Extraction of Hemicellulose from Loblolly Pine Woodchips and Subsequent Kraft Pulping

A mild borate assisted alkaline pretreatment was applied to Loblolly pine chips prior to kraft pulping to extract hemicelluloses. The extraction was performed at 90 °C for 4 h with 6% (w/w based on o.d. sample) alkali and 5% (w/w based on o.d. sample) boric acid. This process could recover 37.7% hemicellulose from the woodchips with only a 6.9% decrease in the cellulose degree of polymerization (DP). During the subsequent kraft pulping of the extracted woodchips, the process requires careful optimization to obtain the same yield (∼52%) and maintain high pulp quality as the control cook. For the kraft cooking of extracted chips, similar pulp yield and physical strength could be reached by either decreasing the cooking time (reduced H-factor by 30%) or decreasing the chemical charge by 25% in comparison with the control cook.