(143h) Amine Functionalization of Hyper-Cross-Linked Polymer (HCPs) for CO2 Separation from Biogas

Climate change mitigation, lowering greenhouse gas emissions, and expanding renewable energy sources to match the growing population are among the most pressing current technological challenges. Biogas is a valuable renewable energy source generated from the anaerobic digestion of biodegradable organic matter, made up of carbon dioxide (CO₂) and methane (CH₄), two potent greenhouse gases. Although biogas could be directly utilized in combustion engines, CO₂ separation from CH₄ is necessary to increase biogas' calorific value so that the biomethane can be injected into the natural gas grid or used as a vehicle fuel [1].

Hyper-cross-linked polymeric (HCP) resins are organic porous materials used in CO₂ adsorption, primarily because of their properties such as low density, high specific surface area, and high mechanical stability [2]. HCPs have tunable porous structures and rigid networks that prevent the porous wall from collapsing owing to their high degree of crosslinking, making them excellent solid adsorbents. Recently, amine-modified HCP resins have been proposed and evaluated for CO₂ separation from flue gases and air [3]. However, its use in biogas upgrading and the economic feasibility evaluation of such adsorbents' practical application has not been explored in detail [4]. This work studied the use of PEI-impregnated resin sorbent for CO₂ separation from biogas. The sorbent exhibited the highest adsorption capacity of 2.7 mmol_CO2/g_ads at 30% PEI loading, increasing to 2.9 mmol_CO2/g_ads in the presence of moisture, and remained stable for several adsorption-desorption cycles. In-situ DRIFTS studies showed that CO₂ adsorption on PEI-impregnated sorbent is consistent with the zwitterion reaction mechanism, and the sorbent could be regenerated completely at 100°C. The upgrading cost of biogas is primarily dominated by the operating cost of regeneration and the adsorbent cost. Economic feasibility analysis projected that PEI-impregnated resin sorbent requires less capital and operating cost than conventional biogas upgrading technologies. Therefore, PEI-functionalized HCPs resins are promising for CO₂ separation from biogas.

References:

[1] X. Zhao, A. Naqi, D.M. Walker, T. Roberge, M. Kastelic,, B. Joseph, J.N. Kuhn, Sustainable Energy & Fuels (2019) 53949. 10.1039/C8SE00344K.

[2] H.R. Penchah, H.G. Gilani, A. Ghaemi, Journal of Chemical & Engineering Data (2020) 490513. 10.1021/ACS.JCED.0C00541.

[3] J. Wang, M. Wang, W. Li, W. Qiao, D. Long, L. Ling, AIChE Journal (2014) 97280. 10.1002/AIC.14679.

[4] O. Johnson, B. Joseph, J.N. Kuhn, Journal of Industrial and Engineering Chemistry (2021) 25563. 10.1016/J.JIEC.2021.07.038.