Phase Boundary Reaction Model Research Articles

Insight into the high-temperature reaction characteristics of CaS with CO2: Experimental study and theoretical calculation

To address the challenge of optimizing the utilization of industrial by-product gypsum, this study proposes a two-step reductive decomposition process for the production of quicklime from industrial by-product gypsum. In the initial step, a blend of CaS and CaO is generated through the low-temperature reductive decomposition of gypsum. Subsequently, the decomposition products undergo oxidation in a carbon dioxide environment, yielding activated quicklime. While the reductive decomposition of gypsum has been extensively documented, there exists a significant research gap concerning the reaction between CaS and CO2 at elevated temperatures. This study investigates the high-temperature reaction characteristics and reaction mechanism of the CaS and CO2 system through a combination of experiments, isothermal kinetic analysis, and density functional theory (DFT) calculations. Furthermore, it offers a comparative analysis of the physicochemical properties of quicklime produced via three different methods, using desulfurization gypsum as an illustrative example. It was observed that the reaction rate of CaS with CO2 markedly increased with rising temperature and CO2 concentration. The reaction of CaS in a CO2 atmosphere adhered to the phase boundary reaction model. DFT calculations were employed to determine the reaction pathway for the interaction between CaS and CO2, which can be summarized as follows: CaS + CO2 → CaSO + CO, CaSO + CO2 → CaSO2 + CO, CaSO2 + CO2 → CaSO3 + CO, CaSO3 → CaO + CO2. The lime generated through the two-step process of desulfurization gypsum (FGD) exhibited a superior pore structure and reactivity when compared to lime produced via the one-step process of FGD gypsum and that obtained through limestone calcination.

Gas-based reduction and nitridation for synthesis of vanadium nitride: Kinetics and mechanism

We investigate the isothermal kinetics of the reduction and nitridation of V2O3 using NH3. The reaction mechanism is also discussed based on the thermodynamic and experimental results. The reaction procedure between V2O3 and NH3 can be divided into two stages. The first stage is mainly the deoxygenation process, whereas the second is the nitridation process. The deoxygenation process follows a two-dimensional phase boundary reaction model, and a modified integrated model (IM + diffusion) was proved to be the best function at temperatures above 1023 K. For the second stage, the three-dimensional diffusion model is determined as the mechanism function. Thermodynamic analysis predicts the feasibility between V2O3 and NH3 to form VN. The VN product is a solid solution (VNxOy) (0 < x,y < 1, x + y = 1), which can be formed at 873 K. The Rietveld refinement analysis indicates the N content of VNxOy gradually increases with increasing temperature. The highest N content is approximately 15.83% at 1073 K for 2 h.

Effects of pre-oxidation on the hydrogen-rich reduction of Panzhihua ilmenite concentrate powder: Reduction kinetics and mechanism

The objective of this study was to investigate the effect of pre-oxidation treatment on the hydrogen-rich reduction of Panzhihua ilmenite concentrate powder on the reduction kinetics and mechanisms. In this study, reduction processes of raw and pre-oxidized ilmenite concentrates reduced by H2/CO mixtures (H2/CO = 0.4 and H2/CO = 2.5) at 950, 1000, and 1050 °C were systematically investigated using a thermal analyzer. The hydrogen-rich reduction rate was accelerated by the pre-oxidation treatment of raw ilmenite concentrate and an increase in H2 in H2/CO mixtures. The hydrogen-rich reduction of raw and pre-oxidized ilmenite concentrates can be divided into two stages according to the first derivatives of the reduction process: Fe3+ to Fe2+ and Fe2+ to Fe. The results of the research on the model function demonstrated that the reaction mechanism of raw and pre-oxidized ilmenite concentrates were three-dimensional diffusion models in the first stage. In the second stage, the reaction mechanism of the raw ilmenite concentrate was a phase boundary reaction model, and for the pre-oxidized ilmenite concentrate, it was a chemical reaction model. Furthermore, the apparent activation energies of both raw and pre-oxidized ilmenite concentrates under different reducing atmospheres were determined and compared. It was demonstrated that pre-oxidation treatment could effectively reduce the apparent activation energies of the reduction reaction. It is feasible to combine the advantages of the pre-oxidation treatment and hydrogen-rich reduction with a higher hydrogen ratio for the efficient reduction of Panzhihua ilmenite concentrate.

Oxidative self-heating modeling of iron sulfides during the processing of high sulfur oil

Scanning electron microscope (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD) were used to analyze the surface micromorphology and components of the iron oxide sulfide powders respectively. Differential scanning calorimetry (DSC) and thermogravimetry (TG) were used to investigate the self-heating properties. It was observed that temperature had a significant effect on the microscopic morphology and composition of the sulfide products. The product powders were homogeneously distributed in small particles and the composition of the products were converted from non-stationary FeS to FeS2 with the sulfidation temperature increased. The apparent activation energy at a sulfidation temperature of 300 °C was 66.5 % of that at a sulfidation temperature of 150 °C. The apparent activation energies were 114.65 kJ/mol, 95.41 kJ/mol, 89.5 kJ/mol and 76.27 kJ/mol respectively at 150 °C, 200 °C, 250 °C and 300 °C during the self-heating reaction phase. There was only one main weight loss phase for the 100 °C, 150 °C and 200 °C products, while the 250 °C and 300 °C products had an additional weight loss phase before the main weight loss phase. The apparent activation energies of the main weight loss phase of the five temperature products were 318.1–333.7 kJ/mol, 266.2–293.2 kJ/mol, 212.7–234.0 kJ/mol, 174.7–193.1 kJ/mol and 168.7–188.7 kJ/mol, respectively. The apparent activation energies of the first weight loss phase of the 250 °C and 300 °C products were 217.4–243.2 kJ/mol and 198.2–214.6 kJ/mol respectively. The mechanism function for the thermal oxidation of elemental sulfur in the first weight loss phase was determined to follow the spherical contraction phase boundary reaction model, i.e. g(α)= [1-(1-α)1/3]m. In the main weight loss phase, the mechanism function for the thermal oxidation of iron sulfate followed the random nucleation followed by subsequent growth model, i.e. g(α)= [ln(1-α)]m.

Mechanochemically synthesized Al–Fe (oxide) composite with superior reductive performance: Solid-state kinetic processes during ball milling

Recently, mechanical ball milling (BM), a simple and green powder processing method, has been successfully applied to improve the performance of zero-valent metals (ZVMs) for efficient water treatment. However, until now BM is still regarded as a “black box” in which the processes of the solid-state reaction during activation remain unclear. In this paper, firstly, FeSO4·7H2O crystal was used to activate and modify inert microscale zero-valent aluminum (mZVAl) by BM to synthesize Al–Fe (oxide)bm composite that showed superior reactivity in reductive removal of various contaminants and excellent reusability, which may be mainly ascribed to the newly formed iron oxide layer on mZVAl by mechanochemical reaction. At the same time, the formation of iron oxides on mZVAl was closely related to BM parameters. Further kinematic analysis revealed that the occurrence of mechanochemical reaction depended on the impact energy and input energy, which BM speed and BM time were two main factors determining reaction extent on the premise that the precursors were full dose. Moreover, kinetic fitting uncovered the solid-state reaction mechanism between mZVAl and FeSO4·7H2O conformed to three-dimensional diffusion and phase boundary reaction models. This study ponders deeply upon the mechanochemical process and solid reaction mechanism during the preparation of Al–Fe (oxide)bm composite, which deepens comprehensions of material synthesis procedures by BM and promotes applications of ZVM-based composite in polluted water or wastewater treatment.

Studies on kinetic and reaction mechanism of oil rolling sludge under a wide temperature range

ABSTRACT Oil rolling sludge (ORS) is a kind of hazardous secondary energy and pyrolysis is an effective technology to recover oil with little secondary pollution. Extant research focused on the pyrolysis of petrochemical sludge (PS) under low-medium temperature (<900 K), few research was about ORS. Therefore, the pyrolysis behavior of ORS was investigated under a wide temperature range (300–1270 K) by thermogravimetric analyzer (TG/DTG) and X-ray diffraction spectrometer (XRD) in this research, which showed that the pyrolysis process could be divided into four stages: desorption of moisture and adsorbed gas, decomposition of light oil, cracking of heavy oil and coke formation, and interaction of mineral and coke. In addition, the model-free Starink and the Malek methods were applied to calculate kinetic triplets and determine the most probable mechanism of stage-2 to stage-4 based on various mechanism formulas. The results showed that the apparent activation energy varied from 44.77 to 196.36 kJ/mol and increased with the increase of conversion rate, while pre-exponential factor changed irregularly with heating rate. The stages 2–4 complied with the 0.7-level chemical order reaction model, random nucleation and nuclear growth reaction model and phase boundary reaction model, respectively. This study provided a theoretical support for the optimization of process conditions, prediction of product distribution and design of industrial equipment.

Palm oil-based bio-PCM for energy efficient building applications: Multipurpose thermal investigation and life cycle assessment

This study aims at investigating the potential use of a bio-based phase change material, i.e. expired palm oil from the food industry, as a more sustainable alternative to petrochemical-based organic PCMs. To this purpose, thermogravimetric analysis (TGA) and isoconversional methods (Starink and Miura-Maki methods) are applied and the main thermo-physical properties of the blend are investigated by means of differential scanning calorimetry (DSC) and extensive thermal monitoring in a controlled realistic environment. Finally, a life cycle assessment is used to evaluate the environmental impact of the bio-based material in comparison to the more common petrochemical-based application. Kinetic analysis results indicate the two dimensional phase boundary reaction model as the most reliable scheme for describing the oxidation of palm oil, with an activation energy of about 73 kJ · mol−1. The DSC and the thermal monitoring procedure, showed two separate melting peaks in the ambient temperature range, which globally guarantee a melting enthalpy of about 50 kJ · kg−1, i.e. of the same order of magnitude of the first developed PCMs. Results from the life cycle analysis reveal that the expired palm oil can be considered a promising material for bio-based latent applications.Globally, the palm oil has proved itself as a promising, low cost, and environmentally friendly alternative for passive thermal storage solutions (e.g. building envelope applications) where stability across multiple thermal cycles, low health risks, and low leakage are crucial parameters to be addressed.

On the kinetics of Mn2O3/ZrO2 oxygen carrier for chemical looping air separation

Chemical looping air separation (CLAS) is a novel oxygen generation technology with relatively small energy penalty. Thereby, CLAS can be efficiently integrated with the oxy-fuel combustion and the integrated gasification combined cycle (IGCC) technologies. The Mn-based oxygen carrier (OC) is a promising candidate for the CLAS process in the OC family, but its reactivity and stability are still unclearly determined. In this work, the equilibrium oxygen partial pressure of the Mn2O3/Mn3O4 system is firstly calculated. Then the reactivity and the stability of the impregnated Mn2O3/ZrO2 and Mn2O3/Mg-ZrO2 are assessed via the thermogravimetric analysis. The redox cycles of both the two kinds of samples are found unstable at high temperatures. The performance of the Mn2O3/ZrO2 is found much better than that of the Mn2O3/Mg-ZrO2, so only the redox kinetics of the Mn2O3/ZrO2 sample is determined at 725–800 °C. The Avrami-Erofeev random nucleation and subsequence growth model (A2) and the phase boundary reaction model (R3) are found to be the most suitable reaction mechanisms for the reduction and the oxidation processes, respectively. Interestingly, the reaction order is detected to increase exponentially with temperature for the oxidation reaction. Furthermore, the apparent activation energy and the pre-exponential factor are obtained for the redox processes.

Thermodynamic and kinetics analysis of the sulfur-fixed roasting of antimony sulfide using ZnO as sulfur-fixing agent

Currently, the commercial antimony metallurgy is mainly based on pyrometallurgical processes and oxidative volatilization of Sb2S3 is an essential step. This step includes the problems of high energy consumption and low concentration of SO2 pollution. Aiming at these problems, we present a new method of sulfur-fixing roasting of antimony sulfide. This method uses ZnO as a sulfur-fixing agent, and roasting with Sb2S3 was carried out at 673 K~1073 K to produce Sb2O3 and ZnS. By calculating the thermodynamics of the reactions, we can conclude that the Gibbs Free Energy Change (?G?) of roasting reaction is below -60 kJ/mol and the predominance areas of Sb2O3 and ZnS are wide and right shifting with the temperature increase, which all indicates that this method is theoretically feasible. The reacted products between Sb2S3 and ZnO indicated that the reaction began at 773 K and finished approximately at 973K. We used the Ozawa-Flynn-Wall, Kissinger and Coats-Redfern method to calculate the kinetics of the roasting reaction. The conclusion is as follows: The average values of apparent activation energy (E) and natural logarithmic frequency factor (lnA) calculated by Ozawa-Flynn-Wall, Kissinger and Coats-Redfern were 189.72 kJ?mol-1 and 35.29 s-1, respectively. The mechanism of this reaction was phase boundary reaction model. The kinetic equation is shown as follow, where ? represents reaction fraction: 1-(1-?)1/3 = 2.12 x1015 exp(-1.90x105/RT) t.

The influence of polyoxymethylene molar mass on the oxidative thermal degradation of its nanocomposites with hydroxyapatite

In this paper, the influence of mass-average molar mass (M w) of polyoxymethylene (POM) copolymer on the thermooxidative degradation behavior of its nanocomposites with hydroxyapatite (HAp) is reported. POM copolymers’ thermal stability slightly decreases with a decrease in mass-average molar mass. Thermal stability of POM/HAp nanocomposites is lower in comparison with pure POM, and it gets lower with a decrease in mass-average molar mass of POM copolymer. For POM copolymer with the highest molar mass, thermal stability of POM/HAp nanocomposite was ca. 30 °C lower than for pure POM. To get a more in-depth insight into the decomposition process, kinetic analysis of POM/HAp nanocomposite thermal degradation process was performed using Friedman, Ozawa–Flynn–Wall and multiple nonlinear regression methods. The best fit for pristine T2, T3 and T4 copolymers with different molar mass of 100768, 74727 and 68377 g mol−1, respectively, was obtained for one-stage degradation mechanism with autocatalysis, while for T2/10 % HAp and T3/10 % it was parallel reaction model with autocatalysis (Bna) and phase-boundary reaction models (R3). For T4/10 % HAp, the best approximation was found for R2–Bna–D3 reaction model. From hyphenated TG–MS and TG–FTIR thermoanalytical studies, it was found that the main degradation product for POM/HAp nanocomposites is formaldehyde and the amount of other degradation products is lower in comparison with nonmodified POM copolymers.

Performance and kinetics of iron-based oxygen carriers reduced by carbon monoxide for chemical looping combustion

Chemical looping combustion is a promising technology for energy conversion due to its low-carbon, high-efficiency, and environmental-friendly feature. Avital issue for CLC process is the development of oxygen carrier, since it must have sufficient reactivity. The mechanism and kinetics of CO reduction on iron-based oxygen carriers namely pure Fe2O3 and Fe2O3 supported by alumina (Fe2O3/Al2O3) were investigated using thermo-gravimetric analysis. Fe2O3/Al2O3 showed better reactivity over bare Fe2O3 toward CO reduction. This was well supported by the observed higher rate constant for Fe2O3/Al2O3 over pure Fe2O3 with respective activation energy of 41.1±2.0 and 33.3±0.8 kJ∙mol–1. The proposed models were compared via statistical approach comprising Akaike information criterion with correction coupled with F-test. The phase-boundary reaction and diffusion control models approximated to 95% confidence level along with scanning electron microscopy results; revealed the promising reduction reactions of pure Fe2O3 and Fe2O3/Al2O3. The boosting recital of iron-based oxygen carrier support toward efficient chemical looping combustion could be explained accurately through the present study.

New logarithmic equation of temperature integral for modelling non-isothermal reactions

This article proposes a new logarithmic approximate formula of the Arrhenius temperature integral p(u) for non-isothermal analysis using the Solver algorithm. The proposed formula is presented as and the values for a, b and c are 0.69038, 1.71975 and 1.01249, respectively, for 0.45891, 1.85919 and 1.00275, respectively, for and 0.27341, 1.93235 and 1.00060, respectively, for The validity of the proposed Arrhenius temperature integral formula has been tested by investigating the thermal decomposition kinetics of acrylonitrile–butadiene–styrene (ABS). The activation energy and the pre-exponential factor determined by the proposed formula are 48.7385 kcal mol−1 and 2.6 × 1016 s−1, respectively. The reaction model of ABS thermal decomposition obtained with the method of master plots indicates that the phase boundary reaction model best describes the thermal decomposition reaction of ABS. The accuracy of the proposed Arrhenius temperature integral formula has also been tested by numerical analysis, and deviations from numerical values were compared with those of several previously published approximation formulae. The results show that the proposed formula is superior and is nearly ideal for estimating kinetic parameters from non-isothermal thermogravimetric data.

Non-isothermal kinetics of styrene—butadiene—styrene asphalt combustion

The combustion characteristics of styrene—butadiene—styrene (SBS) asphalt are studied by thermogravimetric analysis (TG/DTG) at four different heating rates. According to the saturates/aromatics/resins/asphaltenes (SARA) fractionation method, the combustion process of SBS asphalt can be divided by Gaussian peak fitting into three main stages: oil content release, resin pyrolysis, and asphaltene and char combustion. When the heating rate increases, the mass losses of the oil content and resin pyrolysis increase, and less asphaltenes are formed at a higher temperature. The activation energy values are calculated by the Coats—Redfern method to be in the range 61.6 kJ/mol–142.9 kJ/mol. The Popescu method is used for the kinetic analysis, and the result shows that the three stages of asphalt combustion can be explained by the sphere phase boundary reaction model, the second order chemical reaction model, nucleation, and its subsequent growth model, respectively.

Kinetics of CO2/Coal Gasification in Molten Blast Furnace Slag

The coal/CO2 gasification reactions in molten BF (blast furnace) slag were studied kinetically by temperature-programmed thermogravimetry using a thermal analyzer. The effect of heating rates and molten BF slag on coal gasification were studied, and the activation energies, frequency factors, and most possibility mechanism functions were calculated. The results show that the order of reactivity sequence at these temperatures was DT (Datong) coal > FX (Fuxin) coal > coke. With the increase in heating rate, the carbon conversion, and the peak value of reaction rate increased at the same reaction time, the carbon conversion curve shifts to a higher temperature and the reaction rate curve shifts rightward systematically, both of the time required for the carbon conversion to reach nearly unity and the time necessary for reaction rate to reach its maximum decreased. The carbon conversion and reaction rates were sensitive to BF slag; at the same time, the carbon conversion and reaction rates of coal gasification with slag are higher than those without slag. The time required for the carbon conversion to reach nearly unity and the time required for the reaction rate to reach maximum with slag are both shorter than that without slag. In the presence of BF slag, the carbon conversion curve shifts to lower temperature, the peak value of reaction rate is higher than that without slag, and the reaction rate curve also shifts to lower temperature. The molten BF slag acts as a good catalyst to coal gasification. Without molten BF slag, the mechanism functions of coke and FX coal are a C1 model (phase boundary reaction (n = 2) model), while the mechanism function of DT coal is a C2 model (phase boundary reaction (n = 3/2) model). However, with molten BF slag, the mechanism function of coke is a D5 model (3-D diffusion (anti-Jander) model), the mechanism function of DT coal is a D4 model (3-D diffusion model), and the mechanism function of FX coal is a C2 model (phase boundary reaction (n = 3/2) model). The activation energies and frequency factors decrease as heating rates increase. The kinetic compensation effect of coal/CO2 gasification in molten BF slag exists.

TG-DSC-FTIR Analysis of Cyanobacteria Pyrolysis

Pyrolysis of cyanobacteria from Dianchi lake was investigated by TG-DSC-FTIR analysis at different heating rates (10, 20, 40°C/min). The results indicated that the pyrolysis of cyanobacteria can be divided into four stages: evaporation, depolymerization, devolatilization and carbonization. Meanwhile, the initial weight-loss temperature, weight-loss extreme position, endothermic and exothermic peaks were moved to higher temperature with the increaseing of the heating rate. The kinetic analysis was made with Popescu method. It indicated that the best kinetic model for the pyrolysis of cyanobacteria was the cylindrical symmetry of the phase boundary reaction model. The main pyrolysis gases checked with real-time online FTIR were HCN, NH3, CO, CO2, water vapor and hydrocarbons.

Optimization of antigorite heat pre‐treatment via kinetic modeling of the dehydroxylation reaction for CO2 mineralization

AbstractThis contribution describes a predictive framework expedient to the thermal processing of serpentinites for the mineralization of CO2. We demonstrate the optimization of heat treatment of antigorite, providing a benchmark of an extreme case of activation among serpentine minerals. Antigorite was investigated non‐isothermally via thermogravimetry‐mass spectrometry and in situ X‐ray powder diffraction, its thermal reaction sequence elucidated, and reaction kinetics subsequently modeled. Based on the thermally induced structural changes, preferred content of residual hydroxyls in the dehydroxylated antigorite amounts to 10–40% of those present initially. This degree of dehydroxylation minimized the transformation of antigorite into new crystalline phases maximizing the amorphization of the new structure. The thermal reaction sequence provided both the explanation for the observed kinetic behavior and the basis for this optimization strategy. The optimal time for heat activation corresponds to ≤30 min, including the heat‐up period at a rate of 30 °C min–1 and an isothermal stage at 730 °C. This was successfully modeled using a three‐dimensional phase boundary reaction model (R3), with activation energy Ea of 160 kJ mol–1 and a frequency factor A of 5.7 ± 4.1 × 105 s–1 (5.7 × 105 s–1 for dynamic and 1.6 × 105 s–1 for static stage). This strategy translates to a fast and efficient thermal processing in an optimally sized calcining vessel. Furthermore, these results imply that activation of the more common serpentine minerals lizardite and chrysotile would be significantly faster as their dehydroxylation proceeds at lower temperatures than that of antigorite. © 2011 Society of Chemical Industry and John Wiley &amp; Sons, Ltd

Model-fitting and model-free analysis of thermal decomposition of palladium acetylacetonate [Pd(acac)2

The non-isothermal decomposition process of the powder sample of palladium acetylacetonate [Pd(acac)2] was investigated by thermogravimetric (TG) and the X-ray diffraction (XRD) techniques. Model-free isoconversional method of Tang, applied to the investigated decomposition process, yield practically constant apparent activation energy in the range of 0.05≤α≤0.95. It was established, that the Coats-Redfern (CR) method gives several statistically equivalent reaction models, but only for the phase-boundary reaction models (R2 and R3), the calculated value of the apparent activation energy (E) is nearest to the values of E obtained by the Tang’s and Kissinger’s methods.

Kinetic analysis of non-isothermal decomposition of dolomite in nitrogen atmosphere

In the present paper, a comparative study of five different non-isothermal kinetic analysis methods for the determination of the mechanism of the thermal decomposition of dolomite from thermogravimetric experiments, is presented. The experiments were carried out in a thermogravimetric analyser under a nitrogen atmosphere from 50 to 1100°C under non-isothermal conditions at five different heating rates, i.e. 5, 10, 20, 30 and 40 K min-1. By applying each of these methods, the kinetic parameters of the reaction were evaluated and the discrimination of the conversion function (kinetic model) that best verifies the experimental data was attempted. From a comparative study of the results of the above methods, it was concluded that the heating rate affects the activation energy values. For the model free methods, the activation energy was calculated at 242˙5 kJ mol-1 and the pre-exponential factor ln ( A, s-1 ) at 20˙6. The phase boundary reaction model of zero order was found to best represent dolomite decomposition.

Comparison between dehydration and desolvation kinetics of fluconazole monohydrate and fluconazole ethylacetate solvate using three different methods

It was of interest to study the dehydration and the desolvation of fluconazole monohydrate and ethyl acetate solvate respectively and also to determine the kinetics of dehydration and desolvation using thermogravimetry (TGA). Fluconazole monohydrate and ethyl acetate solvate were prepared by crystallization in water and in ethyl acetate solvent respectively. The dehydration and the desolvation processes were characterized by differential scanning calorimetry, thermogravimetry, powder X-ray diffractometry, and Fourier transform infrared spectroscopy. The weight changes of the fluconazole monohydrate and ethyl acetate solvate samples were monitored by isothermal TGA. Kinetic analyses of isothermal TGA data were done using model dependent and model independent methods. Various heating rates were also employed in different TGA samples, in order to apply the Ozawa method to determine the kinetic parameters. Eighteen solid-state reaction models were used to interpret the isothermal TGA experiments. Based on statistics, the three-dimensional phase boundary reaction model provided the best fit of the monohydrate data while the three-dimensional diffusion model provided the best fit for the ethyl acetate solvate data. The activation energy (Ea) values derived from rate constants of the aforementioned models were 90±11 and 153±11 kJ/mol for fluconazole monohydrate and ethyl acetate solvate respectively. Model independent analysis and the Ozawa method were also applied to the experimental results. Based on the results obtained from the model dependent, model independent and the Ozawa method, the mechanisms of the dehydration and the desolvation were determined.

An investigation of the pyrolysis kinetics of some aliphatic amino acids

The thermal behavior of some aliphatic amino acids, including alanine, valine, leucine, isoleucine, and proline was investigated by thermogravimetry (TG) in the range of temperatures within 30–400 °C. Pyrolysis of these amino acids was performed at various heating rates under inert (non-oxidative) conditions. The kinetic analysis was carried out using a composite procedure involving the iso-conversional method and the master plots method. The iso-conversional method indicated that the pyrolysis reaction should conform to single reaction model. The master plots method suggested that the phase boundary reaction models best describe the pyrolysis of alanine, valine, leucine and isoleucine, while the pyrolysis of proline should conform to the simple order reaction model. Also, for each amino acid, the kinetic parameters, such as activation energy and pre-exponential factor, were determined, respectively.