Stability of monometallic Pt and Ru supported on hierarchical HZSM-5 nanosheets for hydrodeoxygenation of lignin-derived compounds in the aqueous phase

Abstract

Bio-oils obtained from the pyrolysis of lignin-derived biomass generally consist of various oxygenated compounds, eventually leading to poor quality as a fuel. Catalytic hydrodeoxygenation (HDO) is an essential step in bio-oil upgrading to increase its quality by oxygen removal in the form of water. Because water is the main solvent of a raw bio-oil, it is more practical to develop a catalytic system using water as a solvent in the HDO reaction. Herein, the stability of Pt supported on the HZSM-5 zeolite in a pressurized system (0.5–2 MPa) and in hot water (50–200 °C) was investigated. It was found that Pt supported on conventional and hierarchical ZSM-5 showed good stability in the temperature range of 50 to 150 °C and in the pressure range of 0.5 to 1 MPa. In addition, we report the catalytic performance of hydrodeoxygenation (HDO) of 4-propylphenol as a bio-oil model compound using developed monometallic Pt or Ru on HZSM-5 nanosheets compared with conventional HZSM-5 in the aqueous phase with 1 MPa of H₂ at 110 °C. The catalytic performances along with the catalytic stability under hot liquid water and pressure conditions were systematically investigated. The results clearly demonstrate that monometallic Pt/HZSM-5 exhibits almost 100% conversion of 4-propylphenol. The main products were propylcyclohexanol (∼64%, which is the hydrogenated product) and propylcyclohexane (∼30%). The catalysts are gradually degraded in the reaction for both Pt supported on conventional and hierarchical HZSM-5.