Catalytic conversion of syngas into C2+ oxygenates over Rh/SiO2-based catalysts: The remarkable effect of hydroxyls on the SiO2

A series of Rh–Mn–Li catalysts supported on SiO2 prepared by different methods were tested for the synthesis of C2+ oxygenates via CO hydrogenation. The catalysts were comprehensively characterized by N2 adsorption–desorption, XRD, in situ FT-IR, CO-TPD, TPSR, and H2-TPR. It was found that the Rh–Mn–Li catalyst supported on the SiO2 synthesized by the Stöber method exhibited the highest CO conversion and selectivity toward C2+ oxygenates compared with other catalysts. The investigation based on the catalytic performance and characterizations of the catalysts suggests that the hydroxyl–metal interaction over the catalysts supported on different SiO2 results in different desorption behavior of the adsorbed CO. The specific interaction between the active components and weakly H-bonded hydroxyls on the SiO2 prepared by the Stöber method promoted the transformation from Rh+(CO)2 to Rh–CO and facilitated the desorption/reactivity of adsorbed CO as a function of temperature in the presence of hydrogen, which were proposed to be the crucial factors for obtaining higher CO conversion and C2+ oxygenates selectivity.

Graphical abstractVarious hydroxyl groups exist on the silica supports prepared by the different methods, and have different interaction with metal particles, which finally affects the CO adsorption and results in different catalytic performance for CO hydrogenation.Figure optionsDownload full-size imageDownload high-quality image (274 K)Download as PowerPoint slideHighlights► Various hydroxyl groups exist on the SiO2 supports prepared by the different methods. ► The different hydroxyl–metal interactions affect the Rh–Mn interaction and CO adsorption. ► The weakly H-bonded hydroxyl is favorable for reactivity of the adsorbed CO. ► The increase of reactivity of the adsorbed CO results in high CO conversion.