The prehydrolysis treatment of wood chips is generally adopted for the manufacture of dissolving sulfate pulp, because this treatment selectively removes pentosan from wood. Instead of water if xylenesulfonate is used in the prehydrolysis, a considerable amount of lignin will be removed with pentosan, and consequently shortening the time of sulfate cooking after prehydrolysis and the improvement of yield and qualities of pulp may be expected.
Beech wood meal and beech wood chips were treated with an aqueous solution of xylenesulfonate to find a suitable condition of prehydrolysis, varying concentration of reagent, pH, cooking temperature and cooking time (Tables 15). As a comparison the prehydrolysis treatments with water were also carried out. From the results of treatments, the following conditions seem to give a good effect : concentration of xylenesulfonate, 25% in weight ; pH of xylenesulfonate solution, 6.1 ; maximum cooking temperature, 160°C ; cooking time at maximum temperature, 2 hours ; in this case the yield of prehydrolyzed chips was 71.8%, contents of lignin and pentosan in chip were 19.9% and 12.5%, respectively.