Condensation of lignin during heating of wood

Funaoka, Masamitsu; Kako, Tetsuya; Abe, Isao

doi:10.1007/bf01153560

Cited by 94 publications

(65 citation statements)

References 17 publications

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“…The fact that the activation energy increases most drastically for the highest treatment temperatures is in line with the fact that cross-linking reactions was not observed for milder steam treatment processes ( Martin-Sampedro et al 2011). In general, the condensation reactions of lignin increase with increasing temperature (Funaoka et al 1990). …”

Section: Resultssupporting

confidence: 56%

“…During steaming and heat treatment processes, cleavage of β-aryl ether linkages, demethylation, demethoxylation as well as formation of phenolic hydroxyl groups have been reported (Sudo et al 1985;Robert et al 1988;Li et al 2007;Martin-Sampedro et al 2011;PelaezSamaniego et al 2015). The high temperatures will also lead to an increased tendency for cross-linking reactions to occur (Funaoka et al 1990).…”

Section: Introductionmentioning

confidence: 99%

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Effects of thermo-hygro-mechanical (THM) treatment on the viscoelasticity of in-situ lignin

et al. 2017

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For producing wood products without fractures based on thermo-hygro-mechanical (THM) treatments, it is essential to understand how steaming and compression change the wood softening and cell wall components. In this paper, the effects of compression combined with steam treatment (CS) on the viscoelasticity of the in-situ lignin of Chinese fir has been investigated through dynamic mechanical analysis (DMA) under fully saturated conditions. Several variations were studied, such as the softening temperature (T g ) and apparent activation energy (ΔH a ) of the softening process in response to CS treatment conditions (such as steam temperature and compression ratio) under separate consideration of earlywood (EW) and latewood (LW). No difference between EW and LW with respect to the viscoelasticity was noted. T g and ΔH a of the lignin softening were nearly unaffected by the compression ratio, but were highly influenced by the steam temperature. The T g decreased significantly with CS treatments at or above 160 o C, but showed no appreciable change, compared to the native wood, at the lower steaming temperature of 140 o C. ΔH a increased at higher steam temperatures, while ΔH a showed a decreasing tendency with decreasing T g . This indicates that lignin undergoes a simultaneous depolymerization as well as a condensation during CS treatment.

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Section: Resultssupporting

confidence: 56%

Section: Introductionmentioning

confidence: 99%

Effects of thermo-hygro-mechanical (THM) treatment on the viscoelasticity of in-situ lignin

et al. 2017

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“…Recent studies have highlighted the technological importance of controlling the heating rate as well as the final temperature and its duration (Kocaefe et al, 2006;Rapp, 2001). The interaction between these three parameters results in more or less complete reactions of vaporization, decomposition and condensation involving the various wood components (Funaoka et al, 1990;Rousset et al, 2006). The immediate effects are changes in the physico-chemical properties of the treated wood (Arias et al, 2008;Mouras et al, 2002;Nuopponen 2005;Windeisen et al, 2007).…”

Section: Introductionmentioning

confidence: 99%

Effect of severe thermal treatment on spruce and beech wood lignins

Rousset¹,

Lapierre

Pollet

et al. 2009

Ann. For. Sci.

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Ann. For. Sci. 66 (2009) Abstract• The structure, proportion and mode of assembly of lignin, celluloses and hemicelluloses have marked effects on the reaction mechanisms during thermal treatment and therefore have a strong influence on the quality of the final product. The effect of treatment conditions, including severe conditions (up to 553 K) and treatment duration (up to 8 h) on the structure of native spruce and beech lignins was studied.• Lignin content was determined by the Klason method and lignin structure was evaluated by thioacidolysis.• The results highlighted the strong reactivity of the native spruce and beech lignins towards severe heat treatments. The distinct susceptibility of syringyl (S) and guaiacyl (G) units towards thermal treatment is confirmed by comparing the data for beech and spruce samples. The most severe treatment of spruce wood (280• C) induced a dramatic enrichment in lignin content together with the almost complete disappearance of G lignin units, whereas a more moderate treatment substantially changed lignin structure by degradation reactions that affect the p-hydroxyphenyl (H) and G lignin units similarly.• Thioacidolysis revealed that the thermal treatment induces the appearance of vinyl ether structures in spruce lignins. The decreased yield of the G and S thioacidolysis monomers reflects the progressive disappearance of G and S lignin units only involved in β-O-4 bonds and the formation of condensed linkages in proportions related to treatment severity. In severe conditions, β-O-4 linked S units are more degraded than their G homologues. Mots-clés :lignine / traitement thermique / thioacidolyse / épicéa / hêtre Résumé -Effet d'un traitement thermique sévère sur les lignines du bois d'épicéa et de hêtre.• La structure, la proportion et le mode de montage de la lignine, des celluloses et des hémicelluloses ont eu des effets marqués sur les mécanismes de la réaction au cours du traitement thermique et, par conséquent, ont eu une forte influence sur la qualité du produit final. L'effet des conditions de traitement, y compris des conditions sévères (jusqu'à 553 K) et la durée du traitement (jusqu'à 8 h) sur la structure de lignines de l'épicéa et du hêtre ont été étudiés.• La teneur en lignine a été déterminée par la méthode Klason et la structure de la lignine a été évaluée par thioacidolyse.• Les résultats ont mis en évidence la forte réactivité des lignines de l'épicéa et du hêtre vis-à-vis des traitements thermiques sévères. La sensibilité des différentes unités syringyl (S) et guaiacyl (G) vis-à-vis du traitement thermique est confirmée par comparaison des données obtenues avec les échantillons du hêtre et de l'épicéa. Le traitement le plus sévère (280• C) du bois d'épicéa a induit un enrichissement spectaculaire en lignine ainsi que la quasi-disparition des unités de la lignine G, alors qu'un traitement plus modéré a sensiblement modifié la structure de la lignine par des réactions de dégradation qui affectent les p-hydroxyphényl (H ) et les unités de lignine G.• La thio...

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“…The band at 1660 cm -1 , attributed to the stretching of conjugated aryl carbonyl (1675 cm -1 to 1660 cm -1 ), also increased, likely due to the cleavage of the α-alkyl-aryl ether bonds. However, at higher temperatures, this peak decreased as a result of reactions between α-sites of the side chains in the lignin and in the neighboring benzene nuclei, forming diphenylmethane structures (Funaoka et al 1990;Gierer 2009). An initial decrease was followed by an increase in the 1715 cm -1 band relative to the 1660 cm -1 .…”

Section: Resultsmentioning

confidence: 99%

Chemical Alterations of Pine Wood Lignin during Heat Sterilization

Kačík¹,

Luptáková²,

Šmíra³

et al. 2016

BioResources

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This study investigated alterations in the lignin of pinewood (Pinus sylvestris L.) during heat sterilization. The Klason lignin content was determined, and the dioxane lignin was isolated. Changes in the dioxane lignin were evaluated by size exclusion chromatography (SEC) as well as Fourier transform infrared (FTIR) spectroscopy. The analyses illustrated an increase in the percentage of extractives and the amount of dioxane lignin yields, while a decrease in the acid-insoluble lignin content was also observed. Changes in the macromolecular characteristics of the dioxane lignin (molecular weight and polydispersity) were not significant (p < 0.05); however, they indicated that simultaneous degradation and condensation reactions had occurred. The FTIR spectra of the dioxane lignins showed an increase at 3420 cm -1 (O-H stretching vibration), indicating the cleavage of ether bonds. The band at 1715 cm -1 (unconjugated C=O stretching) increased after an initial decrease due to the cleavage of the β-alkyl-aryl ether bonds. Also, the band at 1660 cm -1 (conjugated C=O groups) increased, which was caused by the cleavage of the α-alkyl-aryl ether bonds.

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Condensation of lignin during heating of wood

Cited by 94 publications

References 17 publications

Effects of thermo-hygro-mechanical (THM) treatment on the viscoelasticity of in-situ lignin

Effects of thermo-hygro-mechanical (THM) treatment on the viscoelasticity of in-situ lignin

Effect of severe thermal treatment on spruce and beech wood lignins

Chemical Alterations of Pine Wood Lignin during Heat Sterilization

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