Rational design of the La-doped CuCoAl hydrotalcite catalyst for selective hydrogenation of furfuryl alcohol to 1,5-pentanediol†

Abstract

1,5-Pentanediol (1,5-PeD) is an important raw material for the preparation of degradable polyesters, polyurethanes and pharmaceutical intermediates. Efficient synthesis of 1,5-PeD from biomass-derived furfuryl alcohol (FFA) by hydrogenation is a green synthetic route instead of using fossil raw material production. Nevertheless, it suffers from great challenges as the various adsorption configurations of FFA on the catalyst surface induce diverse product distributions and low selectivity for 1,5-PeD. Herein, a CuCoAl hydrotalcite catalyst modified by La was fabricated and applied in the hydrogenation of FFA to 1,5-PeD. The results demonstrated that in the catalyst doped with La via deposition–precipitation methods (La/CuCoAl-DP) there appeared a strong Cu–La interaction, and it exhibited superior activity compared with other catalysts. A near 60% yield of 1,5-PeD was achieved under 160 °C, 4 MPa H₂ within 2 h. Extensive characterizations including XRD, HRTEM, N₂O-TPD and CO₂-TPD demonstrated that the doping of La improved markedly the dispersion of Cu and the concentration of strong basic sites. Furthermore, HRTEM and the in situ XPS characterization verified that the addition of La species promoted the formation of a Cu–La interface with a stable Cuⁿ⁺–O–La(OH)₃ structure on the catalyst surface. Such Cuⁿ⁺–O–La(OH)₃ sites can simultaneously activate the furan ring and the –OH group in FFA with an intermediate six-membered ring transition state, leading to high selective cleavage of the C2–O1 bond in the furan ring to 1,5-PeD. Meanwhile, the DFT calculation results corroborated that the modifying by La species remarkably promoted the C2-end tilted adsorption of FFA on the catalyst surface and enhanced the ability of the catalyst to activate hydrogen. This study provided a new strategy for the high-value utilization of biomass resources and the development of multi-center catalysts.