Reuse and recycling of amine-functionalized silica materials for CO 2 adsorption

Abstract

Abstract The reuse and recycling of amine-silica materials as CO2 adsorbents were investigated for understanding their industrial viability. CO2 adsorbents were obtained by grafting of diethylenetriamine (DT) or impregnation of polyethyleneimine (PEI) onto SBA-15 silica. CO2 desorption conditions were evaluated, optimizing the time and temperature to reduce energy costs. In all cases, conditions as mild as 90 °C and 90 min were enough to completely remove all CO2 adsorbed. After that, a number of adsorption-desorption cycles at 110 °C for DT (60 min) and PEI (75 min) samples were carried out in order to study their cyclability. The recycling of CO2 adsorbents after their lifespan was studied by analysing the physicochemical properties and CO2 uptake of recycled samples obtained by calcination and subsequent re-functionalization with DT or PEI. Materials obtained after grafting the calcined samples exhibited progressively thicker silica walls and lower silanol surface concentration, yielding a smaller amine efficiency during CO2 capture. On the contrary, materials obtained after impregnating the calcined samples maintained their CO2 adsorption properties even after 6 cycles, without significant changes in their silica structure or amine efficiency for CO2 adsorption.