钙基吸附剂对氧化态汞的选择性吸附机理研究
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摘要
本文采用介孔SiO_2为载体,基于不同的CaO前驱物(水合氧化钙、硝酸钙以及醋酸钙)制备了三种钙基吸附剂(CaO-H-S、CaO-N-S和CaO-C-S),研究吸附剂表面对模拟烟气中HgCl_2的选择性吸附机理。吸附剂表征结果表明,醋酸钙为前驱物制得吸附剂(CaO-C-S)孔隙结构发达,活性物相(CaO)分散均匀,吸附剂表面碱性位点丰富,对HgCl_2的选择性吸附性能最优。采用密度泛函理论(DFT)方预测了HgCl_2在CaO表面存在四种不同吸附方式:单配位、双配位、三配位、以及桥式配位吸附,吸附作用依次增强。HgCl_2的程序升温脱附实验进一步证实了CaO-C-S表面存在以上四种HgCl_2吸附行为,三配位和单配位为CaO-C-S表面最主要的吸附构型,双配位吸附方式最少,而桥式配位作用最强。
In this paper, three types of calcium-based sorbents were synthesized using different CaO precursors, including hydrated calcium oxide(CaO-H-S), calcium nitrate tetrahydrate(CaO-N-S) and calcium acetate monohydrate(CaO-C-S). The adsorption mechanisms of HgCl_2 were investigated over those sorbent surfaces. Sorbent characterization results indicated CaO-C-S possessed the advanced porosity, homodisperse phase and abundant basic sites, which showed the optimal ability for HgCl_2 selective adsorption. Density functional theory(DFT) predictions reified four adsorptive manners of HgCl_2 on CaO surfaces: Monodentate < Tridendate < Bidentate < Bridging. The HgCl_2-TPD experiments further substantiated the existence of four HgCl_2 adsorption behaviors over CaO-AcS.HgCl_2 adsorption were prominently comprised of Tridentate and Monodentate configurations. The Bidentate manner was infrequent, while Bridging adsorption was the strongest interaction on CaO-AcS surfaces.
In this paper, three types of calcium-based sorbents were synthesized using different CaO precursors, including hydrated calcium oxide(CaO-H-S), calcium nitrate tetrahydrate(CaO-N-S) and calcium acetate monohydrate(CaO-C-S). The adsorption mechanisms of HgCl_2 were investigated over those sorbent surfaces. Sorbent characterization results indicated CaO-C-S possessed the advanced porosity, homodisperse phase and abundant basic sites, which showed the optimal ability for HgCl_2 selective adsorption. Density functional theory(DFT) predictions reified four adsorptive manners of HgCl_2 on CaO surfaces: Monodentate < Tridendate < Bidentate < Bridging. The HgCl_2-TPD experiments further substantiated the existence of four HgCl_2 adsorption behaviors over CaO-AcS.HgCl_2 adsorption were prominently comprised of Tridentate and Monodentate configurations. The Bidentate manner was infrequent, while Bridging adsorption was the strongest interaction on CaO-AcS surfaces.
引文
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[22]王晋刚.粉煤灰水热化合反应制备钙基烟气脱硫剂[D].天津:天津大学,2006WANG Jingang. Ca-based Absorbent Prepared by Hydrothermal Reaction with Fly Ash for Flue gas Desulfur-ization[D]. Tianjin:Tianjin University, 2006
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[26] Cornu D, Guesmi H, Krafft J M, et al. Lewis Acido-basic Interactions Between CO_2 and MgO Surface:DFT and DRIFT Approaches[J]. The Journal of Physical Chemistry C, 2012, 116(11):6645-6654
[27] YANG Yinju, LIU Jing, SHEN Fenghua, et al. Kinetic Study of Heterogeneous Mercury Oxidation by HCl on Fly Ash Surface in Coal-fired Flue Gas[J]. Combustion and Flame, 2016, 168:1-9
[28] Xue M, Liu S, Guo J, et al. Growth and Electronic Structure of Ag on Polar MgO(111)Films[J]. RSC Advances,2013, 3(41):18916-18922
[2] UNEP Chemicals Branch. Global Mercury Assessment2013:Sources, Emissions, Releases and Environmental Transport[EB/OL].[2017-06-06]. http://weclocs.unep.org/handle/20.500.11822/7984
[3]中国环境科学研究院,国电环境保护研究院.GB 13223-2011,火电厂大气污染物排放标准[S].北京:中国环境科学出版社,2011Chinese Research Academy of Environmental Sciences,National Institute of Environmental Protection. GB13223-2011, Emission Standards for Air Pollutants FromPower Plants[S]. Beijing:Chinese Environment Science Press, 2011
[4]朱纯,段钰锋,尹建军,等.卤化铵盐改性生物质稻壳焦的汞吸附特性[J].东南大学学报(自然科学版),2013, 43(1):99-104ZHU Chu, DUAN Yufeng, YIN Jianjun, et al. Mercury Adsorption by Rice Husk Char Sorbents Modified by Ammonium Halide[J]. Journal of Southeast University(Natural Science Edition), 2013, 43(1):99-104
[5] Moore C W, Castro M S. Investigation of Factors Affecting Gaseous Mercury Concentrations in Soils[J]. Science of the Total Environment, 2012, 419:136-143
[6]陈惠超,赵长遂,沈鹏.烟气中水蒸气对钙基吸收剂碳酸化的影响特性[J].化工学报,2013, 64(4):1364-1372CHEN Huichao, ZHAO Changsui, SHEN Peng. Effect of Steam in Flue Gas on CO_2 Capture for Calcium Based Sorbent[J]. CIESC Jorunal, 2013, 64(4):1364-1372
[7]张帅,肖睿,杨一超,等.钙基载氧体煤化学链燃烧脱硫试验研究[J].工程热物理学报,2012, 33(3):525-528ZHANG Shuai, XIAO Rui, YANG Yi-Chao, et al. Experimental Study of Desulfurization of Chemical-Loping Combustion of Coal With Calcium-based Oxygen Carrier[J]. Journal of Engineering Thermophysics, 2012, 33(3):525-528
[8] Ghorishi B, Gullett B K. Sorption of Mercury Species by Activated Carbons and Calcium-based Sorbents:Effect of Temperature, Mercury Concentration and Acid Gases[J].Waste Management&Research, 1998, 16(6):582-593
[9] Sasmaz E, Wilcox J. Mercury Species and SO_2 Adsorption on CaO(100)[J]. Journal of Physical Chemistry C,2008, 112(42):16484-16490
[10] Lu H, Reddy E P, Smirniotis P G. Calcium Oxide Based Sorbents for Capture of Carbon Dioxide at High Temperatures[J]. Industrial&Engineering Chemistry Research,2006, 45(11):3944-3949
[11]张明明,彭云湘,汪瑾,等.三元复合钙基材料CaOCa_3Al_2O_6-MgO的合成及其CO_2吸附性能[J].化工学报,2014, 65(1):227-236ZHANG Mingming, PENG Yunxiang, WANG Jin, et al. Preparation of Ternary Composite Ca-based Material CaO-Ca_3Al_2O_6-MgO for High-temperature CO_2 Capture[J]. CIESC Jorunal, 2014, 65(1):227-236
[12]佘敏,段钰锋,朱纯,等.改性生物质活性焦碳管吸附剂汞吸附性能实验研究[J].工程热物理学报,2015, 36(9):2060-2064SHE Min, DUAN Yufeng, ZHU Chu, et al. Experimental Study on Mercury Adsorption of Modified Biomass Activated Carbon for Sorbents Traps[J]. Journal of Engineering Thermophysics, 2015, 36(9):2060-2064
[13] Tang H J, Duan Y F, Zhu C, et al. A Novel Carbon Trap Sampling System for Coal-fired Flue Gas Mercury Measurement[J]. Journal of Southeast University(English Edition), 2015, 31(2):244-248
[14] Tang H J, Duan Y F, Zhu C, et al. Characteristics of a Biomass-based Sorbent Trap and Its Application to Coalfired Flue Gas Mercury Emission Monitoring[J]. International Journal of Coal Geology, 2017, 170:19-27
[15] Clark S J, Segall M D, Pickard C J, et al. First Principles Methods using Castep[J]. Zeitschrift für KristallographieCrystalline Materials, 2005, 220(5/6):567-570
[16] Perdew J P, Burke K, Ernzerhof M. Generalized Gradient Approximation Made Simple[J]. Physical review letters,1996, 77(18):3865
[17] Perdew J P, Burke K, Ernzerhof M. Perdew, Burke, and Ernzerhof Reply[J]. Physical Review Letters, 1998, 80(4):891
[18] Monkhorst H J, Pack J D. Special Points for Brillouinzone Integrations[J]. Physical review B, 1976, 13(12):5188
[19] Pfrommer B G, Cote M, Louie S G, et al. Relaxation of Crystals with the Quasi-Newton Method[J]. Journal of Computational Physics, 1997, 131(1):233-240
[20] Zintl E, Harder A, Dauth B. Lattice Structure of the Oxides, Sulfides, Selenides and Tellurides of Lithium, Sodium and Potassium[J]. Zeitschrift für Elektrochemie, 1934, 40:588
[21] Broqvist P, Gronbeck H, Panas I. Surface Properties of Alkaline Earth Metal Oxides[J]. Surface Science, 2004,554(2):262-271
[22]王晋刚.粉煤灰水热化合反应制备钙基烟气脱硫剂[D].天津:天津大学,2006WANG Jingang. Ca-based Absorbent Prepared by Hydrothermal Reaction with Fly Ash for Flue gas Desulfur-ization[D]. Tianjin:Tianjin University, 2006
[23] Hesse K F. Refinement of the Crystal Structure of Wollastonite-2M(parawollastonite)[J]. Zeitschrift für Kristallographie-Crystalline Materials, 1984, 168(1-4):93-98
[24] Shen C H, Liu R S, Lin J G, et al. Phase Stability Study of La_(1.2)Ca_(1.8)Mn_2O_7[J]. Materials Research Bulletin, 2001,36(5):1139-1148
[25] Menezes A O, Silva P S, Padrón Hernaandez E, et al.Tuning Surface Basic Properties of Nanocrystalline MgO by Controlling the Preparation Conditions[J]. Langmuir,2009, 26(5):3382-3387
[26] Cornu D, Guesmi H, Krafft J M, et al. Lewis Acido-basic Interactions Between CO_2 and MgO Surface:DFT and DRIFT Approaches[J]. The Journal of Physical Chemistry C, 2012, 116(11):6645-6654
[27] YANG Yinju, LIU Jing, SHEN Fenghua, et al. Kinetic Study of Heterogeneous Mercury Oxidation by HCl on Fly Ash Surface in Coal-fired Flue Gas[J]. Combustion and Flame, 2016, 168:1-9
[28] Xue M, Liu S, Guo J, et al. Growth and Electronic Structure of Ag on Polar MgO(111)Films[J]. RSC Advances,2013, 3(41):18916-18922
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