Non-Linear Arrhenius Behavior of m-Cresol Hydrogenation over Platinum

The hydrogenation of m-cresol was studied across a wide temperature range, revealing complex variations in product distribution and reaction mechanisms. It has been found that the hydrogenation process predominantly yields 3-methylcyclohexanone and 3-methylcyclohexanol as primary products through ring hydrogenation (HYD) within the 140–250 ℃ temperature range. Conversely, the hydrodeoxygenation (HDO) products, toluene and methylcyclohexane, remain insignificant. More interestingly, the HYD yield is observed to diminish at elevated temperatures, with HDO becoming more dominant beyond 270 ℃. Further exploration of potential factors influencing the observed reduction in HYD yield at elevated temperatures—namely site deactivation, equilibrium limitations, and variations in surface coverage—revealed that changes in the surface adsorption of m-cresol play a critical role in the observed decrease in HYD activity, rather than site deactivation or equilibrium constraints. The order of 3-methylcyclohexanone formation with respect to m-cresol increases from 0 to 1 across the examined temperature range, suggesting m-cresol adsorption follows a simple Langmuir–Hinshelwood adsorption model where \(r \sim k{K}_{C}{P}_{C}/(1+{K}_{C}{P}_{C})\). This analysis not only advances our understanding of the temperature-dependent behavior in m-cresol hydrogenation but also lays the groundwork for future kinetic modeling, offering deeper insight into the complex dynamics of m-cresol hydrogenation.

Graphical Abstract