In situ structural study of manganese and iron oxide promoted rhodium catalysts for oxygenate synthesis

• Published in: Applied catalysis. A, General General, 2020-11, Vol.608, p.117845, Article 117845
• Main Authors: Carrillo, Pamela, Shi, Rui, Senanayake, Sanjaya D., White, Michael G.
• Format: Article
• Language: English
• Subjects: Carbon monoxide; Catalysts; Chemical synthesis; CO hydrogenation; Ethanol; Hydrogenation; In situ characterization; INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; Iron oxides; Manganese; Metal oxides; Oxygenate synthesis; Phase composition; Rhodium; Selectivity; X-ray diffraction
• ISSN: 0926-860X; 1873-3875
• DOI: 10.1016/j.apcata.2020.117845

[Display omitted] •Catalysts were prepared with Mn and Rh dispersed on iron oxide powders.•The MnRh/Fe2O3 catalysts exhibit a high selectivity for ethanol (∼40 %) from syn gas.•In situ x-ray studies show that high selectivity is linked to MnO and FeOx phases. In situ x-ray diffraction (XRD) and absorption spectroscopy (XAS) was used to characterize the structure and phase composition of a novel Mn and Fe double-promoted Rh-based catalyst for CO hydrogenation to oxygenates. Catalysts with different Mn:Rh molar ratios were prepared by combining Mn and Rh precursors with Fe2O3 powder, which were then calcined in air and reduced under hydrogen. The resulting MnRh/Fe2O3 catalysts are found to be highly selective for ethanol synthesis (∼40 %) for CO hydrogenation under mild conditions (∼1 bar, 240 °C). Comparison of the reactivity results with quantitative phase information from in situ XRD measurements suggest that reduced metal oxides, MnO and FeOx, and metallic Rh co-exist as active phases to promote oxygenate selectivity. The results of this work also highlight the importance of in situ characterization for extracting meaningful information on the active phases of such complex, ternary catalysts which can vary under reaction conditions.