-Decades of classical research on pyrolysis of lignocellulosic biomass has not yet produced a generalized formalism for design and prediction of reactor performance. Plagued by the limitations of experimental techniques such as thermogravimetric analysis (TGA) and extremely fast heating rates and low residence times to achieve high conversion to useful liquid products, researchers are now turning to molecular modeling to gain insights. This contribution briefly summarizes prior reviews along the historical path towards kinetic modeling of biomass pyrolysis and focusses on the more recent work on molecular modeling and the associated experimental efforts to validate model predictions. Clearly a new era of molecular-scale modelingdriven inquiry is beginning to shape the research landscape and influence the description of how cellulose and associated hemicellulose and lignin depolymerize to form the many hundreds of potential products of pyrolysis.

Thermochemical conversion of lignocellulosic biomass to renewable fuels and chemicals occurs through high temperature decomposition of the main structural components in plants, including cellulose, hemicellulose, and lignin. Cellulose and hemicellulose comprise mostly carbohydrates. Two disaccharides, maltose and cellobiose, are used as model compounds to explore differences in thermal stability due to the orientation of the glycosidic bond. First principles molecular dynamics and density functional theory have been used to probe the decomposition of these disaccharides during pyrolysis at 700 K. The results suggest that maltose, the α‐disaccharide, is less thermally stable. Dynamic bond length analysis for maltose indicates that several CC bonds and the CO bonds on the pyranose ring demonstrate signs of weakening, whereas no such scissile bonds were identified for cellobiose. The higher stability of the cellobiose is believed to originate from the persistence of low‐energy hydroxymethyl conformers throughout the simulation which enable strong inter‐ring hydrogen bonding. Thermogravimetric and mass spectroscopic experiments corroborate the enhanced thermal stability of cellobiose, wherein the onset of decomposition was observed at higher temperatures for cellobiose than for maltose. © 2015 American Institute of Chemical Engineers AIChE J, 61: 2562–2570, 2015

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Kinetic models for pyrolysis of switchgrass and tall fescue were obtained using thermogravimetric analysis and a newly proposed parameter-extraction methodology. The optimization strategy demonstrates the use of the Akaike information criterion for the statistical identification of the number of distinct processes and a robust global search method. The effects of sample mass, heating rates, particle size, and crystallinity index on the kinetic parameters of each feedstock were considered. For whole biomass particles, the kinetic parameters of the cellulose component was found to be similar to that of pure microcrystalline cellulose. Further particle size reduction through extensive milling reduced the activation energy of cellulose by 48%. X-ray diffraction indicated that the cellulose fraction of highly milled whole biomass becomes largely amorphous and that the amorphization of the cellulose, not the particle size reduction, is likely responsible for the decrease in activation energy.

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