采用多种物理化学手段研究了不同负载量V2O5/TiO2催化剂的VOx物种分散状态、表面酸性、可还原性及其选择性催化还原(SCR) NO性能.结果表明,V2O5在锐钛矿TiO2表面的实测单层分散容量约为1.14 mmolV/100 m2 TiO2,与“嵌入模型”的估算值相符,表明分散态的钒离子应键合在TiO2表面的八面体空位上.随着V2O5负载量的增加,V2O5/TiO2催化剂上NO转化频率(TOF)先急剧增加,至0.70 mmolV/100 m2 TiO2(略超过分散容量的一半)时达到极大(约8.3×l0-3 s-1),然后又急剧下降；同时,孤立VOx 物种可能倾向于分散在相邻的八面体空位上,且通过V-O-V化学键相连形成聚合的VOx 物种,V-O-V键所占比例增加而V-O-Ti键所占比例减小,催化剂表面单位钒离子的Br(o)nsted 酸中心量增加,故催化剂的 TOF 急剧增加.随着负载量进一步增加,虽然催化剂表面单位钒离子的Br(o)nsted酸中心量仍缓慢增加,但V-O-Ti键所占比例减少,导致钒离子的可还原性下降,另外,分散容量以上时晶相V2O5的形成也导致钒离子表面利用率下降,从而导致催化剂的TOF下降.桥式Br(o)nsted酸位(V-O(H)-V)也是SCR反应活性中心之一,不同负载量V2O5/TiO2催化剂上SCR活性与表面VOx物种的分散状态、表面酸性和钒离子可还原性密切相关.
The effect of the dispersion state and surface properties of supported vanadia on the selective catalytic reduction (SCR) activity of NO over V2O5/TiO2 catalysts was studied by various experimental techniques.The experimental monolayer dispersion capacity of V2O5 on anatase (6.86 VOx/nm2) measured by XRD was almost the same as the concentration of surface vacant sites of anatase estimated by the incorporation model,and it was suggested that isolated vanadia species tend to be dispersed on adjacent octahedral vacant sites.An increase of the NO turnover frequency (TOF) at 300 ℃ to a maximum (8.3 × 10 3 s-1) at a coverage near half a monolayer was related to the increase of the amount of weak acid sites (Br(o)nsted acid site on each vanadium ion).The TOF decreased rapidly at high VOx coverages because of a decrease of the reducibility of vanadia species and a decrease of the ratio of exposed vanadia species on the surface.The Br(o)nsted acid sites on bridging V-O(H)-V and terminal V-OH of polymeric vanadia species were all active sites in the SCR reaction.The SCR activity of the V2O5/TiO2 catalysts was related to the dispersion state,acidity,and reducibility of the vanadia species.
参考文献
| [1] | Forzatti P .[J].Applied Catalysis A:General,2001,222:221. |
| [2] | Bond G C;Tahir S F .[J].Applied Catalysis,1991,71:1. |
| [3] | Ba(n)ares M A;Wachs I E .[J].JRaman Spectrosc,2002,33:359. |
| [4] | Grzybowska-Swierkosz B .[J].Applied Catalysis A:General,1997,157:263. |
| [5] | Wachs I E;Weckhuysen B M .[J].Applied Catalysis A:General,1997,157:67. |
| [6] | Went G T;Leu L J;Bell A T .[J].Journal of Catalysis,1992,134:479. |
| [7] | Went G T;Leu L J;Rosin R R;Bell A T .[J].Journal of Catalysis,1992,134:492. |
| [8] | Baiker A;Handy B;Nickl J;Schraml-Marth M Wokaun A .[J].Catalysis Letters,1992,14:89. |
| [9] | LiettiL;Forzatti P .[J].Journal of Catalysis,1994,147:241. |
| [10] | Topsoe NY.;Dumesic JA.;Topsoe H. .VANADIA TITANIA CATALYSTS FOR SELECTIVE CATALYTIC REDUCTION (SCR) OF NITRIC OXIDE BY AMMONIA .1. COMBINED TEMPERATURE PROGRAMMED IN SITU FTIR AND ON-LINE MASS SPECTROSCOPY STUDIES[J].Journal of Catalysis,1995(1):226-240. |
| [11] | Marshneva VI.;Kalinkina OV.;Odegova GV.;Moroz EM. Lavrova GV.;Salanov AN.;Slavinskaya EM. .THE INFLUENCE OF SUPPORT ON THE ACTIVITY OF MONOLAYER VANADIA-TITANIA CATALYSTS FOR SELECTIVE CATALYTIC REDUCTION OF NO WITH AMMONIA[J].Journal of Catalysis,1995(2):171-183. |
| [12] | Alemany LJ.;Ferlazzo N.;Forzatti P.;Busca G.;Giamello E. Bregani F.;Lietti L. .REACTIVITY AND PHYSICOCHEMICAL CHARACTERISATION OF V2O5-WO3/TIO2 DE-NOX CATALYSTS[J].Journal of Catalysis,1995(1):117-130. |
| [13] | Wachs IE.;Weckhuysen BM.;Andreini A.;Vuurman MA.;Deboer M. Amiridis MD.;Deo G. .SELECTIVE CATALYTIC REDUCTION OF NO WITH NH3 OVER SUPPORTED VANADIA CATALYSTS[J].Journal of Catalysis,1996(1):211-221. |
| [14] | Reiche M.A.;Hug;P.;Baiker A. .Effect of Grafting Sequence on the Behavior of Titania-Supported V_2O_5-WO_3 Catalysts in the selective Reduction of NO by NH_3[J].Journal of Catalysis,2000(2):400-411. |
| [15] | Amiridis MD.;Deo G.;Jehng JM.;Kim DS.;Wachs IE. .REACTIVITY OF V2O5 CATALYSTS FOR THE SELECTIVE CATALYTIC REDUCTION OF NO BY NH3 - INFLUENCE OF VANADIA LOADING, H2O, AND SO2[J].Journal of Catalysis,1996(1):247-253. |
| [16] | Ni Z M;Chen A M;Fang C P;Wang L G Yu W H .[J].Journal of Physics and Chemistry of Solids,2009,70:632. |
| [17] | Tang F S;Xu B L;Shi H H;Qiu J H Fan Y N .[J].Applied Catalysis B:Environmental,2010,94:71. |
| [18] | Xie Y C;Tang Y Q .[J].Advances in Catalysis,1990,37:1. |
| [19] | Deo G;Wachs I E .[J].Journal of Catalysis,1994,146:323. |
| [20] | Wachs I E .[J].Catalysis Today,1996,27:437. |
| [21] | Primet M;Pichat P;Mathieu M V .[J].Journal of Physical Chemistry,1971,75:1216. |
| [22] | Xu B L;Fan Y N;Liu L;Lin M,Chen Y .[J].Science in China(Series B),2002,45:407. |
| [23] | Chen Y;Zhang L F .[J].Catalysis Letters,1992,12:51. |
| [24] | Dong L;Chen Y .[J].Chinese Journal of Inorganic Chemistry,2000,16:250. |
| [25] | Mutin P H;Popa A F;Vioux A;Delahay G Coq B .[J].Applied Catalysis B:Environmental,2006,69:49. |
| [26] | Giakoumelou I;Fountzoula C;Kordulis C;Boghosian S .[J].Journal of Catalysis,2006,239:1. |
| [27] | Ramis G;Busca G;Bregani F;Forzatti P .[J].Applied Catalysis,1990,64:259. |
| [28] | Ramis G;Yi L;Busca G .[J].Catalysis Today,1996,2G:373. |
| [29] | Tops(o)e N-Y .[J].Journal of Catalysis,1991,128:499. |
| [30] | Busca G;Lietti L;Ramis G;Berti F .[J].Applied Catalysis B:Environmental,1998,18:1. |
| [31] | Topsoe NY.;Topsoe H.;Dumesic JA. .VANADIA TITANIA CATALYSTS FOR SELECTIVE CATALYTIC REDUCTION OF NITRIC OXIDE BY AMMONIA .2. STUDIES OF ACTIVE SITES AND FORMULATION OF CATALYTIC CYCLES[J].Journal of Catalysis,1995(1):241-252. |
| [32] | 刘清雅,刘振宇,李成岳.NH3在选择性催化还原NO过程中的吸附与活化[J].催化学报,2006(07):636-646. |
| [33] | Bosch H;Kip B J;van Ommen J G;Gellings P J .[J].Journal of the Chemical Society,Faraday Transactions Ⅰ,1984,80:2479. |
| [34] | Busca G;Centi G;Marchetti L;Trifiro F .[J].Langmuir,1986,2:568. |
| [35] | Gheorghe C;Gee B .[J].Chemistry of Materials,2000,12:682. |
| [36] | Went G T;Oyama S T;Bell A T .[J].Journal of Physical Chemistry,1990,94:4240. |
| [37] | Miyata H;Fujii K;Ono T .[J].Journal of the Chemical Society,Faraday Transactions Ⅰ,1988,84:3121. |
| [38] | Ozkan U S;Cai Y P;Kumthekar M M .[J].Applied Catalysis A:General,1993,96:365. |
| [39] | Gasior M;Haber J;Machej T;Czeppe T .[J].JMol Catal,1988,43:359. |
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