Correlations of kinetic parameters in biomass pyrolysis with solid residue yield and lignin content

A kinetic analysis of the pyrolysis of various types of biomass (trunk, bark, leaf, shell, herbage, food dregs, and polysaccharide) as well as synthetic biomass consisting of cellulose and lignin was performed using thermogravimetric analysis data. The reaction rates of biomass pyrolysis were found to be expressed simply by a single nth-order reaction model. The kinetic parameters (frequency factor k₀, activation energy E, and reaction order n) were estimated first by differentiating the thermogravimetric curves and then by the nonlinear estimation method. The rate parameters of the pyrolysis of both 38 biomass samples and 9 synthetic biomass samples were successfully correlated in terms of the solid residue yield ω; charts are presented showing the correlations. Furthermore, a linear correlation was found between ω and the lignin content L in the woody biomass. This allows the kinetic parameters of biomass pyrolysis to be estimated using the value of ω, which is obtained from thermogravimetric measurements or estimated from the value of L for the biomass feedstock.     

Thermal decomposition behavior of oligo(4‐hydroxyquinoline)

In this study, the kinetic parameters and reaction mechanism of decomposition process of oligo(4‐hydroxyquinoline) synthesized by oxidative polymerization were investigated by thermogravimetric analysis (TGA) at different heating rates. TGA‐derivative thermogravimetric analysis curves showed that the thermal decomposition occurred in two stages. The methods based on multiple heating rates such as Kissinger, Kim–Park, Tang, Flynn–Wall–Ozawa method (FWO), Friedman, and Kissinger–Akahira–Sunose (KAS) were used to calculate the kinetic parameters related to each decomposition stage of oligo(4‐hydroxyquinoline). The activation energies obtained by Kissinger, Kim–Park, Tang, KAS, FWO, and Friedman methods were found to be 153.80, 153.89, 153.06, 152.62, 151.25, and 157.14 kJ mol^?1 for the dehydration stage, 124.7, 124.71, 126.14, 123.75, 126.19, and 124.05 kJ mol^?1 for the thermal decomposition stage, respectively, in the conversion range studied. The decomposition mechanism and pre‐exponential factor of each decomposition stage were also determined using Coats–Redfern, van Krevelen, Horowitz–Metzger methods, and master plots. The analysis of the master plots and methods based on single heating rate showed that the mechanisms of dehydration and decomposition stage of oligo(4‐hydroxyquinoline) were best described by kinetic equations of A_n mechanism (nucleation and growth, n = 1) and D_n mechanism (dimensional diffusion, n = 6), respectively. POLYM. ENG. SCI., 54:992–1002, 2014. © 2013 Society of Plastics Engineers     

Predicting thermal degradation kinetics of nylon6/feather keratin blends using artificial intelligence techniques

A multi-structured architecture of artificial intelligence techniques including artificial neural network (ANN), adaptive-neuro-fuzzy-interference system (ANFIS) and radial basis function (RBF) were developed to predict thermal degradation kinetics (TDK) of nylon6 (NY6)/feather keratin (FK) blend films. By simultaneous implementation of back-propagation ANN and feed-forward ANFIS modeling on the experimental data obtained from thermogravimetric analysis (TGA) method, thermal degradation behavior of various compositions of NY6/FK blends was successfully predicted with minimum mean square errors (MSE). RBF networks were then trained on the TGA data at one heating rate for predicting analogs information at different heating rates, providing sufficient feed for TDK modeling. According to the comparison made between experimental and predicted kinetic parameters of thermal degradation process calculated from Friedman and Kissinger methods, the proposed prediction effort could effectively contribute to the estimation of precise activation energy (E_a) and reaction order (n) values with least amount of experimental work and most accuracy.     

Study of pyrolysis kinetics of oil shale

The pyrolysis experiments on oil shale samples from Fushun, Maoming, Huangxian, China, and Colorado, USA, were carried out with the aid of thermogravimetric analyzer (TGA) at a constant heating rate of 5 °C/min. A kinetic model was developed which assumes several parallel first-order reactions with changed activation energies and frequency factors to describe the oil shale pyrolysis. The kinetic parameters of oil shale pyrolysis were determined on the basis of TGA data. The relationship between the kinetic parameters was further investigated and the correlation equations of x_∞-E and ln A-E were obtained. These equations show that the final fractional conversion of each parallel reaction, x_∞(j), can be expressed as an exponential function of the corresponding activation energy. The plot of ln A-E for different reactions becomes a straight line. These relationship equations can provide important information to understand the pyrolysis mechanism and to investigate the chemical structure of oil shale kerogen.     

Thermal pyrolysis and kinetic analysis of a ZnxCo1−x ZiF-8 metal–organic framework for recent applications

Zeolitic imidazolate frameworks (ZIFs) are interesting materials for use in several aspects: energy storage material, gas sensing, and photocatalysis. The thermal stability and pyrolysis process are crucial to determine the active phase of the material. A deep understanding of the pyrolysis mechanism is in demand. So, the thermodynamics and combustion process with different heating rates were examined, and the kinetic parameters were computed employing thermogravimetric tests. Based on the TG analysis of combustion, pyrolysis moves to the high-temperature region with an increase in heating rate. The decomposition process can be separated into dehydration (300–503 K) and pyrolysis reaction (703–1100 K). Three points of the decomposition process are performed by dynamical analysis owing to shifts of slopes, but the combustion process has only one stage. Dynamical parameters, for instance, the possible mechanism, the pre-exponential factor, and the apparent activation energy were obtained through comparison using the Kissinger formula. The thermodynamics analysis of the Zn_1?xCo_x ZIF-8 materials is an effective way to explore the temperature influence on the process of pyrolysis, which can benefit in several recent applications.

     

Analysis of pyrolysis and gasification reactions of hydrothermally and supercritically upgraded low-rank coal by using a new distributed activation energy model

Hydrothermal water treatments and supercritical (SC) water treatments of a lignite were performed to examine the feasibility of upgrading low-rank coals. The treatment below 400°C was found to be effective enough to keep high gasification reactivity at high temperature, as well as to suppress spontaneous combustion. The pyrolysis and gasification behaviors of raw and pretreated coals were examined by thermogravimetry (TG). The kinetic analysis was carried out based on a new distributed activation energy model (DAEM) presented by Miura [K. Miura, Energy & Fuels, (12), 864–869 (1998).]. According to this method, thermogravimetric curves measured at two or more different heating rates were needed to obtain the activation energy distribution function f(E) of a given coal sample. It was found that in the case of pyrolysis, the peak values of f(E) curves for upgraded coal samples are nearly 300 kJ/mol, whereas, the peak value of f(E) curve for their parent coal is about 200 kJ/mol. In the case of gasification, where only single reactions occur, the application of this new DAEM can give the changes of activation energy during reaction. Some interesting results occur, which may hint at some changes in the rate-controlling step of reaction or in the physical structure of coal during gasification.     

An algorithm for determining the kinetics of devolatilisation of complex solid fuels from thermogravimetric experiments

An algorithm is introduced for determining the kinetics of devolatilisation of complex fuels, e.g. coal or biomass, when heated in an inert atmosphere. The algorithm uses information from thermogravimetric experiments, at several different, but constant, rates of heating, to identify and characterise the underlying distribution of reactions governing devolatilisation. The algorithm also provides an approximate way of inverting the distributed activation energy model (DAEM), commonly used to model the pyrolysis of coal. Such techniques provide the activation energy, E, and pre-exponential factor, A, for each parallel step participating in the thermal decomposition of a solid fuel. In addition, the amount of material associated with each pair of A and E can be derived.The method is tested on (i) imaginary data from simulated TGA experiments with one or more first-order reactions and (ii) real data from thermogravimetric experiments on the pyrolysis of sewage sludge. In every case the algorithm gave excellent predictions for heating rates other than those at which the pair of E and A were derived. Thus, the algorithm is a useful method of analysing and summarising measurements to provide kinetic data and facilitate predictions.     

On the thermal degradation of poly(styrene sulfones). VII. Evaluations of poly(styrene sulfone) thermal stability using invariant kinetic parameters

The thermal degradation behavior of poly(styrene sulfone) was investigated by thermogravimetric analysis (TGA) measurement. This study described its thermal stability by applying the invariant kinetic parameter (IKP) method. The thermogravimetric and differential thermogravimetric analyses of different compositions of poly(styrene sulfones) were carried out over the temperature range 100–500°C under nitrogen. The kinetic parameters (preexponential factor and activation energy) of thermal decomposition of poly(styrene sulfone) can be obtained by dynamic measurement of TGA. The IKP method assumes that the kinetic parameters are independent of the experimental conditions. These parameters are computed without any hypothesis on the form of the kinetic degradation function. Invariant activation energies of the degradation of poly(styrene sulfone) show that the thermal stability decreases as the SO₂ content of poly(styrene sulfone) increases due to the thermal instability of the C? S bond. The relation equation, Ea_inv = 237.0 ? 290.5X_SO2, where X_SO2 is the molecular fraction of SO₂, was obtained to describe the effect of sulfur dioxide on the thermal stability of poly(styrene sulfone). © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 1698–1705, 2002     

Kinetics of thermal degradation studies of some new terpolymers derived from 2,4‐dihydroxypropiophenone,oxamide, and formaldehyde

The terpolymers (2,4‐DHPOF) have been synthesized by the condensation of 2,4‐dihydroxypropiophenone with oxamide and formaldehyde in the presence of 2M HCl as catalyst with varying proportions of reactants. Terpolymer composition has been determined on the basis of their elemental analysis. The terpolymer has been characterized by UV‐visible, IR, and ¹H NMR spectra. The thermal decomposition behavior of some new terpolymers was studied using thermogravimetric analysis in air atmosphere at heating rate of 10°C/min. Thermal decomposition curves are discussed with careful attention to minute details. The Freeman–Carroll and Sharp–Wentworth methods have been used to calculate activation energy and thermal stability. Thermal activation energy (E_a) calculated with the help of these methods are in agreement with each other. Thermodynamic parameters such as free energy change (ΔF), entropy change (ΔS), apparent entropy change (S*), and frequency factor (z) are also determined on the basis of the TG curves and by using data of the Freeman–Carroll method. The Freidman method evaluated the variation in the apparent activation energy changes by isoconversional (model‐free) kinetic methods. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Thermogravimetric characteristics of <Emphasis Type="Italic">α</Emphasis>-cellulose and decomposition kinetics in a micro-tubing reactor

The pyrolysis characteristics and kinetics of α-cellulose were investigated using thermogravimetric analyzer (TGA) and micro tubing reactor, respectively. Most of the α-cellulose decomposed between 250 and 400 °C at heating rate of 5–20 °C/min. The apparent activation energy was observed in the range of 263.02 kJ mol^?1 to 306.21 kJ mol^?1 at the conversion of 10-80%. The kinetic parameters were determined by nonlinear least-squares regression of the experimental data, assuming first-order kinetics. It was found from the kinetic rate constants that the predominant reaction pathway was A(α-cellulose) to B(bio-oil) rather than A(α-cellulose) to C(gas; C₁-C₄) and/or to B(bio-oil) to C(gas; C₁-C₄) at temperatures of 340-360 °C.     

Cinétique de la calcination du coke de pétrole en atmosphères neutre et oxydante

A devolatilization kinetic study of oil coke samples under conditions close to those of industrial calcination furnace is presented. The effects of the surrounding conditions (neutral or oxydizing medium), the heating rate and the percentage of oxygen in an oxydizing environment are analyzed. Experiments are carried out in an induction oven and involved thermogravimetric and chromatographic analyses. Results show that, under certain conditions, the nature of the environment influence the devolatilization process. A slow heating rate and a low content in volatiles promote the coke degradation by oxygen in an oxydizing medium. The reactive schemes are derived by tracking the concentration of CH₄, H₂, CO and CO₂. In regions where the coke is not degraded, a kinetic model is used to compare the parameters describing the develotilization phenomena in the two media (neutral and oxydizing), i.e.: the reaction order, the activation energy and the pre-exponential factor. It is shown that the oxydizing medium promotes an increase in the activation energy.     

High‐resolution thermogravimetry/coupled mass spectrometry analysis of flame‐retardant rubber

A bromobutyl rubber composition containing a variety of conventional flame retardants, such as Saytex (decabromodiphenyl oxide), Sb₂O₃, chlorinated paraffin wax, and polychloroprene rubber, was prepared and used to coat nylon 6 fabric in a laboratory‐coating device. An attempt was made to evaluate the decomposition profile, the evolved gases, and the kinetics of the decomposition process at a dynamic heating rate with high‐resolution thermogravimetric analysis (HR‐TGA). HR‐TGA was used with mass spectrometry for evolved gas analysis (EGA). The HR‐TGA results were compared with results from conventional thermogravimetric analysis (TGA) at a constant heating rate; the former offered sharp transitions, an economic timescale, and an accurate activation energy. The resolution optimization for stability analysis and the effect of its variation on the kinetic parameters offered better results for HR‐TGA than conventional TGA. A lifetime and temperature relationship was evaluated in HR‐TGA with Toop's method, and it was observed that the shelf life decreased sharply with temperature. The effluents HBr, HCl, Br ·, and Cl ·, generated between 210 and 496°C during EGA, were correlated with the thermal stability and fire‐retardancy behavior of the material. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 2051–2057, 2003     

Pyrolysis of wheat straw in a thermogravimetric analyzer: Effect of particle size and heating rate on devolatilization and estimation of global kinetics

The influence of different parameters such as particle size, initial weight of the sample, and heating rate on the devolatilization of wheat straw particles have been studied using thermogravimetric analysis. In addition, the variations in proximate analysis with different particle sizes of wheat straw have also been investigated. Results show that the curves corresponding to the third stage of pyrolysis differ for variations in particle size, initial weight, and heating rate of the pyrolysis process. A devolatilization model with three parallel nth-order reactions has been considered to determine the global kinetic parameters using thermogravimetric data. The kinetic parameters such as activation energy (kJ/mol), frequency factor (1/min), and order of the reaction for the three stages considered in devolatilization model were E₁ = 69, E₂ = 78, E₃ = 80; k₀₁ = 2.57 × 10¹², k₀₂ = 3.97 × 10⁷, k₀₃ = 3.17 × 10⁶; and n₁ = 2.3, n₂ = 0.65, n₃ = 2.7, respectively. It was noted from the order of the reaction that the second stage of the pyrolysis curve corresponds to the degradation of cellulose and hemicellulose, and the third stage to the lignin degradation.     

Thermogravimetric analysis and pyrolysis of waste mixtures of paint and tar slag

We describe thermogravimetric analyses and pyrolysis kinetic studies carried out on hazardous waste mixtures of tar slag, paint slag, paper, sodium sulfate and calcium oxide. Both thermogravimetric (TG) and differential thermogravimetric (DTG) profiles were measured by a thermogravimetric analyzer at different final temperatures, particle sizes and heating rates. Pyrolysis kinetic parameters were calculated by the Coats-Redfern method. Influences of particle size, heating rate and final temperature on pyrolysis yields and kinetic parameters are also discussed. The results show that final temperature and particle size have a great effect on pyrolysis yields. We find that with increasing temperature the activation energy initially increases to a maximum value and then decreases. This work was presented at the 7 ^th China-Korea Workshop on Clean Energy Technology held at Taiyuan, Shanxi, China, June 26–28, 2008.     

Synthesis, Spectral, Morphology, Thermal Degradation Kinetics and Antibacterial Studies of Terpolymer Metal Complexes

Terpolymer metal complexes involving transition metal ions such as Cu(II), Mn(II) and Zn(II) were prepared using a terpolymer ligand derived from anthranilic acid–phenyl hydrazine–formaldehyde (APHF). The terpolymer ligand and its metal complexes were intended to spectral characterizations viz. FTIR, electronic, ESR, ¹H NMR and ¹³C NMR to elucidate the structural confirmations. The number, weight, and size average molecular weights of the terpolymer ligand were determined by gel permeation chromatography (GPC). The empirical formula of the repeating unit for both the terpolymer ligand and its metal complexes was clearly justified by elemental analysis. The thermal stability of the ligand and its metal complexes was established by thermogravimetric analysis (TGA). On basis of the TGA data, the kinetic and thermodynamic parameters such as activation energy (E _a), order of reaction (n), entropy change (ΔS), apparent entropy (S*), frequency factor (Z) and free energy change (ΔF) were calculated using Freeman–Carroll and Sharp–Wentworth methods. Further the degradation mechanism for the thermal decomposition was also identified from Phadnis–Desphande method. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) analysis were used to establish the surface morphology and nature of the terpolymer ligand and its metal complexes. In addition, the terpolymer ligand and its metal complexes were screened against the growth of few bacteria and their inhibitions were measured and reported.     

Non-isothermal nitridation kinetics of Ti6Al4V in Al2O3-based refractories

To establish a kinetic model of nitridation of Ti6Al4V in Al₂O₃-based refractories, the non-isothermal nitridation of Ti6Al4V–Al₂O₃ composite refractories at various heating rates was investigated using a thermogravimetric (TG) analyzer for large samples. The activation energy (E) and kinetic model (G(α)) for the nitridation of Ti6Al4V were determined using the isoconversional and master plots methods, respectively. The nucleation and growth of nitriding products of the TiN solid solution was the controlling step in the nitridation of Ti6Al4V in Al₂O₃-based refractories. The Avrami-Erofeev kinetic model, depicted by the G(α) = [-ln (1-α)]⁴ equation, is the most rational kinetic model. The values of E and A for the nitridation of Ti6Al4V were calculated to be 214.99 kJ/mol and 1.46 × 10⁷ (S^?1), respectively.     

Thermal oxidative degradation kinetics of PP and PP/mg (OH)2 flame‐retardant composites

The thermal stability and thermal oxidative degradation kinetics of polypropylene (PP) and flame‐retardant PP composites filled with untreated and treated magnesium hydroxide (MH) in air were studied by thermogravimetric analysis (TGA). The effect of the heating rate in dynamic measurements (5°C–30°C/min) on kinetic parameters such as activation energy was also investigated. The Kissinger and Flynn–Wall–Ozawa methods were used to determine the apparent activation energy for the degradation of neat PP and flame‐retardant PP composites. The results of TGA showed that the addition of untreated or treated MH improved the thermal oxidative stability of PP in air. The kinetic results showed that the apparent activation energy for degradation of flame‐retardant PP composites was much higher than that of neat PP, suggesting that the flame retardant used in this work had a great effect on the mechanisms of pyrolysis and combustion of PP. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1978–1984, 2007     

Kinetics of thermal degradation of poly(p‐phenylene benzobisoxazole)

The kinetics of thermal degradation of poly (p-phenylen benzobisoxazole) (PBO) were studied by thermogravimetric analysis (TG) in dynamic nitrogen gas at four different heating rates: 5, 10, 15, 20°C/min. The activation energy calculated by Kissinger Method was 352.19 kJ/mol, and the mean value of activation energies evaluated by Flynn-Wall-Ozawa Method was 338.32 kJ/mol. The degradation kinetic model of PBO followed the mechanism of random scission of weak bonds of PBO molecule and impact of the active groups obtained from the broken bonds, Mampel Power equation with integral form G(α) = α^3/2 and differential form . And the mathematical equation of kinetic compensation effect was ln A = 0.1365 E_a − 1.4102. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3675–3679, 2007     

Pyrolysis kinetics of Athabasca bitumen using a TGA under the influence of reservoir sand

Pyrolysis kinetics of thermal decomposition of bitumen was investigated by thermogravimetric analysis (TGA). TGA experiments were conducted at multiple heating rates of 5, 10, 20°C min^–1 up to 800°C to obtain the pyrolysis characteristics of bitumen. Weight loss curve from TGA shows that two different stages occurred during bitumen pyrolysis. Differential method has been used for determining the kinetic parameters and the best fit for the order of reaction was found based on the R² values. Kinetics results confirm the presence of two different stages in bitumen pyrolysis with varying kinetic parameters. The average activation energy for the first and second stage was 29 and 60 kJ mol^?1 and the average order of the reaction was 1.5 and 0.25, respectively. Experiments have been conducted with different reservoir sand. The effect of different source of sand reveals no effect on the pyrolysis behaviour of bitumen. A considerable difference was found with the pyrolysis of bitumen–sand mixtures and bitumen alone based on coke yield and activation energy. © 2011 Canadian Society for Chemical Engineering     

Kinetics of calcium carbonate decomposition

Experiments on thermal decomposition of calcium carbonate were carried out in a thermogravimetric analyser under non-isothermal conditions of different heating rates (10 to 100°C/ min). A new technique for determining the kinetic parameters from non- isothermal thermogravimetric data was described. The activation energy and frequency factors were determined from the proposed method and also by the widely used Coats and Redfern method. The kinetic compensation effect between the activation energy and frequency factors obtained from both the methods were found to be very consistent and are in very good agreement with the literature values. The activation energy and frequency factors were also determined from isothermal experiments in the temperature range from 680 to 875°C. The activation energy and frequency factors determined from isothermal data using initial rate method were also found to be in very good agreement with the above results. It is also found that the kinetic parameters determined by isothermal analysis were consistent with the values determined by non-isothermal analysis.