(213a) Understanding Structure–Reactivity Relationships in Biomass Pyrolysis to Enable Modeling of Sustainable Bioproducts Production

Thermochemical conversion of lignocellulosic biomass offers a promising route for producing renewable and value-added chemicals. Pyrolysis of cellulose, a major structural polysaccharide in biomass, yields levoglucosan, furanics, and low molecular weight oxygenates such as glycolaldehyde that serve as key precursors for sustainable polymers, including biodegradable polyesters and furan-based resins. Selective conversion of biomass macromolecules via pyrolysis into targeted intermediates requires a fundamental understanding of the underlying reaction mechanisms. Addressing current knowledge gaps—particularly those linking cellulose structure to product selectivity—is essential for improving the predictability of kinetic models used in reactor design and process optimization.

The current work investigates the effects of particle size and crystallinity on cellulose pyrolysis over the 400–600 °C range. Experiments were performed using Py-GC×GC-FID/TOF-MS and a customized GC system for the simultaneous quantification of low molecular weight products (LMWPs), permanent gases, and water. Crystalline cellulose with an average particle size of 50 μm yielded approximately 50–60 wt% levoglucosan (LVG), while amorphous samples with an average particle size of 15 μm produced only 10–15 wt% LVG, along with elevated yields of water and glycolaldehyde. A detailed kinetic model was used to elucidate mechanistic pathways responsible for these differences in product evolution. The results suggest that mid-chain dehydration and fragmentation reactions dominate in amorphous cellulose, leading to shorter oligomeric fragments with LVG-termini that may undergo secondary reactions to form LMWPs. These mid-chain dehydration pathways represent an alternative to classical chain-end scission mechanisms, highlighting the influence of supramolecular structure on dominant reaction routes during cellulose pyrolysis. These structure–reactivity insights inform the development of predictive kinetic models, guide pretreatment strategies, and provide critical inputs for life cycle and techno-economic assessments aimed at efficient and targeted production of biobased chemical intermediates.