The solvent-free hydrogenation of butyl levulinate to γ-valerolactone and 1,4-pentanediol over skeletal Cu-Al-Zn catalyst

?-valerolactone (GVL) is a sustainable chemical, which can be obtained by hydrogenation of levulinic acid (LA) and levulinate. Herein, we reported a solvent-free hydrogenation of butyl levulinate (BL) to GVL and 1,4-pentanediol (1,4-PDO) over a skeletal Cu-Al-Zn catalyst. The skeletal Cu-Al-Zn catalyst was prepared from Devarda's alloy by alkali leaching and the catalyst was characterized by different analysis methods. The aluminum in the Devarda's alloy was dissolved by sodium hydroxide in the leaching process and many active Cu atoms were generated on the catalyst surface and the skeletal Cu-Al-Zn exhibited many micrometer-scale irregular particles with rough surface. The skeletal Cu-Al-Zn catalyst showed the excellent performance in the solvent-free hydrogenation of BL to GVL under constant hydrogen pressure (5 wt% catalyst loading, 180C, 6 MPa of H2, 6 h): the LA conversion was 100%, the GVL yield was 74.75% and the 1,4-PDO yield was 25.63%. Moreover, the catalyst showed stable performance and it was reusable up to 5 times without apparent loss of activity. A stable hydrogen pressure with Zn would suppressed the dehydration of 1,4-PDO.