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材料导报  2020, Vol. 34 Issue (3): 3044-3055    https://doi.org/10.11896/cldb.19020144
  材料与可持续发展(三)—环境友好材料与环境修复材料 |
尖晶石型催化剂的制备及在气态污染物净化中的应用综述
朱文娟1,高凤雨1,2,唐晓龙1,2,,易红宏1,2,于庆君1,2,赵顺征1,2
1 北京科技大学能源与环境工程学院,北京 100083
2 工业典型污染物资源化处理北京市重点实验室,北京 100083
Spinel Catalysts: Preparation Technology and Applications in Catalytic Purification of Gaseous Pollutants
ZHU Wenjuan1,GAO Fengyu1,2,TANG Xiaolong1,2,,YI Honghong1,2,YU Qingjun1,2,ZHAO Shunzheng1,2
1 School of Energy and Environmental Engineering,University of Science and Technology Beijing,Beijing 100083,China
2 Beijing Key Laboratory of Resource-oriented Treatment of Industrial Pollutants,Beijing 100083,China
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摘要 催化净化法是气态污染物净化的主要技术之一,在改善和优化人类的生存环境质量方面发挥了至关重要的作用。随着科研人员不断深入的研究,开发高比表面积、高效率、短反应物/产物扩散途径以及低能耗的催化材料是目前催化技术领域的研究重点。按催化材料成分分类,一般催化剂可分为过渡金属催化剂、金属氧化物催化剂、硫化物催化剂、固体酸催化剂等。传统金属氧化物催化剂受本身固有结构、活性氧物种及暴露活性位点较少等物理化学性质的限制,难以突破可调控性较差、催化效率较低的瓶颈。研究表明,由特殊的四面体和八面体结构相间组成的尖晶石型金属氧化物因具备结构、组分、物相、价态、形貌和缺陷的可调控性,表现出优异的超导性、发光性、催化活性等理化特性,在介电、磁性、发光、催化等功能材料应用领域中占据重要地位,被视为极具研究与应用潜力的一种高效气态污染物的新型催化净化材料。在催化剂制备合成方法中,沉淀法、水热法为常见的制备方法。然而,传统合成方法已经不能满足人们对不同形貌、构型、多组分复合催化剂的制备需求。为制备可调控性强、物理化学性质优异的尖晶石型催化剂,导晶沉淀、微波辅助水热、自组装法等新型复合制备方法受到人们的广泛关注。Mn、Co、Fe、Cr等尖晶石型催化剂被应用于气态污染物的脱除,其中Mn、Co尖晶石型催化剂因自身价态多变、氧化还原能力强而具有较高的催化去除效果及稳定性,从而被人们广泛研究。本文归纳了尖晶石型催化剂的研究进展,分别对尖晶石型催化剂的空间结构特性、典型制备方法的合成机制等进行介绍,重点分析其在气态污染物催化净化方面的发展方向并展望其前景,并对其未来的理论和应用研究给出了建议。
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朱文娟
高凤雨
唐晓龙
易红宏
于庆君
赵顺征
关键词:  尖晶石型催化剂  空间结构  合成机制  催化净化  气态污染物    
Abstract: Catalytic purification is one of the main technologies for the purification of gaseous pollutants, which plays an important role in improving and optimizing the quality of human living environment. With the continuous in-depth research of scientific researchers, the development of catalytic materials with high specific surface area, high efficiency, short reactants/product diffusion path and low energy consumption is the key point of current catalytic research.
According to the composition of catalytic materials, general catalysts can be divided into transition metal catalyst, metal oxide catalyst, sulfide catalyst, solid acid catalyst, etc. Traditional metal oxide catalysts are limited by physical and chemical properties such as inherent structure, species of reactive oxygen and less active sites exposed, it is difficult to break through the bottleneck of poor controllability and low catalytic efficiency. Research has shown that spinel metal oxide which made up of special tetrahedral and octahedral structure and composition showing excellent physical and chemical properties such as superconductivity, luminance, catalytic activity due to their controllability of structure, component, phase, valence state, morphology and defects. It occupies an important position in the application fields of dielectric, magnetic, luminescent, catalytic and other functional materials, and is regarded as a new type of highly efficient catalytic purification material for gaseous pollutants with great research and application potential.
Precipitation and hydrothermal methods are the common preparation and synthesis methods for catalyst synthesis. While the traditional synthesis methods are no longer meet the preparation needs of composite catalysts with different morphologies, configurations and multi-component. In order to prepare spinel type catalyst with strong controllability and excellent physicochemical properties, new composite preparation methods such as crystal conducting precipitation, microwave-assisted hydrothermal and self-assembly have attracted extensive attention. Mn, Co, Fe, Cr and other spinel type catalysts have been applied in the removal of gaseous pollutants, among which Mn and Co spinel type catalysts were being widely studied for their high catalytic removal efficiency and stability due to their variable valence and strong redox ability.
This paper summarizes the research progress of spinel catalyst, the structure characteristics of spinel type catalyst and the synthesis mechanism of typical preparation methods are introduced separately, and the development direction of catalytic purification of gaseous pollutants and its prospects are emphatically analyzed. Suggestions for its future theoretical and applied research are given.
Key words:  spinel catalyst    spatial structure    synthesis mechanism    catalytic purification    gaseous pollutant
                    发布日期:  2020-01-03
ZTFLH:  X511  
基金资助: 国家自然科学基金(21806009);中国博士后基金(2018M631344)
通讯作者:  txiaolong@126.com   
作者简介:  朱文娟,2018年6月毕业于山东理工大学,获得本科学位。现为北京科技大学能源与环境工程学院研究生,在唐晓龙教授的指导下进行研究。目前主要研究领域为Mn基特殊构型催化剂低温脱硝;唐晓龙,教授/博士研究生导师,教育部新世纪优秀人才。现任北京科技大学能源与环境工程学院副院长,“大气污染控制与资源化”学术梯队负责人。同时兼任中国工程教育认证协会环境类分委会委员、中国有色金属学会环境保护学术委员会委员等。2006年于北京理工大学(清华联合培养)获博士学位,长期以来主要从事烟气脱硫脱硝技术、工业废气资源化、环境功能材料研究与开发等工作。近年来先后主持了国家自然科学基金、国家863计划重点项目子课题、北京市科委“首都蓝天行动”专项课题、教育部博士点基金等10余项研究工作。在国内外学术刊物上发表学术论文240余篇,其中SCI检索91篇;出版专著1部,参编论著3部;申请发明专利50余项,已授权22项;荣获省部级科技奖5项,2013年教育部新世纪优秀人才、2015年北京科技大学五四奖章等荣誉奖项。
引用本文:    
朱文娟,高凤雨,唐晓龙,易红宏,于庆君,赵顺征. 尖晶石型催化剂的制备及在气态污染物净化中的应用综述[J]. 材料导报, 2020, 34(3): 3044-3055.
ZHU Wenjuan,GAO Fengyu,TANG Xiaolong,YI Honghong,YU Qingjun,ZHAO Shunzheng. Spinel Catalysts: Preparation Technology and Applications in Catalytic Purification of Gaseous Pollutants. Materials Reports, 2020, 34(3): 3044-3055.
链接本文:  
http://www.mater-rep.com/CN/10.11896/cldb.19020144  或          http://www.mater-rep.com/CN/Y2020/V34/I3/3044
1 Liu L L, Wang J, Hou Y, et al. Small, 2016, 12(5), 602.
2 Peng S J, Li L L, Hu Y X, et al.ACS Nano, 2015, 9(2),1945.
3 Liu Y, Zhang N, Yu C, et al.Nano Letters, 2016, 16(5), 3321.
4 Su H, Xu Y F, Shen S Y, et al.Journal of Energy Chemistry, 2018, 27(6), 1637.
5 Shin H, Kim H I, Chung D Y, et al.American Chemical Society, 2016, (6), 3914.
6 Wang H, Liu R P, Li Y T, et al.Joule, 2018, 2(2), 337.
7 Zhu H Y, Zhang S, Huang Y X, et al. Nano Letters, 2013, 13(6), 2947.
8 Abbas S A, Kim S H, Iqbal M I, et al. Scientific Reports, 2018, 8(1), 2986.
9 Kashyap V, Kurungot S.ACS Catalysis, 2018, 8(4), 3715.
10 Meng M L, Li J, Zeng Z Y, et al.Journal of Catalysis, 2016, 343,157.
11 Theofanidis S A, Galvita V V, Poelman H, et al. ACS Catalysis, 2018, 8(7), 5983.
12 Zhang L, Wang X G, Chen C J, et al.RSC Advances, 2017, 7(53), 33143.
13 Xing Y, Zhao C X, Jia G P, et al.Journal of Nanoparticle Research, 2018, 20(7),202.
14 Li X D, Huang Y L, Zhang Q, et al. Energy Conversion and Management, 2019, 179,166.
15 Nematollahi B, Rezaei M, Amini E, et al.International Journal of Hydrogen Energy, 2018, 43(2), 772.
16 Brollo M E F, López-Ruiz R, Muraca D, et al.Scientific Reports, 2014, 4(6839), 1.
17 Cui X J, Belo S, Krüger D, et al. Biomaterials, 2014, 35(22),5840.
18 He Q H, Zhang Z X, Xiong J W, et al. Optical Materials, 2008, 31(2), 380.
19 Karimi B, Mansouri F, Vali H. Green Chemistry, 2014, 16(5), 2587.
20 Kassaee M Z, Masrouri H, Movahedi F. Applied Catalysis A: General, 2011, 395(1), 28.
21 Feng J T, Hou Y H, Wang X Y, et al. Journal of Alloys and Compounds, 2016, 681,157.
22 Sharma R, Bansal S, Singhal S. RSC Advances, 2015, 5(8), 6006.
23 Pourzare K, Farhadi S, Mansourpanah Y. Applied Organometallic Chemistry, 2018, 32(5), 1.
24 Qiu M Y, Zhan S H, Yu H B, et al. Nanoscale, 2015, 7(6), 2568.
25 Hosseini S A, Niaei A, Salari D, et al. Ceramics International, 2012, 38(2), 1655.
26 Xie X W, Li Y, Liu Z Q, et al. Nature, 2009, 458,746.
27 Kaczmarczyk J, Zasada F, Janas J, et al. ACS Catalysis, 2016, 6(2), 1235.
28 Bai L,Wyrwalski F,Lamonier J F,et al. Applied Catalysis B:Environmental,2013, 138,381.
29 Lin J, Wang A, Qiao B, et al. Journal of the American Chemical Society, 2013, 135(41),15314.
30 Kim D C, Ihm S K. Environmental Science & Technology, 2001, 35(1), 222.
31 Fino D, Russo N, Saracco G, et al. Catalysis Today, 2006, 117(4), 559.
32 Seko A, Yuge K, Kuwabara A, et al. Physical Review B,2006, 73, 184117-1.
33 Goodenough J B, Loeb A L. Physical Review,1955, 98(2), 391.
34 Grimes R W, Anderson A B, Heuer A H. Journal of the American Chemical Society, 1989, 111(1), 1.
35 Hill R J, Craig J R, Gibbs G V. Physics and Chemistry of Minerals, 1979, 4(4), 317.
36 Sickafus K, Wills J, Grimes W N. Journal of the American Chemical So-ciety,1999, 82(12), 3279.
37 Chen X, Lei K X, Sun H M, et al. Energy Storage Science and Technology, 2017, 6(5), 905 (in Chinese).
陈祥, 雷凯翔, 孙洪明, 等.储能科学与技术,2017, 6(5),905.
38 Strens G J R. Journal of molecular structure, Cambridge University Press,USA,1973.
39 Yang S J, Xiong S C, Liao Y, et al. Environmental Science & Technology, 2014, 48(17), 10354.
40 Hua W J, Li D P, Yang Y, et al. Journal of Catalysis, 2018, 357,108.
41 Zhou L, Zhao D Y, Lou X W. Advanced Materials, 2012, 24(6), 745.
42 Pudukudy M, Yaakob Z. Chemical Engineering Journal, 2015, 262,1009.
43 Vankudoth K, Gutta N, Velisoju V K, et al. Catalysis Science & Techno-logy,2017,7(15), 3399.
44 Zarei M, Meshkani F, Rezaei M. Advanced Powder Technology, 2016, 27(5), 1963.
45 Adrian Marberger, Martin Elsener, Davide Ferri, et al. ACS Applied Materials & Interfaces, 2015, 5(7), 4180.
46 Liu P, He H P, Wei G L, et al. Applied Catalysis B:Environmental, 2016, 182,476.
47 Alibouri M, Ghoreishi S M, Aghabozorg H R. Industrial & Engineering Chemistry Research, 2009, 48(9), 4283.
48 Hao W, Yan W, Li H, et al. Energy Fuels, 2012, 26(11), 6518.
49 Michael M Forde, Lokesh Kesavan, Saiman M I, et al. ACS Nano, 2014, 8(1), 957.
50 Panagiotou G D, Petsi T, Bourikas K, et al. The Journal of Physical Chemistry C, 2010, 114(27), 11868.
51 Ren X R, He Q, Dong Y R, et al. Energy & Fuels, 2014, 28(7), 4746.
52 Hosseini S A, Niaei A, Salari D, et al. Ceramics International, 2012, 38(2), 1655.
53 Qiao J S, Wang N, Wang Z H, et al. Catalysis Communications, 2015, 72,111.
54 Lin Q, He Y, Lin J P, et al. Journal of Magnetism and Magnetic Mate-rials, 2019, 469,89.
55 Liu Y, Yao W Y, Cao X L, et al. Applied Catalysis B: Environmental, 2014, 160-161,684.
56 Li Q, Li G S, Fu C C, et al. ACS Applied Materials & Interfaces, 2014, 6(13), 10330.
57 Dai X X, Jiang W Y, Wang W L, et al. Chinese Journal of Catalysis, 2018, 39(4), 728.
58 Gao G, Shi J W, Fan Z, et al. Chemical Engineering, 2017, 325, 91.
59 Hossain M Z, Chowdhury M B I, Jhawar A K, et al. Biomass and Bioe-nergy, 2017, 107,39.
60 Kashyap V, Kurungot S. ACS Catalysis, 2018, 8(4), 3715.
61 Stingaciu M,Andersen H L,Granados-Miralles C, et al. CrystEngComm, 2017, 19(28), 3986.
62 Yen H X, Rohan R, Chiou C Y, et al. Electrochimica Acta, 2017, 253, 227.
63 Han L, Yu X Y. Advanced Materials, 2016, 28,4601.
64 Hu M, Furukawa S H, Ohtani R, et al. Angewandte Chemie International Edition, 2012, 51(4), 984.
65 Pan A, Wu H B, Yu L, et al. Angewandte Chemie International Edition, 2013, 52(8), 2226.
66 Qiu M Y, Zhan S H, Yu H B, et al. Catalysis Communications, 2015, 62,107.
67 Shen L F, Yu L, Wu H B, et al. Nature Communications, 2015, 6(6694),1.
68 Wang B, Wu H B, Zhang L, et al. Angewandte Chemie International Edition, 2013, 52(15), 4165.
69 Wang Z Y, Wang Z C, Wu H B, et al. Scientific Reports, 2013, 3(1391), 1.
70 Yu L, Wu H B, Lou X W D. Accounts of Chemical Research, 2017, 50(2), 293.
71 Zhao Y K, Zhou X C, Ding Y, et al. Journal of Catalysis, 2016, 338,30.
72 Jadhav H S, Kalubarme R S, Jadhav A H,et al. Journal of Alloys and Compounds, 2016, 666,476.
73 Cheng F, Shen J, Peng B, et al. Nature Chemistry, 2011, 3(1), 79.
74 Li C, Han X P, Cheng F Y, et al. Nature Communications, 2015, 6(7345), 1.
75 Shi L, Tao K, Kawabata T, et al. ACS Catalysis, 2011, 1(10),1225.
76 Qiu G H, Dharmarathna S, Zhang Y S, et al. The Journal of Physical Chemistry C, 2012, 116(1), 468.
77 Shi S J, Wang T, Cao M, et al. ACS Applied Materials & Interfaces, 2016, 8(18), 11476.
78 Tan G Q, Zhang L L, Ren H J, et al. ACS Applied Materials & Interfaces, 2013, 5(11), 5186.
75 Shi L, Tao K, Kawabata T, et al. ACS Catalysis, 2011, 1(10), 1225.
76 Qiu G H, Dharmarathna S, Zhang Y S, et al. The Journal of Physical Chemistry C, 2012, 116(1), 468.
77 Shi S J, Wang T, Cao M, et al. ACS Applied Materials & Interfaces, 2016, 8(18), 11476.
78 Tan G Q, Zhang L L, Ren H J, et al. ACS Applied Materials & Interfaces, 2013, 5(11), 5186.
79 Qiu G H, Huang H, Genuino H, et al. The Journal of Physical Chemistry C, 2011, 115(40), 19626.
80 Zhang L, Shi L Y, Huang L, et al. ACS Catalysis, 2014, 4(6), 1753.
81 Chen Z H, Yang Q, Li H, et al. Journal of Catalysis, 2010, 276(1), 56.
82 Gao G, Shi J W, Fan Z, et al. Chemical Engineering, 2017, 325,91.
83 Wang X Y, Lan Z X, Zhang K, et al. The Journal of Physical Chemistry C, 2017, 121,3339.
84 Zhang L, Shi L Y, Huang L, et al. ACS Catalysis, 2014, 4(6), 1753.
85 Qu W Y, Chen Y X, Huang Z W, et al. Environmental Science & Technology Letters, 2017, 4(6), 246.
86 Yang S J, Wang C Z, Li J H, et al. Applied Catalysis B: Environmental 2011, 110,71.
87 Vennestrom P N R, Janssens T V W, Kustov A, et al. Journal of Catalysis, 2014, 309,477.
88 Gao F Y, Tang X L, Yi H H, et al. Applied Surface Science, 2019, 479,548.
89 Tang X L, Li C L, Yi H H, et al. Chemical Engineering Journal, 2018, 333,467.
90 Stelmachowski P, Maniak G, Kotarba A,et al. Catalysis Communications, 2009, 10(7), 1062.
91 Zasada F, Stelmachowski P, Maniak G, et al. Catalysis Letters, 2009, 127(1), 126.
92 Wang J, Dou Z, Pan Y F, et al. Journal of Molecular Catalysis, 2015, 29(3), 247 (in Chinese).
王建, 窦喆, 潘燕飞,等.分子催化,2015, 29(3), 247.
93 Abu Zied B M, Soliman S A, Abdellah S E. Chinese Journal of Catalysis, 2014, 35(7), 1105.
94 Maniak G, Stelmachowski P, Stanek J J, et al. Catalysis Communications, 2011, 15(1), 127.
95 Franken T, Palkovits R. Applied Catalysis B: Environmental, 2015, 176-177,298.
96 Stelmachowski P, Maniak G, Kaczmarczyk J, et al. Applied Catalysis B: Environmental, 2014, 146,105.
97 Yan L, Ren T, Wang X L, et al. Applied Catalysis B: Environmental, 2003, 45(2), 85.
98 Jia C J, Schwickardi M, Weidenthaler C, et al. Journal of American Chemistry Society, 2011, 133(29), 11279.
99 Kuo C H, Li W K, Song W Q,et al.ACS Applied Materials & Interfaces, 2014, 6(14), 11311.
100 Liu Z G, Wu Z L, Peng X H, et al.The Journal of Physical Chemistry C, 2014, 118(48), 27870.
101 Lou Y, Ma J, Cao X M, et al. ACS Catalysis, 2014, 4(11), 4143.
102 Wang K, Cao Y L, Hu J D, et al. ACS Applied Materials & Interfaces, 2017, 9(19), 16128.
103 Xu J, Deng Y Q, Zhang X M, et al. ACS Catalysis, 2014, 4(11), 4106.
104 Wang H L. Study on CO oxidation catalyzed by manganese oxides. Master's Thesis, Guangxi University ,China, 2016 (in Chinese).
王宏磊. 锰基氧化物催化CO氧化反应的研究. 硕士学位论文, 广西大学, 2016.
105 Gaur S, Johansson S, Mohammad F, et al. The Journal of Physical Chemistry C, 2012, 116(42), 22319.
106 Zheng B,Wu S J, Yang X W,et al.ACS Applied Materials & Interfaces, 2016, 8(40), 26683.
107 Kang M, Lee C H.Applied Catalysis A: General, 2004, 266(2), 163.
108 Liu J D, Zhang T T, Jia A P, et al. Applied Surface Science, 2016, 369,58.
109 Yi H H, Yang Z Y, Tang X L, et al. Chemical Engineering Journal, 2018, 333,554.
110 Yi H H, Yang Z Y, Tang X L, et al. Ultrasonics Sonochemistry, 2018, 40,543.
111 Lei Bai, Frédéric Wyrwalski, Jean-Francois Lamonier, et al. Applied Catalysis B: Environmental, 2013, 138-139,381.
112 Stefanov P, Avramova I, Stoichev D, et al. Applied Surface Science, 2005, 245(1), 65.
113 Ivanov B, Spassova I, Milanova M, et al. Journal of Rare Earths, 2015, 33(4), 382.
114 Modén B, Da Costa P, Fonfé B, et al. Journal of Catalysis, 2002, 209(1), 75.
115 Tang X L, Li J Y, Yi H H, et al. Energy & Fuels, 2017, 31(8), 8580.
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