Molecular motion in restricted geometries

Gautam, Siddharth; Mitra, S.; Mukhopadhyay, R.

doi:10.1007/s12043-008-0271-1

Cited by 5 publications

(5 citation statements)

References 25 publications

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“…In natural environments, they are mostly found confined in porous media like sedimentary rocks such as shale which can profoundly affect their behavior [1,2]. Several studies have reported the effect of nano-confinement on various properties of the adsorbate including its structure, phase behavior and dynamics.…”

Section: Effect Of Temperature and Pressure On The Dynamics Of Nanocomentioning

confidence: 99%

Effect of temperature and pressure on the dynamics of nanoconfined propane

Gautam

Liu

Rother

et al. 2014

AIP Conference Proceedings

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On the molecular origin of high-pressure effects in nanoconfinement: The role of surface chemistry and roughness Effects of pressure, temperature, and hydrogen during graphene growth on SiC(0001) using propane-hydrogen chemical vapor deposition Abstract. We report the effect of temperature and pressure on the dynamical properties of propane confined in nanoporous silica aerogel studied using quasielastic neutron scattering (QENS). Our results demonstrate that the effect of a change in the pressure dominates over the effect of temperature variation on the dynamics of propane nano-confined in silica aerogel. At low pressures, most of the propane molecules are strongly bound to the pore walls, only a small fraction is mobile. As the pressure is increased, the fraction of mobile molecules increases. A change in the mechanism of motion, from continuous diffusion at low pressures to jump diffusion at higher pressures has also been observed.

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Section: Effect Of Temperature and Pressure On The Dynamics Of Nanocomentioning

confidence: 99%

Effect of temperature and pressure on the dynamics of nanoconfined propane

Gautam

Liu

Rother

et al. 2014

AIP Conference Proceedings

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“…Molecular motion under confinement is an interesting topic of research as it entails a variety of peculiar phenomena [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18] . Anomalous size and loading dependence of molecular dynamics of confined fluids in porous media have been reported [6][7][8] , suggesting the need of better understanding how confinement affects not only the structure but also the transport-properties of confined fluids.…”

Section: Introductionmentioning

confidence: 99%

Molecular dynamics simulations of propane in slit shaped silica nano-pores: direct comparison with quasielastic neutron scattering experiments

Gautam

Striolo

et al. 2017

Phys. Chem. Chem. Phys.

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Molecular motion under confinement has important implications for a variety of applications including gas recovery and catalysis. Propane confined in mesoporous silica aerogel as studied using quasielastic neutron scattering (QENS) showed anomalous pressure dependence in its diffusion coefficient (J. Phys. Chem. C, 2015, 119, 18188). Molecular dynamics (MD) simulations are often employed to complement the information obtained from QENS experiments. Here, we report an MD simulation study to probe the anomalous pressure dependence of propane diffusion in silica aerogel. Comparison is attempted based on the self-diffusion coefficients and on the time scales of the decay of the simulated intermediate scattering functions. While the self-diffusion coefficients obtained from the simulated mean squared displacement profiles do not exhibit the anomalous pressure dependence observed in the experiments, the time scales of the decay of the intermediate scattering functions calculated from the simulation data match the corresponding quantities obtained in the QENS experiment and thus confirm the anomalous pressure dependence of the diffusion coefficient. The origin of the anomaly in pressure dependence lies in the presence of an adsorbed layer of propane molecules that seems to dominate the confined propane dynamics at low pressure, thereby lowering the diffusion coefficient. Further, time scales for rotational motion obtained from the simulations explain the absence of rotational contribution to the QENS spectra in the experiments. In particular, the rotational motion of the simulated propane molecules is found to exhibit large angular jumps at lower pressure. The present MD simulation work thus reveals important new insights into the origin of anomalous pressure dependence of propane diffusivity in silica mesopores and supplements the information obtained experimentally by QENS data.

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“…In addition to this fundamental interest, a study of molecular motion under confinement has practical implications in industries like catalysis and gas recovery. This has resulted in an extensive study of molecular dynamics under confinement. − Of particular interest is the dynamics of hydrocarbons confined in porous media − ,− due to their application in catalytic cracking reactions and hydrocarbon recovery. Porous media is classified according to IUPAC as microporous with pores smaller than 2 nm and mesoporous with pores larger than 2 nm in size .…”

Section: Introductionmentioning

confidence: 99%

Dynamics of Propane in Nanoporous Silica Aerogel: A Quasielastic Neutron Scattering Study

et al. 2015

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Molecular motion of hydrocarbons under confinement exhibits several peculiarities and has important implications in industries like gas recovery. A quasielastic neutron scattering (QENS) study of the dynamics of propane in nanoporous silica aerogel was carried out to quantify its molecular mobility. The dynamical properties of propane were studied as a function of temperature, pressure and presence of CO2. The effects of pressure, i.e., fluid density and composition, are found to be more pronounced than the effects of temperature. At low pressures of propane, many propane molecules are adsorbed onto the pore surfaces and are thus immobile. As the pressure of propane loading is increased, more molecules become available to take part in the diffusional dynamics and thus enhance the diffusivity. At low pressure the propane molecules take part in a continuous diffusion, while at higher pressures, the diffusion of propane molecules within the aerogel occurs via the mechanism of jumps. Presence of CO2 enhances the jump rate of propane molecules, thereby increasing the diffusion coefficient. This study aims to aid in understanding the complex processes involved in hydrocarbon migration in porous quartz-rich rocks and enhanced hydrocarbon recovery.

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Molecular motion in restricted geometries

Cited by 5 publications

References 25 publications

Effect of temperature and pressure on the dynamics of nanoconfined propane

Effect of temperature and pressure on the dynamics of nanoconfined propane

Molecular dynamics simulations of propane in slit shaped silica nano-pores: direct comparison with quasielastic neutron scattering experiments

Dynamics of Propane in Nanoporous Silica Aerogel: A Quasielastic Neutron Scattering Study

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