Delignification mechanism during high-boiling solvent pulping. Part 6: Changes in lignin structure analyzed by 1H-13C correlation 2-D NMR spectroscopy

Holzforschung ◽  
2004 ◽  
Vol 58 (4) ◽  
pp. 355-362 ◽  
Author(s):  
T. Kishimoto ◽  
A. Ueki ◽  
H. Takamori ◽  
Y. Uraki ◽  
M. Ubukata
Keyword(s):  
Nmr Spectroscopy ◽  
Spectral Data ◽  
Abies Sachalinensis ◽  
Model Compounds ◽  
Lignin Model Compounds ◽  
Milled Wood Lignin ◽  
High Boiling Solvent ◽  
Lignin Model ◽  
C Nmr ◽  
Lignin Structure

Abstract In order to investigate the delignification mechanism during high-boiling solvent (HBS) pulping, softwood HBS lignin samples from todo fir (Abies sachalinensis) were analyzed by 1H–13C correlation NMR spectroscopy (HMQC). Nine lignin model compounds that may represent the substructures in HBS lignin were prepared. The 1H and 13C NMR spectral data were compared with HBS lignin samples. The HMQC spectra of HBS lignin samples showed the disappearance of β-O-4 structures. Introduction of a pulping solvent into lignin was plainly observed with new signals in aliphatic regions. Only the erythro β-1 structure was detected in softwood milled wood lignin from todo fir by HMQC spectra. The β-1 structure was very reactive and probably produced the stilbene structure. The β-β and β-5 structures remained in HBS lignin. The 4-O-5 structure was successfully detected by HMQC spectra, and it was found to be stable under the conditions used.

Determination of chemical shifts in 6-condensed syringylic lignin model compounds

Holzforschung ◽  
2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Lucas Lagerquist ◽  
Jani Rahkila ◽  
Patrik Eklund
Keyword(s):  
Chemical Shift ◽  
Methoxy Group ◽  
Chemical Shifts ◽  
Model Compounds ◽  
Correlation Peak ◽  
Lignin Model Compounds ◽  
Benzylic Alcohols ◽  
Lignin Model ◽  
C Nmr

Abstract A small library of 6-substituted syringyl model compounds with aliphatic, carboxylic, phenylic, benzylic alcohols and brominated substituents were prepared. The influence of the substituents on the chemical shifts of the compounds was analyzed. All of model compounds showed a characteristic increase in the 13C NMR chemical shift of the methoxy group vicinal to the substitution. This 13C NMR peak and its corresponding correlation peak in HSQC could potentially be used to identify 6-condensation in syringylic lignin samples.

scholarly journals Effect of lignin structure on adsorbable organic halogens formation in chlorine dioxide bleaching

2019 ◽  
Vol 6 (2) ◽  
pp. 182024 ◽  
Author(s):  
Lisheng Shi ◽  
Jiayan Ge ◽  
Shuangxi Nie ◽  
Chengrong Qin ◽  
Shuangquan Yao
Keyword(s):  
Chlorine Dioxide ◽  
Model Compound ◽  
Pulp Bleaching ◽  
Model Compounds ◽  
Lignin Model Compounds ◽  
Lignin Model Compound ◽  
Lignin Model ◽  
Organic Halogens ◽  
Adsorbable Organic Halogens ◽  
Lignin Structure

Adsorbable organic halogens (AOX) are formed in pulp bleaching as a result of the reaction of residual lignin with chlorine dioxide. The natural structure of lignin is very complex and it tends to be damaged by various extraction methods. All the factors can affect the study about the mechanism of AOX formation in the reaction of lignin with chlorine dioxide. Lignin model compounds, with certain structures, can be used to study the role of different lignin structures on AOX formation. The effect of lignin structure on AOX formation was determined by reacting phenolic and non-phenolic lignin model compound with a chlorine dioxide solution. Vanillyl alcohol (VA) and veratryl alcohol (VE) were selected for the phenolic and non-phenolic lignin model compound, respectively. The pattern consumption of lignin model compounds suggests that both VA and VE began reacting with chlorine dioxide within 10 min and then gradually steadied. The volume of AOX produced by VE was significantly higher than that produced by VA for a given initial lignin model compound concentration. In a solution containing a combination of VA and VE in chlorine dioxide, VE was the dominant producer of AOX. This result indicates that the non-phenolic lignin structure was more easily chlorinated, while the phenolic lignin structure was mainly oxidized. In addition, AOX content produced in the combined experiments exceeded the total content of the two separate experiments. It suggested that the combination of phenolic and non-phenolic lignin structure can promote AOX formation.

Lignin to Value-Added Chemical Synthesis

2020 ◽  
Vol 16 ◽  
Author(s):  
Mahdieh Sharifi ◽  
Ramyakrishna Pothu ◽  
Rajender Boddula ◽  
Inamuddin
Keyword(s):  
Ionic Liquids ◽  
Lignocellulosic Biomass ◽  
Academic Research ◽  
Power Saving ◽  
Value Added ◽  
Glycerol Ether ◽  
Model Compounds ◽  
Lignin Model Compounds ◽  
Biomass Activity ◽  
Lignin Model

Background: There is a developing demand for innovation in petroleum systems replacements. Towards this aim, lignocellulosic biomass suggested as a possible sustainable source for the manufacturing of fuels and produced chemicals. The aims of this paper are to investigate different kinds of β-O-4 lignin model compounds for the production of value-added chemicals in presence of ionic liquids. Especially, a cheap β-O-4 lignin model Guaiacol glycerol ether (GGE) (Guaifenesin) is introduced to produce valuable chemicals and novel products. Methods: Research related to chemical depolymerization of lignocellulosic biomass activity is reviewed, the notes from different methods such as thermal and microwave collected during at least 10 years. So, this collection provides a good source for academic research and it gives an efficient strategy for the manufacturing of novel value-added chemicals at an industrial scale. Results: This research presented that ionic liquid microwave-assisted is a power saving, cost efficient, fast reaction, and clean way with high selectively and purity for production of high value chemicals rather that conversional heating. Guaiacol and catechol are some of these valuable chemicals that is produced from β-O-4 lignin model compounds with high word demands that are capable to produce in industry scale. Conclusion: The β-O-4 lignin model compounds such as Guaiacol glycerol ether (GGE) (Guaifenesin) are good platform for developing food materials, perfumery, biorefinery, and pharmaceutical industry by ionic liquids-assisted lignin depolymerization method.

Insights into the electrochemical degradation of phenolic lignin model compounds in protic ionic liquid-water system

2021 ◽  
Author(s):  
Guangyong Liu ◽  
Qian Wang ◽  
Dongxia Yan ◽  
Yaqin Zhang ◽  
Chenlu Wang ◽  
...  
Keyword(s):  
Water System ◽  
Value Added ◽  
Electrochemical Degradation ◽  
Aryl Ether ◽  
Model Compounds ◽  
Protic Ionic Liquid ◽  
Lignin Model Compounds ◽  
Mild Conditions ◽  
System P ◽  
Lignin Model

Cleavage of aryl ether (Caryl-O) bonds is crucial for conversion and value-added utilization of lignin and its derivatives, but remains extremely challenging under mild conditions due to strong Caryl-O linkages....

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