Title: Effects of water on the stochastic motions of propane confined in MCM-41-S pores

Abstract

Hydrocarbons confined in porous media find applications in a wide variety of industries and therefore their diffusive behavior is widely studied. Most of the porous media found in natural environments are laden with water, which might affect the confined hydrocarbons. To quantify the effect of hydration, we report here a combined quasielastic neutron scattering (QENS) and molecular dynamics (MD) simulation study on the dynamics of propane confined in the 1.5 nm-wide micropores of MCM-41-S in the presence of water at 230 and 250 K. To eliminate the strong incoherent signal from water and emphasize the propane signal we have used heavy water (D₂O). QENS data show two dynamically different populations of propane in MCM-41-S and suggest that the presence of water hinders the diffusion of propane. Weak elastic contributions to the QENS spectra suggest that only long-range translational motion of propane molecules contributes to the quasielastic broadening. MD simulations carried out using a model cylindrical silica pore of 1.6 nm diameter filled with water and propane agree with the experimental finding of water hindering the diffusion of propane. Further, the simulation results suggest that the slowing down of propane motions is a function of the water content within the poremore » and is stronger at higher water contents. At high water content, the structure and the dynamics, both translational and rotational, of propane are severely impacted. Simulation data suggest that the rotational motion of the propane molecule occurs on time scales much faster than those accessible with the QENS instrument used, and thus explain the weak elastic contribution to the QENS spectra measured in the experiments. This study shows the effects of hydration on the structure and dynamics of volatiles in porous media, which are of interest for fundamental understanding and applied studies of confined fluids.« less

Authors:

Gautam, Siddharth  ^[1];

• Search DOE PAGES for author "Gautam, Siddharth"
• Search DOE PAGES for ORCID "0000-0003-1443-5382"

Le, Tran Thi Bao ^[2]; Rother, Gernot ^[3]; Jalarvo, Niina  ^[4];

• Search DOE PAGES for author "Jalarvo, Niina"
• Search DOE PAGES for ORCID "0000-0003-0644-6866"

Liu, Tingting  ^[1];

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• Search DOE PAGES for ORCID "0000-0001-9923-690X"

Mamontov, Eugene ^[4]; Dai, Sheng  ^[3];

• Search DOE PAGES for author "Dai, Sheng"
• Search DOE PAGES for ORCID "0000-0002-8046-3931"

Qiao, Zhen-An ^[3]; Striolo, Alberto  ^[2];

• Search DOE PAGES for author "Striolo, Alberto"
• Search DOE PAGES for ORCID "0000-0001-6542-8065"

Cole, David ^[1]

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+ Show Author Affiliations

1. The Ohio State Univ., Columbus, OH (United States)
2. Univ. College London (UCL), Surrey (United Kingdom)
3. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Chemical Sciences Division
4. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Nuclear Science Directorate

Publication Date:

Tue Oct 29 00:00:00 EDT 2019

Research Org.:

Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)

Sponsoring Org.:

USDOE Office of Science (SC), Basic Energy Sciences (BES)

OSTI Identifier:

1606829

Alternate Identifier(s):

OSTI ID: 1573265

Grant/Contract Number:  

AC05-00OR22725; SC0006878

Resource Type:

Accepted Manuscript

Journal Name:

Physical Chemistry Chemical Physics. PCCP (Print)

Additional Journal Information:

Journal Name: Physical Chemistry Chemical Physics. PCCP (Print); Journal Volume: 21; Journal Issue: 45; Journal ID: ISSN 1463-9076

Publisher:

Royal Society of Chemistry

Country of Publication:

United States

Language:

English

Subject:

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY