Effects of promoters on selective CO oxidation in hydrogen-rich streams over Pt/Al2O3 catalysts

Abstract

The objective of this study was to investigate the second promoter effects on Pt-X- Ce/Al2O3 and Pt-Co-Y/Al2O3 catalyst for selective CO oxidation. Seven promoters were tested in two groups; Ni, K and Co as one group (as X) were coupled with ceria, while Ce, Mg, Mn, Fe and Zr as second goup (as Y) were coupled with Co. All catalyst prepared by wetness impregnation method with 1.25wt.% promoter and 1.4 or 0.7%wt.% platinum. Three different gas streams are used for experiments; one without CO2 and H2O, one with 25% CO2 but no H2O and with both 25% CO2 and 10% H2O. All the feed streams contained 1% CO, 1% O2, 60% H2, and He as balance. Co is found to be the best second promoter for Pt-X-Ce/Al2O3 catalyst at 80 and 110 °C for 1.4 wt.% Pt in the absence of CO2 and H2O. For Pt-Co-Y/Al2O3, Fe and Mn addition decreased the CO conversion, where the others has no significant effect at 80 °C. At 110 °C second promoter has increased the conversion rate to 100% from 97-98%. Then the tests over Pt-Co-Y/Al2O3 catalysts were also performed using 0.7 wt.% Pt. at 110 °C for all reaction streams. At 110 °C, all catalysts exhibit promosing activities, except Fe and Zr containing ones. Among these tests Pt-Co-Mg/Al2O3 was found to be slightly better than others. The increases of temperature to 130 °C did not increase the conversion, on the contrary it decreased CO conversion in all catalysts. However, the increase of Pt content to1 wt.% which is tested in Pt-Co-Mg/Al2O3 at 110 °C resulted 100% CO conversion for 2 hours period without any deactivation in the presence of CO2 and H2O in the feed.