Selective hydrogenation of aromatic furfurals into aliphatic tetrahydrofurfural derivatives

Abstract

Tetrahydrofurfural (THFF) and 5-hydroxymethyltetrahydro-2-furaldehyde (5-HMTHFF) are important chemicals. Synthesis of THFF and 5-HMTHFF from the selective hydrogenation of furfural (FF) and 5-hydroxymethylfurfural (HMF) is highly desirable. However, it is a great challenge to hydrogenate furanyl rings while keeping CO intact. Herein, we found that Pd/LDH-MgAl-NO₃ could efficiently catalyze the hydrogenation of FF to THFF and HMF to 5-HMTHFF in water. At near complete conversion of FF and HMF, the selectivities of THFF and 5-HMTHFF could reach 92.6% and 83.7%, respectively. A series of control experiments showed that both the LDH-MgAl-NO₃ support and water solvent played an important role in the unusual performance of the catalytic system. The hydrogenation of the furanyl ring occurred on the surface of Pd. Water prohibited the hydrogenation of the CO group, and the special nature of LDH-MgAl-NO₃ prevented hydrogenation of the CO group on the support by the hydrogen spillover. Thus, the furanyl ring was selectively hydrogenated, and high selectivity of the desired product was successfully achieved. As far as we know, efficient hydrogenation of FF to THFF or HMF to 5-HMTHFF has not been reported. This work opens the way to selectively hydrogenate the furanyl ring while keeping CO in the same molecule unchanged.