Hydrogen peroxide delignification of kraft pulp catalyzed by heteropoly anions

The delignification of kraft pulp with acidic hydrogen peroxide catalyzed by four heteropoly acid-H-4 [PMo11 VO40], H-5 [PMo10 V2O40], H-7 [P2Mo17 VO62] and H-8 [P2Mo16 V2O62] was investigated, and the effects of temperature on hydrogen peroxide delignification catalyzed by H, [ PMo,(, VO,,,, I were studied. The results indicated that the four heteropoly acids all have catalytic activity for the delignification of kraft pulp, but they also accelerate carbohydrate degradation. The kappa number reduction and viscosity reduction of pulp decreased as the electric charge number of heteropoly acids increased. It seems that the temperature response of hydrogen peroxide delignification catalyzed by H-5 [PMo10 V2O40] was "abnormal", the kappa number reduction was maximum at about 60degreesC. The viscosity reduction of pulp was nearly linear with reaction temperature increasing. It is optimal to choose 60degreesC for the hydrogen peroxide delignification catalyzed by H-5 [PMo10 V2O40].