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Ind. Eng. Chem. Res., 2013, 52 (36), pp 12777–12784.
Markus Paananen , Tiina Liitia , Herbert Sixta.
Aalto University, School of Chemical Technology, Department of Forest Products Technology, Vuorimiehentie 1, FI-00076 AALTO, Finland and
VTT Technical Research Centre of Finland, P.O. Box 1000, FI-02044 VTT, Finland.
Abstract
The polysaccharide degradation and dissolution behavior during high liquor-to-wood ratio (200:1) kraft cooking of Scots pine wood meal was studied at high (1.55 M) and moderate (0.50 M) hydroxide ion concentrations at a constant sulfidity of 33%. Both alkalinity levels were studied in and without the presence of anthraquinone (AQ) (0.05, 0.15, and 0.25 g AQ/L). High alkalinity experiments without AQ at 130–160 °C clearly confirmed significant galactoglucomannan stabilization (in respect to lignin content) throughout initial and bulk delignification phases. Additionally, at high alkali compared to moderate alkali concentration, lower amounts of low molecular weight carboxylic acids originating from the degradation of carbohydrates were detected in spent black liquor. The presence of AQ provided significant hemicellulose stabilization against endwise degradation reactions, being more pronounced at moderate 0.50 M concentration than at 1.55 M hydroxyl ion concentration. In all cases, higher alkalinity promoted carbohydrate removal via dissolution, and the addition of AQ reduced the degradation of the dissolved carbohydrate fraction, thus further increasing the amount of dissolved polysaccharides found in black liquor.
Copyright © 2013 American Chemical Society.
