The hydrogen transfer of furfural to furfuryl alcohol with i-propanol as the hydrogen source over cation-exchanged Lewis acidic BEA zeolite has been investigated by means of density functional calculations. The reaction proceeds in three steps. First the O-H bond of i-propanol is broken to form a propoxide intermediate. After that, the furylmethoxy intermediate is formed via hydrogen transfer process, and finally furylmethoxy abstracts the proton to form the furfuryl alcohol product. The second step is rate-determining by requiring the highest activation energy (23.8 kcal/mol) if the reaction takes place on Li-Sn-BEA zeolite. We find that the catalytic activity of various cation-exchanged Sn-BEA zeolites is in the order Li-Sn-BEA > Na-Sn-BEA > K-Sn-BEA. The lower activation energy for Li-Sn-BEA compared to Na-Sn-BEA and K-Sn-BEA can be explained by the larger charge transfer from the carbonyl bond to the catalyst, leading to its activation and to the attraction of the hydrogen being transferred. The larger charge transfer in turn is due to the smaller gap between the energies of furfural HOMO and the zeolite LUMO in Li-Sn-BEA, compared to both Na-Sn-BEA and K-Sn-BEA. In a similar way, we also compare the catalytic activity of tetravalent metal centers (Sn, Zr, and Hf) substituted into BEA and find in the order Zr ≥ Hf > Sn, based on activation energies. Finally we investigate statistically which property of the reactants is a suitable descriptor for an approximative prediction of the reaction rate in order to be able to quickly screen promising catalytic materials for this reaction.

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5-Hydroxymethylfurfural (HMF) is considered as a valuable platform chemical derived from abundant sugars in a plant-based biomass. One of the most precious chemicals, which can be derived from HMF, is 2,5-furandicarboxylic acid (FDCA), which is a renewable substituent for petroleum-based terephthalic acid. Herein, the selective oxidation of HMF to FDCA and its derivatives has been accomplished using highly dispersed Pt nanoparticles supported on alkaline-exchanged hierarchical ZSM-5 nanoparticles under mild conditions (110 °C and 2.0 MPa of air) in a base-free aqueous-phase system. Interestingly, a high HMF conversion (100%) with 80% of FDCA selectivity was achieved. The synergetic effect of highly dispersed Pt nanoparticles and an alkaline-exchanged framework plays a key role, wherein they act as active oxidative sites for this multi-oxidation reaction. These findings open up prospects for the development of zeolite-based catalysts for the conversion of HMF to high value-added FDCA and its derivatives in a base-free aqueous system.

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