The effect of pore size on the performance of desulfurization and denitrification was investigated under the quantitative carbonyl group.It was found that the sulfur capacity increased from 26.9 mg/g to 28.6 mg/g and NO conversion increased from 1.1%to 3.8%with pore size increased.When different pore size CNTs modified with quantitative carbonyl groups,the sulfur capacity increased to 61.1 mg/g and 54.7 mg/g,NO conversion increased to 3.8%and 19.7%,respectively,those results indicated that the desulfurization and denitrification activities were significantly enhanced.The differences of sulfur capacity and NO conversion of CNTs with different pore sizes without modified carbonyl groups were little,which proved that the introduction of carbonyl groups was the key factor for the improvement of sulfur capacity and NO conversion.（2）The effect of carbonyl group on the performance of desulfurization and denitrification was investigated at the same pore size.It was found that the desulfurization activity was significantly enhanced with the carbonyl content increased,and the maximum sulfur capacity reached 61.1 mg/g when the carbonyl content was 47.17%.When the PQ loading was 1:8,the carbonyl amount was higher,but the sulfur capacity was lower,which probably because the PQ loading occupied the active site on the surface and finally weakened the adsorption of SO₂ on the surface.The enhanced mechanism of denitrification by carbonyl were put forward:NO is adsorbed on the carbonyl group to form C（ONO）,NH₃is adsorbed on the surface active site in the form of CO^-（NH₄）⁺,and the formed complexes react with each other to form N₂ and H₂O and release.（3）The carbonyl group-containing functionalized carbon nanotubes were used as carriers and loaded with active metals on their surfaces to investigate the carbonyl-active metal interactions and the mechanism of their combined effect on the desulfurization activity.The results shown that the loading of Mn O_x further promoted the increase of sulfur capacity（from 61.1 mg/g to 85.6 mg/g）compared with carbonyl modified carbon nanotubes,and the highest desulfurization activity was achieved at a loading of 7.5%.The surface activity was enhanced by the active metal loading,and the carbonyl group as the oxidation center together with the multivalent distribution of Mn O_x promoted the oxidation of SO₂ to SO₃.The sulfur capacity decreased when the loading of Mn O_x was 10%,probably due to the saturation of the surface active sites by excessive loading,which led to the agglomeration of the active components and weakened the adsorption of SO₂.（4）The study of carbonyl-active metal interaction and its effect on denitrification showed that the NO conversion was positively correlated with Mn O_x loading under carbonyl modification,and the NO conversion increased from 4.6%to 13.3%,which was attributed to the enhanced dispersion of surface-loaded Mn O_x by carbonyl,which provided more adsorption sites for NO and NH₃ adsorption,and the alkaline functional group carbonyl group favors the transport and storage of denitrification products.It is further demonstrated that the carbonyl group together with the active metal facilitates the conversion of NO to N₂.The increased chemisorbed oxygen on the surface after active metal loading can be used as an acid site to increasing adsorption NH₃,thus forms NH₄+,which in turn accelerates the SCR reaction.The results of this study provide a theoretical basis for the targeted preparation of high-performance AC.