(190n) 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.