Products of hydrothermal treatment of lignin and the importance of ortho-directed repolymerization reactions

Jensen, Mads Mørk; Madsen, René B.; Becker, Jacob; Iversen, Bo B.; Glasius, Marianne

doi:10.1016/j.jaap.2017.05.009

Cited by 21 publications

(27 citation statements)

References 40 publications

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“…A detailed description and analytical characterization of the monomeric aromatic compounds is given in [28][29][30][31]. In addition to these monomers, a large proportion of dimeric and oligomeric structures are obtained having the following types of bonds: 5-5 (biphenyl bond), β-5 (phenylcoumaran), β-β (THF or resinol type) and β-1 (1, 2-diarylpropane).…”

Section: Mechanism Of Bond-breaking and Product Formationmentioning

confidence: 99%

“…This was clearly showed in the comparison of BCD of hardwood organosolv lignin with softwood kraft lignin. Syringol and dimethoxyphenols are found almost exclusively in the BCD-oil of organosolv lignin with a significant amount in the monomer phase [8,28,30]. Other studies focused on the investigation of one type of wood but with different pretreatment methods applied.…”

Section: Influence Of the Processing Conditionsmentioning

confidence: 99%

See 1 more Smart Citation

Base-Catalyzed Depolymerization of Lignin: History, Challenges and Perspectives

Rößiger¹,

Unkelbach²,

Pufky-Heinrich³

2018

Lignin - Trends and Applications

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Bio-based phenolic compounds available from lignin are promising candidates for industrial application, e.g., within polymer resins or as biogenic fuel substitutes. Among numerous conversion methods for the valorization of lignin, the base-catalyzed depolymerization (BCD) has considerable advantages with respect to other processes. By this method, lignin and lignin-containing biorefinery streams can be catalytically transferred to valuable, defined products with tailored specifications. Continuous process operation allows conversions at short residence times and, thus, enables its industrial implementation more easily due to economic reasons. This review reflects the development in the field of BCD on various types of lignin. A historical overview will be given and the principal application of the method is shown. Challenges for operations are addressed, mainly to the development of efficient and selective methods for product separation and purification of the alkylphenolic moieties and the reduction of char formation during the process. An outlook will be given by showing trends and perspectives, especially in the field of industrial applications. Here, hydrotreatment methods for refining BCD intermediates for fuel and platform chemical production are shown. Furthermore, the application of BCD for the conversion of woody biomass and black liquor is discussed.

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Section: Mechanism Of Bond-breaking and Product Formationmentioning

confidence: 99%

Section: Influence Of the Processing Conditionsmentioning

confidence: 99%

Base-Catalyzed Depolymerization of Lignin: History, Challenges and Perspectives

Rößiger¹,

Unkelbach²,

Pufky-Heinrich³

2018

Lignin - Trends and Applications

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“…It was not possible to analyze heavy molecular weight compounds comprised in BC2 using GC-MS or HPLC. The heavier fraction still contains oligolignols generated in the first depolymerization steps as well as repolymerization of lignin fractions [47]. Thus, we were unable to characterize the composition of BC2 with these analytical techniques, but representative infra-red spectra and molecular weight-average distributions of BC1 and BC2 were already given in a previous work [26], showing similarities with the lignin feedstock and demonstrating the higher average molecular weight of BC2, ranging from 1030 to 1400 g mol −1 .…”

Section: Analysis Of Htl Productsmentioning

confidence: 83%

Hydrothermal Depolymerization of Biorefinery Lignin-Rich Streams: Influence of Reaction Conditions and Catalytic Additives on the Organic Monomers Yields in Biocrude and Aqueous Phase

Dell’Orco

Miliotti²,

Lotti³

et al. 2020

Energies

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Hydrothermal depolymerization of lignin-rich streams (LRS) from lignocellulosic ethanol was successfully carried out in a lab-scale batch reactors unit. A partial depolymerization into oligomers and monomers was achieved using subcritical water as reaction medium. The influence of temperature (300–350–370 °C) and time (5–10 minutes) was investigated to identify the optimal condition on the monomers yields in the lighter biocrude (BC1) and aqueous phase (AP) fractions, focusing on specific phenolic classes as well as carboxylic acids and alcohols. The effect of base catalyzed reactions (2–4 wt. % of KOH) was compared to the control tests as well as to acid-catalyzed reactions obtained with a biphasic medium of supercritical carbon dioxide (sCO2) and subcritical water. KOH addition resulted in enhanced overall depolymerization without showing a strong influence on the phenolic generation, whereas sCO2 demonstrated higher phenolic selectivity even though no effect was observed on the overall products mass yields. In conclusion, a comparison between two different biocrude collection procedures was carried out in order to understand how the selected chemical extraction mode influences the distribution of compounds between BC1 and AP.

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“…Generally, it is observed that the alkyl group of the phenolic derivatives is placed in the ortho or para position. The importance of ortho-directed repolymerization from HTL of lignin has previously been shown 28 while para-repolymerization may also occur when the position is not substituted. The complexity of the biomass degradation means that many aldehydes and ketones may be formed from protein, carbohydrates, and lignin.…”

Section: Poplarmentioning

confidence: 93%

“…Hence, residual lignin from alkaline HTL may be better described as chemically modified lignin. 28 Even with thermochemolysis it was not possible to detect hydrocinnamic acids (see section 3.3).…”

Section: Poplarmentioning

confidence: 99%