Gas phase photolysis of 1-pentene and 1-pentene-d10 at 7.1 and 7.6 eV. Kinetic considerations

1978 ◽  
Vol 56 (10) ◽  
pp. 1435-1441 ◽  
Author(s):  
Andrzej Więckowski ◽  
Guy J. Collin
Keyword(s):  
Gas Phase ◽  
Isotope Effects ◽  
Distribution Functions ◽  
Static System ◽  
Hydrogen Atoms ◽  
Photochemical Process ◽  
Radical Decomposition ◽  
Energy Distribution Functions ◽  
Kinetics Of ◽  
Non Equilibrium

The gas phase photolysis of n-pentene was carried out in a static system using nitrogen resonance lines at [Formula: see text] and the bromine line at [Formula: see text] The mechanism for the photolysis was proposed and compared to what was concluded at 8.4 eV (147 nm, the xenon resonance line). The kinetics of the decomposition of the excited C3H5* radicals formed in the primary photochemical process and the C5H11* radicals formed by the addition of hydrogen atoms to the parent molecules were discussed. The investigations were extended to the n-C5D10 photolytic System. The observed decomposition rate constants of the excited pentyl radicals as well as the secondary non-equilibrium isotope effects agree with the data published earlier. It is concluded from these experiments that, at least at 7.6 eV, hot hydrogen atoms are produced.Only a small fraction of the C3H5* radicals décompose and yield aliène. At the same time the combined primary–secondary non-equilibrium isotope effects are much less than those calculated for the 'pure' primary isotope effects. To account for these observations, it is assumed that the C3H5* radicals are formed with a wide spread in the internal energies. Since the threshold of the decomposition of the excited C3H5* radical lies above its mean excess energy (calculated on the statistical basis), an analogy in the energy-distribution functions on the radicals activated photochemically and thermally may be suggested. If so, an inverse secondary isotope effect may contribute to the gross effect involved in the C3H5* radical decomposition.

Electron Energy Distribution Functions of Hydrogen: The Effect of Superelastic Vibrational Collisions and of the Dissociation Process

1979 ◽  
Vol 34 (5) ◽  
pp. 585-593 ◽  
Author(s):  
M. Capitelli ◽  
M. Dilonardo
Keyword(s):  
Boltzmann Equation ◽  
Energy Distribution ◽  
Electron Energy ◽  
Distribution Functions ◽  
Electron Energy Distribution ◽  
Hydrogen Atoms ◽  
Dissociation Process ◽  
Excitation Rate ◽  
The Boltzmann Equation ◽  
Energy Distribution Functions

Abstract Electron energy distribution functions (EDF) of molecular H2 have been calculated by numerically solving the Boltzmann equation including all the inelastic processes with the addition of superelastic vibrational collisions and of the hydrogen atoms coming from the dissociation process. The population densities of the vibrational levels have been obtained both by assuming a Boltz-mann population at a vibrational temperature different from the translational one and by solving a system of vibrational master equations coupled to the Boltzmann equation. The results, which have been compared with those corresponding to a vibrationally cold molecular gas, show that the inclusion of superelastic collisions and of the parent atoms affects the EDF tails without strongly modifying the EDF bulk. As a consequence the quantities affected by the EDF bulk, such as average and characteristic energies, drift velocity, 0-1 vibrational excitation rate are not too much affected by the inclusion of superelastic vibrational collisions and of parent atoms, while a strong influence is observed on the dissociation and ionization rate coefficients which depend on the EDF tail. Calculated dissociation rates, obtained by EDF's which take into account both the presence of vibrationally excited molecules and hydrogen atoms, are in satisfactory agreement with experimental results.

Heterogeneous Adsorption of Activated Carbon Nanofibers Synthesized by Electrospinning Polyacrylonitrile Solution

2006 ◽  
Vol 6 (11) ◽  
pp. 3577-3582
Author(s):  
Jae-Wook Lee ◽  
Hyun-Chul Kang ◽  
Wang-Geun Shim ◽  
Chan Kim ◽  
Kap-Seung Yang ◽  
...  
Keyword(s):  
Activated Carbon ◽  
Energy Distribution ◽  
Carbon Nanofibers ◽  
Distribution Functions ◽  
Significant Information ◽  
Activated Carbon Nanofibers ◽  
Equilibrium And Kinetics ◽  
Adsorption Energy Distribution Functions ◽  
Energy Distribution Functions ◽  
Kinetics Of

This study focuses on the adsorption properties of activated carbon nanofibers (CNFs) fabricated by electrospinning polyacrylonitrile solutions dissolved in dimethylformamide, followed by heat treatment at high activation temperatures (700, 750, 800 °C). The samples were characterized by BET, SEM, and XRD. In addition, the adsorption energy distribution functions of CNFs were analyzed by using the generalized nonlinear regularization method. Comparative analysis of energy distribution functions provided significant information on the energetic and structural heterogeneities of CNFs. Furthermore, an investigation of adsorption equilibrium and kinetics of methylene blue (MB) and congo red (CR) revealed that the adsorption capacity and kinetics of MB are much higher and faster than that of CR on a given sample. Our experimental and theoretical results suggest that the CNFs used in this work may be widely used as an adsorbent.

Photosensitization by Cd(3P0,1) atoms. III. Gas phase decomposition of cyclopentane

1976 ◽  
Vol 54 (1) ◽  
pp. 77-84 ◽  
Author(s):  
Bansi L. Kalra ◽  
Arthur R. Knight
Keyword(s):  
Gas Phase ◽  
Vapor Phase ◽  
Product Formation ◽  
Time Dependent ◽  
Primary Process ◽  
Phase Decomposition ◽  
Unimolecular Decomposition ◽  
Hydrogen Atoms ◽  
Volatile Products ◽  
Radical Decomposition

The triplet cadmium photosensitized decomposition of cyclopentane in the vapor phase has been studied at 355 °C and has been shown to give rise to cyclopentyl radicals and hydrogen atoms with close to unit efficiency in the primary process. Subsequent reactions of these species, including an important contribution from unimolecular decomposition of cyclopentyl radicals, yield the observed volatile products, hydrogen, methane, ethylene, ethane, propylene, and cyclopentene. As a result of significant olefin scavenging of H-atoms product yields are strongly time dependent. The system has been shown to be unaffected by addends. The temperature dependence of the rate of product formation is consistent with the known energetics of cyclopentyl radical decomposition.

scholarly journals Taming microwave plasma to beat thermodynamics in CO2 dissociation

2015 ◽  
Vol 183 ◽  
pp. 233-248 ◽  
Author(s):  
G. J. van Rooij ◽  
D. C. M. van den Bekerom ◽  
N. den Harder ◽  
T. Minea ◽  
G. Berden ◽  
...  
Keyword(s):  
Rayleigh Scattering ◽  
Microwave Plasma ◽  
Vibrational Excitation ◽  
Distribution Functions ◽  
Dissociative Excitation ◽  
Plasma Dynamics ◽  
Novel Approach ◽  
Process Energy ◽  
Energy Distribution Functions ◽  
Non Equilibrium

The strong non-equilibrium conditions provided by the plasma phase offer the opportunity to beat traditional thermal process energy efficiencies via preferential excitation of molecular vibrations. Simple molecular physics considerations are presented to explain potential dissociation pathways in plasma and their effect on energy efficiency. A common microwave reactor approach is evaluated experimentally with Rayleigh scattering and Fourier transform infrared spectroscopy to assess gas temperatures (exceeding 104 K) and conversion degrees (up to 30%), respectively. The results are interpreted on a basis of estimates of the plasma dynamics obtained with electron energy distribution functions calculated with a Boltzmann solver. It indicates that the intrinsic electron energies are higher than is favorable for preferential vibrational excitation due to dissociative excitation, which causes thermodynamic equilibrium chemistry to dominate. The highest observed energy efficiencies of 45% indicate that non-equilibrium dynamics had been at play. A novel approach involving additives of low ionization potential to tailor the electron energies to the vibrational excitation regime is proposed.

Reaction of methyl radicals with cis-butene-2

1969 ◽  
Vol 47 (16) ◽  
pp. 2987-3001 ◽  
Author(s):  
Nobuo Yokoyama ◽  
R. K. Brinton
Keyword(s):  
Gas Phase ◽  
Equilibrium Distribution ◽  
Methyl Radicals ◽  
Methyl Radical ◽  
Hydrogen Atoms ◽  
Radical Concentration ◽  
Radical Decomposition ◽  
Similar Temperature ◽  
Carbonyl Radical

Methyl radicals generated by di-t-butylperoxide pyrolysis interact at comparable rates with cis-butene-2 in the gas phase by both addition and hydrogen atom abstraction. The determination of the rate of these reactions was simplified by the addition of a large concentration of acetaldehyde to the system. The additive, a source of low activation energy abstractable hydrogen atoms, was effective in suppressing polymerization reactions, and in addition, maintained a high steady state methyl radical concentration as a result of the carbonyl radical decomposition. The rate constants, k5 and k6 for the reactions [5] and [6], were determined to be 4.5 × 1010exp (−7000/RT)and 1.8 × 1010exp (−7300/RT)[Formula: see text]cm3 mole−1 s−1, respectively, over the temperature range 126–163 °C. The butenyl radical formed in reaction [6] isomerizes much faster than its interaction with other species in the system, and the distribution of the various conformations is similar to the equilibrium distribution of the butenes at a similar temperature.

The thermally induced rearrangements of 2-vinyloxirane

1976 ◽  
Vol 54 (21) ◽  
pp. 3364-3376 ◽  
Author(s):  
Robert J. Crawford ◽  
Stuart B. Lutener ◽  
Robert D. Cockcroft
Keyword(s):  
Carbon Monoxide ◽  
Gas Phase ◽  
Isotope Effects ◽  
Kinetic Isotope Effects ◽  
Thermally Induced ◽  
Rate Determining Step ◽  
Kinetic Isotope ◽  
Carbonyl Ylide ◽  
Structural Isomerization ◽  
Kinetics Of

The kinetics of the gas phase thermolysis of 2-vinyloxirane (4) have been studied over the temperature range 270–310 °C. The racemization of chiral 4 occurs six times faster than the structural isomerization to 2,3-dihydrofuran, (E)- and (Z)-2-butenal, and 3-butenal. The butenals undergo a slow thermolysis to propene and carbon monoxide. cis-Deuterio- and trans-3-deuterio-vinyloxirane have been synthesized and their interconversion is slow. Deuterium kinetic isotope effects on mono- and dideuterio-4 suggest that for the formation of the butenals the rate determining step involves rupture of the oxirane C—O bond. The dihydrofuran is produced by thermolysis of the oxirane C—C bond. The preferred mechanistic interpretation is that a carbon–oxygen diradical serves as an intermediate for butenal formation, and that a carbonyl-ylide is involved in the formation of the dihydrofuran.The relative rates, at 307.4 °C, of cis–trans-5-isomerization:dihydrofuran formation:racemization: butenal formation for 3-deuterio-2-vinyloxirane are 1.0:0.88:40.2:5.94, respectively.

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