Catalytic Decomposition of Ethylene on Nanocrystalline Cobalt

Nanocrystalline cobalt was carburised with ethylene in the range 340– 500°C to obtain Co(C) nanocapsules. The carbon deposit was reduced by a flow of hydrogen in the range 500– 560°C. The reduction kinetics were studied using thermogravimetry, described by the equation: α = Α[1-exp(-kt)n]. The apparent activation energy of the reduction process of the carbon deposit was determined. After carburisation and reduction the samples were examined by XRD and HRTEM.

Download Full-text

Kinetics of carbothermic reduction of synthetic chromite

Journal of Mining and Metallurgy Section B Metallurgy ◽

10.2298/jmmb130125008w ◽

2014 ◽

Vol 50 (1) ◽

pp. 15-21 ◽

Cited By ~ 11

Author(s):

Y. Wang ◽

L. Wang ◽

J. Yu ◽

K.C. Chou

Keyword(s):

Activation Energy ◽

Apparent Activation Energy ◽

Reduction Process ◽

X Ray Diffraction ◽

X Ray ◽

Chromite Ore ◽

Current Reduction ◽

Increasing Temperature ◽

Isothermal Mode ◽

Kinetics Of

In order to optimize the current reduction process of chromite, a good knowledge of reduction mechanism involved is required. The basic component in chromite ore is FeCr2O4, thus, kinetic investigation of synthetic FeCr2O4 with different amount of carbon were carried out in the temperature range of 1473K to 1673K under both isothermal and non-isothermal mode. The iron can be easily reduced compared with chromium. And higher reduction degree of chromite can be achieved by increasing temperature and carbon content. With the supporting of X-ray Diffraction and Scanning Electron Microscope methods, the formation of metallic products followed the sequence: Fe-C alloy, (Fe,Cr)7C3and Fe-Cr-C alloy. Kinetics analysis showed that the first stage was controlled by nucleation with an apparent activation energy of 120kJ/mol, while the chromium reduction was controlled by crystallochemical transformation with an apparent activation energy of 288kJ/mol.

Download Full-text

Solid-State Kinetic Investigations of Nonisothermal Reduction of Iron Species Supported on SBA-15

Journal of Analytical Methods in Chemistry ◽

10.1155/2017/6205297 ◽

2017 ◽

Vol 2017 ◽

pp. 1-13 ◽

Cited By ~ 3

Author(s):

N. S. Genz ◽

D. Baabe ◽

T. Ressler

Keyword(s):

Activation Energy ◽

Iron Oxide ◽

Solid State ◽

Apparent Activation Energy ◽

Reduction Process ◽

Kissinger Method ◽

Iron Loading ◽

Iron Species ◽

Vis Spectroscopy ◽

Model Independent

Iron oxide catalysts supported on nanostructured silica SBA-15 were synthesized with various iron loadings using two different precursors. Structural characterization of the as-prepared FexOy/SBA-15 samples was performed by nitrogen physisorption, X-ray diffraction, DR-UV-Vis spectroscopy, and Mössbauer spectroscopy. An increasing size of the resulting iron species correlated with an increasing iron loading. Significantly smaller iron species were obtained from (Fe(III), NH4)-citrate precursors compared to Fe(III)-nitrate precursors. Moreover, smaller iron species resulted in a smoother surface of the support material. Temperature-programmed reduction (TPR) of the FexOy/SBA-15 samples with H2 revealed better reducibility of the samples originating from Fe(III)-nitrate precursors. Varying the iron loading led to a change in reduction mechanism. TPR traces were analyzed by model-independent Kissinger method, Ozawa, Flynn, and Wall (OFW) method, and model-dependent Coats-Redfern method. JMAK kinetic analysis afforded a one-dimensional reduction process for the FexOy/SBA-15 samples. The Kissinger method yielded the lowest apparent activation energy for the lowest loaded citrate sample (Ea ≈ 39 kJ/mol). Conversely, the lowest loaded nitrate sample possessed the highest apparent activation energy (Ea ≈ 88 kJ/mol). For samples obtained from Fe(III)-nitrate precursors, Ea decreased with increasing iron loading. Apparent activation energies from model-independent analysis methods agreed well with those from model-dependent methods. Nucleation as rate-determining step in the reduction of the iron oxide species was consistent with the Mampel solid-state reaction model.

Download Full-text

Kinetics of Carbothermic Reduction of Ilmenite

Materials Science Forum ◽

10.4028/www.scientific.net/msf.852.315 ◽

2016 ◽

Vol 852 ◽

pp. 315-322 ◽

Cited By ~ 1

Author(s):

Min Chen ◽

Xuan Xiao ◽

Xue Feng Zhang

Keyword(s):

Activation Energy ◽

Kinetic Parameters ◽

Carbothermic Reduction ◽

Reduction Process ◽

Phase Evolution ◽

Reduction Kinetics ◽

Isokinetic Relationship ◽

Exponential Factor ◽

Morphology Change ◽

Kinetics Of

The reduction kinetics of ilmenite was investigated. Phase evolution during the reduction process was identified by XRD and morphology change was observed using SEM. Kinetic parameters of the activation energy and pre-exponential factor were determined by Kissinger-Akahira-Sunose (KAS) method and Coast-Redfern method&artificial isokinetic relationship (IKP) respectively. Results showed that when the reaction of titanium suboxides makes a growing contribution, the conversion dependence of activation energy has an ascending trend. When the conversion exceeded 0.7, the reactants almost consumed, and the process was controlled by diffusion.

Download Full-text

Reduction Kinetics of Bayan Obo Coexisted Iron and Niobium Ore by Carbon-Bearing Pellet

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.418-420.346 ◽

2011 ◽

Vol 418-420 ◽

pp. 346-352 ◽

Cited By ~ 1

Author(s):

Fu Shun Zhang ◽

Zeng Wu Zhao ◽

Yan Li ◽

Nai Xiang Feng

Keyword(s):

Activation Energy ◽

Apparent Activation Energy ◽

Reaction Rate ◽

Mass Loss Rate ◽

Reduction Process ◽

Inert Atmosphere ◽

Reaction Rate Constant ◽

Carbon Gasification ◽

Reaction Rate Constants ◽

Two Stages

The mass loss rate of carbon-bearing pellet of coexisted iron and niobium ore during reduction process was investigated between 900 and 1050°C in inert atmosphere. The reduction mechanism was studied by analyzing reaction rate constant, apparent activation energy，and the controlling step. The results show that temperature has the significant effect on the reduction of carbon-bearing pellet. The reduction processes include the faster reaction stage and the slower reduction stage, and respective reaction rate constants in two stages are k1=exp (21.025-40484/(RT)) and k2= exp (21.060-42516/(RT))，while respective apparent activation energy are 337 and 353 KJ/mol. Both steps are controlled by carbon gasification.

Download Full-text

Reduction Kinetics Of NiS Sulphide

Archives of Metallurgy and Materials ◽

10.1515/amm-2015-0245 ◽

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.

Download Full-text

The Hydrothermal Stability and the Properties of Non- and Strongly-Interacting Rh Species over Rh/γ, θ-Al2O3 Catalysts

Catalysts ◽

10.3390/catal11010099 ◽

2021 ◽

Vol 11 (1) ◽

pp. 99

Author(s):

Guanghao Cheng ◽

Gurong Shen ◽

Jun Wang ◽

Yunhao Wang ◽

Weibo Zhang ◽

...

Keyword(s):

Activation Energy ◽

Apparent Activation Energy ◽

Aging Time ◽

Reaction Path ◽

Aging Treatment ◽

Hydrothermal Stability ◽

Hydrothermal Aging ◽

Strongly Interacting

The present work reports the effects of γ-, θ-phase of alumina on the hydrothermal stability and the properties of non- and strongly-interacting Rh species of the Rh/Al2O3 catalysts. Comparing to γ-Al2O3, θ-Al2O3 can not only reduce the amount of occluded Rh but also better stabilize Rh during hydrothermal aging treatment. When the aging time was prolonged to 70 h, all the non-interacting Rh was transformed into strongly-interacting Rh and occluded Rh. The XPS results indicated that non- and strongly-interacting Rh might exist in the form of Rh/Rh3+ and Rh4+, respectively. CO-NO reaction was chosen as a probe reaction to research more information about non- and strongly-interacting Rh. The two Rh species had similar apparent activation energy (Eapp) of 170 kJ/mol, which indicated that non- and strongly-interacting Rh follow the same reaction path. The non-interacting Rh was removed from aged samples by the acid-treated method, and obtained results showed that only 2.5% and 4.0% non-interacting Rh was maintained in aged Rh/γ-Al2O3 and Rh/θ-Al2O3.

Download Full-text

The activation energy U(T,B) in high temperature superconductor

The European Physical Journal Applied Physics ◽

10.1051/epjap/2020200223 ◽

2020 ◽

Vol 92 (2) ◽

pp. 20601

Author(s):

Abdelaziz Labrag ◽

Mustapha Bghour ◽

Ahmed Abou El Hassan ◽

Habiba El Hamidi ◽

Ahmed Taoufik ◽

...

Keyword(s):

Magnetic Field ◽

Activation Energy ◽

Phase Diagram ◽

High Temperature ◽

Apparent Activation Energy ◽

High Temperature Superconductor ◽

Flux Flow ◽

Resistivity Measurements ◽

Vortex Phase ◽

The Magnetic Field

It is reported in this paper on the thermally assisted flux flow in epitaxial YBa2Cu3O7-δ deposited by Laser ablation method on the SrTiO3 substrate. The resistivity measurements ρ (T, B) of the sample under various values of the magnetic field up to 14T in directions B∥ab-plane and B∥c-axis with a dc weak transport current density were investigated in order to determine the activation energy and then understand the vortex dynamic phenomena and therefore deduce the vortex phase diagram of this material. The apparent activation energy U0 (B) calculated using an Arrhenius relation. The measured results of the resistivity were then adjusted to the modified thermally assisted flux flow model in order to account for the temperature-field dependence of the activation energy U (T, B). The obtained values from the thermally assisted activation energy, exhibit a behavior similar to the one showed with the Arrhenius model, albeit larger than the apparent activation energy with ∼1.5 order on magnitude for both cases of the magnetic field directions. The vortex glass model was also used to obtain the vortex-glass transition temperature from the linear fitting of [d ln ρ/dT ] −1 plots. In the course of this work thanks to the resistivity measurements the upper critical magnetic field Hc2 (T), the irreversibility line Hirr (T) and the crossover field HCrossOver (T) were located. These three parameters allowed us to establish a phase diagram of the studied material where limits of each vortex phase are sketched in order to optimize its applicability as a practical high temperature superconductor used for diverse purposes.

Download Full-text

Effect of CaO on catalytic combustion of semi-coke

Green Processing and Synthesis ◽

10.1515/gps-2021-0002 ◽

2021 ◽

Vol 10 (1) ◽

pp. 011-020

Author(s):

Luyao Kou ◽

Junjing Tang ◽

Tu Hu ◽

Baocheng Zhou ◽

Li Yang

Keyword(s):

Activation Energy ◽

Apparent Activation Energy ◽

Combustion Rate ◽

Activation Energies ◽

Combustion Reaction ◽

Tg Analysis ◽

Conversion Rates ◽

Apparent Activation Energies ◽

Ozawa Integral Method ◽

Addition Amount

Abstract Generally, adding a certain amount of an additive to pulverized coal can promote its combustion performance. In this paper, the effect of CaO on the combustion characteristics and kinetic behavior of semi-coke was studied by thermogravimetric (TG) analysis. The results show that adding proper amount of CaO can reduce the ignition temperature of semi-coke and increase the combustion rate of semi-coke; with the increase in CaO content, the combustion rate of semi-coke increases first and then decreases, and the results of TG analysis showed that optimal addition amount of CaO is 2 wt%. The apparent activation energy of CaO with different addition amounts of CaO was calculated by Coats–Redfern integration method. The apparent activation energy of semi-coke in the combustion reaction increases first and then decreases with the increase in CaO addition. The apparent activation energies of different samples at different conversion rates were calculated by Flynn–Wall–Ozawa integral method. It was found that the apparent activation energies of semi-coke during combustion reaction decreased with the increase in conversion.

Download Full-text

Thermo-catalytic decomposition of polystyrene waste: Comparative analysis using different kinetic models

Waste Management & Research ◽

10.1177/0734242x19865339 ◽

2019 ◽

Vol 38 (2) ◽

pp. 202-212 ◽

Cited By ~ 14

Author(s):

Ghulam Ali ◽

Jan Nisar ◽

Munawar Iqbal ◽

Afzal Shah ◽

Mazhar Abbas ◽

...

Keyword(s):

Activation Energy ◽

Copper Oxide ◽

Solid Waste ◽

Thermodynamic Parameters ◽

Model Fitting ◽

Catalytic Decomposition ◽

Decomposition Reaction ◽

Inert Atmosphere ◽

Heating Rates ◽

Model Free

Due to a huge increase in polymer production, a tremendous increase in municipal solid waste is observed. Every year the existing landfills for disposal of waste polymers decrease and the effective recycling techniques for waste polymers are getting more and more important. In this work pyrolysis of waste polystyrene was performed in the presence of a laboratory synthesized copper oxide. The samples were pyrolyzed at different heating rates that is, 5°Cmin−1, 10°Cmin−1, 15°Cmin−1 and 20°Cmin−1 in a thermogravimetric analyzer in inert atmosphere using nitrogen. Thermogravimetric data were interpreted using various model fitting (Coats–Redfern) and model free methods (Ozawa–Flynn–Wall, Kissinger–Akahira–Sunose and Friedman). Thermodynamic parameters for the reaction were also determined. The activation energy calculated applying Coats–Redfern, Ozawa–Flynn–Wall, Kissinger–Akahira–Sunose and Friedman models were found in the ranges 105–148.48 kJmol−1, 99.41–140.52 kJmol−1, 103.67–149.15 kJmol−1 and 99.93–141.25 kJmol−1, respectively. The lowest activation energy for polystyrene degradation in the presence of copper oxide indicates the suitability of catalyst for the decomposition reaction to take place at lower temperature. Moreover, the obtained kinetics and thermodynamic parameters would be very helpful in determining the reaction mechanism of the solid waste in a real system.

Download Full-text