The preferential oxidation of CO in hydrogen rich streams over platinum doped nickel oxide catalysts

• Preferential oxidation of CO over NiO catalysts in H2 rich streams
• Effect of platinum dopant on the catalytic activity
• Platinum promoted the reduction of NiO
• Pt–Ni–Al showed higher CO conversion compared to both Ni–Al and Pt–Al
• Concentration of CO is reduced to <10 ppm over Pt–Ni–Al catalyst

NiO/Al2O3, Pt/Al2O3 and Pt/NiO/Al2O3 catalysts were prepared by the incipient wetness technique with a Ni loading of 25 wt% and Pt loading of 0.5 wt%. These catalysts were characterized by ICP-OES, XRD, BET, TPR, N2 adsorption–desorption isotherms, CO chemisorption, FTIR-CO, XPS, SEM-EDX and TEM. XRD and XPS results of the catalysts showed the presence of NiO and PtO phases on the respective supports and in situ redox reactions showed that the catalysts underwent reversible phase changes (oxide and metallic) that were stable. FTIR-CO studies showed that the Pt containing samples exhibited both linear and bridged CO adsorption with higher intensities observed for the Pt/NiO/Al2O3 catalyst. The catalysts were tested for the oxidation of CO in H2 rich streams (preferential oxidation-PROX) in a continuous flow fixed bed stainless steel reactor. The NiO/Al2O3 catalyst produced very low conversions of CO in the stipulated PROX temperature range and showed highest conversion of 11% with a selectivity of 25% toward CO2. The Pt/Al2O3 catalyst showed improved activity within the PROX temperature range with highest CO conversion of 56% and selectivity toward CO2 of 68% at 200 °C. The Pt/NiO/Al2O3 catalyst revealed synergistic effects, obtaining much higher CO conversions within the PROX temperature ranges compared to both the mono-metallic catalysts. The highest CO conversion, of 99.9%, for this catalyst was at 200 °C, with a selectivity of 72.8% toward CO2 using a C:O2 ratio of 1:2.

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