CELLULOSE DELIGNIFICATION AND BLEACHING METHOD Russian patent published in 2014 - IPC D21C9/00 

FIELD: chemistry.

SUBSTANCE: method for cellulose delignification and bleaching with chlorine dioxide and hydrogen peroxide in the presence of molybdate or tungstate as a catalyst. The bleaching step includes: a) a first step where cellulose (3-30 wt %) in an aqueous mixture at temperature in the range of 50 to 150°C and pH in the range of 2 to 7 reacts with chlorine dioxide in an amount which corresponds to a Kappa coefficient in the range of 0.02 to 0.25 until more than 90% chlorine dioxide is converted; b) a second step where the mixture obtained at the first step, without separating components thereof, reacts at temperature in the range of 50 to 150°C with hydrogen peroxide which is taken in amount of 0.1 to 5 wt %, in the presence of molybdate in an amount which corresponds to molybdenum content of 10 to 2000 ppm, or in the presence of tungstate in an amount which corresponds to tungsten content of 200 to 10000 ppm. All amounts in each case are given with respect to the mass of the dry cellulose used.

EFFECT: improved whiteness of cellulose, low consumption of chlorine dioxide without undesirable destruction of cellulose, high resistance of cellulose to yellowing.

10 cl, 10 tbl