Simultaneous Thermodynamic and Kinetic Parameters Determination Using Differential Scanning Calorimetry
2011
Problem statement: The determination of reaction kinetics is of major importance, as for
industrial reactors optimization as for environmental reasons or energy limitations. Although
calorimetry is often used for the determination of thermodynamic parameters alone, the question that
arises is: how can we apply the Differential Scanning Calorimetry for the determination of kinetic
parameters. The objective of this study consists to proposing an original methodology for the
simultaneous determination of thermodynamic and kinetic parameters, using a laboratory scale
Differential Scanning Calorimeter (DSC). The method is applied to the dichromate-catalysed hydrogen
peroxide decomposition. Approach: The methodology is based on operating of experiments carried
out with a Differential Scanning Calorimeter. The interest of this approach proposed is that it requires
very small quantities of reactants (about a few grams) to be implemented. The difficulty lies in the fact
that, using such microcalorimeters, the reactants temperature cannot directly be measured and a
particular calibration procedure has thus to be developed, to determine the media temperature in an
indirect way. The proposed methodology for determination of kinetics parameters is based on
resolution of the coupled heat and mass balances. Results: A complete kinetic law is proposed. The
Arrhenius parameters are determined as frequency factor k0 = 1.39×109 s−1 and activation energy E = 54.9 kJ mol−1. The measured enthalpy of reaction is ΔrH=−94 kJ mol−1. Conclusion: The comparison of the results obtained by such an original methodology with those obtained using a conventional laboratory scale reactor calorimetry, for the kinetics determination of, shows that this new approach is very relevant.
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