Hydrogenation of Biomass-Derived Furfural to Tetrahydrofurfuryl Alcohol over Hydroxyapatite-Supported Pd Catalyst under Mild Conditions

Abstract

Tetrahydrofurfuryl alcohol (THFAL), as a green industrial solvent, can be obtained directly from biomass-derived furfural with 100% conversion and 100% yield over a hydroxyapatite-supported Pd catalyst (Pd-HAP) under relatively mild conditions (40 °C, 1 MPa H2, and 3 h) in 2-propanol. At room temperature and reacting for 8 h, the yield of THFAL was more than 99%. By capturing the intermediates, two pathways were proposed as follows: (1) Furfural was partially hydrogenated to furfuryl alcohol, and then, furfuryl alcohol was further hydrogenated to THFAL. (2) Furfural and 2-propanol first formed 2-(isopropoxymethyl)furan (2-IPMF) via etherification, and then, 2-IPMF was ultimately converted to THFAL. The Pd-HAP catalyst was characterized by various techniques including XRD, SEM, TEM, HAADF-STEM, XPS, and ICP-AAS. The results revealed that the outstanding catalytic performance of Pd-HAP was attributed to the quasicoordination effect between Pd and HAP, which not only contributed to highly dispersed and stable Pd nanoclusters but also led to better activation of hydrogen. The recyclability of the Pd-HAP catalyst was also investigated and proved its stability in the conversion of furfural and high selectivity toward THFAL.