(541c) Selective Hydrogenation of Alkyl-Substituted Phenols to Alkyl-Substituted Cyclohexanone over a Pd/Al2O3 Catalyst Using a Three-Phase Flow Reactor

The creation of a sustainable plastic economy requires the ability to produce high-performing polymers from renewable resources. These high-performing polymers can be made from feedstocks obtained through the selective hydrogenation of phenols and alkyl-substituted phenols, where these alkyl-substituted phenols can be produced from renewable resources such as lignin-derived intermediates. Due to the broad range of potential lignin-intermediates, it is, therefore, critical to develop a process to study the various alkyl chain and functionality in these lignin-derived intermediates. While selective hydrogenation of phenolic compounds has been widely studied, 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 via liquid phase hydrogenation in an up-flow solid-liquid-gas phase reactor using a Pd/Al₂O₃ catalyst. The reaction performance was quantified through conversion and selectivity studies using hydrogenation of phenol, p-cresol, and p-propyl-phenol in the flow reactor system under various space velocities and hydrogen partial pressure. In addition, kinetic measurements and a stability study over time is presented as a function of the variation of alkyl groups, metal dispersion, and operating parameters. The results from this study provide new evidence for the ability to process complex lignin-derived materials under mild conditions into valuable feedstocks for high-performing polymers.