Ce-Mn/TiO_2吸附剂的脱汞性能及抗SO_2特性
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摘要
采用浸渍法制备Mn/TiO_2(MT)、Ce/TiO_2(CT)和Ce-Mn/TiO_2(CMT)脱汞吸附剂,在固定床脱汞实验台上研究吸附剂的脱汞性能.结果表明,吸附温度为100～200°C时,3种吸附剂的脱汞性能均随温度的升高而增强;而在200～300°C范围内,脱汞效率均出现不同程度的降低.MT、CT及CMT吸附剂的脱汞效率在200°C时达到最高,分别为91%、58%和95%.MT和CT吸附剂的抗SO_2性能较弱,在N_2+6%O_2+1000×10~(-6)SO_2烟气条件下,30min内脱汞效率均下降到50%,而CMT吸附剂在2h内仍能保持80%以上的脱汞效率,表明在MT中掺杂Ce不仅可以提高吸附剂的脱汞性能,还可以增强抗SO_2性能.利用N_2吸附/脱附、X射线衍射(XRD)、H_2-程序升温还原(H_2-TPR)和X射线光电子能谱(XPS)等方法对吸附剂的物理化学性质进行表征,并对吸附产物进行热重分析(TG)和程序升温脱附实验(TPD),阐明了CMT脱汞吸附剂的抗SO_2特性机理.Ce的掺杂,提高了活性组分在吸附剂表面的分散度及Mn~(4+)的比例;相比于Mn O_2,CeO_2可优先与SO_2反应,抑制了SO_2对Mn~(4+)的毒害作用,从而提高了抗硫性能.
Mn/TiO_2(MT),Ce/TiO_2(CT)and Ce-Mn/TiO_2(CMT)sorbents for mercury removal were prepared by the impregnation method.Mercury adsorption experiments were conducted on a fixed-bed reactor.The mercury removal performance of the three sorbents gradually increased with the increase of temperature in the range of 100～200°C.The maximum mercury capture efficiency of 91%,58%and 95%were observed at 200°C for MT,CT and CMT,respectively.The mercury removal efficiency decreased when the temperature was higher than 200°C.When MT and CT sorbents were exposed in the flue gas with N_2+6%O_2+1000×10~(-6)SO_2,the decrease of mercury removal efficiency to 50%within 30min was observed,indicating the weak SO_2resistance of MT and CT.However,mercury removal efficiency of more than 80%was maintained by CMT within 2h.It revealed that Ce doping in MT not only improved the mercury removal performance,but also enhanced the SO_2resistance.Physicochemical characteristics of the sorbents were analyzed by N_2adsorption/desorption,X-ray diffraction(XRD),H_2-temperature programmed reduction(H_2-TPR)and X-ray photoelectron spectroscopy(XPS).The spent sorbents were analyzed by thermogravimetric analysis(TG)and temperature programmed desorption(TPD)experiments.Based on the experimental and characterization results,the mechanism of SO_2resistance of the CMT for mercury removal was interpreted.The doping of Ce improved the dispersion of active components on the sorbent surface and the ratio of Mn~(4+),which was favorable for mercury removal;Compared with MnO_2,CeO_2preferentially react with SO_2,which inhibited the toxic effect on Mn~(4+),thus improving the SO_2resistance.
Mn/TiO_2(MT),Ce/TiO_2(CT)and Ce-Mn/TiO_2(CMT)sorbents for mercury removal were prepared by the impregnation method.Mercury adsorption experiments were conducted on a fixed-bed reactor.The mercury removal performance of the three sorbents gradually increased with the increase of temperature in the range of 100～200°C.The maximum mercury capture efficiency of 91%,58%and 95%were observed at 200°C for MT,CT and CMT,respectively.The mercury removal efficiency decreased when the temperature was higher than 200°C.When MT and CT sorbents were exposed in the flue gas with N_2+6%O_2+1000×10~(-6)SO_2,the decrease of mercury removal efficiency to 50%within 30min was observed,indicating the weak SO_2resistance of MT and CT.However,mercury removal efficiency of more than 80%was maintained by CMT within 2h.It revealed that Ce doping in MT not only improved the mercury removal performance,but also enhanced the SO_2resistance.Physicochemical characteristics of the sorbents were analyzed by N_2adsorption/desorption,X-ray diffraction(XRD),H_2-temperature programmed reduction(H_2-TPR)and X-ray photoelectron spectroscopy(XPS).The spent sorbents were analyzed by thermogravimetric analysis(TG)and temperature programmed desorption(TPD)experiments.Based on the experimental and characterization results,the mechanism of SO_2resistance of the CMT for mercury removal was interpreted.The doping of Ce improved the dispersion of active components on the sorbent surface and the ratio of Mn~(4+),which was favorable for mercury removal;Compared with MnO_2,CeO_2preferentially react with SO_2,which inhibited the toxic effect on Mn~(4+),thus improving the SO_2resistance.
引文
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[22]Xu H M,Ma Y P,Huang W J,et al.Stabilization of mercury over Mn-based oxides:Speciation and reactivity by temperature programmed desorption analysis[J].Journal of Hazardous Materials,2017,321:745-752.
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[25]Luo M F,Chen J,Chen L S,et al.Structure and redox properties of Cex Ti1-x O2 solid solution[J].Chemistry of Materials,2001,13(1):197-202.
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[29]Sang M L,Hong S C.Promotional effect of vanadium on the selective catalytic oxidation of NH3 to N2 over Ce/V/TiO2 catalyst[J].Applied Catalysis B Environmental,2015,163(163):30-39.
[30]Maqbool M S,Pullur A K,Ha H P.Novel sulfation effect on low-temperature activity enhancement of CeO2-added Sb-V2O5/TiO2catalyst for NH3-SCR[J].Applied Catalysis B Environmental,2014,152-153(25):28-37.
[31]Wu Z B,Jin R B,Wang H Q,et al.Effect of ceria doping on SO2resistance of Mn/TiO2 for selective catalytic reduction of NO with NH3 at low temperature[J].Catalysis Communications,2009,10(6):935-939.
[32]Gao F Y,Tang X L,Yi H H,et al.Promotional mechanisms of activity and SO2 tolerance of Co-or Ni-doped MnOx-CeO2 catalysts for SCRof NOx with NH3 at low temperature[J].Chemical Engineering Journal,2017,317:20-31.
[33]Romano E J,Schulz K H.A XPS investigation of SO2 adsorption on ceria-zirconia mixed-metal oxides[J].Applied surface science,2005,246(1-3):262-270.
[34]Xu H M,Zhang H B,Zhao S J,et al.Elemental mercury(Hg0)removal over spinel LiMn2O4 from coal-fired flue gas[J].Chemical Engineering Journal,2016,299:142-149.
[35]Li J H,Chen J J,Ke R,et al.Effects of precursors on the surface Mn species and the activities for NO reduction over MnOx/TiO2 catalysts[J].Catalysis Communications,2007,8(12):1896-1900.
[36]Zhang A C,Xing W B,Zhang Z H,et al.Promotional effect of SO2 on CeO2-TiO2 material for elemental mercury removal at low temperature[J].Atmospheric Pollution Research,2016,7(5):895-902.
[37]张呈祥.Mn-Ce/Al2O3低温SCR脱硝催化剂抗SO2中毒性能研究[D].大连:大连理工大学,2015.Zhang C X.Study on SO2 resistance of Mn-Ce/Al2O3 for lowtemperature selective catalytic reduction of NOx[D].Dalian:Dalian University of Technology,2015.
[2]Cao Y,Gao Z Y,Zhu J S,et al.Impacts of halogen additions on mercury oxidation in a slipstream selective catalyst reduction SCRreactor when burning sub-bituminous coal[J].Environmental Science&Technology,2008,42(1):256.
[3]Granite E J,Myers C R,King W P,et al.Sorbents for mercury capture from fuel gas with application to gasification systems[J].Industrial&Engineering Chemistry Research,2006,45(13):4844-4848.
[4]赵鹏飞,郭欣,郑楚光.活性炭及氯改性活性炭吸附单质汞的机制研究[J].中国电机工程学报,2010,30(23):40-44.Zhao P F,Guo X,Zheng C G.Investigating the mechanism of elemental mercury binding on activated carbon and chlorineembedded activated carbon[J].Proceedings of the CSEE,2010,30(23):40-44.
[5]朱磊,李海龙,赵永椿,等.纳米硫化锌吸附脱除单质汞的实验研究[J].工程热物理学报,2017,38(1):203-207.Zhu L,Li H L,Zhao Y C,et al.Experimental study on Hg0 adsorption by nano-ZnS[J].Journal of engineering thermophysics,2017,38(1):203-207.
[6]张安超,张洪良,宋军,等.Mn-Co/MCM-41吸附剂表征及脱除烟气中单质汞研究[J].中国环境科学,2015,35(5):1319-1327.Zhang A C,Zhang H L,Song J,et al.Characterization and performance of Mn-Co/MCM-41 for elemental mercury removal from simulated flue gas[J].China Environmental Science,2015,35(5):1319-1327.
[7]赵鹏飞,郭欣,郑楚光.载银稻壳基吸附剂的制备与表征及其脱除Hg0的实验研究[J].中国电机工程学报,2012,32(5):61-67.Zhao P F,Guo X,Zheng C G.Synthesis and characterizations of silver-loaded rice husk ash sorbents and their performance for elemental mercury removal[J].Proceedings of the CSEE,2012,32(5):61-67.
[8]沈敏强,吴江,潘卫国,等.新型燃煤烟气汞吸附剂的评价研究[J].上海电力学院学报,2009,25(6):566-569.Shen M Q,Wu J,Pan W G,et al.Evaluation study on new sorbents for mercury in coal-fired flue gas[J].Journal of Shanghai University of Electric Power,2009,25(6):566-569.
[9]张星,李彩亭,樊小鹏,等.CeCl3/活性炭纤维去除模拟烟气中单质汞的实验研究[J].中国环境科学,2012,32(5):816-821.Zhang X,Li C T,Fan X P,et al.Experimental research of removing element mercury from simulated flue gas by CeCl3-loaded activated carbon fiber[J].China Environmental Science,2012,32(5):816-821.
[10]Presto A A,Granite E J.Survey of catalysts for oxidation of mercury in flue gas[J].Environmental Science&Technology,2006,40(18):5601-5609.
[11]Yao T,Duan Y F,Zhu C,et al.Investigation of mercury adsorption and cyclic mercury retention over MnOx/γ-Al2O3 sorbent[J].Chemosphere,2018,202:358-365.
[12]Li J F,Yan N Q,Qu Z,et al.Catalytic oxidation of elemental mercury over the modified catalyst Mn/alpha-Al2O3 at lower temperatures[J].Environmental Science&Technology,2010,44(1):426-31.
[13]Wang P Y,Su S,Xiang J,et al.Catalytic oxidation of Hg0 by CuO-Mn O2-Fe2O3/γ-Al2O3 catalyst[J].Chemical Engineering Journal,2013.
[14]Xu H M,Xie J K,Ma Y P,et al.The cooperation of Fe、Sn in a MnOx complex sorbent used for capturing elemental mercury[J].Fuel,2015,140:803-809.
[15]Zhang A C,Zhang Z H,Lu H,et al.Effect of promotion with Ru addition on the activity and SO2 resistance of MnOx-TiO2 adsorbent for Hg0 removal[J].Industrial&Engineering Chemistry Research,2015,54(11):2930-2939.
[16]Yang S J,Guo Y F,Yan N Q,et al.Capture of gaseous elemental mercury from flue gas using a magnetic and sulfur poisoning resistant sorbent Mn/γ-Fe2O3 at lower temperatures[J].Journal of Hazardous Materials,2011,186(1):508-515.
[17]Chen G Y,Zhang D,Zhang A C,et al.CrOx-Mn Ox-TiO2 adsorbent with high resistance to SO2 poisoning for Hg0 removal at low temperature[J].Journal of Industrial&Engineering Chemistry,2017:55.
[18]Zeng X B,Xu Y,Zhang B,et al.Elemental mercury adsorption and regeneration performance of sorbents FeMnOx enhanced via nonthermal plasma[J].Chemical Engineering Journal,2017,309:503-512.
[19]谢江坤.锰基复合氧化物及其对零价汞的吸附性能研究[D].上海:上海交通大学,2013.Xie J K.Study of manganese-based binary metal oxides and their capability for gaseous elemental mercury capture[D].Shanghai:Shanghai Jiao Tong University,2013.
[20]Wang P Y,Su S,Xiang J,et al.Catalytic oxidation of Hg(0)by Mn Ox-CeO2/γ-Al2O3 catalyst at low temperatures[J].Chemosphere,2014,101:49-54.
[21]李卓峰.含硫烟气中Ce改性Zr-Mn Ox催化剂脱汞性能的研究[D].大连:大连理工大学,2017.Li Z F.Study of element mercury removal efficiency over Ce modified Zr-Mn Ox in sulfur-containing flue gas[D].Dalian:Dalian University of Technology,2017.
[22]Xu H M,Ma Y P,Huang W J,et al.Stabilization of mercury over Mn-based oxides:Speciation and reactivity by temperature programmed desorption analysis[J].Journal of Hazardous Materials,2017,321:745-752.
[23]许静.MnxOy/Al2O3可再生脱汞吸附剂特性研究[D].南京:东南大学,2017.Xu J.Study on characteristics of Mnx Oy/Al2O3 regenerable mercury adsorbent[D].Nanjing:Southeast University,2017.
[24]Rumayor M,Díaz-Somoano M,Lopez-Anton M A,et al.Mercury compounds characterization by thermal desorption[J].Talanta,2013,114:318-322.
[25]Luo M F,Chen J,Chen L S,et al.Structure and redox properties of Cex Ti1-x O2 solid solution[J].Chemistry of Materials,2001,13(1):197-202.
[26]And G Q,Yang R T.Characterization and FTIR studies of Mn Ox-CeO2 catalyst for low-temperature selective catalytic reduction of NO with NH3[J].J.phys.chem.b,2004,108(40):15738-15747.
[27]Villase?or J,Reyes P,Pecchi G.Catalytic and photocatalytic ozonation of phenol on MnO2 supported catalysts[J].Catalysis Today,2002,76(2):121-131.
[28]Todorova S,Naydenov A,Kolev H,et al.Mechanism of complete n-hexane oxidation on silica supported cobalt and manganese catalysts[J].Applied Catalysis A General,2012,413(4):43-51.
[29]Sang M L,Hong S C.Promotional effect of vanadium on the selective catalytic oxidation of NH3 to N2 over Ce/V/TiO2 catalyst[J].Applied Catalysis B Environmental,2015,163(163):30-39.
[30]Maqbool M S,Pullur A K,Ha H P.Novel sulfation effect on low-temperature activity enhancement of CeO2-added Sb-V2O5/TiO2catalyst for NH3-SCR[J].Applied Catalysis B Environmental,2014,152-153(25):28-37.
[31]Wu Z B,Jin R B,Wang H Q,et al.Effect of ceria doping on SO2resistance of Mn/TiO2 for selective catalytic reduction of NO with NH3 at low temperature[J].Catalysis Communications,2009,10(6):935-939.
[32]Gao F Y,Tang X L,Yi H H,et al.Promotional mechanisms of activity and SO2 tolerance of Co-or Ni-doped MnOx-CeO2 catalysts for SCRof NOx with NH3 at low temperature[J].Chemical Engineering Journal,2017,317:20-31.
[33]Romano E J,Schulz K H.A XPS investigation of SO2 adsorption on ceria-zirconia mixed-metal oxides[J].Applied surface science,2005,246(1-3):262-270.
[34]Xu H M,Zhang H B,Zhao S J,et al.Elemental mercury(Hg0)removal over spinel LiMn2O4 from coal-fired flue gas[J].Chemical Engineering Journal,2016,299:142-149.
[35]Li J H,Chen J J,Ke R,et al.Effects of precursors on the surface Mn species and the activities for NO reduction over MnOx/TiO2 catalysts[J].Catalysis Communications,2007,8(12):1896-1900.
[36]Zhang A C,Xing W B,Zhang Z H,et al.Promotional effect of SO2 on CeO2-TiO2 material for elemental mercury removal at low temperature[J].Atmospheric Pollution Research,2016,7(5):895-902.
[37]张呈祥.Mn-Ce/Al2O3低温SCR脱硝催化剂抗SO2中毒性能研究[D].大连:大连理工大学,2015.Zhang C X.Study on SO2 resistance of Mn-Ce/Al2O3 for lowtemperature selective catalytic reduction of NOx[D].Dalian:Dalian University of Technology,2015.