One-pot cascade conversion of ethyl levulinate to 1,4-pentanediol over CuZr/CoOx catalyst

Abstract

Catalytic hydrogenation of ethyl levulinate (EL) to 1,4-pentanediol (1, 4-PDO) could provide a potential approach to obtain valuable chemicals from renewable biomass. In this study, a CuZr/CoOx catalyst was developed based on a structural topotactic transformation process of layered double hydroxides. The prepared CuZr/CoOx catalysts possess a double functionality of metal-acid sites and showed superior catalytic activity in the production of 1, 4-PDO from cascade conversion of EL. A complete EL conversion (100 %) and 93.1 % 1, 4-PDO yield were obtained under optimized conditions over catalyst CuZr/CoOx-400. The co-existence of Cu0 and Cu+ on the surface of catalyst CuZr/CoOx was confirmed by XRD and XAES characterizations. In addition, the XPS results suggested a strong interaction between Co and Cu, which would effectively stabilize the Cu+ species in the catalyst. The Cu0 was believed to activate hydrogen, while the Cu+ could promote the adsorption of carbonyl group of the substrate thus facilitating the hydrogenolysis. The introducing of Zr in the catalyst greatly improved the dispersion of Cu species and increased the abundance of the acid sites as revealed by the TEM and NH3-TPD analysis. Catalyst CuZr/CoOx-400 also exhibited highly catalytic activity after five reaction cycles. Together with the low cost of the non-precious metals, the CuZr/CoOx catalysts demonstrate a potential for the scaled-up application in the biomass refinery process.