铈改性增强OMS-2汞氧化催化剂抗硫性能的机理研究

黄金金; 蔡良峰; 刘僖; 杨建平; 屈文麒; 李海龙

铈改性增强OMS-2汞氧化催化剂抗硫性能的机理研究

中南大学能源科学与工程学院, 湖南长沙 410083

基金项目:

国家自然科学基金 51776227

国家自然科学基金 51906260

详细信息

中图分类号: X511
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- 被引次数: 0
出版历程
- 收稿日期: 2020-09-11
- 修回日期: 2020-10-26
- 网络出版日期: 2021-01-23
- 刊出日期: 2020-12-10

Mechanism for the enhancement of the resistance of the OMS-2 mercury oxidation catalyst to sulfur by modifying with cerium

School of Energy Science and Engineering, Central South University, Changsha 410083, China

Funds:

the National Natural Science Foundation of China 51776227

the National Natural Science Foundation of China 51906260

More Information

Corresponding author: LI Hai-long, Tel:18670016725, E-mail:hailong_li@126.com

摘要

摘要: 针对氧化锰八面体分子筛(OMS-2)在催化氧化单质汞过程中抗硫性能差的问题，采用铈(Ce)对OMS-2催化剂进行改性提高其抗硫性。通过热力学分析、固定床实验、氮吸附、XRD、ICP和XPS等表征手段，研究了铈增强OMS-2抗硫能力的原因。结果表明，Ce改性得到的催化剂比表面积大、空隙结构丰富，可以在催化剂表面通过化学吸附吸附更多的Hg⁰；Ce改性得到的催化剂会造成Mn缺陷生成，提高电子迁移率，使得吸附氧(O_β)占比高，可提供更多的活性位点；OMS-2催化剂表面氧化的HgO可经不同浓度的SO₂还原为Hg⁰或者HgSO₄，但Ce改性得到的催化剂可使该部分还原产物迅速重新氧化成HgO，提高了表观Hg⁰氧化效率。该研究结果可为开发高性能抗硫汞氧化催化剂提供理论依据。
- 氧化汞 /
- SO₂ /
- 还原 /
- 热力学 /
- 燃煤烟气
Abstract: In view of the poor resistance of manganese oxide octahedral molecular sieve (OMS-2) catalyst to sulfur in the oxidation of elemental mercury, CeO₂ was used to modify the OMS-2 catalyst. The mechanism for the enhancement of the resistance of the OMS-2 catalyst to sulfur by modifying with CeO₂ was investigated, with the help of thermodynamic analysis, fixed-bed reaction test and various characterization methods like nitrogen sorption, XRD ICP and XPS. The results indicate: The OMS-2 catalyst modified by Ce has a large surface area and void-rich structure, which can adsorb more Hg⁰ through chemical adsorption; More Mn defects are formed on the OMS-2 catalyst through modifying with Ce, leading to an increase in the electron mobility, the proportion of adsorbed oxygen (O_β) species, and the density of catalytically active sites; The Ce-modified OMS-2 catalyst can quickly re-oxidize the reduced Hg⁰ or HgSO₄ species (facilely formed on the pristine OMS-2 catalyst surface in the presence of SO₂) to HgO, which can then improve the apparent Hg⁰ oxidation efficiency. The results should be helpful for the development of high-performance anti-thio catalysts for mercury oxidation.
- mercury oxide /
- SO₂ /
- reduction /
- thermodynamics /
- coal-fired flue gas

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图 1 SO₂对催化剂上Hg⁰氧化性能的影响

Figure 1 Influence of SO₂ on the catalyst performance in the oxidation of Hg⁰

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图 2 催化剂表征谱图

(a)XRD，(b)Mn 2p XPS能谱图，(c)Ce 3d XPS能谱图，(d)O 1s XPS能谱图

Figure 2 Characterization of the catalysts

(a): XRD patterns; (b): Mn 2p XPS spectra; (c): Ce 3d XPS spectra; (d): O 1s XPS spectra

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图 3 OMS-2催化剂的FT-IR光谱谱图

Figure 3 FT-IR spectra of OMS-2 catalyst

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图 4 Ce-OMS-2表面Hg⁰-程序升温脱附实验

Figure 4 TPD profiles of Hg⁰ for the Ce-OMS-2 catalyst

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图 5 OMS-2催化剂表面SO₂对HgO的还原

Figure 5 Reduction of HgO by SO₂ on the surface of OMS-2 catalyst

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图 6 Ce-OMS-2催化剂表面SO₂对HgO的还原

Figure 6 Reduction of HgO by SO₂ on the surface of Ce-OMS-2 catalyst

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图 7 无催化剂时SO₂对HgO的还原

Figure 7 Reduction of HgO by SO₂ without catalyst

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图 8 SO₂气氛下各平衡相含量随温度的变化关系

Figure 8 Equilibrium contents of various species in the presence of SO₂ at different temperatures Initial contents of HgO and SO₂ are set as 1 and those of other species as 0

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图 9 SO₂还原HgO的机理示意图

Figure 9 Mechanistic diagram of HgO reduction by SO₂

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表 1 实验条件

Table 1 Reaction test conditions

Test	Catalyst	Carrier gas	Temp. t/℃	Flow /(L·min^-1)
1	OMS-2	N₂，N₂+0.05%SO₂，N₂+0.1%SO₂，N₂+0.1%SO₂+4%O₂	150	1
2	Ce-OMS-2	N₂，N₂+0.05%SO₂，N₂+0.1%SO₂，N₂+0.1%SO₂+4%O₂	150	1
3	Ce-OMS-2^#1	N₂	100-700	0.5
	Ce-OMS-2^#2
4	OMS-2^*	N₂+0.05%SO₂	150	1
5	Ce-OMS-2^*	N₂+0.05%SO₂	150	1
6	10 mg HgO	N₂+0.05%SO₂	150	1
note:^“#1”, the catalyst was pretreated under N₂+4%O₂+Hg⁰ for 1 h; ^“#2”, the catalyst was pretreated under N₂+4%O₂+0.05%SO₂+Hg⁰ for 1 h; ^“*”, the catalyst pretreated under N₂+4%O₂+500 μg/m³ Hg⁰ for 7 d

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表 2 催化剂的比表面积和表面原子含量

Table 2 Surface area and surface atomic concentration of the catalysts

Catalyst	Surface area A/(m²·g^-1)	Surface atom concentration
		by ICP		by XPS
		K/Mn	Ce/Mn	Mn³⁺/Mn⁴⁺	Ce³⁺/Ce⁴⁺	O_α	O_β
OMS-2	173	0.10	-	1.07	-	79.6%	20.4%
Ce-OMS-2	390	0.038	0.35	1.10	0.24	68.2%	31.8%
note: O_α: lattice oxygen; O_β: surface adsorbed oxygen

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表 3 HgO在SO₂气氛下的初始工况

Table 3 Initial conditions of HgO under SO₂ atmosphere

Species	HgO	SO₂	O₂	SO₃	Hg	HgSO₄
Amount of substance /kmol	1	1	0	0	0	0

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参考文献(36)

[1]	王立刚, 彭苏萍, 陈昌和.燃煤飞灰对锅炉烟道气中Hg⁰的吸附特性[J].环境科学, 2003, 24(6): 59-62. WANG Li-gang, PENG Su-ping, CHEN Chang-he. The experimental study to Hg⁰ adsorption of fly ash in flue gas[J]. Environ Sci, 2003, 24(6): 59-62.
[2]	任建莉, 周劲松, 骆仲泱, 徐璋, 张雪梅.钙基类吸附剂脱除烟气中气态汞的试验研究[J].燃料化学学报, 2006, 34(5): 557-561. REN Jian-li, ZHOU Jin-song, LUO Zhong-yang, XU Zhang, ZHANG Xue-mei. Ca-based sorbents for mercury vapor removal from flue gas[J]. J Fuel Chem Technol, 2006, 34(5): 557-561.
[3]	ZHAO Y X, MICHAEL D M, EDWIN S O, JOHN H P, GRANT E D. Effects of sulfur dioxide and nitric oxide on mercury oxidation and reduction under homogeneous conditions[J]. J Air Waste Manage Assoc, 2012, 56(5): 628-635.
[4]	WANG F, WANG H M, ZHANG F, ZHU J W, TIAN G, LIU Y, MAO J X. SO₂/Hg removal from flue gas by dry FGD[J]. Int J Min Sci Technol, 2012, 22(1): 107-110.
[5]	WANG Y Y, SHEN B X, HE C, YUE S J, WANG F M. Simultaneous removal of NO and Hg⁰ from flue gas over Mn-Ce/Ti-PILCs[J]. Environ Sci Technol, 2015, 49(15): 9355-9363.
[6]	YANG W, LIU Y X, WANG Q, PAN J F. Removal of elemental mercury from flue gas using wheat straw chars modified by Mn-Ce mixed oxides with ultrasonic-assisted impregnation[J]. Chem Eng J, 2017, 326(15): 169-181.
[7]	XU H M, QU Z, ZONG X, QUAN F Q, MEI J, YAN N Q. Catalytic oxidation and adsorption of Hg⁰ over low-temperature NH₃-SCR LaMnO₃ perovskite oxide from flue gas[J]. Appl Catal B: Environ, 2016, 186(5): 30-40.
[8]	ATRIBAK I, BUENO L A, GARCIA G A, NAVARO P, FRIAS D, MONTES M. Catalytic activity for soot combustion of birnessite and cryptomelane[J]. Appl Catal B: Environ, 2010, 93(3/4): 267-273.
[9]	DING Y S, SHEN X F, SITHAMBARAM S, GOMEZ S, KUMAR R, CRISOSTOMO V M B, SUIB S L, AINDOW M. Synthesis and catalytic activity of cryptomelane-type manganese dioxide nanomaterials produced by a novel solvent-free method[J]. Chem Mater, 2005, 17(21): 5382-5389.
[10]	HUANG W M, SHI J L. Water-promoted low-concentration NO removal at room temperature by Mg-doped manganese oxides OMS-2[J]. Appl Catal A: Gen, 2015, 507(25): 65-74.
[11]	GANDHE A R, JEANETTE S, REBELLO J, FIGUEIREDO L, FERNANDES J B. Manganese oxide OMS-2 as an effective catalyst for total oxidation of ethyl acetate[J]. Appl Catal B: Environ, 2007, 72(1/2): 129-135.
[12]	ADJIMI S, GARCIA V J, DIAZ J A, RETAILLEAU L, GIL S, PERA T M, GUO Y, GIROIR F A. Highly efficient and stable Ru/K-OMS-2 catalyst for NO oxidation[J]. Appl Catal B: Environ, 2017, 219(15): 459-466.
[13]	HERNANDEZ W Y, CENTENO M A, SVETLANA I, PIERRE E, GAIGNEAUXE M, ODRIOZOLA J A. Cu-modified cryptomelane oxide as active catalyst for CO oxidation reactions[J]. Appl Catal B: Environ, 2012, 123(23): 27-35.
[14]	LI J F, YAN N Q, QU Z, QIAO S H, YANG S J, GUO Y F, LIU P, JIA J P. Catalytic oxidation of elemental mercury over the modified catalyst Mn/alpha-Al₂O₃ at Lower Temperatures[J]. Environ Sci Technol, 2010, 44(1): 426-431.
[15]	LIU X, JIANG S J, LI H L, YANG J P, YANG Z Q, ZHAO J X, PENG H Y, KAIMIN S. Elemental mercury oxidation over manganese oxide octahedral molecular sieve catalyst at low flue gas temperature[J]. Chem Eng J, 2019, 356(15): 142-150.
[16]	WU S J, KATAYAMA R, UDDIN M A, SASAOKA E, XIE Z M. Study on reactivity of HgO over activated carbon with HCl and SO₂ in the presence of moisture by temperature-programmed decomposition desorption mass spectrometry[J]. Energy Fuels, 2015, 29(10): 6598-6604.
[17]	李扬, 刘冰, 杨赫, 杨大伟, 胡浩权. MnO_x-TiO₂吸附剂对燃煤烟气中汞的脱除[J].燃料化学学报, 2020, 48(5): 513-524. LI Yang, LIU Bing, YANG He, YANG Da-wei, HU Hao-quan. Removal of elemental mercury(Hg⁰) from simulated flue gas over MnO_x-TiO₂ sorbents[J]. J Fuel Chem Technol, 2020, 48(5): 513-524.
[18]	WU S J, UDDIN M A, NAGANO S, MASAKI O, SASAOKA E. Fundamental study on decomposition characteristics of mercury compounds over solid powder by temperature-programmed decomposition desorption mass spectrometry[J]. Energy Fuels, 2011, 25(2): 144-153.
[19]	HE S, ZHOU J S, ZHU Y Q, LUO Z Y, NI M J, CEN K. Mercury oxidation over a vanadia-based selective catalytic reduction catalyst[J]. Energy Fuels, 2009, 23(1): 253-259.
[20]	赵莉, 何青松, 刘宇, 吴洋文, 陆强, 刘松涛, 董长青.湿法脱硫浆液中Hg²⁺的还原机制研究[J].燃料化学学报, 2017, 45(6): 755-760. ZHAO Li, HE Qing-song, LIU Yu, WU Yang-wen, LU Qiang, LIU Song-tao, DONG Chang-qing. Mechanism of Hg²⁺ reduction in wet flue gas desulfurization liquors[J]. J Fuel Chem Technol, 2017, 45(6): 755-760.
[21]	LI H L, WU C Y, LI Y, ZHANG J. CeO₂-TiO₂ catalysts for catalytic oxidation of elemental mercury in low-rank coal combustion flue gas[J]. Environ Sci Technol, 2011, 45(17): 7394-400.
[22]	WANG T, LIU J, YANG Y H, SUI Z F, ZHANG Y S, WANG J W, PAN W P. Catalytic conversion of mercury over Ce doped Mn/SAPO-34 catalyst: Sulphur tolerance and SO₂/SO₃ conversion[J]. J Hazard Mater, 2020, 381(5): 120986.
[23]	王艳坤. HSC Chemistry软件在高校化学科研中的应用[J].河南教育学院学报:自然科学版, 2013, 22(2): 32-34. WANG Yan-kun. Application of HSC chemistry software in university chemical scientific research[J]. J Henan Ins Edu Nat Sci Ed, 2013, 22(2): 32-34.
[24]	GRANITE E J, PENNLINE H W, HARGIS R A. Novel sorbents for mercury removal from flue gas[J]. Ind Eng Chem Res, 2000, 39(4): 1020-1029.
[25]	WU Z B, JIANG B Q, YUE L, ZHAO W R, GUAN B H. Experimental study on a low-temperature SCR catalyst based on MnO_x/TiO₂ prepared by sol-gel method[J]. J Hazard Mater, 2007, 145(3): 488-494.
[26]	LI H L, ZHU L, WANG J, LI L Q, SHIH K. Development of nano-sulfide sorbent for efficient removal of elemental mercury from coal combustion fuel gas[J]. Environ Sci Technol, 2016, 50(17): 9551-9557.
[27]	HOU J T, LI Y Z, MAO M Y, ZHAO X J, YUE Y Z. The effect of Ce ion substituted OMS-2 nanostructure in catalytic activity for benzene oxidation[J]. Nanoscale, 2014, 6(24): 15048-15058.
[28]	LIU C, CHEN L, LI J, MA L, ARANDIYAN H, DU Y, XU J, HAO J. Enhancement of activity and sulfur resistance of CeO₂ supported on TiO₂-SiO₂ for the selective catalytic reduction of NO by NH₃[J]. Environ Sci Technol, 2012, 46(11): 6182-6189.
[29]	WANG X Y, LAN Z X, ZHANG K, CHEN J J, JIANG L L, WANG R H. Structure activity relationships of AMn₂O₄ (A=Cu and Co) spinels in selective catalytic reduction of NO_x: Experimental and theoretical study[J]. J Chem Phys C, 2017, 121(6): 3339-3349.
[30]	KIVELSON, DANIEL. The determination of the potential constants of SO₂ from centrifugal distortion effects[J]. J Chem Phys, 1954, 22(5): 904-908.
[31]	王鹏鹰.铝基SCR催化剂催化氧化烟气中汞的实验与机理研究[D].武汉: 华中科技大学, 2014. WANG Peng-ying. A dissertation submitted in partial fulfllment of the requirements for the degree of doctor of philosophy in engineering[D]. Wuhan: Huazhong University of Science and Technology, 2014.
[32]	张旭楠. CeO₂改性SCR催化剂同时脱除烟气中Hg⁰和NO的实验研究[D].长沙: 湖南大学, 2015. ZHANG Xu-nan. The experimental study on the simultaneous removal of elemental mercury (Hg⁰) and NO from flue gas by CeO₂ modified SCR catalysts[D]. Changsha: Hunan University, 2015.
[33]	ZHUANG Y, JASON L, RICHARD L, MIKE H, JOHN P. Impacts of acid gases on mercury oxidation across SCR catalyst[J]. Fuel Process Technol, 2007, 88(10): 929-934.
[34]	LAUDAL D L, THOMPSON J S, PAVLISH J H, BRICKET L, CHU P, SRIVASTAVA R K, LEE C W, KILGROE J. Mercury speciation at power plants using SCR and SNCR control technologies[J]. Electron Manager, 2012, 53(1): 16-22.
[35]	SUI Z F, ZHANG Y S, LI W H, WILLIAM O, CAO Y, PAN W P. Partitioning effect of mercury content and speciation in gypsum slurry as a function of time[J]. J Therm Anal Calorim, 2015, 119(3): 1611-1618.
[36]	ZHANG Y S, ZHAO L L, GUO R T, WANG J W, CAO Y, WILLIAM O, PAN W P. Influences of NO on mercury adsorption characteristics for HBr modified fly ash[J]. Int J Coal Geol, 2017, 170(1): 77-83.