Achieving Maximum Peroxide Bleaching Response Through Proper Selection of pHv, 1997 Pulping Conference Proceedings

Hydrogen peroxide bleaching performance can be significantly improved by using higher temperature pressurized peroxide bleaching systems. Higher temperatures also have the disadvantage of increasing the rate of peroxide decomposition, thus leading to lower brightnesses and lower pulp viscosities. The rates of both peroxide decomposition and peroxide bleaching of kraft pulp are strongly dependent on the pH of the bleaching liquor. The optimum balance at which decomposition reactions dominate over bleaching reactions at various temperatures will determine the potential success in any peroxide or pressurized peroxide bleaching process.

This work compares the rates of chromophore elimination and delignification to the rates of peroxide decomposition and viscosity loss. The pH at which a peroxide stage is run strongly influences the overall selectivity of the process at a given temperature. An empirical kinetic model for peroxide bleaching has shown that the activation energy for brightening is higher than for decomposition.