The kinetic and solvent isotope effects during the maleic acid heterogeneous catalytic hydrogenation and deuteration in the
light and heavy water have been studied. Also the effect of the γ and neutron irradiation on the Ni−ZnO catalysts (with various
ratios of components) on the reaction kinetics and mechanism has been measured, as well as the effect of pH on the adsorption
behaviour of maleic acid and the temperature depencence of the reaction rate. Existence of different adsorption centers for
hydrogen and maleic acid could be deduced from these experiments. A reaction mechanism based on the two-dimensional diffusion
of components in the surface is proposed.
The thermal stability of lithium-ion battery cathode could substantially affect the safety of lithium-ion battery. In order
to disclose the decomposition kinetics of charged LiCoO2 used in lithium ion batteries, thermogravimetric analyzer (TG) and C80 microcalorimeter were employed in this study. Four
stages of mass losses were detected by TG and one main exothermic process was detected by C80 microcalorimeter for the charged
LiCoO2. The chemical reaction kinetics is supposed to fit by an Arrhenius law, and then the activation energy is calculated as Ea=148.87 and 88.87 kJ mol−1 based on TG and C80 data, respectively.
For complex decomposition reactions, traditional methods, such as TG and DSC cannot fully resolve all of the steps in the
reaction. Evolved gas analysis (EGA) offers another tool to provide more information about the decomposition mechanism. The
decomposition of sodium bicarbonate was studied by TG, DSC and EGA using a simultaneous thermal analysis unit coupled to a
FTIR. The decomposition of sodium bicarbonate involves two reaction products H2O and CO2, which are not evident from either TG or DSC measurements alone. A comparison of the reaction kinetics from TG, DTG and EGA
data were compared.
A new chemical species of bis(acetonitrile)bis(acetylacetonato)technetium(III), [Tc(acac)2(CH3CN)2]+, has been prepared by the reaction of tris(acetylacetonato)technetium(III) with acetonitrile in the presence of a strong acid, perchloric or hydrochloric acid. The reaction kinetics were followed by observing spectral change of Tc(acac)3 in the UV-visible region. The complex has been characterized by combination of elemental analyses, IR and UV-visible spectrophotometry, ion-exchange chromatography, and paper electrophoresis. Applicability of this substance to synthesize mixed-ligand technetium(III) complexes was discussed based on the solubility of this complex and the ease of substitution of the acetonitrile ligand.
The reaction kinetics of the mesoporous powder, MCM-TP, anchored with synergistic extractant TOPO-P204, with Pd2+ in spent fuels have been investigated. The results showed that the reaction rate was independent of pellet size, which suggested
that the powder pellet was highly porous and was composed of plate-like “grains”. This analysis was confirmed by observing
the surface and cross section of the pellet with SEM. It provided the physical basis for establishing the liquid-solid reaction
model of mesoporous powders: P-G* model. The calculated curves from the model were in good agreement with the experimental results.
The reaction [Mn(NH3)2]Cl2+ 4NH3 ⇄ [Mn(NH3)6]Cl2, which is of potential use in chemical heat pumps, was studied by means of differential scanning calorimetry. The thermodynamic conditions, the enthalpy of the reaction, and the heat capacity values for MnCl2, [Mn(NH3)2Ch and [Mn(NH3)6Cl2 were measured. The influence of the reaction kinetics of the experimental procedure and some parameters such as sample temperature, ammonia pressure and scanning rate was examined.
Some specific features of the thermochemistry of epoxy-amine curing at the later stages of the reaction are considered. Possible
mechanism of cross-linking and the question about the driving force leading to the infinite network are discussed. The coupling
of the reaction kinetics and rearrangement of the chains crosslinked into the rigid supramolecular structure is the essential
feature of epoxy-amine vitrified system. It has been proposed that owing to the contribution from the side process, different
curing temperatures can result in the structures with different Tg. It was also established that reaction of epoxy ring opening alone is not responsible for the residual curing. The latter
is the result of the side processes. As compared with the reaction of epoxy ring opening the side processes are strongly dependent
on the geometrical aspects.
Authors:Yuh Kumekawa, Motohiro Hirai, Yuhki Kobayashi, Satoshi Endoh, Eri Oikawa, and Takuya Hashimoto
Thermodynamic and kinetic stabilities of CuAlO2 and CuGaO2 have been evaluated by using thermogravimetry and thermodynamic calculations. It has been revealed that CuAlO2 and CuGaO2 are not thermodynamically stable in air below 800 °C and 1,200 °C, respectively, and that the oxidation reaction, 4CuMO2 + O2 → 2CuO + 2CuM2O4 (M = Al, Ga), should occur if the reaction kinetics are high enough. However, rate constants and activation energies indicated
slow kinetics of the oxidation reaction, showing kinetic stability of CuMO2 even under some thermodynamically unstable temperatures and atmospheres. It was also concluded that CuAlO2 showed higher thermodynamic and kinetic stability than CuGaO2.
This article described the synthesis and mesomorphic behavior transition of a novel liquid crystalline (LC) epoxy resin 4-(2,3-epoxypropoxy)biphenyl,4″-(2,3-epoxypropoxy)phenyl-4′carboxylate (EBEPC), which combined a hydroxyl benzoic aromatic ester and biphenol rigid-rod group. EBEPC showed a clear nematic schlieren texture under curtain conditions. The reaction kinetics of EBEPC cured by 4,4′-diaminodiphenyl-methane (DDM) was studied by using an isoconversional method under isothermal conditions with differential scanning calorimetry (DSC). The isothermal DSC data can be fitted reasonably by an autocatalytic curing model. Smectic phases had been observed in the EBEPC/DDM curing system. The results of DSC showed that the formation of the LC phase had pronounced influence on the curing reaction.
Authors:J. Rocco, J. Lima, A. Frutuoso, K. Iha, M. Ionashiro, J. Matos, and M. Suárez-Iha
The thermal decomposition of ammonium perchlorate (AP)/hydroxyl-terminated-polybutadiene (HTPB), the AP/HTPB solid propellant,
was studied at different heating rates in dynamic nitrogen atmosphere. The exothermic reaction kinetics was studied by differential
scanning calorimetry (DSC) in non-isothermal conditions. The Arrhenius parameters were estimated according to the Ozawa method.
The calculated activation energy was 134.5 kJ mol-1, the pre-exponential factor, A, was 2.04×1010 min-1 and the reaction order for the global composite decomposition was estimated in 0.7 by the kinetic Shimadzu software based
on the Ozawa method. The Kissinger method for obtaining the activation energy value was also used for comparison. These results
are discussed here.