Delignification of wheat straw using a mixture of carboxylic acids and peroxoacids

Wheat straw was pulping by an Organosolv process using a mixture of acetic acid/formic acid/water (AA/FA/water). In order to make easier the bleaching step, it was possible to improve the delignification in an efficient and selective manner by using peroxoacids in acidic organic medium. First a solution of peroxoacids was synthesized by adding hydrogen peroxide in a mixture of acetic acid/formic acid. without any inorganic acids as catalyst. Then this mixture was added to the unbleached pulp. Several parameters (temperature, extraction alkaline, reaction time...) were investigated. This simple and innovative way to use peroxoacids allows to overcome problem due to the control of their stability, in aqueous medium and proves to be perfectly complementary to the cooking method in a carboxylic acid medium. Low kappa numbers and high viscosity were obtained. Strength properties of the pulp after the peroxoacids step were improved. (C) 2004 Elsevier B.V. All rights reserved.