Investigation of Reaction Pathways Involved in Lignin Maturation

Buchanan, A. C.; Britt, Phillip F.; Struss, John A.

doi:10.1021/ef9601273

Cited by 15 publications

(16 citation statements)

References 15 publications

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“…140 Th e physical structure of the biomass would be kept to a large extent, which has been observed in nature. 36 Fischer-Tropsch-type reactions have been observed under hydrothermal conditions, too.…”

Section: Other Mechanismsmentioning

confidence: 99%

Hydrothermal carbonization of biomass: A summary and discussion of chemical mechanisms for process engineering

Funke

Ziegler

2010

Biofuels Bioprod Bioref

1,557

1,028

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Hydrothermal carbonization can be defined as combined dehydration and decarboxy lation of a fuel to raise its carbon content with the aim of achieving a higher calorific value. It is realized by applying elevated temperatures (180-220 o C) to biomass in a suspension with water under saturated pressure for several hours. With this conversion process, a lignite-like, easy to handle fuel with well-defined properties can be created from biomass residues, even with high moisture content. Thus it may contribute to a wider application of biomass for energetic purposes. Although hydrothermal carbonization has been known for nearly a century, it has received little attention in current biomass conversion research. This review summarizes knowledge about the chemical nature of this process from a process design point of view. Reaction mechanisms of hydrolysis, dehydration, decarboxylation, aromatization, and condensation polymerization are discussed and evaluated to describe important operational parameters qualitatively. The results are used to derive fundamental process design im provements.

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Section: Other Mechanismsmentioning

confidence: 99%

Hydrothermal carbonization of biomass: A summary and discussion of chemical mechanisms for process engineering

Funke

Ziegler

2010

Biofuels Bioprod Bioref

1,557

1,028

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“…We have also been exploring in depth the effects of restricted mass transport on pyrolysis reaction mechanisms for a variety of fossil and biomass model compounds. , Mass transport limitations are known to impact the global kinetics as well as product yields and distribution in the thermochemical processing of fossil − and renewable − organic energy resources. In our studies, restricted mass transport has been simulated through covalent attachment of the model compounds to a silica surface by means of a thermally robust Si−O−C aryl linkage (Figure ).…”

Section: Introductionmentioning

confidence: 99%

“…Our pyrolysis research has begun to focus on heteroatom-containing model compounds, in particular those containing oxygen functional groups, such as ethers 10,11,13 and carboxylic acids, because of their prevalence in lignins and low rank coals and the lack of detailed mechanistic understanding compared with hydrocarbon models. Studies of silica-immobilized benzyl phenyl ether (BPE), a model for α-aryl ether linkages in lignin, revealed a much more complicated reaction scheme than previously observed in fluid phases 13a. Significant rearrangement chemistry occurred through two competitive free-radical pathways that were promoted by the diffusional constraints.…”

Section: Introductionmentioning

confidence: 99%

Impact of Restricted Mass Transport on Pyrolysis Pathways for Aryl Ether Containing Lignin Model Compounds

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Pyrolysis studies have been conducted at 375 °C on several silica-immobilized phenethyl phenyl ether (PPE) model compounds, representative of related β-O-4 aryl ether linkages in lignin, to explore the impact of restricted mass transport on reaction pathways. As found previously for fluid-phase PPE, two competitive free-radical decay pathways are operative including a significant rearrangement pathway involving an O,C-phenyl shift for surface-attached PhCH2CH•OPh radicals. The selectivity for the rearrangement pathway is found to be sensitive to substituents and, in particular, to the structure of neighboring spacer molecules on the surface. In contrast to solution-phase behavior, dilution of PPE molecules on the surface with rigid aromatic spacers such as biphenyl or naphthalene hinder the rearrangement path. This phenomenon, attributed to steric constraints that decrease the rate of the 1,2-phenyl shift, is not observed when a more flexible spacer molecule (diphenylmethane) is employed. An improved knowledge of the pathways involved is important since this rearrangement pathway, which was also observed in the pyrolysis of α-aryl ether models, can result in the formation of valuable chemicals (aryl aldehydes and ketones) or undesirable refractory compounds (biphenyls and diphenylmethanes) during the thermochemical processing of lignin.

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“…Acid-exchanged clay catalysts (monmorillonite) have been reviewed by Buchanan et al (1997), with the advantage that these materials are layered to increase the surface area. The typical metal catalyst Ni-Co-Mo-W (less than 1 micron dia) is supported on the inorganic salt or clay (Stamires et al, 2006).…”

Section: Concept Under Reviewmentioning

confidence: 99%

Final Report: Investigation of Catalytic Pathways for Lignin Breakdown into Monomers and Fuels

Gluckstein¹,

Hu²,

Kidder³

et al. 2010

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Investigation of Reaction Pathways Involved in Lignin Maturation

Cited by 15 publications

References 15 publications

Hydrothermal carbonization of biomass: A summary and discussion of chemical mechanisms for process engineering

Hydrothermal carbonization of biomass: A summary and discussion of chemical mechanisms for process engineering

Impact of Restricted Mass Transport on Pyrolysis Pathways for Aryl Ether Containing Lignin Model Compounds

Final Report: Investigation of Catalytic Pathways for Lignin Breakdown into Monomers and Fuels

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