Nucleation of the short-chain n-alkanes from the vapor phase: Experiments and Monte Carlo simulations
Invited
Abstract
The n-alkanes do not nucleate easily from the vapor phase, and, when rapidly cooled in a supersonic expansion, saturation levels on the order of 10,000 are typical. [1, 2] The nucleation rates measured for n-pentane through n-heptane, at temperatures ranging from ~109 K to 168 K, are on the order of 1017 cm-3s-1, increasing slightly with decreasing temperature. Despite the high degree of supercooling, Monte Carlo (MC) simulations suggest that for n-pentane through n-heptane the critical clusters remain liquid like under experimental conditions, whereas n-octane and n-nonane adopt more ordered structures. For all three alkanes, the scaled experimental and simulated nucleation rates are offset by ~3 orders of magnitude. Explicitly accounting for the surface tension difference between the real and model substances, however, increases the offset to ~ 6 orders of magnitude, equivalent to a a formation free energy difference of ~13kBT . This difference could be reduced by changing the cutoff criterion or by using model potentials that better describe n-alkane behavior.
[1] David Ghosh, Dirk Bergmann, Regina Schwering, Judith Wölk, Reinhard Strey, Shinobu Tanimura, Barbara E. Wyslouzil, “Homogeneous nucleation of a homologous series of n-alkanes (CiH2i+2, i=7-10) in a supersonic nozzle,” J. Chem. Phys., 132, 024307 (2010).
[2] Kehinde Ogunronbi, Aliasghar Sepehri, Bin Chen, and Barbara E. Wyslouzil, Vapor phase nucleation of the short-chain n-alkanes (n-pentane, n-hexane and n-heptane): Experiments and Monte Carlo simulations, Journal of Chemical Physics, 148, 144312 (2018)
[1] David Ghosh, Dirk Bergmann, Regina Schwering, Judith Wölk, Reinhard Strey, Shinobu Tanimura, Barbara E. Wyslouzil, “Homogeneous nucleation of a homologous series of n-alkanes (CiH2i+2, i=7-10) in a supersonic nozzle,” J. Chem. Phys., 132, 024307 (2010).
[2] Kehinde Ogunronbi, Aliasghar Sepehri, Bin Chen, and Barbara E. Wyslouzil, Vapor phase nucleation of the short-chain n-alkanes (n-pentane, n-hexane and n-heptane): Experiments and Monte Carlo simulations, Journal of Chemical Physics, 148, 144312 (2018)
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Presenters
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Barbara Wyslouzil
Ohio State University
Authors
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Barbara Wyslouzil
Ohio State University
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Kehinde Ogunronbi
Ohio State University
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Aliasghar Sepehri
Chemistry, Louisiana State University
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Bin Chen
Chemistry, Louisiana State University