Preferential oxidation performance of Pt-Sn/AC catalysts

Abstract

Preferential low temperature CO oxidation was studied to find out the effect of H2O, CO2, CH4 and O2 to CO ratio in the feed stream. Moreover the effect of temperature is also studied on 1% Pt-0.25%Sn/AC. The AC was HCl washed first and then oxidized with HNO3. Selective CO oxidation experiments were conducted for two sets of feed streams, with and without methane: 1% CO, 1% O2, 60% H2 and balance He; 1% CO, 1.25% O2, 60% H2 and balance He; 1% CO, 1% O2, 60% H2, 10% CO2, 15% H2O and balance He; and lastly with 1% CO, 1.25% O2, 60% H2, 10% CO2, 15% H2O and balance He. In the second part, 3% CH4 is added to the feed streams and the experiments were repeated. 250 mg catalyst is used, with 100 ml/min feed flow rate, the W/F ratio is kept constant throughout the study. Catalyst activities were tested with a Thermo 48i CO analyzer with 1 pbm sensitivity and GC at 135-125-115 and 110 °C. The results obtained from the study showed that the CO conversion levels generally increase with the increase in O2:CO ratio. The negative effect of CO2 can be offset by the addition of H2O or via changing the reaction temperature or increasing the O2:CO ratio. Temperature is found to be inversely proportional with CO conversion. Methane addition lowered the catalytic activity at higher temperatures but did not have any significant effect at lower temperatures. The best results were obtained at the feed stream concentrations of 1% CO, 1.25% O2, 60% H2 and balance He. The conversion percentage was 95 per cent at 110 °C. Most important result is obtained under the realistic methane containing feed of 1% CO, 1.25% O2, 60% H2, 10% CO2, 15% H2O, 3% CH4 and balance He. It is found that under the realistic fuel processor conditions CO conversion values were equal to the base case of 1% CO, 1% O2, 60% H2 and balance He. 88% CO conversion is achieved.