Mo-Mn/TiO_2催化剂的协同脱硝脱汞特性
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摘要
采用浸渍法制备Mo-Mn/TiO_2催化剂,研究了反应温度、HCl和SO_2对其模拟烟气协同脱硝脱汞活性的影响.研究表明,过高的反应温度不利于汞的脱除过程,过低的温度则抑制脱硝反应的顺利进行,但在200℃时可兼具最优的脱硝和脱汞效率;HCl的加入促进汞的高效氧化,却明显降低催化剂对NO的转化;而烟气中SO_2的存在对催化剂的脱硝和脱汞过程均起到抑制作用.利用XRD、H_2-TPR和XPS等表征手段对硫中毒反应前后的催化剂进行了研究.结果表明,硫酸盐在催化剂表面的不断沉积和活性组分Mn4+及化学吸附氧Oα的消耗乃是致使催化剂失活的主要原因;另外,SO_2与NH3和Hg0对催化剂表面活性位点的竞争吸附,也严重抑制催化剂的脱硝和脱汞反应.Mo-Mn/TiO_2的脱硝过程是通过Mn价态之间的相互转化来完成的,其中元素Mo和O_2是其转化得以实现的助剂;Mo-Mn/TiO_2对汞的脱除以催化氧化为主,金属氧化物中的晶格氧将Hg~0转化为HgO而被脱除.
Mo/Mn-TiO_2 catalysts were prepared by impregnation method, the effects of reaction temperature, HCl and SO_2 on denitrification and mercury removal from simulated flue gas being studied. The studies showed that, too high reaction temperature was not conducive to the removal of mercury, and too low temperature inhibited the denitrification reaction, but the best efficiency of denitrification and mercury removal can be obtained at 200℃. The addition of HCl can promote the oxidation of mercury, but significantly decrease the rate of NO conversion. The presence of SO_2 in the flue gas played an inhibitory role in the process of denitrification and mercury removal. The catalysts, which before and after the reaction of sulfur poisoning, were studied by XRD, H_2-TPR and XPS. The results showed that the continuous deposition of sulfate on the catalyst surface and the consumption of active component Mn~(4+) and chemical oxygen O_α were the main reasons for the deactivation of the catalyst. In addition, the competitive adsorption of SO_2 with NH_3 and Hg~0 on the surface active sites of the catalyst also severely inhibited the denitration and mercury removal. The denitration process of Mo-Mn/TiO_2 was accomplished by the conversion of Mn valence states, among which both Mo and O_2 were the assistant for the conversion. The removal of mercury by Mo-Mn/TiO_2 was mainly catalytic oxidation, the lattice oxygen in the metal oxide transforms Hg0 into Hg O and was removed.
Mo/Mn-TiO_2 catalysts were prepared by impregnation method, the effects of reaction temperature, HCl and SO_2 on denitrification and mercury removal from simulated flue gas being studied. The studies showed that, too high reaction temperature was not conducive to the removal of mercury, and too low temperature inhibited the denitrification reaction, but the best efficiency of denitrification and mercury removal can be obtained at 200℃. The addition of HCl can promote the oxidation of mercury, but significantly decrease the rate of NO conversion. The presence of SO_2 in the flue gas played an inhibitory role in the process of denitrification and mercury removal. The catalysts, which before and after the reaction of sulfur poisoning, were studied by XRD, H_2-TPR and XPS. The results showed that the continuous deposition of sulfate on the catalyst surface and the consumption of active component Mn~(4+) and chemical oxygen O_α were the main reasons for the deactivation of the catalyst. In addition, the competitive adsorption of SO_2 with NH_3 and Hg~0 on the surface active sites of the catalyst also severely inhibited the denitration and mercury removal. The denitration process of Mo-Mn/TiO_2 was accomplished by the conversion of Mn valence states, among which both Mo and O_2 were the assistant for the conversion. The removal of mercury by Mo-Mn/TiO_2 was mainly catalytic oxidation, the lattice oxygen in the metal oxide transforms Hg0 into Hg O and was removed.
引文
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[26]唐念,胡将军,盘思伟,等.Mn-Nb复合催化剂脱汞性能及抗硫特性试验研究[J].环境科学与技术,2015,38(2):184-188.
[27]Xu W,He H,Yu Y.Deactivation of a Ce/Ti O2catalyst by SO2in the selective catalytic reduction of NO by NH3[J].The Journal of Physical Chemistry C,2009,113:4426-4432.
[28]Jiang B,Deng B,Zhang Z,et al.Effect of Zr addition on the low-temperature SCR activity and SO2 tolerance of Fe-Mn/Ti catalysts[J].The Journal of Physical Chemistry C,2014,118:14866-14875.
[29]李泽英,唐清,左赵宏.载体对V2O5-Mo O3/Ti O2催化剂表面性质及其选择性催化还原脱硝性能的影响[J].工业催化,2016,24(7):41-48.
[30]Zhang J X,Zhang S L,Cai W,et al.The characterization of Cr Ce-doped on Ti O2-pillared clay nanocomposites for NO oxidation and the promotion effect of Ce Ox[J].Applied Surface Science,2013,268:535-540.
[31]Romano E J,Schulz K H.A XPS investigation of SO2adsorption on ceria-zirconia mixed-metal oxides[J].Applied Surface Science,2005,246(1-3):262-270.
[32]Rumayor M,Díaz-Somoano M,Lopez-Anton M A,et al.Mercury compounds characterization by thermal desorption[J].Talanta,2013,114:318-322.
[33]Wang F Y,Wang S X,Meng Y,et al.Mechanisms and roles of fly ash composition on the adsorption and oxidation of mercury in flue gas from coal combustion[J].Fuel,2016,163:232-239.
[34]杜学森.钛基SCR脱硝催化剂中毒失活及抗中毒机理的实验和分子模拟研究[D].杭州:浙江大学,2014.
[35]樊小鹏,李彩亭,曾光明,等.Cu O-Ce O2/AC吸附燃煤烟气中元素汞的实验研究[J].环境工程学报ISTIC,2010,4(2):393-397.
[36]游华伟.Mn Ox-Ce O2/γ-A12O3催化剂脱硝脱汞的实验研究[D].武汉:华中科技大学,2012.
[37]王鹏鹰,苏胜,向军,等.低温SCR催化剂脱硝脱汞实验研究[J].燃烧科学与技术,2014,20(5):423-427.
[38]郭静,李彩亭,路培,等.Ce O2改性Mn Ox/Al2O3的低温SCR法脱硝性能及机制研究[J].环境科学,2011,32(8):2240-2246.
[2]熊志波,金晶,路春美,等.铁基催化剂的微波水热处理对其SCR脱硝性能的影响[J].中国环境科学,2014,34(7):1785-1789.
[3]董晓真.同时脱硝脱汞催化剂研究进展[J].山东化工,2016,45(19):58-59.
[4]邢微波,路好,张安超,等.Ag/Ag Cl可见光催化剂湿法脱除烟气中单质汞[J].中国环境科学,2017,37(2):503-510.
[5]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.
[6]Yamaguchi A,Akiho H,Ito S.Mercury oxidation by copper oxides in combustion flue gases[J].Powder Technology,2008,180(1):222-226.
[7]高鹏,向军,张安超.壳聚糖吸附剂脱除燃煤模拟烟气中汞的试验研究[J].中国环境科学,2010,30(6):733-737.
[8]廖伟平.Mn-Ce/Ti O2催化剂低温选择性催化还原NO机理研究[D].南京:南京师范大学,2012.
[9]王晓刚,张益坤,丁峰,等.SCR催化剂对汞的催化氧化研究进展[J].环境科学与技术,2014,37(4):68-73.
[10]姚杰,仲兆平.蜂窝状SCR脱硝催化剂成型配方选择[J].中国环境科学,2013,33(12):2148-2156.
[11]Pena D A,Uphade B S,Smirniotis P G.Ti O2-supported metal oxide catalysts for low-temperature selective catalytic reduction of NO with NH3:I.Evaluation and characterization of first row transition metals[J].Journal of Catalysis,2004,221(2):421-431.
[12]石研妮.多级大孔-介孔Mn/Ti O2低温SCR脱硝催化剂的制备及其反应机理研究[D].大连:大连理工大学,2014.
[13]陈玲,李彩亭,高招,等.Mn Ox/HZSM-5去除烟气中元素态汞的实验研究[J].中国环境科学,2010,30(8):1026-1031.
[14]唐晓龙,郝吉明,易红宏,等.活性炭改性整体催化剂上低温选择性还原NOx[J].中国环境科学,2007,27(6):845-850.
[15]郑玉婴,汪谢.Mn基低温SCR脱硝催化剂的研究进展[J].功能材料,2014,11(45):11008-11012.
[16]Ji L,Pavani M S,Panagiotis G S,et al.Manganese Oxide/Titania materials for removal of NOx and elemental mercury from flue gas[J].Energy&Fuels,2008,22(4):2299-2306.
[17]He J,Gunugunuri K R,et al.Simultaneous Removal of Elemental Mercury and NO from Flue Gas Using Ce O2Modified Mn Ox/Ti O2 Materials[J].Energy&Fuels.2013,27:4832-4839.
[18]Wang Y Y,Shen B X,et al.Simultaneous Removal of NO and Hg0 from Flue Gas over Mn-Ce/Ti-PILCs[J].Environmental Science&Technology,2015,49:9355-9363.
[19]王晓梅.W-Mn-Ti O2复合金属氧化物的低温NH3-SCR性能的研究[D].大连:大连理工大学,2015.
[20]闫智锋.Mo/HZSM-5催化剂上NH3选择性催化还原NO反应机理的密度泛函理论研究[D].太原:太原理工大学,2015.
[21]陈杰,晏乃强,瞿赞,等.强化SCR脱硝催化剂转化零价汞的初步研究[J].环境科学与技术,2013,36(5):86-88.
[22]Yan R,Liang D T,Tsen L,et al.Bench-scale experimental evaluation of carbon performance on mercury vapour adsorption[J].Fuel,2004,83(17/18):2401-2409.
[23]陈进生.火电厂烟气脱硝技术-选择性催化还原法[J].北京:中国电力出版社,2008:99-104.
[24]Lu P,Li C T,Zeng G M,et al.Low temperature selective catalytic reduction of NO by activated carbon fiber loading lanthanum oxide and ceria[J].Applied Catalysis B:Environmental,2010,96:157-161.
[25]李锋,於承志,张朋,等.低SO2氧化率脱硝催化剂的开发[J].电力科技与环保,2010,26(4):18-21.
[26]唐念,胡将军,盘思伟,等.Mn-Nb复合催化剂脱汞性能及抗硫特性试验研究[J].环境科学与技术,2015,38(2):184-188.
[27]Xu W,He H,Yu Y.Deactivation of a Ce/Ti O2catalyst by SO2in the selective catalytic reduction of NO by NH3[J].The Journal of Physical Chemistry C,2009,113:4426-4432.
[28]Jiang B,Deng B,Zhang Z,et al.Effect of Zr addition on the low-temperature SCR activity and SO2 tolerance of Fe-Mn/Ti catalysts[J].The Journal of Physical Chemistry C,2014,118:14866-14875.
[29]李泽英,唐清,左赵宏.载体对V2O5-Mo O3/Ti O2催化剂表面性质及其选择性催化还原脱硝性能的影响[J].工业催化,2016,24(7):41-48.
[30]Zhang J X,Zhang S L,Cai W,et al.The characterization of Cr Ce-doped on Ti O2-pillared clay nanocomposites for NO oxidation and the promotion effect of Ce Ox[J].Applied Surface Science,2013,268:535-540.
[31]Romano E J,Schulz K H.A XPS investigation of SO2adsorption on ceria-zirconia mixed-metal oxides[J].Applied Surface Science,2005,246(1-3):262-270.
[32]Rumayor M,Díaz-Somoano M,Lopez-Anton M A,et al.Mercury compounds characterization by thermal desorption[J].Talanta,2013,114:318-322.
[33]Wang F Y,Wang S X,Meng Y,et al.Mechanisms and roles of fly ash composition on the adsorption and oxidation of mercury in flue gas from coal combustion[J].Fuel,2016,163:232-239.
[34]杜学森.钛基SCR脱硝催化剂中毒失活及抗中毒机理的实验和分子模拟研究[D].杭州:浙江大学,2014.
[35]樊小鹏,李彩亭,曾光明,等.Cu O-Ce O2/AC吸附燃煤烟气中元素汞的实验研究[J].环境工程学报ISTIC,2010,4(2):393-397.
[36]游华伟.Mn Ox-Ce O2/γ-A12O3催化剂脱硝脱汞的实验研究[D].武汉:华中科技大学,2012.
[37]王鹏鹰,苏胜,向军,等.低温SCR催化剂脱硝脱汞实验研究[J].燃烧科学与技术,2014,20(5):423-427.
[38]郭静,李彩亭,路培,等.Ce O2改性Mn Ox/Al2O3的低温SCR法脱硝性能及机制研究[J].环境科学,2011,32(8):2240-2246.