Production of pure cellulose from Kraft pulp by a totally chlorine-free process using catalyzed hydrogen peroxide

A mixed hardwood Kraft pulp was used after oxygen delignification to produce pure cellulose for dissolving purposes. A totally chlorine-free bleaching and purification process was designed. It comprises an acid hydrolysis step in the presence of a metal chelating agent (EDTA) followed by a peroxide delignification stage under oxygen pressure catalyzed by a Cu(II)phenanthroline complex, a cold caustic extraction and finally, an ozone stage carried out under neutral conditions. High purity cellulose with less than 5% xylans could be produced. Both the catalyst and the ozone stage have an effect on the DP of the cellulose which then can be varied depending on the requirements. (C) 2013 Elsevier B.V. All rights reserved.