Computational Study of Bond Dissociation Enthalpies for a Large Range of Native and Modified Lignins

Kim, Seonah; Chmely, Stephen C.; Nimlos, Mark R.; Bomble, Yannick J.; Foust, Thomas D.; Paton, Robert S.; Beckham, Gregg T.

doi:10.1021/jz201182w

Cited by 344 publications

(318 citation statements)

References 34 publications

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“…Recently, many papers have reported theoretical calculations of the bond dissociation energies (BDEs) for linkages in lignin related compounds [61][62][63][64][65][66][67][68][69][70]. These include calculations of α-O-4, β-O-4, 4-O-5, β-aryl, phenylcoumaran, pinoresinol, dibenzodioxocin type dimers.…”

Section: Bond Dissociation Energymentioning

confidence: 99%

Lignin pyrolysis reactions

2017

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Section: Bond Dissociation Energymentioning

confidence: 99%

Lignin pyrolysis reactions

2017

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“…First-principles simulation can provide valuable insight on the energetics and products of bond cleavage pathways. Previous computational efforts have focused on studying model compounds that contain the abundant β-O-4 ether lignin linkage by evaluating homolytic bond dissociation energies [35][36][37][38][39] , mechanical properties [40][41][42][43] , intramolecular hydrogen bonding 44 . More recently, some kinetic modeling and analysis has been carried out, particularly to model fast pyrolysis [45][46][47][48][49][50] .…”

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

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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

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“…β-O-4 and α-O-4 linkages generally undergo cleavage by HDG more easily than do other types of lignin bonds. 21 However, catalysts effective for C-O bond HDG often promote unwanted hydrogenation of the arene rings to give cyclohexyl derivatives. A major objective in lignin valorization through HDG is to cleave aryl-ether bonds while minimizing aromatic ring hydrogenation.…”

Section: Introductionmentioning

confidence: 99%

Enhancing Aromatic Production from Reductive Lignin Disassembly: in Situ O-Methylation of Phenolic Intermediates

Barrett

Gao

Bernt

et al. 2016

ACS Sustainable Chem. Eng.

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ABSTRACT:The selective conversion of lignin into aromatic compounds has the potential to serve as a "green" alternative to the production of petrochemical aromatics. Herein, we evaluate the addition of dimethyl carbonate (DMC) to a biomass conversion system that uses a Cu-doped porous metal oxide (Cu 20 PMO) catalyst in supercritical methanol (sc-MeOH) to disassemble lignin with little to no char formation. While Cu 20 PMO catalyzes C-O hydrogenolysis of aryl-ether bonds linking lignin monomers, it also catalyzes arene methylation and hydrogenation, leading to product proliferation. The MeOH/DMC co-solvent system significantly suppresses arene hydrogenation of the phenolic intermediates responsible for much of the undesirable product diversity via Omethylation of phenolic -OH groups to form more stable aryl-OCH 3 species. Consequently, product proliferation was greatly reduced and aromatic yields greatly enhanced with lignin models, 2-methoxy-4-propylphenol, benzyl phenyl ether, and 2-phenoxy-1-phenylethan-1-ol. In addition, organosolv poplar lignin (OPL) was examined as a substrate in the MeOH/DMC co-solvent system. The products were characterized by nuclear magnetic resonance spectroscopy ( 31 P, 13 C, and 2D 1 H-13 C NMR) and gas chromatography-mass spectrometry techniques. The co-solvent system demonstrated enhanced yields of aromatic products. INTRODUCTION.

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Computational Study of Bond Dissociation Enthalpies for a Large Range of Native and Modified Lignins

Cited by 344 publications

References 34 publications

Lignin pyrolysis reactions

Lignin pyrolysis reactions

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

Enhancing Aromatic Production from Reductive Lignin Disassembly: in Situ O-Methylation of Phenolic Intermediates

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