scholarly journals Mechanism and kinetics of the oxidation of synthetic α-NiS

2008 ◽  
Vol 73 (2) ◽  
pp. 211-219 ◽  
Author(s):  
Nada Strbac ◽  
Dragana Zivkovic ◽  
Ivan Mihajlovic ◽  
Boyan Boyanov ◽  
Zivan Zivkovic
Keyword(s):  
Activation Energy ◽  
Oxidation Process ◽  
Second Stage ◽  
Stability Diagrams ◽  
Calculation Process ◽  
Reac Tions ◽  
Desulfurization Process ◽  
Mechanism And Kinetics ◽  
Kinetic Investigations ◽  
Kinetics Of

The results of an investigation of the mechanism and kinetics of the oxidation process of synthetic ?-NiS are presented in this paper. The mechanism of ?-NiS oxidation was investigated based on the comparative analysis of DTA-TG-DTG and XRD results, as well as the constructed phase stability diagrams (PSD) for the Ni-S-O system. The kinetic investigations of the oxidation process were performed under isothermal conditions (temperature range 823-1073 K). The obtained degrees of desulfurization were used in the calculation process according to the Sharp model and the kinetic parameters, inclu?ding the activation energies and the rate constants of the characteristic reac?tions, for the oxidation of ?-NiS were determined. These results enabled the formulation of a kinetic equation for the desulfurization process: -ln (1 ? ?) = = k1? = 27.89 exp(-9860/T)?, with an activation energy of 82?4 kJ mol-1, for the first stage of the process and -ln (1 ? ?) = k2? = 1.177 exp(-4810/T)?, with an activation energy of 40?2 kJ mol-1, for the second stage.

scholarly journals Fluoride Leaching of Titanium from Ti-Bearing Electric Furnace Slag in [NH4+]-[F−] Solution

Metals ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 1176
Author(s):  
Fuqiang Zheng ◽  
Yufeng Guo ◽  
Feng Chen ◽  
Shuai Wang ◽  
Jinlai Zhang ◽  
...  
Keyword(s):  
Activation Energy ◽  
Electric Furnace ◽  
Kinetic Equations ◽  
Surface Chemical ◽  
Leaching Rate ◽  
Surface Chemical Reaction ◽  
Mechanism And Kinetics ◽  
Semi Empirical ◽  
Kinetics Of ◽  
Furnace Slag

The effects of F− concentration, leaching temperature, and time on the Ti leaching from Ti-bearing electric furnace slag (TEFS) by [NH4+]-[F−] solution leaching process was investigated to reveal the leaching mechanism and kinetics of titanium. The results indicated that the Ti leaching rate obviously increased with the increase of leaching temperature and F− concentration. The kinetic equation of Ti leaching was obtained, and the activation energy was 52.30 kJ/mol. The fitting results of kinetic equations and calculated values of activation energy both indicated that the leaching rate of TEFS was controlled by surface chemical reaction. The semi-empirical kinetics equation was consistent with the real experimental results, with a correlation coefficient (R2) of 0.996. The Ti leaching rate reached 92.83% after leaching at 90 °C for 20 min with F− concentration of 14 mol/L and [NH4+]/[F−] ratio of 0.4. The leaching rates of Si, Fe, V, Mn, and Cr were 94.03%, 7.24%, 5.36%, 4.54%, and 1.73%, respectively. The Ca, Mg, and Al elements were converted to (NH4)3AlF6 and CaMg2Al2F12 in the residue, which can transform into stable oxides and fluorides after pyro-hydrolyzing and calcinating.

Oxidation Behavior of As-Forged Fe-25wt%Cr Alloys at 1100°C in Air

2011 ◽  
Vol 695 ◽  
pp. 348-352 ◽  
Author(s):  
Hui Xie ◽  
Lei Jia ◽  
Xiao Feng Zhang ◽  
Zhen Lin Lu
Keyword(s):  
Oxidation Behavior ◽  
Oxidation Process ◽  
Hot Forging ◽  
Oxygen Ions ◽  
Second Stage ◽  
Parabolic Law ◽  
Transport Velocity ◽  
Fast Transport ◽  
Kinetics Of ◽  
Oxidation Scale

Fe-25wt%Cr alloys were fabricated by combining Powder Metallurgy (PM) with hot-forging treatment, and their oxidation behavior at 1100°C in air was investigated systematically by using XRD, SEM and EDS, respectively. The results showed that a composite oxidation scale containing both Cr2O3and FeCr2O4formed on the surface of as-forged Fe-25wt%Cr alloys after oxidation at 1100°C in air for 100 hours. The oxidation process of Fe-Cr alloys could be obviously divided into two different stages, and the kinetics of two-stage oxidation agreed well with the parabolic law. The first could be corresponding to the formation of protective Cr2O3layer, while the second could be thought as the growth of FeCr2O4and the further oxidation of the inner Cr2O3oxidation scale. The faster oxidation rate in the second stage could be attributed to both the diffusion of iron ions rapider than that of Cr in the Cr2O3layer and the fast transport velocity of oxygen ions along the cracks.

Thermal Degradation Kinetics of Poly (vinyl chloride)

2010 ◽  
Vol 96 ◽  
pp. 245-249 ◽  
Author(s):  
Bin Han ◽  
Yu Long Wu ◽  
Guo Rui ◽  
Wei Feng ◽  
Zhen Chen ◽  
...  
Keyword(s):  
Activation Energy ◽  
Thermal Degradation ◽  
Degradation Kinetics ◽  
Mass Conservation ◽  
Thermal Degradation Kinetics ◽  
Pyrolysis Mechanism ◽  
Second Stage ◽  
Volatile Products ◽  
Infrared Spectrometer ◽  
Kinetics Of

The thermal degradation of PVC resin was examined by the thermogravimetric analysis (TGA). The pyrolysis volatile products were analyzed by Fourier transform infrared spectrometer synchronized with TG test (TG-FTIR). Based on the TG results, the kinetics of thermal degradation was studied by Friedman method. The pyrolysis mechanism was discussed also. The results indicate that the pyrolysis process of PVC can be divided into two main stages: 220°C - 380°C and 380°C - 560°C. By the calculation of mass conservation and TG-FTIR results, it can be supposed that not only HCl, but also some unsubstituted aromatics such as benzene were released during the first stage. The comparison of activation energy shows that the second stage exhibited higher activation energy than the first stage. Two activation energy values in the first stage confirm that there arose two reactions in the first stage.

Study on Oxidation Kinetics of Catalytic Oxidation of Magnesium Sulfite

2011 ◽  
Vol 391-392 ◽  
pp. 1350-1353
Author(s):  
Tong Zhu ◽  
Xiao Yan Qi ◽  
Zhong Yuan Wang ◽  
Fang Yu ◽  
An An Liu ◽  
...  
Keyword(s):  
Activation Energy ◽  
Reaction Kinetics ◽  
Oxidation Kinetics ◽  
Reaction Rate ◽  
Catalyst Concentration ◽  
Oxidation Process ◽  
Sulfate Concentration ◽  
Air Compressors ◽  
Kinetics Of ◽  
Temperature Time

This paper presented a study on the reaction kinetics of magnesium sulfite catalyzed by Catalyst TR. Used a Lib-scale Plexiglas reactor aerated by air compressors to research the oxidation process Influence by pH, catalyst concentration, aeration quantity, temperature, time, sulfate concentration. Through experiment concluded the activation energy, got the formula between reaction rate and sulfate concentration.

scholarly journals OXIDATION KINETICS OF ALUMINUM ALLOY АЖ2.4М5.3МГ1.1Ц4КР3, ALLOYED WITH TIN, IN SOLID STATE

2021 ◽  
Vol 56 ◽  
pp. 17-22
Author(s):  
Orif Sh. Davlatov ◽  
◽  
Izatullo N. Ganiev ◽  
Haydar Odina Odinazoda ◽  
Safomudin S. Rajabaliev ◽  
...  
Keyword(s):  
Activation Energy ◽  
Aluminum Alloy ◽  
Weight Gain ◽  
Oxidation Kinetics ◽  
Oxidation Process ◽  
Thermogravimetric Method ◽  
Protective Properties ◽  
Initial Alloy ◽  
Kinetics Of ◽  
Improved Characteristics

The purpose of this work was to find out the features of oxidation of the aluminum alloy АЖ2.4М5.3Мг1.1Ц4Кр3 doped with tin and to develop new alloy compositions with improved characteristics. The thermogravimetric method was used to determine the oxidation kinetics of the aluminum alloy АЖ2.4М5.3Мг1.1Ц4Кр3, containing up to 0.5 wt% tin. The results showed that the process of weight gain of alloys during first 15-20 minutes of oxidation grows intensively, and then acquires an almost constant value. Oxide films formed at the beginning of the oxidation process did not possess protective properties, that fact explains an increase in the rate of oxidation of alloys with temperature in the first period. An increase in the rate of oxidation of alloy samples with temperature is noted. As well, the results revealed that tin at concentrations of 0.01 - 0.5 wt.% reduces the oxidability of the initial alloy, which is accompanied by an increase in the apparent activation energy from 82.1 to 104.3 kJ/mol.

scholarly journals Reduction Kinetics Of NiS Sulphide

2015 ◽  
Vol 60 (2) ◽  
pp. 981-983
Author(s):  
G. Smoła ◽  
A. Poczekajło ◽  
Z. Grzesik
Keyword(s):  
Activation Energy ◽  
Heterogeneous Catalysis ◽  
Reduction Process ◽  
Reduction Kinetics ◽  
Reduction Mechanism ◽  
Nickel Sulphide ◽  
Linear Kinetics ◽  
Developed Surface ◽  
Mechanism And Kinetics ◽  
Kinetics Of

Abstract Reduction mechanism and kinetics of NiS nickel sulphide obtained during the process of nickel sulphidation, have been studied as a function of temperature (723-873 K). It has been found that the reduction process follows linear kinetics with activation energy of 103 kJ/mol. It is important to note that during nickel sulphidation and after the reduction of nickel sulphide, the product sample shows highly developed surface, creating thus the potential possibilities to be applied in heterogeneous catalysis.

scholarly journals Decomposition Characteristics and Kinetics of Microalgae in N2 and CO2 Atmospheres by a Thermogravimetry

2017 ◽  
Vol 2017 ◽  
pp. 1-7 ◽  
Author(s):  
Xu Qing ◽  
Ma Xiaoqian ◽  
Yu Zhaosheng ◽  
Cai Zilin ◽  
Ling Changming
Keyword(s):  
Activation Energy ◽  
Thermogravimetric Analysis ◽  
Thermal Degradation ◽  
Apparent Activation Energy ◽  
Kinetic Parameters ◽  
Reaction Order ◽  
Heating Rates ◽  
Residual Mass ◽  
Second Stage ◽  
Kinetics Of

The thermal degradation characteristics of microalgae were investigated in highly purified N2 and CO2 atmospheres by a thermogravimetric analysis (TGA) under different heating rates (10, 20, and 40°C/min). The results indicated that the total residual mass in CO2 atmosphere (16.86%) was less than in N2 atmosphere (23.12%); in addition, the kinetics of microalgae in N2 and CO2 atmospheres could be described by the pseudo bicomponent separated state model (PBSM) and pseudo-multi-component overall model (PMOM), respectively. The kinetic parameters calculated by Coats-Redfern method showed that, in CO2 atmosphere, the apparent activation energy (E) of microalgae was between 9.863 and 309.381 kJ mol−1 and the reaction order (n) was varied from 1.1 to 7. The kinetic parameters (E,n) of the second stage in CO2 atmosphere were quite similar to those in N2 atmosphere.

Vulcanization Kinetics of Natural Rubber Coagulated by Microorganisms with Use of a Vulcameter

2010 ◽  
Vol 160-162 ◽  
pp. 1181-1186 ◽  
Author(s):  
Zhi Feng Wang ◽  
Si Dong Li ◽  
Xiao Dong She
Keyword(s):  
Activation Energy ◽  
Natural Rubber ◽  
Rate Constants ◽  
Order Reaction ◽  
First Order Reaction ◽  
First Order ◽  
Second Stage ◽  
End Stage ◽  
Two Stages ◽  
Kinetics Of

Kinetics of vulcanization of natural rubber coagulated by microorganisms (NR-m) was studied with the use of a vulcameter. In the induction period of vulcanization, the time t0 of NR-m is shorter than that of natural rubber coagulated by acid (NR-a), and the rate constant k1/a of NR-m are greater than that of NR-a. Both the curing periods of NR-m and NR-a consist of two stages. The first stage follows first-order reaction. The rate constants k2 of NR-m in the first stage are greater than that of NR-a at the same temperature, and so are the activation energy E2. The second stage (end stage of the curing period) does not follow first-order reaction, and the calculated reaction order n of NR-m is in the range of 0.82-0.85, and that of NR-a is in the range of 0.64-0.72. The rate constants k3 of the second stage for NR -m are greater than that of NR-a at the same temperature, and so is the activation energy E3.

KINETICS OF OXYGEN EXCHANGE IN HIGH TEMPERATURE SUPERCONDUCTOR YBa2Cu3O6+x

1990 ◽  
Vol 04 (01) ◽  
pp. 29-35 ◽  
Author(s):  
A. A. STEPANOV ◽  
N. G. HAINOVSKY ◽  
Yu. T. PAVLYUKHIN ◽  
A. I. RYKOV
Keyword(s):  
Activation Energy ◽  
Solid Solution ◽  
High Pressure ◽  
Oxygen Diffusion ◽  
Reaction Rate ◽  
High Temperature Superconductor ◽  
Oxygen Absorption ◽  
Second Stage ◽  
Two Stages ◽  
Kinetics Of

Kinetics of oxygen absorption in YBa 2 Cu 3 O 6+x has been described. Experiments were performed in the high pressure reactor with constant volume in the temperature range of 150–700°C and oxygen pressure 1.4–10.7 atm. Two stages of oxygen absorption in tetraphase have been discovered. The first is related to the formation of a solid solution of oxygen in Cu(I) layers with the activation energy 0.07 ± 0.01 eV . The second one is oxygen diffusion in the system of short disordered chains ( Cu − O )n with the activation energy 0.30 ± 0.01 eV . Growths of chains and their interaction during the second stage results in the formation of ortho-phase accompanied by further decrease of the reaction rate. Structure-chemical reasons for the multistage mechanism of oxygen absorption are discussed.

scholarly journals Kinetics and mechanism of arsenic sulfides oxidation

2009 ◽  
Vol 45 (1) ◽  
pp. 59-67 ◽  
Author(s):  
N. Strbac ◽  
I. Mihajlovic ◽  
D. Minic ◽  
D. Zivkovic ◽  
Z. Zivkovic
Keyword(s):  
Mathematical Modeling ◽  
Activation Energy ◽  
Oxidation Process ◽  
Kinetics Of Oxidation ◽  
Natural Mineral ◽  
Isothermal Conditions ◽  
Sulfides Oxidation ◽  
Mineral Mixture ◽  
Kinetics Of ◽  
Arsenic Sulfides

The kinetics of oxidation process of realgar and orpiment natural mineral mixture was studied under non-isothermal conditions. The proposed reaction mechanism and chemical transformation investigated by SEM-EDX, XRD and thermal analysis, are discussed. Using mathematical modeling on results obtained during analysis in non-isothermal conditions, activation energy of this process was determined.

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