不同晶体结构MnO_2纳米催化剂低温NH_3-SCR性能研究
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摘要
为了探究催化剂的结构和催化活性的关系,采用水热法制备了四种不同晶体结构的MnO_2纳米催化剂(α-MnO_2、β-MnO_2、γ-MnO_2和δ-MnO_2),并考察了其低温NH3-SCR活性。结果表明,不同晶体结构催化剂的活性不同,依次为γ-MnO_2>α-MnO_2>β-MnO_2>δ-MnO_2,γ-MnO_2表现出最高的催化活性,NOx转化率在150-260℃超过90%。随后,通过X射线衍射(XRD)、扫描电子显微镜(SEM)、N2吸附-脱附、热重(TG)、红外光谱(FT-IR)、程序升温还原(H2-TPR)及吡啶吸附红外光谱(Py-FTIR)等表征手段对催化剂的结构和性质进行分析。结果表明,α-MnO_2和β-MnO_2为纳米棒,γ-MnO_2和δ-MnO_2为纳米针,催化剂的比表面积并不是影响低温NH3-SCR活性的主导因素。γ-MnO_2具有适宜的孔道结构、较强的氧化还原能力、丰富的化学氧含量和Lewis酸酸性位点,是其具有最高低温NH3-SCR活性的原因。
To investigate the relationship between the structure and catalytic activity,four types of MnO_2 nano-catalysts with various crystal structures( α-MnO_2,β-MnO_2,γ-MnO_2 and δ-MnO_2) were synthesized by hydrothermal method,and their lowtemperature NH3-SCR activity were tested. The results indicated that catalysts with different structures showed various activities which followed the sequence of γ-MnO_2>α-MnO_2>β-MnO_2>δ-MnO_2. It was found that γ-MnO_2 showed highest catalytic activity and its NOxconversion rate surpassed90% at the temperature range of 150-260 ℃. The catalysts were characterized by X-ray diffraction( XRD),scanning electron microscopy( SEM),N2 adsorption-desorption,thermogravimetric( TG),infrared( FT-IR),temperature programmed reduction( H2-TPR) and pyridine infrared spectroscopy( Py-FTIR). It was inferred that the morphology of the α-MnO_2 and β-MnO_2 were nanorods,while γ-MnO_2 and δ-MnO_2 with the structures of nanoneedles. The specific surface area of the catalyst was not the dominant factor affecting the NH3-SCR activity at lowtemperature. The decent pore structure,strong redox property,abundant chemisorption oxygen and Lewis acid sites were responsible for high lowtemperature NH3-SCR activity of γ-MnO_2 nano-catalyst.
To investigate the relationship between the structure and catalytic activity,four types of MnO_2 nano-catalysts with various crystal structures( α-MnO_2,β-MnO_2,γ-MnO_2 and δ-MnO_2) were synthesized by hydrothermal method,and their lowtemperature NH3-SCR activity were tested. The results indicated that catalysts with different structures showed various activities which followed the sequence of γ-MnO_2>α-MnO_2>β-MnO_2>δ-MnO_2. It was found that γ-MnO_2 showed highest catalytic activity and its NOxconversion rate surpassed90% at the temperature range of 150-260 ℃. The catalysts were characterized by X-ray diffraction( XRD),scanning electron microscopy( SEM),N2 adsorption-desorption,thermogravimetric( TG),infrared( FT-IR),temperature programmed reduction( H2-TPR) and pyridine infrared spectroscopy( Py-FTIR). It was inferred that the morphology of the α-MnO_2 and β-MnO_2 were nanorods,while γ-MnO_2 and δ-MnO_2 with the structures of nanoneedles. The specific surface area of the catalyst was not the dominant factor affecting the NH3-SCR activity at lowtemperature. The decent pore structure,strong redox property,abundant chemisorption oxygen and Lewis acid sites were responsible for high lowtemperature NH3-SCR activity of γ-MnO_2 nano-catalyst.
引文
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[16]苏潜,黄妍,张颖,李元元,唐南,张俊丰,杨柳春.铜源对Cu-S APO-34氨催化还原NO性能的影响[J].分子催化,2016,30(2):151-158.(SU Qian,HUANG Yan,ZHANG Yin,LI Yuan-yuan,TANG Nan,ZHANG Jun-fen,YANG Liu-chun.Effects of copper sources on selective catalytic reduction of NO w ith NH3of Cu-SAPO-34[J].J M ol Catal,2016,30(2):151-158.)
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[18]WANG C,SUN L,CAO Q,HU B,HUANG Z,TANG X.Surface structure sensitivity of manganese oxides for low-temperature selective catalytic reduction of NO w ith NH3[J].Appl Catal B:Environ,2011,101(3/4):598-605.
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[21]AND S D,MUNICHANDRAIAH N.Effect of crystallographic structure of Mn O2on its electrochemical capacitance properties[J].J Phys Chem C,2008,112(11):4406-4417.
[22]LI Y,FAN Z,SHI J,LIU Z,ZHOU J,SHANGGUAN W.Modified manganese oxide octahedral molecular sieves M'-OMS-2(M'=Co,Ce,Cu)as catalysts in post plasma-catalysis for acetaldehyde degradation[J].Catal Today,2015,256:178-185.
[23]XIE J,CHEN L,ZHOU W F,AU C T,YIN S F.Selective oxidation of p-chlorotoluene to p-chlorobenzaldehyde over metal-modified OMS-2 molecular sieves[J].J M ol Catal A:Chem,2016,425:110-115.
[24]辛勤,罗孟飞.现代催化研究方法[M].北京:科学出版社,2009.(XIN Qin,LUO Meng-fei.The Modern Catalytic Research Method[M].Beijing:Science Press,2009.)
[25]WU Z,JIANG B,LIU Y,WANG H,JIN R.DRIFT study of manganese/titania-based catalysts for low-temperature selective catalytic reduction of NO w ith NH3[J].Environ Sci Technol,2007,41(16):5812-5817.
[26]YU C,HUANG B,DONG L,CHEN F,LIU X.In situ FT-IR study of highly dispersed Mn Ox/SAPO-34 catalyst for low-temperature selective catalytic reduction of NOxby NH3[J].Catal Today,2017,281:610-620.
[2]ROY S,HEGDE MS,MADRAS G.Catalysis for NOxabatement[J].Appl Energy,2009,86(11):2283-2297.
[3]LIU C,SHI J-W,GAO C,NIU C.Manganese oxide-based catalysts for low-temperature selective catalytic reduction of NOxw ith NH3:A review[J].Appl Catal A:Gen,2016,522:54-69.
[4]杨永利,徐东耀,晁春艳,高明.负载型Mn基低温NH3-SCR脱硝催化剂研究综述[J].化工进展,2016,35(4):1094-1100.(YANG Yong-li,XU Dong-yao,CHAO Chun-yan,GAO Ming.Research advance review on supported Mn-based catalysts at low-temperature selective catalytic reduction of NOxw ith NH3[J].Chem Ind Eng Prog,2016,35(4):1094-1100.)
[5]刘亭,王廷春,吴瑞青,沈伯雄.低温NH3-SCR脱硝催化剂研究进展[J].安全与环境学报,2012,19(6):42-44.(LIU Ting,WANG Ting-chun,WU Rui-qing,SHEN Bo-xiong.Research advance review for low-temperature NH3-SCR catalysts[J].J Saf Environ,2012,19(6):42-44.)
[6]KAPTEIJN F,SINGOREDJO L,ANDREINI A,MOULIJN J A.Activity and selectivity of pure manganese oxides in the selective catalytic reduction of nitric oxide w ith ammonia[J].Appl Catal B:Environ,1994,3(2/3):173-189.
[7]刘林林,田华,贺军辉,杨巧文,王东.隐钾锰矿型和水钠锰矿型氧化锰的研究进展[J].化学通报,2011,74(4):000291-000297.(LIU Lin-lin,TIAN Hua,HE Jun-hui,YANG Qiao-wen,WANG Dong.Progress in cryptomelane-and birnessite manganese oxides[J].Chem Bull,2011,74(4):000291-000297.)
[8]THACKERAY M M.Manganese oxides for lithium batteries[J].Prog Solid State Chem,1997,25(1/2):1-71.
[9]LIANG S,TENG F,BULGAN G,RUILONG ZONG A,ZHU Y.Effect of phase structure of Mn O2nanorod catalyst on the activity for CO oxidation[J].J Phys Chem C,2010,112(14):5307-5315.
[10]ZHANG J,LI Y,WANG L,ZHANG C,HE H.Catalytic oxidation of formaldehyde over manganese oxides with different crystal structures[J].Catal Sci Technol,2015,5(4):2305-2313.
[11]戴韵,李俊华,彭悦,唐幸福.Mn O2的晶相结构和表面性质对低温NH3-SCR反应的影响[J].物理化学学报,2012,28(7):1771-1776.(DAI Yun,LI Jun-hua,PENG Yue,TANG Xing-fu.Effects of Mn O2crystal structure and surface property on the NH3-SCR reaction at low temperature[J].Acta Phys Chim Sin,2012,28(7):1771-1776.)
[12]LI Y,LI Y,WAN Y,ZHAN S,GUAN Q,TIAN Y.Structure-performance relationships of Mn O2nanocatalyst for the low-temperature SCR removal of NOxunder ammonia[J].RSC Adv,2016,6(60):54926-54937.
[13]孙梦婷,黄碧纯,马杰文,李时卉,董立夫.二氧化锰在低温NH3-SCR催化反应上的形貌效应[J].物理化学学报,2016,32(6):1501-1510.(SUN Meng-ting,HUANG Bi-chun,MA Jie-wen,LI Shi-hui,DONG Li-fu.Morphological effects of manganese dioxide on catalytic reactions for low-temperature NH3-SCR[J].Acta Phys Chim Sin,2016,32(6):1501-1510.)
[14]SUN M,LAN B,YU L,YE F,SONG W,HE J,DIAO G,ZHENG Y.Manganese oxides with different crystalline structures:Facile hydrothermal synthesis and catalytic activities[J].M ater Lett,2012,86:18-20.
[15]王燕彩,刘昕,宁平,张秋林,张金辉,徐利斯,唐小苏,王明智.制备方法对氧化锰八面体分子筛的NH3选择性催化还原NOx性能的影响[J].燃料化学学报,2014,42(11):1357-1364.(WANG Yan-cai,LIU Xin,NING Ping,ZHANG Qiu-lin,ZHANG Jin-hui,XU Li-si,TANG Xiao-su,WANG Ming-zhi.Effect of preparation methods on selective catalytic reduction of NOxw ith NH3over manganese oxide octahedral molecular sieves[J].J Fuel Chem Technol,2014,42(11):1357-1364.)
[16]苏潜,黄妍,张颖,李元元,唐南,张俊丰,杨柳春.铜源对Cu-S APO-34氨催化还原NO性能的影响[J].分子催化,2016,30(2):151-158.(SU Qian,HUANG Yan,ZHANG Yin,LI Yuan-yuan,TANG Nan,ZHANG Jun-fen,YANG Liu-chun.Effects of copper sources on selective catalytic reduction of NO w ith NH3of Cu-SAPO-34[J].J M ol Catal,2016,30(2):151-158.)
[17]GIOVANOLI R.Thermogravimetry of manganese dioxides[J].Thermochim Acta,1994,234(94):303-313.
[18]WANG C,SUN L,CAO Q,HU B,HUANG Z,TANG X.Surface structure sensitivity of manganese oxides for low-temperature selective catalytic reduction of NO w ith NH3[J].Appl Catal B:Environ,2011,101(3/4):598-605.
[19]WANG ZM,KANOH H.Calorimetric study on NH3insertion reaction into microporous manganese oxides w ith(2×2)tunnel and(2×∞)layered structures[J].Thermochim Acta,2001,379(1):7-14.
[20]郭学益,刘海涵,李栋,田庆华,徐刚.二氧化锰晶型转变研究[J].矿冶工程,2007,27(1):50-53.(GUO Xue-yi,LIU Hai-han,LI Dong,TIAN Qing-hua,XU Gang.Influence of thermal treatment on the crystal phase transformation of M n O2[J].Min Metal Eng,2007,27(1):50-53.)
[21]AND S D,MUNICHANDRAIAH N.Effect of crystallographic structure of Mn O2on its electrochemical capacitance properties[J].J Phys Chem C,2008,112(11):4406-4417.
[22]LI Y,FAN Z,SHI J,LIU Z,ZHOU J,SHANGGUAN W.Modified manganese oxide octahedral molecular sieves M'-OMS-2(M'=Co,Ce,Cu)as catalysts in post plasma-catalysis for acetaldehyde degradation[J].Catal Today,2015,256:178-185.
[23]XIE J,CHEN L,ZHOU W F,AU C T,YIN S F.Selective oxidation of p-chlorotoluene to p-chlorobenzaldehyde over metal-modified OMS-2 molecular sieves[J].J M ol Catal A:Chem,2016,425:110-115.
[24]辛勤,罗孟飞.现代催化研究方法[M].北京:科学出版社,2009.(XIN Qin,LUO Meng-fei.The Modern Catalytic Research Method[M].Beijing:Science Press,2009.)
[25]WU Z,JIANG B,LIU Y,WANG H,JIN R.DRIFT study of manganese/titania-based catalysts for low-temperature selective catalytic reduction of NO w ith NH3[J].Environ Sci Technol,2007,41(16):5812-5817.
[26]YU C,HUANG B,DONG L,CHEN F,LIU X.In situ FT-IR study of highly dispersed Mn Ox/SAPO-34 catalyst for low-temperature selective catalytic reduction of NOxby NH3[J].Catal Today,2017,281:610-620.