Molecular simulation studies in periodic mesoporous silicas SBA-2 and STAC-1: model development and adsorption applications
Ferreiro Rangel, Carlos Augusto
Rangel, Carlos Augusto Ferreiro
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Adsorption is a low-energy separation process especially advantageous when the components to be separated are similar in nature or have a low molar concentration. The choice of the adsorbent is the key factor for a successful separation, and among them periodic mesoporous silicas (PMS) are of importance because of their pore sizes, shapes and connectivity. Furthermore, they can be modified by post-synthesis functionalisation, which provides a tool for tailoring them to specific applications. SBA-2 and STAC-1 are two types of PMS characterised by a three-dimensional pore system of spherical cages interconnected by a network of channels whose formation process was until now obscure. In this work the kinetic Monte Carlo (kMC) technique has been extended to simulate the synthesis of these complex materials, presenting evidence that the interconnecting network originates from spherical micelles touching during their close-packing aggregation in the synthesis. Moreover, for the first time atomistic models for these materials were obtained with realistic pore-surface roughness and details of the possible location of its interaction sites. Grand Canonical Monte Carlo (GCMC) simulations of nitrogen, methane and ethane adsorption in the materials pore models show excellent agreement with experimental results. In addition, their potential as design tools is explored by introducing surface groups for enhancing CO2 capture; and finally, application examples are presented for carbon dioxide capture from flue gases and for natural gas purification, as well as in the separation of n-butane / iso-butane isomers.