STUDY ON PERMEATION OF ACETONE/NITROGEN MIXED GAS THROUGH AL₂O₃ MICROPOROUS MEMBRANES: MOLECULAR DYNAMICS

Abstract

In this work, by applying Materials Studio 2.2 software package, molecular dynamics (MD) was performed to investigate the dynamic processes of 1:4 acetone/nitrogen mixed gas permeating through different Al₂O₃ microporous membranes. Three systems were modeled by considering different box lengths, microporous sizes, and textures of Al₂O₃ membranes to compare different permeation behaviors. In each system, initial mixed gas contained 20 acetone molecules and 80 nitrogen molecules, and its density was set to 0.1 g/cm³. Analysis on the concentration profiles of nitrogen molecules (N2) and acetone molecules (Ace) in each system at different sampling times was implemented to discuss the permeation behaviors of smaller N2 and larger Ace. The results showed that adsorption and diffusion occurred synchronously but adsorption was dominant for acetone molecules and that the adsorption on the floor surface of the feed gas region more easily reached equilibrium (local equilibrium) than the diffusion and the adsorption on the ceiling of the initially vacuum region. Furthermore, for nitrogen, adsorption followed diffusion. Higher temperature is in favor of the enrichment of acetone on the floor surface of the feed gas region but against the adsorption of nitrogen. The adsorptive layer was found to be a double-layer with COMPASS force field and to be a monolayer with PCFF force field.

Keywords:

• Al₂O₃ membrane
• Acetone/Nitrogen mixed gas
• Molecular dynamics
• Permeation

Acknowledgments

This work was supported by Nature and Science Fund of China (20406007), Jiangsu Nature and Science Foundation (BK2003402), and Nature and Science Fund of Jiangsu University (04KJB150028).

Notes

Hole: existed in the micropore; vacu: diffused into the initially vacuum region; a: system I; b: system II.