The authors present some theoretical considerations concerning the influence of the form of the conversion functionf(α) on the values of the degree of conversion corresponding to the maximum value of the reaction rate (αmax) as well as on the inflexion points (αinf) of the DTG curve. The obtained equations are characterized by a general validity no matter the form off(α).
The results of an attempt to derive correct nonisothermal kinetic equations from isothermal ones through the classical nonisothermal change (CNC) of the postulated primary kinetic equations are presented. An alternative possibility through use of the model of infinitesimal isothermal portions (MIIP) is discussed.
The paper deals with the influence of the deviation of the true heating rate with respect to the programmed one on the values
of non-isothermal kinetic parameters for the solid-gas thermal decompositions of CaC2O4.H2O and [Ni(NH3)6]Br2. An original method, based on integration over small ranges of the variables and making use of local heating rates, was applied
in order to determine the non-isothermal kinetic parameter values. The results show significant differences between values
of non-isothermal kinetic parameters obtained by using true local heating rates and those obtained by using the programmed
The authors continue their considerations concerning the validity of the steady-state approximation in non-isothermal kinetics.
A sequence of two first-order consecutive reactions with an active intermediate was subjected to kinetic analysis by numerical
solution of the corresponding differential kinetic equations for a number of particular cases. The results demonstrated that
the rate of change of concentration of the active intermediate is negligibly small if the assumption made in the isothermal
case is also accepted for the non-isothermal case, i.e. k2(T(t))>>
and the steady-state approximation are used to present a demonstration of the fact that the evolution of the reaction rates
under non-isothermal conditions depends on the ratio of the activation energies and on the heating rate. At the same time,
it is shown that, under isothermal conditions, the ratio of the activation energies plays no role.