Highly efficient and selective aqueous phase hydrogenolysis of furfural to 1,5-pentanediol using bimetallic Ru–SnOx/γ-Al2O3 catalysts†

A highly efficient and selective aqueous phase hydrogenolysis of furfural (FFald) to 1,5-pentanediol (1,5-PeD) was achieved in the presence of gamma-alumina-supported bimetallic ruthenium–tin (Ru–(x)Sn/γ-Al₂O₃; x = Sn co-loaded (wt%)) catalysts. The Ru–(x)Sn/γ-Al₂O₃ catalysts were synthesised using a coprecipitation-hydrothermal method at 150 °C for 24 h, followed by reduction with H₂ at 400 °C for 2 h. The XRD and XPS analyses confirmed the presence of Ru₃Sn₇ alloy phases, Ru⁰, Sn⁰, and oxidative tin (SnO_x) species on the sole surface of γ-Al₂O₃, which can synergistically catalyse the partial hydrogenation of CC of FFald and hydrogenolysis of C–O furan ring, thereby producing a high yield of 1,5-PeD (up to 94%) at 180 °C, under H₂ = 30 bar and after reacting for 7 h. ATR-IR spectra of the reaction mixture under controlled reaction conditions exhibited a sharp absorption peak at 1637 cm⁻¹, which was the band for trisubstituted CC in the 4,5-dihydrofuranmethanol (4,5-DHFM) intermediate. Ru–(1.30)Sn/γ-Al₂O₃ was found to be reusable with a compromising reduction in the yield of 1,5-PeD and the recoverability of the catalyst after repeated reaction run.