Sonochemically Prepared high Dispersed Ru/TiO 2 Mesoporous Catalyst for Partial Oxidation of Methane to Syngas
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Catalysis Letters Vol. 103, Nos. 1–2, September 2005 ( 2005) DOI: 10.1007/s10562-005-6496-4
Sonochemically prepared high dispersed Ru/TiO2 mesoporous catalyst for partial oxidation of methane to syngas Nina Perkasa, Ziyi Zhongb, Luwei Chenb, Michele Bessonc , and Aharon Gedankena,* a
Department of Chemistry and Kanbar Laboratory for Nanomaterials at the Bar-Ilan, University Center for Advanced Materials and Nanotechnology, Bar-Ilan University, Ramat-Gan, 52900 Israel b Institute of Chemical and Engineering Sciences, 1 Pesek Road, Jurong Island, Singapore627833 c Institut de Recherches sur la Catalyse-CNRS, 2 Avenue Albert Einstein, 69626 Villeurbanne Cedex, France
Received 10 March 2005; accepted 13 May 2005
Highly dispersed Ru nanoparticles on mesoporous TiO2 have been synthesized by a one-step ultrasound assisted polyol reduction procedure. The catalysts have been characterized by XRD, TEM and HR-TEM, EDX, BET and TPR methods. It has been demonstrated that the sonochemical method reduces the Ru+3 ions creating a narrow size distribution of metallic nanoparticles deposited on the mesoporous support without damaging its pore structure. The nanoparticles of Ru are highly dispersed and stable because of their incorporation into the mesopores, and the strong metal-support interaction. The catalytic properties of Ru/TiO2(MSP) have been tested in the partial oxidation of methane, and high activity and selectivity towards CO and H2 have been demonstrated. KEY WORDS: partial methane oxidation; syngas; mesoporous support; nanoparticles; ultrasound irradiation.
1. Introduction For the production of synthesis gas in industry, steam reforming of CH4 is currently practiced. Recently catalytic partial oxidation of methane (POM) has attracted a great attention, since it is mildly exothermic and produces suitable H2/CO ratios in the final synthesis gas [1]. Supported noble metals are the main catalysts used for the POM reaction, and ruthenium has been proven as one of the best catalysts in this process because of its high activity and resistance to coking [2–4]. It has been reported already in 1996 that the Ru/TiO2 catalyst promotes the direct formation of synthesis gas without the intermediate production of CO2 and H2O, with high selectivity to CO and H2 [5]. This study [5] included the elucidation of the mechanism of this reaction pathway. The unique ability of Ru/TiO2 is attributed to the high resistance of Ru crystallites in their metallic state to oxidation under reaction conditions of (POM). It has been shown that the interaction between Ru and TiO2, inhibited the oxidation of ruthenium in the composite, promoting the direct route of synthesis gas formation [6,7]. By XRD and TPR method it has been also demonstrated that the activity and selectivity of the Ru/ Al2O3 catalysts (Ru nanoparticles 5.8 nm initial size) of high dispersion is significantly higher than with the conventionally prepared catalysts of low dispersion. The increase in the activity of the catalyst in the POM reaction is related to the shift of the eq
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