Understanding the chemical transformations of lignin during ionic liquid pretreatment

Wen, Jia‐Long; Yuan, Tong‐Qi; Sun, Shaolong; Xu, Feng; Sun, Run‐Cang

doi:10.1039/c3gc41752b

Cited by 281 publications

(223 citation statements)

References 39 publications

Supporting

Mentioning

193

Contrasting

Order By: Relevance

“…The elemental carbon content of OAL (26.5%) was determined to be obviously lower than that of LM/NPs (49.1%), whereas the oxygen content of LM/NPs (43.1%) was lower than that of OAL (66.1%). This may be due to the large amount of dehydration and demethoxylation reactions that occurred during dissolution process, which is consistent with other literature reports [19].The relatively high nitrogen content (2.1%) of LM/NPs was particularly notable, Table1. Elemental composition, calculated C 9 formula, and degree of unsaturation of original alkali lignin (OAL) and lignin micro/nano-particles (LM/NPs).…”

Section: Results and Discussion 31 Sem And Plm Observationsupporting

confidence: 80%

Preparation and structural characterization of lignin micro/nano-particles with ionic liquid treatment by self-assembly

Liu¹,

Li²,

Hou³

2018

Express Polym. Lett.

View full text Add to dashboard Cite

Abstract. In the present research, 1,3-dimethyl-imidazolium dimethyl phosphate ([Mmim][DMP]) ionic liquid was applied to dissolve alkali lignin from wheat grass to prepare for lignin micro/nano-particles. The alkali lignin can be dissolved completely at 80°C in 30 min under microwave condition with [Mmim][DMP] (solid-liquid ratio of 1:10) which is easy to be recycled. The dissolved lignin can be precipitated by diluting the ionic liquid-lignin solution with water to get lignin micro/nano-particles with diameter ranged from 200 nm to 1.5 μm. Structural analyses with Gel permeation chromatography (GPC), 2D heteronuclear single quantum coherence nuclear magnetic resonance (2D-NMR), Thermogravimetric Analysis (TGA), etc., indicate that a large number of dehydration reactions occurred during dissolution process to result in the generation of unsaturated bonds with higher degree of unsaturation (Ω) (from 197-334), lower polydispersity (from 1.49 to 1.12) and lower average molecular weight (from 8634 to 5406 Da). Compared with original alkali lignin, the regenerated alkali lignin as micro/nano-particles showed higher thermal stability. It was also found from the 2D NMR spectra that the cleavages of aryl-ether bonds dramatically happened during the dissolution process, [Mmim][DMP] ionic liquid is more likely to destroy lignin units linked by β-O-4′ bonds to G-type lignin with less steric hindrance, resulting in the least amount of β-O-4′ linkages. In addition, dehydration and demethylation of lignin occurred during the dissolution of ionic liquid.

show abstract

Section: Results and Discussion 31 Sem And Plm Observationsupporting

confidence: 80%

Preparation and structural characterization of lignin micro/nano-particles with ionic liquid treatment by self-assembly

Liu¹,

Li²,

Hou³

2018

Express Polym. Lett.

View full text Add to dashboard Cite

show abstract

“…Thus, depolymerization of unprocessed lignin remains of significant interest 8,16 and has been pursued experimentally with polyoxometalate catalysts 17 , base-catalyzed hydrolysis [18][19] , acidolysis [20][21] , ionic liquid treatment 22 , reduction with hydrosilanes 23 , photochemical degradation 24 , and ball milling 25 . In addition to general depolymerization, efforts have also included selective strategies via homogeneous catalysts [26][27][28][29][30] and enzymes 31 .…”

Section: Introductionmentioning

confidence: 99%

Depolymerization Pathways for Branching Lignin Spirodienone Units Revealed with ab Initio Steered Molecular Dynamics

Mar

Kulik

2017

J. Phys. Chem. A

View full text Add to dashboard Cite

Lignocellulosic biomass is an abundant, rich source of aromatic compounds, but direct utilization of raw lignin has been hampered by both the high heterogeneity and variability of linking bonds in this biopolymer. Ab initio steered molecular dynamics (AISMD) has emerged both as a fruitful direct computational screening approach to identify products that occur through mechanical depolymerization (i.e., in sonication or ball-milling) and as a sampling approach. By varying the direction of force and sampling over 750 AISMD trajectories, we identify numerous possible pathways through which lignin depolymerization may occur in pyrolysis or through catalytic depolymerization as well. Here, we present eight unique major depolymerization pathways discovered via AISMD for the recently characterized spirodienone lignin branchinglinkage that may comprise around 10% weight of all lignin in some softwoods. We extract representative trajectories from AISMD and carry out reaction pathway analysis to identify energetically favorable pathways for lignin depolymerization. Importantly, we identify dynamical effects that could not be observed through more traditional calculations of bond dissociation energies. Such effects include thermodynamically favorable recovery of aromaticity in the dienone ring that leads to near-barrierless subsequent ether cleavage and hydrogen bonding effects that stabilize newly formed radicals. Some of the most stable spirodienone fragments that reside at most 1 eV above the reactant structure are formed with only 2 eV barriers for C-C bond cleavage, suggesting key targets for catalyst design to drive targeted depolymerization of lignin.2

show abstract

“…The changes in the molecular weights of lignin could provide important insights into lignin's fragmentation and recondensation during an IL pretreatment (Wen et al 2014). To determine the effect of [Bmim]Cl on the molecular weight of lignin, GPC was used for the analysis of RL, ILL1, and ILL2.…”

Section: Gel Permeation Chromatography Analysismentioning

confidence: 99%

Structural Changes of Lignin after Ionic Liquid Pretreatment

et al. 2017

View full text Add to dashboard Cite

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.

show abstract

Understanding the chemical transformations of lignin during ionic liquid pretreatment

Cited by 281 publications

References 39 publications

Preparation and structural characterization of lignin micro/nano-particles with ionic liquid treatment by self-assembly

Preparation and structural characterization of lignin micro/nano-particles with ionic liquid treatment by self-assembly

Depolymerization Pathways for Branching Lignin Spirodienone Units Revealed with ab Initio Steered Molecular Dynamics

Structural Changes of Lignin after Ionic Liquid Pretreatment

Contact Info

Product

Resources

About