Amine-modified ordered mesoporous silica: The effect of pore size on CO₂ capture performance

Highlights: • Larger pore size could decrease the mass transfer resistance and increase the interaction between CO₂ and TEPA. • The CO₂ uptakes of sorbents were enhanced in the presence of moisture. • The sorbents are stable and regenerable under test conditions. - Abstract: The objective of current research is to investigate the effect of pore size of mesoporous silica supports on the CO₂ capture performance of solid amine sorbents. Two ordered mesoporous silicas (OMS) with different pore sizes (5.6 nm and 7.6 nm) were synthesized as tetraethylenepentamine (TEPA) supports. A serious of techniques, such as physical adsorption, infrared spectroscopy and thermal gravimetric analysis were used to characterize the solid amine sorbents. The CO₂ capture performances of the sorbents were evaluated using breakthrough method with a fixed-bed reactor equipped with an online mass spectrometer. The experimental results indicate that the pore size has significant influence on CO₂ capture performance. Larger pore size could decrease the mass transfer resistance and increase the interaction between CO₂ and TEPA. Therefore, OMS-7.6 is better than OMS-5.6 as amine support. The highest CO₂ sorption capacities achieved with OMS-7.6 with 50 wt% TEPA loading (OMS-7.6-50) in the absence and presence of moisture are 3.45 mmol/g and 4.28 mmol/g, respectively, under the conditions of 10.0% CO₂/N₂ mixture at 75 °C. Cyclic CO₂ adsorption–desorption experiments indicate that the solid amine sorbents are fairly stable and regenerable