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High solvent recovery and monomeric sugar yield are essential for a viable biochemical conversion technology. The SO2-ethanol-water (SEW) or AVAP® process has great potential to produce easily fermentable pulp fibers and sugars dissolved in the spent liquor stream. The SEW fractionation process is evaluated for delignification, xylan removal and potential reactions between ethanol and sugarcane straw (SCS) carbohydrates. α-ethyl-xyloside (aEX) and β-ethyl-xyloside (bEX) formed by reaction of ethanol with xylose are quantified. The fractionation experiments are carried out at 135°C, 145°C, and 155°C for 20-120 min at fixed liquor composition (SO2/EtOH/H2O = 12:44:44, w/w) and liquor to feedstock ratio (4 l kg-1). The results are interpreted in terms of combined severity factor (CSF). Maximum ethyl xylosides (EX, or sum of aEX and bEX) and monomeric xylose concentrations are observed at CSF of 2.4 ± 0.1. The maximum amount of EX in spent liquor accounts for nearly 1.4% of EtOH (feedstock basis). The implications for downstream recovery of EtOH and sugars from the spent liquor are discussed. [ABSTRACT FROM AUTHOR]

In the present study the advantages of multistage oxygen delignification was explored in comparison with a single-stage process at the same level of total caustic charge. A pine kraft pulp with kappa number of 65 (Kn65) was bleached with the focus on the effect of NaOH-charge distribution on Kn, pulp yield, and selectivity of oxygen delignification. The effect of initial chelation with ethylenediaminetetraacetic acid (EDTA) and interstage pulp treatment with peroxymonosulfuric acid (Px) were also investigated. It is shown that the chelated pulp with high Kn may be delignified in three stages to Kn15, but at an unacceptable reduction in pulp viscosity and yield. In contrast, interstage treatment of the chelated pulp with Px at a total charge of 2% active oxygen (based on pulp) in combination with three stages of oxygen delignification enables Kn reduction to about 15 at acceptable viscosity and total yield advantage of about 0.5% (based on wood) compared to an oxygen-delignified kraft pulp with Kn24 derived from the same pine wood chips. [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]