scholarly journals Acid-Catalyzed α-O-4 Aryl-Ether Cleavage Mechanisms in (Aqueous) γ-Valerolactone: Catalytic Depolymerization Reactions of Lignin Model Compound During Organosolv Pretreatment

2020 ◽  
Vol 8 (47) ◽  
pp. 17475-17486
Author(s):  
Edita Jasiukaitytė-Grojzdek ◽  
Matej Huš ◽  
Miha Grilc ◽  
Blaž Likozar
Keyword(s):  
Model Compound ◽  
Aryl Ether ◽  
Organosolv Pretreatment ◽  
Ether Cleavage ◽  
Lignin Model Compound ◽  
Lignin Model ◽  
Acid Catalyzed

scholarly journals Aromatic–hydroxyl interaction of an alpha-aryl ether lignin model-compound on SBA-15, present at pyrolysis temperatures

2014 ◽  
Vol 16 (44) ◽  
pp. 24188-24193 ◽  
Author(s):  
M. V. Kandziolka ◽  
M. K. Kidder ◽  
L. Gill ◽  
Z. Wu ◽  
A. Savara
Keyword(s):  
Hydrogen Bonds ◽  
Model Compound ◽  
Vibrational Frequencies ◽  
Aryl Ether ◽  
Lignin Model Compound ◽  
Surface Hydroxyls ◽  
Lignin Model

BPEa hydrogen bonds to SBA-15 surface hydroxylsviaan aromatic–hydroxyl interaction characterized by a redshift of >100 cm−1in the OH and CH vibrational frequencies. Surprisingly, this aromatic–hydroxyl interaction is present until ∼400 °C.

Liquefaction Mechanism of β-O-4 Lignin Model Compound in the Presence of Phenol under Acid Catalysis. Part 2. Reaction Behaviour and Pathways

Holzforschung ◽  
2001 ◽  
Vol 55 (6) ◽  
pp. 625-630 ◽  
Author(s):  
L. Lin ◽  
S. Nakagame ◽  
Y. Yao ◽  
M. Yoshioka and N. Shiraishi ◽  
N. Shiraishi
Keyword(s):  
High Performance ◽  
Model Compound ◽  
Structural Characteristics ◽  
Gel Permeation Chromatography ◽  
Main Reaction ◽  
Reaction Products ◽  
Reaction Behavior ◽  
Lignin Model Compound ◽  
Lignin Model ◽  
Acid Catalyzed

Summary By means of high performance liquid chromatography (HPLC) and gel permeation chromatography (GPC), the yields of the main reaction products and the polymeric portion formed in the reaction of guaiacylglycerol-β-guaiacyl ether (GG) under various acid-catalyzed conditions were quantified as a function of reaction time. Based on their forming sequence and reaction behavior, as well as their structural characteristics, an acid-catalyzed reaction mechanism of GG with phenol was proposed.

scholarly journals A Novel Polyphenol Oxidoreductase OhLac from Ochrobactrum sp. J10 for Lignin Degradation

2021 ◽  
Vol 12 ◽  
Author(s):  
Chenxian Yang ◽  
Lingling Ma ◽  
Xin Wang ◽  
Yuqi Xing ◽  
Xin Lü
Keyword(s):  
Lignin Degradation ◽  
Model Compound ◽  
Corn Stalk ◽  
Aryl Ether ◽  
Docking Analysis ◽  
Lignin Valorization ◽  
Lignin Model Compound ◽  
Effects Of Ph ◽  
Lignin Model ◽  
Chemical Products

Identifying the enzymes involved in lignin degradation by bacteria is important in studying lignin valorization to produce renewable chemical products. In this paper, the catalytic oxidation of lignin by a novel multi-copper polyphenol oxidoreductase (OhLac) from the lignin degrader Ochrobactrum sp. J10 was explored. Following its expression, reconstitution, and purification, a recombinant enzyme OhLac was obtained. The OhLac enzyme was characterized kinetically against a range of substrates, including ABTS, guaiacol, and 2,6-DMP. Moreover, the effects of pH, temperature, and Cu2+ on OhLac activity and stability were determined. Gas chromatography-mass spectrometer (GC-MS) results indicated that the β-aryl ether lignin model compound guaiacylglycerol-β-guaiacyl ether (GGE) was oxidized by OhLac to generate guaiacol and vanillic acid. Molecular docking analysis of GGE and OhLac was then used to examine the significant amino residues and hydrogen bonding sites in the substrate–enzyme interaction. Altogether, we were able to investigate the mechanisms involved in lignin degradation. The breakdown of the lignocellulose materials wheat straw, corn stalk, and switchgrass by the recombinant OhLac was observed over 3 days, and the degradation results revealed that OhLac plays a key role in lignin degradation.

Delignification Mechanism during High-Boiling Solvent Pulping. Part 1. Reaction of Guaiacylglycerol-β-Guaiacyl Ether

Holzforschung ◽  
2001 ◽  
Vol 55 (6) ◽  
pp. 611-616 ◽  
Author(s):  
T. Kishimoto ◽  
Y. Sano
Keyword(s):  
Model Compound ◽  
Reaction Products ◽  
Aryl Ether ◽  
Lignin Model Compound ◽  
First Order ◽  
Order Rate ◽  
High Boiling Solvent ◽  
Lignin Model ◽  
Rate Behavior ◽  
Pseudo First Order

Summary A phenolic β-O-4 type lignin model compound, guaiacylglycerol-β-guaiacyl ether (1) was treated with 70 wt% aq 1,3-butanediol solution at 160–200°C to investigate the delignification mechanism under HBS (high-boiling solvent) pulping conditions. The following compounds were identified from the reaction products by use of GC-MS: guaiacol (2), coniferyl alcohol (3), γ-etherified coniferyl alcohols (4) and α-etherified guaiacylglycerol-β-guaiacyl ethers (5), but acidolysis products, such as Hibbert's ketones were not detected. These results strongly suggest that the phenolic β-O-4 linkage was cleaved homolytically under HBS pulping conditions. The cleavage of β-ether exhibited a pseudo first-order rate behavior. The pseudo first-order rate constants were as follows: k = 0.94 × 10−2 min−1 at 160 °C; k = 1.97 × 10−2 min−1 at 170°C; k = 3.22 × 10−2 min−1 at 180 °C; k = 9.76 x 10−2 min−1 at 200 °C. The activation energy was 98.3 kJmol−1. The formation of higher molecular weight compounds was confirmed by GPC. It is highly probable that the oligomeric products were derived from the recombination of phenoxy radicals formed by homolysis of the β-aryl ether.

Delignification Mechanism during High-Boiling Solvent Pulping. Part 2. Homolysis of Guaiacylglycerol-β-Guaiacyl Ether

Holzforschung ◽  
2002 ◽  
Vol 56 (6) ◽  
pp. 623-631 ◽  
Author(s):  
T. Kishimoto ◽  
Y. Sano
Keyword(s):  
Model Compound ◽  
Quinone Methide ◽  
Radical Mechanism ◽  
Reaction Products ◽  
Aryl Ether ◽  
Lignin Model Compound ◽  
High Boiling Solvent ◽  
Lignin Model ◽  
Phenoxy Radicals

Summary A phenolic β-O-4 type lignin model compound, guaiacylglycerol-β-guaiacyl ether, was treated with 70 wt % aq 1,4-butanediol solution at 180°C to investigate the delignification mechanism under high-boiling solvent (HBS) pulping conditions. Thirteen compounds including four monomers, six dimers, two trimers and a tetramer were isolated from the reaction products. Most of these products were generated by recombination of phenoxy radicals formed by homolysis of the β-aryl ether. The results suggest that phenolic β-O-4 linkages in lignin are cleaved homolytically (radical mechanism) via quinone methide intermediates under HBS pulping conditions.

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