Effect of Water Vapor on Carbon Monoxide Oxidation over Promoted Platinum Catalysts
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Catalysis Letters Vol. 103, Nos. 3–4, October 2005 (Ó 2005) DOI: 10.1007/s10562-005-7162-6
Effect of water vapor on carbon monoxide oxidation over promoted platinum catalysts Song Ho Choa, Jong Soo Parkb, Seung Hoon Choic, Shin Kun Leea, and Sung Hyun Kima,* a Department of Chemical and Biological Engineering, Korea University, 1 Anam-Dong, Sungbuk-Ku, Seoul, 136-701, Korea Conversion Process Research Center, Korea Institute of Energy Research, P.O. Box 103, Yusong-Ku, Taejon, 305-600, Korea c Department of Environmental and Chemical Engineering, Seonam University Gwangchi-Dong, Namwon-city, Jeonbuk, 590-711, Korea b
Received 3 March 2005; accepted 2 June 2005
This study focuses on investigation of the effects of magnesium on catalyst and moisture in reactant on the catalytic activity in CO oxidation using Pt catalysts. The CO conversion rate over Pt–Mg/Al2O3 with temperature was higher than that of Pt/Al2O3. With the reactants containing moisture, the CO conversion rate over Pt–Mg/Al2O3 was significantly improved. It is observed that addition of magnesium to Pt catalysts enriches the hydroxyl group with the increase of basicity and the content of Pt0which is weakly interacted with CO. KEY WORDS: CO oxidation; Pt/Al2O3; magnesium; hydroxyl; basicity.
1. Introduction The CO oxidation has been applied in the industrial processes such as ammonia synthesis or the emission control of pollutants [1]. Recently an intensive research on the CO oxidation reaction is required because of its importance in the hydrogen purification processes for fuel cell system (preferential CO oxidation) [2]. Many researchers made efforts to enhance the rate of CO oxidation through changing a character of catalyst with promoter. Some showed their outstanding result that alkali metal oxide as promoter was helpful to CO oxidation over Pt catalyst [3,4]. They explained that the enhancement of CO oxidation rate is related to the surface electron density of Pt catalyst [5], and alkali metal promoted a generation of active oxygen on the surface of catalysts. The oxidation activity on Pt catalysts was increased by the moisture contained in the reactants too [2,6]. Though the role of moisture in CO oxidation reaction has not been clarified yet, it is recently reported the moisture has direct effects on the active sites of catalysts and improves oxidation activity. In the CO oxidation of Au catalysts [7,8], the moisture forms Au+-OH) through adsorption on Au clusters with low electron density and then Au-hydroxycarbonyl produced by the reaction of CO with Au+-OH) is oxidized by dissociated oxygen which is adsorbed on Au clusters with high electron density. For CO oxidation on Pt catalysts, the moisture makes effects on CO oxidation activity through the mechanism similar to Au catalysts. * To whom correspondence should be addressed. E-mail: [email protected]
This study is to compare the effect of moisture on CO oxidation reaction of both Pt–Mg/Al2O3 and Pt/Al2O3 catalysts.
2. Experiment 2.1. Preparation and characterization of catalyst Activated alumina
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