Diffusion of Propane in Zeolite NaY: A Molecular Dynamics and Quasi-Elastic Neutron Scattering Study

Abstract

We report results from molecular dynamics (MD) simulations and quasi-elastic neutron scattering (QENS) measurements of the diffusion of propane in NaY zeolite at temperatures of 300, 324, and 350 K and a loading of 4 molecules per α-cage. The self-diffusivity, D, has been obtained from mean-squared displacement (msd), as well as from three different models of diffusion fitted to the intermediate scattering function (F(Q,t)) obtained from the MD simulation trajectories. All of the diffusivity values are consistent with each other. Further, these results are in good agreement with the experimental QENS results. It is found that the jump models describe both MD simulation and QENS data reasonably.

Rotational dynamics of propylene inside Na-Y zeolite cages

“…We have also studied the translational diffusivities of propylene in Na-Y and Na-ZSM5 zeolites [6] from which it was seen that the diffusivity of propylene in Na-Y is considerably smaller than that of propane in Na-Y obtained earlier [3]. In continuation of the foresaid study we are also carrying out molecular dynamics simulation studies on this system.…”

“…We have in particular been investigating the diffusivities of hydrocarbons in Na-Y zeolitic cages. In this context we had earlier reported the translational diffusivities of propane, acetylene and 1,3-butadiene in Na-Y zeolite [3][4][5]. The translational diffusivities of these molecules are significantly altered by the confinement effect.…”

Diffusion in Zeolites Measured by Neutron Scattering Techniques

“…In recent molecular dynamics (MD) studies of propane in NaY zeolite, the HWHM obtained from the simulations have been compared with jump diffusion models and with experiment [5,8]. Figure 3 shows fits of different models to the MD data, at three temperatures [8].…”

“…Figure 3 shows fits of different models to the MD data, at three temperatures [8]. The error bars on the MD points is too large to select the 'best' model.…”

“…The Q dependence of the HWHM mediate component 2 , for propane in NaY of the Lorentzian function (Q), obtained showing a typical jump diffusion at three from the experimental QENS data of prodifferent temperatures . The curves are the pane in NaY, fitted with different model fits of different models to the MD data [8].…”