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The utilization of lignin in material fabrication has garnered significant attention despite its complex structure that greatly limits its applications. This study reports a green method for grading and modifying lignin to prepare stable hydrophobic coatings via the solvent/anti-solvent (ethanol/water) self-assembly method. First, the formic acid lignin particle (FLP) is prepared and the underlying mechanism is primarily ascribed to the hydrogen bonding, π–π interactions among aromatic groups within and between molecules, and hydrophobic interactions. The lignin nanoparticles were utilized to chelate with metal ions (iron) in order to obtain the stable hydrophobic coatings using the special nanostructures of FLP. This hydrophobic coating could be applied to different substrates (blocks, straw, and fabric). The cotton fabric exhibited an initial water contact angle (WCA) that increased from 73.4° to 129.6°, and excellent chemical and physical hydrophobic performance. Moreover, this coating has strong self-cleaning ability and could be used for oil–water separation. In this newly proposed fabrication, ethanol can be recovered in the preparation of lignin nanoparticles, which makes the green and facile preparation of a stable hydrophobic coating possible. Additionally, this work is important in upgrading formic acid lignin by controlling the polarity into value-added hydrophobic materials via green classification. [ABSTRACT FROM AUTHOR]

Lignin is the second largest component of vascular plants and is the most abundant renewable aromatic polymer on our planet. The attractiveness of lignin valorization lies in its conversion into high value aromatic chemicals and biofuels through fractionation and upgrading. The literature has demonstrated that the presence of aryl ether bonds in native lignin was a key factor for the conversion, while the conventional technical lignins from carbohydrate-first processes, e.g. pulp and cellulose ethanol production, are intensively condensed and lack these linkages due to the intense delignification conditions. Here, by using the β-O-4 lignin model dimer GG, we reveal the dramatic degradation of GG and the synchronous formation of relatively stable intermediate β-O-4 dimers, C6C3 enol ether and the formylated enol ether, within the first 5 min under the conditions of 72 wt% aqueous formic acid and 130 °C, conditions suitable for biomass fractionation. Based on these findings, we propose a simple but effective strategy of rapid flow-through fractionation (RFF), which separates the dissolved lignin from the reactor in time and space, thereby preserving these labile aryl ether bonds in native lignin. The application of RFF of poplar wood with a short residence time of 2.6 min attained 75% delignification with an equivalent of the β-O-4 motif in native lignin. Structure-preserved lignins (β-O-4 retention, 75.0%–85.4%) were also harvested from wheat straw with good lignin yields (61.7%–78.5%). Contrarily, batch fractionation acted as a protracted war and resulted in extensive cleavage of aryl ether bonds as suggested by 92%–100% loss of the β-O-4 motif under the same conditions. Because of the well-preserved structure, RFF lignin can be used as a good feedstock to boost its downstream valorization, especially for hydrogenolysis into monophenolic chemicals and fuels. It is noteworthy that the carbohydrate fraction from RFF retained structural integrity and almost reached theoretical yields for glucan and xylan. [ABSTRACT FROM AUTHOR]

Whole valorization of carbohydrate and lignin from biomass was achieved by rapid flow‐through fractionation (RFF) within 15 min. Wheat straw was effectively deconstructed into its principle components without degradation by using easily recyclable aqueous formic acid (72 wt %) at 130 °C. The obtained cellulose‐rich solid showed a nearly complete glucan recovery and 73.8 % glucose conversion after enzymatic hydrolysis. Xylan also reached full recovery with negligible furfural formation with a sum of 80 % of oligo/mono xylose in spent liquor and 20 % of xylan remaining in the solid. Up to 75.4 % lignin was dissolved in the spent liquor and further fractionated into water‐insoluble (WIL) and water‐soluble lignin (WSL) by dilution with water. WIL showed a non‐condensed and well‐preserved structure with 84.5 % β‐O‐4 remaining, which is believed to be beneficial for catalytic conversion into low‐molecular‐weight chemicals and fuels. The concentration of employed formic acid was below the formic acid/water azeotrope, and therefore the reaction medium could be restored through simple distillation. Together with the joint valorization of lignin and carbohydrates, the presented RFF is a promising process for sustainable biorefinery. Whole valorization of carbohydrate and lignin from biomass is achieved by rapid flow‐through fractionation within 15 min. Wheat straw is effectively deconstructed into its principle components without degradation by using easily recyclable aqueous formic acid (72 wt %) at 130 °C. The obtained cellulose‐rich solid shows a nearly complete glucan recovery and 73.8 % glucose conversion after enzymatic hydrolysis. [ABSTRACT FROM AUTHOR]

To promote the efficient utilization of lignocellulosic materials, one-step fractionation by formic acid-based organosolv process under pressure has been studied for converting lignocellulose in its main components. Lignin and hemicelluloses were selectively dissolved, while cellulose was not obviously degraded. Under optimized conditions (85% formic acid, a liquor-to-solid ratio of 7:1, and a temperature of 145°C for 45 min), this process provided a high efficient way to separate the main components of bamboo, obtaining 42.2% cellulose pulp, 31.5% lignin, 8.5% hemicellulose-rich fraction, 3.56% furfural and 3.80% acetic acid. Cellulose pulp with satisfying viscosity could easily be bleached to a high brightness of over 87% ISO with a short bleaching sequence, and had an acceptable paper strength properties. The recovered lignin fraction contained a small amount of carbohydrates and a considerable part of proteins and p-hydroxycinnamates. Additionally, the organic substances in hemicellulose-rich fraction obtained was composed of 95% carbohydrates, most of which was monosaccharides, as well as 5% lignin. [ABSTRACT FROM AUTHOR]

Integrated fractionation process based on autohydrolysis (H) and subsequent formic acid delignification (FAD) has been considered as an effective strategy to separate the main lignocellulosic components in view of the biorefinery. For the better understanding of the structural changes of the lignin during the integrated process, the fractionated aspen lignins were thoroughly characterized by Fourier transform infrared (FT IR), 13C, two-dimensional heteronuclear single quantum coherence (2D-HSQC) and 31P nuclear magnetic resonance (NMR) spectroscopy, gel permeation chromatography (GPC), and thermogravimetric analysis (TGA). Compared to the milled wood lignin (MWL), the fractionated lignins had higher amounts of phenolic OH groups as due to the cleavage of β-O-4 linkages and less alcoholic OH groups mainly due to the esterification of the aliphatic OH groups by formic acid. Demethylation action of the lignin was not significant during the FAD process. More syringyl-propane (S) units were extracted during the H-FAD process than guaiacyl-propane (G) units resulting in a higher S/G ratio and more OCH 3 in the fractionated lignins. Furthermore, autohydrolysis of aspen at higher temperature led to more condensation of the fractionated lignins which exhibited higher molecular weight and more β-5 and β-β linkages. The fractionated lignins exhibited high purities due to the breakage of the lignin-carbohydrate bonds. • Lignin with high phenolic OH and OCH 3 and high purity was obtained. • Aliphatic OH group was highly esterified by formic acid. • β-O-4 cleavage accompanied by formation of condensed aromatic structure • Autohydrolysis led to higher molecular weight and less formate ester in lignin [ABSTRACT FROM AUTHOR]

Highly hydrophobic fabrics by chelating lignin (alkali lignin, sodium lignin sulfonate and formic acid lignin) with metal ions (Fe3+, Fe2+ and Cu2+) were prepared with the surface wettability from superhydrophilic to highly hydrophobic. The lignin/metal chelated particles are in-situ deposited onto the fabric surface using dip-coating. Different lignin/metal ion system influenced the construction of hierarchical surface roughness and energy of fabrics greatly. Specially, the formation of homogeneous spherical particles on surface contributed to the minimal contact area of water droplets and fabric, and thus avoiding their adherence. The surface morphology results showed that the active groups of lignin is closely related with the surface roughness. It was found that the alkali (AL)/FeⅢ@cotton fabric achieved a maximum water CA value of 149.9° and a low surface energy of 1.90 mN/m. Its oil-water separation efficiency was higher than 99.9% and the resultant AL/FeⅢ@cotton fabric owned an excellent stability and suitability under harsh conditions. Collectively, this work is greatly significant for achieving the high-value utilization of lignin in wastewater treatments. [Display omitted] ● In-situ deposition of lignin/metal ion lowered the surface energy of fabrics. ● Phenolic hydroxyl content of lignin affected the size of lignin/metal chelates. ● Deposited lignin/metal chelates influenced the durable hydrophobicity of fabrics. ● Al/Fe3+ conferred the fabric highest hydrophobicity with the WCA value of 149.9°. ● The resultant fabric exhibited an excellent oil-water separation and stability. [ABSTRACT FROM AUTHOR]

Bamboo chips were efficiently fractionated using an integrated process of autohydrolysis and formic acid to induce rapid delignification. Autohydrolysis pretreatment facilitated oligosaccharide production, while the subsequent rapid-delignification using formic acid at a low liquid/solid ratio with a relatively short reaction time allowed obtaining cellulose fibers and lignin. The major inter-unit linkages of side-chain in lignin were cleaved during the combined fractionation process. The lignin fraction exhibited higher purity, more phenolic OH groups, less condensed phenolic OH groups, and higher syringyl/guaiacyl ratio (S/G) as compared to MWL and formic acid lignin from the direct formic acid delignification. These results indicate that the combined fractionation process presents a promising approach to the commercial utilization in the biorefinery industry. [ABSTRACT FROM AUTHOR]

Formic acid/water binary solvent extraction with formic acid fraction lower than 77.5% (w/w) of azeotrope was used to extract hemicellulose-derived saccharides from poplar wood at various levels of severity. The highest xylose yield of 77.8% and arabinose yield of 93.5% were obtained at 120 °C and 1 h. To reduce cellulose hydrolysis and facilitate downstream xylose crystallization, mild conditions at 90 °C and 4 h was chosen as optimum severity, which led to the highest xylose fraction of 81.7% in all saccharides extracted, with a remarkable xylose yield of 73.1%. Mass balance analysis showed that 5.84% of xylan was degraded, but only 0.25% of xylan ended up as furfural at optimum severity. The proposed extraction process has high feasibility for industrial application since the low formic acid fraction in solvent allows simple recovery and concentration of used solvent. [ABSTRACT FROM AUTHOR]

Bamboo was fractionated using formic acid based on a one-step organosolv process under high pressure (at 145 °C for 45 min, 0.3 MPa) and at atmospheric pressure (at 101 °C for 120 min), respectively. High-pressure formic acid lignin, atmospheric formic acid lignin and milled wood lignin of bamboo were subjected to comprehensive structural characterization using gel permeation chromatography (GPC), Fourier transform infrared (FTIR) and solution-state NMR techniques ( 1 H, 13 C, 2D-HSQC, and 31 P-NMR spectroscopies). The results indicated that the formic acid fractionation under high pressure presents a quick and efficient delignification method by enhancing the cleavage of interunitary bonds in lignin (β-O-4′, β-β and β-5′), and dissolved lignin also occurred condensation reaction. As compared to atmospheric formic acid lignin, high-pressure formic acid lignin obtained showed higher purity and yield, and had relatively higher contents of phenolic and carboxylic groups. [ABSTRACT FROM AUTHOR]

[Display omitted] • Poplar was pretreated by reusable organic solvent under mild temperature (≤100 °C). • Almost all hemicelluloses and part of lignin was extracted with cellulose retained. • Sulfonic acid groups were introduced into lignin structure remained in substrates. • 89% improved glucose conversion compared with that of non-sulfonated substance. • New strategy is exploited to realize sulfonation and promote biomass bioconversion. Biomass pretreatment is an essential strategy to overcome biomass recalcitrance and promote lignocellulosic bioconversion. Here, a reusable organic solvent system (formic acid-methanesulfonic acid) was explored to pretreat poplar under a mild temperature (below 100 °C). The results showed that the co-solvent system could extract basically complete hemicelluloses and part of lignin with original cellulose retained in the pretreated substrates. Meanwhile, sulfonic acid groups were introduced into lignin structure remained in the substrates. The glucose conversion yield of the substrates with a higher concentration of sulfonic acid groups (13.2 mmol/kg) reached 45.9 % by reducing the hydrophobic interaction between lignin and cellulase, showing 89.3 % improvement compared with that of the substrates treated with single formic acid. This progressive study aimed to develop a new strategy to realize sulfonation and promote enzymatic hydrolysis of substrates by using mild organic solvent pretreatment. [ABSTRACT FROM AUTHOR]