Structural Characterization of the Bark and Core Lignins from Kenaf (<i>Hibiscus cannabinus</i>)

Seca, Ana M. L.; Cavaleiro, José A. S.; Domingues, M. Fátima; Silvestre, Armando J. D.; Evtuguin, Dmitry; Neto, Carlos Pascoal

doi:10.1021/jf9801320

Cited by 38 publications

(36 citation statements)

References 22 publications

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“…Seca et al 10 isolated the dioxane and milled wood lignins (MWLs) from the core and dioxane lignin from the bark of kenaf, which showed that large differences in chemical composition exist between in situ and isolated lignins of kenaf. That is, both the core and bast in situ lignins are rich in the guaiacyl lignin units, whereas the lignins isolated from the core and bast are rich in the syringy lignin units.…”

Section: Introductionmentioning

confidence: 99%

The isolation and characterization of lignin of kenaf fiber

Yan

2009

J of Applied Polymer Sci

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In this article, milled wood lignin (MWL) was isolated and purified from retted kenaf fiber, the lignin obtained was characterized by elemental analysis, FTIR, 1 H-NMR, and 13 C-NMR spectroscopy. The C 9 formula is calculated for kenaf fiber MWL as C 9 H 9.32 O 3.69 (OCH 3 ) 1.30 . The spectra of FTIR, 1 H-NMR, and 13 C-NMR show the kenaf fiber lignin to be of the G/S type with high proportion of syringyl (S) unit. The numbers of phenolic and aliphatic hydroxyl groups in the kenaf fiber MWL are estimated to be 0.14 and 1.31, respectively, per C 9 unit. The OH aliph is 90.3% in total numbers of hydroxyl groups of kenaf fiber MWL, and the OH ph is 9.7%. It is evident that the b-O-4 structures are mainly linkage in the MWL of kenaf fiber, which contain more erythro stereochemistry type in b-O-4 units than thero stereochemistry type. In general, the characteristics of lignin of kenaf fiber are similar to that of hardwood.

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Section: Introductionmentioning

confidence: 99%

The isolation and characterization of lignin of kenaf fiber

Yan

2009

J of Applied Polymer Sci

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“…In the 13 C-NMR spectra of RL and ILL, the characteristic tertiary carbon resonances from syringylpropane (S) (signals centered at 104.9 ppm) and guaiacylpropane (G) units (signals centered at 111.5 ppm and 119.3 ppm) were observed. The approximately calculated S/G ratios for RL, ILL1, and ILL2 lignins were 1.14, 0.90, and 0.96, respectively, which showed that the RL was richer in syringyl content than the ILL (Seca et al 1998). This may result from the demethoxylation of S units.…”

Section: Nuclear Magnetic Resonance Spectroscopymentioning

confidence: 92%

Structural Changes of Lignin after Ionic Liquid Pretreatment

et al. 2017

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Changes of lignin's structure were investigated resulting from an ionic liquid ([Bmim]Cl,1-butyl-3-methylimidazolium chloride salt) pretreatment. The purified lignin was pretreated by [Bmim]Cl under the following conditions: the ionic liquid to lignin mass ratio was 10:1, the temperature was 85 °C, and the processing time was 2 h and 4 h. The chemical structure of lignin was studied via Ultraviolet (UV) spectra, Fourier Transform infrared (FT-IR) spectra, Nuclear Magnetic Resonance Spectroscopy ( 13 C-NMR), Gel Permeation Chromatography (GPC), X-ray photoelectron spectroscopy (XPS), and Thermogravimetric Analysis (TG). The total content of phenolic hydroxyl increased with increased time. Moreover, the contents of [OHI] and [OHII] (types of phenolic hydroxyl groups) groups were disproportionately increased. The main structure of lignin still was present after the [Bmim]Cl pretreatment. The β-O-4 linkages were broken apart. The degree of lignin degeneration increased with increased time, after being pre-treated with [Bmim]Cl. Simultaneously, a condensation reaction also took place during the pretreatment. Understanding the chemical changes to wheat straw lignin during an ionic liquid pretreatment provides an important theoretical basis for its further industrial use.

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“…On the other hand, aliphatic low-molecular-weight products were obtained in high yields. Seca et al (1998) analyzed kenaf cores and cuticles using various methods and reported that there were strong structural differences in the bark (cuticle) and core lignins in kenaf. Nishimura et al (2002) also analyzed separated kenaf bast, inner bast, and core samples prepared from the top, upper middle, lower middle, and bottom of kenaf stems.…”

Section: Pyrolysis Of Separated Core and Cuticle Kenaf Tissuesmentioning

confidence: 99%

Pyrolysis characteristic of kenaf studied with separated tissues, alkali pulp, and alkali lignin

et al. 2015

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HIGHLIGHTS Lignin and pulp prepared from kenaf were pyrolyzed to produce chemicals.Pyrolysates from the alkali lignin of kenaf contained valuable phenols.Pyrolysis of the alkali pulp of kenaf produced levoglucosan in high yields. To estimate the potential of kenaf as a new biomass source, analytical pyrolysis was performed using various kenaf tissues, i.e., alkali lignin and alkali pulp. The distribution of the pyrolysis products from the whole kenaf was similar to that obtained from hardwood, with syringol, 4-vinylsyringol, guaiacol, and 4-vinylguaiacol as the major products. The phenols content in the pyrolysate from the kenaf core was higher than that from the kenaf cuticle, reflecting the higher lignin content of the kenaf core. The ratios of the syringyl and guaiacyl compounds in the pyrolysates from the core and cuticle samples were 2.79 and 6.83, respectively. Levoglucosan was the major pyrolysis product obtained from the kenaf alkali pulp, although glycol aldehyde and acetol were also produced in high yields, as previously observed for other cellulosic materials. Moreover, the pathways for the formation of the major pyrolysis products from alkali lignin and alkali pulp were also described, and new pyrolysis pathways for carbohydrates have been proposed herein. The end groups of carbohydrates bearing hemiacetal groups were subjected to ring opening and then they underwent further reactions, including further thermal degradation or ring reclosing. Variation of the ring-closing position resulted in the production of different compounds, such as furans, furanones, and cyclopentenones. GRAPHICAL ABSTRACT ARTICLE INFO ABSTRACT© 2015 BRTeam. All rights reserved. Kojima et al. / Biofuel Research Journal 8 (2015) 317-323 Please cite this article as: Kojima Y., Kato Y., Akazawa M., Yoon S.L., Lee M.K. Pyrolysis characteristic of kenaf studied with separated tissues, alkali pulp and alkali lignin.

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Structural Characterization of the Bark and Core Lignins from Kenaf (Hibiscus cannabinus)

Cited by 38 publications

References 22 publications

The isolation and characterization of lignin of kenaf fiber

The isolation and characterization of lignin of kenaf fiber

Structural Changes of Lignin after Ionic Liquid Pretreatment

Pyrolysis characteristic of kenaf studied with separated tissues, alkali pulp, and alkali lignin

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