Characterization of pyrolytic lignin and insight into its formation mechanisms using novel techniques and DFT method

Li, Simin; Luo, Zhongyang; Wang, Wenbo; Lu, K. C.; Yang, Yi; Liang, Xiubo

doi:10.1016/j.fuel.2019.116516

Cited by 32 publications

(20 citation statements)

References 42 publications

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“…For example, Li et al, report that "simple" pyrolytic lignin monomers, dimers, and coke could be formed from the recombination of monomeric model compounds; however, "complex" oligomeric pyrolytic lignin could only be derived from the fragmentation of whole/real lignin. 86 This supports the hypothesis that oligomer products are detectable in lignin pyrolysis oil largely due to their direct vaporization during the early stages of pyrolysis. An ongoing challenge for understanding the nature of oligomer formation is the reliable collection of these products during pyrolysis and accurately analyzing them with suitable techniques.…”

Section: Methodssupporting

confidence: 78%

“…The presence of directly vaporized oligomers does not preclude the recombination of monomers into heavier species during the complicated interplay of chemical and physical processes in early pyrolysis reactions. For example, Li et al, report that “simple” pyrolytic lignin monomers, dimers, and coke could be formed from the recombination of monomeric model compounds; however, “complex” oligomeric pyrolytic lignin could only be derived from the fragmentation of whole/real lignin . This supports the hypothesis that oligomer products are detectable in lignin pyrolysis oil largely due to their direct vaporization during the early stages of pyrolysis.…”

Section: Discussionmentioning

confidence: 90%

“…Ether linkages, such as β-O-4, tend to be ∼60–70 kcal/mol, while C–C bonds tend to be ∼100 kcal/mol. − The location of a given bond in a lignin oligomeric unit can also have an impact on its dissociation enthalpy for β-O-4 homolytic cleavage . Because of bond dissociation enthalpy disparities between C–O and C–C bonds, during the early stages of pyrolysis, there should be preferential cleavage of ether linkages. , During these primary reactions (e.g., ether cleavage, demethoxylation, decarboxylation, and deacylation) that result in deoxygenation and molecular weight decreases for initial MWL, oligomers with a sufficiently low vaporization temperature are formed and subsequently devolatilized directly from the reaction front. Boiling point correlation analysis (Figure ) suggests that these oligomers should be primarily made up of lignin trimers.…”

Section: Discussionmentioning

confidence: 99%

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Vacuum Pyrolysis of Hybrid Poplar Milled Wood Lignin with Fourier Transform-Ion Cyclotron Resonance Mass Spectrometry Analysis of Feedstock and Products for the Elucidation of Reaction Mechanisms

Terrell

Garcı̀a-Pèrez

2020

Energy Fuels

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The pyrolysis of lignocellulosic materials is a promising technique to produce fuels and chemicals. It is well known that the most abundant products of lignin pyrolysis are oligomeric molecules, known as pyrolytic lignin (PL). The chemical composition of PL has been extensively studied; however, there is still an important debate whether these oligomers are produced directly from the lignin or from the recombination of monomeric pyrolytic products. Existing theories are unable to describe the effect of vacuum on the distribution of pyrolysis products. Hybrid poplar milled wood lignin (MWL) was initially isolated and thoroughly characterized by Fourier transform-ion cyclotron resonance mass spectrometry (FT-ICR MS). Chemical formulas were assigned to each oligomeric compound detected. The MWL was also subjected to vacuum pyrolysis in a modified pyroprobe at 250, 750, and 1000 mbar (absolute pressure), and the resulting liquid products were analyzed by FT-ICR MS. A new strategy to assign structural representations to the oligomeric PL products is proposed, based on the plausible pyrolysis reaction mechanisms of depolymerization/fragmentation applied to original MWL oligomer formulas. Our results support the hypothesis that PL is formed from the removal of moieties from primary lignin pyrolysis products with between three and five aromatic rings. This depolymerization/fragmentation allows the oligomers to reduce their molecular weights to the point where they can be removed from the reaction zone by direct vaporization. This phenomenon highlights the importance of pressure on removal mechanisms and their impact on the molecular weight of the resulting products from lignin pyrolysis.

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Section: Methodssupporting

confidence: 78%

Section: Discussionmentioning

confidence: 90%

Section: Discussionmentioning

confidence: 99%

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Vacuum Pyrolysis of Hybrid Poplar Milled Wood Lignin with Fourier Transform-Ion Cyclotron Resonance Mass Spectrometry Analysis of Feedstock and Products for the Elucidation of Reaction Mechanisms

Terrell

Garcı̀a-Pèrez

2020

Energy Fuels

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“…It can be concluded that the product alkylation of PZ and HZ was According to the SEM results shown in Figure S1, the micro-morphology and dispersion of raw materials with mixed catalysts had been checked, and the particle size was estimated by measuring 20 catalyst and lignin particles. Based on the characterization results from previous studies, the C-O-C linkages in KL and PL, including β-O-4 and α-O-4, had been basically destroyed, leaving only the C-C linkages [27,28]. KL had a high average molecular weight (Mw = 3930) and large particle sizes, which could reach 5 µm.…”

Section: Pyrolysis Of Raw Materialsmentioning

confidence: 99%

“…Kraft lignin was purchased from Sigma-Aldrich (St. Louis, MO, USA). Pyrolytic lignin was obtained from heavy fractions of rice straw pyrolysis bio-oils by the precipitation method, which is listed in SI and is documented in a previous work on the characterization of pyrolytic lignin [28]. All biomass materials were ground with a ball mill and sieved to over 150 meshes.…”

Section: Raw Materialsmentioning

confidence: 99%

Novel Micro-Mesoporous Composite ZSM-5 Catalyst for Aromatics Production by Catalytic Fast Pyrolysis of Lignin Residues

Wang¹,

Luo²,

Li³

et al. 2020

Catalysts

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The industrial utilization of lignocellulosic biomass is often accompanied by lots of lignin residues. Catalytic fast pyrolysis (CFP) is a high-throughput method to convert lignin to aromatics and phenolics. In order to optimize catalytic performance, conventional zeolite catalysts often need to have mesostructural modification. Here, based on hierarchical zeolite (HZ), a novel micro-mesoporous composite zeolite was obtained by redeposition under mild conditions. The conversion of two industrial lignin residues, Kraft Lignin (KL) and Pyrolytic Lignin (PL), was investigated. Interestingly, the hierarchical sample was more suitable for the case of higher concentration of primary pyrolysis products such as CFP of PL, with aromatics yield of 12.7 wt % and a monocyclic aromatic hydrocarbons (MAHs) to polycyclic aromatic hydrocarbons (PAHs) mass ratio of 4.86. The mesoporous composite zeolite possessed a better PAHs suppression capability as M/P reached 6.06, and was suitable for low reactants’ concentration and high oxygen content, such as KL CFP, with a higher aromatics yield of 3.3 wt % and M/P of 5.12. These results were compared with poplar sawdust as actual biomass, and mesoporous samples were both highly efficient catalysts with MAHs yield over 10 wt % and M/P around 5.

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Influence of different salts of alkali and alkaline earth metals on the pyrolysis of Prosopis juliflora

Saynik

Moholkar

2022

Biofuels Bioprod Bioref

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This study explores the effect of acetate, oxide and chloride salts of alkali and alkaline earth metals (AAEMs) on the pyrolysis of lignocellulosic biomass. Prosopis juliflora samples were infused using 2% acetate and chloride salts of potassium (CH 3 COOK, KCl) and the oxide and chloride salts of magnesium (MgO, MgCl 2 ). Dry impregnation technique was employed for the infusion of salts into the biomass matrix. The AAEM salt-infused biomass was pyrolyzed using a semi-batch pyrolysis reactor, and the bio-oils were characterized for variation in chemical composition using gas chromatographymass spectroscopy. The AAEM salts significantly influenced the pyrolysis process by catalyzing different degradation pathways. Potassium salts catalyzed the ring fission reactions of carbohydrates, resulting in an increase in carboxylic acid yield. On the other hand, magnesium salts promoted the cyclization of the fragmented radicals of the ring fission, resulting in enhanced furan and cycloketone yield. AAEM salts were most effective in catalyzing carbohydrate degradation pathways over the lignin degradation reactions owing to their ability to easily influence polysaccharide C-C bond cleavage over those of lignin aromatic rings. This study also revealed that the anions of AAEM salts also play a major role in biomass pyrolysis.

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Characterization of pyrolytic lignin and insight into its formation mechanisms using novel techniques and DFT method

Cited by 32 publications

References 42 publications

Vacuum Pyrolysis of Hybrid Poplar Milled Wood Lignin with Fourier Transform-Ion Cyclotron Resonance Mass Spectrometry Analysis of Feedstock and Products for the Elucidation of Reaction Mechanisms

Vacuum Pyrolysis of Hybrid Poplar Milled Wood Lignin with Fourier Transform-Ion Cyclotron Resonance Mass Spectrometry Analysis of Feedstock and Products for the Elucidation of Reaction Mechanisms

Novel Micro-Mesoporous Composite ZSM-5 Catalyst for Aromatics Production by Catalytic Fast Pyrolysis of Lignin Residues

Influence of different salts of alkali and alkaline earth metals on the pyrolysis of Prosopis juliflora

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