Kinetics of thermal dehydration and decomposition of Fe(III) chloride hydrate (FeCl3·xH2O)

Article abstract of DOI:10.1007/BF01979283

Fe(III) chloride hydrate (FeCl₃·xH₂O) undergoes simultaneous dehydration and dehydrochlorination from its molten phase in the temperature range 100-200°C. The kinetics of these two parallel thermal processes has been studied by both isothermal and non-isothermal methods. Whereas for the dehydration reaction at temperature below 125°C a second order rate model (F₂) fits well, a three-dimensional diffusion (D₃) model is found to fit better at temperature above 135°C. For the dehydrochlorination reaction an interface growth controlled model of 1/3 order (F 1/3) appears to be the most suitable over a wide range of reaction. Dynamic thermogravimetry reveals two major steps in the temperature range 50-250°C. The first step which corresponds to the loss of about 4 mols of H₂O, invariably follows second order kinetics (F₂). The second step which is predominantly a process of dehydrochlorination, generally fits mixed diffusion controlled models due to the overlapping with the dehydration process. There is an excellent agreement in results among the isothermal and non-isothermal methods of determining kinetic parameters.