Investigation on the impact of potassium and mild transport limitations on the pyrolysis behavior of beech wood and its macrocomponents

The existing pyrolysis mechanisms for biomass rarely take into consideration certain feedstock-specific features, such as the interaction between macrocomponents or the influence of inorganic species. This research delves deeper into the impact of potassium (K) and mild transport limitations on the pyrolytic behavior of beech wood and its biopolymers (modeled in the present work by cellulose, xylan, and alkali lignin). Special attention was given to the interactions between macrocomponents in the beech wood in comparison to their individual behavior. A combination of experimental techniques has been applied, which enabled investigation on (I) the devolatilization behavior and heats of reaction through thermogravimetric analysis/differential scanning calorimetry (TGA/DSC), (II) the in-situ evolution of functional groups in the solid thanks to diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), and the pyroylsis products composition by means of pyrolysis gas chromatography/mass spectrometry (Py-GC/MS). The interactions between the components was addressed via a five parallel-reaction kinetic model and its comparison with the commercial model compounds. Detailed information about the pyrolysis mechanistic pathways was extracted from the in-situ DRIFTS by means of a two dimensional perturbation correlation infrared spectroscopy (2D-PCIS) analysis. This technique revealed strong impact of K on cellulose, xylan, and beech wood behavior during the pyrolysis process, enhancing ring opening and dehydration reactions and hindering the formation of anhydrosugars. However, pyroylsis products of beech wood were dominated by those of lignin. It is shown that a detailed understanding on the mechanistic behavior of wood pyrolysis requires not only the understanding of the behavior of its macrocomponents but also of their interaction at a multiple level. • Combined impact of K and mild transport limitations on the pyrolysis behavior of woody biomass. • Contribution of cellulose, hemicellulose, and lignin to the pyrolysis behavior of beech wood under the combined influence of K and mild transport limitations. • In-operando investigation on the evolution of functional groups in the solid with DRIFTS.