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

2017 ◽  
Vol 2017 ◽  
pp. 1-13 ◽  
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.

scholarly journals Kinetics of the Volume Shrinkage of a Magnetite/Carbon Composite Pellet during Solid-State Carbothermic Reduction

Metals ◽  
2018 ◽  
Vol 8 (12) ◽  
pp. 1050 ◽  
Author(s):  
Guang Wang ◽  
Jingsong Wang ◽  
Qingguo Xue
Keyword(s):  
Activation Energy ◽  
Solid State ◽  
Apparent Activation Energy ◽  
Carbothermic Reduction ◽  
Iron Ore ◽  
Carbon Composite ◽  
Volume Shrinkage ◽  
Reduction Temperature ◽  
Iron Particles ◽  
Composite Pellet

The volume shrinkage evolution of a magnetite iron ore/carbon composite pellet during solid-state isothermal reduction was investigated. For the shrinkage, the apparent activation energy and mechanism were obtained based on the experimental results. It was found that the volume shrinkage highly depended on the reduction temperature and on dwell time. The volume shrinkage of the pellet increased with the increasing reduction temperature, and the rate of increment was fast during the first 20 min of reduction. The shrinkage of the composite pellet was mainly due to the weight loss of carbon and oxygen, the sintering growth of gangue oxides and metallic iron particles, and the partial melting of the gangue phase at high temperature. The shrinkage apparent activation energy was different depending on the time range. During the first 20 min, the shrinkage apparent activation energy was 51,313 J/mol. After the first 20 min, the apparent activation energy for the volume shrinkage was only 19,697 J/mol. The change of the reduction rate-controlling step and the automatic sintering and reconstruction of the metallic iron particles and gangue oxides in the later reduction stage were the main reasons for the aforementioned time-dependent phenomena. The present work could provide a unique scientific index for the illustration of iron ore/carbon composite pellet behavior during solid-state carbothermic reduction.

Catalytic Decomposition of Ethylene on Nanocrystalline Cobalt

2007 ◽  
Vol 128 ◽  
pp. 249-254 ◽  
Author(s):  
Urszula Narkiewicz ◽  
Marcin Podsiadły ◽  
Iwona Pełech ◽  
Waleran Arabczyk ◽  
M.J. Woźniak ◽  
...  
Keyword(s):  
Activation Energy ◽  
Apparent Activation Energy ◽  
Reduction Process ◽  
Catalytic Decomposition ◽  
Carbon Deposit ◽  
Reduction Kinetics

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.

scholarly journals Kinetics of carbothermic reduction of synthetic chromite

2014 ◽  
Vol 50 (1) ◽  
pp. 15-21 ◽  
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.

scholarly journals Analysis of Iron Oxide Reduction Kinetics in the Nanometric Scale Using Hydrogen

Nanomaterials ◽  
2020 ◽  
Vol 10 (7) ◽  
pp. 1276 ◽  
Author(s):  
Swathi K. Manchili ◽  
Johan Wendel ◽  
Eduard Hryha ◽  
Lars Nyborg
Keyword(s):  
Activation Energy ◽  
Iron Oxide ◽  
Reaction Kinetics ◽  
Reduction Process ◽  
Steel Powder ◽  
Surface Oxide ◽  
Oxide Reduction ◽  
Sintering Aid ◽  
Surface Iron ◽  
Reported Data

Iron nanopowder could be used as a sintering aid to water-atomised steel powder to improve the sintered density of metallurgical (PM) compacts. For the sintering process to be efficient, the inevitable surface oxide on the nanopowder must be reduced at least in part to facilitate its sintering aid effect. While appreciable research has been conducted in the domain of oxide reduction of the normal ferrous powder, the same cannot be said about the nanometric counterpart. The reaction kinetics for the reduction of surface oxide of iron nanopowder in hydrogen was therefore investigated using nonisothermal thermogravimetric (TG) measurements. The activation energy values were determined from the TG data using both isoconversional Kissinger–Akahira–Sunose (KAS) method and the Kissinger approach. The values obtained were well within the range of reported data. The reaction kinetics of Fe2O3 as a reference material was also depicted and the reduction of this oxide proceeds in two sequential stages. The first stage corresponds to the reduction of Fe2O3 to Fe3O4, while the second stage corresponds to a complete reduction of oxide to metallic Fe. The activation energy variation over the reduction process was observed and a model was proposed to understand the reduction of surface iron oxide of iron nanopowder.

scholarly journals Thermal analysis on potential risk of cosmetic materials by DSC

2018 ◽  
Vol 169 ◽  
pp. 01009
Author(s):  
Yi-Feng Chen ◽  
An-Chi Huang ◽  
Chung-Fu Huang ◽  
Chi-Min Shu
Keyword(s):  
Activation Energy ◽  
Thermal Analysis ◽  
Differential Scanning Calorimetry ◽  
Iron Oxide ◽  
Silicon Dioxide ◽  
Copper Oxide ◽  
Apparent Activation Energy ◽  
Potential Risk ◽  
Potential Hazard ◽  
Scanning Calorimetry

To explore the potential risk of usage on daily chemicals, the product which most contact for human directly, cosmetics, were selected as study object. In this study, common cosmetic materials, such as propylene glycol, ethanolamine, silicon dioxide, iron oxide, and copper oxide were discussed for potential hazard. According to results of differential scanning calorimetry experiments, the apparent activation energy and SADT were calculated out as 779.22 kJ mol-1 and 45°C, respectively.

Investigation on the Reduction of Ilmenite at Lower Temperatures

2016 ◽  
Vol 852 ◽  
pp. 573-578
Author(s):  
Min Chen ◽  
Xuan Xiao
Keyword(s):  
Activation Energy ◽  
Solid State ◽  
Thermogravimetric Analysis ◽  
Chemical Reaction ◽  
Reduction Rate ◽  
Reduction Process ◽  
State Reduction ◽  
Solid State Reduction ◽  
Main Impurity

The solid state reduction of ilmenite was studied using thermogravimetric analysis by a combination of XRD, SEM& EDS methods. Results showed that MgTiO3 was the main impurity and influenced the reduction process of ilmenite. When the temperature was below 1000°C, reduction was controlled by the chemical reaction and the activation energy was 163 kJ/mol. Pretreatment of milling accelerated the solid reduction rate.

Deep oxidation of 1,2-dichlorobenzene over Ti-doped iron oxide

2014 ◽  
Vol 16 (25) ◽  
pp. 12731-12740 ◽  
Author(s):  
Xiaodong Ma ◽  
Xueyue Suo ◽  
Huiqin Cao ◽  
Jie Guo ◽  
Lu Lv ◽  
...  
Keyword(s):  
Activation Energy ◽  
Iron Oxide ◽  
Apparent Activation Energy ◽  
Iron Oxides ◽  
Deep Oxidation ◽  
Lower Temperature

1,2-Dichlorobenzene was completely oxidized to CO2, H2O and HCl over Ti-doped iron oxides at lower temperature with lower apparent activation energy.

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

2011 ◽  
Vol 418-420 ◽  
pp. 346-352 ◽  
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.

Kinetics of the Solid State Reaction between MoO3 and SrCO3

1972 ◽  
Vol 27 (6) ◽  
pp. 1020-1022 ◽  
Author(s):  
G. Flor ◽  
V. Massarotti ◽  
R. Riccardi
Keyword(s):  
Activation Energy ◽  
Solid State ◽  
Apparent Activation Energy ◽  
Solid State Reaction ◽  
Diffusion Mechanism ◽  
Optical Observations ◽  
Kcal Mole ◽  
Temperature Range ◽  
Kinetics Of

AbstractThe solid state reaction MoO3 + SrCO3 → SrMoO4+ CO2 has been studied on mixtures of powdered reagents. Thermogravimetric measurements in the temperature range 412° -498 °C have been made on different mixtures and under different atmospheres. Moreover, optical observations and conductometric measurements have been carried out. The results show that the reaction is governed by a diffusion mechanism with an apparent activation energy of (60 ± 1) kcal/mole and that the main diffusing species is the Mo6+ ion.

scholarly journals Influence of Cerium on the Reduction Behaviour of Iron Oxide by Using Carbon Monoxide: TPR and Kinetic Studies

2019 ◽  
Author(s):  
Tengku Shafazila Tengku Saharuddin ◽  
Nurul Syahira Ezzaty Nor Azman ◽  
Fairous Salleh ◽  
Alinda Samsuri ◽  
Rizafizah Othaman ◽  
...  
Keyword(s):  
Activation Energy ◽  
Carbon Monoxide ◽  
Iron Oxide ◽  
Reduction Process ◽  
Kinetic Studies ◽  
Xrd Analysis ◽  
Oxide Reduction ◽  
Iron Oxide Reduction ◽  
Reduction Behaviour ◽  
Lower Temperature

Reduction of iron oxide is one of the most studied topics owing to the importance of iron/steel industry and also has been used as a precursor and active component in a number of important chemical processes. The interaction between iron oxide and other metal additive have gained interest in the past two decades due to the ability on enhancing the reduction performance of the iron oxide. Therefore, this study was undertaken to investigate the influence of cerium on the reduction behaviours of iron oxide by (10%, v/v) carbon monoxide in nitrogen. The cerium doped (Ce-Fe2O3) and non-doped iron oxide reduction behaviour and the kinetic studies have been studied by temperature programmed reduction (TPR) and the phases formed of partially and completely reduced samples were characterized by X-ray diffraction spectroscopy (XRD) while the activation energy values were calculated from Arrhenius equation using Wimmer’s method. TPR results indicate that the reduction of doped and undoped iron oxide proceeds in three steps reduction (Fe2O3 ? Fe3O4 ? FeO ? Fe), while doped iron oxide showed a large shifted towards lower temperature especially in the transition steps of FeO ? Fe. Furthermore, TPR results also suggested that by adding Ce metal into iron oxide the reduction of metal iron completed at lower temperature (700 ?C) compared to non-doped iron oxide (900 ?C). Meanwhile, XRD analysis indicated that doped iron oxide composed of Fe2O3 and a small amount of FeCe2O4. The increase in the rates of iron oxide reduction may relate to the presence of cerium species in the formed of FeCe2O4 and was confirmed by the decrease in the activation energy regarding to all transition phases (Fe2O3 ? Fe3O4 ? FeO ? Fe) during the reduction process

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