Insights into the hydrogenation reaction degradation mechanisms of lignin model compound using density functional theory methods

Lignin through pyrolysis results in a liquid byproduct that contains a significant proportion of phenolic compounds, which can be subsequently enhanced into aromatic hydrocarbons using hydrogenation methods. To comprehend the reaction mechanism of the lignin hydrogenation process, we conducted theoretical investigations on the hydrogenation reaction process of different phenolic lignin model compounds by theoretical calculation method M06-2X/6-31++G(d,p). Different potential reaction routes were developed for the hydrogenation process of lignin model compounds, and the thermodynamic and kinetic properties of key reaction steps in each pathway were computed. The calculated results indicate that the hydrogenation reaction process of lignin model compounds, the aromatic compound, CH2O, H2O, and CH3OH may be the products that emits firstly in lignin hydrogenation reaction process. And the presence of methoxyl and hydroxyl substituents on the benzene ring does not significantly impact the hydrogenation process of lignin model compounds. Furthermore, the hydrogenation reaction in lignin model compounds exhibits a high energy barrier of approximately 300.0 kJ/ mol. Thus, the hydrogenation process of lignin necessitates either appropriate modifications to the depolymerization conditions or the introduction of a catalyst. This work offers a theoretical foundation for advancing the research on lignin of hydrogenation and achieving optimal resource utilization.