Methane, the principal component of natural gas, is an important energy source and raw material for chemical reactions. It also plays a significant role in planetary physics, being one of the major constituents of giant planets. Here, we report measurements of the molecular self-diffusion coefficient of dense supercritical CH4 reaching the freezing pressure. We find that the high-pressure behaviour of the self-diffusion coefficient measured by quasi-elastic neutron scattering at 300 K departs from that expected for a dense fluid of hard spheres and suggests a density-dependent molecular diameter. Breakdown of the Stokes-Einstein-Sutherland relation is observed and the experimental results suggest the existence of another scaling between self-diffusion coefficient D and shear viscosity eta, in such a way that D eta/rho =constant at constant temperature, with rho the density. These findings underpin the lack of a simple model for dense fluids including the pressure dependence of their transport properties. Methane is abundant in the Universe, is an important energy carrier and a model system for fundamental studies. Here, the authors measure the self-diffusion coefficient of supercritical methane at ambient temperature up to the freezing pressure, and find a different behavior than expected based on previous models.

Diffusion in dense supercritical methane from quasi-elastic neutron scattering measurements / Ranieri, Umbertoluca; Klotz, Stefan; Gaal, Richard; Koza, Michael Marek; Bove, Livia E. - In: NATURE COMMUNICATIONS. - ISSN 2041-1723. - 12:1(2021), p. 1958. [10.1038/s41467-021-22182-4]

Diffusion in dense supercritical methane from quasi-elastic neutron scattering measurements

Ranieri, Umbertoluca
;
Bove, Livia E
2021

Abstract

Methane, the principal component of natural gas, is an important energy source and raw material for chemical reactions. It also plays a significant role in planetary physics, being one of the major constituents of giant planets. Here, we report measurements of the molecular self-diffusion coefficient of dense supercritical CH4 reaching the freezing pressure. We find that the high-pressure behaviour of the self-diffusion coefficient measured by quasi-elastic neutron scattering at 300 K departs from that expected for a dense fluid of hard spheres and suggests a density-dependent molecular diameter. Breakdown of the Stokes-Einstein-Sutherland relation is observed and the experimental results suggest the existence of another scaling between self-diffusion coefficient D and shear viscosity eta, in such a way that D eta/rho =constant at constant temperature, with rho the density. These findings underpin the lack of a simple model for dense fluids including the pressure dependence of their transport properties. Methane is abundant in the Universe, is an important energy carrier and a model system for fundamental studies. Here, the authors measure the self-diffusion coefficient of supercritical methane at ambient temperature up to the freezing pressure, and find a different behavior than expected based on previous models.
2021
methane, diffusion, extreme conditions, simple liquids
01 Pubblicazione su rivista::01a Articolo in rivista
Diffusion in dense supercritical methane from quasi-elastic neutron scattering measurements / Ranieri, Umbertoluca; Klotz, Stefan; Gaal, Richard; Koza, Michael Marek; Bove, Livia E. - In: NATURE COMMUNICATIONS. - ISSN 2041-1723. - 12:1(2021), p. 1958. [10.1038/s41467-021-22182-4]
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11573/1558860
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