Search

Two kinds of mesoporous carbon solid acids (LDMCE-SO3H and LDMCS-SO3H) were successfully prepared using masson pine alkali lignin as carbon source by evaporation-induced self-assembly (EISA) and salt-induced self-assembly (SISA) followed by sulfonation, respectively. In terms of preparation process, SISA (self-assembly in water and preparation time of 2 days) is greener and simpler than EISA (self-assembly in ethanol and preparation time of 7 days). The prepared LDMCE-SO3H and LDMCS-SO3H exhibit obvious differences in structural characteristics such as pore channel structure, specific surface area, mesopore volume and the density of -SO3H groups. Furthermore, the catalytic performances of LDMCE-SO3H and LDMCS-SO3H were investigated in the hydrolysis of microcrystalline cellulose in water, and the glucose yields of 48.99% and 54.42% were obtained under the corresponding optimal reaction conditions. More importantly, the glucose yields still reached 28.85% and 30.35% after five runs, and restored to 39.02% and 45.98% through catalysts regeneration, respectively, demonstrating that LDMCE-SO3H and LDMCS-SO3H have excellent recyclability and regenerability.

A sulfonated lignin-derived mesoporous carbon (LDMC-SO3H) was prepared from kraft lignin (KL) using phenolation and soft-template method followed by sulfonation. LDMC-SO3H bearing a sulfonic acid density of 0.65 mmol/g possessed a well-ordered 2D hexagonal mesoporous characteristics with mesopore volume of 0.067 cm3/g and specific surface area of 262 m2/g as well as mesopore size of 3.42 nm. A high 5-hydroxymethylfurfural (5-HMF) yield of 98.0% with a full fructose conversion was obtained using LDMC-SO3H as catalyst under the optimized reaction conditions of reaction temperature and time of 140 °C and 120 min, initial fructose concentration of 100 g/L, catalyst load of 0.1 mg/mg in DMSO. Furthermore, there was no obvious decrease in 5-HMF yield (≥95.0%) within the five-cycle experiment, highlighting the superior reusability and stability of LDMC-SO3H in fructose-to-5-HMF transformation.

Phenolation is an effective method to improve the reactivity of lignin in the synthesis of lignin–phenol–formaldehyde (LFP) resin. Previous lignin phenolation was almost exclusively catalyzed by ac...

Sulfonic acid-functionalized lignin-derived mesoporous carbon (LDM C-S O3H) was prepared using phenolation and evaporation induced self-assembly method followed by sulfonation. The obtained LDM C-S O3H bearing sulfonic acid density of 0.6528 mmol/g possessed a well-ordered two-dimensional hexagonal mesoporous characteristics. A 5-hydroxymethylfurfural (5-HMF) yield of 98.0% with a full fructose conversion was obtained using LDM C-S O3H as catalyst at 140 °C for 2 h in DMSO. Reactive kinetics studies revealed that fructose conversion in DMSO without catalyst or catalyzed by LDMC-SO3H may obey pseudo-first-order kinetics, and the activation energy of latter (72 kJ/mol) was much lower than that of former (114 kJ/mol). Adsorption kinetics studies indicated that almost no 5-HMF adsorbed onto LDM C-S O3H probably had a great contribution to the high selectivity of up to 98.0%, while the fructose adsorption on LDM C-S O3H was a diffusion-controlling adsorption process with more following Bangham kinetic model and Weber-Morris kinetic model owing to the characteristics of ordered mesostructure of LDM C-S O3H. Moreover, LDM C-S O3H exhibited superior reusability and stability in catalytic performance with a 5-HMF yield higher than 88.0% in six runs probably due to the synergistic effect of mesopore structure with a special surface and -SO3H groups with a relatively high content. These research results will contribute to a better understanding of structure-performance relationship of LDM C-S O3H used as an efficient catalyst in the fructose-to-5-HMF transformation as well as the high-value utilization of lignin in the field of catalysis.

Lignin can be used as a green and sustainable substitute for phenol in the preparation of ordered mesoporous carbon using phenol resin prepolymer as precursor owing to the availability of aromatic ortho-positions in the lignin structure. To further improve the reactivity towards formaldehyde and increase the substitution degree of phenol, masson pine alkali lignin (MAL) was pretreated by an acidic deep eutectic solvent (DES). It was found that adding an appropriate amount of water to DES showed beneficial attributions to the reduction in pretreatment time and the upsurge in the phenolic hydroxyl content of regenerated lignin (DAL). The content of β-O-4 ether bond in MAL was almost cleaved. More importantly, the contents of syringyl and guaiacyl units were decreased. In contrast, the content of p-hydroxyphenyl (H) units was increased obviously, thereby facilitating lignin to react with formaldehyde. Results showed that the optimized DAL with higher content of H units was an appropriate candidate for substituting 100% of phenol in the preparation of highly-ordered lignin-derived mesoporous carbon (LDMC). Finally, the optimized LDMC exhibited high specific capacitance of 197.32 F g-1 at current density of 0.2 A g-1, high capacitance retention of 84% at current density of 20 A g-1, superior cyclic stability with capacitance retention rate of 99.09% after 10000 cycles and high energy density of 6.85 Wh∙kg−1 at power density of 100 W kg−1.

Acidic carbonaceous solids were synthesized from mass pine alkali lignin via hydrothermal carbonization followed by sulfonation. Hydrothermal carbonization of lignin in the presence of acrylic acid (LAHC-SO3H) provided many more carboxylic groups than that in the absence of acrylic acid, allowing subsequent sulfonation to produce a highly active and stable catalyst for cellulose hydrolysis in the [BMIM]Cl-H2O solvent system. The hydrochar and catalyst were characterized using field emission scanning electron microscopy, X-ray diffractometer, X-ray photoelectron spectroscopy, thermal gravimetric analysis, Fourier transform infrared spectrometer, Brunauer–Emmett–Teller and acid–base titration. Results showed that a high acid content of 5.48 mmol/g, including carboxylic group (2.85 mmol/g), phenolic hydroxyl group (1.05 mmol/g) and sulfonic acid group (1.58 mmol/g), contributed significantly to the highly efficient hydrolysis of cellulose. Further, it was found that addition of trace water in [BMIM]Cl was favorable to cellulose hydrolysis. The highest yield (75.4%) of total reducing sugar (TRS) obtained in [BMIM]Cl-H2O at a mass ratio of 100:1 was more than twice that (36.1%) achieved in [BMIM]Cl without water; the corresponding reaction conditions were 50 mg of microcrystalline cellulose, 30 mg of catalyst, 1.0 g of [BMIM]Cl, 10 mg of H2O, reaction temperature of 130 °C and reaction time of 2 h. Furthermore, the TRS yield with 5 cycles for LAHC-SO3H was higher than 68.1%, and the catalytic activity of catalyst could be fully recovered (74.0% of TRS yield) easily by regeneration.

Three kinds of solid acid catalysts were prepared from alkali lignin in the waste liquor of pulping using carbonation- sulfonation method with different pretreatment. The lignin-derived solid acids (LDSAs) were characterized by FESEM, XRD, FTIR, TGA, BET and acid-base titration, respectively. A comparison study on the catalytic performance of LDSA prepared by different pretreatment method before carbonation in the hydrolysis of microcrystalline cellulose (MCC) was carried out. Results showed that the LDSA prepared by chemical activation with phosphoric acid (LPC-SO3H) exhibited superior catalytic activity due to its higher densities of -COOH group (1.68 mmol/g) as binding site and -SO3H group (0.88 mmol/g) as catalytic site as well as its larger specific surface area (488.4 m2/g) than those of the other two LDSAs. A total reducing sugar yield of 50.8% in MCC hydrolysis was obtained under the reaction conditions of temperature of 180 °C, time of 3 h, MCC concentration of 6 mg/mL and mass ratio of catalyst to MCC of 3.3 (w/w). Additionally, the value activation energy for hydrolysis of MCC to reducing sugars using LPC-SO3H was 83.31 kJ/mol, which was smaller than that using sulfuric acid.

Ordered mesoporous carbons (OMCs) were successfully prepared derived from Masson pine alkali lignin using evaporation-induced self-assembly and salt-induced self-assembly, respectively. The two OMCs show obvious differences in textural property including morphology, specific surface area and mesopore volume.

A solid acid catalyst was prepared from masson pine alkali lignin in waste liquor of soda pulping by a combined process of chemical activation, carbonization, and sulfonation. The lignin-derived solid acid (LDSA) was characterized by FESEM, XRD, FTIR, TGA, XPS, BET analyses, and acid-base back titration. The carbonaceous material had high thermal stability and large specific surface area (488.4 m 2 /g), and the structural analyses showed that it was composed of amorphous carbon bearing -SO 3 H, -COOH, and phenolic -OH groups. The lignin-derived catalyst was then applied to the hydrolysis of a microcrystalline cellulose (MCC) in aqueous system, and the yield of total reducing sugars was found to be 46.1%. It was proposed that good adsorption capacities of cellulose and desorption property of glucose on LDSA probably contributed to efficient catalytic hydrolysis.

The lignin-derived ordered mesoporous carbon solid acid (LDMC-SO3H) was prepared by evaporation induced self-assembly and sulfonation using Masson pine alkali lignin as carbon source. And LDMC-SO3H was used as catalyst in the hydrolysis of bagasse cellulose (BSC) with crystallinity index of 70.3% pretreated using deep eutectic solvent. A glucose yield of 42.5% was obtained under the optimized conditions of reaction temperature and time of 180 °C and 7 h, initial BSC concentration of 5 mg/mL and catalyst load of 3 mg/mg. In addition, glucose yield decreased to 31.0% after five runs of LDMC-SO3H due to the loss of -SO3H groups.

Carboxymethylated lignin (CML) is well suited as a dispersant or natural adsorbent applied in ceramics, gypsum paste, graphite suspension, and water treatment. In this paper, the effects of COOH content in CML on its behavior in water and the dispersion stability of aqueous graphite suspension has been investigated by means of viscosimetry, surface tension measurement, fluorescence spectrometry, dynamic light scattering (DLS), Turbiscan Lab Expert (TLE) stability analysis, and ζ potential measurement. Viscosimetry clearly revealed the polyelectrolyte effect in diluted aqueous solution of CML. With a higher COOH content of CML, the surface tension of water is reduced. Moreover, the aggregation behavior of CML was strengthened with increasing COOH content, leading to a more compact molecular structure of the aggregates. Based on the results, an aggregation model was proposed to illustrate the variations in the solution behavior of CML with different COOH contents at various concentrations. The dispersion stability of aqueous graphite suspension was improved by adding CML with high COOH content.

Carboxymethylated lignin (CML), a water-soluble lignin derivative with more carboxylic groups introduced by chemical modification, can be used as dispersant in industry. In this paper, using the methods of zeta potential measurement, X-ray photoelectron spectroscopy and UV spectroscopy, natural graphite (NG) and high-purity graphite (HPG) were selected to investigate the adsorption characteristics of CML at the hydrophobic solid/water interface. The adsorption isotherm of CML on HPG was more suitable for the Langmuir model than the Freundlich model, whereas the opposite result was obtained for the adsorption of CML on NG. Moreover, the amounts adsorbed of CML on HPG increased with higher ionic strength and lowering solution pH. However, the uptake of CML on NG increased dramatically with adding NaCl under acidic condition, while the ionic strength had no obvious influence on the adsorption under neutral condition. With increasing solution pH, the amounts of CML adsorbed on NG were dropped under acidic condition followed by increases under alkaline condition. It is suggested that the interactions between CML and the minor metallic impurities on NG surface probably contribute considerably to the differences between adsorption behaviors of CML on NG and HPG in varying solution conditions. Moreover, the results showed that the adsorption mechanism of CML at graphite/water interface could be described by Lennard-Jones potential.

Carboxymethylated lignin (CML) was prepared from wheat straw alkali lignin (WAL) via carboxymethylation modification. The characterizations using FTIR, 13C NMR, and 1H–13C HSQC NMR suggest that carboxyl groups are introduced into WAL structure successfully and there are two different active sites substituted by carboxymethyl groups. Moreover, the dispersion efficiency of CML was evaluated using the Turbiscan Lab analyzer. Effects of CML dosage and suspension pH on the dispersion stability of aqueous graphite suspension were investigated. The result shows that the dispersion stability of aqueous graphite suspension prepared with CML of 1.0% dosage at suspension pH 6.7 is obviously improved.

Carboxymethylated lignin (CML) as a water-soluble lignin derivative is a multipurpose adsorbent and dispersant. In this article, the aggregation and adsorption behaviors of CML have been investigated in aqueous solution using fluorescence spectroscopy, dynamic light scattering, and a quartz crystal microbalance combined with dissipation monitoring techniques. It was found that CML forms aggregates when its concentration exceeds the critical aggregation concentration (CAC). The CAC of CML1 with a carboxylic (COOH) group content of 2.8 mmol g-1 was 0.022 g l-1, and that of CML2 with a COOH group content of 2.0 mmol g-1 was 0.026 g l-1. The adsorption behavior of CML on the gold surface was strongly dependent on the pH and ionic strength of the solution. At low pH and ionic strength, more CMLs were adsorbed at the gold/water interface, and the layers were rigid. The results could be used not only from the theoretical but also from the application point of view.