Reactions of thiyl radicals. II. The photolysis of methyl disulfide vapor

1967 ◽  
Vol 45 (12) ◽  
pp. 1369-1374 ◽  
Author(s):  
P. M. Rao ◽  
J. A. Copeck ◽  
A. R. Knight
Keyword(s):  
Nitric Oxide ◽  
Activation Energy ◽  
Apparent Activation Energy ◽  
Pressure Range ◽  
Excess Energy ◽  
Inert Gases ◽  
Effect Of Temperature ◽  
Primary Process ◽  
Direct Production ◽  
Thiyl Radicals

The photolysis of methyl disulfide vapor in the pressure range 2–25 Torr at wavelengths between 2 300 and 2 800 and at 2 288 Å has been examined and the effect of temperature, pressure, added inert gases, ethyl disulfide, and nitric oxide determined.The primary process is a direct production of two CH3S radicals which have excess energy and which can be observed as methyl thionitrite when NO is present during the decomposition. When pure disulfide is photolyzed the major observable product is methanethiol, although this material accounts for only a small fraction of the primarily produced thiyl radicals whose principal fate is recombination in a substrate-reforming reaction producing excited disulfide molecules. The latter species are deactivated by added gases, or by the substrate itself. The mode of mercaptan formation is by abstraction of H atoms from the substrate by excited CH3S radicals with an apparent activation energy of 1.5 kcal.

THE KINETICS OF CUPRENE GROWTH

1950 ◽  
Vol 28b (7) ◽  
pp. 358-372
Author(s):  
Cyrias Ouellet ◽  
Adrien E. Léger
Keyword(s):  
Nitric Oxide ◽  
Activation Energy ◽  
Carbon Monoxide ◽  
Apparent Activation Energy ◽  
Copper Catalyst ◽  
Maximum Velocity ◽  
Static System ◽  
Reaction Velocity ◽  
First Order ◽  
Kinetics Of

The kinetics of the polymerization of acetylene to cuprene on a copper catalyst between 200° and 300 °C. have been studied manometrically in a static system. The maximum velocity of the autocatalytic reaction shows a first-order dependence upon acetylene pressure. The reaction is retarded in the presence of small amounts of oxygen but accelerated by preoxidation of the catalyst. The apparent activation energy, of about 10 kcal. per mole for cuprene growth between 210° and 280 °C., changes to about 40 kcal. per mole above 280 °C. at which temperature a second reaction seems to set in. Hydrogen, carbon monoxide, or nitric oxide has no effect on the reaction velocity. Series of five successive seedings have been obtained with cuprene originally grown on cuprite, and show an effect of aging of the cuprene.

scholarly journals Effect of Temperature on the Creep of Ice

1969 ◽  
Vol 8 (52) ◽  
pp. 131-145 ◽  
Author(s):  
Malcolm Mellor ◽  
Richard Testa
Keyword(s):  
Activation Energy ◽  
Creep Rate ◽  
Single Crystal ◽  
Apparent Activation Energy ◽  
Creep Curve ◽  
Effect Of Temperature ◽  
Temperature Dependent ◽  
Creep Tests ◽  
Polycrystalline Ice ◽  
Rate Relation

Creep tests on homogeneous, isotropic polycrystalline ice gave an apparent activation energy for creep of 16.4 kcal/mol (68.8 kJ/mol) over the temperature range −10° to −60° C. Above −10° C the Arrhenius relation for temperature dependence is invalid, and creep rate becomes progressively more temperature dependent as the melting point is approached. Between −20° and −50° C the apparent activation energy for creep of a single crystal of ice was found to be 16.5 kcal/mol (69.1 kJ/mol). A complete creep curve for a single crystal loaded in uniaxial compression parallel to the basal plane was qualitatively similar to the classical creep curve; creep rate at all stages was very much faster than for polycrystalline ice under the same conditions. Creep tests on polycrystalline ice at 0° C gave a stress/strain-rate relation for that temperature, but its precise meaning is unclear, since recrystallization complicated the results.

Creep and Creep Recovery of 2618-T61 Aluminum Under Variable Temperature

1984 ◽  
Vol 51 (4) ◽  
pp. 816-820 ◽  
Author(s):  
U. W. Cho ◽  
W. N. Findley
Keyword(s):  
Activation Energy ◽  
Aluminum Alloy ◽  
Apparent Activation Energy ◽  
Variable Temperature ◽  
Constant Stress ◽  
Temperature History ◽  
Effect Of Temperature ◽  
Creep Recovery ◽  
Dependent Theory ◽  
Using Data

Creep and creep recovery data are reported for pure tension of 2618-T61 aluminum alloy under variable temperature between 200° C and 230° C. Varying temperature experiments involved an abrupt temperature increase and a linearly increasing and decreasing temperature at a constant stress of 137.9 MPa (20 ksi). A temperature-compensated time by Sherby and Dorn was employed to represent the effect of temperature. A temperature-history-dependent theory using data from constant stress creep and creep recovery together with the apparent activation energy was used to predict the creep under variable temperature. The predictions agreed quite well with the observed data. The apparent activation energy of this alloy was found to be 49,000 cal/mole°K.

scholarly journals Effect of Temperature on the Creep of Ice

1969 ◽  
Vol 8 (52) ◽  
pp. 131-145 ◽  
Author(s):  
Malcolm Mellor ◽  
Richard Testa
Keyword(s):  
Activation Energy ◽  
Creep Rate ◽  
Single Crystal ◽  
Apparent Activation Energy ◽  
Creep Curve ◽  
Effect Of Temperature ◽  
Temperature Dependent ◽  
Creep Tests ◽  
Polycrystalline Ice ◽  
Rate Relation

Creep tests on homogeneous, isotropic polycrystalline ice gave an apparent activation energy for creep of 16.4 kcal/mol (68.8 kJ/mol) over the temperature range −10° to −60° C. Above −10° C the Arrhenius relation for temperature dependence is invalid, and creep rate becomes progressively more temperature dependent as the melting point is approached. Between −20° and −50° C the apparent activation energy for creep of a single crystal of ice was found to be 16.5 kcal/mol (69.1 kJ/mol). A complete creep curve for a single crystal loaded in uniaxial compression parallel to the basal plane was qualitatively similar to the classical creep curve; creep rate at all stages was very much faster than for polycrystalline ice under the same conditions. Creep tests on polycrystalline ice at 0° C gave a stress/strain-rate relation for that temperature, but its precise meaning is unclear, since recrystallization complicated the results.

scholarly journals Effect of Temperature and pH on Early Hydration Rate and Apparent Activation Energy of Alkali-Activated Slag

2019 ◽  
Vol 2019 ◽  
pp. 1-13
Author(s):  
Ping Li ◽  
Jianhui Tang ◽  
Xudong Chen ◽  
Yin Bai ◽  
Qiyao Li
Keyword(s):  
Activation Energy ◽  
Apparent Activation Energy ◽  
Effect Of Temperature ◽  
Early Hydration ◽  
Alkali Activated Slag ◽  
Hydration Rate ◽  
Different Temperatures ◽  
Shell Forming ◽  
Activated Slag ◽  
Alkali Activated

In order to investigate the effect of temperature and pH on the early hydration rate of alkali-activated slag (AAS), NaOH was used as alkali activator, and the nonevaporable water (NEW) content of the slag paste at different temperatures (5, 20 and 35°C) and pH (12.10, 12.55, 13.02, and 13.58) was measured. On the basis of the Arrhenius formula, the hydration rate of slag was characterized by the content of nonevaporative water, and the apparent activation energy of slag hydration at different pH was also obtained. The early hydration rate of slag was significantly affected by temperature and pH of activator solution. The apparent activation energy Ea of slag decreased with the increase of pH, and there was a good linear relationship between them. When pH was less than 13.02, increasing the temperature can accelerate the hydration rate of slag. However, under the condition of high pH (pH = 13.58), the hydration rate of slag was negatively correlated with temperature, which was related to the “shell forming” phenomenon of slag hydration.

scholarly journals Experimental Study on the Inhibition Effects of Nitrogen and Carbon Dioxide on Coal Spontaneous Combustion

Energies ◽  
2020 ◽  
Vol 13 (20) ◽  
pp. 5256
Author(s):  
Yi Zhang ◽  
Jun Xu ◽  
Deming Wang
Keyword(s):  
Activation Energy ◽  
Apparent Activation Energy ◽  
Spontaneous Combustion ◽  
Inert Gases ◽  
Coal Spontaneous Combustion ◽  
Inhibition Effect ◽  
Burn Out ◽  
O2 Concentration ◽  
Temperature Combustion ◽  
High Temperature Combustion

Inert gases can effectively inhibit coal spontaneous combustion. In this paper, the inhibition effect of inert gases (N2 and CO2) on coal spontaneous combustion was studied. In the low-temperature oxidation stage, the constant-temperature heat release and apparent activation energy of coal sample were measured and calculated by the C80 micro-calorimeter. In the high-temperature combustion stage, the critical temperature, maximum peak temperature, ignition temperature, and burn-out temperature of coal samples were analyzed by the synchronous thermal analyzer. The results demonstrate that with the decrease of O2 concentration, the oxidation heat release of coal samples drops gradually while the apparent activation energy increases gradually. In the N2 and CO2 atmospheres, as the O2 concentration is reduced to 1.5% and 3%, respectively, the value of apparent activation energy changes from negative to positive, and the spontaneous reaction transits to a nonspontaneous reaction. The TG-DTG (thermogravimetric-derivative thermogravimetric) curve of coal sample in the high-temperature combustion stage indicates that the critical temperature exhibits a W-shaped trend with the decrease of O2 concentration, which also leads to gradual increases of maximum peak temperature, ignition temperature, and burn-out temperature. The above results signify that increasing the inert gas concentration can gradually reduce the oxidation and combustion rate and improve the inhibition effect on coal spontaneous combustion. In addition, when the O2 concentration is the same, the inhibition effect of CO2 on coal spontaneous combustion is superior to that of N2.

THE MERCURY PHOTOSENSITIZED REACTIONS OF NITRIC OXIDE

1952 ◽  
Vol 30 (3) ◽  
pp. 194-202 ◽  
Author(s):  
J. D. Mcgilvery ◽  
C. A. Winkler
Keyword(s):  
Nitric Oxide ◽  
Vapor Pressure ◽  
Pressure Range ◽  
Mercury Vapor ◽  
Low Pressure ◽  
Primary Process ◽  
Light Filters ◽  
Photochemical Decomposition ◽  
Mercury Vapor Pressure ◽  
Oxygen Atoms

The photochemical decomposition of nitric oxide has been studied over a pressure range 60 to 500 mm., using a low pressure mercury arc source and a circulating system. Stoichiometrically, the reaction was found to be represented by 6NO → N2 + 2N2O3. Addition of nitrogen decreased the rate, as did also a decrease in the mercury vapor pressure. Using appropriate light filters at 1.7 × 10−3 mm. mercury pressure the decomposition was shown to be photosensitized by Hg (61P1) atoms. The primary process is probably dissociation of nitric oxide into nitrogen and oxygen atoms.

scholarly journals Photodegradation of Rhodamine B Using the Microwave/UV/H2O2: Effect of Temperature

2013 ◽  
Vol 2013 ◽  
pp. 1-12 ◽  
Author(s):  
Carlo Ferrari ◽  
H. Chen ◽  
R. Lavezza ◽  
C. Santinelli ◽  
I. Longo ◽  
...  
Keyword(s):  
Activation Energy ◽  
Hydrogen Peroxide ◽  
Apparent Activation Energy ◽  
Rhodamine B ◽  
Effect Of Temperature ◽  
Microwave Source ◽  
Uv Emission ◽  
Linear Behavior ◽  
C 30 ◽  
Few Data

The oxidative decoloration of Rhodamine B (RhB) was performed in a photochemical reactor which enables microwave (MW) and UV radiation to be applied simultaneously. We used an immersed microwave source, with no need for an oven. Controlling the temperature, MW power, and UV emission of the reactor all led to a greater overall control of the process. Due to the action of highly reactive hydroxyl radicals, the decoloration of RhB was followed online using a spectrograph. Complete decoloration occurred in four minutes, and 92% of mineralisation was obtained in 70 minutes. The experiments were performed at various temperatures (21°C, 30°C, 37°C, and 46°C), with and without hydrogen peroxide. The apparent reaction rate was used to calculate the apparent activation energy of the decoloration process:Ea=38±2 kJ/mol and40±2 kJ/mol with (400 mg/L) or without hydrogen peroxide, respectively. The lack of deviation from the linear behavior of the Arrhenius plot confirms that the application of MW does not affect theEaof the process. The apparent activation energy value found was compared with the few data available in the literature, which were obtained in the absence of MW radiation and are inconsistent.

scholarly journals Crystallization Kinetics of α-Hemihydrate Gypsum Prepared by Hydrothermal Method in Atmospheric Salt Solution Medium

Crystals ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 843
Author(s):  
Zhongqi Wei ◽  
Qin Zhang ◽  
Xianbo Li
Keyword(s):  
Activation Energy ◽  
Apparent Activation Energy ◽  
Hydrothermal Method ◽  
Crystallization Kinetics ◽  
Calcium Sulfate ◽  
Control Process ◽  
Effect Of Temperature ◽  
Model Calculations ◽  
Crystallization Curve ◽  
Kinetics Of

α-Calcium sulfate hemihydrate (α-HH) is an important cementitious material, which can be prepared by hydrothermal method from calcium sulfate dihydrate (DH) in an electrolyte solution. Study of the conversion kinetics of DH to α-HH in NaCl solution is helpful for understanding the control process. In this paper, X-ray diffraction (XRD) patterns were applied to study the effect of temperature on the crystallization kinetics of α-HH to determine the kinetic parameters. The research results show that the sigmoidal shape of the α-HH crystallization curve follows the Avrami-Erofeev model, which describes the crystallization kinetics of α-HH formation. Applying Arrhenius law in experimental data and model calculations, an apparent activation energy of 124 kJ/mol for nucleation and an apparent activation energy of 810 kJ/mol for growth were obtained. By adjusting the temperature of the solution, the number of α-HH nucleation and growth steps increases, which can effectively increase the DH-α-HH conversion rate in the NaCI solution.

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