Jiachuan Chen

Cationic polyacrylamide enhancing cellulase treatment efficiency of hardwood kraft-based dissolving pulp

Cellulase treatment for decreasing viscosity and increasing Fock reactivity of dissolving pulp is a promising approach to reduce the use of toxic chemicals, such as hypochlorite in the dissolving pulp manufacturing process in the industry. Improving the cellulase treatment efficiency during the process is of practical interest. In the present study, the concept of using cationic polyacrylamide (CPAM) to enhance the cellulase treatment efficiency was demonstrated. This was mainly attributed to the increased cellulase adsorption onto cellulose fibers based on the patching/bridging mechanism. Results showed that the cellulase adsorption was increased by about 20% with the addition of 250 ppm of CPAM under the same conditions as those of the control. It was found that the viscosity decrease and Fock reactivity increase for the cellulase treatment was enhanced from using CPAM. The CPAM-assisted cellulase treatment concept may provide a practical alternative to the present hypochlorite-based technology for viscosity control in the industry.

Highly selective and efficient extraction of lignin in kraft pulp by aqueous ionic liquids for enhanced bleaching properties

Aqueous ionic liquids (ILs) that selectively extract lignin in kraft pulp under benign conditions were reported. This study provided an innovative idea to isolate the three-dimensional lignin from a recalcitrant matrix with the benefits of decreased dosage of bleaching chemicals, degradation of cellulose and toxicity of bleaching effluent.

Recycling cellulase towards industrial application of enzyme treatment on hardwood kraft-based dissolving pulp.

Cost-effectiveness is vital for enzymatic treatment of dissolving pulp towards industrial application. The strategy of cellulase recycling with fresh cellulase addition was demonstrated in this work to activate the dissolving pulp, i.e. decreasing viscosity and increasing Fock reactivity. Results showed that 48.8-35.1% of cellulase activity can be recovered from the filtered liquor in five recycle rounds, which can be reused for enzymatic treatment of dissolving pulp. As a result, the recycling cellulase with addition fresh cellulase of 1mg/g led to the pulp of viscosity 470mL/g and Fock reactivity 80%, which is comparable with cellulase charge of 2mg/g. Other pulp properties such as alpha-cellulose, alkaline solubility and molecular weight distribution were also determined. Additionally, a zero-release of recycling cellulase treatment was proposed to integrate into the dissolving pulp production process.

Thermogravimetric kinetics of sugarcane bagasse pretreated by hot-water.

The thermogravimetric of sugarcane bagasse pretreated by hot-water has been studied in this paper. Results indicated that residual solid pretreatment by hot water could decrease the activation energy of phase 2 (270-350 °C) obviously, which makes the pyrolysis more energy-saving. By hot water pretreatment, the hemicellulose, especially xylose (9.78%/o.d. dry mass at 170 °C and 1 h) was greatly extracted into hydrolyzates liquor. Greatly minimized hemicellulose waste at low temperature during pyrolysis also agreed with biorefinery concept. Therefore, bagasse with hot-water pretreatment should be a good pyrolysis material for value-added material.

Synergy of Lewis and Brønsted acids on catalytic hydrothermal decomposition of carbohydrates and corncob acid hydrolysis residues to 5-hydroxymethylfurfural

5-hydroxymethylfurfural (HMF) is an important platform molecule in the synthesis of various chemicals and materials. Herein, we reported a simple and effective dehydration of glucose-based carbohydrates to HMF in a biphasic system containing cyclopentyl methyl ether as the organic phase and AlCl3 with minute amounts of HCl as co-catalysts. The results showed that the mixed catalysts had a positive synergistic catalytic effect on glucose conversion to HMF compared with single AlCl3 or HCl catalyst. For glucose, the highest HMF yield of 54.5% was achieved at 175 °C for 20 min. More importantly, the optimal catalytic system was so efficient that it achieved one of the highest reported yields of HMF (30.5%) directly from corncob acid hydrolysis residues. Thus, the catalytic system can become a promising route for effective utilization of biomass in future biorefineries.

Extraction of Technical Lignins from Pulping Spent Liquors, Challenges and Opportunities

Different value-added products can be produced from lignin. To produce lignin based products, lignin derivatives need to be isolated from pulping spent liquors, as pulping spent liquors are dilute in lignin and impure. In this chapter, methods for isolating lignin derivatives from pulping spent liquors are reviewed. The main challenges and perspectives in the development of viable lignin production processes are described. LignoBoost and LignoForce were designed based on the acidification concept to isolate Kraft lignin from black liquor on the commercial scale, both of which produce pure lignin. To extract lignosulfonate from sulfite spent liquors, ultrafiltration seemed to be an industrially viable method, but the extracted lignin will likely contain impurities. Laboratory studies on adsorption and flocculation techniques for isolating lignin from other spent liquors with a low lignin content, e.g. prehydrolysis liquor of Kraft based processes, or the spent liquor of the neutral sulfite semichemical processes, are also discussed. Although these techniques seem to be industrially attractive, the purity of lignin that is produced in these processes are not high.

High consistency cellulase treatment of hardwood prehydrolysis kraft based dissolving pulp.

For enzymatic treatment of dissolving pulp, there is a need to improve the process to facilitate its commercialization. For this purpose, the high consistency cellulase treatment was conducted based on the hypothesis that a high cellulose concentration would favor the interactions of cellulase and cellulose, thus improves the cellulase efficiency while decreasing the water usage. The results showed that compared with a low consistency of 3%, the high consistency of 20% led to 24% increases of cellulase adsorption ratio. As a result, the viscosity decrease and Fock reactivity increase at consistency of 20% were enhanced from 510 mL/g and 70.3% to 471 mL/g and 77.6%, respectively, compared with low consistency of 3% at 24h. The results on other properties such as alpha cellulose, alkali solubility and molecular weight distribution also supported the conclusion that a high consistency of cellulase treatment was more effective than a low pulp consistency process.

Deep Eutectic Solvents (DESs) for the Isolation of Willow Lignin (Salix matsudana cv. Zhuliu)

Deep eutectic solvents (DESs) are a potentially high-value lignin extraction methodology. DESs prepared from choline chloride (ChCl) and three hydrogen-bond donors (HBD)—lactic acid (Lac), glycerol, and urea—were evaluated for isolation of willow (Salix matsudana cv. Zhuliu) lignin. DESs types, mole ratio of ChCl to HBD, extraction temperature, and time on the fractionated DES-lignin yield demonstrated that the optimal DES-lignin yield (91.8 wt % based on the initial lignin in willow) with high purity of 94.5% can be reached at a ChCl-to-Lac molar ratio of 1:10, extraction temperature of 120 °C, and time of 12 h. Fourier transform infrared spectroscopy (FT-IR) , 13C-NMR, and 31P-NMR showed that willow lignin extracted by ChCl-Lac was mainly composed of syringyl and guaiacyl units. Serendipitously, a majority of the glucan in willow was preserved after ChCl-Lac treatment.

Improvement membrane filterability in nanofiltration of prehydrolysis liquor of kraft dissolving pulp by laccase treatment

In this work, laccase treatment was employed to enhance nanofiltration process by lignin removal. Results showed that the membrane filterability was increased in terms of deionized water flux and PHL filtration process. On the other hand, the hemicellulosic sugars were negligible affected and can be concentrated to 172 g/L, which was increased about 300% from the original one. The combined laccase-nanofiltration process provides an alternative approach to utilize hemicellulosic sugars of PHL in an environmentally friendly way.

Modeling laccase-induced lignin removal in prehydrolysis liquor from kraft-based dissolving pulp production

Laccase treatment is a promising approach to remove lignin from prehydrolysis liquor (PHL) for value added utilization of hemicellulose rich waste streams. Modeling the lignin removal process is of practical interest for prediction and control of laccase treatment of PHL. The present study focused on the lignin removal through variation of laccase charge and treatment time. Results showed that the lignin removal may be divided into two phases, i.e. a fast initial phase followed by a second slow phase. A kinetic model based on the experimental results was developed, which can be used to predict the lignin removal of PHL during the laccase treatment.