Effect of CeO2 on the reaction kinetics for the formation of Sr0.5Ba0.5CexNb2O6+δ

2003 ◽  
Vol 18 (11) ◽  
pp. 2594-2599 ◽  
Author(s):  
Jyh-Tzong Shiue ◽  
Tsang-Tse Fang
Keyword(s):  
Activation Energy ◽  
Kinetic Equation ◽  
Solid State ◽  
Empirical Model ◽  
Reaction Model ◽  
Heating Rates ◽  
Strontium Barium ◽  
Isothermal Reaction ◽  
Nonisothermal Kinetic ◽  
Different Temperatures

The solid-state reaction of SrNb2O6, BaNb2O6, and CeO2 to form Sr0.5Ba0.5CexNb2O6+δ at different temperatures and heating rates was investigated. A nonisothermal kinetic empirical model was used to evaluate the activation energy and rate constant of Sr0.5Ba0.5CexNb2O6+δ. The values of the activation energy evaluated from the slopes are 762, 800, and 844 kJ/mol, respectively, for S50, 1CeS50, and 2CeS50, which increase with the increase in Ce doping. The order of reaction was found to decrease with the increase of the Ce doping. A kinetic equation was developed based on the parameters evaluated from the nonisothermal reaction model, which was successfully used to predict the isothermal reaction of Ce-doped strontium barium niobate.

scholarly journals Apparent Pyrolysis Kinetics and Index-Based Assessment of Pretreated Peach Seeds

Processes ◽  
2021 ◽  
Vol 9 (6) ◽  
pp. 905
Author(s):  
Angelos-Ikaros Altantzis ◽  
Nikolaos-Christos Kallistridis ◽  
George Stavropoulos ◽  
Anastasia Zabaniotou
Keyword(s):  
Activation Energy ◽  
Industrial Sector ◽  
Reaction Model ◽  
Specific Rate ◽  
Atmospheric Conditions ◽  
Pyrolysis Kinetics ◽  
Heating Rates ◽  
Hexane Extraction ◽  
Exponential Factor ◽  
Different Temperatures

To better understand pyrolysis for upscaling purposes, a kinetic characterization of the process is necessary for every feedstock. Laboratory experiments allow identification of apparent kinetic models. This paper aims at the apparent kinetic investigation of peach seeds’ slow pyrolysis. Peach seeds from Greek peach fruits pyrolyzed under inert atmospheric conditions at different temperatures (475–785 °C), heating rates (100–250 °C/min) and N2 flow rates (25–200 cc/min). Prior to pyrolysis, they submitted to hexane extraction for the recovery of 36.8% wt. of the contained oils. Determination of the specific rate constant (k) and activation energy (Ea) for each considered reaction was made by using the Coats–Redfern integral non-isothermal fitting model that requires an assumption of the reaction order (n). Results revealed that a 3rd order reaction model best fits the process, the increasing of the pyrolysis temperature leads to a decrease of the activation energy (E) and pre-exponential factor (A), while nitrogen flow rate and heating rate had an opposite impact. E and A values ranged from 23 to 56 kJ/mol and 1.82 × 106 to 1.13 × 106 min−1, respectively, at different pyrolysis conditions. Furthermore, estimation of combustion and pyrolysis indexes were made to assess the suitability of peach seeds as a fuel, using isothermal thermogravimetric analyses (TGA). Results revealed that peach seeds are a suitable feedstock for pyrolysis, while prior submission of peach seeds to oils extraction, in a cascade biorefinery approach, can increase the energy and material recovery efficiency and potentially the environmental and economic benefit of the agri-food industrial sector.

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.

scholarly journals A Modified Model for Kinetic Analysis of Petroleum Coke

2019 ◽  
Vol 2019 ◽  
pp. 1-8
Author(s):  
Iman Eslami Afrooz ◽  
Dennis Ling Chuan Ching
Keyword(s):  
Activation Energy ◽  
Distribution Function ◽  
Normal Distribution ◽  
Heating Rate ◽  
Reaction Model ◽  
Normal Distribution Function ◽  
Gravimetric Analysis ◽  
Heating Rates ◽  
Shrinking Core ◽  
Volume Reaction

In this study, a nonisothermal kinetics analysis of petcoke was performed at heating rates of 10, 15, and 20°C/min using thermal gravimetric analysis (TGA). The behaviour of petcoke at different gasification stages (dewatering, volatilization, char burning, and burnout) was studied. The effect of heating rate on the activation energy of petcoke gasification was also investigated. The activation energy of petcoke was estimated using different kinetic models that include volume reaction model (VRM), shrinking core model (SCM), random pore model (RPM), Coats and Redfern model (CRM), and normal distribution function (NDF). The NDF model was modified in this study. It was found that the experimental data were best fitted with the modified normal distribution function (MNDF) and SCM. The results also showed that activation energy decreases as heating rate increases, leading to reduction in gasification completion time.

scholarly journals Comparison of the dehydration kinetics of solid state compounds of 2-methoxybenzylidenepyruvate with some divalent metal ions

2010 ◽  
Vol 35 (1) ◽  
pp. 7-18
Author(s):  
M. Kobelnik ◽  
C. A. Ribeiro ◽  
D. S. Dias ◽  
G. A. Bernabé ◽  
M. S. Crespi
Keyword(s):  
Activation Energy ◽  
Solid State ◽  
Nitrogen Atmosphere ◽  
Divalent Metal ◽  
Point Of View ◽  
Conversion Degree ◽  
Divalent Metal Ions ◽  
Heating Rates ◽  
Exponential Factor ◽  
Kinetics Of

Divalent metal complexes of ligand 2-methoxybenzylidenepyruvate with Fe, Co, Ni, Cu and Zn as well as sodium salt were synthesized and investigated in the solid state. TG curves of these compounds were obtained with masses sample of 1 and 5mg under nitrogen atmosphere. Different heating rates were used to characterize and study these compounds from the kinetic point of view. The activation energy and pre-exponential factor were obtained applying the Wall-Flynn-Ozawa method to the TG curves. The obtained data were evaluated and the values of activation energy (Ea / kJ mol-1) was plotted in function of the conversion degree (α). The results show that due to mass sample, different activation energies were obtained. The results are discussed mainly taking into account the linear dependence between the activation energy and the pre exponential factor, where was verified the effect of kinetic compensation (KCE) and possible linear relations between the dehydrations steps of these compounds.

scholarly journals Systematic kinetic study of magnesium production using magnesium oxide and carbonic materials at different temperatures

2021 ◽  
Vol 68 (1) ◽  
Author(s):  
Hamid Zahedi ◽  
Nahid Farzi ◽  
Nasser Golestani
Keyword(s):  
Activation Energy ◽  
Kinetic Equation ◽  
Solid State ◽  
Magnesium Oxide ◽  
Chemical Kinetics ◽  
Rate Coefficient ◽  
Reducing Agent ◽  
General Definition ◽  
Mathematical Function ◽  
State Chemical

Abstract The main goal of this study was to determine the industrially best reductant for reduction of magnesium oxide to magnesium with wood charcoal and petroleum coke (petcoke) each in molar ratio 1:1 and 1:2 (oxidant:reductant) at high temperatures. In this study, a new and reliable combination of mathematical modeling and discrete numerical optimization theory by presenting 18 “mathematical filters” not relying only on statistical quantities of fitting (contrary to many similar researches) was introduced. The purpose of these filters was the determination of correct kinetic equation and therefore, the corresponding rate coefficient from among 18 equations most used at present in the challenging field of solid state chemical kinetics. With assistance of a new and fundamental mathematical function and the obtained values of rate coefficients, the function of rate coefficient in temperature was attained. The activation energy was then calculated as a function of temperature using the general definition of activation energy and the determined function for rate coefficient. The comparison between different reducing agents in the different conditions and with relevant previous study was accomplished to determine the best reducing agent from industry standpoint. Also, the areas under experimental data were calculated numerically and utilized for method validation and comparison. It turned out finally that relying only on fitting quantities in the solid state chemical kinetics can readily lead to wrong conclusions about the correct kinetic equation and about the most suitable reducing agent. It is obvious that the erroneous calculations and wrong decisions in the laboratory scale become significant and paramount in industry and this reveals the significance of rigorous mathematical analysis. Graphical abstract

scholarly journals Kinetic Analysis of the Curing of a Partially Biobased Epoxy Resin Using Dynamic Differential Scanning Calorimetry

Polymers ◽  
2019 ◽  
Vol 11 (3) ◽  
pp. 391 ◽  
Author(s):  
Diego Lascano ◽  
Luis Quiles-Carrillo ◽  
Rafael Balart ◽  
Teodomiro Boronat ◽  
Nestor Montanes
Keyword(s):  
Experimental Data ◽  
Activation Energy ◽  
Differential Scanning Calorimetry ◽  
Epoxy Resins ◽  
Curing Kinetics ◽  
Reaction Model ◽  
Diglycidyl Ether ◽  
Heating Rates ◽  
Scanning Calorimetry ◽  
Model Free

This research presents a cure kinetics study of an epoxy system consisting of a partially bio-sourced resin based on diglycidyl ether of bisphenol A (DGEBA) with amine hardener and a biobased reactive diluent from plants representing 31 wt %. The kinetic study has been carried out using differential scanning calorimetry (DSC) under non-isothermal conditions at different heating rates. Integral and derivative isoconversional methods or model free kinetics (MFK) have been applied to the experimental data in order to evaluate the apparent activation energy, Ea, followed by the application of the appropriate reaction model. The bio-sourced system showed activation energy that is independent of the extent of conversion, with Ea values between 57 and 62 kJ·mol−1, corresponding to typical activation energies of conventional epoxy resins. The reaction model was studied by comparing the calculated y(α) and z(α) functions with standard master plot curves. A two-parameter autocatalytic kinetic model of Šesták–Berggren [SB(m,n)] was assessed as the most suitable reaction model to describe the curing kinetics of the epoxy resins studied since it showed an excellent agreement with the experimental data.

Kinetics of Hydrothermal Decomposition of Potassium Feldspar with Calcium Hydroxide

2012 ◽  
Vol 549 ◽  
pp. 65-69 ◽  
Author(s):  
Yu Qin Liu ◽  
Hong Tu Xia ◽  
Hong Wen Ma
Keyword(s):  
Activation Energy ◽  
Kinetic Equation ◽  
Calcium Hydroxide ◽  
Arrhenius Equation ◽  
Hydrothermal Reaction ◽  
Potassium Feldspar ◽  
Different Temperatures ◽  
Temperature Ranges ◽  
Dissolution Ratio ◽  
Kinetics Of

The aegirine-augite syenite potash ore, taken from Changling, Luonan in Shannxi province, were hydrothermally decomposed over the temperature ranges of 533 K to 563 K using calcium hydroxide as additive. The dissolution ratio of the K2O at different reaction temperature and time was determined. Analysis of the experimental results revealed that the dissolution rate of potash ore satisfies the chemical reaction controlled kinetic equation. The rate constant of hydrothermal reaction at different temperatures was obtained. The activation energy was calculated using the Arrhenius equation. The hydrothermal decomposition mechanism of microcline was proposed.

scholarly journals Non-isothermal reaction mechanism and kinetic analysis for the synthesis of monoclinic lithium zirconate (m-Li2ZrO3) during solid-state reaction

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Juan P. Yasnó ◽  
Susana Conconi ◽  
Arnaldo Visintin ◽  
Gustavo Suárez
Keyword(s):  
Reaction Mechanism ◽  
Solid State ◽  
Kinetic Analysis ◽  
Solid State Reaction ◽  
Diffusion Mechanism ◽  
Model Fitting ◽  
Isoconversional Methods ◽  
Heating Rates ◽  
Isothermal Reaction ◽  
Lithium Zirconate

AbstractNon-isothermal reaction mechanism and kinetic analysis for the synthesis of monoclinic lithium zirconate (m-Li2ZrO3) were investigated by processing of TG-DTA, along with XRD, DLS, and HRTEM. For this purpose, the solid-state reaction of Li2CO3 with ZrO2 was carried out by TG-DTA at different heating rates (10, 20, and 30 °C/min) from room temperature to 1100 °C. The thermal data was used to calculate the kinetic parameters by two types of isoconversional methods: Flynn-Wall-Ozawa (FWO) and Kissinger-Akahira-Sunose (KAS). The reaction mechanism was determined by the model-fitting method, applying the Coats-Redfern (CR) approximation to the different solid-state reaction models. The results confirmed the formation of pure m-Li2ZrO3, consists of semispherical particles of about 490 nm, using a very short reaction time. The average activation energy obtained by FWO and KAS methods were 274.73 and 272.50 kJ/mol, respectively. It was found that the formation of m-Li2ZrO3 from Li2CO3 with ZrO2 is governed by the three-dimensional diffusion mechanism. Based on these results, a microscopic reaction model of the formation of m-Li2ZrO3 was proposed.

scholarly journals Determination of Thermodynamic Parameters of Polylactic Acid by Thermogravimetry under Pyrolysis Conditions

2021 ◽  
Vol 11 (21) ◽  
pp. 10192
Author(s):  
Paul Palmay ◽  
Melissa Mora ◽  
Diego Barzallo ◽  
Joan Carles Bruno
Keyword(s):  
Activation Energy ◽  
Heating Rate ◽  
Thermodynamic Parameters ◽  
Polylactic Acid ◽  
Reaction Model ◽  
Raw Material ◽  
Heating Rates ◽  
Statistical Validation ◽  
Exponential Factor ◽  
Degradation Temperature

In the present study, the thermodynamic parameters of Polylactic Acid (PLA) under conditions of thermal degradation were determined. The PLA material, previously sampled and characterized, was analyzed by dynamic thermogravimetry (TG) at heating rates of 5, 10 and 15 °C min−1 with a nitrogen flow of 20 mL min−1 from a temperature of 25 to 900 °C. The data were treated using isoconversional kinetic models to obtain the activation energy and the pre-exponential factor of each model. To fit the DTG curves, the Arrhenius equation was used applying the Contraction Sphere reaction model: two-dimensional phase limit reaction (R2). The thermodynamic parameters such as enthalpy, Gibbs free energy and entropy were determined from the kinetic parameters of suitable models for each heating rate after statistical validation and comparison with other studies. The results showed that as the heating rate increases, the degradation temperature also increases, while the activation energy, enthalpy and pre-exponential factor decrease. According to the value of ∆G (171.65 kJ mol−1), PLA has a significant potential to be used as a raw material to produce bioenergy/biofuels by pyrolysis.

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