Aqueous-phase hydrodeoxygenation of 4-propylphenol as a lignin model to n-propylbenzene over Re-Ni/ZrO2 catalysts

• Addition of Re to Ni/ZrO2 improves the hydrodeoxygenation of 4-propylphenol.
• 54% yield of n-propylbenzene is obtained from 4-propylphenol over Re-Ni/ZrO2.
• 4-Propylphenol is hydrogenated to 4-propylcyclohexanol as a key intermediate.
• Dehydration of 4-propylcyclohexanol gives 4-propylcyclohexene.
• Subsequent dehydrogenation provides n-propylbenzene as a product.

Aqueous-phase hydrodeoxygenation of 4-propylphenol as a lignin model to n-propylbenzene was carried out over various Ni based catalysts. Among the catalysts tested, Re-Ni/ZrO2 showed the best catalytic performance. Addition of Re decreased the Ni particle size and greatly improved the catalytic activity. H2 pressure, Re to Ni ratio and reaction temperature were tuned in the optimization of reaction conditions for favorable formation of n-propylbenzene. Under the conditions of 300 °C and 4 MPa H2, the yield of n-propylbenzene reached 54% over Re-Ni/ZrO2 (Re/Ni ratio 0.33) catalyst. It is suggested that the formation of n-propylbenzene proceeds via the hydrogenation of 4-propylphenol to form 4-propylcyclohexanol, followed by the dehydration to give 4-propylcyclohexene and the subsequent dehydrogenation to n-propylbenzene.

Bimetallic Re-Ni/ZrO2 catalyzes the aqueous-phase hydrodeoxygenation of 4-propylphenol as a lignin model to n-propylbenzene with 54% yield in a batch reactor under the conditions of 300 °C and 4 MPa H2.Figure optionsDownload high-quality image (401 K)Download as PowerPoint slide