Simulation of the Gas Separation in Hybrid Inorganic-Organic Membrane

Membrane separation is widely used in the energy industry for gas mixtures. For decades, experimentalists have invested a significant amount of time to develop novel membranes with better efficiency and selectivity. Understanding the mechanistic steps in the separation can lead to better membrane designs and shorter development.

The gas separation process is simulated with the hybrid inorganic-organic membrane model constructed from our previous study, which used MD with BKS force field to generate amorphous silicon dioxide and followed by MD with Dreiding force field to optimize the hybrid membrane structure. To obtain the permeability and selectivity of the membrane, non-equilibrium molecular dynamics must be applied to vary the number of molecules. Thus the dual control volume grand canonical MD (DCV-GCMD) method is used with Dreiding force field. At 400K with the feed pressure of 4MPa, the permeability of CO²  is  3.05×10^-7 mol m^-2 s^-1 Pa^-1 and that of CH⁴ is  5.00×10^-8 mol m^-2 s^-1 Pa^-1. The calculated properties are compared with the experimental data of the specific membrane.

We are currently investigating the relation between the ability for separation of the membrane and the characters of the structure of the membrane, the size of the pore, the number of phenyl group in the structure, etc. Also we are studying to improve the simulation result by using different force field.