(521n) Selective Reduction of Alkyl-Substituted Phenols to Alkyl-Substituted Cyclohexanone over a Pd/Al2O3 Catalyst Using a Three-Phase Flow Reactor

The ability to produce high-performing polymers from renewable resources is necessary to create a sustainable plastic economy. These high-performing polymers can be made from feedstocks, such as alkyl-substituted cyclohexanones that are produced through the selective reduction of alkyl-substituted phenols obtained from lignin-derived intermediates. However, the broad range of potential lignin-derived intermediates adds complexities in processing it. Therefore, it is critical to develop a process that can accommodate the various alkyl chain and functionality in these lignin-derived intermediates. While there has been a wide range of study on the selective hydrogenation in phenolic compound, achieving high selectivity towards the desired product while maintaining high reaction activity remains a common challenge.

In this work, we demonstrated the ability to achieve high selectivity (>90%) towards various alkyl-substituted cyclohexanone using a liquid phase selective hydrogenation over a Pd/Al₂O₃ catalyst in an up-flow solid-liquid-gas phase reactor. Conversion and selectivity of the hydrogenation of phenol, p-cresol, and p-propyl-phenol was quantified to assess the reaction performance in the flow reactor system under various space velocities and hydrogen partial pressure. In addition, kinetic measurements and a stability study over time will be presented as a function of the variation of alkyl groups, metal dispersion, and different operating parameters. The results from this study provide new evidence for the ability to use mild conditions in processing complex lignin-derived materials into valuable feedstocks for high-performing polymers.