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SO2-ethanol-water (SEW) delignification kinetics for spruce, beech, and wheat straw are presented. All these species produce pulps using SEW cooking liquor and follow first order delignification kinetics at similar bulk delignification rates. However, residual delignification is much slower for beech than for spruce. The hemicelluloses retention (135°C) and cellulose degradation kinetics are also characterized for beech SEW pulping. Xylan and glucomannan are removed from the pulp following first-order kinetics with a higher rate constant for xylan. Cellulose is retained in the fibers until kappa number 9, after which it starts to dissolve in the liquor. The yield also drops significantly in the region of kappa numbers 9-7. Cellulose degradation is followed by intrinsic viscosity measurements and is found to be zero order in cellulose. The rates are higher at 135 and 145°C for beech SEW pulping than for spruce. [ABSTRACT FROM AUTHOR]

The objective of this study is to develop a process for conditioning spent liquor produced by SO2-ethanol-water (SEW) fractionation of spruce wood chips for fermentation to butanol, ethanol and acetone/isopropanol, i.e., by means of the so called acetone-butanol-ethanol (ABE) process using Clostridia bacteria. This study serves as part of an overall project aiming at the development of economic processes for producing chemicals and biofuels from mixed forest biomass via SEW fractionation and ABE fermentation technologies. [ABSTRACT FROM AUTHOR]

SO2-ethanol-water (SEW) pulping is a promising fractionation process for lignocellulosics to produce pulp and value-added chemicals as a contribution to the concept of forest biorefinery. The presence of SO2 leads to dissolution of hemicelluloses in high yield mostly as monomeric sugars, while lignin becomes soluble through sulfonation. After lignin removal, the dissolved sugars may be used as feedstock for fermentation to ethanol or butanol. SEW pulping may be considered a hybrid between solvent pulping (organosolv pulping by solvolysis) and acid sulfite pulping. Absence of an inorganic base leads to simplification of the recovery cycle. Furthermore, alcohol increases the impregnation rate of dissolved SO2 into wood, so that a separate impregnation phase is not necessary. Also, the presence of SO2 allows cooking of softwoods, while ethanol pulping is limited to hardwoods. Thus, SEW pulping may be applied to a wide variety of lignocellulosics at lower temperatures and similar cooking times than those used in kraft pulping. In the present study, SEW pulping experiments were performed on spruce chips at cooking temperatures of 135–165°C with a 12% SO2 solution at a liquor-to-wood ratio of 6:1 l kg-1. The effect of cooking temperature and time on kappa number, yield, and intrinsic viscosity of the pulp was determined. Based on these results, the kinetics of delignification, hemicelluloses removal, and cellulose hydrolytic destruction were established. [ABSTRACT FROM AUTHOR]

The focus of this study is to develop a process for conditioning spent liquor produced by SO2–ethanol–water (SEW) fractionation of spruce chips/softwood biomass for fermentation to butanol, ethanol, and acetone/2-propanol (so-called ABE process) by Clostridia bacteria. This study is an integral part of a project which aims at creating an economic process that can utilize cheap forestry residues such as twigs, cones, treetops, branches, and bark to produce renewable chemicals and liquid fuels. The results of this study suggest that the proposed scheme for conditioning of SEW spent liquor from spruce/softwood biomass can be successfully applied to produce chemicals and biofuels by ABE fermentation. Butanol, acetone, and ethanol are produced at a total yield of around 0.25 g/g sugars. [ABSTRACT FROM AUTHOR]

Abstract: SO2–ethanol–water (SEW) spent liquor from spruce chips was successfully used for batch and continuous production of acetone, butanol and ethanol (ABE). Initially, batch experiments were performed using spent liquor to check the suitability for production of ABE. Maximum concentration of total ABE was found to be 8.79g/l using 4-fold diluted SEW liquor supplemented with 35g/l of glucose. The effect of dilution rate on solvent production, productivity and yield was studied in column reactor consisting of immobilized Clostridium acetobutylicum DSM 792 on wood pulp. Total solvent concentration of 12g/l was obtained at a dilution rate of 0.21h−1. The maximum solvent productivity (4.86g/lh) with yield of 0.27g/g was obtained at dilution rate of 0.64h−1. Further, to increase the solvent yield, the unutilized sugars were subjected to batch fermentation. [Copyright &y& Elsevier]