Effect of Surface Organo-Silanization on SBA-15 Mesoporous Silicas in CO₂ Adsorption Processes: Design, Synthesis, and Computational Studies

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 CO2 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 CO2 sensitive groups in the other extreme; (i) hyperbranched polymeric PAMAM moieties, carrying multiple −NH2 groups, and (ii) a collection of linear functional ending groups such as −SH, −SO3H, −guanidine (Gdn), −NH2, −NCO, and −N3. 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 (SBA-15@NH2) under conditions relevant to CO2 capture (1 bar and 50 °C). We also found intriguing certain discrepancies observed between the calculated CO2 isotherms and the theorized binding energy in two of the materials. This will be addressed in the present work.

Capture of CO2 by Melamine Derivatives: A DFT Study Combining the Relative Energy Gradient Method with an Interaction Energy Partitioning Scheme

“…So far, the main existing technologies can be divided into three categories: absorption, adsorption and membrane technologies . The most used in industry is the absorption of CO 2 by amine solution, in general a solution of monoethanolamine (MEA). − However, the large energy needed for the regeneration of the solvent after capture makes this method far away from the ambitious but needed CO 2 capture cost of $20/ton, proposed by several USA and European research programs.…”

Understanding the coupling of non-metallic heteroatoms to CO2 from a Conceptual DFT perspective

“…The CO 2 absorption by amine solutions, specially monoethanolamine (MEA) [ 31 – 34 ], is frequently used industrially. Also, supported amines [ 34 – 37 ] and nitrogen heterocycles are capable of react with CO 2 [ 38 ].…”

“…The CO 2 absorption by amine solutions, specially monoethanolamine (MEA) [ 31 – 34 ], is frequently used industrially. Also, supported amines [ 34 – 37 ] and nitrogen heterocycles are capable of react with CO 2 [ 38 ]. In general, this reaction processess with the formation of the carbamic acid followed in some cases by deprotonation to yield the corresponding carbamate [ 39 – 41 ].…”