Kinetic Investigation of Thermal Decomposition Reactions of Podophyllic Acid and Picropodophyllic Acid

摘要

The thermal behavior and thermal decomposition kinetic parameters of podophyllic acid and picropodophyllic acid in a temperature-programmed mode have been investigated by means of DSC and TG-DTG. The kinetic model functions in differential and integral forms of the thermal decomposition reactions mentioned above for leading stage were established. The kinetic parameters of the apparent activation energy Ea and per-exponential factor A were obtained from analysis of the TG-DTG curves by integral and differential methods. The most probable kinetic model function of the decomposition reaction in differential form was 2/3?α~(-1/2) for podophyllic acid and 1/2? (1-α)~(-1) for picropodophyllic acid. The values of Ea indicated that the reactivity of picropodophyllic acid was highter than that of podophyllic acid in the thermal decomposition reaction. The values of the entropy of activation ?S~≠, enthalpy of activation ?H~≠ and free energy of activation ?G~≠ of the reactions were estimated.