Preparation and Characterization of Pt/Al-ZSM-5 Catalysts and their Reactivities for the Oxidation of CO with N 2 O at L
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Catalysis Letters Vol. 102, Nos. 3–4, August 2005 ( 2005) DOI: 10.1007/s10562-005-5847-5
Preparation and Characterization of Pt/Al-ZSM-5 Catalysts and their Reactivities for the Oxidation of CO with N2O at Low Temperatures Masaya Matsuokaa, Kiyoshi Iinoa, Haijun Chena, Yukiko Yamasakia, Gianmario Martab, Salvatore Colucciab, and Masakazu Anpoa,* a
Department of Applied Chemistry, Graduate School of Engineering, Osaka Prefecture Univerzsity, 1-1 Gakuen-cho, Sakai Osaka, 599-8531 Japan b Dipartimento di Chimica IFM, Universita di Torino, Via P. Giuria 7, 10125 Torino, Italy
Received 12 February 2005; accepted 18 March 2005
Al-ZSM-5 was prepared by treating H-ZSM-5 with an aqueous solution of Al(NO3 Þ3 and used as a support for Pt catalysts. The Pt-loaded Al-ZSM-5 acts as an efficient catalyst for CO oxidation with N2O at 273 K. TEM investigations revealed that Pt clusters with an average particle size of around 1–1.5 nm were homogeneously dispersed within Al-ZSM-5. Moreover, FT-IR and XPS analyses indicated that the small Al2O3 clusters formed within Al-ZSM-5 plays a significant role in the formation of highly dispersed Pt clusters within the pore structure of the ZSM-5 zeolite, leading to the high catalytic activity of Pt/Al-ZSM-5 as compared to Pt/ZSM-5. KEY WORDS: CO oxidation; N2O; Pt/Al-ZSM-5; Ion-exchange method.
1. Introduction The oxidation of CO on noble metal-supported catalysts have been extensively investigated for applications in various industrial processes such as selective CO oxidation in the presence of H2 [1–3] as well as for industrial and automotive pollution control [4–7]. Recent studies have shown that noble metals such as Pt, Pd, Au dispersed on easily reducible metal oxides such as TiO2 or Fe2O3 can act as efficient catalysts for CO oxidation even at ambient temperatures [8–11]. Previously, we have reported that Pt-loaded ZSM-5 (Pt/ZSM-5) catalysts prepared by a combination of ion-exchange and thermovacuum treatments exhibit high catalytic activity for the oxidation of CO with N2O at temperatures as low as 273 K [12]. Detailed characterizations of Pt/ZSM-5 have revealed that the highly dispersed Pt clusters within ZSM-5 plays an important role in the reaction. In the present study, in order to investigate methods that can enhance the efficiency and reactivity of the catalysts, H-ZSM-5 was treated with an aqueous solution of Al(NO3)3 and the resulting Al-ZSM-5 was used as a support for the Pt catalysts. Pt-loaded Al-ZSM-5 (Pt/Al-ZSM-5) was prepared by a combination of an ion-exchange method and thermovacuum treatment and its activity for CO oxidation with N2O was investigated at 273 K. Furthermore, the effect of Al(NO3)3 aqueous treatment on the chemical states of the framework Al as well as on the particle size of the Pt catalysts have been investigated by FT-IR, XPS and TEM measurements. Significant improvement of the catalytic activity of the * To whom correspondence should be addressed.
Pt-loaded catalysts through Al(NO3)3 aqueous treatment is reported here.
2. Experimental The parent H-ZSM-
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