Hardwood and softwood lignins from sulfite liquors: Structural characterization and valorization through depolymerization

Capacity of Aqueous Solutions of the Ionic Liquid 1-Ethyl-3-methylimidazolium Acetate to Partially Depolymerize Lignin at Ambient Temperature and Pressure

“…A number of lignin-derived compounds were identified in the post-treatment aqueous phases, with the full list and corresponding yields (interpreted as mass of compound per unit mass of the original Indulin AT) being given in Table S1 in the Supporting Information. Apart from the polyphenolic compound epicatechin, the two (monophenolic) compounds obtained in a higher yield are vanillin and guaiacol, in line with what has been typically reported in the depolymerization of kraft lignins. ,− These two substances are likely produced by the cleavage of β-O-4 bonds in the lignin polymeric structure by the action of the IL, , and further analysis will specifically focus on them. From a mechanistic perspective, and according to a suggestion from the literature, the cleavage of these β-O-4 bonds may take place heterolytically via a six-membered transition state, with participation of both cation and anion of the IL.…”

“…Focusing, for instance, on the particular case of vanillin, yields in the range of 25–100 g of vanillin per kg of lignin have been reported. ,,, Nevertheless, it must be noted that the latter yields were achieved through treatments involving stages with harsh conditions: very high pH (close to 14), temperatures over 150 °C, pressurization with molecular oxygen, and organic solvents, such as nitrobenzene. Different works, ,, in the quest for greener approaches, avoided the use of highly toxic organic solvents; and, although they maintained strongly alkaline conditions, O 2 pressurization, and temperatures never lower than 120 °C, their reported yields of vanillin decreased significantly, down to the range of 2.5–13 g of vanillin per kg of lignin. In this range also lie the yields reported in the present work, which in turn have been achieved by means of treatments at ambient pressure and temperature with the only involvement of a nonflammable IL with low toxicity.…”

“…Most of the efforts made to develop innovative processes to obtain products from lignin through its depolymerization involve, unfortunately, the use of solvents with poor green credentials and/or high temperatures and pressures. − One of the alternatives that has been explored in some works over the past decade is the use of ionic liquids (ILs), which have been credited with the potential to act as both solvents and catalysts in the depolymerization of lignin. , As compared to other solvents of organic nature, ILs can certainly improve the sustainability credentials of the lignin depolymerization processes thanks to inherent characteristics such as their extremely low vapor pressure (resulting in a lack of contribution of the solvent to atmospheric pollution and also beneficial effects in terms of process safety and health of plant operators). However, to date, the published research works exploring ILs for the valorization of lignin through its depolymerization have involved relatively harsh conditions: temperatures higher than 100 °C, oxygen pressures, additional metal/acid catalysts, etc .…”

Multiple Isothermal Amplification Coupled with CRISPR–Cas14a for the Naked-eye and Colorimetric Detection of Aflatoxin B1

“…In recent years, various methods for detecting AFB1 have been utilized, including high-performance liquid chromatography, tandem mass spectrometry, and enzyme-linked immunosorbent assays (ELISA). − However, these methods are expensive and time-consuming and require specialized personnel to operate in a laboratory setting. Researchers are therefore focused on developing new technologies that simplify sample preparation and yield more portable detection devices.…”

Theoretical investigation on the reaction mechanisms of O2‐initiated gas‐phase oxidation of lignin model compounds

“…Filipa and co‐workers studied the oxidation mechanism of obtained from hardwood and softwood sulfite liquors and evaluates the structural characteristics. The hardwood lignin generates mostly SAL through oxidation reaction initiated by O 2 , while softwood lignin mainly produces VAL [17]. Wei and co‐workers studied the reaction between lignin degradation products and laccase active sites using molecular docking technique, the results showed that the ortho ‐ substituted phenolic hydroxyl groups of lignin degradation products could maintain the stability of mediator conformation, and the electron donating ability of ortho ‐ substituted groups could improve the stability of radical intermediate [18, 19].…”