Efficient hydrodeoxygenation of lignin-derived phenols and dimeric ethers with synergistic [Bmim]PF6-Ru/SBA-15 catalysis under acid free conditions

Abstract

Selective catalytic hydrotreatment of lignin-derived phenols and dimeric ethers into alkanes is crucial for utilization of lignin and its fragments. Herein, we developed an efficient catalytic system with well-dispersed metal nanoparticles supported on SBA-15 synergistic with an ionic liquid. The catalytic system could catalyze the hydrodeoxygenation (HDO) of various monomeric and dimeric lignin-derived phenols into the corresponding alkanes under acid free conditions. The synergistic [Bmim]PF₆-Ru/SBA-15 (1-butyl-3-methylimidazolium hexafluorophosphate) catalysis exhibited the best HDO activity for lignin-derived phenols and dimeric ethers with >99.0% conversion and maximum >98.0% selectivity of the corresponding alkanes. The yield of cyclohexane from diphenyl ether was 97.7% with 100% conversion under 2 MPa H₂ at 130 °C for 6 h. The mechanism investigation confirmed that the Ru/SBA-15 catalyst and the anion of [Bmim]PF₆ played crucial roles in the hydrogenation process and deoxidization process, respectively. The catalytic system was reused six times for HDO of diphenyl ether to test its stability.