Abstract
The combustion of lean methane was studied over palladium, rhodium, platinum, and ruthenium catalysts supported on hydroxyapatite (HAP). The samples were prepared by wetness impregnation and thoroughly characterized by BET, XRD, UV-Vis-NIR spectroscopy, H2-TPR, OSC, CO chemisorption, and TEM techniques. It was found that the Pd/HAP and Rh/HAP catalysts exhibited a higher activity compared with Pt/HAP and Ru/HAP samples. Thus, the degree of oxidation of the supported metal under the reaction mixture notably influenced its catalytic performance. Although Pd and Rh catalysts could be easily re-oxidized, the re-oxidation of Pt and Ru samples appeared to be a slow process, resulting in small amounts of metal oxide active sites. Feeding water and CO2 was found to have a negative effect, which was more pronounced in the presence of water, on the activity of Pd and Rh catalysts. However, the inhibiting effect of CO2 and H2O decreased by increasing the reaction temperature.
Highlights
González-Velasco, J.R.; Gutiérrez-Ortiz, J.I.; López-Fonseca, Abstract: The combustion of lean methane was studied over palladium, rhodium, platinum, and ruthenium catalysts supported on hydroxyapatite (HAP)
We examined the suitability of HAP as a support for a series of noble metal catalysts (Pd, Rh, Pt and Ru) for the methane oxidation reaction
The methane oxidation reaction was investigated over various HAP supported noble metal catalysts
Summary
González-Velasco, J.R.; Gutiérrez-Ortiz, J.I.; López-Fonseca, Abstract: The combustion of lean methane was studied over palladium, rhodium, platinum, and ruthenium catalysts supported on hydroxyapatite (HAP). Few catalysts have demonstrated a reasonable activity and long-term stability under realistic reaction mixtures, in the presence of large amounts of H2 O (10–15%) and CO2 (10–15%), and trace levels of sulfur compounds (SO2 or H2 S) present in the exhaust gas of NG engines [4]. To address these major disadvantages, current research is focused on the use of alternative supports that present suitable interactions with the active phase [1,2,6,7,8,9]. Various promoters and bimetallic formulations have been examined to improve the activity and the resistance of the catalysts [10,11,12,13]
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