Reactions of hydrogen atoms and aliphatic radicals with monovalent cadmium and nickel ions as a source of hydrogen yield in some radiation chemical systems

1977 ◽  
Vol 73 (0) ◽  
pp. 622 ◽  
Author(s):  
Mira Freiberg ◽  
Dan Meyerstein
Keyword(s):  
Hydrogen Yield ◽  
Hydrogen Atoms ◽  
Radiation Chemical ◽  
Nickel Ions ◽  
Chemical Systems

RADIATION CHEMISTRY OF CYCLOHEXANE: VI. DILUTE SOLUTIONS OF CARBON TETRACHLORIDE AND CHLOROFORM IN CYCLOHEXANE

1964 ◽  
Vol 42 (3) ◽  
pp. 669-681 ◽  
Author(s):  
J. A. Stone ◽  
P. J. Dyne
Keyword(s):  
Carbon Tetrachloride ◽  
Chemical Reaction ◽  
Physical Process ◽  
Radical Scavenging ◽  
Radiation Chemistry ◽  
Hydrogen Yield ◽  
Halogenated Compounds ◽  
Dilute Solutions ◽  
Hydrogen Atoms

A study of the effect of the addition of small amounts (<3.5%) of the halogenated compounds CCl4, CHCl3, and CDCl3 on the radiolysis of cyclohexane has shown that processes other than radical scavenging occur. At the lowest concentrations of solute that it was practical to employ (0.004 M) cyclohexyl radicals were scavenged without a corresponding reduction in the hydrogen yield. At higher solute concentrations G(H2) was reduced by a physical process which did not involve the scavenging of thermal hydrogen atoms but did lead to chemical reaction involving the solute.

scholarly journals Photolysis of HNCO vapor in the presence of NO and O2

1968 ◽  
Vol 46 (4) ◽  
pp. 531-534 ◽  
Author(s):  
R. A. Back ◽  
R. Ketcheson
Keyword(s):  
Steady Increase ◽  
Hydrogen Yield ◽  
Mercury Lamp ◽  
Hydrogen Atoms ◽  
Medium Pressure ◽  
Absorption Of Light

The effect of NO at pressures up to 380 Torr on the photolysis of HNCO vapor (4.5 Torr) by light from an unfiltered medium-pressure mercury lamp has been studied at 37 °C. The yield of CO was reduced to about half its original value, which is attributed to reactions of NH and NCO with NO. The yield of N2 showed a steady increase with increasing NO pressure, probably due to reactions of NO(A2∑+) excited by absorption of light. The hydrogen yield fell rapidly to zero as the NO pressure was increased.Added oxygen at pressures up to 5 Torr had no effect on the CO and N2 production at 37 °C; at 110 °C the CO yield decreased somewhat while the N2 remained unaffected. These observations suggest that NH and NCO do not react readily with O2. The production of H2 fell rapidly to zero with increasing O2 pressure at both temperatures. The suppression of H2 formation by both NO and O2 supports the belief that it is formed by reactions of hydrogen atoms.

Radiolysis of methylcyclohexane. III. Pure vapor phase and effects of additives

1967 ◽  
Vol 45 (14) ◽  
pp. 1649-1659 ◽  
Author(s):  
W. J. Holtslander ◽  
G. R. Freeman
Keyword(s):  
Vapor Phase ◽  
Secondary Reaction ◽  
Hydrogen Yield ◽  
Methyl Radicals ◽  
Hydrogen Atoms ◽  
Hydrogen Formation ◽  
Positive Ions ◽  
Total Ionization ◽  
Different Types ◽  
Increasing Temperature

The radiolysis of methylcyclohexene (MCH) vapor was carried out under a variety of conditions. The G-values of the main products at 110°, extrapolated to zero dose, are hydrogen (5.2), methylcyclohexene isomers (2.0), ethylene (1.5), methane (1.3), propylene (0.8), and total dimer (0.3). Other products were also measured.The hydrogen yield was reduced to G = 3.1 by each of the additives, N2O, SF6, and CCL4, and to G = 1.6 by C2H4. Both DI and ND3 increased the total hydrogen yield above the value in pure MCH. In pure MCH approximately 50% of the ions (G(total ionization) = 4.4) resulted in hydrogen formation, whereas in the presence of DI or ND3, 75% of the ions are hydrogen precursors. Thus three different types of positive ions are distinguished in the system: G(M1+) = 2.1, G(M2+) = 1.3, and G(N+) = 1.0.The average ion lifetime with respect to neutralization was 10−3 s. The ion DI−was therefore stable with respect to decomposition to D + I− for a period greater than 10–3 s under the conditions of the experiments (~380 Torr MCH, 110°).The yield of methylcyclohexene isomers increased with increasing temperature and increased upon addition of ND3 or C2H4 to the radiolysis system. The dimer yield was also enhanced by the addition of ND3. This effect was explained by the occurrence of an ionic secondary reaction that destroys methylcyclohexene and (or) methylcyclohexyl radicals in pure MCH.Approximately 85% of the methane is produced by methyl radicals abstracting hydrogen atoms from MCH.

Hydrogen Production from Ethanol. Comparing Thermal Catalytic Reactions to Photo-catalytic Reactions.

2011 ◽  
Vol 1326 ◽  
Author(s):  
M. Scott ◽  
A.M. Nadeem ◽  
G.I.W. Waterhouse ◽  
H. Idriss
Keyword(s):  
Hydrogen Production ◽  
Thermal Activation ◽  
Room Temperature ◽  
Complete Removal ◽  
Catalytic Reactions ◽  
Hydrogen Yield ◽  
Hydrogen Atoms ◽  
Catalytic Systems ◽  
Thermally Activated ◽  
Sustainable System

ABSTRACTHydrogen production from renewables such as bio-ethanol is one of the most promising processes for energy carriers in a sustainable way. In this work we review and compare two catalytic systems: one based on thermal activation over bimetallic catalysts (Rh-Pd/CeO2) and the other over photo-excited semiconductor catalysts (Au/TiO2 anatine, rutile and anatase/rutile). It is found that the hydrogen yield is far higher on the thermally activated catalysts (at 773K) when compared to that of the photo-exited catalysts (at room temperature); about 60 times. However, the photo-excited catalysts are a promising way to create a fully sustainable system for future applications if the complete removal of hydrogen atoms from water and ethanol are obtained at room temperature.

The X-radiolysis of water vapor containing methanol. Effects of some electron and hydrogen atom scavengers

1968 ◽  
Vol 46 (12) ◽  
pp. 1957-1964 ◽  
Author(s):  
R. S. Dixon ◽  
M. G. Bailey
Keyword(s):  
Nitrous Oxide ◽  
Water Vapor ◽  
Carbon Tetrachloride ◽  
Hydrogen Atom ◽  
Sulfur Hexafluoride ◽  
Hydrogen Yield ◽  
Hydrogen Atoms ◽  
A Value ◽  
Ion Recombination ◽  
Positive Ion

The X-radiolysis of water vapor containing methanol at 125 °C and 1 atm pressure has been studied alone and in the presence of some electron and hydrogen atom scavengers. In water vapor containing methanol only, a plateau value G(H2) = 7.9 ± 0.3 is obtained at all methanol concentrations above 0.5 mole %. Addition of propylene drastically reduces this yield due to efficient scavenging of hydrogen atoms, and values for the total number of H atoms from all precursors g(H)t = 7,5 ± 0.2 and [Formula: see text] are deduced from the competition. An unscavengeable hydrogen yield g(H2) ~ 0.5 is also indicated in mixtures containing propylene. Nitrous oxide and sulfur hexafluoride are found to scavenge electrons efficiently in water vapor containing methanol and the number of hydrogen atoms arising from electron–positive ion recombination is estimated to have a value G = 2.2 ± 0.6. The number of hydrogen atoms arising from processes not involving electrons is g(H) = 5.2 ± 0.3. Carbon tetrachloride reacts efficiently with both electrons and hydrogen atoms, with k(H + CH3OH)/k(H + CCl4) = 0.085. Values of g(H) = 4.9 ± 0.5 and g(H2) = 0.8 ± 0.2 are deduced from mixtures containing carbon tetrachloride.

THE RADIOLYSIS OF ETHANOL: II. BINARY VAPOR MIXTURES

1961 ◽  
Vol 39 (9) ◽  
pp. 1843-1847
Author(s):  
J. M. Ramaradhya ◽  
G. R. Freeman
Keyword(s):  
Experimental Data ◽  
Kinetic Parameters ◽  
Vapor Phase ◽  
Reaction Mechanisms ◽  
Marked Decrease ◽  
Hydrogen Yield ◽  
Hydrogen Atoms ◽  
Energy Excitation ◽  
Straight Line ◽  
Vapor Mixtures

Benzene and cyclohexene cause a marked decrease in the hydrogen yield from the vapor phase radiolysis of ethanol.The experimental data were tested against the two reaction mechanisms that gave straight-line plots for the corresponding cyclohexane–protector systems. Both of these mechanisms also gave straight-line plots for the ethanol–protector systems.One mechanism involved scavenging of hydrogen atoms. The values of the kinetic parameters derived from this mechanism are quite similar in the cyclohexane and ethanol systems.The second mechanism involved the transfer of energy (excitation or ionization) from ethanol to the protector. The values of the kinetic parameters derived from this mechanism showed some differences between the ethanol and cyclohexane systems.One possible reason for the lack of resolution between the two reaction mechanisms might be that they both occur to comparable extents. Two mechanisms appear to occur to comparable extents in the liquid cyclohexane system.

HYDROGEN FORMATION IN γ-IRRADIATED HYDROGEN CHLORIDE

1962 ◽  
Vol 40 (7) ◽  
pp. 1385-1393 ◽  
Author(s):  
D. A. Armstrong
Keyword(s):  
Hydrogen Chloride ◽  
Solid Hydrogen ◽  
Pure Liquid ◽  
Hydrogen Yield ◽  
Hydrogen Atoms ◽  
A Value ◽  
Low Concentrations ◽  
Electronically Excited ◽  
Γ Rays ◽  
Electronically Excited Molecules

Hydrogen yields from pure liquid and solid hydrogen chloride irradiated with Co60 γ-rays were [Formula: see text](liquid) = 6.50 ± 0.10 and [Formula: see text] (solid) = 3.30 ± 0.10 at −79 °C and −196 °C respectively. The yield from solid hydrogen chloride was only slightly reduced by the addition of chlorine; but the yield from liquid samples was reduced sharply by low concentrations of chlorine to a value of about 4.5, and then much more gradually by larger concentrations. A [Formula: see text] value of 2.1 persisted at 10 mole% chlorine. The results were interpreted in terms of the formation of hydrogen in the reactions[Formula: see text]and[Formula: see text]Reduction of the hydrogen yields by chlorine was attributed to the reactions[Formula: see text]and[Formula: see text]Values of k11/k15 and k11*/k15* were estimated to be 1.7 × 10−3 and 0.10 respectively, while those of GH and GH(hot) were 2.4 ± 0.2 and 4.0 ± 0.2. Electron scavenging by chlorine was considered as a less likely mechanism for reduction of the hydrogen yield. Sources of the thermal and hot hydrogen atoms were examined and it was suggested that the decomposition of electronically excited molecules might be an important mode of decomposition.

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