The catalytic transformation of furfural to cyclopentanone has been investigated using two different liquid phases as solvent: water and 30 wt.% tert–butanol in water. When using neat water at 160 °C, 40 bar of H₂, and after 2 h of reaction time, furfural polymerizes, and the yield of cyclopentanone is just 42% with a low carbon balance, indicating that furfural is transformed to non-detected by-products, likely heavy resins. When using 30 wt.% tert–butanol in water, the yield of cyclopentanone is ca. 20%, and the major product is furfuryl alcohol with a 47% yield. We have studied the catalytic transformation of the most relevant reaction intermediates in the overall conversion of furfural to cyclopentanone. In the presence of tert–butanol, two steps are inhibited in the overall pathway: (i) the Piancatelli rearrangement of furfuryl alcohol and (ii) the transformation of cyclopentenone. This inhibition is attributed to the neutralization of protons from water dissociation by surface sites on the catalyst, preventing their participation in the overall reaction. To counteract these inhibitions when tert–butanol is present, higher H₂ pressure (60 bar) and temperatures (200 °C) are required. We have been able to obtain productivities per gram of catalyst and mols of Cu basis of 411 g_prod·h⁻¹·g_cat⁻¹ and 14 g_prod·s⁻¹·mol_Cu⁻¹, respectively, which is substantially above that found for other copper-based catalysts.

This study presents a comprehensive characterization of monometallic (Co or Cu) and bimetallic (Co-Cu) catalysts supported on cerium oxide (CeO₂). XRD and TEM analyses revealed that crystallinity decreases after reduction and that metal dispersion is highly dependent on composition, with cobalt exhibiting greater dispersion than copper. The results confirmed a strong interaction between the metals and CeO₂, which alters the ceria structure and facilitates the reduction of the metal oxides. H₂-TPR and XPS data indicated that monometallic and the bimetallic 15Cu15Co catalysts achieved nearly complete reduction, whereas other bimetallic catalysts did not. Furthermore, CO chemisorption and H₂-TPD demonstrated that the hydrogen activation capacity correlates with the degree of catalyst reduction. Notably, bimetallic catalysts did not show enhanced hydrogen activation compared to their monometallic counterparts. This suggests that the dispersion and metal–support interaction are more critical factors for catalytic activity in this system than the formation of metal alloys. Although the furfural conversion was complete, the selectivity depended greatly on the catalyst composition. The 30Co_R catalyst was most selective for 1,5-pentanediol (38.4%), the 30Cu_R catalyst for 1,2-pentanediol (22.1%), and the bimetallic catalysts for THFA. Reutilising the 30Co_R catalyst after five catalytic cycles resulted in a gradual reduction in the selectivity of 1,5-pentanediol.