(7b) Molecular Simulations of Amine Functionalized MCM-41 for the Separation of CO2/N2

Molecular
simulations of amine functionalized MCM-41 for the separation of CO₂/N₂

The sorptive behavior
of amorphous silica can be enhanced by the use of organic groups. Using certain
organic species can increase the selectivity of solid silica for a given
compound in a gas mixture. These functionalized materials can be used to
capture gases reversibly using adsorption. The effective design of these
materials requires a method that can relate the structure of the adsorbent to
their performance. This level of understanding can be achieved by using
molecular simulations, as they relate the microscopic behavior of the molecules
during the adsorption process to the macroscopic behavior of the system,
allowing one to tailor materials for specific separation purposes. 

We propose a simulation methodology for the design of post-synthesis
functionalized silica materials and the calculation of chemisorbed and
physisorbed CO₂ using Grand Canonical Monte Carlo molecular
simulations. For this purpose realistic model adsorbents are generated using an
energy-bias selection scheme for the possible grafting sites. The methodology
is robust and can be applied for a large variety of different combinations of
solid materials and grafting chains. As an example we evaluate a model MCM-41
grafted with 3-aminopropylsilane for the separation of mixtures of CO₂
and N₂ in
the framework of reduction of CO₂ emissions from flue gases. We analyze the effect of
physisorption and chemisorption on the separation of CO₂ using
grafted amines. The degree of functionalization and the type of bonding of the
organic chains to the inorganic adsorbent are studied aiming to optimize the
sorption of CO₂ over N₂.

 This work was partially financed by the Spanish Government under projects
CTQ2008-05370/PPQ, CTQ2011-23255 and CENIT SOST-CO2 (CEN-2008-1027). Additional support from the Catalan Government through
2009SGR-666 and Carburos Metálicos was also provided. S.B. acknowledges a
Talent grant from the Comission for Universities and
Research of the Generalitat de Catalunya.