研究報告26 - 1 論文 - Original
ジルコニウム合金上のメタン分解動力学
Kinetics of Methane Decomposition over Zr-Ni Alloys
渡辺国昭1), 洲 亘2), 松山政夫1)
1) 富山大学水素同位体科学研究センター、〒930-8555 富山市五福3190
2) Present Afflication: Tritium Process Laboratory, JAERI, Japan
K. Watanabe1), W Shu2), M. Matsuyama1)
1) Hydrogen Isotope Research Center, Toyama University, Gofuku 3190, Toyama 930-8555, Japan
2) Present Affliation: Tritium Process Laboratory, JAERI, Japan
Abstract
The decomposition of methane over Zr, Zr4Ni and Zr2 and Zr2Ni was
investigated to develop
highly active materials for capturing tritiated methane inevitably formed in tritium handling systems.
The entire decomposition or absorption curves, however, could not been described by any simple kinetic
equations appearing in the literature. The present paper describes verification of plausible kinetic
equations reproducing the observed absorption curves, assuming a reaction mechanism consisting of a
progressive removal
of hydrogen atoms according to CH4(g) →CH3(a)→ CH2(a)→
CH(a)→ C(a) and
its modification including carbon segregation schemes by solving a set of kinetic equations by means of finite
difference method,
by taking into account of ab-initio calculations of potential energy surfaces by Gaussian 03.
It was found that a step-by-step H-deletion model could not generate the experimentally
observed absorption curves, but they could be reproduced quite well in the whole reaction
range by a modified reaction scheme assuming coagulation of a carbon residue like CH2(a) or CH(a)
to carbonaceous
deposits, described as CH4(g)- k1 →CH3(a)-k2 →
CH(a)-k3 →C-deposits.
It was concluded that the final third step (with a rate constant of k3) governs the overall
absorption reactivity (methane consumption beyond 90%) of the materials.