Shangshang Ma

Lignin, a complex natural three-dimensional aromatic polymer, is prone to condensation during the separation process, owing to the diverse properties of its basic structural units, linkage types, and spatial configurations. These inherent structural complexities present significant challenges for its efficient isolation and precise transformation. Current separation techniques primarily include physical, chemical (such as acid hydrolysis, alkaline dissolution, organic solvents, and ionic liquids), and biological methods. Each approach offers distinct advantages and limitations in terms of yield, purity, cost, and impact on lignin structure. Studies have indicated that ionic liquids and organic solvent methods demonstrate considerable application potential owing to their mild reaction conditions and high selectivity. Future research should focus on developing green, efficient, and low-cost separation technologies, while also enhancing detailed structural characterization and targeted lignin conversion to facilitate its large-scale utilization in the production of value-added materials and chemicals.

Lignin, the most abundant renewable resource of aromatics in nature, is recognized as an alternative to fossil-based fuels and chemicals. In this study, a phosphomolybdic acid-ionic liquid (PMA-IL) [BSHMIM]H₂PMo₁₂O₄₀ was synthesized and used as a catalyst for further oxidative depolymerization of extracted lignin to prepare valuable chemicals. Under optimized conditions, the conversion of lignin reached 61.33%, and the total yield of target products (vanillin, vanillic acid, and methyl vanillate) was 28.00 mg·g^-1, where the selectivity of methyl vanillate reached 56.43%. The liquid products and residues obtained under the optimum conditions were analyzed, further confirming the advantages of PMA-IL compared with single PMA. In addition, this method also has an excellent catalytic effect for other types of lignin and presents a good substrate applicability. Finally, based on the research results of model compounds, the possible reaction pathway of the formation of vanillin, vanillic acid, and methyl vanillate was proposed.

Lignin, the second largest component of biomass, is considered as an important alternative source of fossil reserves for the production of fuels and chemicals. Here, we developed a novel method to oxidatively degrade organosolv lignin into value-added four-carbon esters, particularly diethyl maleate (DEM), with the cooperative catalyst consisting of 1-(3-sulfobutyl) triethylammonium hydrogen sulfate ([BSTEA]HSO4) and 1-butyl-3-methylimidazolium ferric chloride ([BMIM]Fe2Cl7). Under optimized conditions (1.00 MPa initial O2 pressure, 160 degrees C, 5 h), the lignin aromatic ring was effectively cleaved by oxidation to form DEM with a yield of 15.85% and a selectivity of 44.25% in the presence of the synergistic catalyst of [BMIM]Fe2Cl7- [BSMIM]HSO4 (1/3, mol/mol). The structure and composition analysis of lignin residues and liquid products confirmed that the aromatic units in lignin were effectively and selectively oxidized. Furthermore, the catalytic oxidation of lignin model compounds was explored for obtaining a possible reaction pathway of oxidative cleavage of lignin aromatic units to DEM. This study provides a promising alternative method for the production of traditional petroleum-based chemicals.

The facile, green, and efficient strategy for the separation of lignin from straw and subsequent production of value-added chemicals is crucial to the current utilization of straw. Herein, up to 23.72% of lignin was isolated from wheat stalk over cheap and green 1-(3-sulfobutyl) triethylammonium hydrogen sulfate ([BSTEA]HSO₄) in aqueous ethanol (V_ethanol: V_water = 4:1). The acquired lignin was verified as a p-hydroxyphenyl-guaiacyl-syringyl type, which had a narrower molecular weight distribution, better thermal stability, and higher purity compared with those of the lignin obtained using 1-methyl-3-(4-sulfobutyl)-imidazolium hydrogen sulfate and 1-(3-sulfobutyl) pyridinium hydrogen sulfate. Moreover, a carbohydrate-rich liquid containing [BSTEA]HSO₄ was obtained by water removal from the waste liquid after lignin separation and further converted to ethyl levulinate (EL) by a one-pot process in the presence of inexpensive and stable USY zeolite. The yield of EL reached 30.23% at 200 °C for 60 min over the presence of 40% [BSTEA]HSO₄ and 60% USY zeolite. Under optimal conditions, the yields of lignin and EL can respectively reach 83.89 and 72.28% of those catalyzed by a fresh catalyst after five cycles. In short, the above-mentioned methods present a green, economic, and efficient route for the extraction of lignin and further treatment of the liquid waste generated during the extraction process.

A facile strategy has been reported to anchor silver nanoparticles (Ag NPs) onto three-dimensional reduced graphene oxide (3D rGO) via a green and simple method. An accurate and reliable electrochemical sensing platform based on Ag NPs/3D rGO was designed for the ultrasensitive detection of rifampicin (RIF). The morphology and features of Ag NPs/3D rGO were characterized by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), Raman spectroscopy and electrochemical measurements. The interface of the modified electrode presented effective electrical activity for the analysis of RIF due to the large electrochemically active surface area and excellent electron transport ability. The sensor exhibited a good linear relationship in the range of 0.01 nM–45 μM and a low detection limit of 0.810 nM (S/N = 3). Crucially, the fabricated Ag NPs/3D rGO sensor was successfully utilized to assess RIF in human blood, drug and aquatic product samples. This sensing platform exhibited outstanding electrochemical performance for RIF detection and showed great potential application in clinical diagnosis, pharmaceutical and food-related fields.