Thermal Kinetic Analysis Research Articles

A Innovative Method for Evaluating Basswood Pyrolysis Kinetics

A innovative method to simplify calculation the kinetics model is applied to wood pyrolysis. Thermal degradation of basswood was investigated with thermogravimetry. The thermal kinetic TG analysis of basswood under N2 atmosphere was studied at the heating rate of 10,20, 30, 90K/min. All the TG curves are divided into four parts which are drying, slow pyrolysis, fast pyrolysis, and carbonization. The third one is employed to determine the parameters for around 69% of the total mass loss occurs in this range. The peak of the composition is according with DTG curve. It validate assumption of reaction stage.According to the developed method, the react order, reaction energy and pre-exponential factor are obtained, which are in the range of 2.8~4.3, 101.7~126.6 kJ/mol and 2.3×108~7.0×1010min-1, respectively, which are in the range of that reported previously. As a comparison experimental data with calculated data, the well fitting results indicate that this method is appropriate for simulating wood pyrolysis kinetics.

The thermal and detailed kinetic analysis of dipicolinate complexes

The [Cu(pydc)(eim)3]·H2O (1), [Cu(pydc)(4hp)(H2O)] (2) and [Ni(pydc)(3hp)(H2O)2][Cu(pydc)(3hp)(H2O)2]·3H2O (3) complexes (H2pydc = 2,6-pyridinedicarboxylic acid or dipicolinic acid, eim = 2-ethylimidazole, 4hp = 4-hydroxypyridine, 3hp = 3-hydroxypyridine) were studied by thermo-gravimetric analysis at an ambient temperature up to 1000 K under nitrogen atmosphere. The complexes are stable about 350 K, and the decomposition reactions were carried out in seven, three and four stages for the complexes 1, 2 and 3, respectively. Following detailed thermo-gravimetrical analysis of the complexes, the decomposition mechanism was suggested for all complexes. The kinetic analysis of all decomposition stages of each compound was performed except for the final stages. The values of the activation energy, Ea, were obtained using model-free Kissinger–Akahira–Sunose and Flyn–Wall–Ozawa methods for all decomposition stages.

Analysing visual pattern of skin temperature during submaximal and maximal exercises

Aims of this study were to examine our hypotheses assuming that (a) skin temperature patterns would differ between submaximal exercise (SE) and graded maximal exercise test (GXT) and (b) thermal kinetics of Tskin occurring in SE and GXT might be similar in a homogenous cohort. Core temperature (Tcore) also observed in order to evaluate thermoregulatory responses to SE and GXT. Eleven moderately to well-trained male athletes were volunteered for the study (age: 22.2±3.7years; body mass: 73.8±6.9kg; height: 181±6.3cm; body surface area 1.93±0.1m2; body fat: 12.6%±4.2%; V̇O2max: 54±9.9mLmin−1kg−1). Under stabilized environmental conditions in climatic chamber, GXT to volitional exhaustion and 20-min SE at 60% of VO2max were performed on cycle ergometer. Thermal analyses were conducted in 2-min intervals throughout exercise tests. Tskin was monitored by a thermal camera, while Tcore was recorded via an ingestible telemetric temperature sensor. Thermal kinetic analyses showed that Tskin gradually decreased till the 7.58±1.03th minutes, and then initiated to increase till the end of SE (Rsqr=0.97), while Tskin gradually decreased throughout the GXT (Rsqr=0.89). Decrease in the level of Tskin during the GXT was significantly below from the SE [F (4, 40)=2.67, p=0.07, ηp2=0.211]. In the meantime, Tcore continuously increased throughout the SE and GXT (p<0.05). Both GXT and SE were terminated at very close final Tcore values (37.8±0.3°C and 38.0±0.3°C, respectively; p>0.05). However, total heat energies were calculated as 261.5kJ/m2 and 416kJ/m2 for GXT and SE, respectively (p<0.05). Thus, it seems that SE may be more advantageous than GXT in thermoregulation. In conclusion, Tcore gradually increased throughout maximal and submaximal exercises as expected. Tskin curves patterns found to be associated amongst participants at both GXT and SE. Therefore, Tskin kinetics may ensure an important data for monitoring thermoregulation in exercise.

Thermal hazards and kinetic analysis of salicyl hydroxamic acid under isothermal and adiabatic conditions

Kinetic study and thermal hazards analysis on the thermal decomposition of salicyl hydroxamic acid (SHA) was carried out using differential scanning calorimetry (DSC). The isothermal and dynamic differential scanning calorimetric curves were recorded, respectively. The temperature dependence of the observed induction periods suggests an autocatalytic decomposition mechanism, which was supported by the conversion-reduced time plots. The differential and integral isoconversional methods were used to obtain the kinetic parameters. The decomposition mechanism model of the first peak was f(α)=α1.49(1−α)1.59. Moreover, the isothermal temperature induction period were studied to obtain the activation energy, which was close to that obtained by the isoconversional integral method. The adiabatic accelerating calorimetry (ARC) was also employed to evaluate the thermal hazards. The adiabatic activation parameters were also obtained based on the autocatalytic reaction model.

Thermal degradation kinetics of poly(acrylate/α-methyl styrene) copolymers

The poly(acrylate/α-MeSt) copolymers were prepared by emulsion polymerization of butyl acrylate (BA), 2-ethylhexyl acrylate (2-EHA) and α-methyl styrene (α-MeSt). The contents of α-MeSt units combined into the copolymers were confirmed by 1H-NMR. In order to clarify the thermal degradation phenomenon of the copolymers differential scanning calorimetry (DSC) was used to monitor the initial decomposition of the copolymers at low temperatures without obvious weight loss, and gel permeation chromatography (GPC) was used to characterize the molecular weights of the copolymers and the thermally treated ones. The thermal degradation behavior of these copolymers was investigated by thermogravimetry (TGA), and the thermal degradation kinetics was systematically investigated by both Kissinger method, Flynn–Wall–Ozawa (FWO) method and Kissinger–Akahira–Sunose (KAS) method. The GPC and DSC measurements showed that bond breaking of the poly(acrylate/α-MeSt) copolymers occurred at a relatively low temperature compared with neat polyacrylates; the thermal degradation kinetics analysis verified that both the activation energy and pre-exponential factor increased with increasing the content of α-MeSt units in the copolymers; consequently, the decomposition reaction rate constant of the poly(acrylate/α-MeSt) copolymers increased with increasing the amount of combined α-MeSt units in the copolymers when the degradation temperature was higher than 320 °C. FWO method and KAS method revealed that the value of the degradation activation energy of the copolymer sample with higher content of α-MeSt units was higher than that of the copolymer sample with lower content of α-MeSt units at the same conversion.

Thermal degradation, kinetic analysis, and apoptosis induction in human melanoma for oleanolic and ursolic acids

This study deals with the comparative analysis of thermal degradation (including kinetic study) in dynamic air atmosphere, for two similar-structured triterpenoid acids—ursolic (URS) and oleanolic (OLE) acids. As kinetic methods, two integral methods (Kissinger–Akahira–Sunose and Flynn–Wall–Ozawa) and one differential method (Friedman) were used. The “in-depth” kinetic analysis was completed by applying the nonparametric kinetics (NPK) method, which confirmed the multiprocess degradation suggested by isoconversional methods (the observed variation in Ea vs. conversion degree). The NPK method revealed that ursolic acid is degraded solely by two parallel chemical processes, while in the case of oleanolic acid, the processes are accompanied by physical ones. The physicochemical investigation was completed with a bioactivity evaluation regarding the apoptotic process caused by the two compounds in A2058 human melanoma cell line. It was found that the similar-structured triterpenoids possess different biological effects, OLE being antiapoptotic, while URS being strong apoptotic.

Low temperature pyrolysis properties and kinetics of non-coking coal in Chinese western coals

Chinese western low-rank coals known as for its favorable characteristics play a key role in the production of coal oil. In this work, based on the changes in element occurrence during low-temperature pyrolysis of coal, the kinetic and thermodynamic characteristics of coal at 400–500 °C temperatures with 10 °C/min heat rate were studied, which resulted in the drastically cracking of aliphatic groups. However, a significant amount of oxygen-containing functional groups were also found during coal pyrolysis at low temperature followed pseudo-first-order kinetics. According to the low-temperature thermal kinetics analysis of different coals, the activation energy of coking coal is higher than that of non-coking coals, and the activation of non-coking coals is relatively low under the same pyrolysis conditions. The objective of this work is to provide theoretical data about the pyrolysis characteristics of non-coking coal at low temperature and increase the non-coking coal proportion in coking proceeding.

Abnormal crystallization behavior of an (Al86Ni9La5)98Si2 amorphous alloy

An abnormal crystallization phenomenon, indicated by an enlargement in the temperature interval between two exothermal peaks with increasing heating rate, was observed during anisothermal annealing of an (Al86Ni9La5)98Si2 amorphous alloy as the heating rate increased from 5 to 80K/min. The reasons for this special phenomenon are discussed on the basis of a thermal kinetic analysis. It is found that the variation in the crystallization peak temperature with increasing heating rate is closely related to the activation energy of crystallization. The temperature interval between two crystallization events increases with increasing heating rate if the latter event possesses the lower activation energy. Otherwise, the temperature interval between crystallization events is reduced.

Thermal decomposition behavior and de-intercalation mechanism of acetamide intercalated into kaolinite by thermoanalytical techniques

De-intercalation is the inverse of the intercalation process, which can be easily and rapidly determined by thermal analysis. Research on the de-intercalation process is beneficial to exploring the intercalation mechanism that is still unclear in the case of kaolinite intercalation. The objectives of this study were (a) to investigate the thermal decomposition behavior of the intercalation compound of kaolinite and (b) to determine the kinetics of de-intercalation process by thermal analysis to study the mechanism of de-intercalation reaction in kaolinite. Here, the kaolinite–acetamide intercalation compound that was prepared by the direct intercalation method was investigated. X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy results showed that acetamide molecules were inserted into the interlayer space of kaolinite and apparently formed new hydrogen bonds with the inner surface hydroxyl groups of kaolinite. The basal spacing of kaolinite increased from 0.721 to 1.102nm upon intercalation with acetamide. The thermogravimetric (TG) and differential scanning calorimetry (DSC) curves indicated that the decomposition process of the intercalation compound could be divided into two steps. The first step was attributed to the de-intercalation of the intercalated molecules at a temperature of about 181°C, and the second step corresponded to the dehydroxylation of kaolinite at a temperature of about 502°C. The completed kinetic triplet of the de-intercalation reaction was obtained through thermal analysis kinetics methods. The apparent activation energy Ea of the de-intercalation process was calculated to be about 73.6kJmol−1 by an iterative procedure. The pre-exponential factor A was estimated to be in the range of 1.06×1010s−1 to 7.92×1010s−1 by the Dollimore method. The optimized mechanism function of the de-intercalation process of acetamide was determined to be an nth-order chemical reaction through the Malek method. The mechanism function is G(α)=[1−(1−α)1−n]/(1−n), f(α)=(1−α)n and experiments showed that the value of n increased with increased heating rate.

A comparative study of thermal behaviors and kinetics analysis of the pyrotechnic compositions containing Mg and Al

The purpose of this research is to analyze the thermal behavior and kinetics of the pyrotechnic compositions including Al + KClO4, Mg + KClO4, Al + Mg + KClO4, MgAl + KClO4 and Al + MgAl + KClO4 mixtures. The differential scanning calorimeter coupled with thermogravimetry analysis was employed to illustrate the reaction process of these pyrotechnic compositions. Moreover, the bomb calorimetry was utilized to compare experimental and theoretical heats of reaction. The apparent activation energy (Ea), frequency factor (A), the critical ignition temperature of thermal explosion and the self-accelerating decomposition temperature (TSADT), were calculated using Kissinger approach. The results showed that the composition containing MgAl had the highest activation energy and frequency factor; however, the critical ignition temperature of their oxidation reaction was lowest value. In agreement with the theoretical value, the highest experimental heat of reaction for the composition MgAl/KClO4 corresponds to the more complete combustion of metastable MgAl as an alloying mixture of Aluminum and Magnesium with equal proportions. These results suggest that benchmark values for an optimum designation and issues pertinent to the storage and handling of pyrotechnics containing Mg, Al and KClO4.

Thermal Degradation and Kinetics Analysis of Forest Waste for Energy Recovery

The uncertainty surrounding fossil fuels, the need for diversification of energy supply and the environmental awareness concerning climate change, are some of the factors that prompted interest in the 2 nd generation biofuels to deal with sustainability issues that 1 st generation biofuels have been under criticism. This paper examines the possibility of exploiting biomass residues from pines and eucalypts trees that are widely planted in most of Tanzania forests. The properties of saw dust materials originating from these trees were investigated by adopting proximate and ultimate analysis methods. The results revealed both pine and eucalyptus sawdust materials to have high O/C ratios hence, but with low H/C ratios, while their heating values are 152.446 kJ/mol, for pine and 157.576 kJ/mol, for eucalyptus. The study on thermal degradation made using a Thermo-gravimetric analysis conducted by heating the material to 1000 K allowed to study the degradation behavior of the materials at different heating rates of 5, 10, 20 and 40 Kmin -1 . Kinetic study of the materials estimated the activation energy for pine and eucalyptus was to be 152.446 and 157.576 kJ/mol respectively. These results gave an indication that eucalyptus sawdust could be suitable for bio-oil production due to its high volatile level, while pine sawdust for syngas production since it contains high ash content.

The Kinetic Analysis of Oxidized Oil During the High Pressure Air Injection by Thermal Kinetic Analysis

Studying the changing of the oil property with injected air is the prerequisite to apply the HPAI technique in heavy oil reservoir. For this purpose, the oxidation experiments have been carried to study the influence of pressure on heavy oil analyzed by thermogravimetry and differential scanning calorimetry. The results indicated that the oxidized oil with lower activation energy is easier to react with the oxygen. So the higher pressure has positive influence on the coke deposition with stable combustion front. Sufficient coke will bring the possibility for application of HPAI technique without ignition devices in heavy oil reservoirs.

A Candid Approach to Clay Modification via Dehydroxylation for Nanocomposites Application: Investigation of Degradation Kinetics, Reaction Model, and Flammability

ABSTRACTA candid approach to thermal dehydroxylation was used for the modification of clay, to achieve improved thermal stability of a polymer nanocomposite. The modification of clay using alkyl ammonium salt has been found disadvantageous due to various aspects; hence the approach to dehydroxylation was an innovative step to overcome the difficulties in achieving a thermally stable polymer clay nanocomposite. Therefore, a detailed study of thermal stability of polymer clay nanocomposites has been carried out using isoconversional TGA methods of Flynn–Wall–Ozawa and Kissinger. Also, the reaction model involved in the decomposition process of polypropylene (PP) and its nanocomposites have been investigated. From the thermal kinetic analysis, it was clear that the thermal dehydroxylation method can be used as an effective approach for clay modification and the use of organic alkyl ammonium salt can be avoided. Furthermore, to predict the flame‐retardant effectiveness of the thermally dehydroxylated clay, the cone calorimeter analysis was carried out. A comparison of the flame‐retardant effectiveness of the organophillic clay and thermally dehydroxylated clay was presented.

Study on Thermal Decomposition Kinetics of Nano-Cr(OH)&lt;sub&gt;3 &lt;/sub&gt;Powder

Abstract. This paper studies on the thermal decomposition analysis kinetics of nanometer powders. The DTA-TG-DTG curves obtain by SDT 2960 Simultaneous DSC-TGA analysis apparatus. Under the condition of N2atmosphere operation and rise temperature velocity was 10°C·min-1. The mechanism function dα/dt=κ(1-α)nis used to calculate the kinetics factors. Reaction progressionnwas obtained by calculation of the kissinger peak shape factor method. The results showed that the apparent activation energy of nano-Ni(OH)2was 254.027 KJ·mol-1, the pre-exponential factor was 3.062×1036, the reaction progression was obtained as 1.560, the kinetic equation is dα/dt=3.062×1036exp(-30554.166/T)(1-α)1.560

Thermal stability and kinetics analysis of epoxy composites modified with reactive polyol diluent and multiwalled carbon nanotubes

ABSTRACTThe effect of polyether polyol and amino‐functionalized multiwalled carbon nanotubes (NH2‐MWCNTs) on the thermal stability of three‐phase (epoxy/polyol/NH2‐MWCNTs) epoxy composites was investigated. Thermal stability and degradation characteristics of polyol/MWCNTs modified epoxy composites was evaluated using thermogravimetric analysis. The kinetics of thermal degradation was assessed from data scanned at 5, 10, and 20°C/min. Activation energy for degradation of epoxy nanocomposites was calculated using different differential and integral methods, that is, Kissinger's, Flynn–Wall–Ozawa, Coats–Redfern, and Horowitz–Metzger methods. In addition, the integral procedure decomposition temperature was determined to evaluate the inherent thermal stability of the modified composite system. Rate of thermal degradation in MWCNT/Polyol samples was found to be reduced significantly while activation energy of degradation was increased compared to unmodified epoxy composite. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41558.

Obtaining reliable phenomenological chemical kinetic models for real-world applications

The derivation of chemical kinetics by the thermal analysis community has a checkered past, with numerous papers published using substandard methodology. The ICTAC kinetics committee has taken on the task of upgrading the quality of thermal analysis kinetics through a series of workshops and publications. However, the resulting publications from those efforts by design do not cover all important aspects in detail. This paper explores two issues in greater depth—the optimum selection of heating rates for kinetic determination based on statistical error considerations and the importance of using a diverse set of thermal histories, including but not limited to isothermal and linear heating, to better constrain and validate global models.

Synthesis, characterization of monodispersed MgO microspheres and thermal decomposition kinetics of its precusor

Monodispersed MgO microspheres were successfully synthesized by a simple solvothermal method using PEG-400 as solvent. The samples were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results reveal that the precusor was monoclinic Mg5(CO3)4(OH)2·4H2O and composed of nanosheets with the thickness of about 250 nm. By calcining the precusor at 500 °C for 5 min, cubic MgO with similar morphology was obtained. According to the SEM images, it is found that the volume ratio of PEG-400 to deionized water is considered as a crucial factor in the evolution of the morphology. Based on the SEM images obtained under different experimental conditions, a possible growth mechanism which involves self-assembly process was proposed. The thermal decomposition process of MgO precusor was studied by thermogravimetry-differential thermogravimetry (TG-DTG) at different heating rates in air. Thermal analysis kinetics results show that the most probale mechanism models of MgO precusor are An and D3, respectively. In addition, isothermal prediction was studied to quantitatively characterize the thermal decomposition process.

Study on Kinetics of Nano-Ni(OH)&lt;sub&gt;2 &lt;/sub&gt;Powder Ethanol Desorption Process

This paper studies on the thermal analysis kinetics of nanometer powders ethanol desorption process.The DTA-TG-DTG curves obtain by SDT 2960 Simultaneous DSC-TGA analysis apparatus. Under the condition of N2atmosphere operation and rise temperature velocity was 10°C·min-1. The mechanism functionis used to calculate the kinetics factors. Reaction progressionnwas obtained by calculation of the kissinger peak shape factor method. The results showed that the apparent activation energy of nano-Ni(OH)2was 73.210 kJ·mol-1, the pre-exponential factor was 2.349×1012, the reaction progression was obtained as 1.2767, the kinetic equation is

Effect of doping Al on the liquid oxidation of Sn–Bi–Zn solder

The liquid oxidation behaviors of Sn–40Bi–2Zn and Sn–40Bi–2Zn–0.005Al solders were investigated from thermal dynamics and kinetics analysis. The characteristics of surface oxidation film at 170 °C were studied by thermo gravimetric analysis and X-ray photoelectron spectroscopy (XPS). Sn–40Bi–2Zn solder performed inferiorly in oxidation prevention performance, due to the formation of ZnO, which exhibits lower Gibbs free energy of formation and higher growth rate. Trace amount of Al addition, however, alleviated the oxidation behavior of Zn. XPS depth profile results indicated that the surface layer of Sn–40Bi–2Zn–0.005Al consisted of oxides of Al and Zn formed on the outer surface of the solder film and in the subsequent layer, mainly formed by the oxides of Sn, Bi. Al, basically formed as Al2O3, segregated towards the outer surface, seemed to deter the Zn oxidation on the solder surface.

Investigations of the structure and thermal kinetic analysis of sugarcane bagasse char during non-isothermal CO2 gasification

The CO2 gasification reactivity, thermal behaviour and activation energies of sugar cane bagasse (SCB) chars prepared at 500, 800 and 900°C were investigated by using thermogravimetric analysis (TGA) under non isothermal conditions at different heating rates of 20, 30 and 40°Cmin−1. The characteristics (physical and chemical structures) of the sugar cane chars as a function of pyrolysis temperature have been studied by applying Brunauer–Emmett–Teller (BET) surface area and Fourier transform infrared spectroscopy (FTIR) techniques. The results have demonstrated that the gasification of SCB chars took place almost completely in one-stage process as it has been shown by the presence of only one peak in DTG curve. The char reactivity is an inversely proportional to the pyrolysis temperature and directly to a gasification heating rate. As pyrolysis temperature increases, the char physical structures (BET surface area, pores characteristics) are directly proportional to the pyrolysis temperature. The hydroxyl, aliphatic C–H, carbonyl and olefinic C=C groups were lost at high pyrolysis temperatures (800 and 900°C). The activation energies were estimated by using Vyazovkin and Ozawa–Flynn–Wall methods, which have resulted in the mean of activation energy values of 70.44–88.37, 89.16–101.55 and 107.20–115.29kJmol−1, respectively for char prepared at 500, 800 and 900°C. Finally, Vyazovkin and Ozawa–Flynn–Wall methods were effectively applied to predict the reaction mechanism of thermal gasification.