Mechanistic Differences Between Kraft and Soda-AQ Pulping of Hardwoods with Regard to Lignin–Carbohydrate Complexes (LCC)

Nicholson, David; Leavitt, Aaron; Stromberg, Bertil; Francis, Raymond C.

doi:10.1080/02773813.2017.1299184

Cited by 9 publications

(5 citation statements)

References 31 publications

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“…The main cross-signals in the 2D-HSQC spectra were assigned according to the literature − and are listed in Table S2. The main different region appeared at the carbohydrate regions (δC/δH 91–105/3.9–5.4 ppm), which are mainly assigned to the LCC structures . Signals were not observed in the HASO lignin, implying that LCC bonds were cleaved during the extended soda–oxygen pulping process.…”

Section: Resultsmentioning

confidence: 97%

“…The main different region appeared at the carbohydrate regions (δC/δH 91−105/3.9−5.4 ppm), which are mainly assigned to the LCC structures. 41 Signals However, the signals of β−β′ were weak, whereas those of β-5′ could not even be detected in the HASO lignin. Furthermore, a semiquantitative method was used to identify the relative abundance of the main structures as presented in Table S3.…”

Section: ■ Experimental Sectionmentioning

confidence: 97%

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High-Yield Preparation of Micro/Nanofibers from Rice Straw Using Superextended Soda–Oxygen Cooking and High-Intensity Ultrasonication

Zhang

Chen

2019

ACS Sustainable Chem. Eng.

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Chemical purification through ultrasonic treatment as a method to prepare energy-saving and environmentally friendly nanofiber from natural lignocellulose has attracted wide attention in academic research. However, purifying cellulose through chemical pretreatment is complicated and inefficient, making it one of the bottlenecks that plague its industrial application. In this paper, the superextended soda–oxygen pulping process successfully purified rice straw cellulose fibers (total lignin 1.57%). Results showed that 82% of the hemicellulose can be removed with a high yield of 43.05% (w/w dry rice straw). In addition, micro/nanofibers can be isolated from the purified cellulose after the conventional ultrasonic process (2000 W, 2 h). The transmission electron microscope shows that the obtained micro/nanofibers were interconnected with fiber bundles, which formed entangled, weblike networks in the suspension. The thermogravimetric analysis results indicated that the degradation temperature of the micro/nanofibers can be increased to approximately 335 °C compared with that of 300 °C of the conventional pulp. After a simple vacuum filtration, a highly transparent film with a smooth surface was produced from micro/nanofibers. The production process has low cost, stable product quality, and high yield, and it is also easy to use in industrial production.

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Section: Resultsmentioning

confidence: 97%

Section: ■ Experimental Sectionmentioning

confidence: 97%

High-Yield Preparation of Micro/Nanofibers from Rice Straw Using Superextended Soda–Oxygen Cooking and High-Intensity Ultrasonication

Zhang

Chen

2019

ACS Sustainable Chem. Eng.

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“…For the possible mechanism (Figure ), the AQ first reacts with the end aldehyde group of the carbohydrate fiber to the stable carboxylic acid because of its oxidation property, which can protect the cellulose fiber by restraining the unwanted peeling reaction. In addition, the generated carbanion intermediate (H-AQ – ) can further combine with the quinone methide intermediate (QM, 12c ) generated from phenolic β-O-4 linkage alkaline hydrolysis ( 12a → 12c ) or phenolic group oxidation with RO• radical release at C α . Then, the base-promoted ingenious molecular rearrangement in 12d causes the cleavage of the generated C α –C H‑AQ bond (bold in red) to release one AQ for the next oxidation cycle and two phenolic anions ( 12e and 12f ) after the cleavage of the C β –OAr bond.…”

Section: Anionic Intermediatesmentioning

confidence: 99%

Catalytic Strategies and Mechanism Analysis Orbiting the Center of Critical Intermediates in Lignin Depolymerization

et al. 2023

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Lignin, as a precious resource given to mankind by nature with abundant functional aromatic structures, has drawn much attention in the recent decade from academia to industry worldwide, aiming at harvesting aromatic compounds from this abundant and renewable natural polymer resource. How to efficiently depolymerize lignin to easy-to-handle aromatic monomers is the precondition of lignin utilization. Many strategies/methods have been developed to effectively degrade lignin into monomers, such as the traditional methods of pyrolysis, gasification, liquid-phase reforming, solvolysis, chemical oxidation, hydrogenation, reduction, acidolysis, alkaline hydrolysis, alcoholysis, as well as the newly developed redox-neutral process, biocatalysis, and combinatorial strategies. Therefore, there is a strong demand to systemically summarize these developed strategies and methods and reveal the internal transformation principles of the lignin. Focusing on the topic of lignin depolymerization to aromatic chemicals, this review reorganizes and categorizes the strategies/methods according to their mechanisms, orbiting the center of critical intermediates during the lignin linkage transformation, which includes the critical anionic intermediates, cationic intermediates, organometallic intermediates, organic molecular intermediates, aryl cation radical intermediates, and neutral radical intermediates. The corresponding introduction involves the generation and the transformation chemistry of the critical intermediates via the corresponding C–H/O–H/C–C/C–O chemical bond transformations, leading to the cleavage of the C–C/C–O linkage bonds. Accompanying the brief introduction of lignin chemistry and the final concluding remarks and perspectives on lignin depolymerization, this review aims to provide a current research process of lignin depolymerization, which may provide useful suggestions for this vigorous research field.

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“…In the case of the kraft impregnation pre-treatment, however, chemical reactions are possible; hydroxyls on cellulose surfaces can react with quinone methides produced from lignin during pulping, to form covalent bonds. Some literature exists on this molecular mechanism option (Nicholson et al 2017). Such reactions should however be limited by the presence of hydrogen sulfide ions, which being stronger nucleophiles would result in cleavage rather than formation of LC linkages.…”

Section: Massmentioning

confidence: 99%

“…This could either be a stable native form or created during pulping. The creation mechanism would involve nucleophilic addition reactions to quinone methide intermediate (Nicholson et al 2017).…”

Section: Analysis Of Structure and Molar Massmentioning

confidence: 99%

On the effect of hemicellulose removal on cellulose-lignin interactions. - OPEN ACCESS

et al. 2017

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Mechanistic Differences Between Kraft and Soda-AQ Pulping of Hardwoods with Regard to Lignin–Carbohydrate Complexes (LCC)

Cited by 9 publications

References 31 publications

High-Yield Preparation of Micro/Nanofibers from Rice Straw Using Superextended Soda–Oxygen Cooking and High-Intensity Ultrasonication

High-Yield Preparation of Micro/Nanofibers from Rice Straw Using Superextended Soda–Oxygen Cooking and High-Intensity Ultrasonication

Catalytic Strategies and Mechanism Analysis Orbiting the Center of Critical Intermediates in Lignin Depolymerization

On the effect of hemicellulose removal on cellulose-lignin interactions. - OPEN ACCESS

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