CO2 pyrolysis kinetics and characteristics of lignin-rich hydrolysis residue produced from a tandem process of steam-stripping and acid hydrolysis

Huang, Yongda; Zhang, Xinghua; Zhang, Qi; Wang, Chenguang; Ma, Longlong

doi:10.1016/j.fuel.2022.123361

Cited by 4 publications

(1 citation statement)

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“…They concluded that hydroxyl-assisted hydrogen could exist in the pyrolysis of lignin. Recent researchers have found that the methoxyl groups on GS-type products can quickly lose −CH 3 radicals via homolytic mechanisms and then through H-abstraction to form CH 4 . − DFT calculations and analytical techniques suggest that lignin pyrolysis occurs through a homolysis radical mechanism.…”

Section: Introductionmentioning

confidence: 99%

Elucidating Biomass-Derived Pyrolytic Lignin Structures from Demethylation Reactions through Density Functional Theory Calculations

et al. 2023

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Pyrolytic lignin is a fraction of pyrolysis oil that contains a wide range of phenolic compounds that can be used as intermediates to produce fuels and chemicals. However, the characteristics of the raw lignin structure make it difficult to establish a pyrolysis mechanism and determine pyrolytic lignin structures. This study proposes dimer, trimer, and tetramer structures based on their relative thermodynamic stability for a hardwood lignin model in pyrolysis. Different configurations of oligomers were evaluated by varying the positions of the guaiacyl (G) and syringyl (S) units and the bonds βO4 and β5 in the hardwood model lignin through electronic structure calculations. The homolytic cleavage of βO4 bonds is assumed to occur and generate two free radical fragments. These can stabilize by taking hydrogen radicals that may be in solution during the intermediate liquid (pathway 1) formation before the thermal ejection. An alternative pathway (pathway 2) could occur when the radicals use intramolecular hydrogen, turning themselves into stable products. Subsequently, a demethylation reaction can take place, thus generating a methane molecule and new oligomeric lignin-derived molecules. The most probable resulting structures were studied. We used FTIR and NMR spectra of selected model compounds to evaluate our calculation approach. Thermophysical properties were calculated using group contribution methods. The results give insights into the lignin oligomer structures and how these molecules are formed. They also provide helpful information for the design of pyrolysis oil separation and upgrading equipment.

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Section: Introductionmentioning

confidence: 99%