New developments on carbon dioxide capture using amine-impregnated silicas

Abstract

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).