Search

Pulping kinetics of sugarcane straw (SCS) using the sulfur dioxide (SO2)-alcohol-water (SAW) system were investigated with different solvents (methanol, ethanol, and isopropanol) in order to evaluate the effect of the solvents. The methanol, ethanol, and isopropanol SAW pulps are identified as SMW, SEW, and SPW, respectively. The pulping experiments were carried out at 135°C, 145°C, and 155°C with cooking liquor (L/F = 4 L/kg feedstock) composition; SO2/alcohol/water of 12/44/44 w%. The pulps were characterized in terms of yield, kappa number, viscosity, cellulose, and hemicellulose and lignin content. After a fast initial dissolution phase, two regimes of delignification were identified in all solvent systems: a bulk and a residual phase. Bulk delignification and xylan removal followed first order kinetics in residual lignin and xylan, respectively, while the cellulose hydrolysis rate was zeroth order in cellulose. Linear relationships between Klason lignin content and kappa number were developed for each solvent system after correcting the acid insoluble lignin for ash and non-oxidizable matter. The corrected lignin content on original SCS was used to develop the bulk delignification kinetics. Rate constants and activation energies for bulk delignification, xylan removal, and cellulose hydrolysis were evaluated for each pulping system. In terms of degree of delignification, the pulping systems followed the sequence of: SMW 800 ml/g) were produced in SEW and SPW systems, while the lower rate of delignification and higher rate of cellulose hydrolysis in SMW yielded much lower viscosity pulps of higher kappa number at the same pulping temperature and time. The results are explained in terms of the effective acidity and lignin/carbohydrate dissolution properties of the pulping liquors. [ABSTRACT FROM AUTHOR]

The objective of this work was to determine the process conditions for converting sodium acetate, the major component of alkaline hardwood extract, into acetic acid and sodium hydroxide using bipolar membrane electrodialysis (BPMED). The effects of current density and sodium acetate concentration in the feed-salt solution were evaluated using synthetic sodium acetate solution in a feed and bleed mode. This mode of operation represents semibatch processing and was useful for determining the current efficiencies, energy consumption, and other system parameters for the production of about 160 g/L of acetic acid; maximum achievable concentration of acetic acid in electrodialysis; and 30 g/L of sodium hydroxide, which is the concentration sufficient for the extraction of sodium acetate from hardwood. The feed and bleed mode experiments performed at 60 mA/cm2 using 130 and 85 g/L sodium acetate as feed-salt solutions produced similar results, except for a small change in the amount of water transported into the acid and base compartments. The feed and bleed mode experiment performed at low current density of 40 mA/cm2 using 50 g/L sodium acetate as feed-salt solution produced almost similar quantities of acetic acid and sodium hydroxide as those in the other feed and bleed mode experiments. However, the energy consumption and current efficiencies were lower than those for the experiments performed at the current density of 60 mA/cm2. [ABSTRACT FROM AUTHOR]

Our objective was to develop a process for recovering acetyl groups from industrial northeast hardwood chips. Extraction experiments showed that the white liquor charge of 6% effective alkali at 50°C and liquor-to-wood ratio of 4:1 leads to the complete extraction of acetyl groups from industrial hardwood chips. Electrodialysis was assessed as a technique for separating and concentrating sodium acetate from synthetic hardwood extract. Preliminary separation experiments using dilute sodium acetate showed that the sodium acetate can be concentrated up to approximately 24% by weight from an initial concentration of about 2% by weight. The effects of current density, feed concentration, electro-osmosis, and osmosis on the separation of sodium acetate were evaluated. Finally, selectivity experiments were performed to study the effect of various components of the white liquor on the separation of sodium acetate. Fully oxidized synthetic white liquor was used in selectivity experiments to avoid deleterious effects of Na2S. Selectivity experiments using synthetic oxidized white liquor showed a significant decrease in the separation efficiency due to the presence of sodium hydroxide, sodium carbonate, and sodium sulfate in the synthetic extract. Application: Scientists and engineers engaged in the biorefinery concept can apply this information to development of a process to recover acetic acid or acetate salt as a byproduct at kraft mills, a possible new source of income for the paper industry. [ABSTRACT FROM AUTHOR]

A lignin-rich feedstock, soda-anthraquinone spent pulping liquor, was pyrolyzed in a kiln reactor. The liquor was prepared from mixed northern hardwood chips at a liquor-to-wood ratio of 3.5 L/kg, 16% effective alkali, and an H-factor of 1000 h. The spent liquor was pyrolyzed at 500°C as is, after oxygen oxidation, and with addition of sodium formate to determine the effect on bio-oil yield and product distribution. Contrary to bio-oil from sawdust, a clear phase separation of the liquid product into an aqueous layer and a denser organic layer is obtained. The predominant products found in the organic layer collected after pyrolysis are phenols with varying degrees of methylation and ethylation. The organic yield appears to go through a maximum (32 wt% on spent liquor organics) at around 25 wt% formate added on spent liquor dry solids and subsequently decreases at greater charges. Oxidation of the spent liquor prior to pyrolysis appears to have a detrimental effect on the organic yield. [ABSTRACT FROM AUTHOR]

This study was focused on the products from a larch biorefinery, specifically bleached paper and different fermentation products. Siberian larch (Larix sibirica Lebed.) wood chips were treated with water in a pre-extraction (PE) stage. The larch extract was removed by drainage and fermented into different products. Eight different bacteria strains were tested. The extracted wood chips were mildly washed before kraft pulping with polysulfide (PS) and anthraquinone (AQ). The PE-PSAQ pulps were bleached to about 80% brightness. Laboratory paper sheets were made and tested for different paper properties, and a conventional larch kraft pulp was also prepared as reference. The larch PE-PSAQ paper and the larch kraft paper had similar properties. The removal of a significant amount of hemicelluloses from the wood chips before pulping was not a detriment to the paper properties. [ABSTRACT FROM AUTHOR]

The kappa number, intrinsic viscosity, and yield of Southern Pine pulps were determined after oxygen delignification at different alkali concentrations, temperatures, oxygen pressures, and treatment time in a Berty throughflow reactor. It was found that the highest delignification-cellulose degradation selectivity is achieved at low alkali concentrations and temperatures of about 100°C or less. Oxygen pressure has little effect on selectivity. Carbohydrate yield loss is proportional to kappa number loss up to kappa reduction of 60%. At higher delignification, the carbohydrate yield loss increases more strongly than delignification. However, carbohydrate yield loss is linearly correlated with cellulose degradation at all degrees of delignification. Hexenuronic acids are not removed during conventional oxygen delignification. To increase delignification of softwood pulp beyond about 60%, oxygen system design should be changed so that alkali concentration and charge are decoupled, as is similarly done in modern cooking systems. [ABSTRACT FROM AUTHOR]