Diffusion of acetylene inside Na-Y zeolite: molecular dynamics simulation studies

Area of Science:

• Materials Science
• Physical Chemistry
• Computational Chemistry

Background:

• Zeolites, particularly Na-Y zeolite, are widely used as catalysts and adsorbents.
• Understanding guest molecule dynamics within zeolite frameworks is crucial for optimizing their performance.
• Acetylene adsorption in zeolites is relevant for petrochemical processes.

Purpose of the Study:

• To investigate the dynamic behavior of acetylene molecules adsorbed in Na-Y zeolite cages.
• To elucidate the translational and rotational motion characteristics of acetylene within the zeolite framework.
• To analyze the time scales and mechanisms governing acetylene diffusion and rotation.

Main Methods:

• Molecular dynamics (MD) simulations were employed to model the system.
• Analysis of translational and rotational motions of acetylene molecules.
• Calculation of intermediate scattering functions to characterize motion.

Main Results:

• Acetylene translational motion exhibits three distinct time scales.
• "Free particle" diffusion observed at short times and small length scales.
• Center of mass motion at long times is dictated by Na-Y zeolite pore topology.
• Rotational motion of acetylene is very fast, characterized by large-angle jumps.
• Rotational dynamics can be described using an m-diffusion model.

Conclusions:

• The study provides detailed insights into the complex dynamics of acetylene in Na-Y zeolite.
• The findings highlight the interplay between guest molecule motion and host zeolite structure.
• The m-diffusion model offers a suitable description for the observed rotational dynamics of acetylene.