Delignification Mechanism during High-Boiling Solvent Pulping Part 3. Structural Changes in Lignin Analyzed by 13C-NMR Spectroscopy

Holzforschung ◽  
2003 ◽  
Vol 57 (6) ◽  
pp. 602-610 ◽  
Author(s):  
T. Kishimoto ◽  
A. Ueki ◽  
Y. Sano
Keyword(s):  
Structural Changes ◽  
Black Liquor ◽  
Average Molecular Weight ◽  
Acid Catalyst ◽  
Gel Permeation Chromatography ◽  
13C Nmr Spectroscopy ◽  
Hydroxyl Groups ◽  
Nmr Study ◽  
High Boiling Solvent ◽  
C Nmr

Summary Milled wood lignin as well as wood meal from todo fir (Abies sachalinensis MAST) was treated with 70% aqueous 1,4-butanediol solution at 220°C without acid catalyst in order to elucidate the delignification mechanism during high-boiling solvent (HBS) pulping. HBS lignin was recovered from black liquor by precipitation, and was subjected to gel permeation chromatography and quantitative 13C-NMR study. The average molecular weight of MWL decreased. The content of phenolic hydroxyl groups in MWL increased from 0.28 to 0.68/OMe. The decrease in the content of β-O-4 substructures was evident, which may be attributed to the homolytic cleavage of phenolic β-aryl ethers. The changes in the content of β-5 and β-β substructures were rather small. The benzyl ether formation of β-O-4 structures with 1,4-butanediol was also confirmed by 13C-NMR. However, the signals corresponding to Hibbert's ketones were not observed, which suggests that acidolysis was not an important degradation pathway during HBS pulping.

Probing the molecular weights of sweetgum and pine kraft lignin fractions

TAPPI Journal ◽  
2021 ◽  
Vol 20 (6) ◽  
pp. 381-391
Author(s):  
JULIANA M. JARDIM ◽  
PETER W. HART ◽  
LUCIAN LUCIA ◽  
HASAN JAMEEL
Keyword(s):  
Molecular Weight ◽  
Black Liquor ◽  
Average Molecular Weight ◽  
Gel Permeation Chromatography ◽  
Systematic Investigation ◽  
Kraft Pulping ◽  
Molecular Weights ◽  
Lignin Recovery ◽  
Lignin Reactivity ◽  
Kinetics Of

The present investigation undertook a systematic investigation of the molecular weight (MW) of kraft lignins throughout the pulping process to establish a correlation between MW and lignin recovery at different extents of the kraft pulping process. The evaluation of MW is crucial for lignin characterization and utilization, since it is known to influence the kinetics of lignin reactivity and its resultant physicochemical properties. Sweetgum and pine lignins precipitated from black liquor at different pHs (9.5 and 2.5) and different extents of kraft pulping (30–150 min) were the subject of this effort. Gel permeation chromatography (GPC) was used to deter- mine the number average molecular weight (Mn), mass average molecular weight (Mw), and polydispersity of the lignin samples. It was shown that the MW of lignins from both feedstocks follow gel degradation theory; that is, at the onset of the kraft pulping process low molecular weightlignins were obtained, and as pulping progressed, the molecular weight peaked and subsequently decreased. An important finding was that acetobromination was shown to be a more effective derivatization technique for carbohydrates containing lignins than acetylation, the technique typically used for derivatization of lignin.

Cationic copolymerization of 1,3-pentadiene with α-pinene

2014 ◽  
Vol 34 (7) ◽  
pp. 583-589 ◽  
Author(s):  
Ai-Yuan Li ◽  
Xiang-Dong Sun ◽  
Hui-Bo Zhang ◽  
Yong-Chun Zhang ◽  
Bin Wang ◽  
...  
Keyword(s):  
Average Molecular Weight ◽  
Gel Permeation Chromatography ◽  
Polymerization Temperature ◽  
Scanning Calorimetry ◽  
Gardner Color ◽  
H Nmr ◽  
Cationic Copolymerization ◽  
Ft Ir ◽  
Better Than ◽  
C Nmr

Abstract The cationic copolymerization of 1,3-pentadiene (PD) with α-pinene (AP) initiated by aluminum trichloride (AlCl3) was carried out in N-pentane solvent. The effects of the polymerization temperature and the comonomer composition on the yield of the copolymer, softening point, Gardner color scale and number-average molecular weight (Mn) are discussed. The performance of the copolymer was better than that of AP homopolymer (PAP) and PD homopolymer (PPD). The structure of the copolymer was characterized by Fourier transform infrared spectroscopy (FT-IR), 1H-nuclear magnetic resonance (1H-NMR), 13C-NMR, differential scanning calorimetry (DSC) and gel permeation chromatography (GPC). In addition, the reactivity ratios for AP (M1) and PD (M2) determined by the Kelen-Tudos method from low-conversion data are r1=0.58 and r2=5.92, respectively.

A New Green Process for Synthesising High Quality PLLA Materials

2013 ◽  
Vol 750-752 ◽  
pp. 1377-1380 ◽  
Author(s):  
Hui Li Shao ◽  
Xian Jue Zhou ◽  
Xue Chao Hu
Keyword(s):  
Molecular Weight ◽  
Ring Opening ◽  
Average Molecular Weight ◽  
Gel Permeation Chromatography ◽  
Ring Opening Polymerization ◽  
Green Process ◽  
Weight Average Molecular Weight ◽  
H Nmr ◽  
Ft Ir ◽  
C Nmr

Synthesis of Poly(L-lactide) (PLLA) by the ring-opening polymerization (ROP) of L-lactides in supercritical carbon dioxide (SC-CO2) with co-solvent were studied. Effects of kinds of co-solvent on the molecular weight (MW) and the molecular weight distribution (MWD) of the resultant polymers were investigated by the gel permeation chromatography (GPC). The resultant polymers were also characterized with1H NMR,13C NMR and FT-IR. It was found that PLLA with high purity and almost without racemization could be obtained by this technology and the acetone is the best co-solvent for this kind of polymerization. By using stannous octoate as initiator and acetone as co-solvent, PLLA having a weight-average molecular weight (Mw) near to 9×104and polydispersity index (PDI) of 1.7 was successfully synthesized.

Characterization of aspen exploded wood lignin

1982 ◽  
Vol 60 (18) ◽  
pp. 2372-2382 ◽  
Author(s):  
R. H. Marchessault ◽  
Suzanne Coulombe ◽  
Hiromichi Morikawa ◽  
Danielle Robert
Keyword(s):  
Room Temperature ◽  
Average Molecular Weight ◽  
Gel Permeation Chromatography ◽  
Aryl Ether ◽  
Weight Average Molecular Weight ◽  
Nmr Spectrum ◽  
Typical Composition ◽  
Moist Steam ◽  
C Nmr

Exploded wood lignin (EXWL) was extracted from moist steam hydrolysed aspen (Populustremuloides) wood using methanol. The lignin was examined by elemental analysis, gel permeation chromatography, infrared spectroscopy, proton and 13C nmr. The observed nmr spectra were compared with those of aspen milled wood lignin (MWL). Typical composition of the material is C9H9.2O2.7(OCH3)1.1 Assignment of all the signals in the nmr spectrum led to the conclusion that the explosion process causes cleavage of the β-aryl-ether bond. The weight average molecular weight was found to be 1700–1900 and the polydispersity 2.6. The finely divided exploded wood was soluble in 90% methanol/water mixtures to well beyond 20% by weight at room temperature.

Chemistry of chromotropic acid. 1H and 13C NMR spectroscopy of chromotropic acid and its derivatives

1991 ◽  
Vol 69 (8) ◽  
pp. 1207-1211 ◽  
Author(s):  
Paris E. Georghiou ◽  
Chi Keung (Jimmy) Ho ◽  
Chester R. Jablonski
Keyword(s):  
Nmr Spectroscopy ◽  
13C Nmr ◽  
Nmr Spectra ◽  
Deuterium Oxide ◽  
13C Nmr Spectroscopy ◽  
Chromotropic Acid ◽  
Hydroxyl Groups ◽  
Two Dimensional ◽  
1H And 13C Nmr ◽  
C Nmr

The 1H and 13C NMR spectra of chromotropic acid (CTA) (4,5-dihydroxy-2,7-naphthalenedisulphonic acid) have been unambiguously assigned. Proton NOED spectra were used to show the proximity of both H-3 and H-6 and the hydroxyl groups. Two-dimensional 1H–13C NMR correlation spectra of CTA, of its corresponding diacetoxy derivative, and of 3-bromo- and 3,6-dibromo-CTA support the assignments. A regioselective deuterium exchange reaction of the C-3 and C-6 protons of CTA with deuterium oxide was observed during the NMR experiments. This latter finding is strongly indicative of the mode of formation, and of the nature of the chromogen formed in the reaction of CTA with formaldehyde in the well-known CTA-formaldehyde analytical reaction. Key words: chromotropic acid, 3-bromochromotropic acid, 3,6-dibromochromotropic acid.

Structural characteristics of milled wood lignin (MWL) isolated from green liquor (GL) pretreated poplar (Populus deltoides)

Holzforschung ◽  
2017 ◽  
Vol 71 (2) ◽  
pp. 99-108 ◽  
Author(s):  
Xu Tan ◽  
Bo Jiang ◽  
Yiqin Yang ◽  
Douyong Min ◽  
Yongcan Jin
Keyword(s):  
Quantum Coherence ◽  
Structural Changes ◽  
Populus Deltoides ◽  
Structural Characteristics ◽  
Average Molecular Weight ◽  
Enzymatic Saccharification ◽  
Gel Permeation Chromatography ◽  
Milled Wood Lignin ◽  
Green Liquor ◽  
Alkaline Conditions

Abstract Pretreatment is one of the key steps for the utilization of lignocellulosic biomasses via biorefinery. Green liquor (GL) pretreatment has been considered as an effective approach to improve the subsequent enzymatic saccharification. For the better understanding of the structural changes of lignin in GL pretreatment, milled wood lignin (MWL) samples isolated from untreated and GL-pretreated poplar by the Björkman method were characterized by means of gel permeation chromatography (GPC), alkaline nitrobenzene oxidation (NBO), Fourier transform-infrared (FT-IR) spectroscopy, and quantitative 13C and 2D heteronuclear single quantum coherence nuclear magnetic resonance (HSQC NMR). The results indicate that the average molecular weight of MWLs decreased after GL pretreatment. Surprisingly, more guaiacyl-propane units are extracted under mild alkaline conditions than syringyl-propane units, which results in a higher condensation degree and higher S/G ratios of MWLs isolated from GL-pretreated poplars. The amount of β–O–4 structures decreased, while the β–β and β-5 structures increased after GL pretreatment. The structure of esterified p-hydroxybenzoic acid was detected in poplar MWL sample and it degraded obviously after GL pretreatment.

scholarly journals Composition and Structure of Ethanol-Lignins of Coniferous and Deciduous Wood and Products of their Catalytic Telomerization with 1,3-Butadiene

2021 ◽  
Vol 14 (4) ◽  
pp. 539-551
Author(s):  
Maxim A. Lutoshkin ◽  
◽  
Franck Rataboul ◽  
Laurent Djakovitch ◽  
Yuriy N. Malyar ◽  
...  
Keyword(s):  
Average Molecular Weight ◽  
Total Content ◽  
Gel Permeation Chromatography ◽  
Analysis Data ◽  
Elemental Analysis Data ◽  
Hydroxyl Groups ◽  
Oh Groups ◽  
Composition And Structure ◽  
Phenolic Hydroxyl Groups ◽  
Telomerization Reaction

The composition and structure of ethanol-lignins of coniferous (abies, pine) and deciduous (aspen, birch) wood and products of their catalytic telomerization with 1,3-butadiene has been studied with use of the methods 31P-NMR, gel-permeation chromatography, scanning electron microscopy and elemental analysis. Data on the nature and content of hydroxyl groups in ethanol-lignins were obtained using phosphorylation of lignins with 2-chloro‑4,4,5,5,-tetramethyl‑1,3,2-dioxaphospholane.The studied lignins differ from each other in the content of aliphatic, phenolic and carboxyl groups. The total content of hydroxyl groups increases in the series of ethanol-lignins: birch < aspen < pine < abies. For the modification of ethanol-lignins, the reaction of catalytic telomerization with 1,3-butadiene was used at 70 °C and 90 °C in the presence of a complex of palladium (II) diacetate with the sodium salt of triphenylphosphine trisulfate. By comparing the number of aliphatic, phenolic and carboxyl OH- groups in the initial and telomerized ethanol-lignins, it was found that only aliphatic and phenolic hydroxyl groups participate in the telomerization reaction. Telomerization of ethanol-lignins with 1,3-butadiene increases their average molecular weight and reduces polydispersity. The morphology of telomerized and initial samples of ethanol-lignins varies significantly

scholarly journals A straightforward implementation of in situ solution electrochemical 13C NMR spectroscopy for studying reactions on commercial electrocatalysts: ethanol oxidation

2015 ◽  
Vol 51 (38) ◽  
pp. 8086-8088 ◽  
Author(s):  
L. Huang ◽  
E. G. Sorte ◽  
S.-G. Sun ◽  
Y. Y. J. Tong
Keyword(s):  
Nmr Spectroscopy ◽  
13C Nmr ◽  
Ethanol Oxidation ◽  
13C Nmr Spectroscopy ◽  
Nmr Study ◽  
C Nmr

The first in situ solution electrochemical 13C NMR study of ethanol oxidation on commercial Pt/C and PtRu/C was reported.

The Determination of Hydroxyl Groups in Coal by Fourier Transform Infrared and 13C NMR Spectroscopy

1983 ◽  
Vol 37 (6) ◽  
pp. 497-502 ◽  
Author(s):  
R. W. Snyder ◽  
P. C. Painter ◽  
J. R. Havens ◽  
J. L. Koenig
Keyword(s):  
Fourier Transform ◽  
Nmr Spectroscopy ◽  
Fourier Transform Infrared ◽  
13C Nmr Spectroscopy ◽  
Hydroxyl Groups ◽  
Oh Groups ◽  
The Individual ◽  
Oh Content ◽  
C Nmr

Fourier transform infrared spectroscopy and solid state 13C NMR spectroscopy have been used to measure the hydroxyl groups in coal. The methodology depends upon measuring the intensities of bands and resonances assigned to the products of acetylation reactions. In the infrared three separate bands, assigned to acetylated phenolic OH, alkyl OH, and NH groups, can be identified. In NMR, we used the methoxy carbon to determine the total OH. Spectroscopic measurements demonstrate that not only does the total OH content of coals but also the individual types of OH groups vary systematically as a function of rank. The proportion of phenolic to alkyl OH is approximately constant for the coals used in this study.

Folding-Controlled Assembly of Ortho-Phenylene-Based Macrocycles

2020 ◽  
Author(s):  
Viraj kirinda ◽  
Scott Hartley
Keyword(s):  
Self Assembly ◽  
Structural Control ◽  
Structural Changes ◽  
Condensation Product ◽  
Gel Permeation Chromatography ◽  
Emergent Behavior ◽  
Order Structure ◽  
High Level ◽  
Alkoxy Groups ◽  
Energy Surfaces

The self-assembly of foldamers into macrocycles is a simple approach to non-biological higher-order structure. Previous work on the co-assembly of ortho-phenylene foldamers with rod-shaped linkers has shown that folding and self-assembly affect each other; that is, the combination leads to new emergent behavior, such as access to otherwise unfavorable folding states. To this point this relationship has been passive. Here, we demonstrate control of self-assembly by manipulating the foldamers’ conformational energy surfaces. A series of o-phenylene decamers and octamers have been assembled into macrocycles using imine condensation. Product distributions were analyzed by gel-permeation chromatography and molecular geometries extracted from a combination of NMR spectroscopy and computational chemistry. The assembly of o-phenylene decamers functionalized with alkoxy groups or hydrogens gives both [2+2] and [3+3] macrocycles. The mixture results from a subtle balance of entropic and enthalpic effects in these systems: the smaller [2+2] macrocycles are entropically favored but require the oligomer to misfold, whereas a perfectly folded decamer fits well within the larger [3+3] macrocycle that is entropically disfavored. Changing the substituents to fluoro groups, however, shifts assembly quantitatively to the [3+3] macrocycle products, even though the structural changes are well-removed from the functional groups directly participating in bond formation. The electron-withdrawing groups favor folding in these systems by strengthening arene–arene stacking interactions, increasing the enthalpic penalty to misfolding. The architectural changes are substantial even though the chemical perturbation is small: analogous o-phenylene octamers do not fit within macrocycles when perfectly folded, and quantitatively misfold to give small macrocycles regardless of substitution. Taken together, these results represent both a high level of structural control in structurally complex foldamer systems and the demonstration of large-amplitude structural changes as a consequence of a small structural effects.

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