Modellversuche zur Ligninfrage

Freudenberg, Karl; Richtzenhain, Hermann; Flickinger, Erich; Engler, Kurt

doi:10.1002/cber.19390720927

Cited by 9 publications

(6 citation statements)

References 4 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…1£ ligninsulfonic acid from cuproxam-lignin is SUbj ected to further sulfite treatment the sulfur content can be raised to 8.6 per cent (85). Following methylation and oxidation such a preparation yields 2.8 per cent veratric acid and 3.8 per cent isohemipinic acid (85). Part of the sulfonic acid groups could have reacted with carbinols which are adj acent to benzene rings (compare XIX).…”

Section: Aceto Vanillonementioning

confidence: 98%

“…To this must be added the free phenol groups resulting from the cleavage of the greater portion of the formaldehyde from the methylenedioxy groups, for only 0.6 per cent formaldehyde is detectable in ligninsulfonic acid. 1£ ligninsulfonic acid from cuproxam-lignin is SUbj ected to further sulfite treatment the sulfur content can be raised to 8.6 per cent (85). Following methylation and oxidation such a preparation yields 2.8 per cent veratric acid and 3.8 per cent isohemipinic acid (85).…”

Section: Aceto Vanillonementioning

confidence: 99%

“…The excess (9 per cen t) of oxygen may be regarded as combined in ether link ages, the extent of which is app ro ximat ely equivalent to the methoxyl and hydroxyl groups present. The me tho xy l group occurs primarily in the guaiacol group (rV) and to a very small extent i n sy ringi c resi dues (VI) (72).…”

Section: Analytical Evidencementioning

confidence: 99%

See 2 more Smart Citations

Polysaccharides and Lignin

Freudenberg

1939

Annu. Rev. Biochem.

Self Cite

View full text Add to dashboard Cite

Section: Aceto Vanillonementioning

confidence: 98%

Section: Aceto Vanillonementioning

confidence: 99%

See 1 more Smart Citation

Polysaccharides and Lignin

Freudenberg

1939

Annu. Rev. Biochem.

Self Cite

View full text Add to dashboard Cite

“…Lignin accounts for 15–30% by weight and 40% by energy . It has a high potential as a feedstock for bulk and fine chemicals, especially aromatic compounds. , Lignin is an irregular macromolecule built from different phenolic monomers . The most promising method to depolymerize the lignin structure to get valuable chemicals ready for further treatment is pyrolysis, fast pyrolysis in particular .…”

Section: Introductionmentioning

confidence: 99%

Mechanism of Fast Pyrolysis of Lignin: Studying Model Compounds

et al. 2014

View full text Add to dashboard Cite

Fast pyrolysis of lignin is one of the most promising methods to convert the complex and irregular structure of lignin into renewable chemicals and fuel. During pyrolysis the complex set of radical reactions, rearrangements, and eliminations is influenced by temperature, pressure, and the lignin origin and structure. This model compound study aims to understand reaction pathways and how primary intermediates lead to the observed product selectivity. The pyrolysis microreactor directly connected to the gas chromatograph with a mass spectrometer (py-GC/MS) detects the final products, while imaging photoelectron photoion coincidence (iPEPICO) with VUV synchrotron radiation shows primary decomposition radicals. The tested model compounds, diphenylether (DPE) and ortho-methoxyphenol (guaiacol), represent a common lignin linkage and the most present subunit in lignin, respectively. Radical fragments, such as the hydroxycyclopentadienyl radical in guaiacol decomposition, are identified by mass-selected threshold photoelectron spectra (ms-TPES) in excellent agreement with the Franck-Condon simulation. While homolysis produces phenoxy-, phenyl-, and hydroxyphenoxy radicals, which are observed in high vacuum, radically initiated reactions are dominant in ambient conditions and produce recombination and rearrangement products, such as 2-hydroxybenzaldehyde in the case of guaiacol. The degree of substitution plays a dominant role in both the stabilization of the intermediate radical and the following degree of recombination. The recombination of phenoxy radicals is enhanced compared to hydroxy-phenoxy radicals.

show abstract

“…It has high potential as a feedstock for bulk and fine chemicals, especially aromatic and phenolic compounds . Lignin is polymerized from three phenolic monomers, resulting in a complex and irregular polymer that is very hard to characterize . A sample sketch of the lignin polymer together with the three building blocks: coniferyl, sinapyl, and coumaryl units, is provided in Scheme .…”

Section: Introductionmentioning

confidence: 99%

How Inter‐ and Intramolecular Reactions Dominate the Formation of Products in Lignin Pyrolysis

Custodis

Hemberger

Bokhoven

2017

Chemistry A European J

View full text Add to dashboard Cite

One of the key challenges in renewable chemical production is the conversion of lignin, especially by fast pyrolysis. The complexity of the lignin pyrolysis process has hindered the elucidation of the mechanism, inhibiting further industrial implementation. By combining pyrolysis of model compounds (4-phenoxyphenol and 2-methoxy-phenoxybenzene) with lignin bond characteristics both under vacuum and under realistic pressure conditions, the roles of inter- and intramolecular reactions were established. On the one hand, the stable 4-O-5 ether bond enables, without breaking, C-C bond formation and even directly forms naphthalene depending on the position and type of the substituent. p-Benzoquinone intermediates, on the other hand, are highly unstable at ambient pressure and directly decompose into coke and carbon monoxide. The system pressure (radical concentration) plays a crucial role in the dominant reaction mechanism by initiating intramolecular reactions, interfering with intramolecular reactions. H-transfer and recombination reactions suppress the decarbonylation of phenoxy radicals, thus yielding a very different product distribution.

show abstract

Modellversuche zur Ligninfrage

Cited by 9 publications

References 4 publications

Polysaccharides and Lignin

Polysaccharides and Lignin

Mechanism of Fast Pyrolysis of Lignin: Studying Model Compounds

How Inter‐ and Intramolecular Reactions Dominate the Formation of Products in Lignin Pyrolysis

Contact Info

Product

Resources

About