Primary Processes of Hydrogen Formation in the Gas- and Liquid-Phase Radiolysis of Propane

Abstract

The yield of hydrogen formed in the gas- and liquid-phase radiolysis of propane has been measured in the presence of a “radical scavenger” (C2H4) and an electron scavenger (N2O or SF6). Further, the isotopic compositions of the hydrogen formed in the gas-phase radiolyses of C3H8–C3D8, C3H8–4 mole % SF6–C3D8, and C3H8–4 mole % C2H4–C3D8 mixtures and also those in the liquid-phase radiolyses of C3H8–C3D8, C3H8–0.4M SF6–C3D8, and C3H8–0.2M C2H4–C3D8 mixtures have been measured to determine the unimolecular fraction of hydrogen for each mixture. Combining these results, the yields of six primary processes by which hydrogen is formed have been evaluated. The results are that for the gas-phase radiolysis G (thermal hydrogen atom), G (hot hydrogen atom), and G (unimolecular hydrogen) are, respectively, 2.5, 0.9, and 1.4 by direct excitation and ionization, and that G (thermal hydrogen atom and hot hydrogen atom) and G (unimolecular hydrogen) are, respectively, 1.9 and 0.7 by neutralization. For the liquid-phase radiolysis G (thermal hydrogen atom), G (hot hydrogen atom), and G (unimolecular hydrogen) are, respectively, 0.9, 1.2, and 0.4 by direct excitation and ionization and 0.6, 0.7, and 1.0 by neutralization with probable errors of ± 0.2. The G values of the six primary processes for propane in the liquid-phase radiolysis are almost the same as those for n-butane previously reported. A possible role of hot hydrogen atoms has been pointed out in the gas-phase as well as in the liquid-phase radiolysis of propane. It is also suggested that ethylene scavenges with high efficiency not only thermal hydrogen atoms but also positive ions, expecially in the gas phase.