Novel noble metal-free and recyclable Co-CoOx-FeNiCo/γ-Al2O3 catalyst for selective hydrogenation of 5-hydroxymethylfurfural to 2,5-dimethyl-furan or 2,5-Bis(hydroxymethyl)furan

The efficient production of the liquid fuel 2,5-dimethylfuran (DMF) from biomass-derived 5-hydroxymethylfurfural (HMF) is very complicated because of the presence of the aldehyde group, hydroxyl group, and C=C bond. In this study, a novel Co-CoOx -FeNiCo/gamma-Al2O3 catalyst was developed for selective hydrogenation of HMF to DMF. The catalyst was characterized by using XRD, TEM, SAED, BET, XPS, NH3-TPD, and H-2-TPR techniques. The catalyst reduced at 500 degrees C exhibited excellent catalytic performance and the highest DMF yield (>99.9%) was obtained at 190 degrees C and 4 h. During the reaction, metal sites selectively hydrogenated the C=O bond while acid sites (CoOx acid sites) selectively hydrogenolyzed C-O bond. Appropriate surface acidity of the catalyst and the balance between metal and metal oxide species are the main factors for achieving a high yield of DMF. At reaction temperatures below 150 degrees C, DMF was not produced and HMF has completely converted into 2,5-Bis (hydroxymethyl)furan (BHMF), an important furan diol for polymers production. 100% BHMF yield was also obtained for the HMF hydrogenation over 300 degrees C reduced catalysts due to the high concentration of strong acid sites. The catalyst recyclability exhibited excellent stability and the original activity was maintained after six reuses. A reaction mechanism was also proposed.

Automated summary

A novel catalyst was developed for the selective hydrogenation of HMF to DMF. The catalyst exhibited excellent catalytic performance and high DMF yield under suitable reaction conditions. The surface acidity of the catalyst and the balance between metal and metal oxide species were found to be crucial for achieving a high yield of DMF.