| Stoichiometric H2 and O2 mixture diluted in helium and held below the lower explosion limit were passed over heterogeneous fixed bed catalysts. Experiments were conducted to determine relative hydrogen oxidation activity of a series of granular and/or monolithic Iridium, Palladium, Rhodium and Platinum based. Iridium catalysts were found to have the highest activity. The catalyst was studied using a reactive mixture of 5% hydrogen, 2.5% oxygen and balance helium, with exit temperature and humidity serving as basic reaction parameters. Heat loss from the reactor bed was high due to radiation effects and lack of insulation. Insulation of the bed resulted in increased thermal responses and the best-insulated system produced the highest rate of temperature and humidity change with time. The Iridium catalysts were found to deactivate after prolonged exposure to the reactive hydrogen mixtures. Hence the more stable Platinum based catalysts produced the greatest conversion at higher bed temperatures than Iridium. Although Iridium had the highest activity, when the activity was compared on long processing times with the 5% hydrogen reactive mixture, platinum demonstrated better long-term stability. |
