Methanol diffusion in H-ZSM-5 catalysts as a function of loading and Si/Al ratio: A classical molecular dynamics study

The Effect of Si/Al Ratio on Local and Nanoscale Water Diffusion in H-Zsm-5: A Quasielastic Neutron Scattering and Molecular Dynamics Simulation Study

“…As the Si/Al ratio is decreased, and more BASs are introduced, the water diffusivity decreases from 1.31 to 0.65 × 10 − 10 m 2 s − 1 at 300 K and from 6.21 to 2.58 × 10 − 10 m 2 s − 1 at 360 K. As in previous work investigating water diffusion in zeolite Y [19] and methanol in H-ZSM-5 [10], a stronger dependence is observed at lower Si/Al ratiosillustrated in Fig. 10.…”

“…As well as the diffusion coefficients being lower, we note that the scale of mobility probed is significantly larger than those probed by our QENS experiments, modelling the nanoscale mobility throughout the whole supercell rather than the more localised motions discussed in the experimental section. Comparing to previous MD simulations of methanol in H-ZSM-5 [10], the activation energies here are significantly larger (by 10-15 kJ mol − 1 ), as one would expect given the larger orientational dependence of methanol hydrogen bonding, both with the zeolite and between methanol molecules. This orientational dependence would logically lead to a lower frequency of said H-bonding interactions, so their influence on the activation energy would be lower.…”

“…This decreases the favourability of the deprotonated structure, increasing the deprotonation energy with the greater likelihood of proximal sites at lower Si/Al ratios [9]. Small molecules such as water or methanol, which demonstrate high diffusivity when unconfined, are significantly hindered by strong hydrogen bonding interactions with acid sites, as observed by a range of modelling [10,11] and spectroscopic studies [12][13][14].…”

Diffusion Mechanisms of Dissolved Gases in Transformer Oil Influenced with Moisture Based on Molecular Dynamics Simulation

“…In recent years, molecular simulation technology has made many important achievements in the aging of transformer insulating oil. At the same time, great progress has been made in the study of molecular diffusion mechanisms from the microperspective . For example, Koirala et al studied the water diffusion in mixed insulating oil at different temperatures by molecular dynamics simulation .…”

“…At the same time, great progress has been made in the study of molecular diffusion mechanisms from the microperspective. 23 For example, Koirala et al studied the water diffusion in mixed insulating oil at different temperatures by molecular dynamics simulation. 24 Wang et al studied the structures of graphene-reinforced epoxy coatings and the dynamic diffusion of guest water.…”