Ce、Zr改性Mn/ZSM-5分子筛催化剂对C_3H_6-SCR反应性能的影响
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摘要
采用浸渍法制备了一系列Ce、Zr改性Mn/ZSM-5分子筛催化剂,对其C_3H_6-SCR(选择性催化还原)反应性能进行了评价,研究了Ce、Zr的引入对Mn/ZSM-5分子筛催化剂选择催化还原NO的影响,并采用X射线衍射、比表面积测量、扫描电子显微镜、NH_3-程序升温脱附(TPD)、H_2-程序升温还原(TPR)等表征手段对催化剂的物理化学性质进行了表征。结果表明:Ce、 Zr改性Mn/ZSM-5分子筛催化剂C_3H_6-SCR反应中表现出较为优异的催化活性,最优配比的20%Mn-7%Ce-1%Zr/ZSM-5催化剂在200℃、30000h~(-1)的空速下,催化剂的最大脱硝效率达到87%,且操作温度窗口T50=150～380℃。活性组分Mn以MnO_2和Mn_2O_3形式存在,且与助剂Ce、Zr高度分散在催化剂表面,而且形成协同作用;催化剂表面的弱酸和中强酸和氧化还原性能的增强有利于C_3H_6-SCR低温催化活性的提高。
A series of Ce, Zr modified Mn/ZSM-5 molecular sieve catalysts were prepared by an impregnation method, and the C_3H_6-selective catalytic reduction(SCR) reaction performance was evaluated.The effects of Ce and Zr on the SCR of NO on Mn/ZSM-5 molecular sieve catalyst were investigated.The physical and chemical properties of the catalysts were characterized by X-ray diffraction, specific surface area measurement, scanning electron microscopy, NH_3-temperature programmed desorption(TPD), and H_2-TPR, respectively.The results show that Ce and Zr modified Mn/ZSM-5 molecular sieve catalyst shows an excellent catalytic activity in the C_3H_6-SCR reaction.At 200 ℃ and a space velocity of 30 000 h~(-1), the optimal ratio of 20%Mn-7%Ce-1%Zr/ZSM-5 catalyst has a maximum NO conversion of 87% and NO conversion of >50% at 150-380 ℃ in a wide operating temperature range.The active component Mn exists in the forms of MnO_2 and Mn_2O_3.Mn, Ce and Zr are mainly dispersed on the catalyst surface and form a synergy.The weak acid and moderate acidity of the catalyst surface and the enhancement of the redox properties are beneficial to the improvement of low-temperature catalytic activity in C_3H_6-SCR.
A series of Ce, Zr modified Mn/ZSM-5 molecular sieve catalysts were prepared by an impregnation method, and the C_3H_6-selective catalytic reduction(SCR) reaction performance was evaluated.The effects of Ce and Zr on the SCR of NO on Mn/ZSM-5 molecular sieve catalyst were investigated.The physical and chemical properties of the catalysts were characterized by X-ray diffraction, specific surface area measurement, scanning electron microscopy, NH_3-temperature programmed desorption(TPD), and H_2-TPR, respectively.The results show that Ce and Zr modified Mn/ZSM-5 molecular sieve catalyst shows an excellent catalytic activity in the C_3H_6-SCR reaction.At 200 ℃ and a space velocity of 30 000 h~(-1), the optimal ratio of 20%Mn-7%Ce-1%Zr/ZSM-5 catalyst has a maximum NO conversion of 87% and NO conversion of >50% at 150-380 ℃ in a wide operating temperature range.The active component Mn exists in the forms of MnO_2 and Mn_2O_3.Mn, Ce and Zr are mainly dispersed on the catalyst surface and form a synergy.The weak acid and moderate acidity of the catalyst surface and the enhancement of the redox properties are beneficial to the improvement of low-temperature catalytic activity in C_3H_6-SCR.
引文
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[2]SMIRNIOTIS P G,SREEKANTH P M,PE?A D A,et al.Manganese oxide catalysts supported on TiO2,Al2O3 and SiO2:A comparison for low-temperature SCR of NO with NH3[J].Ind Eng Chem Res,2006,45(19):6436-6443.
[3]胡和兵,王牧野,吴勇民,等.氮氧化物的污染与治理方法[J].环境保护科学,2006,32(4):5-9.HU Hebing,WANG Muye,WU Yongmin,et al.Environ Protec Sci(in Chinese),2006,32(4):5-9.
[4]ZENBOURY L,AZAMBRE B,WEBER J V.Transient TPSR,DRIFTS-MS and TGA studies of a Pd/ceria-zirconia catalyst in CH4and NO2 atmospheres[J].Catal Today,2008,137(2):167-173.
[5]CHEN X,YANG X,ZHU A,et al.In situ DRIFTS study during C2H4-SCR of NO over Co-ZSM-5[J].J Mol Catal A-Chem,2009,312(1):31-39.
[6]PALOMARES A E,FRANCH C,CORMA A.Determining the characteristics of a Co-zeolite to be active for the selective catalytic reduction of NOx with hydrocarbons[J].Catal Today,2011,176(1):239-241.
[7]WANG X Q,LI Y,CHEN W,et al.Characteristics of NOx removal combining dielectric barrier discharge plasma with selective catalytic reduction by C3H6[J].Jpn J Appl Phys,2010,49(8R):086201.
[8]KUMAR P A,REDDY M P,HYUN-SOOK B,et al.Influence of Mg addition on the catalytic activity of alumina supported Ag for C3H6-SCR of NO[J].Catal Lett,2009,131(1-2):85-97.
[9]YANG W,ZHANG R,CHEN B,et al.New Aspects on the Mechanism of C3H6 Selective Catalytic Reduction of NO in the Presence of O2over LaFe1-x(Cu,Pd)x O3-δPerovskites[J].Environ Sci Technol,2012,46(20):11280-11288.
[10]SHEN B X,LIU T.Deactivation of MnOx-CeOx/ACF catalysts for lower-temperature NH3-SCR in the presence of SO2[J].Acta Phys Chim Sin,2010,26(11):3009-3016.
[11]潘华,建艳飞,陈宁娜,等.甲烷催化还原NOx中Co基/分子筛催化剂的助剂和载体优化[J].环境科学,2017,38(7):3085-3094.PAN Hua,JIAN Yanfei,CHEN Ningna,et al.Environ Sci(in Chinese),2017,38(7):3085-3094.
[12]KWAK J H,TONKYN R G,KIM D H,et al.Excellent activity and selectivity of Cu-SSZ-13 in the selective catalytic reduction of NOx with NH3[J].J Catal,2010,275(2):187-190.
[13]KIM Y J,KWON H J,HEO I,et al.Mn-Fe/ZSM-5 as a low-temperature SCR catalyst to remove NOx from diesel engine exhaust[J].Appl Catal B-Environ,2012,126:9-21.
[14]陈树伟,闫晓亮,陈佳琪,等.富氧条件下Mn/ZSM-5选择催化CH4还原NO[J].催化学报,2010,31(9):1107-1114.CHEN Shuwei,YAN Xiaoliang,CHEN jiaqi,et al.Chin J Catal(in Chinese),2010,31(9):1107-1114.
[15]YANG T T,BI H T,CHENG X.Effects of O2,CO2 and H2O on NOx adsorption and selective catalytic reduction over Fe/ZSM-5[J].Appl Catal B-Environ,2011,102(1/2):163-171.
[16]BERNDT H,SCHüTZE F W,RICHTER M,et al.Selective catalytic reduction of NO under lean conditions by methane and propane over indium/cerium-promoted zeolites[J].Appl Catal B-Environ,2003,40(1):51-67.
[17]HOUEL V,JAMES D,MILLINGTON P,et al.A comparison of the activity and deactivation of Ag/Al2O3 and Cu/ZSM-5 for HC-SCRunder simulated diesel exhaust emission conditions[J].J Catal,2005,230(1):150-157.
[18]张丹,许俊强,周亭,等.Zr助剂对富氧条件下Ag/Al2O3选择性催化C3H6还原NO性能的影响[J].材料导报,2016,30(12):105-110.ZHANG Dan,XU Junqiang,ZHOU Ting,et al.Mater Rev(in Chinese),2016,30(12):105-110.
[19]SAQER S M,KONDARIDES D I,VERYKIOS X E.Catalytic oxidation of toluene over binary mixtures of copper manganese and cerium oxides supported onγ-Al2O3[J].Appl Catal B-Environ,2011,103(3/4):275-286.
[20]黄增斌,李翠清,王振,等.不同分子筛负载锰铈催化剂的低温NH3-SCR脱硝性能[J].燃料化学学报,2016,44(11):1388-1393.HUANG Zengbin,LI Cuiqing,WANG Zhen,et al.J Fuel Chem Technol(in Chinese),2016,44(11):1388-1393.
[21]MU W T,ZHU J,ZHANG S,et al.Novel proposition on mechanism aspects over Fe-Mn/ZSM-5 catalyst for NH3-SCR of NOx at low temperature[J].Catal Sci Technol,2016,6(20):7532-7548.