Selective conversion of 5-hydroxymethylfurfural to diketone derivatives over Beta zeolite-supported Pd catalysts in water

Conversion of 5-hydroxymethylfurfural (HMF) in water to the linear diketone derivatives 1-hydroxyhexane-2,5-dione (HHD) and 2,5-hexanedione (HXD) was investigated over a series of Beta zeolite-supported transition metal catalysts (Co, Ni, Cu, Ru, Pd). Their catalytic performance was tested in a batch stirred reactor (T = 110 °C, PH2 = 20 bar) with Pd showing the highest activity and selectivity to HHD and HXD. The effects of Pd particle size, zeolite Si/Al ratio and reaction conditions (T = 80–155 °C, PH2 = 5–60 bar) were also investigated. The incorporation of Pd into Beta zeolite by the deposition-coprecipitation method produced the most efficient catalyst, affording complete HMF conversion (T = 110 °C, PH2 = 60 bar) predominantly to HHD (68% selectivity) and HXD (8% selectivity). The combination of a bifunctional acid/redox solid catalyst and water enhances the hydrolytic ring-opening and subsequent hydrogenation of the furan ring. Catalytic activity can be partially restored by a simple regeneration treatment. This work establishes a catalytic route to produce valuable diketone derivatives from renewable furanic platform sources in water.