| Activated coke which has good pore structure,rich surface functional groups and high thermostability is consider as a best denitrification and desulfurization catalysts.Based on this,NPAC-CoCeNi-a,NPAC-N-Co?0.7?CeNi-a and Mn-Ce-M/NPAC-a?Fe,Co,Ni?were prepared by equal volume impregnation method using low cost and high strength non-pitch coal-based activated coke?NPAC?as support.The effects of loadings,calcination temperatures and calcination times on the denitrification performance were investigated,and the effects of n?NH3?/n?NO?,O2 concentrations,H2O?g?and SO2 on the low temperature NH3-SCR activity were also investigated.The relationships between denitrification activity and surface functional groups,active metal,pore structure,redox properties et al.factors were recognized by characterization technology.The low temperature denitrification kinetic equation mode was built,and the reaction orders of NO,NH3 and O2 were determined.The main results and conclusions are as follows:1?The NOx removal rate of NPAC was approximately 20%.The single load Co Ox,CeOx,NiOx into NPAC could improve the low temperature denitrification performance,and the NOx removal rate at 150?was 48.86%,56.73%and50.01%,respectively.The Co-load CoOx,CeOx and NiOx could obvious enhanced the low temperature denitrification performance of NPAC,and the NOx removal rate of NPAC-CoCeNi-7 was 71.55%.The cobalt,cerium and nickel best loadings of NPAC-N were optimized.When the Co,Ce,Ni loadings were 4.9%,7%,8%,respectively,the NOx removal rate of NPAC-N-Co?0.7?CeNi-8 at 150?was75.26%.2?The optimum preparation conditions of NPAC-Co CeNi-a-7 was calcined at 500?for 1 h.The optimum preparation conditions of NPAC-N-Co?0.7?CeNi-8 was calcined at 500?for 1.5 h and melamine immersed for 5 h.3?When the ratio of n?NH3?/n?NO?<1,the denitrification activity of NPAC-CoCeNi-7 and NPAC-N-Co?0.7?CeNi-8 are increase from approximately 12%to71.25%and 75.86%with ratio increasing,respectively.And when the ratio of n?NH3?/n?NO?>1,the denitrification activity is almost constant with ratio increasing.When the O2 contents less than 7%,the denitrification activity of NPAC-Co CeNi-7 and NPAC-N-Co?0.7?CeNi-8 are increase from original 18%to71.68%and 75.79%with O2 contents increasing,respectively.And when the O2contents more than 7%,the denitrification activity does not change with the increase of O2 contents.The denitrification performance of NPAC-CoCeNi-7 and NPAC-N-Co?0.7?CeNi-8 decreacsd about 31%and 42%caused by SO2,and that decreased about 11%and 16%caused by H2O?g?4?NPAC-CoCeNi-a and NPAC-N-Co?0.7?CeNi-a comprises micropore and mesopore,and it have rich surface functional groups.The addition of Co,Ce,Ni into NPAC and NPAC-N destroy graphene crystallite structuce,and the diffraction peak corresponding to?111?decreased in intensity and the peaks corresponding to?010?and?110?divided into“left and right”pesks.The valence transition of Co2+?Co3+,Ce3+?Ce4+and Ni2+?Ni3+are beneficial to electronic migration and unsaturated bond formation,which could increase the concentrations of chemical adsorbed oxygen,and enhance the NO oxidation ability,and then promote“fast-SCR”reaction.Therefore the low temperature denitrification activity could improve.After melamine heat treatment,the relative contents of N-6 and N-5 are increase for 25%and 4%,respectively,and it is beneficial to NO adsorption.Besides,the addition of CoOx,CeOx and NiOx enhance the surface acidity of NPAC and NPAC-N,which are beneficial to the adsorption and activation ability of NH3.5?The introduction of Fe,Co,Ni significantly enhance the low temperature denitrification performances of MnOx-CeOx-4.39.The NOx removal rate of MnOx-CeOx-4.39 was increased from 59.56%to 77.85%?Mn-Ce-Fe/NPAC-7?,78.98%?Mn-Ce-Co/NPAC-7?and 81.36%?Mn-Ce-Ni/NPAC-7?,respectively.And the addition of Fe,Co,Ni increased the SO2 tolerance ability of Mn Ox-CeOx-4.39 about 15%,and H2O?g?tolerance ability about 8%.6?MnOx-CeOx-4.39,Mn-Ce-Fe/NPAC-7,Mn-Ce-Co/NPAC-7 and Mn-Ce-Ni/NPAC-7 have good thermostability and rich surface functional group.The addition of Fe,Co,Ni enhance the BET surface specific areas and change the pore structures which macropore change into mesopore.The new compound oxides CeFeO3 and NiMnO3 are formed in the MnOx-CeOx-4.39 after the addition of Fe and Ni,which are beneficial to improve the denitrification activity.The relative contents of Mn4+,Ce3+and chemical oxygen concentrations obvious increase after the introduction of Fe,Co and Ni.The synergistic effect between Mn,Ce and Fe,Co,Ni promote the enhancement of low temperature denitrification activity.The introduction of Fe,Co,Ni increase the redox ability and surface acidity of MnOx-CeOx-4.39,which the redox ability and surface acidity decreased in the following order:Mn-Ce-Ni/NPAC-7>Mn-Ce-Co/NPAC-7>Mn-Ce-Fe/NPAC-7>MnOx-CeOx-4.39.The SO2 deactivation mechanism of modified NPAC was proposed,which is active phase sulfate and ammonium sulfate deposition7?In the surface of MnOx-CeOx-4.39,Mn-Ce-Fe/NPAC-7,Mn-Ce-Co/NPAC-7 and Mn-Ce-Ni/NPAC-7,adsorbed NH3 could react with gaseous NO through E-R mechanism or react with adsorbed NO through L-H mechanism.8?When the space velocity>3600 h-1 and particle size in 0.3-1 nm,Mn-Ce-Ni/NPAC-7 could exclude the influence of inner and external diffusion.When O2contents<7.2%,the O2 average reaction order is 0.42,and when O2 contents>7.2%,the O2 average reaction order is 0.When NH3 contents<500 ppm,the NH3average reaction order is 0.57,and when NH3 contents>500 ppm,the NH3average reaction order is 0.NO average reaction order is 0.70.9?The kinetic mode of denitrification reaction over Mn-Ce-Ni/NPAC-7 was established under the condition:100-200?,O2 contents<7.2%,NH3 contents<500 ppm,0.8-1 nm particle size,and 12000 h-11 space velocity.The kinetic mode is rNO=2.20×104 exp?-15480/RT?[NO]0.70[NH3]0.57[O 2]0.42,and its activation energy is15.48 kJ/mol. |
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