Kinetic Study For The Formation Of The Oxygendeficient Magnetite

1994 ◽  
Vol 344 ◽  
Author(s):  
T. Togawa ◽  
Y. Wada ◽  
T. Yoshida ◽  
M. Tsuji ◽  
Y. Tamaura
Keyword(s):  
Partial Pressure ◽  
Kinetic Study ◽  
Rate Constant ◽  
Rate Constants ◽  
Arrhenius Equation ◽  
Reaction Order ◽  
Oxygen Deficiency ◽  
Reverse Reaction ◽  
Temperature Range ◽  
Reaction Orders

AbstractAn oxygendeficient magnetite (Fe3O4–8) has been found to exist in the range of (0<Δ<0.12) in the course of H2-reduction of magnetite to αFe at 300°C. The formation of the oxygendeficient magnetite was studied kinetically. In the temperature range of 250 350°C, the rate constants, k1, and k2, were determined for the forward and reverse reactions, respectively. The rate of formation of the oxygendeficient magnetite depended on the partial pressure of H2 gas. The rate constant, k1, was 109.58 at 300°C and the reaction order was 1.11 with respect to the partial pressure of H2 gas. The rate of reverse reaction depended on the partial pressure H2O gas and the oxygen deficiency of magnetite, Δ. The rate constant of the reverse reaction, k2, was 10−2.54 at 300°C, and the reaction orders were 0.45 and 0.99 with respect to the partial pressure of H2O gas and the Δ value respectively. The activation energies for the forward and reverse reactions were determined to be 63.8 kJ.mol−1 and 25.5 kJ.mol−1 from the Arrhenius' equation.

Reactions of methyl radicals. I. Hydrogen abstraction from dimethyl sulphide

1976 ◽  
Vol 29 (7) ◽  
pp. 1483 ◽  
Author(s):  
NL Arthur ◽  
M Lee
Keyword(s):  
Free Radicals ◽  
Rate Constant ◽  
Rate Constants ◽  
Hydrogen Abstraction ◽  
Reverse Reaction ◽  
Thermochemical Data ◽  
Methyl Radicals ◽  
Dimethyl Sulphide ◽  
Temperature Range

Hydrogen abstraction from (CH3),S and CH3COCH3 by CH3 radicals CH3+CH3SCH3 → CH4+CH3SCH2 CH3 + CH3COCH3 → CH4 + CH3COCH2 has been studied in the temperature range 120-245�. The rate constants, based on the value of 1013.34cm3 mol-l s-1 for the recombination of CH3 radicals, are given by (k in cm3 mol-1 s-1, E in kJ mol-1, R = 0.008314 kJ K-1 mol-1): logk1 = (11.62 � 0.08) ? (38.35 � 0.68)/2.303RT logk3 = (11.61 � 0.05) ? (40.48 � 0.46)/2.303RT Combination of the results for (1) with thermochemical data gives a calculated value of Logk-1 = (11.8 -63.7/2.303RT for the rate constant of the reverse reaction. The results for CH3+(CH3)2S are compared with all of the available data for hydrogen abstraction by free radicals from both sulphur-containing compounds, and molecules of the type (CH3)xM.

Reactions of trifluoromethyl radicals. I. Hydrogen abstraction from dimethyl sulphide

1972 ◽  
Vol 25 (4) ◽  
pp. 803 ◽  
Author(s):  
NL Arthur ◽  
KS Yeo
Keyword(s):  
Hydrogen Atom ◽  
Rate Constant ◽  
Hydrogen Abstraction ◽  
Reverse Reaction ◽  
Thermochemical Data ◽  
Hydrogen Atom Abstraction ◽  
Dimethyl Sulphide ◽  
Temperature Range

Hydrogen atom abstraction from (CH3)2S by CF3 radicals has been studied in the temperature range 79-167�: (1) CF3 + CH3SCH3 ←→ CF3H + CH3SCH2 (-1) The rate constant, based on Ayscough's value of 1013.36cmS mol-l s-l for the recombination of CF3 radicals, is given by (k1 in cm3 mol-1 s-l, E in J mol-l): Logk1 = (12.05 � 0.02)-(28710 � 130)/2.303RT Combination of these results with thermochemical data gives a calculated value of log k-1 = 12.2 - 62600/2.303RT for the rate constant of the reverse reaction. ΔH�f(CH3SCH2) and S�(CH3SCH2) are estimated to be 155.6 kJ mol-l and 290 J K-l mol-1 respectively.

The Rate-Constant for the Recombination of Methyl Radicals

1986 ◽  
Vol 39 (8) ◽  
pp. 1257 ◽  
Author(s):  
NL Arthur ◽  
JC Biordi
Keyword(s):  
Experimental Data ◽  
High Pressure ◽  
Rate Constant ◽  
Rate Constants ◽  
The Other ◽  
Methyl Radicals ◽  
Experimental Conditions ◽  
Temperature Range ◽  
Best Value ◽  
Limiting Value

Rate constants for the recombination of CH3 radicals have been measured by means of the rotating sector technique in the temperature range 373- 463 K, and at a pressure of 30 Torr . CH3 radicals were produced by the photolysis of acetone, and the experimental data were fitted to sector curves generated from Shepp's theory. The results give kb = (2.81�0.22)×1013 cm3 mol-1 s-1, which, under the chosen experimental conditions, is close to its high-pressure limiting value. A comparison is made with the other values of the rate constant reported in the literature, and a best value is suggested.

scholarly journals Use of the O2-Thiosemicarbazide System, for the Leaching of: Gold and Copper from WEEE & Silver Contained in Mining Wastes

Materials ◽  
2021 ◽  
Vol 14 (23) ◽  
pp. 7329
Author(s):  
Eduardo Cerecedo-Sáenz ◽  
Edgar A. Cárdenas-Reyes ◽  
Abner H. Rojas-Calva ◽  
Ma. Isabel Reyes-Valderrama ◽  
Ventura Rodríguez-Lugo ◽  
...  
Keyword(s):  
Partial Pressure ◽  
Environmental Pollution ◽  
Kinetic Study ◽  
Chemical Reaction ◽  
Electronic Equipment ◽  
Mining Wastes ◽  
Reagent Concentration ◽  
Market Effect ◽  
O2 Partial Pressure ◽  
Reaction Orders

Environmental pollution today is a latent risk for humanity, here the need to recycle waste of all kinds. This work is related to the kinetic study of the leaching of gold and copper contained in waste electrical and electronic equipment (WEEE) and silver contained in mining wastes (MW), using the O2-thiosemicarbazide system. The results obtained show that this non-toxic leaching system is adequate for the leaching of said metals. Reaction orders were found ranging from 0 (Cu), 0.93 (Ag), and 2.01 (Au) for the effect of the reagent concentration and maximum recoveries of 77.7% (Cu), 95.8% (Au), and 60% (Ag) were obtained. Likewise, the activation energies found show that the leaching of WEEE is controlled by diffusion (Cu Ea = 9.06 and Au Ea = 18.25 kJ/Kmol), while the leaching of MW (Ea = 45.55 kJ/Kmol) is controlled by the chemical reaction. For the case of stirring rate, it was found a low effect and only particles from WEEE and MW must be suspended in solution to proceed with the leaching. The pH has effect only at values above 8, and finally, for the case of MW, the O2 partial pressure has a market effect, going the Ag leaching from 33% at 0.2 atm up to 60% at a 1 atm.

scholarly journals Kinetic Study of CaCO3 Precipitation Accelerated by High Voltage Impulse

2021 ◽  
Vol 43 (2) ◽  
pp. 125-134
Author(s):  
Damha Kim ◽  
In-Soung Chang
Keyword(s):  
Rate Constant ◽  
High Voltage ◽  
Rate Constants ◽  
Reaction Order ◽  
Reaction Rate Constant ◽  
Formation Reaction ◽  
Different Temperatures ◽  
Synthetic Solution ◽  
Scale Control

Objectives : Determination of reaction order (n) and rate constants (k) of the CaCO<sub>3</sub> scale formation reaction that was accelerated by the HVI (high voltage impulse) induction.Methods : HVI was inducted to the synthetic solution containing 2.5 mM of Ca<sup>2+</sup> ion at different temperatures of 25, 40, 60℃. The concentration of Ca<sup>2+</sup> ion has been monitored as voltages of the HVI increased from 0 to 5, 10, 15 kV. Reaction order and the rate constants of the CaCO<sub>3</sub> formation reaction were determined with the experimental dataset of Ca<sup>2+</sup> concentration vs. time plots.Results and Discussion : The CaCO<sub>3</sub> formation was determined to follow two-molecules 2<sup>nd</sup> order reaction. The reaction rate constant, k increased as temperature and the applied voltages of HVI increased. The rate constant, k at 25℃ and 15 kV of HVI was 8.2×10<sup>-3</sup> L/(mmol･hr), which was 2.7 times greater than the k of the control at 25℃, 3.0×10<sup>-3</sup> L/(mmol･hr).Conclusions : The reaction of CaCO<sub>3</sub> formation was accelerated by HVI as the applied voltages of HVI increased, indicating that the HVI could be used as an alternative desalting technology for scale control.

scholarly journals Penentuan Konstanta Laju Pengeringan Coconut Chips

2021 ◽  
Vol 7 (1) ◽  
pp. 39-49
Author(s):  
Hary Kurniawan ◽  
Sukmawaty Sukmawaty ◽  
Ansar Ansar ◽  
Kurniawan Yuniarto ◽  
Murad Murad ◽  
...  
Keyword(s):  
Moisture Content ◽  
Water Content ◽  
Rate Constant ◽  
Rate Constants ◽  
Arrhenius Equation ◽  
Drying Rate ◽  
Initial Water Content ◽  
Thermogravimetric Method ◽  
Initial Water

This study aims to determine the drying rate constant of coconut chips using an oven. Coconut chips drying is carried out at drying temperatures of 50 ° C, 60 ° C and 70 ° C. Drying coconut chips has been conducted at an initial water content of 40-50% wb until it reached ± 10% wb. The change of moisture content was measured every 15 minutes, and the measurement of the water content was determined by the thermogravimetric method. Newton's model was used in determining the observation drying rate constant. Furthermore, the observation drying rate constant was applied to predict the drying rate constant as a function of temperature using the Arrhenius equation. The results showed that the predicted drying rate constants ranged from 0.0090 - 0.0130 minute-1. 

scholarly journals Absolute rate constant and O(<sup>3</sup>P) yield for the O(<sup>1</sup>D)+N<sub>2</sub>O reaction in the temperature range 227 K to 719 K

2008 ◽  
Vol 8 (20) ◽  
pp. 6261-6272 ◽  
Author(s):  
S. Vranckx ◽  
J. Peeters ◽  
S. A. Carl
Keyword(s):  
Rate Constant ◽  
Rate Constants ◽  
Room Temperature ◽  
Marked Decrease ◽  
Quantum Yields ◽  
Absolute Rate ◽  
Temperature Range ◽  
A Value ◽  
Relative Quantum ◽  
Absolute Rate Constant

Abstract. The absolute rate constant for the reaction that is the major source of stratospheric NOx, O(1D)+N2O → products, has been determined in the temperature range 227 K to 719 K, and, in the temperature range 248 K to 600 K, the fraction of the reaction that yields O(3P). Both the rate constants and product yields were determined using a recently-developed chemiluminescence technique for monitoring O(1D) that allows for higher precision determinations for both rate constants, and, particularly, O(3P) yields, than do other methods. We found the rate constant, kR1, to be essentially independent of temperature between 400 K and 227 K, having a value of (1.37±0.11)×10−10 cm3 s−1, and for temperatures greater than 450 K a marked decrease in rate constant was observed, with a rate constant of only (0.94±0.11)×10−10 cm3 s−1 at 719 K. The rate constants determined over the 227 K–400 K range show very low scatter and are significantly greater, by 20% at room temperature and 15% at 227 K, than the current recommended values. The fraction of O(3P) produced in this reaction was determined to be 0.002±0.002 at 250 K rising steadily to 0.010±0.004 at 600 K, thus the channel producing O(3P) can be entirely neglected in atmospheric kinetic modeling calculations. A further result of this study is an expression of the relative quantum yields as a function of temperature for the chemiluminescence reactions (kCL1)C2H + O(1D) → CH(A) + CO and (kCL2)C2H + O(3P) → CH(A) + CO, both followed by CH(A) → CH(X) + hν, as kCL1(T)/kCL2(T)=(32.8T−3050)/(6.29T+398).

scholarly journals Kinetic study of the methane dry (CO2) reforming reaction over the Ce0.70La0.20Ni0.10O2−δ catalyst

2020 ◽  
Vol 10 (8) ◽  
pp. 2652-2662 ◽  
Author(s):  
Lidia Pino ◽  
Cristina Italiano ◽  
Massimo Laganà ◽  
Antonio Vita ◽  
Vincenzo Recupero
Keyword(s):  
Partial Pressure ◽  
Kinetic Study ◽  
Fixed Bed ◽  
Dry Reforming ◽  
Fixed Bed Reactor ◽  
Co2 Reforming ◽  
Methane Dry Reforming ◽  
Kinetic Behaviour ◽  
Temperature Range

The kinetic behaviour of the Ce0.70La0.20Ni0.10O2−δ catalyst during the methane dry reforming reaction was investigated in a fixed bed reactor in the temperature range of 923–1023 K with the partial pressure of CH4 and CO2 ranging between 5 and 50 kPa.

Kinetic Study on the Reaction of YBa2Cu3Oy Powder with Water

2003 ◽  
Vol 17 (18n20) ◽  
pp. 3629-3635 ◽  
Author(s):  
F. C. Yu ◽  
C. H. Lin ◽  
C. M. Wang ◽  
H.-C. I. Kao
Keyword(s):  
Activation Energy ◽  
Kinetic Study ◽  
Surface Area ◽  
Rate Constant ◽  
Arrhenius Equation ◽  
Initial Rate ◽  
Initial Surface ◽  
Exponential Factor ◽  
Rate Law

The reaction of superconducting YBa 2 Cu 3 O y powder with water is studied kinetically. The initial rate law is found as [Formula: see text] where [S] o is the initial surface area of the solid, a and b is found to be 0.94 ± 0.02 and 0.318 ± 0.002, respectively. For 100.7 mg powder with a mean radius of 0.0265 mm at pH 7.00 and 298 K, R o is 2.21 × 10-4 mol · min -1. Using a = 1 and b = 0.3, the rate constant, k, obtained at 283, 298 and 313 K is 0.64, 1.84 and 4.91 × 10-3 mol · min -1 · cm -2 · M -0.3, respectively. The activation energy is 50.0 kJ · mol -1 and pre-exponential factor is 1.09 × 106 mol · min -1 · cm -2· M -0.3, as calculated from the Arrhenius equation.

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