School of Chemical Technology Degree Programme of Bioproduct technology

Fractionation of milled pine wood using γ-valerolactone (GVL)/ water solution as a novel organosolv treatment is proposed. Milled pine wood of 0.125 mm was cooked with GVL/water solution of different ratios. The reaction took place at 180 °C for 120 min in a monowave reactor. It was found that the highest delignification in pulp was achieved over the range of 50% to 60% wt. GVL/water. Under these conditions, the lignin content in the pulp was 12.7% and 14.4% O.D. wood basis, and the pulp yield was 60% and 65% respectively. Additionally, delignification increased when a different batch of samples at 50% and 60% wt. GVL were tested at 200 °C for 120 min. The residual lignin was the lowest at 60% wt. GVL with only 5.9% remaining. There was no significant change in delignification observed when the reaction time was increased to 150 min for the 50% and 60% wt. GVL samples at 180 °C. On the other hand, minor losses in cellulose content were detected at the first reaction conditions. The losses in the cellulose content slightly increased when temperature was raised to 200 °C. On the contrary, hemicelluloses content in pulp, xylan and glucomannan, were readily hydrolyzed. The hydrolysis of hemicelluloses was greatly affected by the increase in temperature, the final hemicelluloses content in pulp at 200 °C was 2.6% O.D. wood at 60% wt. GVL. For the aim of studying the trend behavior of delignification and polysaccharides hydrolysis, the fractionation reactions were carried out at 180 °C, 195°C and 210°C. As expected, delignification was maximum at 210 °C with only 45 min reaction time, while the least delignification was achieved at 180 °C and 180 min. The same trend is adopted by the hydrolysis of the polysaccharides, where intensive hydrolysis of hemicelluloses was noticed at 210 °C compared to 180 °C. On the contrary, cellulose losses were minor and residual cellulose values were not significantly affected by the increase in temperature. Finally, the rate constants (K) for delignification and polysaccharides hydrolysis were determined at the reaction temperatures of 180 °C, 195°C and 210°C. The K values showed faster delignification reactions at 210°C with 0.0378 1/min to 0.0225 at 195 °C, while the slowest delignification rate constant was 0.0038 1/min at 180 °C. The activation energy (E) for the delignification reactions was found to be 140.1 KJ/mol. As for polysaccharides, ’semi-crystalline’ cellulose hydrolysis was much slower compared to ’amorphous’ hemicelluloses hydrolysis at any given temperature, and xylan hydrolysis was faster than that of glucomannan.