2020 年 49 巻 1 号 p. 28-34
The deeper part of the Earth's mantle is considered to be reduced state where CH4, H2, and hydrocarbons would exist. Thus, the reduced species of carbon-hydrogen compounds are likely to play an important role in the deep cycle of carbon and hydrogen at the upper mantle. Effects of H2 fluid on stability and phase relation of silicate minerals were investigated on MgO-SiO2-H2 systems using laser-heated diamond-anvil cells. It was revealed that SiO2 components dissolve into H2 fluid, with formation of Si-H compounds and H2O molecules at 2-15 GPa, >1500 K. Aromatic hydrocarbons are considered as the most abundant organic materials in nature and the existence of aromatic compounds in interior of the Earth and icy planets has been reported. In this study, pressure-induced chemical reactions of aromatic hydrocarbons, such as benzene and naphthalene were reported. Mass spectrometry of the reaction products revealed that oligomerization occurred after compression >15 GPa at room temperature. The dimerization products were classified into three groups, simple dimerization, naphthylation, and condensation. It was indicated that release of hydrogen by the pressure-induced oligomerization was lesser as compared to the temperature-induced pyrolysis. The results provide a basic information on the chemical reaction of organics in the deep interior of the Earth.
