Enhancing sustainable furan production from biomass: Influence of support cations on Pd-catalyzed furfural decarbonylation under industrially relevant conditions

This work investigates the vapor-phase decarbonylation of furfural to furan, a key platform intermediate, using Pd/γ-Al₂O₃ catalysts under conditions approaching industrial operation. Reaction parameters, including space velocity, temperature, and pressure, were systematically optimized. Although lower pressures favor catalytic activity, a compromise pressure of 10 bar was selected to facilitate downstream separation. The optimal reaction temperature was identified as 325 °C, providing high activity and near-complete selectivity toward furan. Catalyst stability was enhanced through modification of the alumina support with K, Ca, and La cations. The unmodified, Ca-, and La-modified catalysts exhibited rapid deactivation within the first 24 h on stream, whereas the K-modified catalyst showed significantly improved stability with no clear deactivation over this period. At longer times on stream, gradual deactivation was observed, mainly attributed to coke deposition. The superior performance of the K-modified catalyst is associated with reduced acidity and slight modification of palladium electronic density and dispersion. Regeneration of severely deactivated catalysts proved challenging, resulting in poor catalytic recovery. Therefore, regeneration was performed while conversion remained above 90% and selectivity above 95% to maintain process operability. Long-term catalyst lifetime was demonstrated through multiple reaction–regeneration cycles, achieving at least 200 h on stream without significant loss of activity or selectivity for the optimal formulation.