AZOXYCOMPOUNDS: I. THE PHOTOLYSIS OF AZOXYMETHANE

1964 ◽  
Vol 42 (8) ◽  
pp. 1936-1939 ◽  
Author(s):  
B. G. Gowenlock
Keyword(s):  
Activation Energy ◽  
Nitrous Oxide ◽  
Reaction Products ◽  
Kcal Mole

A study of the photolysis of azoxymethane has been made. The reaction products include nitrogen, nitrous oxide, methane, and ethane. The ratio N2:N2O is independent of temperature and two primary photolytic processes are postulated to account for this fact. On the assumption that methane arises from the reaction CH3 + CH3N2OCH3 → CH4 + CH2N2OCH3, the activation energy of this reaction is 6 ± 2 kcal/mole. Other reactions that take place during the photolysis are discussed.

The decomposition of nitrous oxide catalysed by palladium-gold alloy wires

1966 ◽  
Vol 294 (1436) ◽  
pp. 1-19 ◽  
Keyword(s):  
Activation Energy ◽  
Nitrous Oxide ◽  
Fermi Level ◽  
Apparent Activation Energy ◽  
Frequency Factor ◽  
Kcal Mole ◽  
Dissociative Chemisorption ◽  
Retarding Effect ◽  
Effect Of Oxygen ◽  
Decomposition Of Nitrous Oxide

The rate of decomposition of nitrous oxide has been examined by pressure measurements, at temperatures between 500 and 900 °C and pressures between 10 -2 and 1 torr. The reaction is first order, but shows retardation by oxygen, but not nitrogen. Over the range of alloys, from Pd to nearly 40 at. % Pd, the velocity at 650 °C falls by a factor of 104, the apparent activation energy falls from 30 to 13 kcal/mole, and the retarding effect of oxygen falls to zero. Over this range of alloys the Fermi level which lies in the d band hardly changes but the concentration of the d band vacancies falls to zero. Over the range of alloys from 40 at. % Pd to Au the velocity at 650 °C remains constant but the apparent activation energy and frequency factor, which show an abrupt increase at 40 at. % Pd, show a continuous fall. The retarding effect of oxygen remains zero. In this range the Fermi level has entered the s band and increases to Au. A steady state treatment of an irreversible dissociative chemisorption of nitrous oxide, together with an oxygen chemisorption equilibrium, yields an equation for the velocity in quantitative agreement with the results found. It is also possible to account for the increase in apparent activation energy with oxygen coverage of the surface. The heat of adsorption of oxygen is derived as 32-2±2 kcal/mole, and the activation energy for chemisorption of nitrous oxide as 12-7 ±0-5 kcal/mole.

REACTION OF OXYGEN ATOMS WITH ACETALDEHYDE

1956 ◽  
Vol 34 (6) ◽  
pp. 775-784 ◽  
Author(s):  
R. J. Cvetanović
Keyword(s):  
Activation Energy ◽  
Nitrous Oxide ◽  
Room Temperature ◽  
Primary Process ◽  
Kcal Mole ◽  
Decomposition Of Nitrous Oxide ◽  
Oxygen Atoms

Reaction of oxygen atoms, produced by mercury photosensitized decomposition of nitrous oxide, with acetaldehyde has been studied at room temperature. The major products of the reaction are water and biacetyl and the only primary process appears to be[Formula: see text]followed by[Formula: see text]and[Formula: see text]At room temperature oxygen atoms react with acetaldehyde 0.7 ± 0.1 times as fast as with ethylene, so that the activation energy of reaction [1] is likely to be close to 3 kcal./mole.

Kinetics of the thermal decomposition of propylene, and of propylene-inhibited hydrocarbon decompositions

1960 ◽  
Vol 259 (1297) ◽  
pp. 257-266 ◽  
Keyword(s):  
Activation Energy ◽  
Main Chain ◽  
Chain Termination ◽  
Reaction Products ◽  
Kcal Mole ◽  
Allyl Radical ◽  
Individual Reaction ◽  
Benzene Toluene ◽  
The Individual ◽  
Kinetics Of

The main products of the propylene decomposition, studied between 580 and 640°C, were found to be ethylene, methane and hydrogen, in the approximate ratio 2:2:1. Smaller amounts of ethane, propane, butenes, benzene, toluene and diallyl were found, but no allene was detected. The order of the reaction was 3/2, and the activation energy 56⋅7 kcal/mole. A mechanism is proposed, involving an initial split into C 3 H 5 + H and including abstractions by both CH 3 and H; the main chain-terminating step is H + C 3 H 5 . The mechanism is shown to predict the rates of formation of the individual reaction products, and to account satisfactorily for the observed activation energy. Hydrogen atom abstractions by the allyl radical were demonstrated. It is shown that the facts are consistent with the suggestion that in the propylene-inhibited paraffin decompositions there is H abstraction by C 3 H 5 and chain termination by reaction between C 3 H 6 and an alkyl radical. This proposal explains why NO and propylene give rise to the same rates for the fully inhibited reactions, and why smaller amounts of NO are required to produce a given degree of inhibition.

Temperature Dependent Intermixing At The V/Ge(111) Interface

1985 ◽  
Vol 54 ◽  
Author(s):  
M. Del Giudice ◽  
R. A. Butera ◽  
J. J. Joyce ◽  
M. W. Ruckman ◽  
J. H. Weaver
Keyword(s):  
Activation Energy ◽  
High Resolution ◽  
Grain Boundary ◽  
Diffusion Process ◽  
Boundary Diffusion ◽  
The Other ◽  
Reaction Products ◽  
Kcal Mole ◽  
Temperature Dependent ◽  
Heterogeneous Interfaces

ABSTRACTHigh resolution core level photoemission results show the temperature evolution of the V/Ge(111) interface in the range from 300 to 600 K. Three well-defined chemical environments are present for Ge at 300K (the first is the substrate and the other two are reaction products with overall shifts of−0.5 and −0.95 eV). Increasing the temperature enhances Ge outdiffusion, and a homogeneous reacted layer forms when deposition and measurements are done isothermally at 475K. The activation energy for this diffusion process is very low (5 kcal/mole), indicating the importance of grain boundary diffusion at reacting, heterogeneous interfaces.

REACTION OF OXYGEN ATOMS WITH TOLUENE

1961 ◽  
Vol 39 (12) ◽  
pp. 2444-2451 ◽  
Author(s):  
G. R. H. Jones ◽  
R. J. Cvetanović
Keyword(s):  
Activation Energy ◽  
Nitrous Oxide ◽  
Room Temperature ◽  
Kcal Mole ◽  
General Similarity ◽  
Decomposition Of Nitrous Oxide ◽  
Oxygen Atoms

The reaction of toluene with oxygen atoms produced by mercury photosensitized decomposition of nitrous oxide has been studied at room temperature. The reaction shows a general similarity to the corresponding reaction of benzene. Relative rates have been determined at 120 and 220 °C and the activation energy estimated at close to 4 kcal/mole.

The Chemistry of Vulcanization. V. Action of 2,2′-Benzothiazolyl Disulfide on the Reaction of Diphenylmethane and Sulfur

1958 ◽  
Vol 31 (4) ◽  
pp. 788-799 ◽  
Author(s):  
Jitsuo Tsurugi ◽  
Haruko Fukuda
Keyword(s):  
Activation Energy ◽  
Zinc Oxide ◽  
Reaction Mechanism ◽  
Rate Equation ◽  
Thermal Dissociation ◽  
Material Balance ◽  
Reaction Products ◽  
Kcal Mole ◽  
Near Future

Abstract The reaction involving diphenylmethane, sulfur and 2,2′-benzothiazoIyl disulfide is summarized as follows. A. The reaction products and material balance among them are indicated. B. A reaction mechanism was decided upon. C. The rate equation for MBTS consumption was derived from the above mechanism and the results interpreted satisfactorily. The activation energy for thermal dissociation of 2,2′-benzothiazolyl disulfide was found to be 32.7 kcal/mole. D. The accelerating efficiency of this accelerator was defined, discussed and evaluated. These studies are being continued and further communications on the studies of accelerators in the presence of zinc oxide or zinc soap will appear in the near future.

Vulcanization of Elastomers. 23. The Chemical Kinetics of Vulcanization Reactions and The Physical Properties of The Vulcanizates. I

1960 ◽  
Vol 33 (2) ◽  
pp. 335-341
Author(s):  
Walter Scheele ◽  
Karl-Heinz Hillmer
Keyword(s):  
Activation Energy ◽  
Physical Properties ◽  
Chemical Kinetics ◽  
Kcal Mole ◽  
First Order ◽  
Equilibrium Swelling ◽  
Kinetics Of ◽  
Kinetics Of Vulcanization ◽  
Limiting Value ◽  
Good Agreement

Abstract As a complement to earlier investigations, and in order to examine more closely the connection between the chemical kinetics and the changes with vulcanization time of the physical properties in the case of vulcanization reactions, we used thiuram vulcanizations as an example, and concerned ourselves with the dependence of stress values (moduli) at different degrees of elongation and different vulcanization temperatures. We found: 1. Stress values attain a limiting value, dependent on the degree of elongation, but independent of the vulcanization temperature at constant elongation. 2. The rise in stress values with the vulcanization time is characterized by an initial delay, which, however, is practically nonexistent at higher temperatures. 3. The kinetics of the increase in stress values with vulcanization time are both qualitatively and quantitatively in accord with the dependence of the reciprocal equilibrium swelling on the vulcanization time; both processes, after a retardation, go according to the first order law and at the same rate. 4. From the temperature dependence of the rate constants of reciprocal equilibrium swelling, as well as of the increase in stress, an activation energy of 22 kcal/mole can be calculated, in good agreement with the activation energy of dithiocarbamate formation in thiuram vulcanizations.

The slow oxidation of methane

1956 ◽  
Vol 235 (1201) ◽  
pp. 158-173 ◽  
Keyword(s):  
Activation Energy ◽  
Hydrogen Peroxide ◽  
Induction Period ◽  
Hydrofluoric Acid ◽  
Pressure Rise ◽  
Pressure Change ◽  
Kcal Mole ◽  
Gaseous Products ◽  
Oxidation Of Methane ◽  
Reproducible Manner

Mixtures of methane and oxygen behave in a reproducible manner at temperatures of 440 to 520°C and initial pressures of 100 to 350 mm when reacting in Pyrex vessels freshly cleaned with hydrofluoric acid. The apparent order of the reaction ranged from 2∙3 to 2∙6 and the overall activation energy from 29 to 41 kcal/mole. Analyses of the products formed have been made, together with measurements of pressure change. Formaldehyde is formed from the commencement of the reaction including the induction period, but its concentra­tion reaches a maximum near the stage where the pressure rise is a maximum, and then falls off. Hydrogen peroxide is also formed, less rapidly in the earliest stage, but its rate of formation overtakes that of formaldehyde and it reaches an even higher concentration. No other peroxides were detected, nor was methanol found. Hydrogen was present in the gaseous products. These observations are not in full accord with some of the conclusions derived from earlier investigations.

POLYMÉRISATION PAR LES RAYONS-X DU CHLORURE DE VINYLE À L'ÉTAT DE VAPEUR

1963 ◽  
Vol 41 (6) ◽  
pp. 1578-1587 ◽  
Author(s):  
Jan A. Herman ◽  
Pierre M. Hupin
Keyword(s):  
Activation Energy ◽  
Gas Phase ◽  
Average Molecular Weight ◽  
Negative Temperature ◽  
Solid Polymer ◽  
X Rays ◽  
Kcal Mole ◽  
Rate Of Polymerization ◽  
G Value ◽  
Termination Process

The polymerization of vinyl chloride in the gas phase by X rays gives a solid polymer of 1140 average molecular weight. The G value of monomer disappearance varies from 100 to 400 and depends on pressure and temperature. From the measure of the rate of polymerization it was possible to deduce the activation energy of the chain propagation steps: 2.5 kcal/mole, and that of the hindered termination process: 7.4 kcal/mole. The negative temperature co-efficient of the polymerization is explained by the importance of this hindered termination process.

Methanation on exfoliated and supported MoS2

1989 ◽  
Vol 67 (5) ◽  
pp. 862-866 ◽  
Author(s):  
Guenter A. Scholz ◽  
S. Roy Morrison
Keyword(s):  
Activation Energy ◽  
Carbon Monoxide ◽  
Transition Metal Catalysts ◽  
Surface Species ◽  
Reaction Products ◽  
Third Order ◽  
Ammonium Heptamolybdate ◽  
First Order ◽  
Methanation Reaction ◽  
Improved Performance

The methanation reaction on MoS2 exfoliated to a thickness of a few layers or less and adsorbed onto alumina is found to be very small. However, by calcining and resulfiding the exfoliated MoS2 catalysts, greatly improved performance is achieved that is at least equal to the commercial catalysts based on ammonium heptamolybdate. The creation of molybdenum oxysulflde surface species therefore appears to be a necessary step toward producing significant methanation rates with exfoliated and supported MoS2. The methanation products are almost exclusively CO2 and CH4, their mole ratios near unity, with otherwise only very much smaller amounts of longer chain hydrocarbons. The activation energy for methanation is generally observed to be near 100 kJ/mol, with the overall reaction being first order in the carbon monoxide concentration and third order in the hydrogen concentration. In contrast to the transition-metal catalysts, no water could be detected in the reaction products of the molybdenum based catalyst. Keywords: methanation reaction on MoS2, exfoliated and supported MoS2 as catalyst.

Sign in / Sign up

Export Citation Format

Share Document