The catalytic properties of monometallic and bimetallic Ru and Mo phosphides were evaluated for their ability to selectively hydrogenate furfural to furfuryl alcohol. Monometallic MoP showed high selectivity (98%) towards furfuryl alcohol, while RuP and Ru 2 P exhibited lower selectivity at comparable conversion. Bimetallic promotional effects were observed with Ru 1.0 Mo 1.0 P, as the pseudo-first order reaction rate constant for furfural hydrogenation to furfuryl alcohol, k 1 , was at least 5× higher than MoP, RuP, and Ru 2 P, while maintaining a 99% selectivity. Composition-directed catalytic studies of Ru x Mo 2−x P (0.8 < x < 1.2) provided evidence that Ru rich compositions positively influence k 1 , but not the selectivity. The rate constant ratio k 1 /( k 2 + k 3 ) for furfuryl alcohol production compared to methyl furan ( k 2 ) and tetrahyrofurfuryl alcohol ( k 3 ) followed the trend of Ru 1.0 Mo 1.0 P > Ru 1.2 Mo 0.8 P > MoP > Ru 0.8 Mo 1.2 P > RuP > Ru 2 P. Diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) was used to examine the configuration of adsorbed furfural on the synthesized catalysts, but the results were inconclusive and no correlation could be found with the selectivity due to the possible IR inactive surface modes with furfural adsorption. However, gas phase density functional theory calculations suggested the x = 1.0 material in Ru x Mo 2−x P (0.8 < x < 1.2) had the most favorable furfural adsorption energy. Experimentally, we also observed that the solvent greatly influenced both the conversion and selectivity, where isopropanol provided the highest selectivity to furfuryl alcohol. Finally, recycling experiments showed a 12% decrease in k 1 after 3 cycles without any regeneration, but the activity could be fully recovered through a re-reduction step.
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Development of Molybdenum Phosphide Catalysts for Higher Alcohol Synthesis from Syngas by Exploiting Support and Promoter Effects
Molybdenum phosphide (MoP) catalysts have recently attracted attention due to their robust methanol synthesis activity from CO/CO2. Synthesis strategies are used to steer MoP selectivity toward higher alcohols by investigating the promotion effects of alkali (K) and CO‐dissociating (Co, Ni) and non‐CO‐dissociating (Pd) metals. A systematic study with transmission electron microscopy, X‐ray diffraction, X‐ray photoelectron spectroscopy, and X‐ray absorption spectroscopy (XAS) showed that critical parameters governing the activity of MoP catalysts are P/Mo ratio and K loading, both facilitating MoP formation. The kinetic studies of mesoporous silica‐supported MoP catalysts show a twofold role of K, which also acts as an electronic promoter by increasing the total alcohol selectivity and chain length. Palladium (Pd) increases CO conversion, but decreases alcohol chain length. The use of mesoporous carbon (MC) support has the most significant effect on catalyst performance and yields a KMoP/MC catalyst that ranks among the state‐of‐the‐art in terms of selectivity to higher alcohols.
- NSF-PAR ID:
- 10091087
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Energy Technology
- Volume:
- 7
- Issue:
- 5
- ISSN:
- 2194-4288
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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