Abstract: Delignification and bleaching of lignocellulosic material is obtained with catalyzed hydrogen peroxide in alkaline medium.

Abstract: The bleaching of fluff cellulosic pulp with a gaseous ozone bleaching agent at an acidic pH is often followed by an alkaline treatment, usually an alkaline extraction or an alkaline hydrogen peroxide bleaching treatment, at a much higher water content than the gaseous ozone treatment of the fluff pulp. Such a bleaching sequence of gaseous ozone bleaching followed by an alkaline treatment is improved by the present invention based upon two discoveries, first, the discovery of peroxygen bleaching values in the water associated with the fluff pulp leaving the ozone bleaching treatment, and second, the peroxygen values are destroyed at the alkaline pH used for the alkaline treatment that follows the gaseous ozone bleaching treatment. In accordance with the discoveries, a Low Consistency Acidic Retention Treatment is interposed between the gaseous ozone bleaching treatment and the alkaline treatment.

Abstract: A Kraft pulp bleaching process comprising from one to about three treatments with ozone and a final treatment with an alkaline peroxide solution, the treatments being separated by an alkaline extraction, wherein effluent from the bleach treatments is utilized in subsequent bleaching operations or in the chemical recovery system of a Kraft pulping process.