Catalytic performances of Pt–Pd/CeO 2 catalysts for selective CO oxidation Apichart Parinyaswan a , Sangobtip Pongstabodee a , Apanee Luengnaruemitchai b, ∗ a Department of Chemical Technology, Faculty of Science, Chulalongkorn University, Bangkok 10330, Thailand b The Petroleum and Petrochemical College, Chulalongkorn University, Bangkok 10330, Thailand Abstract Platinum–Palladium supported on ceria catalysts has been studied for preferential oxidation of CO in the presence of hydrogen. The catalysts were prepared by impregnation method using different supports. The catalytic activity tests were performed using a fixed bed reactor in the temperature range of 50.190 ◦ C atmospheric pressure. Effects of support, ratio of Pt–Pd, O 2 concentration water vapor concentration, CO 2 concentration, and the combination of H 2 O and CO 2 in the feed stream on the catalytic performance of Pt–Pd/CeO 2 catalysts were also investigated. The experimental results showed that 1% (1:7) Pt–Pd/CeO 2 (sol–gel) exhibited higher activity than other catalysts examined. Water vapor in the feed substantially increased the activity of the catalysts, whereas CO 2 in the feed stream drastically decreased the activity of the catalysts. When both H 2 O and CO 2 were added in the feed stream, the positive effect of H 2 O is more pronounced than the negative effect of CO 2 . Keywords: Selective CO oxidation; Bimetallic; Pt; Pd; Sol–gel; CeO 2 1. Introduction In the past decade, proton exchange membrane fuel cells (PEMFC) have been extensively studied because of its high efficiency compared to conventional fossil- fuel power sources which are derived from burning petroleum products which result in pollutants such as CO 2 and CO. However, CO removal in a hydrogen- rich fuel is a critical issue when liquid hydrocarbon fu- els are used as the hydrogen source for fuel cells. A small amount of CO (∼10 ppm) in the reformed fuel strongly adsorbs on the Pt active site and deteriorates the fuel cell performance. Therefore, these small amounts ∗ Corresponding author. Tel.: +66 2 218 4148; fax: +66 2 215 4459. E-mail address: apanee.l@chula.ac.th (A. Luengnaruemitchai). of CO must be removed to less than 10 ppm before entering the fuel cell. Among the CO removal methods, the preferential oxidation of CO seems to be the most promising approach. However, in this reaction water is formed via hydrogen oxidation, reverse water gas shift and CO-methanization reactions. The side reactions are as follows: H 2 + 1 2 O 2 → H 2 O H rxn, 298 K =-242 kJ/mol, CO 2 + H 2 → CO + H 2 O H rxn, 298 K =+41.2 kJ/mol, CO + 3H 2 → CH 4 + H 2 O H rxn, 298 K =-206.2 kJ/mol. In recent years, much attention has been focused on CeO 2 -supported noble metal catalysts due to their