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When immiscible becomes miscible-Methane in water at high pressures
Ciprian G Pruteanu1, Graeme J Ackland1, Wilson C K Poon1
1SUPA, School of Physics Astronomy Centre for Science at Extreme Conditions, The University of Edinburgh, Edinburgh, EH9 3JZ, UK.
Science Advances
|August 29, 2017
Summary
Methane solubility in water dramatically increases at high pressures (above 2 GPa), exceeding 35 mol % at 100°C. This finding challenges previous models of gas solubility under extreme conditions.
Area of Science:
- Geochemistry
- Physical Chemistry
- Fluid Phase Behavior
Background:
- Henry's law describes gas solubility at low pressures, but deviations occur at higher pressures.
- Methane is a key hydrophobe in geology, and its solubility behavior is critical for understanding natural systems.
- Previous studies showed limited gas solubility increase at high pressures, differing from critical point phenomena.
Purpose of the Study:
- To measure the solubility of methane in water at high pressures (up to 3.5 GPa) and a constant temperature (100°C).
- To investigate the pressure dependence of methane solubility below water's critical temperature.
- To understand the behavior of hydrophobes in aqueous solutions under extreme geological conditions.
Main Methods:
- High-pressure solubility measurements of methane in water.
- Experimental setup capable of reaching pressures up to 3.5 gigapascals (GPa).
- Controlled temperature maintained at 100°C, well below the critical point of water.
Main Results:
- Methane solubility shows a significant increase between 1 and 2 GPa.
- Above 2 GPa, methane solubility in water exceeds 35 mole percent (mol %).
- This high solubility is observed at 100°C, far from the critical point of water.
Conclusions:
- Methane exhibits exceptionally high solubility in water at pressures above 2 GPa.
- The observed solubility behavior deviates significantly from predictions based on low-pressure models.
- These findings have implications for geological processes involving methane and water under high pressure.
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