Production of abiotic or biogenic hydrocarbons on rock particles in the presence of H2O and carbon compounds

Le résumé fourni par la source

Abiotic H 2 and hydrocarbons are found in fluids discharged from ultramafic-hosted hydrothermal vents. Beneath the hydrothermal vents, abiotic H 2 and hydrocarbons can be formed by serpentinization reactions and Fischer–Tropsch-type hydrocarbon-forming reactions, respectively, over ultramafic rocks. However, the source rocks that form abiotic H 2 and hydrocarbons may extend to broader subsurface rocks. Here, we show that various rock constituents (solid acids) play a catalytic role in the formation of H and OH radicals via H 2 O dissociation, as well as in the formation of diverse hydrocarbons via the synthesis reactions of H radicals and inorganic carbons or by H radical-induced dissociation of organic carbons. The mechanisms and characteristics of these formation processes were explored through a series of reactor-based laboratory experiments. Four types of solid acid-containing rocks were mixed with H 2 O and a carbon source and reacted at different temperatures and pressures for different reaction periods. The product gases were analyzed via GC/MS. Twenty-nine hydrocarbons up to C 11 , predominantly including CH 4 and aromatic hydrocarbons, were identified when CO 2 (inorganic carbon source) and basalt particles were used; in contrast, 42 hydrocarbons up to C 11 , predominantly including CH 4 and aliphatic hydrocarbons, were identified when soybean oil (organic carbon source) and basalt particles were used. The results of this study imply that abiotic H 2 and diverse hydrocarbons are produced in the subsurface of Earth regardless of the presence of living organisms and suggest that solid acid-containing rocks near hot springs or volcanic areas can promote CO 2 conversion into CH 4 with the aid of H radicals supplied from H 2 O dissociation over the rocks.

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