Hydrogen purification for fuel cells: selective oxidation of carbon monoxide on Pt–Fe/zeolite catalysts

Abstract

A preferential oxidation of CO remaining in reformed H2 fuels (PROX) is one of the processes to avoid a serious poisoning of anode-catalysts in fuel cells. The crucial requirement for the PROX catalyst is high CO oxidation rate with high selectivity at low-temperatures of ≤200°C. We propose new Pt–Fe/mordenite catalysts for the PROX, which is extremely superior to conventional Pt/Al2O3 catalysts, even to our Pt/mordenite. TEM observation showed that the most parts of metal catalysts were loaded in mordenite molecular pores. The performances were examined in comparison with Pt/mordenite at various experimental conditions, i.e. temperature ranges (80–300°C), gas-compositions including water vapor, gas hourly space velocities (GHSV: 20,000–80,000h−1) or the compositions of metal-catalysts supported on mordenite, and found to exhibit a sufficient stability for the whole experimental period. On Pt–Fe/mordenite, we show a complete removal of CO with 100% selectivity by the addition of stoichiometric amount O2 from a simulated reformate, e.g. 1% CO, 25% CO2, 20% H2O and H2 balance, at 80–150°C with an extremely high GHSV (∼80,000h−1). FTIR and TPD data showed that CO coverage and CO bond strength on Pt are extremely lowered by the combination with Fe.