Abstract
NO reduction to N2 is the key reaction for efficient operation of a three-way catalytic converter (TWC). It is reported that metal catalysts Pt and Rh co-exist as individual metals in a TWC to give synergistic performance. In this article, we have studied the NO + CO reaction for a 1:1 physical mixture of silica supported Pt and Rh catalysts using fixed bed experiments and microkinetic modeling. The microkinetic model [14] for the reaction on single metals Pt and Rh is simulated for the mixture case in CHEMKIN PRO®. It is observed that the mixture maintains the activity while producing less N2O (by-product of NO + CO reaction) thus enhancing N2 selectivity inspite of having only half amount of Rh. Analysis of surface coverages on individual metals in mixture shows that in the presence of Pt, CO poisoning of Rh is reduced at lower temperature leading to better overall conversion and selectivity. This has potential benefit in automotive catalysis, as it results in the formation of significantly lower amounts of N2O, an undesirable side-product and greenhouse gas; at a lower cost than if pure Pt/Rh catalysts were used.
References
1. BurchR. Knowledge and know-how in emission control for mobile applications. Catalysis Rev Sci Eng2004;46:271–333.10.1081/CR-200036718Search in Google Scholar
2. KummerJT. Use of noble metals in automobile exhaust catalysts. J Phys Chem1986;90:4747–52.10.1021/j100411a008Search in Google Scholar
3. HuZ. A Pt–Rh synergism in pt/rh three-way catalysts. Chem Commun1996;7:879–80.10.1039/CC9960000879Search in Google Scholar
4. SchlatterJC, TaylorKC. Platinum and palladium addition to supported rhodium. J Catalysis1977;49:42–50.10.1016/0021-9517(77)90238-XSearch in Google Scholar
5. Gonzhlez-VelascoJR, BotasJA, FerretR, Guti~rrez-OrtizMA. Comparative three-way behaviour of pt, pd and rh single and combined phases in a full gas mixture with oscillating feed stream. Stud Surf Sci Catalysis1998;116:73–82.10.1016/S0167-2991(98)80865-3Search in Google Scholar
6. KociP, KubicekM, MarekM. Multifunctional aspects of three-way-catalyst: effects of complex washcoat composition. Chem Eng Res Des2004;82:284–92.10.1205/026387604772992882Search in Google Scholar
7. KoopJ, DeutschmannO. Detailed surface reaction mechanism for pt-catalysed abatement of automotive exhaust gases. Appl Catalysis B Environ2009;91:47–58.10.1016/j.apcatb.2009.05.006Search in Google Scholar
8. KwonHJ, BaikJH, KwonYT, NamI, OhSH. Detailed reaction kinetics over commercial three-way catalysts. Chem Eng Sci2007;62:5042–7.10.1016/j.ces.2007.01.082Search in Google Scholar
9. MaL, BartH, NingP, ZhangA, WuG, ZengzangZ. Kinetic study of three-way catalyst of automotive exhaust gas: modeling and application. Chem Eng J2009;155:241–7.10.1016/j.cej.2009.07.045Search in Google Scholar
10. KawaseM, FujitsukaH, NakanishiH, YoshikawaT, MiuraK. Basic reaction model of automobile exhaust gas treatment over Pt–Rh catalyst. Ind Eng Chem Res2010;49:10341–7.10.1021/ie1005564Search in Google Scholar
11. ChatterjeeD, DeutschmannO, WarnatzJ. Detailed surface reaction mechanism in a three-way catalyst. Faraday Discuss2001;119:371–84.10.1039/b101968fSearch in Google Scholar
12. GlebovLS, ZakirovaAG, BurdeinayaTN, Tret’yakovVF, MatyshakVA. Nonlinear effects in reactions of petrochemical and organic synthesis on mixtures of catalysts. Petroleum Chem2004;44:215–26.Search in Google Scholar
13. ParvulescuVI, GrangeP, DelmonB. Catalytic removal of NO. Catalysis Today1998;46:233–316.10.1016/S0920-5861(98)00399-XSearch in Google Scholar
14. MantriD, AghalayamP. Micro-kinetic study of reduction of NO on pt group catalysts. Int J Chem Reactor Eng2007;5:A1.10.2202/1542-6580.1361Search in Google Scholar
15. HaberJ, BlockJH, DelmonB. Manual of methods and procedures for catalyst characterization. Pure Appl Chem1995;67:1257–306.10.1351/pac199567081257Search in Google Scholar
16. RavatV, AghalayamP. Effect of noble metals deposition on the catalytic activity of MAPO-5 catalysts for the reduction of NO by CO. Appl Catalysis A Gen2010;389:9–18.10.1016/j.apcata.2010.08.029Search in Google Scholar
17. ChambersDC, AngoveE, NoelWC. The formation and hydrolysis of isocyanic acid during the reaction of NO, CO, and H2 mixtures on supported platinum, palladium, and rhodium. J Catalysis2001;204:11–22.10.1006/jcat.2001.3359Search in Google Scholar
18. FreyszJ, SausseyJ, LavalleyJ, BourgesyP. In situ FTIR study of the NO + CO reaction on a silica-supported platinum catalyst at atmospheric pressure using a new pulse technique. J Catalysis2001;197:131–8.10.1006/jcat.2000.3060Search in Google Scholar
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