Radiolysis of aqueous methane solutions

Abstract

The -ray and electron pulse irradiation of aqueous methane and some ethane solutions is reported. The absorption spectra of the CH3 and C2H5 free radicals have been measured in the wavelength range 210-270 nm. At 210 nm e(CH3) = 850 M-1 cm-1 and e(C2Hs) = 520 M-1 cm-1. The bimolecular recombination rate constants are 1.24 ± 0.2 x 109 and 0.96 ± 0.2 X 109 M-1 sec-1 for CH3 and C2H5, respectively. The rate constant fe(OH + CH4) = 1.21 ± 0.4 X 108 M-1 sec-1; k(CHa + H202) = 3.5 X 107 M-1 sec-1. The yields G(-CH4), G(C2H6), G(H2), G(H2Ó2), and G(N2) for N20-CH4 solutions are reported for some acid, neutral, and alkaline solutions. A radiolysis mechanism is also given. menta fe(CH4 + OH) has been established as 1.4 x 108 M-1 sec-1.7 As expected, CH3 is the product radical and its re-(1) Work performed under the auspices of the U.S. Atomic Energy Commission.(2) G. G. Meisels in "Fundamental Processes in Radiation Chemistry." P.

Kinetics and anomalous temperature dependence of the kinetic isotope effect of reactions of cycloalkanes C5H10, C6H12 and C6D12 with OH radicals in aqueous solutions

“…where E 5 -E 6 is the difference in activation energies and A 6 /A 5 is the ratio of the preexponential constants of the Arrhenius equation for cyclohexane (6) and cyclopentane (5). In contrast to the KIE, the k 6 /k 5 ratio varies differently with increasing temperature for different groups of reagents.…”

“…The absolute rate constants for reaction (1) have been measured in aqueous solution only for methane [5,6], while relative rate constants in the methane series have been measured for butane [7-10] and cyclopentane [11,12].…”

“…The kinetics of the reactions of OH radicals with saturated hydrocarbons (RH) (1) RH + OH ⋅ ® [R…H…OH] ® R ⋅ + H 2 O including cycloalkanes, has been studied extensively in the gas phase [1]. The absolute rate constants for reaction (1) have been measured in aqueous solution only for methane [5,6], while relative rate constants in the methane series have been measured for butane [7][8][9][10] and cyclopentane [11,12].…”

Review of waste package verification tests. Semiannual report, October 1982-March 1983

“…No G(H2) value for the aqueous methane solution was reported in the Stevens (1972) study. water (0.45), it should be noted that the methane content (-0.1 mol) in our system is approximately 250 times less than the content of water.…”

“…Henry's Law coefficient for methane at this temperature is -4 x lo4 atm/mole fraction (Himmelblau, D. M., 1960). Results of a study on the gamma radiolysis of aqueous methane solutions (Stevens, G. C., 1972) have indicated that only the OH free radical (from the water radiolysis) reacts with methane to any appreciable extent. Methyl radical is the product of this reaction.…”