scholarly journals Interpretation and Physical Meaning of Kinetic Parameters Obtained from Isoconversional Kinetic Analysis of Polymers

Polymers ◽  
2020 ◽  
Vol 12 (6) ◽  
pp. 1280 ◽  
Author(s):  
Nicolas Sbirrazzuoli
Keyword(s):  
Kinetic Parameters ◽  
Model Fitting ◽  
Isoconversional Methods ◽  
Crystalline Polymers ◽  
Kinetic Information ◽  
Biobased Polymers ◽  
Rate Limiting Step ◽  
Thermoanalytical Data ◽  
Complex Chemical Reactions ◽  
Application Fields

Several successful examples—where physically sounded kinetic information was obtained from thermoanalytical data in different application fields, such as polymerization of thermosetting resins, biobased polymers and nanocomposites, crystallization and glass transition of semi-crystalline polymers and their nanocomposites—are here presented and discussed. It is explained how the kinetic parameters obtained from advanced isoconversional methods can be interpreted in terms of reaction mechanisms or changes in the rate-limiting step of the overall process, in the case of complex chemical reactions or complex physical transitions, and how these parameters can be used to extract model-fitting parameters.

scholarly journals Kinetic Study and Thermal Decomposition Behavior of Lignite Coal

2015 ◽  
Vol 2015 ◽  
pp. 1-9 ◽  
Author(s):  
Mehran Heydari ◽  
Moshfiqur Rahman ◽  
Rajender Gupta
Keyword(s):  
Solid State ◽  
Thermal Behavior ◽  
Kinetic Parameters ◽  
Model Fitting ◽  
Isoconversional Methods ◽  
Solid State Reactions ◽  
Process Conditions ◽  
Coal Pyrolysis ◽  
Model Free ◽  
Lignite Coal

A thermogravimetric analyzer was employed to investigate the thermal behavior and extract the kinetic parameters of Canadian lignite coal. The pyrolysis experiments were conducted in temperatures ranging from 298 K to 1173 K under inert atmosphere utilizing six different heating rates of 1, 6, 9, 12, 15, and 18 K min−1, respectively. There are different techniques for analyzing the kinetics of solid-state reactions that can generally be classified into two categories: model-fitting and model-free methods. Historically, model-fitting methods are broadly used in solid-state kinetics and show an excellent fit to the experimental data but produce uncertain kinetic parameters especially for nonisothermal conditions. In this work, different model-free techniques such as the Kissinger method and the isoconversional methods of Ozawa, Kissinger-Akahira-Sunose, and Friedman are employed and compared in order to analyze nonisothermal kinetic data and investigate thermal behavior of a lignite coal. Experimental results showed that the activation energy values obtained by the isoconversional methods were in good agreement, but Friedman method was considered to be the best among the model-free methods to evaluate kinetic parameters for solid-state reactions. These results can provide useful information to predict kinetic model of coal pyrolysis and optimization of the process conditions.

scholarly journals Kinetic Parameters of Nut Shells Pyrolysis

Energies ◽  
2021 ◽  
Vol 14 (3) ◽  
pp. 682
Author(s):  
Tomasz Noszczyk ◽  
Arkadiusz Dyjakon ◽  
Jacek A. Koziel
Keyword(s):  
Kinetic Parameters ◽  
Waste Treatment ◽  
Model Fitting ◽  
Thermal Conversion ◽  
Point Of View ◽  
The European Union ◽  
Heating Rates ◽  
Isothermal Model ◽  
Biomass Residues ◽  
Conversion Point

The European Union created a European Green Deal Program (EGDP). This program aims at a sustainable economy through the transformation of the challenges related to climate and the environment. The main goal of EGDP is climate neutrality by 2050. The increase of alternative biomass residues utilization from various food processing industries and cooperation in the energy and waste management sector is required to meet these expectations. Nut shells are one of the lesser-known, yet promising, materials that can be used as an alternative fuel or a pre-treated product to further applications. However, from a thermal conversion point of view, it is important to know the energy properties and kinetic parameters of the considered biowaste. In this study, the energy and kinetic parameters of walnut, hazelnut, peanut, and pistachio shells were investigated. The results showed that raw nut shells are characterized by useful properties such as higher heating value (HHV) at 17.8–19.7 MJ∙kg−1 and moisture content of 4.32–9.56%. After the thermal treatment of nut shells (torrefaction, pyrolysis), the HHV significantly increased up to ca. 30 MJ∙kg−1. The thermogravimetric analysis (TGA) applying three different heating rates (β; 5, 10, and 20 °C∙min−1) was performed. The kinetic parameters were determined using the isothermal model-fitting method developed by Coats–Redfern. The activation energy (Ea) estimated for β = 5 °C∙min−1, was, e.g., 60.3 kJ∙mol−1∙K−1 for walnut, 59.3 kJ∙mol−1∙K−1 for hazelnut, 53.4 kJ∙mol−1∙K−1 for peanut, and 103.8 kJ∙mol−1∙K−1 for pistachio, respectively. Moreover, the increase in the Ea of nut shells was observed with increasing the β. In addition, significant differences in the kinetic parameters of the biomass residues from the same waste group were observed. Thus, characterization of specific nut shell residues is recommended for improved modeling of thermal processes and designing of bioreactors for thermal waste treatment.

scholarly journals Kinetic Analysis of the Thermal Decomposition of Polymer-Bonded Explosive Based on PETN: Model-Fitting Method and Isoconversional Method

2020 ◽  
Vol 2020 ◽  
pp. 1-12
Author(s):  
Trung Toan Nguyen ◽  
Duc Nhan Phan ◽  
Van Thom Do ◽  
Hoang Nam Nguyen
Keyword(s):  
Thermal Decomposition ◽  
Kinetic Parameters ◽  
Model Fitting ◽  
Isoconversional Method ◽  
Isothermal Tg ◽  
Decomposition Reactions ◽  
Model Free ◽  
Negative Effect ◽  
Adverse Influence ◽  
Vacuum Stability Test

This work investigates kinetics and thermal decomposition behaviors of pentaerythritol tetranitrate (PETN) and two polymer-bonded explosive (PBX) samples created from PETN (named as PBX-PN-85 and PBX-PP-85) using the vacuum stability test (VST) and thermogravimetry (TG/DTG) techniques. Both model-free (isoconversional) and model-fitting methods were applied to determine the kinetic parameters of the thermal decomposition. It was found that kinetic parameters obtained by the modified Kissinger–Akahira–Sunose method (using non-isothermal TG/DTG data) were close to those obtained by the isoconversional and model-fitting methods that use isothermal VST data. The activation energy values of thermal decomposition reactions were 125.6–137.1, 137.3–144.9, and 143.9–152.4 kJ·mol−1 for PBX-PN-85, PETN, and PBX-PP-85, respectively. The results demonstrate the negative effect of the nitrocellulose-based binder in reducing the thermal stability of single PETN, while the polystyrene-based binder seemingly shows no adverse influence on the thermal decomposition of PETN in our presented PBX compositions.

Kinetic analysis of cellulose pyrolysis: a short review

2014 ◽  
Vol 68 (7) ◽  
Author(s):  
Cristina Şerbănescu
Keyword(s):  
Major Part ◽  
Reaction Rate ◽  
Model Fitting ◽  
Isoconversional Methods ◽  
Short Review ◽  
Physicochemical Process ◽  
Cellulose Pyrolysis ◽  
Model Free ◽  
Proper Design ◽  
The Subject

AbstractSince the 1950s, cellulose pyrolysis has been the subject of intense study, with kinetic analyses forming a major part of these studies. They represent useful tools for a better understanding of the physicochemical process and for the proper design of industrial pyrolysis units. Until recently, the methods most frequently used in these analyses were based on model-fitting, i.e. the fitting of the experimental data to a number of mathematical models. Nowadays, other methods, so-called “model-free” methods, are considered to be more suited. These are based on the principle that, at constant conversion, the reaction rate depends only on temperature. In its first part, this short review presents the particularities and drawbacks of the traditional model-fitting models. Subsequently, several main contributions in this field are listed and discussed. Finally, the more suited “model-free” (isoconversional) methods are explained and several main studies presented, as well as a comparison of this method with the model-fitting ones.

The Dependency of Kinetic Parameters as a Function of Initial Solute Concentration: New Insight from Adsorption of Dye and Heavy Metals onto Humic-Like Modified Adsorbents

2021 ◽  
Vol 16 (4) ◽  
pp. 773-795
Author(s):  
Rahmat Basuki ◽  
Bambang Rusdiarso ◽  
Sri Juari Santosa ◽  
Dwi Siswanta
Keyword(s):  
Kinetic Parameters ◽  
Solute Concentration ◽  
Reaction Model ◽  
Kinetics Model ◽  
Kinetics Parameters ◽  
Rate Limiting Step ◽  
Initial Solute ◽  
Intra Particle Diffusion ◽  
Modified Adsorbents ◽  
Rate Limiting

Kinetics parameters are the essential issue in the design of water treatment systems for pollutants uptake. Though numerous studies have identified the boundary conditions that exert influence on the kinetics parameters, the influence of the dynamic initial solute concentration (C0) to the kinetic parameters generated from fitting kinetics model to experimental data has not been investigated thoroughly. This study revealed a change in the kinetics parameter value due to changes in the adsorption mechanism as an effect of dynamic C0. It was observed that at higher C0 the adsorbed solute at equilibrium (qe) increases and it takes longer time to reach equilibrium. As a result, the kinetics rate constant (k) calculated from adsorption reaction model (Lagergren, Ho, Santosa, and RBS) was decreased. In general, Ho model exhibit higher correlation coefficient value (R2) among the other model at low C0. At high C0, Ho’s R2 tend to decrease while the Lagergren and RBS’s R2 was increased. The amendment mechanism from external mass transport to intra-particle diffusion as a rate limiting step was evidenced by Boyd and Weber-Morris kinetics model. Further, the physicochemical properties of the adsorbent used in this work: chitin and Fe3O4 modified horse dung humic acid (HDHA-Fe3O4 and HDHA-Ch, respectively) with the solute: Pb(II), Methylene Blue (MB), and Ni(II) was deeply discussed in this paper. The outcomes of this work are of prime significance for effective and optimum design for pollutant uptake by adsorption equipment. Copyright © 2021 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0). 

Kinetic Modeling of the Thermal Degradation of Methacrylate Copolymers by Thermogravimetric Methods

2007 ◽  
Vol 5 (1) ◽  
Author(s):  
Ali Habibi ◽  
Juray De Wilde
Keyword(s):  
Molecular Weight ◽  
Thermal Degradation ◽  
Kinetic Parameters ◽  
Average Molecular Weight ◽  
Model Fitting ◽  
Continuous Distribution ◽  
Thermal Degradation Kinetics ◽  
Polymer Backbone ◽  
Model Free ◽  
Degradation Step

The thermal degradation kinetics of a random copolymer of isobutyl methacrylate / lauryl methacrylate, produced by free-radical solution polymerization is investigated over a temperature range of 350 to 750 K, using dynamic thermogravimetric experiments. Heat treatment of the copolymer affects the main polymer backbone and side chains. The thermal degradation of the copolymer proceeds in three distinct steps of weight loss: the first and easiest step is initiated by scissions of head-to-head linkages representing one type of defect in the polymer backbone; the second and more difficult step is initiated by scissions at the vinylidene chain ends; the third and most energetic step is initiated by random scissions within the polymer chain.The time evolution of molecular weight distribution (MWD) is measured by gel permeation chromatography (GPC). The most pronounced changes in the trend of the average molecular weight are observed during the transition from each degradation step to the subsequent one. A continuous distribution kinetic model based on a population balance is developed to describe the observed degradation behaviour of the copolymer. This comprehensive model conforms to the special mechanisms for random chain-scission and chain-end depolymerization. The pseudo-kinetic rate parameters for each degradation step are estimated to be respectively equal to 1.1 10-8, 5.6 10-8 and 1.08 10-7 mol g-1 min-1. The average calculated activation energies are respectively 89.2, 116.4 and 134.8 kJ/mol.Global kinetic parameters of degradation are also determined using dynamic thermogravimetric (TGA/DTGA) data. The model-fitting and model-free isoconversional methods are used to retrieve the kinetic parameters of the degradation process. The model-free isoconversional method can satisfactorily describe the dependence of the activation energy on the conversion and is recommended over the model-fitting methods for obtaining the reliable and consistent kinetic parameters of polymer degradation.

Kinetic Studies on the Thermal Synthesis of Fluorapatite: Model Free and Model-Fitting Methods

2018 ◽  
Vol 28 ◽  
pp. 75-89
Author(s):  
Hamid Reza Javadinejad ◽  
Sayed Ahmad Hosseini ◽  
Mohsen Saboktakin Rizi ◽  
Eiman Aghababaei ◽  
Hossein Naseri
Keyword(s):  
Activation Energy ◽  
Model Fitting ◽  
Kinetic Studies ◽  
Isoconversional Methods ◽  
Reaction Model ◽  
Heating Rates ◽  
Thermal Synthesis ◽  
Exponential Factor ◽  
Model Free ◽  
Master Plots

The kinetic study for the synthesis of Fluorapatite has been done using the thermogravimetric technique under non-isothermal conditions and at four heating rates of 5, 10, 15 and 20 °C. Both model free and model-fitting methods were used to investigate kinetic parameters. Calcium oxide, phosphorus pentoxide and calcium fluoride were used as the precursor materials. The activation energy values were calculated through model-fitting and isoconversional methods and were used to predict the reaction model and pre-exponential factor. In this case several techniques were considered such as master plots and compensation effects. The results indicated that the reaction mechanism was chemically controlled with second and third order reaction models in the whole range of conversion which the activation energy varied from 25 to 43 kJ/mol.

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