Carbon dioxide capture using amine-impregnated HMS having textural mesoporosity

A series of HMS (hexagonal mesoporous silica) materials having different textural mesoporosities was synthesized using dodecylamine as a structure directing agent, which were employed as a host for supporting PEI (polyethylenimine) (PEI/HMS) as a CO2 capturing agent. The textural properties of the prepared materials were examined by XRD, N2 adsorption–desorption isotherms, and SEM. CO2 sorption/desorption measurements were carried out using a TGA unit using high purity (99.999%) CO2. The as-prepared HMS alone exhibited a moderate sorption capacity of 34 mgCO2mgCO2/gsorbent at 25 °C. The PEI/HMS prepared using a HMS having complementary textural mesopores exhibited CO2 sorption capacity of 128 mgCO2mgCO2/gsorbent with a 45 wt% PEI loading at 75 °C, whereas a sorption capacity of 94 mgCO2mgCO2/gsorbent only was obtained under the same loading level using a HMS host with negligible textural mesoporosity. In addition, we were able to increase the PEI loading to 60 wt% without losing the capturing efficiency of the former, and achieved a CO2 sorption capacity of 184 mgCO2mgCO2/gsorbent, one of the highest capturing capacities reported in the literature thus far under the given conditions. PEI/HMS exhibited only a minor drop in CO2 capture capacity during a 4 repeated cyclic sorption–desorption run at 75 °C.