Diffusion of hydrocarbons in confined media: Translational and rotational motion |
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Authors: | S Y Bhide A V Anil Kumar and S Yashonath |
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Institution: | (1) Solid State and Structural Chemistry Unit, Indian Institute of Science, 560 012 Bangalore, India |
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Abstract: | Diffusion of monatomic guest species within confined media has been understood to a good degree due to investigations carried
out during the past decade and a half. Most guest species that are of industrial relevance are actually polyatomics such as,
for example, hydrocarbons in zeolites. We attempt to investigate the influence of non-spherical nature of guest species on
diffusion. Recent molecular dynamics (MD) simulations of motion of methane in NaCaA and NaY, benzene in NaY and one-dimensional
channels AlPO4−5, VPI−5 and carbon nanotube indicate interesting insights into the influence of the host on rotational degrees of freedom
and orientational properties. It is shown that benzene in one-dimensional channels where the levitation parameter is near
unity exhibits translational motion opposite to what is expected on the basis of molecular anisotropy. Rotational motion of
benzene also possesses rotational diffusivities aroundC
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and C2axes opposite to what is expected on the basis of molecular geometry. Methane shows orientational preference for 2+ 2 or 1
+ 3 depending on the magnitude of the levitation parameter. |
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Keywords: | Diffusion hydrocarbons orientational preference translational orientational coupling molecular dynamics |
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