14-17 May 2018
New Orleans
US/Central timezone

Porosity effects on phase diagram of gas condensate mixture

15 May 2018, 16:16
15m
New Orleans

New Orleans

Oral 20 Minutes MS 1.12: Fluids in Nanoporous Media Parallel 5-E

Speaker

Dr Vasily Pisarev (Joint Institute for High Temperatures of RAS)

Description

A phase diagram of methane+n-butane mixture is investigated by the means of molecular dynamics (MD) simulations. The system exhibits retrograde condensation behavior above 191 K in some range of methane molar fractions. A vapor-liquid equilibrium curve for mixtures is calculated with TraPPE-UA united-atom forcefield [1], TraPPE-EH [2] and OPLS-AA [3,4] all-atom forcefields. The forcefields show good agreement with experimental vaporization curves of pure hydrocarbons. They also reproduce well the composition of liquid phase in binary mixtures as a function of pressure at isotherms, while some discrepancies from experimental data are observed in the saturated vapor compositions. The TraPPE forcefields show better agreement with experimental vapor-liquid equilibrium data than OPLS. The TraPPE-EH accuracy is comparable to that of cubic equations of state.
The effects of nanoscale porosity on mixture phase diagram are qualitatively studied. The saturation curves in slit pores with Lennard-Jones walls are calculated. We considered two sets of wall-molecule interaction parameters and two pore widths. It is shown that nanopores may shift the coexistence curve. At certain wall-molecule interaction parameters, a significant widening of the pressure range of the retrograde condensation is found. This effect may hinder gas extraction from the rocks with a large fraction of nanopores.
The work is supported by the Russian Science Foundation (grant no. 17-79-20391).

References

  1. M.G. Martin and J.I. Siepmann, J. Phys. Chem. B 102, 2569-2577 (1998)
  2. B. Chen and J.I. Siepmann, J. Phys. Chem. B 103, 5370 (1999)
  3. W.L. Jorgensen, D.S. Maxwell and J. Tirado-Rives, J. Amer. Chem. Soc. 118, 11225-11236 (1996)
  4. S.W.I. Siu, K. Pluhackova and R.A. Böckmann, J. Chem. Theory Comput. 8, 1459-1470 (2012)
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Primary authors

Dr Vasily Pisarev (Joint Institute for High Temperatures of RAS) Mr Stepan Zakharov (Joint Institute for High Temperatures of RAS)

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