MD Simulation of CO2/CH4 Gas Separation with Hybrid Membrane

Membrane is one of the most widely used materials for gas separation. Many efforts have been made to improve the performance of membrane and hybrid organic-inorganic membrane is one novel type with plenty of advantages. Thus we studied this hybrid membrane to understand the mechanism and further to find new research direction of experiment.

Regular shaped pores are created in silicon-dioxide crystal structure. The pores are blocked by different number of phenyl groups which are randomly bonded to silicon atoms on the wall of the pores. Gas molecules are disposed in one side of membrane structure and the other side is left as vacuum. Gas molecules are restricted from to move to the other side by a repulsive wall. The simulation is under 375K and 20MPa in 1 to 4 ns, which is depending on the permeance results. The effect of the pore's radius on the selectivity and permeance is studied. The permeance is of the order of 10^{-4  mol} m^-2 s^-1 Pa^-1 . The selectivity changes from 0.31 to 1.15. We also researched how the number of phenyl groups in the channel affects the performance and the related mechanism. The orientation of the phenyl groups can cause significant difference. Also the distances between the atoms of the phenyl group and nearby atoms from the frame lead to different result for the separation. Based on the simulation results, one membrane structure is constructed which yield to the selectivity of 68 at thelevel of permeance.