(537g) Colloidal Aminated Porous Liquids (CAPLs) – a Novel Approach to CO2 Capture

CO₂ is industrially separated at post-combustion conditions via scrubbing, where the 30 wt% aqueous monoethanolamine (MEA) solution is part of the benchmarking technology. Scrubbing suffers from several drawbacks. The high energy demand related to the regeneration of the solvent is the main one, but MEA is corrosive and tends to leach, which, due to its toxicity, poses a serious issue. [1]

As an alternative to MEA, colloidal aminated porous liquids (CAPLs) represent an alternative approach to CO₂ separation where these drawbacks can be mitigated. The CAPLs of this study use amines that are grafted and polymerized across porous silica supports. The small aminated colloids can be dispersed and concentrated in water. We hypothesize several advantageous properties, such as a decreased heat capacity stemming from the properties of the aminated silica particles, and that the chemical anchoring of the amines reduces amine leaching and shields them chemically towards decomposition.

We have studied aminated silica for CO₂ capture [2], [3], and, here, we synthesized colloidal and small particles of mesoporous type SBA-15 silica. The SBA-15 was pore-expanded using swelling agents, ensuring a presence of large pores to improve on the diffusion of CO₂ and increase the mass-specific amination. BET analysis of the pristine silica showed a surface area of 723 m²/g and a pore size of 12.6 nm.

Different types of aminated organosilanes are chemically tethered via post-grafting methods. The resulting sorbents show high capacities (with preliminary values up to 1.87 mmol CO₂/g-dry-adsorbent with the aminosilane APTES). We expect lower regeneration energy for the CAPLs compared to the benchmark, due to the thermal properties of the silica support and the expected high CO₂ uptake. In the future, we will explore the use of different amines, improve on the amine density, optimize the redispersion of the aminated silica, and assert minimal amine leaching and emission of amine decomposition products.

[1] P. Luis, "Use of monoethanolamine (MEA) for CO₂ capture in a global scenario: Consequences and alternatives," Desalination, vol. 380, pp. 93-99, 2016.

[2] A. E. Szego, A. Jaworski and N. Hedin, " Chemisorption of CO₂ on diaminated silica as bicarbonates and different types of carbamate ammonium ion pairs," Material Advances, vol. 2, pp. 448-454, 2021.

[3] A. Baroz, G. Zhao and N. Hedin, "Carbon Dioxide Sorbents with Propylamine Groups-Silica Functionalized with a Fractional Factorial Design Approach," Langmuir, vol. 27, pp. 3822-3834, 2011.