Gold-Nano Particles Supported on Na-Y and H-Y Types Zeolites: Activity and Thermal Stability for CO Oxidation Reaction S. Jafari H. Asilian Mahabady 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 (HAuCl 4 ) solution. The synthesized catalysts were then characterized and the catalytic activity toward CO oxida- tion 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. Ther- mal 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 unchan- ged 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 mole- cules like di-oxygen and di-hydrogen at ambient 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 con- ditions [4]. The most important factor in the catalyst reactivity is the GNP size, which is 3 nm as an optimum size for CO oxi- dation 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 sup- ports, e.g., active supports, such as TiO 2 and Fe 2 O 3 , which can be easily reduced and passive(inert) supports such as Mg(OH) 2 , Al 2 O 3 , silica, mesoporous materials [4, 6], activated carbon fibers [7], and zeolites [8–10]. The GNP is an active catalyst even without any high temperature pretreatments (activation). For moderately reducible support such as TiO 2 or Al 2 O 3 , hydrogen reduction at a moderately high temperature is effective. For example, the temperatures of hydrogen reduction are 373 and 473 K for Au/TiO 2 and Au/Al 2 O 3 , respectively [4], whereas for inert supports such as activated carbon, high- temperature reduction in H 2 (e.g., 673–773 K) is necessary to activate the catalyst [7]. 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: hosseinkazemian@gmail.com 123 Catal Lett (2009) 128:57–63 DOI 10.1007/s10562-008-9724-x