Oxidative coupling of methane (OCM): Effect of noble metal (M = Pt, Ir, Rh) doping on the performance of mesoporous silica MCF-17 supported MnxOy-Na2WO4 catalysts
| Autor: | Wen-Chi Liu, Gérôme Melaet, Gabor A. Somorjai, Walter T. Ralston |
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| Rok vydání: | 2017 |
| Předmět: |
Olefin fiber
Chemistry Process Chemistry and Technology Inorganic chemistry 02 engineering and technology engineering.material Mesoporous silica 010402 general chemistry 021001 nanoscience & nanotechnology 01 natural sciences Catalysis 0104 chemical sciences Metal X-ray photoelectron spectroscopy visual_art engineering visual_art.visual_art_medium Noble metal Oxidative coupling of methane 0210 nano-technology Dispersion (chemistry) |
| Zdroj: | Applied Catalysis A: General. 545:17-23 |
| ISSN: | 0926-860X |
| Popis: | Noble metal doped M-Mn x O y -Na 2 WO 4 /SiO 2 (M = Pt, Ir, Rh) catalysts were prepared via a wet impregnation method using mesoporous silica MCF-17 as support, and their performance in the oxidative coupling of methane (OCM) was studied in a fixed-bed flow reactor. The reaction was carried out at 750 °C under atmospheric pressure with a gas feed composition of CH 4 :O 2 = 4:1. The incorporation of the noble metals yielded an enhanced selectivity towards both C 2 and C 3 hydrocarbons as compared to the undoped Mn x O y -Na 2 WO 4 /MCF-17 catalyst in the order of Rh-doped > Ir-doped > Pt-doped samples together with a lower olefin to paraffin ratio. On the other hand, the Ir-doped catalyst showed the highest overall yield for C 2 production. Elemental analysis, N 2 -adsorption, and X-ray powder diffraction (XRD) measurements confirmed similar metal loading, surface area, and phase composition for both the undoped and doped catalysts. Electron microscopy analysis showed a near-homogeneous distribution of Na and W but a higher tendency to form aggregates for Mn, with the Rh-doped catalyst being the best in overall elemental dispersion. X-ray photoelectron spectroscopy (XPS) and temperature-programmed reduction (H 2 -TPR) results indicate a more reduced nature of the surface oxide species in the noble metal doped catalysts as compared to the undoped one. They also suggest a more optimized strength of interaction between the carbon intermediates and the surface of the noble metal doped catalysts, which in combination with the improved reducibility of Mn and W species and metal dispersion, accounted for the enhanced C 2 production on the noble metal doped Mn x O y -Na 2 WO 4 /MCF-17 catalysts. |
| Databáze: | OpenAIRE |
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