Measurement and modeling of methane diffusion in hydrocarbon mixtures

Shi, Zhubing; Khodaparast, Pooya; Hu, Sheng; Tsotsis, Theodore T.; Jessen, Kristian

doi:10.1016/j.fuel.2022.124740

Cited by 5 publications

(1 citation statement)

References 30 publications

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“…Its change in lineshape when crossing the Widom line reflects a substantial change in the molecular interaction length scale and diffusive behaviour. This observation could be exploited to tailor the efficiency of supercritical fluids in industrial applications 74 and could have major consequences on the geodynamics of gas giant planets in our Solar System and beyond.…”

Section: Discussionmentioning

confidence: 99%

Crossover from gas-like to liquid-like molecular diffusion in a simple supercritical fluid

Ranieri,

Formisano,

Gorelli

et al. 2024

Nat Commun

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According to textbooks, no physical observable can be discerned allowing to distinguish a liquid from a gas beyond the critical point. Yet, several proposals have been put forward challenging this view and various transition boundaries between a gas-like and a liquid-like behaviour, including the so-called Widom and Frenkel lines, and percolation line, have been suggested to delineate the supercritical state space. Here we report observation of a crossover from gas-like (Gaussian) to liquid-like (Lorentzian) self-dynamic structure factor by incoherent quasi-elastic neutron scattering measurements on supercritical fluid methane as a function of pressure, along the 200 K isotherm. The molecular self-diffusion coefficient was derived from the best Gaussian (at low pressures) or Lorentzian (at high pressures) fits to the neutron spectra. The Gaussian-to-Lorentzian crossover is progressive and takes place at about the Widom line intercept (59 bar). At considerably higher pressures, a liquid-like jump diffusion mechanism properly describes the supercritical fluid on both sides of the Frenkel line. The present observation of a gas-like to liquid-like crossover in the self dynamics of a simple supercritical fluid confirms emerging views on the unexpectedly complex physics of the supercritical state, and could have planet-wide implications and possible industrial applications in green chemistry.

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Section: Discussionmentioning

confidence: 99%