Lari Vähäsalo

Kinetics of Acid Hydrolysis of Water-Soluble Spruce O-Acetyl Galactoglucomannans

Water-soluble O-acetyl galactoglucomannan (GGM) is a softwood-derived polysaccharide, which can be extracted on an industrial scale from wood or mechanical pulping waters and now is available in kilogram scale for research and development of value-added products. To develop applications of GGM, information is needed on its stability in acidic conditions. The kinetics of acid hydrolysis of GGM was studied at temperatures up to 90 degrees C in the pH range of 1-3. Molar mass and molar mass distribution were determined using size exclusion chromatography with multiangle laser light scattering and refractive index detection. The molar mass of GGM decreased considerably with treatment time at temperatures above 70 degrees C and pH below 2. The molar mass distribution broadened with hydrolysis time. A first-order kinetic model was found to match the acid hydrolysis. The reaction rate constants at various pH values and temperatures were calculated on the basis of the first-order kinetic model. Furthermore, the activation energy, E, was obtained from the Arrhenius plot. The activation energy E was 150 kJ mol (-1) for acid hydrolysis of spruce GGM. The apparent rate constant during acid hydrolysis increased by a factor of 10 with a decrease in pH by 1 unit, regardless of temperature. In addition, gas chromatography and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry were applied to study the released GGM monomers and oligomers.

Phase Distribution of Resin and Fatty Acids in Colloidal Wood Pitch Emulsions at Different pH-Levels

The distribution of resin and fatty acids (RFAs) between the water phase and the lipophilic phase in colloidal pitch emulsions was determined as a function of pH. Model pitch emulsions were prepared and agitated at different pH, temperature, and NaCl concentration. After filtration, the concentration of dissolved RFAs in the water phase was determined. The experimental data were used for calculation of pKlw, that is, the pH at which 50% of the acids are dissolved in the water phase. At pH 3, all of the RFAs were associated with the colloidal droplets. The resin acids were dissolved at lower pH than the fatty acids. Among the resin acids, dehydroabietic acid had the lowest pKlw. The pKlw of fatty acids depended greatly on the chain length and degree of unsaturation. Fatty acids with more than 20 carbon atoms had a low water solubility even above pH 10. Increasing the NaCl concentration increased the pKlw. The kinetics of the phase distribution was very rapid.

Influence of Pitch Composition and Wood Substances on the Phase Distribution of Resin and Fatty Acids at Different pH Levels

Pitch emulsions were prepared to mimic the colloidal wood resin system in paper mill process waters. The phase distribution of resin and fatty acids (RFAs) between the colloidal lipophilic droplets (l) and the water phase (w) were determined as pKlw values. The effect of triglyceride to RFA ratio on pKlw values was studied, to determine if seasonal variations in wood extractives influence their phase distribution. The effect of water-soluble hemicelluloses on pKlw values was also determined. The pKlw values of the RFAs were lower in emulsions with a low triglyceride to RFA ratio. Addition of water-soluble galactoglucomannans also lowered the pKlw values of the RFAs.

De-esterification and sulfonation in spruce CTMP: Effects on pulp and paper properties

Abstract De-esterification and sulfonation reactions, which create new anionic groups in the middle lamella and primary wall layers, are the key chemical reactions in chemithermomechanical pulping. The effects of these reactions on the resulting fibre dimensions, refining energy demand, hand-sheet bulk and strength properties were assessed by laboratory-scale chemical pre-treatments and refining of Norway spruce chips. After pre-treatments with alkaline, sulfite, alkaline sulfite and alkaline peroxide liquors, a Wing defibrator-type batch refiner was used. The refining energy was measured. The degree of alkaline hydrolysis of acetyl and methyl ester groups in galactoglucomannans (GGMs) and pectins, and the degree of lignin sulfonation were determined. Hand-sheets were prepared and their physical properties were tested. The data were subjected to multivariate analysis and the order of significance of the chemical reactions towards pulp and paper properties was estimated. Chemical pre-treatments were found to increase the fibre length and the energy demand considerably. The fibre length and width after refining were strongly influenced by lignin sulfonation and pectin demethylation. GGM deacetylation had little influence on preserving the fibre dimensions in CTMP refining. The bulk, on the other hand, was highly influenced by GGM deacetylation. Peroxide reactions in alkaline peroxide treatments had no effect on the pulp and paper properties.

Effect of Calcium on the Phase Distribution of Resin and Fatty Acids in Pitch Emulsions

Resin and fatty acids (RFAs) play a key role in deinking processes of recycled fiber after precipitation by calcium. The distribution of RFAs between the lipophilic/colloidal phase and the water phase, here called pKlw, was determined by gas chromatography for different emulsions of TMP pitch and fatty acid soaps in the presence of calcium ions. Resin acids were at least partially dissolved at alkaline conditions even at high calcium ion concentrations, while fatty acids were only slightly soluble. The structure of the component was an important factor, along with the calcium content present which made fatty acids practically insoluble.