The increasing energy demand and the detrimental effects of fossil-fuel consumption demands the development of cleaner energy technologies. Ethanol is of high interest since it can be produced from biomass-derived synthesis gas (CO/CO2/H2).1 Oxide supported Rh catalysts are to date the most effective for this conversion. Rhodium surfaces enable C-C coupling but are constrained by the thermodynamically preferred production of methane.2 Rhodium can be modified by metal addition or the choice of metal oxide support to kinetically enhance ethanol selectivity.1 Studies have suggested that Mn as promoter can boost oxygenate selectivity by lowering the CO insertion barrier into CHx species.3 This leads to CHxCO intermediates that ultimately govern the formation of oxygenates.2 Our previous in situ studies of Fe-promoted Rh catalysts supported on CeO2 and TiO2 found that increased ethanol selectivity is accompanied by the presence of FeRh alloy and a FeOx phase.4,5 In this work, we explore the promotional effects of Mn and Fe on Rh/TiO2 and Rh/nano-Fe2O3 catalysts. The synthesized catalysts were tested and characterized using transmission electron microscopy (TEM), X-ray diffraction (XRD), and X-ray absorption spectroscopy (XAS). Our results suggest that Mn modifies the CO hydrogenation mechanism on Rh surfaces by limiting hydrogenation activity while boosting CO insertion that leads to higher oxygenate formation.

Manganese promotion of rhodium-based nanocatalysts

254th National Meeting (2017)

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