5-Hydroxymethylfurfural Hydrodeoxygenation Coupled with Water-Gas Shift Reaction for 2,5-Dimethylfuran Production over Au/ZrO2 Catalysts

For the biomass catalytic valorization in the presence of a H2 atmosphere, large amounts of H2O and H2 are necessary to improve the processing efficiency, which resulted in the waste of such generous inputs. As a model reaction, the traditional hydrodeoxygenation of 5-hydroxymethylfurfural (5-HMF) selectively produces 2,5-dimethylfuran (2,5-DMF) under high pressure H2. Meanwhile, the water-gas shift reaction (WGSR) can counteract the harmful CO by simultaneously producing H2 from H2O. The hydrogenolysis of 5-HMF to 2,5-DMF produces H2O because of the hydroxyl group removal. Therefore, adding a trace amount of H2O to initiate 5-HMF hydrodeoxygenation coupled with WGSR to achieve H2O recycling in the reaction process is of great significance but extremely challenging. Herein, we reported a new process for the selective hydrodeoxygenation of 5-HMF to 2,5-DMF coupled with WGSR using a single catalyst, Au/ZrO2. A detailed study showed that the hydrogen species produced in situ by WGSR was used for 5-HMF hydrodeoxygenation to obtain 78.5% of 2,5-DMF yield. The H/H2O cycle in the coupling reactions exhibited a H2 utilization efficiency of 88.2%. Without using external H2, this work provided a new method for 5-HMF hydrodeoxygenation to 2,5-DMF triggered by WGSR and also showed the potential for application in H2O-saving conversion of cellulosic biomass with C–OH or C═O groups to value-added chemicals and fuels.