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Catalytic Oxidation of Lignins into the Aromatic Aldehydes: General Process Trends and Development Prospects

This review discusses principal patterns that govern the processes of lignins’ catalytic oxidation into vanillin (3-methoxy-4-hydroxybenzaldehyde) and syringaldehyde (3,5-dimethoxy-4-hydroxybenzaldehyde). It examines the influence of lignin and oxidant nature, temperature, mass transfer, and of othe...

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Autores principales: Tarabanko, Valery E., Tarabanko, Nikolay
Formato: Online Artículo Texto
Lenguaje:English
Publicado: MDPI 2017
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5713389/
https://www.ncbi.nlm.nih.gov/pubmed/29140301
http://dx.doi.org/10.3390/ijms18112421
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author Tarabanko, Valery E.
Tarabanko, Nikolay
author_facet Tarabanko, Valery E.
Tarabanko, Nikolay
author_sort Tarabanko, Valery E.
collection PubMed
description This review discusses principal patterns that govern the processes of lignins’ catalytic oxidation into vanillin (3-methoxy-4-hydroxybenzaldehyde) and syringaldehyde (3,5-dimethoxy-4-hydroxybenzaldehyde). It examines the influence of lignin and oxidant nature, temperature, mass transfer, and of other factors on the yield of the aldehydes and the process selectivity. The review reveals that properly organized processes of catalytic oxidation of various lignins are only insignificantly (10–15%) inferior to oxidation by nitrobenzene in terms of yield and selectivity in vanillin and syringaldehyde. Very high consumption of oxygen (and consequentially, of alkali) in the process—over 10 mol per mol of obtained vanillin—is highlighted as an unresolved and unexplored problem: scientific literature reveals almost no studies devoted to the possibilities of decreasing the consumption of oxygen and alkali. Different hypotheses about the mechanism of lignin oxidation into the aromatic aldehydes are discussed, and the mechanism comprising the steps of single-electron oxidation of phenolate anions, and ending with retroaldol reaction of a substituted coniferyl aldehyde was pointed out as the most convincing one. The possibility and development prospects of single-stage oxidative processing of wood into the aromatic aldehydes and cellulose are analyzed.
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spelling pubmed-57133892017-12-07 Catalytic Oxidation of Lignins into the Aromatic Aldehydes: General Process Trends and Development Prospects Tarabanko, Valery E. Tarabanko, Nikolay Int J Mol Sci Review This review discusses principal patterns that govern the processes of lignins’ catalytic oxidation into vanillin (3-methoxy-4-hydroxybenzaldehyde) and syringaldehyde (3,5-dimethoxy-4-hydroxybenzaldehyde). It examines the influence of lignin and oxidant nature, temperature, mass transfer, and of other factors on the yield of the aldehydes and the process selectivity. The review reveals that properly organized processes of catalytic oxidation of various lignins are only insignificantly (10–15%) inferior to oxidation by nitrobenzene in terms of yield and selectivity in vanillin and syringaldehyde. Very high consumption of oxygen (and consequentially, of alkali) in the process—over 10 mol per mol of obtained vanillin—is highlighted as an unresolved and unexplored problem: scientific literature reveals almost no studies devoted to the possibilities of decreasing the consumption of oxygen and alkali. Different hypotheses about the mechanism of lignin oxidation into the aromatic aldehydes are discussed, and the mechanism comprising the steps of single-electron oxidation of phenolate anions, and ending with retroaldol reaction of a substituted coniferyl aldehyde was pointed out as the most convincing one. The possibility and development prospects of single-stage oxidative processing of wood into the aromatic aldehydes and cellulose are analyzed. MDPI 2017-11-15 /pmc/articles/PMC5713389/ /pubmed/29140301 http://dx.doi.org/10.3390/ijms18112421 Text en © 2017 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).
spellingShingle Review
Tarabanko, Valery E.
Tarabanko, Nikolay
Catalytic Oxidation of Lignins into the Aromatic Aldehydes: General Process Trends and Development Prospects
title Catalytic Oxidation of Lignins into the Aromatic Aldehydes: General Process Trends and Development Prospects
title_full Catalytic Oxidation of Lignins into the Aromatic Aldehydes: General Process Trends and Development Prospects
title_fullStr Catalytic Oxidation of Lignins into the Aromatic Aldehydes: General Process Trends and Development Prospects
title_full_unstemmed Catalytic Oxidation of Lignins into the Aromatic Aldehydes: General Process Trends and Development Prospects
title_short Catalytic Oxidation of Lignins into the Aromatic Aldehydes: General Process Trends and Development Prospects
title_sort catalytic oxidation of lignins into the aromatic aldehydes: general process trends and development prospects
topic Review
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5713389/
https://www.ncbi.nlm.nih.gov/pubmed/29140301
http://dx.doi.org/10.3390/ijms18112421
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