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Abstract

Oxygen (O2) or air is widely applied globally to yield cumene hydroperoxide (CHP) in a cumene oxidation tower. In previous studies, CHP has been identified as a thermally hazardous chemical. This study was used to evaluate thermal hazard of CHP in cumene using differential scanning calorimetry and vent sizing package 2 (VSP2). Self-accelerating decomposition temperature (SADT), self-heating rate, exothermic onset temperature (T 0), critical temperature (T c), time to maximum rate (TMR), activation energy (E a), etc., were employed to prevent and protect thermal runaway reaction and explosion in the manufacturing process and/or storage area. The reaction order (n) of CHP was evaluated to be 0.5 in this study. The E a was determined to be 122 kJ mol−1 by VSP2. High volume of CHP with 0 rpm of stirring rate by VSP2 was more dangerous than a low one. Control of stirring rate should be a concern in process safety management program. In view of proactive loss prevention, inherently safer handling procedures and storage situations should be maintained in the chemical industries.

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Abstract  

Lauroyl peroxide (LPO) is a typical organic peroxide that has caused many thermal runaway reactions and explosions. Differential scanning calorimetry (DSC) was employed to determine the fundamental thermokinetic parameters that involved exothermic onset temperature (T0), heat of decomposition (ΔHd), and other safety parameters for loss prevention of runaway reactions and thermal explosions. Frequency factor (A) and activation energy (Ea) were calculated by Kissinger model, Ozawa equation, and thermal safety software (TSS) series via DSC experimental data. Liquid thermal explosion (LTE) by TSS was employed to simulate the thermal explosion development for various types of storage tank. In view of loss prevention, calorimetric application and model analysis to integrate thermal hazard development were necessary and useful for inherently safer design.

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Abstract  

A new method of the multiple rate iso-temperature was used to define the most probable mechanism g(α) of a reaction; the iterative iso-conversional procedure has been employed to estimate apparent activation energy E a, the pre-exponential factor A was obtained on the basis of E a and g(α). In this new method, the thermal analysis kinetics triplet of dehydration of calcium oxalate monohydrate is determined, which apparent activation energy E a is 82.83 kJ mol-1, pre-exponential factor A is 1.142105-1.235105 s-1, the most probable mechanism belongs to phase boundary reaction Rn with integral form g(α)=1-(1-α)n and differential form f(α)=n(1-α)1-(1/n), where accommodation factor n=2.40-1.40.

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Journal of Thermal Analysis and Calorimetry
Authors: Liu Yongjun, Ding Yangjun, Nan Zhaodong, Sun Haitao, and Zhang Honglin

Abstract  

The power-time curves of bacterial growth at different temperatures were determined by using the 2277 Thermal Activity Monitor (Sweden). From these curves, the growth rate constant (μ) and activation energy (E a) were calculated. According to the transition state theory of reaction dynamics, the activation entropy (ΔS), activation Gibbs free energy (ΔG) and equilibrium constant (K ) of the activation state could be calculated. These results permitted thermodynamic analysis of the bacterial growth metabolism.

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Journal of Thermal Analysis and Calorimetry
Authors: C. Tomasi, M. Scavini, A. Speghini, M. Bettinelli, and M. Riccardi

Abstract  

The devitrification of glassy PbGeO3 was studied and interpreted by means of isothermal and non-isothermal Johnson-Mehl-Avrami equations. In the case of the non-isothermal approach, several approximated equations proposed by various authors were considered in order to obtain both the activation energy E a and the Avrami morphological coefficient n of the crystallisation process. A critical discussion of the Avrami coefficient on the basis of experimental morphological evidence is also presented.

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Abstract  

Taking into account the importance of thermal stability in the liquid crystals field, the study presents the thermal behavior of some ferrocene containing Schiff bases. Some other kinetic characteristics, such as reaction order (n), activation energy (E a) and pre-exponential factor (lnA) have been also evaluated. The thermal stability series of Schiff bases was established analysis associated with three parameters (T d, T max, E a) is: S6<S4<S3<S5<S1<S2.

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Abstract  

The activation energy,E a taken from the thermal decomposition of KMnO4 and AgMnO4 was compared with the energy of the longest wavelength O→Mn ‘charge transfer’ (CT) transition. TheE a and CT correlation was found in these systems. However, such relationship can be valid when in the dissociation process the electron transfer is assumed to be the rate determining step. Thus, the permanganates as well as the previously studied chromates, are positive examples showing that in some cases, the energies derived from both methods can be comparable.

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Abstract  

Thermal degradation behavior using thermogravimetry (TG), chemical composition and crystallinity by X-ray diffraction of white and naturally colored cotton fibers (ruby, beige, brown and green) were studied. Flynn-Wall-Ozawa method was used to investigate the thermal decomposition kinetics of the different fibers. The white cotton fiber has higher thermal stability and higher apparent activation energy (E a) value compared to the colored fibers. There are no significant differences in initial temperature of degradation in air or in nitrogen atmosphere for the same type of fiber. Chemical composition and crystallinity influenced the thermal degradation behavior of the fibers studied.

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Abstract  

The elaboration of Na+ super-ionic conductor (NaSICON) ceramics is studied in this work. These solid electrolytes can be used as sensor for detection of polluted gases in air. Two sorts of ceramics with different chemical compositions are synthesised by soft chemistry route: a zirconium-based NaSICON and a hafnium-based NaSICON. DTA-TG and temperature depending X-ray diffractometry were used to follow the thermal decomposition of the precursor phases. The electrical properties of these ceramic sodium ionic conductors are investigated by complex impedance spectroscopy (CIS). The substitution of the zirconium by the hafnium increases the ceramic conductivity and decreases the activation energy E a (from 0.29 to 0.12 eV).

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Abstract  

The crystallization mechanism of the glass-ceramics obtained from Romanian (Şanoviţa) basalt in the presence of 3 and 5% CaF2 as nucleation agent has been investigated under non-isothermal conditions using DTA technique. The activation energies of the crystallization processes were calculated using the Kissinger-Akahira-Sunose, Ozawa-Flynn-Wall, Starink and Tang isoconversional methods. The monotonous decreases in the activation energy (E a) with the crystallized fraction (α) confirms the complex mechanism of the glass-ceramics crystallization process. It has been proved that the Johnson-Mehl-Avrami model cannot be applied for the studied glass-ceramics crystallization process.

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