Jinghui Zhou

Structural changes of poplar wood lignin after supercritical pretreatment using carbon dioxide and ethanol–water as co-solvents

To delineate the structural changes of lignin during supercritical carbon dioxide pretreatment with ethanol–water as co-solvents (SCEP), enzymatic hydrolysis lignin (EHL) in original poplar chips, residual lignin in SCEP pretreated residues (SCEP-RL) and lignin dissolved in the SCEP liquors (SCEP-DL) were sequentially isolated and systematically characterized by GPC, quantitative 13C-NMR, 31P-NMR, 2D-HSQC NMR and TGA. After SCEP process, 19.2% of lignin was degraded and dissolved into SCEP liquors, while 4.8% of lignin was still present in the pretreated residues. It was also convinced that parts of the β-O-4 aryl ether linkages were cleaved and some of the stilbene, resinol (β–β) and phenylcoumaran (β-5) units were increased during SCEP process. Furthermore, the contents of free phenolic hydroxyl groups and carboxylic acids in SCEP-RL and SCEP-DL were higher than that of EHL.

High-strength lignin-based carbon fibers via a low-energy method

Bio-renewable carbon fibers are fabricated and employed as high-strength composite materials in many fields. In this work, a facile and low energy consumption method was developed to fabricate high-strength lignin-based carbon fibers. Using iodine treatment, the thermodynamic stability of the lignin-based precursor fibers increased significantly, and thus energy consumption during the preparation of the carbon fibers was reduced. The influence of the iodine treatment on fibers was analyzed by differential scanning calorimetry (DSC), scanning electron microscopy (SEM), Raman spectroscopy, tension testing, etc. The resulting iodine lignin-based carbon fibers had better tensile strength (89 MPa) than that of PAN carbon fibers produced by electrospinning technology.

Preparation, characterization and the adsorption characteristics of lignin/silica nanocomposites from cellulosic ethanol residue

The preparation, characterization, and adsorption characteristics of lignin/silica nanocomposites are described. The nanocomposites were obtained from cellulosic ethanol residue (CER) by an in situ method. The lignin was used as a structure directing reagent, and sulfuric acid as precipitating reagent during the synthesis of lignin/silica nanocomposites. The effects of pH on the properties of the nanocomposites have been investigated in detail. The prepared nanocomposites were characterized by the FT-IR, SEM, TG-TGA, XPS and low-temperature nitrogen sorption methods. Adsorption capacities and adsorption behaviors of selected lignin/silica nanocomposite, lignin, and silica for Methylene Blue (MB) were also studied, respectively. The results indicated that the lignin/silica nanocomposite is a good candidate for a biosorbent, providing a potential route for the high value-added utilization of CER.

Functional food packaging for reducing residual liquid food: Thermo-resistant edible super-hydrophobic coating from coffee and beeswax

Edible super-hydrophobic coatings have attracted great attentions as they can avoid the waste of liquid foods, such as honey and milk, adhered to the inside of containers. However, the poor thermal stabilities of edible super-hydrophobic coatings restrict their applications. In this work, a thermo-resistant edible super-hydrophobic coating has been fabricated using beeswax and coffee, which are approved by U.S. Food and Drug Administration. This coating surface has the similar micro/nanoscale structure to that of the leaf surface. A variety of liquid foods can freely roll on this coating surface in spherical. This special wetting property effectively reduces the residue of liquid foods, when they are poured out of the containers. With the introduction of coffee lignin, the thermal stability and adhesive force of the coating increases significantly. The apparent contact angle of this coating can remain to be above 150° after a long-time heating and flushing. This thermo-resistant edible super-hydrophobic coating can solve the problem that original edible super-hydrophobic coating is not resistant to high temperature, and has a broad application prospect in the field of functional food packaging.

Self-assembly of cationic amphiphilic cellulose-g-poly (p-dioxanone) copolymers

Cationic amphiphilic cellulose copolymers were prepared through grafting hydrophobic poly (p-dioxanone) (PPDO) chains onto hydrophilic quaternized cellulose derivatives (QC) via ring-opening polymerization (ROP) reaction, which was performed in 1-butyl-3-methylimidazolium chloride (BmimCl) and using 4-dimethylaminopyridine (DMAP) or 1,8-diazabicyclo (5.4.0) undec-7-ene (DBU) as catalyst. Their chemical structures and physical properties were confirmed by FT-IR, 1H-, 13C-, 2D HSQC-NMR, X-ray diffraction (XRD), and thermal stability (TGA) techniques, while self-assembly behavior was characterized by dynamic light scattering (DLS), transmission electron microscopy (TEM) and fluorescence techniques. Both of the sizes and critical micelle concentration (CMC) values of micelles were decreased with increasing grafting contents of PPDO in the copolymers, which were in the ranges of 110-246 nm and 64-253 μg/mL, respectively. The ζ-potentials of micelles were cationic andranged from 39.1 mV to 45.4 mV. The highest encapsulation efficiencyof paclitaxel (PTX) into the micelles was 61.8% and 92.0% of loaded PTX was continuously released from micelles in phosphate buffered saline medium for 36 h.

Lignin Structure and Solvent Effects on the Selective Removal of Condensed Units and Enrichment of S-Type Lignin

This study focused on the structural differences of lignin after pyridine–acetic acid–water (PAW) and dioxane–acidic water (DAW) purification processes. These structural differences included the S/G ratio, condensed structure, weight-average (MW) molecular weights, β-O-4 linkages and sugar content. The chemical structure of the isolated crude lignin (CL), PAW purified lignin (PPL) and DAW purified lignin (DPL) was elucidated using quantitative 13C NMR, 2D-HSQC NMR spectra, thermogravimetric analysis (TGA), gel permeation chromatography (GPC) and Fourier transform infrared spectroscopy (FTIR). The results showed that the PPL fractions contain fewer condensed structures, higher S/G ratios, more β-O-4 linkages, higher average MW and lower thermal degradation properties compared to the CL and DPL fractions. Furthermore, the PAW process was more selective in removing condensed units and enriching S-type lignin from CL compared to the DAW process. These results provide valuable information for understanding which purification process is more suitable to be applied for lignin.

Effect of xylanase, urea, Tween and Triton additives on bioethanol production of corn stover

Corn stover is a potential source of renewable biomass for conversion to bioethanol. Fed-batch semi-simultaneous saccharifcation and fermentation (S-SSF) of corn stover pretreated by liquid hot water (LHW) was investigated. The present study aimed to confirm the influence of xylanase, urea, Tween and Triton additives on bioethanol. Results show that the positive effect of xylanase, urea, Tween was observed. High ethanol concentration requires the addition of xylanase in the stage of saccharification. The optimal amount of xylanase was 0.2 g/g biomass and addition of Triton (Triton X-100) increases the effect of xylanase. Urea has a promotion effect on the whole fermentation process.When adding 0.1% urea in the fermentation stage,the best promoting rate is 24.2%. In the longitudinal comparison of the Tween series, under the same experimental conditions, the promoting effect of Tween series: Tween 40 > Tween 80 > Tween 20 > Tween 60.

The optimum delignification conditions and delignification course during the pretreatment process of poplar kraft pluping with green liquor pretreatment

In this paper, optimal pretreatment conditions were obtained by investigating the influences of temperature, time and green liquor doses on delignification during pretreatment stage in poplar green liquor pretreatment-Kraft pulping process with orthogonal experiments firstly. Then delignification course during pretreatment stage was obtained by conditional experiments after orthogonal experiments. Finally reaction course was analyzed by the changes of OH- and HS- in the pretreatment liquor. The results showed that the optimal conditions of delignification were as follows: maximum temperature, 120°C; green liquor dose, 1L/kg; holding time, 1h; liquor ratio, 1:4. The delignification process had three periods, which were the initial delignification stage, mass delignification stage and residual delignification stage. During the pretreatment the main function of NaOH was to open the channels for ion penetration, and provided suitable environment for the reaction between HS- and lignin. The main function of HS- was to react with lignin molecular and made it dissolvable after fragmentation.

Influence of poplar green liquor pretreatment on pentosan extraction

Green liquor pretreatment used in poplar Kraft pulping process and the influences of pretreatment conditions on pentosan extraction have been studied in this paper. The result showed that the influence of green liquor dosage (GLD) on pentosan extraction was the most remarkable, with the influence of temperature taking the second place and the influence of time the third. Under the conditions of liquor ratio 1:4, green liquor dosage 1.5L/kg (based on oven dried raw material), pretreatment 100°C, 90mins, higher pentosan extraction content was achieved, which was about 13.81%(based on the pentosan content of oven dried material). Under the best conditions of pentosan extraction, the wood after pretreatment was pulped under normal KP conditions. Comparing two kinds of pulp with and without pretreatment by green liquor at similar stock yield level, the results showed that the former had a little lower viscosity, significantly decreased Kappa number and excellent paper physical properties.