Investigation of the Thermal Decomposition Behavior of Oleuropein with Many Pharmacological Activities from Olive by Thermogravimetry

Due to the existence of poly-hydroxyl structures,the temperature may have an effect on the thermal stability of oleuropein for its applications.In the current study,the thermal decomposition process and kinetics behavior of oleuropein from the olive resource were researched by thermogravimetric theoretical analysis methods and non-isothermal kinetics simulation.The results of thermogravimetry analysis showed the whole thermal decomposi-tion process of oleuropein involved two stages,with 21.22%of residue.It was also revealed that high heating rates of more than 20 K min^(-1) led to significant thermal hysteresis and inhibited the whole thermal decomposition behavior of oleuropein.Moreover,an investigation of the thermal decomposition kinetics indicated that the non-isothermal decomposition behavior followed a D3 model during thefirst stage(three-dimensional diffusion,Jander equation)and a D1 model in the second stage(one-dimensional diffusion).For thefirst and second ther-mal decomposition stages,the Kissinger,Friedman,Flynn-Wall-Ozawa,and Coats–Redfern four methods were applied to determine the activation energy(E=143.72 and 247.01 kJ mol^(-1))and Arrhenius preexponential factor(ln A=26.34 and 42.45 min^(-1)),respectively.Therefore,the study will provide good theoretical guidance for ther-mal stability and thermal transformation application of oleuropein.It will be suitable for low-temperature appli-cations in the cosmetic,food supplement and pharmaceutical industries.

Study on thermal decomposition kinetics of azobenzene-4,4′-dicarboxylic acid by using compensation parameter method and nonlinear fitting evaluation

Recently,azobenzene-4,4'-dicarboxylic acid(ADCA)has been produced gradually for use as an organic synthesis or pharmaceutical intermediate due to its eminent performance.With large quantities put into application in the future,the thermal stability of this substance during storage,transportation,and use will become quite important.Thus,in this work,the thermal decomposition behavior,thermal decomposition kinetics,and thermal hazard of ADCA were investigated.Experiments were conducted by using a SENSYS evo DSC device.A combination of differential iso-conversion method,compensation parameter method,and nonlinear fitting evaluation were also used to analyze thermal kinetics and mechanism of ADCA decomposition.The results show that when conversion rate α increases,the activation energies of ADCA's first and main decomposition peaks fall.The amount of heat released during decomposition varies between 182.46 and 231.16 J·g^(-1).The proposed kinetic equation is based on the Avrami-Erofeev model,which is consistent with the decomposition progress.Applying the Frank-Kamenetskii model,a calculated self-accelerating decomposition temperature of 287.0℃is obtained.

Crystal Structure, Thermal Decomposition Behavior and the Standard Molar Enthalpy of Formation of a Novel 3D Hydrogen- Bonded Supramolecular [Co（HnicO）2·（H2O）2]

Hydrothermal synthesis and X-ray characterized 3D supramolecular networks were constructed by [Co（HnicO）2·（H2O）2] （HnicOH=2-hydroxynicofinic acid） （1） as building block via abundant dimeric homomeric （N--H…O） and unusually cyclic tetrameric heteromeric （O-H…O） hydrogen-bonds. It is noted that there exist unusually linear metal-water chains comprised of tetrameric units linked by vertexes sharing cobalt centers through hydrogen-bonding. TG-DTG curves illustrated that thermal decomposition was completed by two steps, one is the loss of two terminal water molecules in the range of 156--234℃, and the other is the pyrolysis of HnicO ligand in the range of 234--730 ℃. The standard molar enthalpy of formation of the complex was determined to be （-1845.43± 2.77） kJ·mol^-1 by a rotary-bomb combustion calorimeter.