Co-Production of High-Grade Dissolving Pulp,Furfural,and Lignin from Eucalyptus via Extremely Low Acid Pretreatment and Pulping Technologies and Catalysis

Hemicellulose and lignin are not reasonably utilized during the dissolved pulp preparation process.This work aimed to propose a process for the co-production of dissolving pulp,furfural,and lignin from eucalyptus.High-grade dissolving pulp was prepared from eucalyptus using a combination of extremely low acid(ELA)pretreatment,Kraft cooking,and elementary chlorine-free(ECF)bleaching.The obtained pre-hydrolysate was catalytic conversion into furfural in a biphasic system,and lignin during Kraft cooking and ECF was recovered.The process condition was discussed as well as the mass flow direction.The results showed that ELA pretreatment could effectively remove 80.1%hemicellulose.Compared with traditional hydrothermal pretreatment,the ELA pretreatment significantly increased the xylose yield from 5.05 to 14.18 g/L at 170℃ for 2 h,which had practical significance for furfural production.The 82.7%furfural yield and 82.9%furfural selectivity were obtained from xylose-rich pre-hydrolysate using NaCl as a phase modifier in a biphasic system with 4-methyl-2-pentanone(MIBK)as an organic phase by ion exchange resin catalysts at 190℃ for 2 h.Subsequently,the pretreated eucalyptus was subjected to Kraft cooking,and the optimal alkali amount was 14%.Then,the Kraft pulp was bleached using the O-D1-EP-D_(2) sequence,and dissolving pulp was obtained with an ISO brightness of 86.0%,viscosity of 463 mL/g,andα-cellulose content of 95.4%.The Kraft lignin which has a potential application was investigated by 2D-HSQC NMR and 31P NMR.The results showed that the S/G ratio of Kraft lignin was 1.93,and the content of phenolic hydroxyl groups was 2.53 mmol/g.Moreover,based on the above proposed process,30.5 g dissolving pulp,5.5 g furfural,and 21.2 g lignin per 100 g eucalyptus chips(oven dry)were produced.This research will provide new catalysis and pulping technical routes for dissolving pulp,furfural,and Kraft lignin products,which are in great demand in the chemical industry.

Upgrading Paper-grade Softwood Kraft Pulp to Dissolving Pulp by Cold Caustic Extraction

Cold caustic extraction has potential applications in the production of dissolving-grade pulps due to its ability to selectively remove hemicellulose from lignocellulosic materials. In this study,we demonstrate the conversion of paper-grade kraft pulp into dissolving pulp by a single-stage cold caustic extraction. Under the extraction conditions of 12 wt% NaOH lye,11% pulp consistency,a temperature of 35℃,and 2 h,a paper-grade softwood kraft pulp was purified to high-grade dissolving pulp with 97. 1% α-cellulose content,1. 2% pentosane content,and narrowed molecular weight distribution. The resulting extraction filtrate was concentrated by nano-filtration to obtain the hemicellulose content of 59. 0 g / L,while the permeate was a clear Na OH solution with 10. 9 wt% concentration. A process configuration was also proposed,integrating this cold caustic extraction process with existing pulp and paper production and multi-purpose utilization of the extraction filtrate.

Process Control for Dissolving Pulp by SuperBatch Cooking

The process of producing dissolving pulp with SuperBatch cooking was introduced. The factors that affected the quality of the dissolving pulp and the corresponding operations were investigated.

Wet oxidation of activated carbon for enhanced adsorptive removal of lignin from the prehydrolysis liquor of kraft-based dissolving pulp production in an integrated forest biorefinery

Prehydrolysis is a key step for the production of kraft-based dissolving pulp.The pre-hydrolysis liquor mainly contains hemicellulosic components.Lignin can also be released into the pre-hydrolysis liquor,which hinders the purification and utilization of these hemicellulosic components.In this work,wet oxidation of activated carbon with nitric acid was employed to enhance the adsorptive removal of lignin from the pre-hydrolysis liquor.Under mild oxidation conditions(2%nitric acid solution),the oxidization of activated carbon resulted in significant enhancement of lignin removal.Adsorption isotherms showed that the specific surface area and the amount of carboxyl groups were affected by the oxidation treatment.The selective removal of lignin fitted well with the pseudo-second order kinetics model.

Enzymatic activation of dissolving pulp with cationic polyacrylamide to enhance cellulase adsorption

Cellulase treatment is a promising technology to improve the properties of dissolving pulp in an environmental friendly way.Increasing the cellulase treatment efficiency is of practical interest.In the present study,the concept of using cationic polyacrylamide(CPAM)to enhance the cellulase treatment efficiency was demonstrated.The hypothesis was that the CPAM would attribute to the increased cellulase adsorption onto cellulose fibers based on the patching/bridging mechanism.Results showed that the viscosity decrease was improved with the addition of 250 ppm of CPAM under the same conditions as those of the control.Degraded cellulose content was increased based on the alkaline solubility analysis,while alpha-cellulose content kept constant.The CPAM-assisted cellulase treatment concept may provide a practical alternative method for upgrading dissolving pulp.

Green and Effective Ammonium Carbonate-assisted Process for Drying Hemicellulose Obtained through Alkali Extraction of Bleached Bamboo Kraft Pulp

Hemicellulose has a wide range of applications,including that as an emulsifier for the food industry and raw material for the synthesis of bioethanol/biochemicals and biodegradable films.Hemicellulose is usually present as a spent liquor,such as the prehydrolysis liquor of the prehydrolysis kraft dissolving pulp production process and the alkali extraction liquor of the cold caustic extraction of pulp fibers.Due to its dilute nature,hemicellulose needs to be dried for practical utilization,and this is challenging.In this study,cellulose and hemicellulose in a bleached bamboo kraft pulp were separated using an alkali extraction process.Hemicellulose obtained from the extraction liquor was dried by an ammonium carbonate-assisted drying process.The effects of drying time and drying temperature were determined.Structure of the hemicellulose obtained by the ammonium carbonate-assisted drying process was similar to that of original hemicellulose,as revealed by detailed Fourier transform infrared and X-ray diffraction analyses.The novel drying method was more energy efficient and required a shorter drying time than the conventional freeze drying method,and the excellent solubility in alkaline solutions favored the chemical modification of hemicellulose.The dried hemicellulose can be used as a renewable raw material for the preparation of hydrogels and other substances such as bioethanol/biochemicals and biodegradable films.

Integration of hemicellulose recovery and cold caustic extraction in upgrading a paper-grade bleached kraft pulp to a dissolving grade

In this study,a hemicellulose recovery process was integrated with a cold caustic extraction(CCE)process in upgrading paper-grade bleached kraft pulp to dissolving grade.Under the conditions of 15%NaOH,10%pulp consistency,30℃and 1 h,a paper-grade softwood bleached kraft pulp was purified to a dissolving-grade pulp with 97.57%α-cellulose and 1.67%pentosan contents.The spent liquor from the cold caustic extraction process was sequentially extracted with ethanol to precipitate and recover the dissolved hemicelluloses,followed by evaporation to recover the ethanol.After the recovery of hemicelluloses and ethanol,the spent liquor can be reused as the caustic solution for the CCE process without compromising the resulting pulp properties.The results demonstrated that it is feasible to integrate hemicellulose production with the cold caustic extraction process of dissolving pulp production,based on the concept of biorefinery.

Beyond cotton and polyester: An evaluation of emerging feedstocks and conversion methods for the future of fashion industry

As the global population grows,the demand for textiles is increasing rapidly.However,this puts immense pressure on manufacturers to produce more fiber.While synthetic fibers can be pro-duced cheaply,they have a negative impact on the environment.On the other hand,fibers from wool,sisal,fique,wood pulp(viscose),and man-made cellulose fibers(MMCFs)from cotton can-not alone meet the growing fiber demand without major stresses on land,water,and existing markets using these materials.With a greater emphasis on transparency and circular economy practices,there is a need to consider natural non-wood alternative sources for MMCFs to supple-ment other fiber types.However,introducing new feedstocks with different compositions may require different biomass conversion methods.Therefore,based on existing work,this review ad-dresses the technical feasibility of various alternative feedstocks for conversion to textile-grade fibers.First,alternative feedstocks are introduced,and then conventional(dissolving pulp)and emerging(fibrillated cellulose and recycled material)conversion technologies are evaluated to help select the most suitable and promising processes for these emerging alternative sources of cellulose.It is important to note that for alternative feedstocks to be adopted on a meaningful scale,high biomass availability and proximity of conversion facilities are critical factors.In North America,soybean,wheat,rice,sorghum,and sugarcane residues are widely available and most suitable for conventional conversion through various dissolving pulp production methods(pre-hydrolysis kraft,acid sulfite,soda,SO2-ethanol-water,and potassium hydroxide)or by emerging cellulose fibrillation methods.While dissolving pulp conversion is well-established,fibrillated cel-lulose methods could be beneficial from cost,efficiency,and environmental perspectives.Thus,the authors strongly encourage more work in this growing research area.However,conducting thorough cost and sustainability assessments is important to determine the best feedstock and technology combinations.

A review on raw materials,commercial production and properties of lyocell fiber

As one of the regenerated cellulosic fibers,viscose fiber has the largest output.However,the wastes produced in the manufacturing process are difficult to eliminate,which restricts the de-velopment of viscose fiber.Lyocell fiber is claimed as“green and eco-friendly fiber”with a good application prospect in the 21st century.The preparation of lyocell fiber is based on the cellu-losic non-derivative solution system,i.e.,N-methylmorpholine-N-oxide system which is nontoxic and recyclable.In this review,firstly,the demands of dissolving pulp properties for regenerated-cellulosic fiber(RCF),especially for lyocell fiber,were introduced in detail.Next,the whole manu-facturing processes including pretreatment,preparation of spinning dope,spinning,posttreatment and efficient solvent recovery technologies were reviewed emphatically.Then,the properties and structural characteristics of lyocell fiber were illustrated.At last,some suggestions were proposed for lyocell fiber development in China.