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1.
ChemSusChem ; 2020 Jul 21.
Artigo em Inglês | MEDLINE | ID: mdl-32692480

RESUMO

Increases in coniferaldehyde content, a minor lignin residue, significantly improves the sustainable use of plant biomass for feed, pulping, and biorefinery without affecting plant growth and yields. Herein, different analytical methods are compared and validated to distinguish coniferaldehyde from other lignin residues. It is shown that specific genetic pathways regulate amount, linkage, and position of coniferaldehyde within the lignin polymer for each cell type. This specific cellular regulation offers new possibilities for designing plant lignin for novel and targeted industrial uses.

2.
ChemSusChem ; 2020 Apr 13.
Artigo em Inglês | MEDLINE | ID: mdl-32281748

RESUMO

Organosolv pulping releases reactive monomers from both lignin and hemicellulose by the cleavage of weak C-O bonds. These monomers recombine to form undesired polymers through the formation of recalcitrant C-C bonds. Different strategies have been developed to prevent this process by stabilizing the reactive monomers (i.e., lignin-first approaches). To date, all reported approaches rely on the addition of capping agents or metal-catalyzed stabilization reactions, which usually require high pressures of hydrogen gas. Herein, a metal- and additive-free approach is reported that uses zeolites as acid catalysts to convert the reactive monomers into more stable derivatives under organosolv pulping conditions. Experiments with model lignin compounds showed that the recondensation of aldehydes and allylic alcohols produced by the cleavage of ß-O-4' bonds was efficiently inhibited by the use of protonic ß zeolite. By applying a zeolite with a preferred pore size, the bimolecular reactions of reactive monomers were effectively inhibited, resulting in stable and valuable monophenolics. The developed methodology was further extended to birch wood to yield monophenolic compounds and value-added products from carbohydrates.

3.
Chem Sci ; 10(12): 3681-3686, 2019 Mar 28.
Artigo em Inglês | MEDLINE | ID: mdl-30996963

RESUMO

The idea of using biaryl structures to generate synthetic building blocks such as spirolactones is attractive because biaryl structures are abundant in biomass waste streams. However, the inertness of aromatic rings of biaryls makes it challenging to transform them into functionalized structures. In this work, we developed photoinduced dearomatization of nonphenolic biaryl compounds to generate spirolactones. We demonstrate that dearomatization can be performed via either aerobic photocatalysis or anaerobic photooxidation to tolerate specific synthetic conditions. In both pathways, dearomatization is induced by electrophilic attack of the carboxyl radical. The resulting spirodiene radical is captured by either oxygen or water in aerobic and anaerobic systems, respectively, to generate the spirodienone. These methods represent novel routes to synthesize spirolactones from the biaryl motif.

4.
ChemSusChem ; 9(23): 3280-3287, 2016 Dec 08.
Artigo em Inglês | MEDLINE | ID: mdl-27860308

RESUMO

The pulping industry could become a biorefinery if the lignin and hemicellulose components of the lignocellulose are valorized. Conversion of lignin into well-defined aromatic chemicals is still a major challenge. Lignin depolymerization reactions often occur in parallel with irreversible condensation reactions of the formed fragments. Here, we describe a strategy that markedly suppresses the undesired condensation pathways and allows to selectively transform lignin into a few aromatic compounds. Notably, applying this strategy to woody biomass at organosolv pulping conditions, the hemicellulose, cellulose, and lignin were separated and in parallel the lignin was transformed into aromatic monomers. In addition, we were able to utilize a part of the lignocellulose as an internal source of hydrogen for the reductive lignin transformations. We hope that the presented methodology will inspire researchers in the field of lignin valorization as well as pulp producers to develop more efficient biomass fractionation processes in the future.


Assuntos
Biomassa , Fracionamento Químico/métodos , Lignanas/química , Madeira/química , Celulose/isolamento & purificação , Hidrocarbonetos Aromáticos , Lignanas/isolamento & purificação , Lignina/química , Polissacarídeos/isolamento & purificação
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