Effect of Surface Organo-Silanization on SBA-15 Mesoporous Silicas in CO<sub>2</sub> Adsorption Processes: Design, Synthesis, and Computational Studies
Eduardo J. Cueto‐Díaz, Alberto Castro Muñiz, Fabián Suárez‐García, Ibón Alkorta, María Pilar Valles González, Eva Mateo‐Martí
Abstract
Carbon dioxide solid sorbents produced from mesoporous functionalized silica microparticles (SBA-15) have been investigated (i) theoretically using density functional theory and (ii) evaluated empirically for assessing their CO 2 adsorption capacity. Two different families of organosilyl groups have been tested possessing a common anchoring group (silanol), in one extreme, but bearing two different types of CO 2 sensitive groups in the other extreme; (i) hyperbranched polymeric PAMAM moieties, carrying multiple −NH 2 groups, and (ii) a collection of linear functional ending groups such as −SH, −SO 3 H, −guanidine (Gdn), −NH 2, −NCO, and −N 3 . The adsorption isotherms revealed that SBA-15 bearing (3-aminopropyl)triethoxysilane (APTES) showed an impressive 3.4-fold adsorption enhancement at 1 bar and 50 °C when compared to the pristine SBA-15, following a straightforward synthetic protocol. The maximum adsorption capacity was increased from 0.34 mmol/g (SBA-15) to 1.15 mmol/g ( [email protected] 2 ) under conditions relevant to CO 2 capture (1 bar and 50 °C). We also found intriguing certain discrepancies observed between the calculated CO 2 isotherms and the theorized binding energy in two of the materials. This will be addressed in the present work.