An ammonia-free denitration method: Direct reduction of NOx over activated carbon promoted by Cu-K bimetals
-
摘要: 本研究利用等体积浸渍法制备出来一种Cu-K双金属负载活性炭,可直接用于烟气脱硝,并在较宽的温度窗口下保持良好的脱硝效果。研究还通过程序升温表面反应 (TPSRs) 以及 BET、SEM、XRD、XPS、H2-TPR、Raman 和 FT-IR 等表征手段对双金属辅助脱硝的机理进行了研究与讨论。研究结果表明,炭材料表面形成的活性官能团是重要的中间产物,在还原过程中起着关键作用。氧的加入明显促进了化学吸附和中间产物含氧官能团 C(O) 的形成,提高了NO的还原速率。双金属氧化物催化直接还原NO的效果明显,铜∶钾= 2∶1 时,在300 ℃下脱硝率可达 90%,催化活性主要来自 CuO/Cu2O 的氧化还原循环,钾抑制了铜在炭材料表面的团聚,有效提高了铜的催化效率。Abstract: As ammonia slip becomes more serious with the traditional deNOx application, ammonia-free technologies have received more and more attention recently. Cu-K bimetal loaded activated carbon catalysts were prepared by equivalent-volume impregnation method for the direct reduction of NO and showed good NO reduction performance in a wide temperature range under temperature-programmed surface reactions (TPSRs) conditions in aerobic and anaerobic environments. The catalysts were characterized by BET, SEM, XRD, XPS, H2-TPR, Raman and FT-IR techniques and the NO reduction mechanism was analyzed. Experimental results show that the active functional groups formed on the surface of activated carbon are the important intermediate products and play a key role in the reduction reaction. The presence of O2 greatly promotes the formation of the intermediate, C(O) (Oxygen-containing functional groups on the carbon surface), leading to the increase reduction rate of NO. The bimetallic oxides catalysts are obviously effective to directly reduce NO. When the ratio of copper: potassium is 2∶1, the NO reduction efficiency is about 90% at 300 °C. The catalytic activity mainly depends on the redox cycle of CuO/Cu2O, and the potassium inhibits the agglomeration of copper on the surface of carbon materials and enhances the catalytic reactivity of Cu.
-
Key words:
- activated carbon /
- ammonia-free denitration /
- bimetal catalysis /
- Cu /
- K
-
Table 1 Elemental analysis of coconut-shell activated carbon
Element A N C H S O Content wmass/% 1.83 0.19 94.06 0.76 0 3.16 Table 2 Surface area and pore volume of CSAC obtained by BET (N2, 77 K)
Char SBET /(m2·g−1) vMes /(cm3·g−1) vtotal /(cm3·g−1) CSAC 841.195 0.029 0.457 Table 3 Cu 2p XPS curve-fitting analysis for 2Cu-K-CSAC
Material Cu 2p XPS curve-fitting /% Cu(Ⅱ)/ Cu(Ⅰ/0) Cu(Ⅱ) Cu(Ⅰ) Cu(0) 2Cu-K-CSAC before reaction 23.07 56.77 20.16 1∶3.33 2Cu-K-CSAC after reaction 27.39 42.40 30.21 1∶2.65 -
[1] QIANG L, XIAO Y L, HONG W, QIAN Q H. Current situation and trend analysis of clean heating in north China[J]. Energy China,2021,1:17−22. [2] CHANG Z. Research on development and engineering application of key technology of denitration of central heating boiler flue gas[D]. Nanjing: Southeast University, 2018. [3] ZHANG X, FUNG J, LAU A, HOSSAIN, M. S. HUANG, W. Air quality and synergistic health effects of ozone and nitrogen oxides in response to China's integrated air quality control policies during 2015–2019[J]. Chemosphere,2020,268(2021):129385. [4] HENDRYX M, ZULLIG K J, LUO J H. Impacts of coal use on health[J]. Annu Rev Publ Health,2020,41(1):397−415. doi: 10.1146/annurev-publhealth-040119-094104 [5] TAO Z, ZHEN H Z. Effects of nitrogen oxides and meteorological factors on ozone pollution in the ambient air of Rizhao city[J]. Energy Conserv Environ Prot,2019,2:80−81. [6] YUE J S, NIAN X Z. Ammonia emission without participating in the reduction reaction of denitrification[J]. Sci Manag,2019,39(6):68−75. [7] JIAN T, JIAN H Y, OU C, GUANG X Y. Excessive ammonia escape is another cause of aggravating atmospheric haze[J]. Energy China,2020,42(10):45−47. [8] YAN W, XUE J D. Ammonia pollution: the neglected culprit of smog[J]. Ecolog Econ,2017,33(6):6−9. [9] ZHANG Y, FENG Q, LI S, XU K, PEI Y, ZHU Y. Study on operation status of SCR denitration system in Chinese coal-fired power plants[J]. IOP Confer Ser: EES,2020,467(1):012119. doi: 10.1088/1755-1315/467/1/012119 [10] GAO Y W, PAN W G, GUO R T, ZHEN W L, ZHANG Q, SHI C L, ZHAO X. Review of denitration by SNCR in cement kilns[J]. Adv Mater Res,2013,864–867:1474−1477. [11] CHEN H, LUO M, WANG Y, ZHANG Q, LIU Y. Influence of coal-fired boiler fly ash on SCR denitration catalysts and preventive measures[J]. J Combust Sci Technol,2017,23(3):200−211. [12] YAO Y, GUI S, YANG J, WEI J, ZHANG W, LI P, XUE F, SU J, LIU X. Cause analysis and countermeasure of blockage in urea pyrolysis denitration system of coal-fired power plant[J]. IOP Confer Ser: EES,2021,651(2):022058. doi: 10.1088/1755-1315/651/2/022058 [13] ZHANG J. Research and application of dry flue gas denitration method for small coal-fired boiler[J]. Coal Chem Ind,2019,42(7):139−141. [14] KE Y. Experimental study on the purification of NOx by hot carbon reduction method[J]. Environ Prot Chem Ind,1984,3:4−47. [15] MJ I G, LINARES S A, RADOVIC L R, SALINAS-MARTINEZ de LECEA C. NO reduction by activated carbons. 7. Some mechanistic aspects of uncatalyzed and catalyzed reaction[J]. Energy Fuels,1996,10(1):158−168. doi: 10.1021/ef950066t [16] YANG J, MESTL G, HEREIN D, SCHLGL R, FIND J. Reaction of NO with carbonaceous materials: 1. Reaction and adsorption of NO on ashless carbon black[J]. Carbon,2000,38(5):715−727. doi: 10.1016/S0008-6223(99)00150-5 [17] SMITH R N, SWINEHART J, LESNINI D. The oxidation of cardon by nitric oxide[J]. J Phys Chem,1959,63(4):544−547. [18] GRZYBEK T, KLINIK J, SAMOJEDEN B, SUPRUN V, PAPP H. Nitrogen-promoted active carbons as DeNOx catalysts[J]. Catal Today,2008,137(2/4):228−234. doi: 10.1016/j.cattod.2007.11.009 [19] WANG Y, QIN N, CUI S, MA X, PENG S. Influence of biochar composition and micro-structure on the denitration of flue gases at high temperature[J]. Appl Sci-basel,2020,10(6):1920. doi: 10.3390/app10061920 [20] WU H X, CAI J, REN Q Q, XU J, CHU F H, LYU Q G. An efficient and economic denitration technology based on fuel pretreatment for cement cleaner production[J]. J Clean Prod,2020,272:122669. doi: 10.1016/j.jclepro.2020.122669 [21] LIN Y T, LI Y R, XU Z C, XIONG J, ZHU T Y. Transformation of functional groups in the reduction of NO with NH3 over nitrogen-enriched activated carbons[J]. Fuel,2018,223(1):312−323. [22] LI M X, YI Z J, LI N L, LI G W, ZHI Y L KAI W Z. Preparation and characterization of activated carbon modified by ferric oxide[J]. Carbon,2017,1:16−19. [23] LI M X, KAI W Z. Preparation and characterization of copper oxide modified activated carbon[J]. Carbon,2017,3:24−32. [24] ILLAN G M J, LINARES-SOLANO A, RADOVIC L R, SALINAS-MARTINEZ de LECEA C L. NO reduction by activated carbons. 4. Catalysis by calcium[J]. Energy Fuels,1995,9(1):112−118. doi: 10.1021/ef00049a017 [25] ILLAN G M J, LINARES-SOLANO A, SALINAS-MARTINEZ de LECEA C. NO reduction by activated carbon. 6. Catalysis by transition metals[J]. Energy Fuels,1995,9(6):976−983. doi: 10.1021/ef00054a007 [26] ILLANGOMEZ M J, LINARESSOLANO A, RADOVIC L R. NO reduction by activated carbons. 2. Catalytic effect of potassium[J]. Fuel Energy Abstracts,1995,36(3):97−103. [27] SHU Y, ZHANG F, WANG F, WANG H M. Catalytic reduction of NOx by biomass-derived activated carbon supported metals[J]. Chin J Chem Eng,2018,26(10):2077−2083. doi: 10.1016/j.cjche.2018.04.019 [28] TSCHAMBER V, BRILHAC] J F. Oxidation of carbon by NOx, with particular reference to NO2 and N2O[J]. Fuel,2008,87:131−146. doi: 10.1016/j.fuel.2007.04.012 [29] BUENO-LÓPEZ A, SORIANO-MORA J M, GARCÍA-GARCÍA A. Study of the temperature window for the selective reduction of NOx in O2-rich gas mixtures by metal-loaded carbon[J]. Catal Commun,2006,7(9):678−684. doi: 10.1016/j.catcom.2006.02.010 [30] LEI Z, YAN J, FANG J, SHUI H, KANG S. Catalytic combustion of coke and NO reduction in-situ under the action of Fe, Fe-CaO and Fe-CeO2[J]. Energy,2021,216:119246. doi: 10.1016/j.energy.2020.119246 [31] TIGHE C J, DENNIS J S, HAYHURST A N, TEIGG M. V. The reactions of NO with diesel soot, fullerene, carbon nanotubes and activated carbons doped with transition metals[J]. Proc Combust Inst,2009,32(2):1989−1996. doi: 10.1016/j.proci.2008.06.165 [32] YAMASHITA H, YAMADA H, TOMITA A. Reaction of nitric oxide with metal-loaded carbon in the presence of oxygen[J]. Appl Catal,1991,78(2):1−6. doi: 10.1016/0166-9834(91)80101-2 [33] BAILÓN-GARCÍA E, ELMOUWAHIDI A, RIBEIRO F, HENRIQUES C, PEREZ-CADENAS A F, MARÍN F C, MALDONADO-HÓDAR H J. Reduction of NO with new vanadium-carbon xerogel composites. Effect of the oxidation state of vanadium species[J]. Carbon,2020,156:194−204. doi: 10.1016/j.carbon.2019.09.047 [34] KIENER J, LIMOUSY L, JEGUIRIM M, LE MEINS J M, HAJJAR-GARREAU S, BIGOIN G, GHIMBEU C M. Activated carbon/transition metal (Ni, In, Cu) hexacyanoferrate nanocomposites for cesium adsorption[J]. Materials (Basel),2019,12(8):1253. doi: 10.3390/ma12081253 [35] YAN Y L, XIAN C L. Direct catalytic reduction of NO by zero-valent Iron nanocrystalline cluster supported on biomass activated carbon[J]. CIESC J,2019,70(3):1111−1119. [36] LI X C, DONG Z, DOU J, YU J, TAHMASEBI A. Catalytic reduction of NO using iron oxide impregnated biomass and lignite char for flue gas treatment[J]. Fuel Process Technol,2016,148:91−98. doi: 10.1016/j.fuproc.2016.02.030 [37] YANG N, YU J L, DOU J X, TAHMASEBI A, SONG H, MOGHTADERI B, LUCAS J, WALL T. The effects of oxygen and metal oxide catalysts on the reduction reaction of NO with lignite char during combustion flue gas cleaning[J]. Fuel Process Technol,2016,152:102−107. doi: 10.1016/j.fuproc.2016.06.010 [38] ILLÁN-GÓMEZ M J, RAYMUNDO-PIÑERO E, GARĆIA-GARĆIA A, LINARES-SOLANO A, SALINAS-MARTÍNEZ de LECEA C. Catalytic NOx reduction by carbon supporting metals[J]. Appl Catal B: Environ,1999,20:267−275. doi: 10.1016/S0926-3373(98)00119-2 [39] CATALAO R A, MALDONADO-HÓDAR F J, FERNANDES A, HENRIQUES C, RIBEIRO M F. Reduction of NO with metal-doped carbon aerogels[J]. Appl Catal B: Environ,2009,88(1/2):135−141. doi: 10.1016/j.apcatb.2008.09.019 [40] FENG B, LU G, WANG Y Q, GUO Y, GUO Y. Cocatalytic effect of potassium on NO reduction by activated carbon catalyzed by copper oxide[J]. Chin J Catal,2011,32(5):853−861. [41] VENEZUELA P, LAZZERI M, MAURI F. Theory of double-resonant Raman spectra in graphene: Intensity and line shape of defect-induced and two-phonon bands[J]. Phys Rev,2011,84(3):1−25. [42] ZHANG G Q, ZHONG L, ZHENG H Y, FU T J, JU Y B, WANG Y C. Influence of the surface oxygenated groups of activated carbon on preparation of a nano Cu/AC catalyst and heterogeneous catalysis in the oxidative carbonylation of methanol[J]. Appl Catal B: Environ,2015,179:95−105. doi: 10.1016/j.apcatb.2015.05.001 [43] TENG H, SUUBERG E M. Chemisorption of nitric oxide on char. 1. Reversible nitric oxide sorption[J]. J Chem Inform,1993,97(2):478−483. [44] TENG H, SUUBERG E M. Chemisorption of nitric oxide on char. 2. Irreversible carbon oxide formation[J]. Ind Eng Chem Res,1993,32(3):416−423. doi: 10.1021/ie00015a004 [45] ULÁN-GÓMEZ M J, LINARES SOLANO A, RADOVIC A L R, SALINAS-MARTÍNEZ de LECEA C. No reduction by activated carbons. some mechanistic aspects of uncatalyzed and catalyzed reaction[J]. Coal Sci Technol,1995,24(1):1799−1802.