Researchers from the University of Limerick’s Bernal Institute, including Jacopo Lupi, Leandro Ayarde-Henríquez, Mark Kelly, and Stephen Dooley, have published a study in the Journal of Physical Chemistry A that sheds light on the thermal decomposition of hemicellulose, a major component of lignocellulosic biomass, during fast pyrolysis. Their work aims to enhance our understanding of the initial stages of this process, which is crucial for converting biomass into bio-oils and other valuable products.
Lignocellulosic biomass is a abundant renewable resource that can be converted into chemicals and fuels through various thermal processes. Fast pyrolysis is a promising technology that uses high temperatures and rapid heating rates to convert lignocellulose into bio-oils in high yields, without the need for oxygen. Hemicellulose, one of the three main components of lignocellulosic biomass, is a complex, branched structure composed of pentose, hexose sugars, and sugar acids.
The researchers focused on β-D-xylopyranose as a model structure to represent the essential chemical structure of hemicellulose. They employed advanced computational strategies rooted in quantum chemistry to investigate the gas-phase pyrolytic reactivity of β-D-xylopyranose. By using the Minnesota global hybrid functional M06-2X and the 6-311++G(d,p) Pople basis set, they computed the thermal degradation potential energy surfaces of β-D-xylopyranose. The electronic energies were further refined through DLPNO-CCSD(T)-F12 single point calculations using the cc-pVTZ-F12 basis set.
The study calculated key thermodynamic quantities such as free energies, barrier heights, enthalpies of formation, and heat capacities. Using reaction rate theory, the researchers computed rate coefficients for the initial steps of thermal decomposition. For the first time, they developed a detailed elementary reaction kinetic model for β-D-xylopyranose, targeting the initial stages of its pyrolysis. This model helps to understand the reaction kinetics, explore reactive pathways, evaluate competing parallel reactions, and selectively accept or discard pathways based on the analysis.
The practical applications of this research for the energy sector include optimizing fast pyrolysis processes to improve the yield and quality of bio-oils derived from lignocellulosic biomass. By understanding the thermal decomposition behavior of hemicellulose, researchers and engineers can develop more efficient and effective strategies for converting biomass into valuable energy products. This work contributes to the ongoing efforts to create sustainable and renewable energy solutions.
Source: Journal of Physical Chemistry A, 2023, 127, 14, 3346–3359.
This article is based on research available at arXiv.