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The objective of this work was to determine the effect of sodium methyl mercaptide (SMM) as an additive on the minimization of carbohydrate peeling reactions in Rock/Hard Maple (Acer saccharum) chips during kraft pulping. Two methods were evaluated for SMM addition to the pulping process: 1) pre-treatment before pulping and 2) co-addition with white liquor. The experimental results showed about 2.5% (on wood basis) increase in the kraft pulp yield after pre-treatment with 4.38% SMM (on wood basis) or the co-addition of the same amount of SMM with white liquor. The use of 4.38% SMM allowed a decrease in the white liquor effective alkali charge of 3% (on wood basis) to produce the target 14–15 kappa pulp. The 4.38% SMM charge was determined to be the optimum for both pre-treatment and co-addition. The increase in kraft pulp yield was mostly due to increased retention of cellulose (about 0.8% on wood) and xylan (about 1.8% on wood). The retention of glucomannan was insignificant in all cases. Based on the increase in intrinsic viscosity, it is concluded that the increased cellulose yield with SMM addition is caused by both reduced primary peeling and faster delignification rate (less alkaline hydrolysis followed by secondary peeling). The increased xylan retention is due to the lower effective alkali concentration during kraft pulping with SMM addition. [ABSTRACT FROM AUTHOR]

A simplified method for sequentially dissolving and fractionating ball milled hard wood polymers in high yield is presented. The complete dissolution of the whole ball milled wood, and the fractions recovered from it by applying the sequential fractionation, was accomplished in lithium chloride/dimethylacetamide solvent system enabling size exclusion chromatography studies. The chromatography applied a four detector system; an Ultraviolet-Visible spectroscopy-, Intrinsic Viscosity-Differential Pressure-, Right Angle Laser Light Scattering- and Refractive Index detectors, a combination hereby proposed to enable interpretation of the complex elution profiles with emphasis on chemical interactions. Indirect evidence of the presence of lignin carbohydrate complexes in hardwoods is provided. It is also proposed that cellulose is severely degraded from a degree of polymerization of 10,000 in wood, down to a value of approximately 400 by either the applied ball milling condition or in subsequent solubilization steps. [ABSTRACT FROM AUTHOR]

Highlights: [•] Softwood and hardwood biomass is fractionated by SO2–ethanol–water technology. [•] Hemicellulose dissolution rate is similar for softwood and hardwood. [•] Biomass (branches etc.) fractionation is compared with stem wood fractionation. [•] Softwood biomass delignification is inferior likely due to high amount of bark. [ABSTRACT FROM AUTHOR]

The overall target of this project, called Bioforest, is to develop an economic process for the production of commodity chemicals from mixed forest biomass, consisting of logging residues of hardwoods (HW) and softwoods (SW) and also from recycled fibers. The aim is to dissolve the biomass lignin and to produce monosugars based on hemicelluloses and hydrolyzed cellulose in high yield. The hydrolyzate could subsequently be converted into chemicals by modified acetone-butanol-ethanol fermentation. Here, the total mass balances of SO2-ethanol-water fractionation of different types of biomass feedstocks, such as SW and HW biomass, and deinked pulp are presented. Chemical composition of the feedstocks, solid residues (pulps) and spent liquors of fractionation were analyzed to gain more understanding about the fractionation procedure. The analysis was focused on carbohydrates, lignin, ash, acetyl groups and sugar degradation products. It was also examined if all feedstocks could be treated simultaneously in one digester because a larger feedstock supply within an economic transport radius improves the viability of the process. The fractionation approach was successful and it can be concluded that the method presented is very versatile for future applications in lignocellulosic biorefineries. [ABSTRACT FROM AUTHOR]

Extraction of hemicelluloses from wood prior to pulping is being pursued to generate more value-added products, while still producing high quality pulp from the pre-extracted wood. For a better understanding of the factors limiting selective extraction, enzymatic hydrolysis in combination with size exclusion chromatography (SEC) was applied to milled wood and hydrothermally treated wood. Complete dissolution was achieved in a lithium chloride/dimethylacetamide solvent system after mild ballmilling of a Southern Hardwood Mixture (SHM), of SHM extracted using auto-hydrolysis, and of enzyme-treated SHM. SEC tests showed that severe degradation of wood polymers occurred after a milling time of 3 hours. The SEC data also confirmed the presence of lignin-carbohydrate complexes. Based on the results, it is suggested that linkages between lignin and polysaccharides may play an important role in limiting extraction of hemicelluloses. [ABSTRACT FROM AUTHOR]

The enzymatic hydrolysis of hardwood and softwood harvest residues treated by SO2-ethanol-water (SEW) fractionation was studied. The target was to convert these fibers with high yield into glucose monomers which could be further converted into biofuel by a subsequent fermentation stage. Hardwood biomass residues were efficiently digested at low enzyme dosage (5 FPU/g cellulose) whereas the softwood residues required notably higher enzyme dosage (20 FPU) for sufficient conversion. However, cellulase dosage of softwood could be reduced mannanase supplementation. Especially the high lignin content of softwood biomass pulps impairs the digestibility and thereby, improved delignification could notably enhance the hydrolysis yields. It was shown that inferior delignification of SW biomass is due to persistent polyphenolic acids present in coniferous bark, whereas no evidence of the negative effect of inorganics and acetone extractives was observed. Additionally, SW hydrolyzate was successfully converted into a mixture of butanol, acetone and ethanol through ABE fermentation. [ABSTRACT FROM AUTHOR]

A mixture of US southern hardwood chips was treated with aqueous acetic and formic acid (FA) solutions in a modified Dionex ASE100 extractor. The amount and selectivity of hemicelluloses dissolution increase at higher acetic acid (AA) and FA concentrations, but cellulose remains intact in the residual wood. Even at the highest AA concentration of 100 g l-¹, the dissolved hemicellulose fragments are still oligomeric except for arabinose. The formation of lignin-like condensation products (LCPs) and decomposition of dissolved mannose, arabinose, and galactose were observed at the highest AA concentration. Sugar hydrolysis is more pronounced with the addition of FA at increasing temperature. The concentration of xylose in the FA extract is approximately the same as that of xylooligomers at 160°C. Formation of LCPs is only observed at 170°C during 10 g l-¹ FA treatment. The concentrations of dissolved wood components increase linearly with increased recycling of the FA extract. [ABSTRACT FROM AUTHOR]

Inthe current study, a simple two-step fractionation process was developedfor utilization of hardwood biomass without forming troublesome stickylignin condensation products. The four product streams generated area hemicellulose extract, a lignin extract, separated wood fibers (pulp)and wood fiber bundles (rejects). All four product streams can befurther utilized for production of transportation fuel, chemicals,and biomaterials. The optimum fractionation conditions for mixed southernhardwood chips are the following: extraction with 10 g/L formic acid(FA) at 160 °C for 90 min followed by extraction with 50% (w/w)EtOH at 80 °C for 90 min. The yield of pulp and reject fibersthat are produced from the FA and EtOH pre-extracted wood chips bymechanical action are 38% and 28%, respectively. Cellulose to glucoseconversion yield of the FA treated wood, as well as that of the finalpulp and fiber bundles by enzymes, are strongly improved comparedto that of the original hardwood chips. [ABSTRACT FROM AUTHOR]

A pre-hydrolysis step to remove hemicelluloses from mixed hardwood chips consisting of maple, aspen, and birch with a ratio of 7:2:1 has been carried out. The effects of parameters on the pre-hydrolysis such as time, temperature, acetic acid addition, and raw material species, were determined. Different sugars, acetic acid, and furfural formation in the pre-hydrolysis liquor were quantified. The results showed that the pre-hydrolysis is a dynamic process, in which the removal of hemicelluloses increased with time while the conversion of extracted hemicelluloses to monosaccharides due to acid hydrolysis increased and part of the xylose was converted to furfural. The maximum temperature was the most critical parameter for hemicelluloses extraction and conversion, and a temperature of 170°C was the optimum for hemicelluloses extraction with relatively low conversion of xylose to furfural. About 11% of the xylan (in both monomeric and oligomeric forms) was removed at 170°C. Due to the presence of a high amount of xylan, birch produced the highest amount of xylose, followed by maple, and then aspen. [ABSTRACT FROM AUTHOR]

Hardwood hemicellulose extracts can be used as a feed stock for ethanol plants or for renewable polymer applications. Extraction of Acer rubrum wood strands with water at 160°C and for 90 minutes removed approximately 16% of the wood weight. The extract was composed primarily of acetylated glucuronoxylans (63.9%) and lignin (17.6%). The dispersive surface energy and acid-base surface characteristics for a multi-component freeze dried mixture of hot water extracted Acer rubrum components was determined by inverse gas chromatography (IGC). The dispersive surface energy of the extract was found to be non-sensitive to thermal variations and has a magnitude of 34.6 ± 0.2 mJ/m2 with a Ka of 0.13 and Kb of 0.46. The maple wood had a regressed surface energy of 42.7 mJ/m2 at 20°C following extraction, and the surface energy before extraction was 40.4 mJ/m2 at 20°C. Also, before extraction the Ka and Kb of the red maple were 0.19, 0.92, respectively, and after extraction the Ka and Kb were 0.15 and 1.17. Infrared spectroscopy (IR) was used to characterize the wood surfaces and the IR data correlated to the surface energy values. These findings indicate that the hemicellulose-extract components influence the overall average surface energy of maple wood by lowering the surface energy relative to other surface components. [ABSTRACT FROM AUTHOR]