Master Plot Method Research Articles

Synthesis and isoconversional kinetic study of the formation of LiNiPO4 from Ni3(PO4)2·8H2O as a new precursor

The nanosized LiNiPO4 was successfully synthesized by a solid-state reaction between the new Ni3(PO4)2·8H2O precursor and Li3PO4 at 700 °C in air atmosphere. The formation of LiNiPO4 was generated via three thermal decomposition steps. The samples were characterized by Fourier transform infrared, X-ray diffraction, scanning electron microscopy, atomic absorption/atomic emission spectrophotometers, and thermogravimetric/differential thermal gravimetric/differential thermal analysis techniques. The activation energy (Eα) values of the three steps were calculated by Vyazovkin method and determined to be 90.39 ± 5.79, 197.81 ± 7.46, and 308.66 ± 12.03 kJ mol−1, respectively. The average Eα values from this method are very close to Eα from KAS method. The most probable mechanism functions g(α) of three steps were evaluated by using the masterplots method and found to be the F1/3 (first step), F3/2 (second step), and D4 (final step), respectively. The pre-exponential factors (A) values of three steps were obtained based on the Eα and g(α). The kinetic triplet parameters of the formation of LiNiPO4 from the new precursor are reported in the first time.

(Fe0.9Ni0.1)77Mo5P9C7.5B1.5 bulk metallic glass matrix composite produced by partial crystallization: The non-isothermal kinetic analysis

In this study, the non-isothermal kinetic analysis of partial crystallization process in (Fe0.9Ni0.1)77Mo5P9C7.5B1.5 BMG was investigated. The XRD and FE-SEM results revealed that five nano-crystalline phases including (Fe,Ni)3P, Ni3Fe, Fe3C, α-Fe, and γ-Fe were formed during crystallization process. Also, the DTA curves showed that crystallization process in this BMG occurred at various stages. The kinetic parameters for various stages of crystallization process were determined by isoconversional Starink and Friedman (FR) methods in combination with the invariant kinetic parameters (IKP) and the g(α) master plot methods. According to isoconversional and fitting methods, it was observed that crystallization process in this BMG was controlled by activation energies equal to 170–280 kJ/mol and Avrami–Erofeev and power law models.

Thermal decomposition and kinetics of coal and fermented cornstalk using thermogravimetric analysis

The thermal behavior and kinetics of Yiluo coal (YC) and the residues of fermented cornstalk (FC) were investigated in this study. The Kissinger-Akahira-Sunose (KAS) and Flynn-Wall-Ozawa (FWO) methods were used for the kinetic analysis of the pyrolysis process. The results showed that the activation energy (Eα) was increased with the increase of the thermal conversion rate (α), and the average values of Eα of YC, FC and the blend (mYC/mFC = 6/4) were 304.26, 224.94 and 233.46 kJ/mol, respectively. The order reaction model function for the blend was also developed by the master-plots method. By comparing the Ea and the enthalpy, it was found that the blend was favored to format activated complex due to the lower potential energy barrier. Meanwhile, the average value of Gibbs free energy of the blend was 169.83 kJ/mol, and the changes of entropies indicated that the pyrolysis process was evolved from ordered-state to disordered-state.

Characterization of Powder River Basin coal pyrolysis with cost-effective and environmentally-friendly composite Na[sbnd]Fe catalysts in a thermogravimetric analyzer and a fixed-bed reactor

The pyrolysis characteristics of PRB coal with use of NaFe composite catalysts were investigated in a thermogravimetric analyzer and a fixed bed reactor. Model-free methods developed by Friedman (FR), Kissinger-Akahira-Sunose (KAS), Flynn-Wall-Ozawa (FWO) and Vyazovkin (VA) were compared and applied to determine the pyrolysis kinetic parameters. A Master-plot method was used to determine the reaction order and pre-exponential factors. Raw coal with the addition of 4% FeCO3 achieved the highest effect on coal conversion; specifically, 4% Na2CO3 and 1% Na2CO3–3% FeCO3 showed higher effect than 3% Na2CO3–1% FeCO3 and 2% Na2CO3–2% FeCO3. The averaged E values of raw coal with 4% FeCO3 catalyst decreased by 10% compared with that of raw coal. Compared with the individual use of 4% Na2CO3, the addition of FeCO3 can be effective in decreasing the E values of the raw coal. The nonlinear VA method appears to be superior in determining activation energies of coal pyrolysis at considered conversion range. Further, the An (random nucleation and nuclei growth model) appears to be the appropriate reaction model for raw coal pyrolysis with and without the use of NaFe composite catalysts. From the pyrolysis in the fixed bed reactor, XRD and FTIR tests for coal chars produced by PRB coal pyrolysis with use of catalysts were conducted. By combining the gas evolution and XRD/FTIR results, a reaction mechanism is proposed for coal pyrolysis with composite Na2CO3FeCO3 catalysts.

Kinetics of perovskite-like oxygen carriers for chemical looping air separation

Chemical looping air separation gives an energy-efficient choice for oxygen production. We performed kinetic analysis of YBaCo4O7+δ, Y0.95Ti0.05BaCo4O7+δ, Y0.2Ti0.05Dy0.75BaCo4O7+δ, and Y0.15Zr0.1Dy0.75BaCo4O7+δ oxygen carriers in a CLAS process. TG experiments were conducted with heating rates of 0.5, 1, and 2 °C/min in a thermogravimetric analyzer. Further exploration is required to develop an appropriate oxygen carrier. So, we used the model-free approach, Starink method, to evaluate the apparent activation energy. And, masterplots method was applied to determine the most probable mechanism function. The results show that the distributed activation energies of oxidation/reduction process are 189.42/286.22 kJ/mol, 197.70/324.87 kJ/mol, 195.41/310.4 kJ/mol, and 192.20/293.53 kJ/mol for YBaCo4O7+δ, Y0.95Ti0.05BaCo4O7+δ, Y0.2Ti0.05Dy0.75BaCo4O7+δ, and Y0.15Zr0.1Dy0.75BaCo4O7+δ oxygen carriers, respectively. Random nucleation and nuclei growth A model is the most suitable for oxidation process. The A model and D are the most suitable for the reduction process. Regarding YBaCo4O7+δ, Y0.95Ti0.05BaCo4O7+δ, Y0.2Ti0.05Dy0.75BaCo4O7+δ, and Y0.15Zr0.1Dy0.75BaCo4O7+δ kinetic, oxygen transfer materials are rate-determined by nucleation and nuclei growth. For reduction kinetic, the gas diffusion stage could also become a dominant step.

Pyrolytic behavior of waste extruded polystyrene and rigid polyurethane by multi kinetics methods and Py-GC/MS

The utilization of polymer wastes for volatile fuel production has been considered as a sustainable and environmental-friendly approach for achieving better waste management, pollution protection, and renewable energy security. Polymer pyrolysis, as an ideal method for polymer waste converted into storable fuel, was explored thoroughly in this study from pyrolysis kinetics to evolved gas analysis. Two typical building-used polymer wastes, extruded polystyrene (XPS) and rigid polyurethane (RPU), were selected to conduct a series of thermogravimetry (TG) experiments. Then commonly-used isoconversional methods were employed to calculate the kinetic parameters of the pyrolysis during the whole conversion. Kinetic models of XPS and RPU thermal degradations were identified from nineteen reaction models by Coats-Redfern and masterplots methods. Then accommodation function was employed to adjust the theoretical model for reconstruction. Considering the complexities of RPU component and degradation process, Py-GC/MS was used to identify the volatile product component at 250, 340, and 460 °C, respectively. Results showed that there are large parts of volatile alcohols and ethers escaped during RPU pyrolysis process. The results of this study have implications concerning kinetic triplet determination method and escaped gas analysis during polymer waste pyrolysis process.

Kinetic Analysis of Nonisothermal Decomposition of Acetyl Ferrocene

ABSTRACTThe work deals with thermal decomposition of acetyl ferrocene in nitrogen atmosphere based on nonisothermal thermogravimetry. It presents a mathematical analysis of nonisothermal thermogravimetric data using multiheating rates to estimate reaction kinetic parameters. Model free (integral isoconversional) methods are employed to analyze the thermogravimetric data. The decomposition is a multistep process. The activation energy Eα of decomposition is conversion (α) dependent. The average values of activation energy are Eα = 49.87, 106.28, and 183.35 kJ mol−1 for three major steps of decomposition. The most probable reaction mechanism function, g(α), for thermal reactions has been identified by the master plot method, and the stepwise reaction mechanisms are found to be different for different steps. The estimated values of the activation energy Eα and g(α) have been utilized in the determination of the reaction rate Aα of thermal decomposition. The α‐dependent reaction rate values are determined and are found to lie in the range of 5.2 × 105 to 3.2 × 104 min−1, 1.7 × 1015 to 7.8 × 106 min−1, and 3.8 × 108 to 1.4 × 107 min−1 for three different steps. Based on the values of Eα, g(α), and Aα, the thermodynamic triplets (ΔS, ΔH, ΔG) associated with the decomposition reactions have been estimated. Estimated kinetic parameters have been used to construct the conversion curves, and those have been successfully compared with the experimentally observed ones.

Determination of the Self-Heating Temperature of Coal by Means of TGA Analysis

In this study, the self-heating tendency of Tavsanli (Turkey) coal was investigated by the apparatus of thermal analysis. TG-DTG and DSC-DDSC plots obtained at air atmosphere from 25 to 800 °C were used to determine the self-heating temperature (Tsh) and the combustion behavior of coal. The self-heating temperature changes versus the particle sizes of coal and heating rates were examined . Also, kinetic parameters of the main combustion region were obtained in the temperature range of 25 to 800 °C at different heating rates (1, 2.5, 5, and 10 °C min–1) under nonisothermal heating conditions at air atmosphere. The activation energy, pre-exponential factor, and reaction mechanism were calculated by using KAS, FWO, Coats–Redfern, and Master-Plot methods. It was understood that the oxidation process of coal was controlled by the first order [F1: −ln (1 – α)] mechanism.

Revealing low temperature microwave‐assisted pyrolysis kinetic behaviors and dielectric properties of biomass components

The kinetic characteristics of microwave‐assisted pyrolysis (MAP) of biomass components were investigated in a self‐designed microwave thermogravimetric analysis using the KAS model and the master plot method. Compared with conventional pyrolysis, the initial decomposition temperatures of biomass components were reduced by 50–100°C and the fastest weight loss regions were shifted to lower temperatures. The average apparent activation energies of cellulose, hemicellulose, and lignin were 47.82, 44.81, and 51.54 kJ/mol, respectively. Analysis with master plot method suggested the MAP of cellulose followed the 2‐D diffusion reaction model, while hemicellulose and lignin could be interpreted by third order‐based and 3‐D diffusion model. The change of dielectric properties was consistent with the weight loss behaviors of biomass components during the pyrolysis process. The increase of dielectric properties with temperature can lead to a thermal gradient and “hot spots” within biomass, which accelerated the pyrolysis process at low temperatures and reduced the apparent activation energy. © 2018 American Institute of Chemical Engineers AIChE J, 64: 2124–2134, 2018

Thermal kinetics study and flammability evaluation of polyimide fiber material

The thermal stability and flammability of polyimide (PI) fiber for fire protection applications have been assessed by dynamic thermogravimetry and microscale combustion calorimetry (MCC) measurements, respectively. The polymer decomposed in a single step and main pyrolysis occurs within a very narrow temperature range. The kinetic analysis of the main pyrolysis process was conducted by a composite procedure involving the iso-conversional method and the Master-plots method. The main process reaction mechanism of the polyimide obeyed random nucleation model with three nuclei on the individual particle. Compared with polysulfonamide fiber and Meta-aramid (NOMEX 1313) inherently heat-resistant fiber, flammability evaluation from LOI values and MCC data indicated that PI fiber exhibited lower flammability in terms of the ability to ignite and higher flammability in terms of the heat release capacity during combustion. This analysis for kinetics of the PI fiber is useful information for further study of numerical simulation of pyrolysis process of PI fabric when exposed to intense heat flux.

A Kinetic Investigation into the In Situ Combustion Reactions of Iranian Heavy Oil from Kuh-E-Mond Reservoir

An efficient design of in situ combustion depends on accurate kinetic modeling of the crude oil oxidation. The kinetic triplet of the oxidation reactions of a heavy oil sample was investigated. Once the kinetic triplet is known, the kinetic equation would be deconvolved. The crude oil sample was obtained from Kuh-E-Mond reservoir, located in the southwest of Iran. The samples were analyzed using differential scanning calorimetry (DSC) at atmospheric pressure, in a temperature range of 297- 973 K, and at four different heating rates. Three isoconversional kinetic models were used to obtain a variation of Arrhenius parameters during the course of the high temperature oxidation reaction. The activation energy (Eα) and the pre-exponential factor (A) were obtained at different conversions. Having Arrhenius parameters, the conversion function, f(α), was estimated using an advanced master plot method. It was observed that f(α) follows the Avrami–Erofeev (An) model with n=3. Furthermore, the parameters of truncated Sestak–Berggren (SB) reaction model were obtained. SB fits fairly better than A3 to the experimental data. According to the results, a change in the heating rate does not considerably vary the reaction model.

Estimation of the kinetic triplet for in-situ combustion of crude oil in the presence of limestone matrix

Efficient design of in-situ combustion depends on accurate kinetic modeling of the crude oil oxidation. Kinetic triplet of the crude oil combustion was obtained and effect of the limestone matrix on kinetic triplet was investigated. Once the kinetic triplet is known, the basic kinetic equation would be deconvolved. Crude oil Samples (both pure and mixed with limestone) were analyzed using Differential Scanning Calorimetry (DSC) under atmospheric pressure at 297K–973K in four different heating rates. Three isoconversional kinetic models were used to obtain a variation of Arrhenius parameters during the course of the reaction. The presence of the limestone decreased activation energy (Eα) probably due to increased surface area. Moreover, both values and standard deviation of the preexponential factor (A) would be decreased due to the presence of limestone. Having Arrhenius parameters, the conversion function, f(α), was estimated using an advanced master plot method. It was observed that f(α) follows the Avrami–Erofeev (An) model with n=3. Furthermore, parameters of truncated Sestak–Berggren (SB) reaction model were obtained. It was shown that the SB was slightly better than A3 in fitting the experimental data. According to the results, neither change of heating rates nor addition of limestone caused a considerable change of the reaction model; HTO region in each case follows A3 model.

Thermal dehydration of colemanite: kinetics and mechanism determined using the master plots method

ABSTRACTDehydration kinetics of colemanite ore were explored using thermogravimetric analysis techniques (thermogravimetry (TG)/derivative thermogravimetry (DTG)) in the range of 0–1000°C at heating rates of 2, 5, 10 and 20°C min−1 in an inert (N2) atmosphere. Kinetic triplets which were activation energy, pre-exponential factor and reaction mechanism were obtained from the TG and DTG applying six model-free (isoconversional) methods, i.e. Kissinger–Akahira–Sunose (KAS); Flyn–Wall–Ozawa (FWO); Tang, Starink and iterative KAS and iterative FWO. The researcher tested the reliability of the study method in identifying the kinetic mechanism by comparing experimental master plots to theoretical master plots. Structural and morphological properties were carried out using X-ray diffraction, Fourier transform infrared and scanning electron microscopy-energy disperse spectroscopy methodologies.

Combustion characteristics and kinetics of anthracite with added chlorine

The combustion process of Yangquan anthracite (YQ) with the addition of 0.045wt%, 0.211wt%, 1.026wt%, and 2.982wt% chlorine was investigated using a thermogravimetric method from an ambient temperature to 1173 K in an air atmosphere. Results show that the YQ combustion characteristics are not significantly affected by an increase in chlorine content. Data acquired for combustion conversion are then further processed for kinetic analysis. Average apparent activation energies determined using the model-free method (specifically the KAS method) are 103.025, 110.250, 99.906, and 110.641 kJ/mol, respectively, and the optimal kinetic model for describing the combustion process of chlorine-containing YQ is the nucleation kinetic model, as determined by the z(α) master plot method. The mechanism function of the nucleation kinetic model is then employed to estimate the pre-exponential factor, by making use of the compensation effect. The kinetic models to describe chlorine-containing YQ combustion are thus obtained through advanced determination of the optimal mechanism function, average apparent activation energy, and the pre-exponential factor.

Synthesis and characterization of methacrylamide-acrylic acid-N-isopropylacrylamide polymeric hydrogel: degradation kinetics and rheological studies

Methacrylamide-acrylic acid-N-isopropylacrylamide terpolymeric hydrogels have been prepared via free radical polymerization using diammonium-peroxo-disulphate initiator system and ethylene glycol-di-methacrylate as a cross-linker. The hydrogels were characterized by Fourier transform infrared spectroscopy, field emission scanning electron microscopy, thermogravimetric analysis, and differential scanning calorimetry. Molar mass was determined by viscometric method. Rheological profiling of the hydrogels was carried out by rheological measurements at various temperatures and methacrylamide contents in hydrogels. Thermogravimetric data were analyzed to assess the kinetic triplet by iso-conversional method. The values of apparent activation energy (E a) figured out from TG data were measured for each step by Kissinger–Akahira–Sunose method. On the findings of results, the decomposition reaction of terpolymeric hydrogels has been analyzed as a slow reaction, which is evident from the low-frequency factor values (A), i.e., 3 × 106, 2 × 1010, and 4 × 1015 s−1, respectively. The master plot method was used to predict the mechanism for degradation of MANIPAM-7. Flow curve and frequency sweep tests at different temperatures showed temperature dependency with shear rate indicating the pseudo-plastic nature of the synthesized samples. The rheological parameters were analyzed using various models. Out of these methods, the Ostwald, modified Bingham, and Herschel–Bulkley models were established to provide better fit to experimental data. Dynamic moduli measured as a function of angular frequency showed viscoelastic nature of all the samples. Frequency sweep studies indicated that storage (G′) and loss modulus (G″) showed an increase with increasing concentration of methacrylamide. Composition dependency of crossover frequency directed an increase in relaxation time with methacrylamide contents in the hydrogel.

Pyrolysis reaction models of waste tires: Application of Master-Plots method for energy conversion via devolatilization

Land applied disposal of waste tires has far-reaching environmental, economic, and human health consequences. Pyrolysis represents a potential waste management solution, whereby the solid carbonaceous residue is heated in the absence of oxygen to produce liquid and gaseous fuels, and a solid char. The design of an efficient conversion unit requires information on the reaction kinetics of pyrolysis. This work is the first to probe the appropriate reaction model of waste tire pyrolysis. The average activation energy of pyrolysis was determined via iso-conversional methods over a mass fraction conversion range between 0.20 and 0.80 to be 162.8±23.2kJmol−1. Using the Master Plots method, a reaction order of three was found to be the most suitable model to describe the pyrolytic decomposition. This suggests that the chemical reactions themselves (cracking, depolymerization, etc.), not diffusion or boundary layer interactions common with carbonaceous biomasses, are the rate-limiting steps in the pyrolytic decomposition of waste tires.

Comparison of kinetic analysis methods in thermal decomposition of cattle manure by themogravimetric analysis

The thermogravimetric (TG) experiments of cattle manure were carried out from room temperature to 900°C at five different heating rates (10, 20, 30, 40 and 50°C/min) and the kinetics of the main decomposition process were analyzed with different methods. TG curves indicate that the major decomposition process of cattle manure could be roughly divided into three stages. The average activation energy of each stage calculated by Coats-Redfern method are 68.95, 2.63 and 55.32kJ/mol respectively. The kinetic parameters given by Distributed Activation Energy Model method, Flynn-Wall-Ozawa method and Vyazovkin method are all show that the activation energies keep stable (at around 122.4, 126 and 123.8kJ/mol respectively) under 60% conversion degree and then changed dramatically (ranging from 129.9 to 454.9kJ/mol). Power law (P3) was determined as an appropriate reaction mechanism using master-plots method. The kinetic parameters calculated by Vyazovkin method can give the best agreement with the experimental results.

Evaluation of agricultural residues pyrolysis under non-isothermal conditions: Thermal behaviors, kinetics, and thermodynamics

The thermal conversion characteristics, kinetics, and thermodynamics of agricultural residues, rape straw (RS) and wheat bran (WB), were investigated under non-isothermal conditions. TGA experiments showed that the pyrolysis characteristics of RS were quite different from those of WB. As reflected by the comprehensive devolatilization index, when the heating rate increased from 10 to 30Kmin−1, the pyrolysis performance of RS and WB were improved 5.27 and 5.96 times, respectively. The kinetic triplets of the main pyrolysis process of agricultural residues were calculated by the Starink method and the integral master-plots method. Kinetic analysis results indicated that the most potential kinetic models for the pyrolysis of RS and WB were D2 and F2.7, respectively. The thermodynamic parameters (ΔH, ΔG, and ΔS) were determined by the activated complex theory. The positive ΔH, positive ΔG, and negative ΔS at characteristic temperatures validated that the pyrolysis of agricultural residues was endothermic and non-spontaneous.

Thermal decomposition of rape straw: Pyrolysis modeling and kinetic study via particle swarm optimization

The aim of this work is to implement an efficient and robust optimization approach for parameter estimation of pyrolysis kinetic model to study the pyrolysis of a typical agricultural residue. Thermogravimetric profiles of rape straw were obtained at a wide heating range of 10, 20, 30 and 40°C/min in an inert atmosphere of nitrogen and the thermal decomposition process was studied in detail. First, three different kinetic methods (Friedman, KAS and OFW) were applied for activation energy determination. The activation energies ranged from 191.16kJ/mol to 264.31kJ/mol. Then, the reaction mechanism and pre-exponential factor were analyzed by using the generalized master-plots method. It is found that at conversion level higher than 0.4 the rape straw decomposition was governed by 3-D diffusion model and it tended to high order reaction model at lower conversion. Finally, a multi-component parallel reactions scheme incorporated into the Particle Swarm Optimization (PSO) technique was presented to determine kinetic parameters. The kinetic triplets and other stoichiometric parameters were optimized against profiles for heating rates of 20 and 30°C/min. The optimized activation energy value is 156.41kJ/mol, 211.26kJ/mol and 57.84kJ/mol for hemicellulose, cellulose and lignin, respectively. These results are in conformity with results reported in previous literatures. Meanwhile, the obtained pre-exponential factors values also lie in the reasonable range of lnAi=25.32–39.14ln/s according to intrinsic transition-state theory. Furthermore, cross-validated results show that the optimized parameters can be applied not only to conditions where they were obtained, but also to conditions beyond (10 and 40°C/min), indicating that the derived results are appropriate to simulate and predict rape straw pyrolysis under various heating rates, which will be useful for further design and sizing of biomass thermochemical process reactors.

Pyrolysis Kinetics and Emission Characteristics of Waste Disposable Paper Cups Using the Thermogravimetric-FTIR Technique

The pyrolysis of waste disposable paper cups (WDPCs) was investigated using a thermogravimetric analyser coupled with a Fourier transform infrared spectrometer. The activation energies of the pyrolysis reactions were obtained by the Flynn–Wall–Ozawa (FWO) and Kissinger–Akahira–Sunose (KAS) methods respectively. The kinetic model was determined by the master plots method. Thermogravimetric results showed that the highest weight loss rate occurred from 345 to 365 °C as the heating rate was increased from 10 to 30 °C min−1, indicating the pyrolysis of cellulosic material in the WDPC. The weight loss between 400 and 500 °C can be attributed to the decomposition of polyethylene. By analysing the FTIR spectra, it was found that the absorbance of all the evolved gaseous products had peaks at 360 °C due to the decomposition of cellulose fibres and the cracking of polyethylene at 485 °C led to the emergence of a second hydrocarbon peak. Ketones were the most abundant condensable organic products and CO2 was the dominating gaseous product, which can also be produced via secondary cracking of the small molecule organics above 400 °C. Kinetic analysis revealed that the average activation energy of the pyrolysis of the WDPC was 153.75 kJ mol−1 from the FWO method and 151.43 kJ mol−1 from the KAS method. The reaction mechanism can be described by the R3 model.