Insights into the effects of varying hemicellulose and lignin ratios on cellulose pyrolysis within biomass: Kinetics and product evolution

Hemicellulose and lignin decreased the activation energy of cellulose pyrolysis by 36.7 and 22.6 kJ/mol. • Hemicellulose interacted cellulose decreased levoglucosan yield by up to 34-fold due to volatile-acid scission. • Lignin interacted cellulose enhanced levoglucosan yield by up to 77% due to thermal ejection and radical stabilization. Understanding the interactions between biomass components during pyrolysis is crucial for product control. Here, we employed a selective graded decoupling strategy to construct cellulose-hemicellulose (C-H) and cellulose-lignin (C-L) binary systems with varying ratios from pine as a typical woody biomass. Fractionation altered sample morphology from dense to porous, yet cellulose I crystallinity was retained in all samples. The effects of varying hemicellulose and lignin contents on cellulose pyrolysis were studied by thermogravimetric analysis coupled with Fourier transform infrared spectroscopy (TG-FTIR), pyrolysis–gas chromatography/mass spectrometry (Py-GC/MS), and kinetic analysis. The distributed activation energy model (DAEM) study showed that interactions with hemicellulose and lignin decreased the activation energy of cellulose pyrolysis by 36.7 and 22.6 kJ/mol, respectively. C-H interaction promoted the early evolution of CO 2 and carbonyl compounds, whereas C-L interaction enhanced the release of aromatic phenols while inhibiting the generation of hydrocarbons. C-H interaction drastically reduced levoglucosan (LGA) yield by up to 34-fold and shifted products toward small oxygenates possibly due to the random bond scission catalyzed by hemicellulose-derived acidic volatiles. In contrast, C-L interaction increased the yields of LGA and phenolic compounds by 77% and 70%, respectively. The increase in LGA may be due to a lignin-induced thermal ejection effect that facilitates its rapid escape, while the phenolic enrichment may involve radical stabilization by cellulose-derived hydrogen donors. This study reveals the distinct effects of hemicellulose and lignin on cellulose pyrolysis with biomass, providing a theoretical basis for selective valorization of lignocellulosic biomass. Download: Download high-res image (162KB) Download: Download full-size image