CO preferential oxidation over Rh-supported catalyst in H2-rich gas for fuel cell applications

The CO-PROX process can reduce CO concentration in hydrogenrich gases down to 10 ppmv, to avoid poisoning of PEM fuel cells electrocatalysts. Rh–based catalysts on mixed alumina + 3A zeolite support were prepared and tested in temperature range compatible with that of PEMFCs (80-100°C). In order to determine the catalyst highest oxygen selectivity toward CO oxidation with the lowest hydrogen loss, tests with decreasing feed oxygen concentration were carried out. The optimum O2 feed concentration was that corresponding to λ=O/CO=2 (selectivity equal to 0.5). At this λ value and heigher weight space velocity, an increase in the temperature range of complete CO conversion was obtained. Finally, to reduce the catalyst costs, tests at lower Rh load (from 1% to 0.5%) were carried out. No significant variations in activity resulted for 0.5% Rh-MIX catalyst, only the temperature range of complete CO conversion being slightly enhanced.