Thermooxidative degradation and its kinetics of natural rubber coagulated by microwave radiation

2012 ◽  
Vol 32 (8-9) ◽  
pp. 511-517 ◽  
Author(s):  
Lu-Sheng Liao ◽  
Jian-He Liao ◽  
Yi-Min Li ◽  
Yong-Ping Chen ◽  
Yan-Fang Zhao ◽  
...  
Keyword(s):  
Activation Energy ◽  
Kinetic Model ◽  
Natural Rubber ◽  
Microwave Radiation ◽  
Preexponential Factor ◽  
Degradation Process ◽  
Main Stage ◽  
Thermooxidative Degradation ◽  
Mean Values ◽  
One Step

Abstract The thermooxidative degradation of natural rubber (NR) coagulated by microwave radiation (NR-m) was investigated by thermogravimetry (TG) analysis, and compared with NR coagulated by acid (NR-a). It was found that the degradation process is not a one-step reaction, the main degradation process occurs at 300–400ºC, and the equilibrium degradation temperatures of NR-m are higher than those of NR-a. Different methods were used to find the most probable kinetic model and the Arrhenius para­meters (activation energy E and preexponential factor A) for the main stage of thermooxidative degradation of NR-m. The results show that the values of E and A, obtained from the Coats-Redfern method, are highly variable with the kinetic model chosen and the heating rate (β), and the apparent activation energy (E0) when β approaches zero for the Dn type kinetic model is in the range of 96.7–106.4 kJ ∙ mol-1. The mean values of E, calculated by the Friedman and Flynn-Wall-Ozawa (FWO) methods, are 113.8 and 83.3 kJ ∙ mol-1, respectively, suggesting E in the range of 83.3–113.8 kJ ∙ mol-1. Comparison of these two ranges indicates the most probable kinetic model to be Dn type kinetic models, corresponding to a diffusion-controlled mechanism.

Studies of thermooxidative degradation process of chlorinated natural rubber from latex

2004 ◽  
Vol 410 (1-2) ◽  
pp. 119-124 ◽  
Author(s):  
He-ping Yu ◽  
Si-dong Li ◽  
Jie-ping Zhong ◽  
Kui Xu
Keyword(s):  
Natural Rubber ◽  
Degradation Process ◽  
Thermooxidative Degradation

Thermal Stability and Kinetic Analysis of Xanthoceras sorbifolia Polysaccharide

2012 ◽  
Vol 518-523 ◽  
pp. 3904-3907 ◽  
Author(s):  
Quan Cheng Zhou ◽  
Hong Mei Zhang ◽  
De Mao Li
Keyword(s):  
Activation Energy ◽  
Thermal Stability ◽  
Kinetic Model ◽  
Thermal Degradation ◽  
Kinetic Analysis ◽  
Large Scale ◽  
Degradation Process ◽  
Second Step ◽  
Step Process ◽  
Thermal Degradation Process

Pyrolysis and kinetic analysis of Xanthoceras Sorbifolia polysaccharide were evaluated using the TG-DTG/DTA method. The results indicated that its mass loss occured in three-step process . The first step could be attributed to the expulsion of water of crystallization at 25 - 176 °C. The second step corresponded to the large scale degradation of X. Sorbifolia polysaccharide in the temperature range of 179 - 661 °C. The final step was slow degradation of residues. Heating rate had significant effects on the pyrolysis of X. Sorbifolia polysaccharide and nitrogen could improve its stability. A close value of activation energy E of the thermal degradation process has been obtained by FWO, KAS and Popescu methods. The possible kinetic model was estimated to be Jander 5 (g(α)=[1-(1-α)1/3]1/2.

Analysis of mechanism of the catalytic effect of hydrogen on the decay of alkyl macroradicals in polyethylene

1986 ◽  
Vol 51 (6) ◽  
pp. 1279-1286 ◽  
Author(s):  
Josef Bartoš
Keyword(s):  
Activation Energy ◽  
Kinetic Model ◽  
Energy Barrier ◽  
Catalytic Effect ◽  
Molecular Model ◽  
Particle State ◽  
One Step ◽  
The One ◽  
Step Mechanism ◽  
Phase Proceeds

The suggested one-step and two-step mechanism of decay of alkyl macroradicals in polyethylene are analyzed in detail at the activation energy level. For the one-step mechanism, the BEBO method is modified for reactions proceeding via a three-particle state. For the two-step mechanism, a three-process kinetic model is used; the contributions to the total energy barrier are calculated by the original BEBO method for two-particle transition states and by a molecular model for the diffusion of simple penetrants in polymers. The results indicate that the catalytic effect of hydrogen on the migration of the alkyls in the amorphous phase proceeds by the two-step mechanism.

Kinetics of Thermal Degradation of Ionic Liquid Regenerated Cellulose

2012 ◽  
Vol 488-489 ◽  
pp. 923-927
Author(s):  
Nawshad Muhammad ◽  
Zakaria B. Man ◽  
M. Azmi Bustam Khalil ◽  
Sikander Rafiq
Keyword(s):  
Activation Energy ◽  
Ionic Liquid ◽  
Kinetic Model ◽  
Thermal Degradation ◽  
Kinetic Parameters ◽  
Dynamic Condition ◽  
Degradation Process ◽  
Waste Paper ◽  
Regenerated Cellulose ◽  
Kinetics Of

In the present work ionic liquid has been used for the regeneration of cellulose from waste writing paper. The regenerated cellulose was characterized by TGA, FTIR and XRD analyses. Kinetics of thermal degradation of this cellulose was carried out under dynamic condition using thermogravimetry. Coats-Redfern kinetic model was used to determine the kinetic parameters for the degradation process. The activation energy for the thermal degradation of the regenerated cellulose has been found to be less than the precursor waste paper.

A kinetic modeling study of ethylene pyrolysis

2000 ◽  
Vol 78 (1) ◽  
pp. 16-25 ◽  
Author(s):  
John M Roscoe ◽  
Alain R Bossard ◽  
Margaret H Back
Keyword(s):  
Activation Energy ◽  
Kinetic Model ◽  
Temperature Dependence ◽  
Key Words ◽  
Kinetic Modeling ◽  
Rate Constants ◽  
Preexponential Factor ◽  
Isomerization Reaction ◽  
Experimental Measurements ◽  
Experimental Conditions

A kinetic model is presented for the pyrolysis of ethylene at pressures ranging from 0.8 to 27 kPa and temperatures from 774 to 1023 K. The model is based on experimental measurements of C2H2, C2H6, C3H6, 1-C4H8, and 1,3-C4H6. In this temperature range the reaction is initiated by the disproportionation of C2H4 and the observed products result from reactions of the C2H3 and C2H5 radicals produced in this process. The C2H2 and 1,3-C4H6 result from reactions of C2H3 while C2H6, C3H6, and 1-C4H8 result from reactions of C2H5. C2H2 is produced exclusively by the decomposition of the C2H3 radical. This process is in its falloff region throughout the range of experimental conditions examined and the yield of C2H2 provides a measure of the degree of falloff. The production of 1,3-C4H6 is controlled by the reaction C4H7 –> C4H6 + H. The rate constants for this reaction were independent of pressure and are given as a function of temperature by k = 2.2 × 1013 exp (-19.6 × 103/T). Production of C2H6 is controlled by the reaction C2H5 + C2H4 –> C2H6 + C2H3. The rate constant for this reaction is given as a function of temperature by k = 5.83 × 1011 exp (-14.6 × 103/T). C3H6 is produced by decomposition of 2-C4H9 and is controlled kinetically by the isomerization reaction 1-C4H9 –> 2-C4H9. The temperature dependence of the rate constants obtained for this reaction leads to a preexponential factor of approximately 3 × 1016 and an activation energy of approximately 200 kJ mol-1. The yield of 1-C4H8 is controlled by 1-C4H9 –> 1-C4H8 + H. The rate constants for this reaction were independent of pressure and are given as a function of temperature by k = 2.97 × 1012 exp (-17.1 × 103/T). Key words: kinetic modeling, ethylene pyrolysis.

scholarly journals Superior Degradation Performance of Nanoporous Copper Catalysts on Methyl Orange

Metals ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 913
Author(s):  
Jinyi Wang ◽  
Sen Yang
Keyword(s):  
Activation Energy ◽  
Methyl Orange ◽  
High Efficiency ◽  
Low Cost ◽  
Degradation Process ◽  
Copper Catalysts ◽  
Reaction Rate Constant ◽  
Nanoporous Structure ◽  
Intra Particle Diffusion ◽  
Different Temperatures

The development of low-cost and high-efficiency catalysts for wastewater treatment is of great significance. Herein, nanoporous Cu/Cu2O catalysts were synthesized from MnCu, MnCuNi, and MnCuAl with similar ligament size through one-step dealloying. Meanwhile, the comparisons of three catalysts in performing methyl orange degradation were investigated. One of the catalysts possessed a degradation efficiency as high as 7.67 mg·g−1·min−1. With good linear fitting by the pseudo-first-order model, the reaction rate constant was evaluated. In order to better understand the degradation process, the adsorption behavior was considered, and it was divided into three stages based on the intra-particle diffusion model. Three different temperatures were applied to explore the activation energy of the degradation. As a photocatalytic agent, the nanoporous structure of Cu/Cu2O possessed a large surface area and it also had low activation energy, which were beneficial to the excellent degradation performance.

Kinetic Model of the 1,2-Propanediol Oxidation Reaction in the Presence of 3wt%Pd/α-Al2O3 Catalyst

2021 ◽  
Vol 903 ◽  
pp. 143-148
Author(s):  
Svetlana Cornaja ◽  
Svetlana Zhizhkuna ◽  
Jevgenija Vladiko
Keyword(s):  
Activation Energy ◽  
Lactic Acid ◽  
Kinetic Model ◽  
Catalytic Oxidation ◽  
Molecular Oxygen ◽  
Oxidation Reaction ◽  
Main Product ◽  
Oxidation Process ◽  
Water Solution ◽  
Reaction Conditions

Supported 3wt%Pd/α-Al₂O₃ catalyst was tested in selective oxidation of 1,2-propanediol by molecular oxygen. It was found that the catalyst is active in an alkaline water solution. Lactic acid was obtained as the main product of the reaction. Influence of different reaction conditions on 1,2-PDO conversion and oxidation process selectivity was studied. Partial kinetic orders of the reaction with respect to 1,2-propanediol, c0(NaOH), p(O2), n(1,2-PDO)/n(Pd)) were determined and an experimental kinetic model of the catalytic oxidation reaction was obtained. Activation energy of the process was calculated and was found to be about 53 ± 5 kJ/mol.

scholarly journals Thermal Degradation Behaviour of Ni(II) Complex of 3,4-Methylenedioxaphenylaminoglyoxime

2013 ◽  
Vol 2013 ◽  
pp. 1-7 ◽  
Author(s):  
Emin Karapınar ◽  
Ilkay Hilal Gubbuk ◽  
Bilge Taner ◽  
Pervin Deveci ◽  
Emine Ozcan
Keyword(s):  
Experimental Data ◽  
Activation Energy ◽  
Free Energy ◽  
Thermal Degradation ◽  
Metal Complex ◽  
Kinetic Parameters ◽  
Preexponential Factor ◽  
Degradation Behaviour ◽  
Mechanism Of Decomposition ◽  
Pyrolytic Decomposition

Thermal degradation behaviour of the Ni(II) complex of 3,4-methylenedioxaphenylaminoglyoxime was investigated by TG, DTA, and DTG at a heating rate of 10°C min−1under dinitrogen. The acquired experimental data shows that the complex is thermally stable up to 541 K. The pyrolytic decomposition process occurs by melting metal complex and metal oxide remains as final product. The energies of the reactions involved and the mechanism of decomposition at each stage have been examined. The values of kinetic parameters such as activation energy (E), preexponential factor (A) and thermodynamic parameters such as enthalpy (ΔH), entropy (ΔS), and Gibbs free energy (ΔG) are also evaluated.

Sign in / Sign up

Export Citation Format

Share Document