摘要
随着人们对环境质量要求的不断提高,吸烟场所、厨房、汽车拥挤的公路上产生的低浓度氮氧化物造成的环境污染日益受到重视。低浓度氮氧化物的脱除对催化剂的性能提出了新的挑战。光催化技术是近几年发展起来的一项空气净化技术,该技术由于利用太阳光,可以在室温下进行,以及高效处理低浓度污染物(无需富集),具有反应条件温和、操作易于控制、能耗低、二次污染少等优点,在处理低浓度大气污染物方面具有很高的研究价值和潜在的应用背景。
本论文以高吸附性的H-ZSM-5分子筛为载体,银离子改性制得的催化剂,在紫外光下对NO这一典型氮氧化物进行光催化脱除,并借助XRD、UV-vis漫反射、TPD、原位AgNO3程序升温分解等技术对催化剂表征,对反应中起重要作用的银物种及光催化分解NO机理进行了探讨和研究。为进一步提高光催化分解NO活性,同时还对催化剂做了进一步改性。论文取得了以下有意义结果：
1.光催化分解NO反应是在一套自制的套管式固定床光催化反应器中进行。H-ZSM-5分子筛中活性组分银的引入提高了催化剂光催化分解NO反应活性,银担载量、反应气NO初始浓度、灯距对光催化分解NO反应有较大影响。
2.通过在不同预处理条件下处理得到的Ag/H-ZSM-5催化剂,对NO进行光催化分解实验,实验表明,不同预处理条件能明显影响Ag/H-ZSM-5催化剂的活性。将XRD、UV-vis漫反射表征与活性数据相关联,发现随着预处理温度升高,单个的银原子为降低表面能会聚集,并随着温度升高颗粒逐渐长大,催化剂光催化分解NO活性逐渐下降；氧化性气氛处理的催化剂上银物种主要为银离子和银簇,光催化分解NO活性最高,而催化剂经还原性气氛处理使交换到阳离子位的部分Ag+被还原为Ag0,具有最差的光催化分解NO活性。结合包信和等人建立的定量区分分子筛内外表面银物种含量的方法,确立高度分散于分子筛阳离子位上的银离子及银簇是光催化分解NO的活性中心。
3.为获得更多活性银物种提高催化剂的光催化分解NO活性,对银催化剂进行如下改性：首先,将银担载在不同的分子筛载体上进行光催化分解NO反应,实验结果表明,Ag/H-ZSM-5催化剂具有最好的光催化分解NO活性。结合XRD, UV-vis、原位AgNO3程序升温分解等技术发现,虽然Ag/HY催化剂上具有最多的活性银物种,但光催化分解NO活性并不是最高,这主要是由于孔径的限制,反应物NO分子不能与分子筛中的活性银物种有效接触。其次,通过采用银氨溶液作为银源,获得更多的活性银物种,催化剂具有较高的光催化分解NO活性。
4.通过对新鲜催化剂的NO吸附饱和后程序升温脱附和反应4个小时后的催化剂程序升温脱附过程的研究,结果表明,光催化分解NO生成的氧吸附在催化剂活性位上难以脱附是催化剂失活的主要原因。惰性气氛500℃处理可以使催化剂部分再生。
As people's consciousness on environmental quality continues to increase, the indoor air pollution attracts people's attention day by day. The low concentrations of nitrogen oxides mainly come from smoking areas and kitchen, car congested highway. Effective removal of low concentration of nitrogen oxides, i.e, the direct decomposition of NO into N2 and O2, has been a great challenge for many researchers. Photocatalysis is an attractive, clean, safe, low-temperature reaction and a nonenergy-intensitive approach, especilly, for chemical waste removal.
In this thesis, the photocatalytic decomposition of NO under UV light was investigated over silver modified H-ZSM-5 catalysts. The characterizations of XRD, UV-vis diffuse spectra, TPD, temperature-programmed decomposition of AgNO3 were employed to discriminate different kinds of Ag species. By correlating silver species with their photo-catalytic behaviors in NO decomposition, the active species for NO decomposition is clarified. Some interesting results were got as follows:
1. The photocatalytic decomposition of NO was carried out in a self-made fixed bed reactor. Silver introduced into H-ZSM-5 greatly enhanced the catalytic activity in photocacalytic decomposition of NO. Silver loadings, the initial NO concentration, lamp distance has great affects on the photocatalytic activities.
2. Silver is shown to be a structure-sensitive catalyst. Pretreatment has different influence on the catalytic performance. Upon thermal treatment in nitrogen, thermal induced changes in silver morphology leaded to the formation of reduced silver clusters and nano-silver particles to achieve a minimization of surface free energy. With the increase of pretreatment temperatures, catalytic activity decreased. Upon oxygen treatment of silver catalysts at elevated temperatures, the oxygen oxidized silver species into silver ions and depresses the growing of silver patticles. While under thermal treatment in hydrogen, the reduction atmosphere enchanced silver ions self-reduced and aggregated into silver particles. Consequently, the the catalyst lost part of its activity. Using the method of quantitative discrimination of silver species in the zeolite channels and those deposited on the zeolite surface established by Bao Xinhe et.al, it was concluded that silver ions and silver clusters played an important role on the photocatalytic decomposition of NO.
3. To improve the photocatalytic reactivity, silver was supported on different kinds of zeolites. It indicated that Ag/H-ZSM-5 catalyst has the best photocatalytic activity. Combined with XRD, UV-vis and in situ temperature-programmed decomposition of AgNO3 techniques, it is found that Ag/HY catalyst had the most active silver species, but the activity of which was worst. This is mainly due to aperture restriction. Size 6-ring window in Y zeolite is smaller than the kinetic diameter of NO. Therefore, NO is difficult to be activated over this catalyst. While aqueous solution of silver ammonia was used as a precursor for Ag to impregnate in H-ZSM-5 zeolite. The Ag(NH)/H-ZSM-5 catalysts with more active Ag species had better activity.
4. Study on the TPD results over the fresh and used samples indicates that oxygen produced from NO dissociation strongly adsorbed on silver catalyst, which blocks the active sites. That might be the reason for catalyst deactivation.
引文
[1]CANT N W, COLE J R, Photocatalysis of the reaction between ammonia and nitric oxide on TiO2 surfaces [J]. J. Catal.,1992,134:317-330.
[2]SANO T, NEGISHI N, MAS D, et al. Photocatalytic decomposition of N2O on highly dispersed Ag+ ions on TiO2 prepared by photodeposition [J]. J. Catal.,2000, 194:71-79.
[3]BOWERING N, WALKER G S, HARRISON P G. Photocatalytic decomposition and reduction reactions of nitric oxide over degussa P25 [J]. Appl. Catal. B,2006,62:208-216.
[4]Bowering N, Croston D, Harrison P G., et al. Silver modified degussa P25 for the photocatalytic removal of nitric oxide [J]. Int. J. Photoenergy,2007:1-8.
[5]MATSUOKA M, ANPO M, et al. Local structures, excited states, and photocatalytic reactivities of highly dispersed catalysts constructed within zeolites [J]. J. Photochem. Photobiol. C,2003,3:225-252.
[6]ZHANG J, HU Y, MATSUOKA M, et al. Relationship between the local structures of titanium oxide photocatalysts and their reactivities in the decomposition of NO [J]. J. Phys. Chem. B,2001,105:8395-8398.
[7]ZHANG J, MINAGAWAM, AYUSAWA T, et al. In situ investigation of the photocatalytic decomposition of NO on the Ti-HMS under flow and closed reaction systems [J]. J. Phys. Chem. B,2000,104:11501-11505.
[8]张改莲,戚慧心.汽车排气污染物的形成及危害[J].生物学通报,2000,35(6)：17-18.
[9]李英实,陈宏德.负载型汽车尾气催化剂简介[J].环境科学进展,1999,7(3)：52-61.
[10]李勤.现代内燃机排气污染物的测量与控制[M].北京：机械工业出版,1998.
[11]Parvulescu V I, Grange P, Delmon B. Catalytic removal of NO [J]. Catal. Today, 1998,46(4):233-316.
[12]毕列锋,李旭东.微生物法净化含NO废气[J].环境工程,1998,16：37-39.
[13]李晓东,杨卓如.国外氮氧化物气体治理的研究进展[J].环境工程,1996,14(2)：34-39.
[14]BOSCH H, Janssen F. Formation and control of nitrogen oxides [J]. Catal. Today, 1988,2:369-379.
[15]ARMOR N J. Environmental catalysis [J]. Appl. Catal. B,1992,1:221-256
[15]赵惠富.污染气体NOx的形成与控制[M].北京：科学出版社,1993.
[17]阮静师.降低管式炉NOx排放的途径[J].炼油设计,1996,26(5)：54-56.
[18]孔祥应.能源环境与保护[M].北京：中国科学技术出版社,1991,44-45.
[19]大连理工大学无机化学教研组.无机化学第三版(上册)[M].高等教育出版社,1990.
[20]TRUEX T J, SEARLES R A, SUN D C. Catalysts of nitrogen oxides control under lean burn conditions [J]. Platium Met. Rev.,1992,36:2-11.
[21]WALSH M P. Transport and the environmental [J]. Platium Met. Rev.,1992,36:126-134.
[22]韩才元,徐蜊厚,等.煤粉燃烧[M],北京：科学出社,2001.
[23]陈笃慧,燃煤烟气中SO2和NOx的防治[J],环保化工,1997,3：140-144.
[24]朱珍,崔洪,等.铁催化聚丙烯腈脱氮的研究[J],环境化工,1996,1：301-306.
[25]滕加伟,宋庆英,于岚,等.催化法脱除NOx的研究进展[J].环境污染治理技术与设备.2000,1(1)：38-45.
[26]SHELEF M, OTTO K, GANDHI H. The heterogeneous decomposition of nitric oxide on supported catalysts [J], Atmos. Environ.,1969,3:107-122.
[27]IWAMOTO M, FURUKAWA H, MINE Y, et al. Copper(Ⅱ) ion-exchanged ZSM-5 zeolites as highly active catalysts for direct and continuous decomposition of nirtrogen monoxide [J]. J. Chem. Soc., Chem. Commun.,1986,1272-1273.
[28]LI Y, HALL W K. Stoichiometric catalytic decomposition of nitric oxide over Cu-ZSM-5 catalysts [J]. J. Phys. Chem.,1990,94:6145-6148.
[29]GREEN T E, HINSHELWOOD C N. The catalytic decomposition of nitric oxide at the surface of platinum [J]. J. chem. soc.,1926,128:1709-1713
[30]PANCHARATNUM S, LIM K J, MASON D M. The decomposition of nitric oxide on a heated platinum wire [J]. Chem. Eng. Sci.,1975,30:781-787.
[31]AMIRNAZMI A, BOUDART M. Decomposition of nitric oxides on platinum [J]. J. Catal., 1975,39:383-394.
[32]AMIRNAZMI A, BENSON J E, BOUDART M. Oxygen inhibition in the decomposition of NO on metal oxides and platinum [J]. J. Catal.,1973,30:55-56.
[33]HANEDA M, KINTAICHI Y, NAKAMURA I, et al. Effect of surface structure of supported palladium catalysis on the activity for direct decomposition of nitrogen monoxide [J]. J. Catal.,2003,218:405-410.
[34]SAKAIDA R. R., RINKER R G, WANG Y L, et al. Catalytic decomposition of nitric oxide [J]. AIChEJ.,1961,7:658-663.
[35]OGATA A, OBUCHI A, MIZUNO K, et al. Enhancement effect of Mg2+ ion on direct nitric oxide decomposition over supported palladium catalysts [J]. Appl. Catal.,1990, 65:L11-L15.
[36]OGATA A, OBUCHI A, MIZUNO K, et al. Active sites and redox properties of supported palladium catalysts for nitric oxide direct decomposition [J]. J. Catal.,1993, 144:452-459.
[37]WU R T, CHOU T Y, YEH C T. Enhancement effect of gold and silver on nitric oxide decomposition over Pd/AlO3 catalysts [J]. Appl. Catal. B,1995,6:105-116.
[38]XIE S, ROSYNEK M P, LUNSFORD J H. Catalytic reaction of NO over 0.7%Ba/MgO catalysts [J]. J. Catal.,1999,188:24-31.
[39]ZHANG X, WATERS A B, VANNICE M A. NO decomposition and reduction by CH4 over Sr/La203 [J]. Appl. Catal. B,1996,7:321-336.
[40]SHIN S, OGAWA K, SHIMOMURA K. Catalytic decomposition of nitric oxide over brownmillerite-like compounds, calcium ferrate(III)(Ca2Fe205) and strontium ferrate(Ⅲ)(Sr2Fe2O5)[J]. Mater. Res. Bull.,1979,14:133-136.
[41]YASUDA H, MIZUNO N. Role of copper in the direct decomposition of nitrogen monoxide over well characterized La2xAxCu1-yByO4 [J]. J. Chem. Soc., Chem. Commun.,1990, 1094-1096.
[42]HANEDA M, Kintaichi Y, Hamada H. Alkali metal-dope cobalt oxide catalysts for NO decomposition [J]. Appl. Catal. B,2003,46(3):473-482.
[43]BANAS J, TOMASIC V, WESELUCHA-BIRCZYNSKA A, et al. Structural sensitivity of NO decomposition over a V-O-W/Ti(Sn)02 catalyst [J]. Catal. Today,2007,119(1-4): 199-203.
[44]TABATA K, FUKUDA H, KOHIKI S, et al. Uptake of nitric oxide gas by yttrium barium copper oxide(YBa2Cu30y) [J]. Chem. Lett.,1988,779-802.
[45]IWAMOTO M, MARUYAMA K, YAMAZOE N, et al. Study of metal oxide catalysts by temperature programmed desorption.2. chemisorption of oxygen on copper(II) ion-exchanged Y-type zeolites [J]. J. Phys. Chem.,1977,81:622-629.
[46]GIMAELLO E., MURPHY D, MAGNACCA G., et al. The interaction of NO with copper ions in ZSM-5:An EPR and IR investigation [J]. J. Catal.,1992,136:510-520.
[47]SHELF M. On the mechanism of nitric oxide decomposition over Cu-ZSM-5 [J]. Catal. Lett.1992,15:305-310.
[48]方书农,伏义路,等.Cu-ZSM-5分子筛中铜的精细结构和NO催化分解[J].催化学报,1995,16：213-216.
[49]KUCHEROV A V, GERLOCK J L, JEN H W, et al. In situ e. s.r. monitoring of the coordination and oxidation states of copper in Cu-ZSM-5 up to 500℃in flowing gas mixtures:1. Interaction with He,O2, NO, NO2 and H20 [J]. Zeolites,1995, 15:9-14.
[50]YAMASHITA H, MATSUOKA M, TSUJI K, et al. In-siut XAFS, photoluminescence and IR investigations of copper ions included within various kinds of zeolites. Structure of Cu(Ⅰ) ions and their interaction with CO molecules [J]. J. Phys. Chem.,1996, 100:397-402.
[51]于必勋,伏义路.Cu-ZSM-5上Cu位置的CO吸附红外光谱表征[J].催化学报,1995,16：38-43.
[52]蔡天锡,滕加伟.大气环境保护中的催化方法[J].化工进展,1997,3：9-14.
[53]MORIKAWA S, YOSHIDA H, TAKAHOSH T, et al. Improvement of V2O5-TiO2 catalyst for NOx reduction with NH3 in flue gases [J]. Chem. Lett.,1981, (2):251-254.
[54]BOSCH H, JANSSEN F, OLDENZLEL J, et al. The activity of supported vanadium oxide catalysts for the selective reduction of NO with ammonia [J]. Appl. Catal.,1986, 25(1-2):239-248.
[55]BOND G C, TAHIR S F. Vanadium oxide monolayer catalysts preparation characterization and catalytic activity [J]. Appl. Catal.,1991,71(1):1-31.
[56]HELD W, KOENING A, RICHTER T, et al. Catalytic NOx, reduction in net oxidizing exhaust gas [J]. SAE Paper,1990,900469.
[57]IWAMOTO M, YAHIRO H, YU-U Y, et al. Selective reduction of NO by lower hydrocarbons in the presence of O2 and SO2 over copper ion-exchanged zeolites [J]. Shokubai, 1990,32(6):430-433.
[59]LI Y, ARMOR J N. Catalytic reduction of nitrogen oxides with methane in the presence of excess oxygen [J]. Appl. Catal. B,1992,1(4):L31-L40.
[59]LI Y, ARMOR J N. Catalytic reduction of NOx with methane over metal exchange zeolites [J]. Appl. Catal. B,1993,2(2-3):239-256.
[60]JOHN N. ARMOR, FARRIS T S. The unusual hydrothermal stability of Co-ZSM-5 [J]. Appl. Catal. B,1994,4(1):L11-L17.
[61]HONDA K, FUJISHIMA A. Electrochemical photolysis of water at a semiconductor electrode [J]. Nature,1972,238:37-38.
[62]CAREY J H, TOSINE H M. Photodechlorination of PCB's in the presence of titanium dioxide in aqueous suspensions [J]. Bull. Environ. Contam. Toxicol.,1976, 16(6):697-701.
[63]魏宏斌.光催化氧化法的影响因素和发展趋势[J].上海环境科学,1995,14(3)：7-10.
[64]王春云.TiO2光催化剂大气净化涂料的开发[J].化工新型材料,1998,26(8)：29-30.
[65]YIN S, LIU B, MORIKAWA T, et al. Photocatalytic oxidation of NOx under visible LED light irradiation over nitrogen-doped titania particles with iron or platinum loading [J]. J. Phys. Chem. C,2008,112:12425-12431.
[66]WANG S, RAMAN R, CHEN B, et al. Photocatalytic oxidation of NOx using TiO2 and adsorbents [J]. Chem. Oxid,1995,5:289-302.
[67]DEVAHASDIN S, FAN C, Jr., Li K, et al. TiO2 photocatalytic oxidation of nitric oxide: transient behavior and reaction kinetics [J]. J. Photochem. Photobiol A,2003, 156:161-170.
[68]HASHIMOTO K, WASADA K, TOUKAI N, et al. Photocatalytic oxidation of nitrogen monoxide over titanium(IV) oxide nanocrystals large size areas [J]. J. Photochem. Photobiol. A,1999,136:103-109.
[69]YAMASHITA Y, AOYAMA N, TAKEZAWA N, et al. Photocatalytic conversion of NO on AgCl/Al2O3 catalyst [J]. J. Mol. Catal. A:Chem,1999,150:233-239.
[70]KUDO A, NAGAYOSHI H. Photocatalytic reduction of N20 on metal-supported TiO2 powder at room temperature in the presence of H2O and CH3OH vapor [J]. Catal. Lett.,1998, 52:109-111.
[71]HENDERSON M A, SZANYI J, PEDEN C H F. Conversion of N20 to N2 on TiO2 (110) [J]. Catal. Today,2003,85(2/4):251-266.
[72]ZHANG S, FUJIN N, NOSAKA Y. The dispersion effect of TiO2 loaded over ZSM-5 zeolite [J]. J. Mol. Catal. A:Chem,1998,129:219-224.
[73]VASENKOV S, FREI H. UV-Visible Absorption spectroscopy and photochemistry of an alkene · O2 contact charge-transfer system in large NaY crystals [J]. J. Phys. Chem. B,1997,101:4539-4543.
[74]张向华,李文钊,徐恒泳.分子筛在光催化中的应用[J].化学进展,2004,16(5)：730-734
[75]DEROUANE E G. Zeolites as solid solvents [J]. J. Mol. Catal. A:Chem,1998,134: 29-45.
[76]RAMAMURTHY V. Controlling photochemical reactions via confinement:zeolites [J]. J. Photochem. Photobiol. C,2000,1:145-166.
[77]ANDERSON M A, GRISSOM C B, et al. Increasing the heavy atom effect of xenon by adsorption to zeolites:photolysis of 2,3-diazabicyclo[2.2.2]oct-2-ene [J]. J. Am. Chem. Soc.,1996,118:9552-9556.
[78]SCAIANO J C, GARCIA H. Intrazeolite photochemistry:toward supramolecular control of molecular photochemistry [J]. Acc. Chem. Res.,1999,32:783-793.
[79]HASHIMOTO S. Zeolite photochemistry:impact of zeolites on photochemistry and feedback from photochemistry to zeolite science [J]. J. Photochem. Photobiol. C,2003,4:19-49.
[80]GARCIA H, ROTH H D. Generation and reactions of organic radical cations in zeolites [J]. Chem. Rev.,2002,102:3947-4007.
[81]HIGASHIMOTO S, NISHIMOTO K,ONO T, et al. Characterization of Fe-oxide species prepared onto ZSM-5 zeolites and their role in the photocatalytic decomposition of N20 into N2 and O2 [J]. Chem. Lett.,2000,10:1160-1161.
[82]WOO-SUNG J, MATSUOKA M, ANPO M. The photocatalytic reduction of nitrous oxide with propane on lead(Ⅱ) ion-exchanged ZSM-5 catalysts [J].Catal. Lett,2001,71, 1-2:91-93.
[83]刘守新,曲振平,韩秀文,等.Ag担载对TiO2光催化活性的影响[J].催化学报,2004,25：133-137.
[84]KANAN S M, YOUSEF I A A, ABDO N M. The photodecomposition of phosmet over UV irradiated silver nanoclusters doped in mordenite zeolite [J]. Appl. Catal. B, 2007,74:130-136.
[85]KANAN S M, KANAN M C, PATTERSON H H. Photophysical properties of Ag(I)-exchanged zeolite A and the photoassisted degradation of malathion [J]. J. Phys. Chem. B, 2001,105:7508-7516.
[86]KANAN M C, KANAN S M, AUSTIN R N, et al. Photodecomposition of carbaryl in the presence of silver-doped zeolite Y and Suwannee river natural organic matter [J]. Environ. Sci. Techno1.,2003,37:2280-2258.
[87]JACOBS P A, UYTTERHOEVEN J B, BEYER H. Cleavage water over zeolites [J]. J. Chem. Soc., Chem. Commun,1997,128
[88]OZIN G A, HUGUES F. Selective photoactivation of carbon-hydrogen bonds in paraffinic hydrocarbons. Dimerization of alkanes [J]. J. Phys. Chem.,1982, 86:5174-5179.
[89]OZIN G A, HUGUES F, MATTAR S M, et al. Low nuclearity silver clusters in faujasite-type zeolites:optical spectroscopy, photochemistry and relationship to the photodimerization of alkanes [J]. J. Phys. Chem.,1983,87:3445-3450.
[90]YOSHIDA H, HAMAJIMA T, KATO Y. Active Ag species in MFI zeolite for direct methane conversion in the light and dark [J]. Res. Chem. Intermed.2003,29(7-9):897-910.
[91]MATSUOKA M., MATSUDA E, ANPO M. The photocatalytic decomposition of nitric oxide on Ag+/ZSM-5 catalyst prepared by ion-exchange [J]. J. Mol. Catal. A:Chem.,1996, 107:399-403.
[92]ANPO M, MATSUOKA M, YAMASHITA H. In situ investigations of the photocatalytic decomposition of NO2 on ion-exchanged silver (Ⅰ) ZSM-5 catalysts [J]. Catal. Today, 1997,35:177-181.
[93]MATSUOKA M, ANPO M, WOO-SUNG. In situ characterization of the Ag'ion-exchanged zeolites and their photocatalytic activity for the decomposition of N2O into N2 and O2 at 298 K [J]. J. Photochem. Photobiol. A,2003,160:43-46.
[94]PICHAT P. Purification/deodorization of indoor air and gaseous effluents by TiO2 photocatalysis [J]. Catal. Today,2000,63:363-369.
[95]AO C H, LEE S C. Indoor air purification by photocatalyst TiO2 immobilizedon an activated carbon filter installedin an air cleaner [J]. Chem. Eng. Sci.,2005, 60(1):103-109
[96]WANG S 0. Photocatalytic oxidation of NO2 with porous TiO2 nanometer thin film [J]. Wuhan University Journal of Natural Sciences,2005,10(2):431-434.
[97]MATSUDA S, HATANO H. Photocatalytic removal of NOx in a circulating fluidized bed system [J]. Powder Technol,2005,151:61-67.
[98]COURBON H, PICHAT P. Room-temperature interaction of N180 with ultraviolet-illuminated titanium dioxide [J]. J. Chem. Soc., Faraday Trans.1 F,1984, 80:3175-3185.
[99]CALZAFERRIC G, LEIGGENER C, GLAUS S, et al. The electronic structure of Cu+, Ag+, and Au+zeolites [J], Chem. Soc. Rev.,2003,32:29-37.
[100]SHI C, CHENG M, BAO X, et al. Investigation on the catalytic roles of silver species in the selective catalytic reduction of NOx with methane [J]. Appl. Catal. B, 2004,51:171-181.
[101]BROWN D R, KEVAN L. Comparative electron spin resonance and optical absorption studies of silver-exchanged sodium Y zeolites:silver centers formed on dehydration, oxidation, and subsequent γ-irradiation [J]. J. Phys. Chem.,1986, 90(6):1129-1133.
[102]LI Z, FLYTZANI-STEPHANOPOULOS M. On the promotion of Ag-ZSM-5 by cerium for the SCR of NO by methane [J]. J. Catal.,1999,182(2):313-327.
[103]SATO K, KINTAICHI T, HANEDA M, et al. Rh-post-doped Ag/Al2O3 as a highly active catalyst for the selective reduction of NO with decane [J]. Catal. Commun,2003, 4:315-319.
[104]JANATA E. Structure of the trimer silver cluster Ag32+ [J]. J. Phys. Chem. B,2003, 107:7334-7336.
[105]BETHKE K. A, KUNG H H. Supported Ag Catalysts for the Lean Reduction of NO with C3H6 [J]. J. Catal.,1997,172:93-102.
[106]SHIMIZU K, SHIBATA J, YOSHIDA H, et al. Silver-alumina catalysts for selective reduction of NO by higher hydrocarbons:structure of active sites and reaction mechanism[J]. Appl. Catal. B.,2001,30:151-162.
[107]BAKER M D, OZIN G A, GODBER J. Far-infrared studies of silver atoms, silver ions, and silver clusters in zeolites A and Y [J]. J. Phys. Chem.,1985,89:305-311.
[108]NAGY A J, MESTL G, HEREIN D, et al. The correlation of subsurface oxygen diffusion with variations of silver morphology in the silver-oxygen system [J]. J. Catal. 1999,182(2):417-429.
[109]GELLENS L R, MORTIER W J, UYTTERHOEVEN J B. Oxidation and reduction of silver in zeolite Y:a structural study [J]. Zeolites,1981, 1(2):85-90.
