Work

CO 2 -Triggered Sedimentation in Concentrated Dispersions of Aminated Silica for CO 2 Capture

Year: 2025

Type: article

Abstract: High Resolution Image Download MS PowerPoint Slide This study focused on CO 2 -triggered phase separation in concentrated dispersions of mono-, di-, and triaminated silica for CO 2 capture, based on the hypothesis of reduced regeneration energy coupled with the formation of a CO 2 -rich, water-lean sediment. The sedimentation of the CO 2 -rich and CO 2 -lean dispersions was studied using time-resolved optical transmittance measurements. The CO 2 capacity, reaction rate, diffusivity, and solubility of the dispersions were also studied. The involved CO 2 -amine chemistry was studied by using infrared (IR) and cross-polarization solid-state 13 C and 15 N NMR spectroscopy, and the fluid behavior of the dispersions was studied by rheology. The aminated silica was of the SBA-15 type and characterized by N 2 adsorption and desorption experiments, thermogravimetric analysis, powder X-ray diffraction, scanning and transmission electron microscopy, and crosspolarization solid-state 29 Si NMR spectroscopy. The derived energy balances for a simplified process indicated that the regeneration of the CO 2 -rich sediments results in an energy demand similar to that of 30 wt % ethanolamine (MEA) in water. The bounds of the energy balances were found to be limited by the somewhat low CO 2 capacities of the dispersions, which underscores the need for increasing the amino group density of the dispersions in future efforts. The observed changes in transmittance between the CO 2 -lean and CO 2 -loaded dispersions showed that sedimentation occurred within the first 10 min for the CO 2 -loaded dispersions, while the CO 2 -lean dispersions exhibited no change in transmittance after 60 min. The analysis of the pressure decay curves of the partial CO 2 pressure showed that the absorption rates of the dispersions were smaller than those of monoethanolamine (MEA) in water but were similar to the absorption rates of 2-amino-2-methyl-1-propanol (AMP) in water. The IR spectroscopic analysis was consistent with the formation of ammonium carbamates at a low CO 2 loading and the subsequent formation of HCO 3 – at a higher loading. The flow curves displayed rich and complex fluid behavior, which was strongly affected by the capture of CO 2 by the dispersions. Phenomena such as shear thinning, jamming, and thixotropy were observed.

Source: ACS Sustainable Chemistry & Engineering

DOI: 10.1021/acssuschemeng.5c05798