New developments on carbon dioxide capture using amine-impregnated silicas

A series of representative amines were impregnated on SBA-15 mesostructured silica. Ethylenediamine, 1,6-diaminohexane, hexamethyleneimine, tetraethylenepentamine (TEPA), branched polyethyleneimine (PEI), piperazine (PZ), and 4-amino-2-hydroxy-6-methylpyrimidine (PD) were used as impregnating agents. Impregnated materials were characterized by N₂ adsorption–desorption, elemental analysis and CO₂ adsorption–desorption. CO₂ analyses were performed at 45 °C with the aim of reproducing industrial post-combustion conditions. Relevant differences in CO₂ uptake were assigned to the kind of amino group used and their position in the molecule (i.e., primary, secondary or tertiary, isolated, close to aromatic rings…). PEI, TEPA and PZ were also impregnated over SBA-AP, i.e., SBA-15 grafted with aminopropyl-trimethoxysilane (AP), by using a double functionalization method. CO₂ uptake and amine efficiency (CO₂/N molar ratio) were found to depend on the nature of the impregnating molecule. Improved stability and CO₂ capture properties were obtained for samples impregnated over SBA-AP, achieving a CO₂ adsorption capacity of 104 mg CO₂/g ads (2.4 mmol CO₂/g ads) for SBA-AP–TEPA (45 °C, 1 bar), with an amine efficiency of 0.32 mol CO₂/mol N (SBA-AP–TEPA, 45 °C, 1 bar).