(152l) Amine-Modified Hyper-Cross-Linked Polymeric Resins for Economically Viable Biogas Upgrading

Addressing climate change, reducing greenhouse gas emissions, and expanding renewable energy sources to accommodate the growing population are among today's most pressing technological challenges. Biogas, a valuable renewable energy source, is produced from the anaerobic digestion of biodegradable organic matter and primarily consists of methane (CH₄) and carbon dioxide (CO₂), both potent greenhouse gases. To increase biogas' calorific value for injection into the natural gas grid or use as vehicle fuel, CO₂ must be separated from CH₄.

Hyper-cross-linked polymeric (HCP) resins are organic porous materials with properties such as low density, high specific surface area, and high mechanical stability, making them suitable for CO₂ adsorption. HCPs feature tunable porous structures and rigid networks that prevent porous wall collapse due to their high degree of crosslinking. Amine-modified HCP resins have been proposed for CO₂ separation from flue gases and air but their application in biogas upgrading and economic feasibility has not been thoroughly investigated.

This study explores the use of PEI-impregnated resin sorbents for CO₂ separation from biogas. The sorbent displayed the highest adsorption capacity of 2.7 mmol_CO2/g adsorbent at 30% PEI loading, which increased to 2.9 mmol_CO2/g adsorbent in the presence of moisture and remained stable across multiple adsorption-desorption cycles. In-situ DRIFTS studies indicated that CO₂ adsorption on PEI-impregnated sorbent aligns with the zwitterion reaction mechanism, and the sorbent could be fully regenerated at 100°C. The main costs of biogas upgrading are associated with adsorbent costs and regeneration operating costs. An economic feasibility analysis revealed that PEI-impregnated resin sorbents require lower capital and operating costs compared to conventional biogas upgrading technologies, suggesting that PEI-functionalized HCP resins are promising candidates for CO₂ separation in biogas applications.