The effect of K addition on Au/activated carbon for CO selective oxidation in hydrogen-rich gas
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Catalysis Letters, Vol. 115, Nos. 1–2, May 2007 (Ó 2007) DOI: 10.1007/s10562-007-9069-x
The effect of K addition on Au/activated carbon for CO selective oxidation in hydrogen-rich gas Fang Wanga,b and Gongxuan Lua,* a
State Key Laboratory for Oxo Synthesis and Selective Oxidation, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou 730000, China b Graduate College of Chinese Academy of Sciences, Beijing 100049, China
Received 13 February 2007; accepted 16 February 2007
The effect of K addition on Au/Activated carbon (AC) catalyst for CO selective oxidation in hydrogen-rich gas was investigated in this paper. It was found that K addition resulted in activity promotion for selective CO oxidation. The results of XRD and XPS characterization indicated that K addition produced the highly dispersed Au species and retarded the sintering of Au species on the catalyst surface during the reaction. KEY WORDS: selective CO oxidation; Au; activated carbon.
1. Introduction Hydrogen, as a source of energy for stationary power plants and moving vehicles, will certainly be widely used in decades via fuel cell, for example polymer electrolyte fuel cell (PEFC). However, when hydrogen is produced via the reforming reaction, the gas always contains CO as a poisoning impurity. Therefore, the hydrogen production system must be equipped with a CO removal apparatus. Selective oxidation of CO in H2-rich gas is one of choices. Ideally, the catalyst should selectively oxidize CO to maintain its concentration less than 5 ppm while make the H2 un-reacted. Some catalysts have been reported to be active for selective oxidation of CO in H2-rich mixture, such as supported Pt [1–5], Au [6, 7], Ag [8] Cu [9], Pd, Rh catalysts [10, 11], and metal oxides catalysts [12]. The activated carbon was recently reported as support for Au catalyst in CO oxidation because of its special properties, for example, a high specific surface area(up to 3,000 m2/g), high stability in acidic and basic media [13], easy modification of textural properties and functional groups, and easy recovery of supported metals by burning off the catalyst. In fact, the Pt–Sn/ activated carbon was active for CO oxidation [14–16]. Some papers reported that the activities of Au/AC catalysts were highly dependent on pre-treatment of carbon support [17, 18]. It was known that some alkali metals exhibited significant effects of activity enhancement for CO oxidation in Pt and Pd catalysts [4, 19–24]. It is quite
*To whom correspondence should be addressed. E-mail: [email protected]
interesting to know the effect of alkali on the Au/activated carbon catalyst for CO selective oxidation. In this work, we present the observation that the dimension control of Au particle on activated carbon support by addition of K component and the activity improvement for CO selective oxidation.
2. Experimental 2.1. Preparation Au/AC catalyst was prepared by impregnation of activated carbon with the calculated amount of HAuCl4 aqueous solution. The sample was dried at 383 K for 12 h, and t
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