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 N-2 adsorption-desorption, XRD, in situ FT-IR, CO-TPD, TPSR, and H-2-TPR. It was found that the Rh-Mn-Li catalyst supported on the SiO2 synthesized by the Stober 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 Stober 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. (C) 2012 Elsevier B.V. All rights reserved.