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.