QUANTITATIVE CORRELATIONS OF ACTIVATION PARAMETERS AND PROCEDURAL FACTORS - DEPENDENCE ON REACTION TYPE

The dependence of the correlation of kinetic parameters (energy of activation and pre-exponential factor) and procedural factors (sample mass and heating rate) on the type of reaction in non-isothermal thermogravimetry is established here for the first time. The effect of heating rate and sample mass on the stages of decomposition of diaquabis(ethylenediamine)copper(II) oxalate [GRAPHICS] has been studied non-isothermally. The kinetic parameters, calculated using both the mechanistic and non-mechanistic equations, show a systematic decrease with increase in either heating rate or sample mass for the dehydration and deamination reactions. For the decomposition reaction, the kinetic parameters are not appreciably affected by procedural factors. Mathematical correlations of high reliability are established between kinetic parameters and heating rate/sample mass using both the mechanistic and non-mechanistic equations for the dehydration and deamination reactions. Thus it has been found that the type of reaction is decisive in the correlation of kinetic parameters with procedural factors. The quantification follows a rectangular hyperbolic equation for the dehydration and a parabolic one for the deamination. No quantitative correlations were possible for the final decomposition of the oxalate to oxide. For all three reaction types, the rate-controlling process is random nucleation with the formation of one nucleus on each particle. It is observed that the mechanism of these reactions is not affected by the variations in sample mass and heating rate, or by the reaction type.