A kinetic study of hydrogen isotope exchange was carried out in a H2/Pd membrane/organic compound system for a number of compounds in the 0.2–20 kPa H2 pressure range. The results suggest a low specificity of the reaction kinetics for the compounds used. Possible reaction mechanisms are discussed and analyzed.
Studies on the reaction kinetics and mechanism of the synthesis of the Zn2.5VMoO8 compound in the solid state have been carried out in situ in a high-temperature X-ray diffraction attachment. The apparent
activation energy, 21226 kJ mol-1 was calculated by using the diffusion controlled Ginstling-Brounstein model. There was also determined a temperature dependence
of unit cell parameters for Zn3V2O8 and Zn2.5VMoO8.
Faraday induced the mechanochemical reduction of AgCl with Zn, Sn, Fe and Cu in 1820, using trituration in a mortar. This
experiment is revisited, employing a mortar-and-pestle and a ball mill as mechanochemical reactors. The reaction kinetics
depends both on the thermochemical properties and the hardness of the reactants. When using Zn as the reducing agent, Faraday
likely observed a mechanically induced self-sustaining process (MSR), or at least he came very close to doing so.
Reaction kinetics of the formation of TiC by calciothermic reduction of TiO2 in presence of carbon have been investigated using thermal analysis (TG-DTA) of a powder mixture of TiO2, Ca, and C in argon atmosphere at different heating rates. Both the reaction initiation and the peak temperatures are found
to increase with heating rates. The appearance of exothermic peaks in the DTA plots after Ca melting indicates the reduction
of TiO2 by liquid calcium and formation of TiC by in-situ reaction of Ti with C. The apparent activation energy of the process has
been found to be 170.80.5 kJ mol-1.
Authors:A. Hadj Mebarek, C. Cogneville, S. Helle, and S. Walter
The formation of alkali metal alcoxides by an alcohol reacting on the elemental metal itself cannot be completed under stoichiometric
conditions. As a consequence of solvation, the chemical activity of the reacting alcohol is drastically reduced. Thus, the
reaction cannot undergo completion without a large excess of alcohol with respect to the alkali metal. Moreover, solvation
processes can drop the reaction kinetics down to nearly zero. When an excess of alkali metal is reacted with alcohol, the
heat accumulated by solvation can be suddenly released by an addition of pure alcohol. Extremely dangerous thermal runaways
can be started this way.
Conversion (α) and the glass transition temperature (Tg) were investigated during the isothermal cure of endo-dicyclopentadiene (DCPD) with a Grubbs catalyst for different temperatures using differential scanning calorimetry. Conversion
vs. In (time) data at an arbitrary reference temperature were superposed by horizontal shift and the shift factors were used
to calculate an Arrhenius activation energy. Glass transition temperature vs. conversion data fell on a single curve independent of cure temperature, implying that reaction of the norbornene and cyclopentene
ring of DCPD proceeds in a sequential fashion. Implications of the isothermal reaction kinetics for self-healing composites
Authors:R. H. Meinhold, H. Atakul, T. W. Davies, and R. C. T. Slade
The structural changes occurring during the dehydroxylation of kaolinite have been followed using flash calcination to produce kinetically frozen calcines. The percentage of dehydroxylation was varied by changing the furnace residence time or temperature and/or heating speed. These calcination conditions affected the reaction kinetics, but the products depended only on the extent of dehydroxylation.
The non-parametric kinetics (NPK) method has been recently developed for the kinetic treatment of thermoanalytical data. The
most significant feature of this method is its ability to provide information about the reaction kinetics without any assumptions
either about the functionality of the reaction rate with the degree of conversion or the temperature. This paper presents
the results of the application of the method to adiabatic calorimetry. Some data have been obtained by numerical simulation,
but also the thermal decomposition of DTBP, a well known first order reaction, has been studied, being the obtained results
in good agreement with literature.