Catalytic performance of Au–TiO2 catalysts prepared by deposition–precipitation for CO preferential oxidation in H2-rich gases

CO preferential oxidation (CO-PROX) can lead to a reduction of the CO content in the hydrogen-rich gas derived from hydrocarbon reforming down to at least 10 ppmv or below, so as to enable its direct feeding to standard PEM fuel cells. Au-based catalysts supported on titania were prepared and tested as potential applications in CO-PROX operating over a temperature range compatible with PEM FCs (80–100 °C).Au–TiO2 catalysts were prepared by means of two deposition–precipitation methods, varying pH (with NaOH) and some other parameters during the preparation procedure. Also the calcinations temperature was a varied parameter to evaluate the most promising catalyst.Catalyst prepared by deposition–precipitation method, using lower pH and calcined at 300 °C was found to be the most suitable one for the CO-PROX at low temperature: it reduced the inlet CO concentration below 10 ppmv within a temperature range of at least 60–80 °C.Tests at progressively lower O-to-CO feed ratio (λ) and the same WSV value were carried out for the sake of reducing H2 consumption and improve CO-PROX selectivity. For 2%Au–TiO2 the minimum λ value, ensuring a sufficiently wide temperature range of a nearly complete CO conversion at temperatures compatible with PEM FCs operation was found to be equal to 4. Tests doubling WSV were also carried out, but a complete CO conversion was not reached. Finally, CO inlet concentration was reduced to 0.5% (possible CO outlet concentration from WGS stage); parasite RWGS reaction seemed to take place leading to worse performance.