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In situ Raman spectroscopic observation of thiol transformation in hydrothermal fluids: implications for hydrocarbon decomposition and reservoir desulfurization
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DOI：10.1016/j.gca.2026.07.034.png)
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Abstract
En 中文
Thiols play important roles in global carbon and sulfur cycling, hydrocarbon alteration and metal mineralization. However, their transformation pathways and thermal stability in hydrothermal systems remain poorly constrained. Here we use an in situ approach combining fused silica capillary capsules with Raman spectroscopy to investigate the fate of thiols during hydrous pyrolysis and thermochemical sulfate reduction (TSR). Our results show that thiols are sequentially transformed into alcohols, aldehydes/ketones, and carboxylic acids, which subsequently decarboxylate or oxidize to form light hydrocarbons and CO2. Complex organic sulfur compounds—including sulfides, disulfides, sulfones, and thiophenes—are also generated, and their formation can be explained by radical mechanisms. Thiol hydrous pyrolysis proceeds more slowly than anhydrous pyrolysis at high temperatures (e.g., >247.5 °C for 1‑propanethiol) but faster at lower temperatures. Notably, thiols significantly enhance the rate of sulfate reduction, providing direct kinetic evidence that they can promote TSR. Even in the absence of external sulfate, thiol formation and hydrous pyrolysis can still promote hydrocarbon decomposition while transferring H2S from formation fluid into solid bitumen, serving as a critical but previously overlooked reservoir desulfurization mechanism. Because TSR-derived H2S reacting with hydrocarbon is a major pathway for thiol formation, the overall impact of TSR on hydrocarbon decomposition may be substantially underestimated. These results establish a kinetic and mechanistic framework for thiol-mediated C-S cycling in hydrothermal systems, with implications for hydrocarbon decomposition and reservoir desulfurization.
Keywords:
Thiol
Reaction pathway
Kinetics
Hydrothermal experiments
Raman spectroscopy
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