Abstract: Wheat straw was cooked at low temperature (85 ℃) by alkaline-oxygen method, and the pulp was then bleached by hydrogen perxoide under pressure and low temperature (80 ℃). We got the pulp with 86.6 %-89.5 % yield after bleaching, and the pulp brightness was significantly risen to 45.6 % from 60.6 %. The Kappa number of bleached pulp dropped from 17.9 to 9.4-11.9, and interestingly, the pulp viscosity slightly increased from 1 042 mL/g to 1 158-1 192 mL/g,which is different from the traditional bleaching. The brightness has certain linear relationship with Kappa number:brightness increment=Kappa number decrement×1.57;meanuhile there is a standard linear relationship between yield decrement and Kappa number decrement:yield decrement=Kappa number decrement×0.19.

Key words: wheat straw, alkaline-oxygen pulping, pressurized hydrogen peroxide bleaching