KINETIC-ANALYSIS OF REVERSIBLE THERMAL-DECOMPOSITION OF SOLIDS

The isoconversional method was used to elucidate the kinetics of rever sible solid-state reactions occurring under nonisothermal linear heati ng. The characteristic dependencies of the effective activation energy (E) on the extent of conversion (W) were established for two model pr ocesses: a reversible first-order reaction and a reversible reaction f ollowed by an irreversible one. For the first process, E is almost ind ependent of W and varies between the activation energy of the direct a nd inverse reaction. For the second, process with an endothermic rever sible step, the dependence of E on W is of decreasing shape. The effec tive activation energy is limited by the sum of the activation energy of the irreversible reaction and the enthalpy of the reversible reacti on, at low conversions, and by the activation energy of the irreversib le reaction at high conversions. Analyses of the kinetic data for the dehydration of crystalhydrates, as well as other processes proceeding through a reversible step, show the dependencies of E on W characteris tic of a reversible reaction followed by an irreversible one. (C) 1995 John Wiley & Sons, Inc.