scholarly journals Study on the Size-Dependent Oxidation Reaction Kinetics of Nanosized Zinc Sulfide

2014 ◽  
Vol 2014 ◽  
pp. 1-8 ◽  
Author(s):  
Qing-Shan Fu ◽  
Yong-Qiang Xue ◽  
Zi-Xiang Cui ◽  
Ming-Fang Wang
Keyword(s):  
Activation Energy ◽  
Particle Size ◽  
Surface Energy ◽  
Apparent Activation Energy ◽  
Zinc Sulfide ◽  
Rate Constant ◽  
Oxidation Reaction ◽  
Reaction Order ◽  
Preexponential Factor ◽  
Surface Entropy

Numerous oxidation problems of nanoparticles are often involved during the preparation and application of nanomaterials. The oxidation rate of nanomaterials is much faster than bulk materials due to nanoeffect. Nanosized zinc sulfide (nano-ZnS) and oxygen were chosen as a reaction system. The influence regularities were discussed and the influence essence was elucidated theoretically. The results indicate that the particle size can remarkably influence the oxidation reaction kinetics. The rate constant and the reaction order increase, while the apparent activation energy and the preexponential factor decrease with the decreasing particle size. Furthermore, the logarithm of rate constant, the apparent activation energy and the logarithm of preexponential factor are linearly related to the reciprocal of particle diameter, respectively. The essence is that the rate constant is influenced by the combined effect of molar surface energy and molar surface entropy, the reaction order by the molar surface area, the apparent activation energy, by the molar surface energy, and the preexponential factor by the molar surface entropy. The influence regularities and essence can provide theoretical guidance to solve the oxidation problems involved in the process of preparation and application of nanomaterials.

The Effects of Particle Size on the Kinetic Parameters in the Reaction of Nano-Nio with Sodium Bisulfate Solution

2011 ◽  
Vol 36 (4) ◽  
pp. 329-341 ◽  
Author(s):  
Yongqiang Xue ◽  
Xiaopeng Wang ◽  
Zixiang Cui
Keyword(s):  
Activation Energy ◽  
Particle Size ◽  
Apparent Activation Energy ◽  
Kinetic Parameters ◽  
Rate Constant ◽  
Reaction Order ◽  
Particle Diameter ◽  
Preexponential Factor ◽  
Exponential Factor ◽  
Sodium Bisulfate

The kinetic parameters for the chemical reaction of nano-NiO of different particle sizes with aqueous sodium bisulfate solution were determined; additionally, the influence of particle size on the kinetic parameters were studied and were discussed. The results show that: there are clear effects of the particle size of nano-NiO on the rate constant, the reaction order, the apparent activation energy and the pre-exponential factor; thus the rate constant and the reaction order increase, and the apparent activation energy and the pre-exponential factor decrease, with decrease of the particle diameter; the logarithm of the preexponential factor, and the apparent activation energy, exhibit a linear relationship with the reciprocal of the particle diameter respectively. The bases of the role of the particle size are that the reaction order is influenced by the molar surface area of nano-NiO, the apparent activation energy by the molar surface energy, the preexponential factor by the molar surface entropy, and the rate constant by both the molar surface energy and the molar surface entropy.

Effect of Particle Size on Oxidation Reaction Kinetics Parameter of Cu2O Powders

2011 ◽  
Vol 284-286 ◽  
pp. 726-729 ◽  
Author(s):  
Zai Yuan Li ◽  
Yu Chun Zhai ◽  
Myongil Pang
Keyword(s):  
Activation Energy ◽  
Particle Size ◽  
Apparent Activation Energy ◽  
Reaction Kinetics ◽  
Oxidation Reaction ◽  
Raw Materials ◽  
Particle Sizes ◽  
Oxide Powders ◽  
Effect Of Particle Size ◽  
Kinetics Parameter

The 0.4mol•L-1CuSO4liquor and 5mol•L-1NaOH liquor were prepared by CuSO4·5H2O and NaOH as raw materials. The Cu2O powders were prepared by dextrose reducer and PVP dispersant. The Cu2O oxidation reaction DTA-TG-DTG curves were obtained by SDT 2960 simultaneous DSC-TGA analysis apparatus. The mensuration condition were that rise temperature velocity 15°C·min-1and deoxidize gas air. The Cu2O oxidation reaction kinetics was calculated by DTA-TG-DTG curves data. The results indicate that the cuprous oxide powders shape were spherical, their particle’ sizes were 100,200,1000nm. Their apparent activation energy were 164.38, 175.54, 282.65 KJ·mol-1, the apparent activation energy increase with Cu2O particle’ size. Their frequency factors were 1.22×1013, 1.40×1013, 2.88×1020, the frequency factors increase with particle’ size Cu2O. Their reaction progressions were 1.02, 1.00, 0.96, the reaction progression increase with Cu2O particle’ size decreased.

scholarly journals Kinetic Models of Integrated Solidification and Cementation of Cementformation Interface with New Method

2013 ◽  
Vol 7 (1) ◽  
pp. 9-17
Author(s):  
Jun Gu ◽  
Pei Zhong ◽  
Wenzheng Qin ◽  
Haoya Liu ◽  
Lifei Dong ◽  
...  
Keyword(s):  
Activation Energy ◽  
Kinetic Models ◽  
Initial Temperature ◽  
Reaction Order ◽  
Preexponential Factor ◽  
Exothermic Peak ◽  
Temperature Peak ◽  
Final Temperature ◽  
Natural Logarithm ◽  
Solidification Reaction

The isolation failure of cement-formation interface is an important and urgent problem in oil production, while an effective way to solve it is to realize the integrated solidification and cementation of cement-formation interface (ISCCFI). In order to study the kinetics of ISCCFI with MTA (Mud Cake to Agglomerated Cake) method, the Diamond Differential Scanning Calorimetry Analyzer is adopted for experiments with dynamic method and isothermal method. The results show that there is a linear relationship between the solidification reaction temperature and the heating rate of ISCCFI with MTA method. For the first exothermic peak, the initial temperature, peak tip temperature and final temperature are 53 °C, 69 °C and 83 °C respectively, and the apparent activation energy of solidification reaction is 44.39×10-3 kJ.;mol-1, the natural logarithm of preexponential factor is 7.26, the solidification reaction order is 0.88. For the second exothermic peak, the initial temperature, peak tip temperature and final temperature are 83 °C, 92 °C and 114 °C respectively, and the apparent activation energy of solidification reaction is 99.14×10-3 kJ.;mol-1, the natural logarithm of preexponential factor is 24.77, the solidification reaction order is 0.94. The maximum solidification reaction rates at 50 °C, 75 °C and 90 °C are 0.09×10-3 s-1, 0.27×10-3 s-1 and 0.51×10-3 s-1 respectively. The kinetic models of ISCCFI with MTA method under different temperatures are established. It provides a theoretical and technical support for the isolation improvement of cement-formation interface.

scholarly journals Kinetics of the Carbon Monoxide Oxidation Reaction Under Microwave Heating

1996 ◽  
Vol 430 ◽  
Author(s):  
W. Lee Perry ◽  
Joel D. Katz ◽  
Daniel Rees ◽  
Mark T. Paffett ◽  
Abhaya Datye
Keyword(s):  
Activation Energy ◽  
Carbon Monoxide ◽  
Co Oxidation ◽  
Microwave Heating ◽  
Oxidation Reaction ◽  
Reaction Order ◽  
Thermal Gradients ◽  
Exponential Factor ◽  
Co Oxidation Reaction ◽  
Kinetics Of

Abstract915 MHz microwave heating has been used to drive the CO oxidation reaction over Pd/Al2O3 without significantly affecting the reaction kinetics. As compared to an identical conventionally heated system, the activation energy, pre-exponential factor, and reaction order with respect to CO were unchanged. Temperature was measured using a thermocouple extrapolation technique. Microwave-induced thermal gradients were found to play a significant role in kinetic observations.

scholarly journals Determining Preexponential Factor in Model-Free Kinetic Methods: How and Why?

Molecules ◽  
2021 ◽  
Vol 26 (11) ◽  
pp. 3077
Author(s):  
Sergey Vyazovkin
Keyword(s):  
Activation Energy ◽  
Kinetic Analysis ◽  
Rate Constant ◽  
Condensed Phase ◽  
Compensation Effect ◽  
Preexponential Factor ◽  
Isoconversional Methods ◽  
Activation Entropy ◽  
Model Free ◽  
Kinetics Of

The kinetics of thermally stimulated processes in the condensed phase is commonly analyzed by model-free techniques such as isoconversional methods. Oftentimes, this type of analysis is unjustifiably limited to probing the activation energy alone, whereas the preexponential factor remains unexplored. This article calls attention to the importance of determining the preexponential factor as an integral part of model-free kinetic analysis. The use of the compensation effect provides an efficient way of evaluating the preexponential factor for both single- and multi-step kinetics. Many effects observed experimentally as the reaction temperature shifts usually involve changes in both activation energy and preexponential factor and, thus, are better understood by combining both parameters into the rate constant. A technique for establishing the temperature dependence of the rate constant by utilizing the isoconversional values of the activation energy and preexponential factor is explained. It is stressed that that the experimental effects that involve changes in the preexponential factor can be traced to the activation entropy changes that may help in obtaining deeper insights into the process kinetics. The arguments are illustrated by experimental examples.

scholarly journals Influence of coal properties on the co-combustion characteristics of low-grade coal and city mud

2014 ◽  
Vol 16 (2) ◽  
pp. 329-338 ◽  
Keyword(s):  
Activation Energy ◽  
Particle Size ◽  
Apparent Activation Energy ◽  
Frequency Factor ◽  
Combustion Characteristic ◽  
Low Grade ◽  
Mixing Ratio ◽  
Mixture Ratio ◽  
Characteristic Index ◽  
Carbon Burning

<div> <p>In this paper, the effects of the mixing ratio and particle size of coal were investigated using a thermogravimetric analysis (TGA). A method of Achar-Brindley-Sharp-Wendworth (ABSW) was applied to a simultaneous calculation of the kinetic parameters (including the apparent activation energy, the reaction order and the frequency factor). Meanwhile, this study also revealed that both the burning performance and the characteristic parameters improved when sludge mixing ratio was smaller (10 wt.%). The ignition temperature advanced with an increase of the sludge proportion, while the combustion characteristic index dropped. As the sludge mixture ratio rose to 70 wt.%, the DTG curve reached three peaks at 293 &deg;C, 580 &deg;C and 748 &deg;C Decreasing the coal particle size led to the advancement of the devolatilization, fixed carbon burning stage and maximum weight loss rate, and the reduction of the corresponding temperature. Additionally, the apparent activation energy and frequency factor of the mixture reduced when the proportion of the sludge mixing ratio went up. Also, the experiment results indicated that with the decline of the particle size distribution of coal, the apparent activation energy followed a downward trend, while the frequency factor increased.</p> </div> <p>&nbsp;</p>

scholarly journals Effect of the Particle Size of Iron Ore on the Pyrolysis Kinetic Behaviour of Coal-Iron Ore Briquettes

Energies ◽  
2018 ◽  
Vol 11 (10) ◽  
pp. 2595 ◽  
Author(s):  
Heng Zheng ◽  
Wei Wang ◽  
Runsheng Xu ◽  
Rian Zan ◽  
Johannes Schenk ◽  
...  
Keyword(s):  
Activation Energy ◽  
Particle Size ◽  
Synergistic Effect ◽  
Apparent Activation Energy ◽  
Conversion Rate ◽  
Iron Ore ◽  
High Reactivity ◽  
Particle Sizes ◽  
Low Carbon ◽  
Pyrolysis Behaviour

High reactivity coke is beneficial for achieving low carbon emission blast furnace ironmaking. Therefore, the preparation of highly reactive ferro-coke has aroused widespread attention. However, the effects of the particle size of iron ore on the pyrolysis behaviour of a coal-iron ore briquette are still unclear. In this study, the effect of three particle sizes (0.50–1.00 mm, 0.25–0.50 mm and <0.74 mm) of iron ore on the thermal and kinetic behaviours of coal-iron ore briquettes were investigated by non-isothermal kinetic analysis. The results showed that the synergistic effect of iron ore and coal during coking mainly occurred during the later reaction stage (850–1100 °C) and smaller particle sizes of iron ore have a stronger synergistic effect. The addition of iron ore had little effect on T0 (the initial temperature) and Tp (the temperature at the maximum conversion rate) of briquette pyrolysis, however itgreatly affected the conversion rate and Tf (the final temperature) of the briquettes. T0 decreased with the decrease of iron ore particle sizes, while Tp and Tf showed opposite trends. After adding iron ore into the coal briquette, the reaction kinetics at all stages of the coal-iron ore briquettes changed. The weighted apparent activation energy of the caking coal (JM) briquette was 35.532 kJ/mol, which is lower than that of the coal-iron ore briquettes (38.703–55.627 kJ/mol). In addition, the weighted apparent activation energy gradually increased with decreasing iron ore particle sizes.

Adsorption Kinetics of Uranium(VI) on Carboxylic Acid Fiber

2012 ◽  
Vol 550-553 ◽  
pp. 2625-2628 ◽  
Author(s):  
Yun Yi Lei ◽  
Wei Guo Cao ◽  
Kun Hua Lin ◽  
Ye Fei Jin
Keyword(s):  
Activation Energy ◽  
Carboxylic Acid ◽  
Apparent Activation Energy ◽  
Rate Constant ◽  
Adsorption Kinetics ◽  
Theoretical Basis ◽  
Nuclear Wastes ◽  
Kinetics Of ◽  
Langmuir And Freundlich Equations

The paper analyzed the adsorption conditions of uranium on carboxylic acid fiber. The isotherms were drawn, and Langmuir and Freundlich equations were deduced. The adsorption kinetics of UO22+on carboxylic fiber was researched. The rate constant of adsorption was obtained and the apparent activation energy was determined. This research provides a theoretical basis for new adsorbents of uranium in nuclear wastes.

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.

scholarly journals CORRELATION BETWEEN PREEXPONENTIAL FACTOR AND ACTIVATION ENERGY OF ISOAMYLALCOHOL HYDROGENOLYSIS ON PLATINUM CATALYSTS

2010 ◽  
Vol 4 (1) ◽  
pp. 1-5 ◽  
Author(s):  
Triyono Triyono
Keyword(s):  
Activation Energy ◽  
Rate Constant ◽  
Reaction Rate ◽  
Arrhenius Equation ◽  
Preexponential Factor ◽  
Active Centers ◽  
Exponential Term ◽  
Lower Activation ◽  
Higher Temperature ◽  
Lower Activation Energy

Arrhenius equation stated that reaction will proceed faster at higher temperature and with lower activation energy (Ea). Many literatures reported that preexponential factor (A) is constant for certain reaction and there is no relation between A and Ea. Experiment on the reaction of isoamylalcohol hydrogenolysis showed that logarithm of A increased linearly with Ea. The result of this investigation suggests that the rate of a process is affected by the number of active centers on the surface of a catalysts, which influences the value of the pre-exponential term in the expression for the rate constant of a reaction. An increase in the number of active centers corresponds to a higher value of A, the active centers would be less effective and is attended by a growth in the value of Ea. Therefore, reaction with lower activation energy will not always has higher reaction rate due to decreasing of Ea.   Keywords: isoamylalcohol hydrogenolysis, preexponential factor, activation  energy.

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