Mn-Ce/(CC-A)@12TiO_2整体式蜂窝催化剂的制备及脱硝性能研究
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摘要
以氨水预处理后的堇青石蜂窝陶瓷为基体,采用半原位溶胶-凝胶工艺制备涂覆TiO_2涂层的Mn-Ce/(CC-A)@12TiO2整装脱硝催化剂,在80～260℃,NOx转化率达90%以上。N2吸脱附、XRD、TG-DSC等分析测试表明,TiO_2主要以结构完整的锐钛矿晶型存在,促进了活泼氧物质的生成,提高了催化活性。SEM图像表明,催化剂表面TiO_2涂层上具有裂纹和粗糙表面,有利于三维结构以及更多孔结构的形成,为反应物与活性位之间相互作用产生更多的活性中间体,从而促进反应速率提供了适宜的场所。EDS研究显示,催化剂Mn-Ce/(CC-A)@12TiO2中TiO_2表面形成的弱结晶Mn-Ce混合氧化物可能有利于Mn与Ce的微观协同效应,提高中间体的形成。
Pretreating of CC with NH3·H2 O and coating of TiO_2 with semi-in-situ sol-gel method over CC-A were propitious to low-temperture catalytic performance of NH3-SCR over monolith catalyst Mn-Ce/( CC-A) @ 12 TiO2,with above 90% conversion of NOxduring 80 ～ 260 ℃. Results of N2-adsorption/desorption,XRD and DSC indicated that TiO_2 mainly existed in intact anatase crystalline which accelerated the generation of labile oxygen species with contribution to activity. SEM images demonstrated that threedimensional structure and more channels were formed over catalyst surface due to fissures and rough surface of special TiO_2 coating,which was conducive to interaction between reactants and active sites generating more reactive intermediates to accelerate reaction rate. EDS result showed that,Mn-Ce mixed oxides with weak crystalline over Mn-Ce/( CC-A) @ 12 TiO2 might facilitate the synergistic effect between Mn and Ce to enhance the formation of intermediates as well.
Pretreating of CC with NH3·H2 O and coating of TiO_2 with semi-in-situ sol-gel method over CC-A were propitious to low-temperture catalytic performance of NH3-SCR over monolith catalyst Mn-Ce/( CC-A) @ 12 TiO2,with above 90% conversion of NOxduring 80 ～ 260 ℃. Results of N2-adsorption/desorption,XRD and DSC indicated that TiO_2 mainly existed in intact anatase crystalline which accelerated the generation of labile oxygen species with contribution to activity. SEM images demonstrated that threedimensional structure and more channels were formed over catalyst surface due to fissures and rough surface of special TiO_2 coating,which was conducive to interaction between reactants and active sites generating more reactive intermediates to accelerate reaction rate. EDS result showed that,Mn-Ce mixed oxides with weak crystalline over Mn-Ce/( CC-A) @ 12 TiO2 might facilitate the synergistic effect between Mn and Ce to enhance the formation of intermediates as well.
引文
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[40] Li J,Yang C,Zhang Q,et al. Effects of Fe addition on the structure and catalytic performance of mesoporous Mn/AlSBA-15 catalysts for the reduction of NO with ammonia[J]. Catal Commun,2015,62:24-28.
[2] Mu W,Zhu J,Zhang S,et al. Novel proposition on mechanism aspects over Fe-Mn/ZSM-5 catalyst for NH3-SCR of NOxat low temperature:rate and direction of multifunctional electron-transfer-bridge and in situ DRIFTs analysis[J]. Catal Sci Technol,2016,6(20):7532-7548.
[3] Jiang B,Li Z,Lee S C. Mechanism study of the promotional effect of O2on low-temperature SCR reaction on FeMn/Ti O2by DRIFT[J]. Chem Eng J,2013,225:52-58.
[4] Chen Z,Wang F,Li H,et al. Low-temperature selective catalytic reduction of NOxwith NH3over Fe-Mn mixed-oxide catalysts containing Fe3Mn3O8phase[J]. Ind Eng Chem Res,2012,51(1):202-212.
[5] Smirniotis P G,Sreekanth P M,Pe1a D A,et al. Manganese oxide catalysts supported on Ti O2,Al2O3,and Si O2:A comparison for low-temperature SCR of NO with NH3[J]. Ind Eng Chem Res,2006,45(19):6436-6443.
[6] Li F,Shen B,Tian L,et al. Enhancement of SCR activity and mechanical stability on cordierite supported V2O5-WO3/Ti O2catalyst by substrate acid pretreatment and addition of silica[J]. Powder Technol,2016,297:384-391.
[7] Zhou H,Su Y,Liao W,et al. Preparation,characterization,and properties of monolithic Fe/Al2O3/cordierite catalysts for NO reduction with C2H6[J]. Appl Catal A-Gen,2015,505:402-409.
[8] Zhou H,Su Y,Liao W,et al. NO reduction by propane over monolithic cordierite-based Fe/Al2O3catalyst:Reaction mechanism and effect of H2O/SO2[J]. Fuel,2016,182:352-360.
[9] Qiu Y,Liu B,Du J,et al. The monolithic cordierite supported V2O5-MoO3/Ti O2catalyst for NH3-SCR[J]. Chem Eng J,2016,294:264-272.
[10] Huang H-f,Jin L-l,Lu H-F,et al. Monolithic Cr-V/Ti O2/cordierite catalysts prepared by in-situ precipitation and impregnation for low-temperature NH3-SCR reactions[J].Catal Commun,2013,34:1-4.
[11] Wang J C,Chen Y,Tang L,et al. One-step hydrothermal synthesis of Cu-SAPO-34/cordierite and its catalytic performance on NOxremoval from diesel vehicles[J]. T Nonferr Metal Soc,2013,23(11):3330-3336.
[12] Wang J,Peng Z,Chen Y,et al. In-situ hydrothermal synthesis of Cu-SSZ-13/cordierite for the catalytic removal of NOxfrom diesel vehicles by NH3[J]. Chem Eng J,2015,263:9-19.
[13] Smirniotis P G,Pe1a D A,Uphade B S. Low-temperature selective catalytic reduction(SCR)of NO with NH3by using Mn,Cr,and Cu oxides supported on hombikat Ti O2[J]. Angew Chem Int Edit,2001,40(13):2479-2482.
[14] Meng D,Zhan W,Guo Y,et al. A highly effective catalyst of Sm-MnOxfor the NH3-SCR of NOxat low temperature:Promotional role of Sm and its catalytic performance[J].ACS Catal,2015,5(10):5973-5983.
[15] Zhou G,Zhong B,Wang W,et al. In situ DRIFTS study of NO reduction by NH3over Fe-Ce-Mn/ZSM-5 catalysts[J]. Catal Today,2011,175(1):157-163.
[16] Cao F,Su S,Xiang J,et al. The activity and mechanism study of Fe-Mn-Ce/γ-Al2O3catalyst for low temperature selective catalytic reduction of NO with NH3[J]. Fuel,2015,139:232-239.
[17] Xiong S,Liao Y,Dang H,et al. Promotion mechanism of Ce O2addition on the low temperature SCR reaction over MnOx/Ti O2:a new insight from the kinetic study[J].RSC Adv,2015,5(35):27785-27793.
[18] Lee S M,Park K H,Hong S C. MnOx/Ce O2-Ti O2mixed oxide catalysts for the selective catalytic reduction of NO with NH3at low temperature[J]. Che Eng J,2012,195/196(Supplement C):323-331.
[19] Liu Z,Zhu J,Li J,et al. Novel Mn-Ce-Ti mixed-oxide catalyst for the selective catalytic reduction of NOxwith NH3[J]. ACS Appl Mater Inter,2014,6(16):14500-14508.
[20] Xu Q,Su R,Cao L,et al. Facile preparation of high-performance Fe-doped Ce-Mn/Ti O2catalysts for the low-temperature selective catalytic reduction of NOxwith NH3[J]. RSC Adv,2017,7(77):48785-48792.
[21] Cui M,Li Y,Wang X,et al. Effect of preparation method on MnOx-Ce O2catalysts for NO oxidation[J]. J Rare Earth,2013,31(6):572-576.
[22] Wu X,Si Z,Li G,et al. Effects of cerium and vanadium on the activity and selectivity of MnOx-Ti O2catalyst for low-temperature NH3-SCR[J]. J Rare Earth,2011,29(1):64-68.
[23] Li L,Diao Y,Liu X. Ce-Mn mixed oxides supported on glass-fiber for low-temperature selective catalytic reduction of NO with NH3[J]. J Rare Earth,2014,32(5):409-415.
[24] Tang X,Gao F,Xiang Y,et al. Effect of potassium-precursor promoters on catalytic oxidation activity of Mn-CoOx catalysts for NO removal[J]. Ind Eng Chem Res,2015,54(37):9116-9123.
[25] Chen Z,Yang Q,Li H,et al. Cr-MnOxmixed-oxide catalysts for selective catalytic reduction of NOxwith NH3at low temperature[J]. J Catal,2010,276(1):56-65.
[26] Liu L,Zhao H,Andino J M,et al. Photocatalytic CO2reduction with H2O on Ti O2nanocrystals:Comparison of anatase,rutile,and brookite polymorphs and exploration of surface chemistry[J]. ACS Catal,2012,2(8):1817-1828.
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[29] Hu H,Cai S,Li H,et al. Mechanistic aspects of de NOx processing over Ti O2supported Co-Mn oxide catalysts:Structure-activity relationships and in situ DRIFTs analysis[J]. ACS Catal,2015,5(10):6069-6077.
[30] L Xiaoxin,J Zhengguo,B Shaojing,et al. Influences of solvent on properties of Ti O2porous films prepared by a solgel method from the system containing PEG[J]. J Sol-Gel Sci Techn,2005,36(1):103-111.
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[32] An Z,Zhuo Y,Xu C,et al. Influence of the Ti O2crystalline phase of MnOx/Ti O2catalysts for NO oxidation[J].Chinese J Catal,2014,35(1):120-126.
[33] Yao X,Zhao R,Chen L,et al. Selective catalytic reduction of NOxby NH3over Ce O2supported on Ti O2:Comparison of anatase,brookite,and rutile[J]. Appl Catal B-Environ,2017,208:82-93.
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[35] Ettireddy P R,Ettireddy N,Mamedov S,et al. Surface characterization studies of Ti O2supported manganese oxide catalysts for low temperature SCR of NO with NH3[J]. Appl Catal B-Environ,2007,76(1/2):123-134.
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[37] Wang W,McCool G,Kapur N,et al. Mixed-phase oxide catalyst based on Mn-mullite(Sm,Gd)Mn2O5for NO oxidation in diesel exhaust[J]. Science,2012,337(6096):832-835.
[38] Liu F,He H,Ding Y,et al. Effect of manganese substitution on the structure and activity of iron titanate catalyst for the selective catalytic reduction of NO with NH3[J].Appl Catal B-Environ,2009,93(1/2):194-204.
[39] Kang M,Park E D,Kim J M,et al. Cu-Mn mixed oxides for low temperature NO reduction with NH3[J]. Catal Today,2006,111(3/4):236-241.
[40] Li J,Yang C,Zhang Q,et al. Effects of Fe addition on the structure and catalytic performance of mesoporous Mn/AlSBA-15 catalysts for the reduction of NO with ammonia[J]. Catal Commun,2015,62:24-28.