ALKALINE PULPING OF PREHYDROLYSED WHEAT-STRAW IN AQUEOUS-ORGANIC SOLVENT SYSTEMS AT LOW-TEMPERATURES

The effects of partial hemicelluloses fractionation by prehydrolysis o n low-temperature organosolv pulping of wheat straw were examined. Pre hydrolysis took place at 100 degrees in 1.43 N H2SO4 for 10-40 min. Th e pretreated material ras delignified in NaOH-containing (5-25% w/w dr y solid basis) ethanol-water mixtures (35-100% v/v ethanol concentrati on). Optimal prehydrolysis, i.e. 30% hemicellulose removal, combined w ith pulping in 65% (v/v) EtOH were found to significantly, i.e. 8-25%, increase pulp mechanical properties. In addition, very high (95%) cel lulose retention in the pulp and high delignification values (86%) wer e achieved at 55% overall yield. The selectivity of lignin vs. carbohy drate removal during delignification was doubled by the application of a prehydrolytic stage prior to pulping.