Structural properties and reactivities of amino-modified silica fume solid sorbents for low-temperature CO2 capture

In this work, diisopropanolamine (DIPA) and 3-aminopropyltriethoxysilane (APTS) were respectively supported on hydrated silica fume particles by the impregnation method. The amino-modified silica fume solid sorbents were characterized, and their reactivities toward CO2 were evaluated using a thermogravimetric analyzer. All the prepared solid sorbents exhibited a type IV isotherm with a hysteresis loop of type H3. Due to the blocking of micropores and some mesopores, the specific surface areas of the sorbents were significantly reduced when DIPA or APTS was supported. The reactivity of DIPA/silica fume sorbents toward CO2 was higher than that of APTS/silica fume sorbents. The DIPA/silica fume sorbent prepared at a weight ratio of 1.0/1 had a maximum CO2 capture capacity of 1.25 mmol/g sorbent at a relatively low temperature of 30 °C, where a CO2/N molar ratio of 0.41 was achieved. The incomplete amino utilizations are mostly due to the thermodynamic equilibrium at the tested temperatures and partly due to the limitations of CO2 mass transfer in the sorbents. Furthermore, the multiple adsorption/desorption cycling results indicate that the solid sorbents are quite stable and regenerable.