Selective Conversion of Syngas to Ethanol over a Tailored Supported RhFe Alloy Catalyst

Abstract

The direct conversion of syngas to ethanol is a promising route for the sustainable production of value-added chemicals and fuels. While Fe-promoted Rh-based catalysts have long been studied because of their notable activity and selectivity towards ethanol, the nature of Rh-Fe interaction and the catalyst structure under reaction conditions remain poorly understood due to the complexity of heterogeneous catalysts prepared by conventional approaches. In this work, we construct well-defined RhFe@SiO2 model catalysts via surface organometallic chemistry (SOMC), composed of small and narrowly distributed nanoparticles supported on silica. Such RhFe@SiO2 catalyst converts syngas into ethanol, reaching an overall selectivity of 38% ethanol among all products at 8.4% CO conversion, while the non-promoted Rh@SiO2 catalyst mostly yields methane (selectivity > 90%) and no ethanol. In situ X-ray absorption spectroscopy (XAS) reveals that the as-prepared RhFe@SiO2 and the catalyst under working conditions corresponds to Rh-Fe alloy with ca. 3:1 Rh/Fe ratio dispersed on SiO2 containing residual FeII single site. This unique alloyed structure promotes high ethanol selectivity.