Gold-Nano Particles Supported on Na-Y and H-Y Types Zeolites: Activity and Thermal Stability for CO Oxidation Reaction
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Gold-Nano Particles Supported on Na-Y and H-Y Types Zeolites: Activity and Thermal Stability for CO Oxidation Reaction S. Jafari Æ H. Asilian Mahabady Æ H. Kazemian
Received: 22 June 2008 / Accepted: 7 October 2008 / Published online: 7 November 2008 Ó Springer Science+Business Media, LLC 2008
Abstract Gold nano particles (GNP) were deposited on Na-Y and H-Y zeolite substrates using chloroauric acid (HAuCl4) solution. The synthesized catalysts were then characterized and the catalytic activity toward CO oxidation reaction was investigated using a tubular fix bed micro reactor under atmospheric pressure. It was found that CO conversion of 100% and 5% can be achieved at 20 °C on Au/Na-Y and Au/H-Y fresh catalysts, respectively. Thermal stability of catalysts was also investigated by treating the catalysts at 400 °C for 4 h. After thermal stability test, activity tests of the catalysts at 20 °C were shown that CO conversion of Au/Na-Y catalyst was decreased to 65% whereas the activity of the Au/H-Y at 20 °C was increased up to 15%. Characterization tests were revealed that the structures of the zeolitic supports were remained unchanged after thermal pretreatment. Keywords Gold nano particle (GNP) HY NaY CO oxidation Catalyst Thermal stabilization
1 Introduction Gold did not attract much attention in heterogeneous catalysis and employed industrially because of its chemical inertness, resulting from an inability to chemisorb molecules like di-oxygen and di-hydrogen at ambient S. Jafari H. Asilian Mahabady Department of Occupational and Environmental Health, Medical Faculty, Tarbiat Modares University, Tehran, Iran H. Kazemian (&) R&D Lab. of SPAG Co., Technology Incubation Center, Sci & Technol. Park of Tehran University (UTSTP), Tehran, Iran e-mail: [email protected]
temperature. To the inertness of gold is added the absence of techniques for the dispersion of the metal comparable to those which exist for other metals traditionally used for heterogeneous catalysis and the difficulty for obtaining highly dispersed samples [1]. The application of gold catalysts to the oxidation of carbon monoxide has been studied extensively, most notably by Haruta et al. [2]. One of the significant features of gold-based catalysts is the low temperature oxidation of carbon monoxide, where the catalysts display activity at temperatures as low as -70 °C [3]. There are many factors affecting catalytic activity of gold nano particles (GNP); e.g., the size of gold nanoparticles, preparation methods, and pretreatment conditions [4]. The most important factor in the catalyst reactivity is the GNP size, which is 3 nm as an optimum size for CO oxidation reaction. Various methods have been developed in order to control the GNP size [4]. The nature of catalyst support is one of the critical parameters, which determines the catalytic activity [5]. So far, different kinds of materials have been tested as supports, e.g., active supports, such as TiO2 and Fe2O3, which can be easily reduced and passive(inert) supports such as Mg(O
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