Comparison of kinetic parameters and reaction mechanisms between hardwood and softwood pyrolysis: insights from combined kinetics

The pyrolysis behavior of hardwood and softwood is important for understanding biomass conversion into biofuels and bio-based products. Traditional studies often employ a simplified single-step chemical reaction order model, overlooking the multi-stage and multi-component nature of wood pyrolysis. In this study, thermogravimetric (TG) experiments combined with inverse modeling using the combined kinetics and the master plots method were used to investigate differences in the pyrolysis mechanisms of representative hardwood and softwood. TG results reveal distinct differences in the thermal degradation of two woods, with hardwood exhibiting overlapping "shoulder" regions due to the concurrent decomposition of multi-components, while softwood displays a more uniform and concentrated decomposition pattern. The inverse modeling results capture the decomposition of three main components, revealing significantly lower activation energy and pre-exponential factor for hemicellulose and cellulose in hardwood compared to softwood, while lignin shows minimal differences between the two wood types. The key combined kinetics parameters reveal that the pyrolysis differences between hardwood and softwood are primarily due to the differing pyrolysis reaction mechanisms of hemicellulose and cellulose. Moreover, the lignin of both exhibits a high-order chemical reaction mechanism. These findings highlight the impact of wood composition on thermal degradation, offering insights for optimizing biomass conversion and biofuel production.