Fe-promotion of supported Rh catalysts for direct conversion of syngas to ethanol

The effect of Fe–Rh alloying on CO hydrogenation to C2+ oxygenates

“…This conclusion was supported by other studies that found evidence of either Rh-Ti bonding or Rh bonding to lattice-bound oxygen in the TiO2 [8][9][10]. Subsequent transmission electron microscopy (TEM) studies suggest intimate contact of Rh and Fe through the simultaneous detection of Rh and Fe in the same particles studied using spot scans of energy-dispersive spectroscopy (EDS) [4]. The combined results of these studies suggest that direct contact of Rh with both Fe and Ti is likely to be responsible for the enhanced activity and selectivity of these bimetallic catalysts.…”

“…A catalyst where Mi is the mol% of product i detected and ni is the number of carbons in product i. This definition of selectivity follows the work of Haider et al who performed reactivity studies on similar catalyst systems [4]. As a measure of the overall activity, CO conversion (%) was also calculated for each catalyst via Eq.…”

“…The need to develop alternative sources of liquid fuels has led to renewed interest in developing catalysts for the efficient conversion of synthesis or ''syn'' gas (CO + H2), derived from biomass, coal, and natural gas, to simple alcohols and higher oxygenates [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15]. Currently, the only industrially applied process involves syngas conversion to methanol over a Cu-based catalyst (CuZnO/Al2O3) at temperatures above 500 K [1].…”

“…Various promoters (Fe, CeO2, V, La, Mn, Ag, Ti, Ir) have been shown to increase ethanol selectivity, with Fe being particularly effective due to its combined methane suppression and the enhancement of ethanol production [2][3][4][5][6]. Studies have shown that Fe loading up to 10 wt% has increased ethanol production while suppressing methane formation for Fe-promoted Rh/Al2O3 [6].…”

“…Metal dopants such as Fe are thought to improve performance by increasing the barrier for methane formation and/or decreasing the barrier for CO insertion [7]. Selectivity studies performed by Haider et al, also show that both unpromoted and Fe-promoted Rh catalysts exhibit enhanced activity and selectivity for oxygenates when the support is changed from silica to titania [4]. The authors attribute this to an increase in the number of active sites, which would be caused by increased dispersion and/or an enhanced particle-support interface.…”