Membranes based on porous, inorganic materials such as structured mesoporous silicas (for example MCM materials) are being increasingly considered for industrial separation processes because of their compatibility with high temperature environments and their ability to separate species which are close in molecular size. These materials can be further tailored by introducing functional surface groups. Here, we present the results of our research into the design and optimization of one such mesoporous inorganic silica material, MCM-41, for the removal of carbon dioxide from flue gases.

We have used a number of different molecular modelling techniques including an in-house kinetic Monte Carlo method for the creation and validation of a pore model, grand-canonical Monte-Carlo simulations for the adsorption of pure components and typical flue gas compositions and non-equilibrium molecular dynamics simulations to calculate the flux and transport diffusion coefficients of the components of flue gases in MCM-41 under various conditions. These techniques not only allow for macroscopic predictions of adsorption isotherms and diffusion coefficients but also give a detailed picture of molecular-level phenomena which is not easily accessible using experimental methods.

Here, we present findings and conclusions based on our simulation results. In particular, we describe how the size of the pore wall and pore wall functionalization with organic surface groups can influence diffusant transport and behavior. Our investigations allow us to propose an optimally performing material with a specific pore diameter and surface group functionalization. Importantly, the simulated modifications to the pore wall are experimentally reproducible. We therefore envisage that an optimally performing MCM-41 material designed using these simulation methods can be targeted for experimental synthesis.