Large Distinct Diffusivity in Binary Mixtures Confined to Zeolite NaY

Abstract

Mutual diffusion coefficients have been computed from molecular dynamics simulation of two different binary mixtures confined to zeolite NaY. In one of these mixtures, where one component is from the linear regime and the other from the anomalous regime of the levitation effect [S. Yashonath, P. Santikary, J. Phys. Chem., 1994, 98, 6368], the magnitude of distinct diffusivity, Dd, is unusually large and comparable to the mixture self-diffusivity Ds. Distinct van Hove correlations suggest that the large Dd seems to arise from the presence of distinct physisorption sites for the two components. The contribution from Dd might be important for achieving good separation of mixtures, for which zeolites are used extensively.

Separation of hydrocarbon mixture of neopentane and n‐hexane using NaY zeolite: Large distinct diffusivity

“…This suggests, for the first time, we have a system in which the transport diffusivity is large, because of the significant contribution from the distinct diffusivity. Typically, the contribution from distinct diffusivity to the transport diffusivity is between 1% and 30% 18,20,21,43,48–50 . In contrast to this, here the contribution from distinct diffusivity is 230% of the contribution from the self diffusivity.…”

“…Typically, the contribution from distinct diffusivity to the transport diffusivity is between 1% and 30%. 18,20,21,43,[48][49][50] In contrast to this, here the contribution from distinct diffusivity is 230% of the contribution from the self diffusivity.…”

“…The value of R we have obtained for the mixture of neopentane and n-hexane are much higher than the value of R obtained for other mixtures reported in the literature. 20,21 For example, a mixture of 2,2-dimethyl butane and n-hexane by Ahsan et al, 21 found a value of 0.77 for R at 300 K. The nature of the mixture in our work and their work are similar as one of the components in our mixture is branched and another one is linear, and both mixtures are diffusing in the same porous material, namely, zeolite NaY. But, the higher value of R in our case arises from the judicious combination of the choice of the zeolite and introduction of localized hot zones.…”

“…Distinct diffusivity arises from interactions between distinct particles i and j of the same species as well as different species. Thus, it will have contributions from distinct particles of n ‐hexane and also from distinct particles of neopentane as well as distinct particle i of n ‐hexane and j of neopentane, in a binary mixture of n ‐hexane and neopentane 18–21 …”

“…Thus, it will have contributions from distinct particles of n-hexane and also from distinct particles of neopentane as well as distinct particle i of n-hexane and j of neopentane, in a binary mixture of n-hexane and neopentane. [18][19][20][21] The mixture self-diffusivity is defined as…”