Mg_3Mn_xAl_(1-x)CO_3类水滑石衍生NSR催化剂的制备及其性能评价
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摘要
采用共沉淀法合成了三元类水滑石Mg_3Mn_xAl_(1-x)CO_3,通过高温煅烧得到其衍生氧化物Mg_3Mn_xAl_(1-x)O_m,再经浸渍负载Pt或BaO后制得新型NO_x存储/再还原(NSR)催化剂。XRD及SEM表征结果显示,当Mn与Al的摩尔比(Mn/Al)大于1时所制备的Mg_3Mn_xAl_(1-x)O_m有杂晶相出现且发生团聚,结合NO_x存储性能评价结果,确定最优Mn/Al为1。BaO负载不利于NO_x的存储,而当Pt负载量为1%(w)时NO_x存储性能最优,250℃条件下的存储量由负载前的0.52 mmol/g提升至0.61 mmol/g。CO_2与NO_x之间存在较强的竞争吸附。负载1%Pt催化剂的NSR性能评价结果表明,8个稀燃-富燃循环后NO_x的去除率为68%,表明催化剂的还原性能仍需加强。
Ternary hydrotalcite-like Mg_3Mn_xAl_(1-x)CO_3 was synthesized by coprecipitation method. Its derivative oxides Mg_3Mn_xAl_(1-x)O_m were obtained by calcination at high temperature,and then supported with Pt or BaO by impregnation to prepare a new type of NO_x storage and reduction(NSR)catalysts. The characterization results obtained by XRD and SEM showed that when the molar ratio of Mn to Al(Mn/Al)was higher than 1,the prepared Mg_3Mn_xAl_(1-x)O_m had hetero-crystalline phase and agglomerated. Combining with the evaluation results of NO_x storage performance,the optimum Mn/Al was determined to be 1. BaO loading was not conducive to NO_x storage,and the catalyst loading 1%(w)Pt showed the best NO_x storage capacity of 0.61 mmol/g at 250 ℃,which is higher than 0.52 mmol/g before loading.There was a strong competitive adsorption behavior between CO_2 and NO_x. The evaluation results of NSR capability of catalyst loading 1% Pt showed that after 8 lean burn-rich burn cycles,the removal rate of NO_x was only 68%,indicating that the reductive capability of the catalyst still needed to be enhanced.
Ternary hydrotalcite-like Mg_3Mn_xAl_(1-x)CO_3 was synthesized by coprecipitation method. Its derivative oxides Mg_3Mn_xAl_(1-x)O_m were obtained by calcination at high temperature,and then supported with Pt or BaO by impregnation to prepare a new type of NO_x storage and reduction(NSR)catalysts. The characterization results obtained by XRD and SEM showed that when the molar ratio of Mn to Al(Mn/Al)was higher than 1,the prepared Mg_3Mn_xAl_(1-x)O_m had hetero-crystalline phase and agglomerated. Combining with the evaluation results of NO_x storage performance,the optimum Mn/Al was determined to be 1. BaO loading was not conducive to NO_x storage,and the catalyst loading 1%(w)Pt showed the best NO_x storage capacity of 0.61 mmol/g at 250 ℃,which is higher than 0.52 mmol/g before loading.There was a strong competitive adsorption behavior between CO_2 and NO_x. The evaluation results of NSR capability of catalyst loading 1% Pt showed that after 8 lean burn-rich burn cycles,the removal rate of NO_x was only 68%,indicating that the reductive capability of the catalyst still needed to be enhanced.
引文
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[2]刘小华.基于氮氧化物危害及其防治对策[J].低碳世界,2017(9):8-9.
[3]陈文浩.发动机稀薄燃烧技术对排放的影响[J].时代汽车,2018(1):101-102.
[4]乔南利,杨忆新,宋焕巧,等.低温NH3-SCR脱硝催化剂的研究现状与进展[J].化工环保,2017,37(3):282-288.
[5]FRITZ A,PITCHON V.The current state of research on automotive lean NOx catalysis[J].Appl Catal,B,1997,13(1):1-25.
[6]NUNAN J G,ROBOTA H J,COHN M J,et al.Physicochemical properties of Ce-containing three-way catalysts and the effect of Ce on catalyst activity[J].JCatal,1992,133(2):309-324.
[7]DOI Y,HANEDA M,OZAWA M.Direct decomposition of NO on Ba catalysts supported on rare earth oxides[J].JMol Catal A:Chem,2014,383/384:70-76.
[8]HANEDA M,HAMADA H.Recent progress in catalytic NO decomposition[J].CR Chim,2016,19(10):1254-1265.
[9]JIANG Y,GAO X,ZHANG Y X,et al.Effects of PbCl2 on selective catalytic reduction of NO with NH3over vanadia-based catalysts[J].J Hazard Mater,2014,274:270-278.
[10]马景琦.SCR催化剂的研究进展[J].科技资讯,2017,15(10):112-113.
[11]GRANGER P,PARVULESCU V I.Catalytic NOx abatement systems for mobile sources:from threeway to lean burn after-treatment technologies[J].Chem Rev,2011,111(5):3155-3207.
[12]JOSHI S Y,REN Y J,HAROLD M P,et al.Determination of kinetics and controlling regimes for H2 oxidation on Pt/Al2O3 monolithic catalyst using high space vel city experiments[J].Appl Catal B,2011,102(3/4):484-495.
[13]LIETTI L,FORZATTI P,NOVA I,et al.NOx storage reduction over Pt-Ba/γ-Al2O3 Catalyst[J].J Catal,2001,204(1):175-191.
[14]Epling W S,Campbell L E,Yezerets A,et al.Overview of the fundamental reactions and degradation mechanisms of NOx storage/reduction catalysts[J].Cat Rev Sci Eng,2004,46(2):163-245.
[15]WANG Q,CHUNG J S.NOx storage and reduction over Cu/K2Ti2O5 in a wide temperature range:activity,characterization,and mechanism[J].Appl Catal,A,2009,358(1):59-64.
[16]LIU G,GAO P X.A review of NOx storage/reduction catalysts:mechanism,materials and degradation studies[J].Catal Sci Technol,2011,1(4):552-568.
[17]OLSSON L,FRIDELL E.The influence of Pt oxide formation and Pt dispersion on the reactions NO2NO+1/2O2 over Pt/Al2O3 and Pt/BaO/Al2O3[J].JCatal,2002,210(2):340-353.
[18]PRINETTO F,MANZOLI M,MORANDI S,et al.Pt-K/Al2O3 NSR catalysts:characterization of morphological,structural and surface properties[J].JPhy.Chem C,2010,114(2):1127-1138.
[19]MANZI-NSHUTI C,WANG D Y,HOSSENLOPP JM,et al.Aluminum-containing layered double hydroxides:the thermal,mechanical,and fire properties of(nano)composites of poly(methyl methacrylate)[J].J Mater Chem,2008,18(26):3091-3102.
[20]WILLIAMS G R,KHAN A I,O’HARE D.Mechanistic and kinetic studies of guest ion intercalation into layered double hydroxides using time-resolved,in situ X-ray powder diffraction[M]//DUAN X,EVANS DG.Layered Double Hydroxides.Berlin:Springer,2005:161-192.
[21]WANG Q,LUO J Z,ZHONG Z Y,et al.CO2 capture by solid adsorbents and their applications:current status and new trends[J].Energy Environ Sci,2011,4(1):42-55.
[22]WANG Q,WU Z H,TAY H H,et al.High temperature adsorption of CO2 on Mg-Al hydrotalcite:effect of the charge compensating anions and the synthesis pH[J].Catal Today,2011,164(1):198-203.
[23]CAVANI F,TRIFIRòF,VACCARI A.Hydrotalcite-type anionic clays:preparation,properties and applications[J].Catal Today,1991,11(2):173-301.
[24]FORNASARI G,TRIFIRòF,VACCARI A,et al.Novel low temperature NOx storage-reduction catalysts for diesel light-duty engine emissions based on hydrotalcite compounds[J].Catal Today,2002,75(1/4):421-429.
[25]CENTI G,FORNASARI G,GOBBI C,et al.NOx storage-reduction catalysts based on hydrotalcite:effect of Cu in promoting resistance to deactivation[J].Catal Today,2002,73(3/4):287-296.
[26]PALOMARES A E,UZCáTEGUI A,CORMA A.NOx storage/reduction catalysts based in cobalt/copper hydrotalcites[J].Catal Today,2008,137(2/4):261-266.
[27]QIU L Z,CHEN W,QU B J.Structural characterisation and thermal properties of exfoliated polystyrene/ZnAl layered double hydroxide nan composites prepared via solution intercalation[J].Polym Degrad Stab,2005,87(3):433-440.
[28]LIU Y,MENG M,ZOU Z Q,et al.In situ DRIFTSinvestigation on the NOx storage mechanisms over Pt/K/TiO2-ZrO2 catalyst[J].Catal Commun,2008,10(2):173-177.
[29]ROY S,BAIKER A.NOx storage-reduction catalysis:from mechanism and materials properties to storage-reduction performance[J].Chem Rev,2009,109(9):4054-4091.
[30]VERRIER C,KWAK J H,KIM D H,et al.NOx uptake on alkaline earth oxides(BaO,MgO,CaO and SrO)supported onγ-Al2O3[J].Catal Today,2008,136(1/2):121-127.
[31]LUO J Y,MENG M,ZHA Y Q,et al.A comparative study of Pt/Ba/Al2O3 and Pt/Fe-Ba/Al2O3 NSRcatalysts:new insights into the interaction of Pt-Ba and the function of Fe[J].Appl Catal,B,2008,78(1/2):38-52.
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