Indian Journal of Chemistry Vol. 53A, April-May 2014, pp. 511-515 Selective CO oxidation over Fe 5 (PO 4 ) 3 (OH) 5 supported Pt catalyst: Kinetic and mechanistic studies A Hari Padmasri a, *, P Anil Kumar b , S Naveen Kumar b , A Venugopal b & Sooboo Singh c a Department of Chemistry, University College for Women, Osmania University, Koti, Hyderabad 500 095, AP, India b Inorganic and Physical Chemistry, CSIR-Indian Institute of Chemical Technology, Hyderabad 500 007, AP, India c School of Chemistry, University of KwaZulu-Natal, Private Bag X54001, Durban 4000, South Africa Email: ahpadmasri@gmail.com Received 16 January 2014; revised and accepted 13 February 2014 Iron hydroxyphosphate as support for Pt catalysts is explored for preferential oxidation of CO using simulated reformate gas mixture in the temperature range 40-240 °C. The CO oxidation activity and selectivity at low reaction temperatures are enhanced on addition of H 2 O but decrease at high temperatures due to the reverse water gas shift reaction. X-ray diffraction patterns of the supported and unsupported catalysts show very weak diffraction lines due to the Fe 5 (PO 4 ) 3 (OH) 5 phase. The chemical composition of this phase on the catalyst surface has been confirmed by X-ray photoelectron spectroscopy results. Keywords: Catalysts, Supported catalysts, Platinum catalysts, Oxidation, Carbon monoxide oxidation, Iron hydroxyphosphate The production of hydrogen by steam reforming of hydrocarbons and alcohols generate far less greenhouse gas emissions than conventional fuels. Studies pertaining to hydrogen production by reforming of renewable resources such as biomass, bio-ethanol, and bio-glycerol have been reported 1,2 . However, the product stream is inevitably contaminated with 1-2% of CO, which is detrimental for hydrogen fuel cell applications. Hence, removal of CO from the reformed gas mixture is imperative. The possible methods for the removal of CO are adsorption, reduction or oxidation. Among these, selective CO removal by catalytic oxidation appears to be the most amiable approach since adsorption processes typically require unacceptably large volumes of adsorbents. The reformate gas mixture usually consists of 75% H 2 , 1-4% CO, 20-21% CO 2 and the balance is made up of nitrogen 3,4 . CO can be oxidized by water gas shift reaction (WGSR) and preferential oxidation (PROX). However, it is difficult to remove CO completely from the reformate gas by WGS catalysts, thus, eliminating its use in the fuel cell applications. On the other hand, complete removal of CO from the H 2 rich reformate gas is possible by preferential oxidation catalysts. Hence, the development of PROX catalysts has become the prime focus in recent times. Influence of H 2 O and CO 2 has been studied by Schubert et al. 5 during the PROX of CO over Au/Fe 2 O 3 catalysts. The selective CO oxidation in the presence of both H 2 and CO 2 is demanding. PROX requires the injection of a stoichiometric amount of O 2 into the gas stream for CO oxidation, and at the same time a fraction of H 2 is also consumed under the reaction conditions 6,7 . Among the several catalysts reported, Pt supported systems are claimed to be efficient for PROX 8 . Pt supported on ceria 7 , alumina 9 , silica 10 , and zeolites 11 have also been tested for the PROX reaction. It is reported that partially reducible support materials such as Fe 2 O 3 and TiO 2 for Au 12-14 and non-reducible support materials, Al 2 O 3 and SiO 2 , for Pt are active and selective for low temperature CO oxidation reaction 9 . Recently, low temperature active Pt supported on a mesoporous silica catalyst (FSM-16) showed noticeable PROX activity 15,16 . Iron based noble metal catalysts are highly active and selective for low temperature CO conversion reactions either by WGSR 9,17,18 or by selective oxidation 12,19-22 . In this study, we have studied the iron hydroxyphosphate synthesized by us earlier. 23 A simulated reformate gas mixture, i.e., 1.8% CO/N 2 , 64.1% H 2 /N 2 , 23.5% CO 2 /N 2 was used in this investigation. We report results obtained for the