Refining Surface Copper Species on Cu/SiO₂ Catalysts to Boost Furfural Hydrogenation to Furfuryl Alcohol

Controllable hydrogenation of carbonyl groups (C=O) is crucial for converting furfural into high-value furfuryl alcohol. Instead of traditional impregnation method, a novel Cu-based catalyst (Cu/SiO₂) is prepared using the ammonia evaporation method (AE) for the efficient hydrogenation of furfural to furfuryl alcohol under mild conditions. At the reaction conditions of 90 °C and 1 MPa H₂, the 5Cu/SiO₂-AE sample showed optimal performance with higher turnover frequency (36.0 h^-1) and furfuryl alcohol selectivity (>99.9%). After five cycles, the catalyst recycled still showed a high reaction activity and selectivity for furfuryl alcohol. Characterization results such as XRD, H₂-TPR, FT-IR, and XPS showed that the excellent catalytic performance of 5Cu/SiO₂-AE catalyst was attributed to the formation of layered copper silicate and the high dispersion of Cu species. Furthermore, the formation of layered copper silicate resulted in a higher ratio of Cu⁺/(Cu⁰+Cu⁺) at a reduction temperature of 250 °C, which was also responsible for the optimum activity. This work showed the importance of controllable synthesis of layered copper silicate in improving the catalytic performance of copper-containing catalyst.