Acid Reactions of Lignin Models of β-5 Type

Li, Shiming; Lundquist, Knut

doi:10.1515/hf.1999.007

Cited by 22 publications

(16 citation statements)

References 13 publications

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“…The β-5 linkage is almost exclusively modified via a similar mechanism. [17] This also means, that the formaldehyde released during these reactions is probably trapped in the form of its ethylene-glycol acetal 1,3-dioxolane as also confirmed in our earlier studies.…”

Section: Resultssupporting

confidence: 80%

Metal Triflates for the Production of Aromatics from Lignin

et al. 2016

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Abstract:The depolymerization of lignin into valuable aromatic chemicals is one of the key goals towards establishing economically viable biorefineries. In this contribution we present a simple approach for converting lignin to aromatic monomers in high yields, under mild reaction conditions. The methodology relies on the use of catalytic amounts of easy to handle metal triflates. Initially, we evaluated the reactivity of a broad range of metal triflates using simple lignin model compounds. More advanced lignin model compounds were also used to study the reactivity of different lignin linkages. The product aromatic monomers were either phenolic C2 acetals obtained by stabilization of the aldehyde cleavage products by reaction with ethylene glycol, or methyl aromatics obtained by catalytic decarbonylation. Notably, when the former method was ultimately tested on lignin, especially Fe(OTf)3 proved very effective and the phenolic C2 acetal products were obtained in an excellent, 19.3 ±3.2 Wt% yield.

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Section: Resultssupporting

confidence: 80%

Metal Triflates for the Production of Aromatics from Lignin

et al. 2016

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“…50 Meanwhile, β−5 units could be converted to stilbenes through loss of the γ-methylol group as formaldehyde. 52 Although complete removal of β−O−4 interlinkages in lignin could be achieved under conventional organosolv pretreatments at harsh pretreatment conditions, 53 one of the advantages of using THF as the water cosolvent is that THF could preferentially solvate lignin and the THF/water cosolvent mixture could act as a "theta" solvent to prevent lignin aggregation or repolymerization while facilitating lignin solubilization. 34 GPC results indicated that CELF lignin had much lower weight-average molecular weight (M w ) and number-average molecular weight (M n ) compared to CEL, suggesting significant lignin depolymerization during CELF pretreatment.…”

Section: ■ Materials and Methodsmentioning

confidence: 99%

Hybrid Catalytic Biorefining of Hardwood Biomass to Methylated Furans and Depolymerized Technical Lignin

Seemala

Meng

Parikh

et al. 2018

ACS Sustainable Chem. Eng.

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A robust method is needed to achieve high yield all-catalytic conversion of recalcitrant lignocellulosic biomass to transportation fuels while maximizing carbon utilization from raw substrates. To accomplish this, we developed an integrated strategy that combines homogeneous and heterogeneous reactions with a treatment-extraction step to coproduce 2-methylfuran (MF) and 2,5-dimethylfuran (DMF) directly from hardwood poplar while maintaining high catalyst activity. In the first step, poplar wood chips were treated with dilute FeCl 3 in THF−water at subpyrolytic temperature to yield 93.5% furfural (FF) from xylan and 66.0% 5-hydroxymethylfurfural (HMF) from glucan. Concurrently, a highly pure lignin powder was obtained from the liquor by precipitation upon room temperature vacuum recovery of THF from the water. Afterward, FF and HMF were extracted from water into an organic phase consisting of toluene and 1,4-dioxane treated with Ca(OH) 2. A second hydrodeoxygenation reaction using Cu−Ni/TiO 2 catalyst yielded 87.8% MF from FF and 85.6% DMF from HMF. Characterization of the lignin product showed its molecular weight to be reduced by an order of magnitude from its native state as well as complete removal of its native β-aryl ether linkages without hydrogen input or further heterogeneous catalytic processing. A 60% cumulative yield of MF, DMF, and lignin products from the available carbon (xylan+glucan+lignin) in poplar was achieved, rivaling more mature cellulosic ethanol strategies.

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“…In summary, the formation of 1,3-dioxane structures 1 and phenyl-dihydrobenzofuran 3 from GG under the acidic GVL-H 2 O system suggests that the actions of GVL pretreatment on lignin model GG was different from those induced by the traditional acidolysis. [18][19][20][21]. In the acidic GVL-H 2 O system used here, compound 22 was transformed following the pathway described in Figure 5.…”

Section: Reactions Of β-O-4 Lignin Model Gg In Gvl/ H 2 O (80/20) Systemmentioning

confidence: 99%

“…The β-5 (phenylcoumaran) types of structures are the second most abundant component of lignin. The reactions of β-5 lignin model compounds 22 and 26 have been investigated under acidolysis conditions [18][19][20][21]. In the acidic GVL-H2O system used here, compound 22 was transformed following the pathway described in Figure 5.…”

Section: Reactions Of β-5 Lignin Models In Gvl/ H2o (80/20) Systemmentioning

confidence: 99%

“…It was well documented that β-O-4 aryl ether models were degraded into guaiacol and Hibbert's ketones via enol ethers intermediates formed from acid catalyzed dehydration of the 1,3-diol model; meanwhile the released guaiacol attacked the benzyl cation resulting in the condensation product (supporting information, Figure S1). Lundquist et al [18][19][20][21] described the degradation mechanisms of phenylcoumaran type (β-5) models under acidolysis conditions. When phenolic or non-phenolic β-5 lignin models having propyl alcohol (R 1 = CH 2 -CH 2 -CH 2 OH) or a ketone (R 1 = CH 2 -CO-CH 2 OH) side chain, the acidolysis products were coumarone, stilbene, and formaldehyde, generated from the intermediate benzylium ion following the ring opening while the side chains were kept intact.…”

Section: Introductionmentioning

confidence: 99%

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Revealing Structural Modifications of Lignin in Acidic γ-Valerolactone-H2O Pretreatment

Zhao

Yue

et al. 2020

Polymers

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γ-valerolactone (GVL)/H2O/acid solvent mixtures has been used in chemical pretreatment of lignocellulosic biomass, it was claimed that GVL lignins were structurally close to proto (native) lignins, or having low molecular weight with narrow polydispersity, however, the structural changes of GVL lignins have not been investigated. In this study, β-O-4 (β-aryl ether, GG), β-5 (phenylcoumaran), and β-β (resinol) lignin model compounds were treated by an acidic GVL-H2O solvent system, a promising pretreatment of lignocellulose for biomass utilization, to investigate the structural changes possibly related to the lignin involved. NMR characterization of the products isolated from the treated GG indicated that a phenyl dihydrobenzofuran, having typical C-H correlations at δC/δH 50.74/4.50 and 93.49/4.60 ppm in its HSQC spectrum, was produced from GG. In the pretreatment, the released formaldehyde from GG reacted fast with GG to form a novel 1,3-dioxane intermediate whose characteristic HSQC signals were: δC/δH 94.15–94.48/4.81–5.18 ppm and 80.82–83.34/4.50–4.94 ppm. The β-5 model, dihydrodehydrodiconiferyl alcohol, was converted into phenylcoumarone and stilbene having benzaldehyde that resulted from the allyl alcohol side chain. The β-β model, syringaresinol, was isomerized to form a mixture of syringaresinol, epi-, and dia-syringaresinol although being degraded slightly.

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Acid Reactions of Lignin Models of β-5 Type

Cited by 22 publications

References 13 publications

Metal Triflates for the Production of Aromatics from Lignin

Metal Triflates for the Production of Aromatics from Lignin

Hybrid Catalytic Biorefining of Hardwood Biomass to Methylated Furans and Depolymerized Technical Lignin

Revealing Structural Modifications of Lignin in Acidic γ-Valerolactone-H2O Pretreatment

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