The effect of the temperature upon the diffusion of methane in silicalite was studied via molecular dynamics, using both a model where the vibrations of the zeolite framework were taken into account and one where the framework was rigid (table 44). The methane molecules were represented by Lennard-Jones particles. The diffusion coefficients were evaluated at four temperatures in the range of 150 to 450K and resulted in good agreement with experiment.
Molecular Dynamics Studies on Zeolites. 6. Temperature Dependence of Diffusion of Methane in Silicalite. P.Demontis, G.B.Suffritti, E.S.Fois, S.Quartieri: Journal of Physical Chemistry, 1992, 96[3], 1482-90
Table 44
Calculated Diffusivities of Methane in Silicalite
Temperature(K) | Framework | D(m2/s) |
446 | vibrating | 8.3 x 10-9 |
290 | vibrating | 6.9 x 10-9 |
221 | vibrating | 6.2 x 10-9 |
167 | vibrating | 3.0 x 10-9 |
451 | rigid | 8.6 x 10-9 |
304 | rigid | 5.5 x 10-9 |
202 | rigid | 4.5 x 10-9 |
169 | rigid | 2.9 x 10-9 |