2024 AIChE Annual Meeting

(612d) Porous Colloidal Biphasic Solvents for CO2 Capture

Authors

Iqbal, M. N., Stockholm University
Hedin, N., Stockholm Univerisity
Anthropologic emissions of greenhouse gases is the main cause of global warming. The IPCC expects carbon sinks and negative emissions, particularly in sectors that are difficult to decarbonize, like the agricultural and transportation sector [1]. Combined bioenergy and carbon capture can contribute with such negative emissions. The benchmarking technology for CO2 capture from large point source flue gases uses an absorption-desorption process with a scrubbing liquid consisting of 30 wt-% monoethanol amine (MEA). The amines and the CO2 react with fast kinetics to form ammonium carbamates and ultimately bicarbonates. Temperature swings are used to regenerate the solvent resulting in a high-purity CO2 stream. However, the high water content in the liquid makes the regeneration step very energy intensive, and the formation of bicarbonates giving a high effectiveness is slow. Furthermore, leaching of the amines is detrimental due to their inherent toxic and corrosive nature. [2]-[4]

We are designing and developing a new type of scrubbing liquid to address the above described issues. It is based on colloidal and aminated mesoporous silica nanoparticles (A-Si-MNPs), and we hypothesize that we can synergistically combine the advantages of liquid scrubbing methods and methods using solid, aminated adsorbents. The solid support MNPs are pore-expanded SBA-15 type silica, which acts as a solid support for the amines. Owing to the high surface area of the SBA-15 (1027±41 m2∙g-1), a high degree of amination is expected, as a higher surface area generally corresponds to thinner walls, thus facilitating a high amine incorporation. The A-Si-MNPs were shown to significantly increase the CO2 adsorption in the solid state (1.35 mmol CO2/g at 15kPa, 20°C) as compared to the Si-MNPs, as expected from the formation of ammonium carbamates with the amines [5]. In addition to the high productivity expected from dispersed or suspended A-Si-MNPs, it is noted that the silica has a significantly lower specific heat capacity than water, which in turn is expected to reduce the heat needed for the regeneration.

Interestingly, the CO2-amine chemistry seems to destabilize the colloidal dispersions/suspensions. To investigate this further, we are studying if this biphasic behavior can be used to further reduce the heat needed for the regeneration. This could be achieved by separating the concentrated CO2-rich slurry and the lean water phase, and regenerate only the former. In conjunction with the stability study, we will investigate the properties of the dispersions/suspensions/slurries using a stirred cell reactor. We will also use catalysts that promote the bicarbonate formation and the overall productivity. Comparisons will be made with the benchmarking MEA-solvent.

[1] IPCC - working group III, “IPCC AR6 WGIII: CDR Factsheet.” IPCC.

[2] S. Kammerer, I. Borho, J. Jung, and M. S. Schmidt, “Review: CO2 capturing methods of the last two decades”.

[3] D. Aaron and C. Tsouris, “Separation of CO 2 from Flue Gas: A Review,” Separation Science and Technology, vol. 40, no. 1–3, pp. 321–348, Feb. 2005, doi: 10.1081/SS-200042244.

[4] C.-H. Yu, C.-H. Huang, and C.-S. Tan, “A Review of CO2 Capture by Absorption and Adsorption,” Aerosol Air Qual. Res., vol. 12, no. 5, pp. 745–769, 2012, doi: 10.4209/aaqr.2012.05.0132.

[5] D. J. Fauth, M. L. Gray, H. W. Pennline, H. M. Krutka, S. Sjostrom, and A. M. Ault, “Investigation of Porous Silica Supported Mixed-Amine Sorbents for Post-Combustion CO 2 Capture,” Energy Fuels, vol. 26, no. 4, pp. 2483–2496, Apr. 2012, doi: 10.1021/ef201578a.