Kaolinite Dehydroxylation Kinetics

The rates of dehydroxylation of three kaolinites which varied in particle thickness were studied from 417° to 480°C under very low water vapor partial pressures. The dehydroxylation rate was directly proportional to the surface area and had an activation enthalpy of 41.0 kcal/mol. The data did not fit either a diffusion-controlled or a phase-boundary-controlled reaction in the radial direction, even when the particle diameter distribution was taken into account. The reaction appears to proceed through the kaolin particles by a pseudo-phase-boundary-controlled mechanism, principally in the 001] direction.