Pressure dependence of methyl radical combination reaction. Part II. Effect of temperature

1970 ◽  
pp. 1001 ◽  
Author(s):  
F. Casas ◽  
C. Previtali ◽  
J. Grotewold ◽  
E. A. Lissi
Keyword(s):  
Pressure Dependence ◽  
Effect Of Temperature ◽  
Methyl Radical

scholarly journals Effect of Temperature and Pressure on Segmental Relaxation in Polymethylphenylsiloxane

2003 ◽  
Vol 76 (5) ◽  
pp. 1106-1115 ◽  
Author(s):  
S. Pawlus ◽  
S. J. Rzoska ◽  
J. Ziolo ◽  
M. Paluch ◽  
C. M. Roland
Keyword(s):  
Molecular Weight ◽  
Glass Transition ◽  
Pressure Dependence ◽  
Activation Volume ◽  
Relaxation Times ◽  
Effect Of Temperature ◽  
Loss Peak ◽  
Glass Transition Temperatures ◽  
Segmental Relaxation ◽  
Temperature And Pressure

Abstract Segmental relaxation in a series of polymethylphenylsiloxanes (PMPS) was studied using dielectric spectroscopy. The measurements covered a temperature range of more than 40 deg at pressures from ambient to 115 MPa. The results confirmed that the shape of the loss peak is independent of temperature, pressure and molecular weight. Consequently, the Tg -scaled dependence of the relaxation times was also independent of molecular weight. The pressure dependence of the relaxation times was characterized by means of the activation volume. This quantity changes markedly with pressure at a given temperature. However, the activation volume at the respective glass transition temperatures of the PMPS are essentially invariant to molecular weight. Finally, we measured the dependence of Tg on pressure, with the results well-described by the Andersson equation.

Mathematical Modeling and Investigation on the Temperature and Pressure Dependency of Permeation and Membrane Separation Performance for Natural gas Treatment

2016 ◽  
Vol 11 (1) ◽  
pp. 7-10 ◽  
Author(s):  
Seyed Saeid Hosseini ◽  
Javad Aminian Dehkordi ◽  
Prodip K. Kundu
Keyword(s):  
Experimental Data ◽  
Pressure Dependence ◽  
Hollow Fiber ◽  
Hollow Fiber Membrane ◽  
Effect Of Temperature ◽  
Separation Performance ◽  
Gas Treatment ◽  
Pressure Dependency ◽  
Temperature And Pressure ◽  
Membrane Permeance

Abstract Due to special features, modules comprising asymmetric hollow fiber membranes are widely used in various industrial gas separation processes. Accordingly, numerous mathematical models have been proposed for predicting and analyzing the performance. However, majority of the proposed models for this purpose assume that membrane permeance remains constant upon changes in temperature and pressure. In this study, a mathematical model is proposed by taking into account non-ideal effects including changes in pressure and temperature in both sides of hollow fibers, concentration polarization and Joule-Thomson effects. Finite element method is employed to solve the governing equations and model is validated using experimental data. The effect of temperature and pressure dependency of permeance and separation performance of hollow fiber membrane modules is investigated in the case of CO2/CH4. The effect of temperature and pressure dependence of membrane permeance is studied by using type Arrhenius type and partial immobilization equations to understand which form of the equations fits experimental data best. Findings reveal that the prediction of membrane performance for CO2/CH4 separation is highly related to pressure and temperature; the models considering temperature and pressure dependence of membrane permeance match experimental data with higher accuracy. Also, results suggest that partial immobilization model represents a better prediction to the experimental data than Arrhenius type equation.

The catalytic fission of the carbon-nitrogen bond II. The reactions of ethylamine and hydrogen on evaporated metal films

1958 ◽  
Vol 244 (1238) ◽  
pp. 398-410 ◽  
Keyword(s):  
Pressure Dependence ◽  
Reaction Mechanisms ◽  
Metal Films ◽  
Activation Energies ◽  
Effect Of Temperature ◽  
Gold Films ◽  
Rate Determining Step ◽  
The Common ◽  
Nitrogen Bond ◽  
And Tungsten

The catalytic fission of the C—N bond of ethylamine in hydrogen led to two main reactions: platinum films favoured reaction I, to ammonia and ethane; nickel, palladium and gold films favoured reaction II, producing ammonia and diethylamine and also triethylamine by further reaction of the first products. Both types of reaction occurred on rhodium and tungsten films. The effect of temperature was studied and the values of the activation energies indicated that the fission of the C—N bond was the common rate-determining step for the various pro­cesses. Increase of pressure of ethylamine caused reaction II to occur on platinum films and eventually to predominate over reaction I. Although the rate of fission of the C—N bond on platinum was not influenced by the pressure of ethylamine, the ratio of the rates of reaction II and I depended on the second power of this pressure. Reaction mechanisms are discussed and the pressure dependence of the rates on platinum considered in terms of differing types of adsorption of the amine. The activity of the various catalysts is compared and discussed with regard to their ability to break the C—N bond in ethylamine. It was found that ethylamine was more easily decomposed than methylamine on all the metals which were common to this investigation and to the previous work on the decomposition of methylamine.

Effect of temperature on methyl radical generation over Sr/La2O3 catalysts

1991 ◽  
Vol 11 (3-6) ◽  
pp. 295-300 ◽  
Author(s):  
Mingting Xu ◽  
Jack H. Lunsford
Keyword(s):  
Effect Of Temperature ◽  
Methyl Radical ◽  
Radical Generation

Mercury-photosensitized decomposition of dimethyl ether. Part III. The combination of radicals

1967 ◽  
Vol 45 (22) ◽  
pp. 2775-2783 ◽  
Author(s):  
Leon F. Loucks
Keyword(s):  
Dimethyl Ether ◽  
Rate Constant ◽  
Pressure Dependence ◽  
Rate Coefficient ◽  
Methyl Radicals ◽  
Methyl Ethyl ◽  
Methyl Radical ◽  
Unimolecular Decomposition ◽  
Third Body ◽  
Methyl Ethyl Ether

As part of the study of the mercury-photosensitized decomposition of dimethyl ether, the combination of methyl radicals has been investigated in the temperature range 200 to 300 °C and at pressures between 3 and 300 mm Hg. For pressures of less than 100 mm the second-order rate coefficient for the combination of methyl radicals shows a pressure dependence. The pressure dependence agrees qualitatively with that observed by others, but occurs at somewhat higher pressures. Calculations for the Kassel equation using the Arrhenius parameters for ethane decomposition and fitted to the pressure dependence of the methyl radical combination show that the number of effective modes for ethane decomposition is 8 or 9. Carbon dioxide was found to be a quite ineffective third body for energy transfer. The results for the mercury-photosensitized decomposition of dimethyl ether have also been analyzed to obtain information about the combination of methyl radicals with methoxymethyl radicals. The combination of these radicals becomes pressure dependent at pressures less than about 15 mm. Kassel integrations based on the rate constant [Formula: see text]for the unimolecular decomposition of methyl ethyl ether at the C—C bond, and fitted to the observed pressure dependence of the combination reaction, lead to s = 10 for these reactions.The rate constant for the abstraction of a hydrogen atom by a methyl radical from dimethyl ether was found to be [Formula: see text]

Nucleation of Disorder in Fe3Al Alloys

1967 ◽  
Vol 25 ◽  
pp. 312-313
Author(s):  
P. R. Swann ◽  
W. R. Duff ◽  
R. M. Fisher
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Annealing Temperature ◽  
Antiphase Domain ◽  
Effect Of Temperature ◽  
Domain Structures ◽  
Transmission Electron ◽  
Domain Boundaries ◽  
Higher Temperature ◽  
The One

Recently we have investigated the phase equilibria and antiphase domain structures of Fe-Al alloys containing from 18 to 50 at.% Al by transmission electron microscopy and Mössbauer techniques. This study has revealed that none of the published phase diagrams are correct, although the one proposed by Rimlinger agrees most closely with our results to be published separately. In this paper observations by transmission electron microscopy relating to the nucleation of disorder in Fe-24% Al will be described. Figure 1 shows the structure after heating this alloy to 776.6°C and quenching. The white areas are B2 micro-domains corresponding to regions of disorder which form at the annealing temperature and re-order during the quench. By examining specimens heated in a temperature gradient of 2°C/cm it is possible to determine the effect of temperature on the disordering reaction very precisely. It was found that disorder begins at existing antiphase domain boundaries but that at a slightly higher temperature (1°C) it also occurs by homogeneous nucleation within the domains. A small (∼ .01°C) further increase in temperature caused these micro-domains to completely fill the specimen.

The effect of temperature on high-resolution TEM image contrast

1995 ◽  
Vol 53 ◽  
pp. 640-641
Author(s):  
T. Geipel ◽  
W. Mader ◽  
P. Pirouz
Keyword(s):  
Form Factor ◽  
Inelastic Scattering ◽  
Accurate Method ◽  
Waller Factor ◽  
Effect Of Temperature ◽  
Specimen Thickness ◽  
Influence Of Temperature ◽  
Debye Waller Factor ◽  
Influence Of Temperature On ◽  
Atomic Form Factor

Temperature affects both elastic and inelastic scattering of electrons in a crystal. The Debye-Waller factor, B, describes the influence of temperature on the elastic scattering of electrons, whereas the imaginary part of the (complex) atomic form factor, fc = fr + ifi, describes the influence of temperature on the inelastic scattering of electrons (i.e. absorption). In HRTEM simulations, two possible ways to include absorption are: (i) an approximate method in which absorption is described by a phenomenological constant, μ, i.e. fi; - μfr, with the real part of the atomic form factor, fr, obtained from Hartree-Fock calculations, (ii) a more accurate method in which the absorptive components, fi of the atomic form factor are explicitly calculated. In this contribution, the inclusion of both the Debye-Waller factor and absorption on HRTEM images of a (Oll)-oriented GaAs crystal are presented (using the EMS software.Fig. 1 shows the the amplitudes and phases of the dominant 111 beams as a function of the specimen thickness, t, for the cases when μ = 0 (i.e. no absorption, solid line) and μ = 0.1 (with absorption, dashed line).

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