New insights into mercury removal mechanism on CeO<sub>2</sub>-based catalysts: A first-principles study

doi:10.1007/s11783-018-1007-1

Front. Environ. Sci. Eng.

2018, Vol. 12

Issue (2) : 11 https://doi.org/10.1007/s11783-018-1007-1

research-article

New insights into mercury removal mechanism on CeO₂-based catalysts: A first-principles study

Ling Li¹, Yu He²(

), Xia Lu³

¹. Forestry College, Guizhou University, Guiyang 550025, China
². Key Laboratory of High-Temperature and High-Pressure Study of the Earth’s Interior, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China
³. State Key Laboratory of Organic-Inorganic Composites, Beijing Advanced Innovation Center for Soft Matter Science and Engineering, College of Energy, Beijing University of Chemical Engineering, Beijing 100029, China

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Abstract

Hg⁰ is chemically adsorbed and fully oxidized by surface oxygen on CeO₂.

HCl promotes the desorption of oxidized Hg on CeO₂.

Surface oxygen is consumed by the H provided by HCl.

Desorption of oxidized Hg is a rate-determining step.

Maintenance of sufficient active surface oxygen is another rate-determining step.

First-principles calculations were performed to investigate the mechanism of Hg⁰ adsorption and oxidation on CeO₂(111). Surface oxygen activated by the reduction of Ce⁴⁺ to Ce³⁺ was vital to Hg⁰ adsorption and oxidation processes. Hg⁰ was fully oxidized by the surface lattice oxygen on CeO₂(111), without using any other oxidizing agents. HCl could dissociate and react with the Hg adatom on CeO₂(111) to form adsorbed Hg–Cl or Cl–Hg–Cl groups, which promoted the desorption of oxidized Hg and prevented CeO₂ catalyst deactivation. In contrast, O–H and H–O–H groups formed during HCl adsorption consumed the active surface oxygen and prohibited Hg oxidation. The consumed surface oxygen was replenished by adding O₂ into the flue gas. We proposed that oxidized Hg desorption and maintenance of sufficient active surface oxygen were the rate-determining steps of Hg⁰ removal on CeO₂-based catalysts. We believe that our thorough understanding and new insights into the mechanism of the Hg⁰ removal process will help provide guidelines for developing novel CeO₂-based catalysts and enhance the Hg⁰ removal efficiency.

Keywords Elemental mercury removal Surface adsorption Ceria First-principles calculations

Corresponding Author(s): Yu He

Issue Date: 07 November 2017

Cite this article:

Ling Li,Yu He,Xia Lu. New insights into mercury removal mechanism on CeO₂-based catalysts: A first-principles study[J]. Front. Environ. Sci. Eng., 2018, 12(2): 11.

URL:

https://academic.hep.com.cn/fese/EN/10.1007/s11783-018-1007-1
https://academic.hep.com.cn/fese/EN/Y2018/V12/I2/11

Fig.1 CeO₂(111)-p(2 × 2) 9-layer slab: (a) side and (b) top views, in which yellow and red spheres represent Ce and O atoms, respectively. Cet, Ceb, Ob, Ot, and h correspond to active sites at Ce-top, Ce-bridge, O-top, O-bridge and O hollow positions

Tab.1 Adsorption energies (E_ads) and equilibrium distances of a Hg adatom on the CeO₂(111)

Fig.2 Most stable configuration of Hg-adsorbed CeO₂(111): (a) top and (b) side views. Gary, yellow, and red spheres represent Hg, Ce, and O atoms, respectively. Active sites Ce1, Ce2, O1, O2, O3, and O4 are labeled

Fig.3 Charge density difference for (a) Hg adsorption at the O-hollow site and (b) bare CeO₂(111). Red and blue colors represent charge accumulation and depletion, accordingly

Tab.2 Calculated Bader charges of Hg, Ce, and O in various compounds and configurations

Fig.4 Side views of the optimized configurations of two HCl on the Hg-adsorbed CeO₂(111): (a) O1O2-top, (b) O3O4-top, (c) O3-top, (d) O4-top, (e) Ce1Ce2-top, (f) CeHg-top

Tab.3 Adsorption energies (E_ads) of two HCl molecules on Hg-adsorbed CeO₂(111), and the calculated Bader charges of Hg, H, Cl, and O (bonded with H) in various compounds and configurations

Fig.5 Charge density difference for two HCl adsorptions on Hg-adsorbed CeO₂(111): (a) O1O2-top, (b) O3O4-top, (c) O3-top, (d) O4-top. The isosurfaces were calculated at 0.05 bohr⁻³

1	Pavlish J H, Sondreal E A, Mann M D, Olson E S, Galbreath K C, Laudal D L, Benson S A. Status review of mercury control options for coal-fired power plants. Fuel Processing Technology, 2003, 82(2-3): 89–165 https://doi.org/10.1016/S0378-3820(03)00059-6
2	Mergler D, Anderson H A, Chan L H, Mahaffey K R, Murray M, Sakamoto M, Stern A H. Methylmercury exposure and health effects in humans: A worldwide concern. Ambio, 2007, 36(1): 3–11 https://doi.org/10.1579/0044-7447(2007)36[3:MEAHEI]2.0.CO;2 pmid: 17408186
3	Wu Q, Wang S, Li G, Liang S, Lin C J, Wang Y, Cai S, Liu K, Hao J. Temporal trend and spatial distribution of speciated atmospheric mercury emissions in China during 1978–2014. Environmental Science & Technology, 2016, 50(24): 13428–13435 https://doi.org/10.1021/acs.est.6b04308 pmid: 27993067
4	Presto A A, Granite E J. Survey of catalysts for oxidation of mercury in flue gas. Environmental Science & Technology, 2006, 40(18): 5601–5609 https://doi.org/10.1021/es060504i pmid: 17007115
5	Galbreath K C, Zygarlicke C J. Mercury speciation in coal combustion and gasification flue gases. Environmental Science & Technology, 1996, 30(8): 2421–2426 https://doi.org/10.1021/es950935t
6	Wilcox J, Rupp E, Ying S C, Lim D H, Negreira A S, Kirchofer A, Feng F, Lee K. Mercury adsorption and oxidation in coal combustion and gasification processes. International Journal of Coal Geology, 2012, 90–91: 4–20 https://doi.org/10.1016/j.coal.2011.12.003
7	Monnell J D, Vidic R D, Gang D, Karash A, Granite E J. Recent Advances in Trace Metal Capture Using Micro and Nano-Scale Sorbents. In: Proceedings of the 23rd Pittsburgh Coal Conference. Pittsburgh, PA: University of Pittsburgh, 2006
8	Granite E J, Pennline H W, Hargis R A. Novel sorbents for mercury removal from flue gas. Industrial & Engineering Chemistry Research, 2000, 39(4): 1020–1029 https://doi.org/10.1021/ie990758v
9	Hua X Y, Zhou J S, Li Q, Luo Z Y, Cen K F. Gas-phase elemental mercury removal by CeO2 impregnated activated coke. Energy & Fuels, 2010, 24(10): 5426–5431 https://doi.org/10.1021/ef100554t
10	Li H, Wu C Y, Li Y, Zhang J. CeO2-TiO2 catalysts for catalytic oxidation of elemental mercury in low-rank coal combustion flue gas. Environmental Science & Technology, 2011, 45(17): 7394–7400 https://doi.org/10.1021/es2007808 pmid: 21770402
11	Zhou J, Hou W, Qi P, Gao X, Luo Z, Cen K. CeO2-TiO2 sorbents for the removal of elemental mercury from syngas. Environmental Science & Technology, 2013, 47(17): 10056–10062 https://doi.org/10.1021/es401681y pmid: 23931010
12	Chang H, Wu Q, Zhang T, Li M, Sun X, Li J, Duan L, Hao J. Design strategies for CeO2-MoO3 catalysts for DeNOx and Hg0 oxidation in the presence of HCl: The significance of the surface acid-base properties. Environmental Science & Technology, 2015, 49(20): 12388–12394 https://doi.org/10.1021/acs.est.5b02520 pmid: 26421943
13	Li H, Wu S, Wu C Y, Wang J, Li L, Shih K. SCR atmosphere induced reduction of oxidized mercury over CuO-CeO2/TiO2 catalyst. Environmental Science & Technology, 2015, 49(12): 7373–7379 https://doi.org/10.1021/acs.est.5b01104 pmid: 25961487
14	Wang Y, Chang H, Shi C, Duan L, Li J, Zhang G, Guo L, You Y. Novel Fe-Ce-O mixed metal oxides catalyst prepared by hydrothermal method for Hg0 oxidation in the presence of NH3. Catalysis Communications, 2017, 100: 210–213 https://doi.org/10.1016/j.catcom.2017.06.053
15	Reddy B M, Khan A, Yamada Y, Kobayashi T, Loridant S, Volta J C. Structural characterization of CeO2-MO2 (M= Si4+, Ti4+, and Zr4+) mixed oxides by Raman spectroscopy, X-ray photoelectron spectroscopy, and other techniques. Journal of Physical Chemistry B, 2003, 107(41): 5162–5167 https://doi.org/10.1021/jp0344601
16	Bera P, Patil K C, Jayaram V, Subbanna G N, Hegde M S. Ionic dispersion of Pt and Pd on CeO2 by combustion method: Effect of metal-ceria interaction on catalytic activities for NO reduction and CO and hydrocarbon oxidation. Journal of Catalysis, 2000, 196(2): 293–301 https://doi.org/10.1006/jcat.2000.3048
17	Roy S, Marimuthu A, Hegde M S, Madras G. High rates of NO and N2O reduction by CO, CO and hydrocarbon oxidation by O2 over nano crystalline Ce0.98Pd0.02O2-d: Catalytic and kinetic studies. Applied Catalysis B: Environmental, 2007, 71(1-2): 23–31 https://doi.org/10.1016/j.apcatb.2006.08.005
18	Cui L, Tang Y, Zhang H, Hector L G Jr, Ouyang C, Shi S, Li H, Chen L. First-principles investigation of transition metal atom M (M= Cu, Ag, Au) adsorption on CeO2(110). Physical Chemistry Chemical Physics, 2012, 14(6): 1923–1933 https://doi.org/10.1039/c2cp22720g pmid: 22231441
19	Lim D H, Aboud S, Wilcox J. Investigation of adsorption behavior of mercury on Au(111) from first principles. Environmental Science & Technology, 2012, 46(13): 7260–7266 https://doi.org/10.1021/es300046d pmid: 22631210
20	Lim D H, Wilcox J. Heterogeneous mercury oxidation on au(111) from first principles. Environmental Science & Technology, 2013, 47(15): 8515–8522 https://doi.org/10.1021/es400876e pmid: 23805868
21	Jung J E, Geatches D, Lee K, Aboud S, Brown G E Jr, Wilcox J. First-principles investigation of mercury adsorption on the a-Fe2O3 surface. Journal of Physical Chemistry C, 2015, 119(47): 26512–26518 https://doi.org/10.1021/acs.jpcc.5b07827
22	Zhang B, Liu J, Zheng C, Chang M. Theoretical study of mercury species adsorption mechanism on MnO2(110) surface. Chemical Engineering Journal, 2014, 256(256): 93–100 https://doi.org/10.1016/j.cej.2014.07.008
23	Zhang B, Liu J, Shen F. Heterogeneous mercury oxidation by HCl over CeO2 catalyst: density functional theory study. Journal of Physical Chemistry C, 2015, 119(27): 15047–15055 https://doi.org/10.1021/acs.jpcc.5b00645
24	Fabris S, Gironcol S D, Baroni S, Vicario G, Balducci G. Taming multiple valency with density functionals: A case study of defective ceria. Physical Review B: Condensed Matter and Materials Physics, 2005, 71(4): 041102 https://doi.org/10.1103/PhysRevB.71.041102
25	Da Silva J L F, Ganduglia-Pirovano M V, Sauer J, Bayer V, Kresse G. Hybrid functionals applied to rare-earth oxides: The example of ceria. Physical Review B: Condensed Matter and Materials Physics, 2007, 75(4): 045121 https://doi.org/10.1103/PhysRevB.75.045121
26	Loschen C, Carrasco J, Neyman K M, Illas F.First-principles LDA+ U and GGA+ U study of cerium oxides: Dependence on the effective U parameter. Physical Review B: Condensed Matter and Materials Physics, 2007, 75(3): 035115 https://doi.org/10.1103/PhysRevB.75.035115
27	Kresse G, Hafner J. Ab initio molecular dynamics for liquid metals. Physical Review B: Condensed Matter and Materials Physics, 1993, 47(1): 558–561 https://doi.org/10.1103/PhysRevB.47.558 pmid: 10004490
28	Kresse G, Furthmüller J. Efficient iterative schemes for ab initio total-energy calculations using a plane-wave basis set. Physical Review B: Condensed Matter and Materials Physics, 1996, 54(16): 11169–11186 https://doi.org/10.1103/PhysRevB.54.11169 pmid: 9984901
29	Kresse G, Furthmüller J. Efficiency of ab-initio total energy calculations for metals and semiconductors using a plane-wave basis set. Computational Materials Science, 1996, 6(1): 15–50 https://doi.org/10.1016/0927-0256(96)00008-0
30	Blöchl P E. Projector augmented-wave method. Physical Review B: Condensed Matter and Materials Physics, 1994, 50(24): 17953–17979 https://doi.org/10.1103/PhysRevB.50.17953 pmid: 9976227
31	Perdew J P, Burke K, Ernzerhof M. Generalized gradient approximation made simple. Physical Review Letters, 1996, 77(18): 3865–3868 https://doi.org/10.1103/PhysRevLett.77.3865 pmid: 10062328
32	Perdew J P, Burke K, Ernzerhof M. Generalized gradient approximation made simple. Physical Review Letters, 1997, 78(7): 1396 https://doi.org/10.1103/PhysRevLett.78.1396
33	Zhang C, Michaelides A, King D A, Jenkins S. Oxygen vacancy clusters on ceria: Decisive role of cerium f electrons. Physical Review B: Condensed Matter, 2009, 79(7): 075433 https://doi.org/10.1103/PhysRevB.79.075433
34	Fabris S, de Gironcoli S, Baroni S, Vicario G, Balducci G. Taming multiple valency with density functionals: A case study of defective ceria. Physical Review B: Condensed Matter and Materials Physics, 2005, 72(23): 237102 https://doi.org/10.1103/PhysRevB.72.237102
35	Tang W, Sanville E, Henkelman G. A grid-based Bader analysis algorithm without lattice bias. Journal of Physics Condensed Matter, 2009, 21(8): 084204 https://doi.org/10.1088/0953-8984/21/8/084204 pmid: 21817356
36	Sanville E, Kenny S D, Smith R, Henkelman G. Improved grid-based algorithm for Bader charge allocation. Journal of Computational Chemistry, 2007, 28(5): 899–908 https://doi.org/10.1002/jcc.20575 pmid: 17238168

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