Preparation of high grade dissolving pulp from radiata pine
Abstract High grade dissolving pulp was prepared from radiata pine by the pre hydrolysis Kraft process. The effect of the P factor in the pre hydrolysis stage on the properties of wood chips was investigated. With an increasing P factor, hemicellulose was selectively removed from wood chips, and the crystallized index of the pre hydrolyzed wood chips increased owing to the dissolution of the amorphous phase in the substrates. Further, sugars in hemicellulose could be rapidly hydrolyzed; whereas, their release became slower with a further increase in the P factor. Comparatively, arabinose and galactose were readily removed during pre hydrolysis for its accessibility. Additionally, accumulations of furfural and 5 hydroxymethylfurfural (HMF) were detected via acid catalyzed dehydration of pentose and hexose, respectively. HMF can be further converted into formic and levulinic acid by acid catalyzed dehydration. After pre hydrolysis, the chips were subjected to Kraft cooking, and the optimal P factor (480) for the production of dissolving pulp and the optimal H factor (1500) in terms of the Kappa number, viscosity, and a cellulose of the pulp were obtained. Then, the Kraft pulp was bleached using the (OO)D0EOPD1D2 sequence, and a final ISO brightness of 91.0% was achieved with negligible loss in a cellulose. The described technique and parameters are important for the industrial production of high grade dissolving pulp using radiata pine.