Lead poisoning and regeneration of Mn-Ce/TiO2 catalysts for NH3-SCR of NOx at low temperature
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摘要: 考察了Pb对Mn-Ce/TiO2低温选择性催化还原(SCR)脱硝活性的影响,并对Pb中毒的催化剂进行了再生;结合氮吸附、SEM、XRD、FT-IR、H2-TPR和NH3-TPD等表征结果,研究了Mn-Ce/TiO2催化剂Pb中毒和再生活性恢复的原因。结果表明,Pb对Mn-Ce/TiO2催化剂脱硝活性有明显的抑制作用;当Pb的含量为11%时,Mn-Ce/TiO2催化剂在180 ℃下的脱硝效率从原来100%下降至44%。Pb在Mn-Ce/TiO2中的掺杂使得催化剂的比表面积以及活性组分Mn4+和Ce3+的含量降低,影响了氧化还原循环反应(Mn4+ + Ce3+ ↔ Mn3+ + Ce4+)的进行;此外,Pb的加入破坏了催化剂的酸性位点,阻碍了催化剂对NH3的吸附和活化。经硝酸再生后的Mn-Ce/TiO2催化剂的脱硝活性几乎完全恢复,在80–150 ℃下其脱硝活性甚至超过新鲜未中毒的催化剂,其原因主要在于硝酸再生能恢复催化剂的氧化还原能力、增大比表面积、并形成新的酸位点。
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关键词:
- 低温选择性催化还原脱硝 /
- Mn-Ce/TiO2 /
- Pb中毒 /
- 再生
Abstract: The effect of lead on the catalytic performance of Mn-Ce/TiO2 catalysts in the selective catalytic reduction (SCR) of NOx with ammonia at low temperature was investigated; with the help of nitrogen sorption, XRD, FT-IR spectroscopy, H2-TPR and NH3-TPD characterization, the causes of lead poisoning and acid regeneration were clarified. The results indicate that the doping of Pb in Mn-Ce/TiO2 leads to a significant decrease of the low-temperature SCR activity; with a Pb loading of 11%, the conversion of NO over Mn-Ce/TiO2 at 180 °C decreases from original 100% on the fresh catalyst to 44% on the Pd-poisoned catalyst. The presence of Pb may reduce the content of active Mn4+ and Ce3+ species on the Mn-Ce/TiO2 catalyst, which suppresses the redox cycle of Mn4+ + Ce3+ ↔ Mn3+ + Ce4+; moreover, the decrease of surface acidity on the Mn-Ce/TiO2 catalyst by the doping of Pb is also disadvantageous to the adsorption and activation of NH3. The Pd-poisoned Mn-Ce/TiO2 can be regenerated by nitric acid treatment; after the regeneration, the catalytic activity of Mn-Ce/TiO2 in NH3-SCR of NO is almost completely recovered and even exceeds that of the fresh catalyst at 80–150 °C. The nitric acid treatment can restore the redox capacity of Mn-Ce/TiO2, increase the surface area, and create new acid sites, which contribute to recovery of the activity of Pb-poisoned Mn-Ce/TiO2 catalyst in NH3-SCR.-
Key words:
- selective catalytic reduction /
- Mn-Ce/TiO2 /
- Pb poisoning /
- regeneration
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图 1 测试装置示意图
1: gas cylinders; 2: pressure reducing valve; 3: mass-flow meters; 4: mixed gas cylinder; 5: catalytic reactor; 6: tube furnace; 7: flue gas analyzer; 8: absorption pot for tail gas
Figure 1 Schematic diagram of the catalytic test device for the selective catalytic reduction (SCR) of NOx with ammonia at low temperature
表 1 Pb中毒催化剂再生前后的物化特性
Table 1 Textural properties the Mn-Ce/TiO2 catalysts before and after Pb poisoning and regeneration
Sample Specific surface area /(m2·g−1) Total pore volume /(cm3·g−1) Average pore size /nm Mn-Ce/TiO2 77.68 1.58 81.40 Pb(3%)-Mn-Ce/TiO2 46.32 0.60 51.67 Pb(7%)-Mn-Ce/TiO2 45.65 0.48 42.28 Pb(11%)-Mn-Ce/TiO2 35.11 0.18 27.68 $ {\rm{R}}{{\rm{e}}_{{{\rm{H}}_{\rm{2}}}{\rm{O}}}} $ 40.86 0.66 64.8 $ {\rm{R}}{{\rm{e}}_{{\rm{C}}{{\rm{H}}_{\rm{3}}}{\rm{COOH}}}} $ 40.92 0.68 66.23 $ {\rm{R}}{{\rm{e}}_{{\rm{HN}}{{\rm{O}}_{\rm{3}}}}} $ 50.94 1.11 86.95 -
[1] 郝吉明, 马广大, 王书肖. 大气污染控制工程[M]. 第三版. 北京: 高等教育出版社, 2010: 401−402.HAO Ji-ming, MA Guang-da, WANG Shu-xiao. Air Pollution Control Engineering [M]. 3rd Ed. Beijing: Higher Education Press, 2010: 401−402. [2] PARK T S, JEONG S K, HONG S H, HONG S C. Selective catalytic reduction of nitrogen oxides with NH3 over natural manganese ore at low temperature[J]. Ind Eng Chen Res,2015,40(21):4491−4495. [3] XU W Q, YU Y B, ZHANG C B, HE H. Selective catalytic reduction of NO with NH3 over a Ce/TiO2 catalyst[J]. Catal Commun,2008,9(6):1453−1457. doi: 10.1016/j.catcom.2007.12.012 [4] 孙科, 刘伟, 王岳军, 莫建松, 刘越, 吴忠标. Ce-Mn/TiO2低温SCR脱硝催化剂成型工艺中添加剂的影响实验研究[J]. 环境污染与防治,2013,35(11):37−41. doi: 10.3969/j.issn.1001-3865.2013.11.009SUN Ke, LIU Wei, WANG Yue-jun, MO Jian-song, LIU Yue, WU Zhong-biao. Experimental study on influences of additives in the molding process of Ce-Mn/TiO2 catalyst for the low-temperature selective catalytic reduction of NOx[J]. Environ Pollut Control,2013,35(11):37−41. doi: 10.3969/j.issn.1001-3865.2013.11.009 [5] CASAPU M, KRÖCHERR O, ELSENER M. Screening of doped MnOx-CeO2 catalysts for low temperature NO-SCR[J]. Appl Catal B: Environ,2009,88(3):413−419. [6] TANG X L, HAO J M, YI H H, NING P. Low-temperature SCR of with NH3 on Mn-based catalysts modified with cerium[J]. J Rare Earth,2007,01:240−243. [7] ANDREOLI S, DEORSOLA F A, PIRONE R. MnOx-CeO2 catalysts synthesized by solution combustion synthesis for the low-temperature NH3-SCR[J]. Catal Today,2015,253:199−206. doi: 10.1016/j.cattod.2015.03.036 [8] QI N, DAN H, LI X. Effect of Cu doping on the SCR activity of Mn-Ce/ATP catalyst[J]. Russ J Appl Chem,2018,91(1):136−142. doi: 10.1134/S1070427218010214 [9] 王晓伟, 王虎. 脱硝催化剂的失活原因分析及再生方法研究进展[J]. 山东化工,2015,44(17):37−39. doi: 10.3969/j.issn.1008-021X.2015.17.013WANG Xiao-wei, WANG Hu. The research progress of SCR catalyst deactivation reason and regeneration method[J]. Shandong Chem Ind,2015,44(17):37−39. doi: 10.3969/j.issn.1008-021X.2015.17.013 [10] 邓双, 张凡, 刘宇, 石应杰, 王红梅, 张辰, 王相凤, 曹晴. 燃煤电厂铅的迁移转化研究[J]. 中国环境科学,2013,33(7):1199−1206.DENG Shuang, ZHANG Fan, LIU Yu, SHI Ying-jie, WANG Hong-mei, ZHANG Chen, WANG Xiang-feng, CAO Qing. Lead emission and speciation of coal-fired power plants in China[J]. J Environ Sci-China,2013,33(7):1199−1206. [11] 陈耿, 柯钊跃. 唐念. 张凯, 刘军. 燃煤电厂烟气中铅的测定方法初探[J]. 环境监测管理与技术,2020,32(4):52−54. doi: 10.3969/j.issn.1006-2009.2020.04.012CHEN Geng, KE Zhao-yue, TANG Nian, ZHANG Kai, LIU Jun. Preliminary study on test method for lead in flue gas from coal-fired power plant[J]. Adm Techn Environ Monit,2020,32(4):52−54. doi: 10.3969/j.issn.1006-2009.2020.04.012 [12] GUO R T, LU C Z, PAN W G, ZHEN W L, WANG Q S, CHEN Q L, DING H L, YANG N Z. A comparative study of the poisoning effect of Zn and Pb on Ce/TiO2 catalyst for low temperature selective catalytic reduction of NO with NH3[J]. Catal Commun,2015,59:136−139. doi: 10.1016/j.catcom.2014.10.006 [13] 姜烨. 钛基SCR催化剂及其钾、铅中毒机理研究[D]. 杭州: 浙江大学, 2010.JIANG Ye. Study on titania-based SCR catalysts and their poisoning mechanism of potassium and lead[D]. Hangzhou: Zhejiang University, 2010. [14] CHEN J P, BUZANOWSKI M A, YANG R T, CICHANOWICZ J E. Deactivation of the vanadia catalyst in the selective catalytic reduction process[J]. Air Repair,1990,40(10):1403−1409. [15] 纪妍. 脱硝催化剂重金属中毒及其再生技术的研究[D]. 华北电力大学, 2017.JI Yan. Study on heavy metal poisoning and its regeneration technology of DeNOx catalyst[D]. Beijing: North China Electric Power University, 2017. [16] LI Q C, LIU Z Y, LIU Q Y. Kinetics of vanadium leaching from a spent industrial V2O5/TiO2 catalyst by sulfuric acid[J]. Ind Eng Chen Res,2014,53:2956−2962. doi: 10.1021/ie401552v [17] YU Y K, HE C, CHEN J S, YIN L Q, QIU T X, MENG X R. Regeneration of deactivated commercial SCR catalyst by alkali washing[J]. Catal Commun,2013,39(5):78−81. [18] ZHOU L L, LIA C T, ZHAO L K, ZENG G M, GAO L, WANG Y, YU M E. The poisoning effect of PbO on Mn-Ce/TiO2 catalyst for selective catalytic reduction of NO with NH3 at low temperature[J]. Appl Surf Sci,2016,389:532−539. doi: 10.1016/j.apsusc.2016.07.136 [19] THIRUPATHI B, SMIRNIOTIS P G. Nickel-doped Mn/TiO2 as an efficient catalyst for the low-temperature SCR of NO with NH3: Catalytic evaluation and characterizations[J]. J Catal,2012,288:74−83. doi: 10.1016/j.jcat.2012.01.003 [20] WAN Y P, ZHAO W R, TANG Y, LI L, WANG H J, CUI Y L, GU J L, LI Y S, SHI J L. Ni-Mn bi-metal oxide catalysts for the low temperature SCR removal of NO with NH3[J]. Appl Catal B: Environ,2014,148:114−122. [21] 黄继辉, 童华, 童志权, 张俊峰, 黄妍. H2O和SO2对Mn-Fe/MPS催化剂用于NH3低温还原NO的影响[J]. 过程工程学报,2008,8(16):517−522.HUANG Ji-hui, TONG Hua, TONG Zhi-quan, ZHANG Jun-feng, HUANG Yan. Effects of H2O and SO2 on Mn-Fe/MPS catalyst for NO reduction by NH3 at lower temperatures[J]. Chin J Process Eng,2008,8(16):517−522. [22] CENTENO M A, CARRIZOSA I, ODREOZOLA J A. NO-NH3 coad sorption on vanadia titania catalysts: Ddetermination of the reduction degree of vanadium[J]. Appl Catal B: Environ,2001,29:307−314. doi: 10.1016/S0926-3373(00)00214-9 [23] JIANG Y, YANG L, LIANG G T, LIU S J, GAO W Q, YANG Z D, WANG X W, LIN R Y, ZHU X B. The poisoning effect of PbO on CeO2-MoO3 /TiO2 catalyst for selective catalytic reduction of NO with NH3[J]. Mol Catal,2020,486:1−9. [24] THIRUPATHI B, SMIRNIOTIS P G. Effect of nickel as dopant in Mn/TiO2 catalysts for the low-temperature selective reduction of NO with NH3[J]. Catal Lett,2011,141:1399−1404. doi: 10.1007/s10562-011-0678-z [25] CHI G L, SHEN B X, YU R R, HE C, ZHANG X. Simultaneous removal of NO and HgO over Ce-Cu modified V2O5/TiO2 based commercial SCR catalysts[J]. J Hazard Mater,2017,330:83−92. doi: 10.1016/j.jhazmat.2017.02.013 [26] LIAN Z H, LIU F D, HE H, SHI X Y, MO J S, WU Z B. Manganese-niobium mixed oxide catalyst for the selective catalytic reduction of NOx with NH3 at low temperatures[J]. Chem Eng J,2014:390−398. [27] CAO F, XIANG J, SU S, WANG P Y, HU S, SUN L S. Ag modified Mn-Ce/γ-Al2O3 catalyst for selective catalytic reduction of NO with NH3 at low-temperature[J]. Fuel Process Technol,2015,135:66−72. doi: 10.1016/j.fuproc.2014.10.021