(514ae) Biogas Upgrading to Methane Using Amine-Impregnated Resins

Separation of CO₂ from CH₄ is important for increasing the heating value of biogas prior to use as a vehicle fuel or for natural gas grid injection. Solid porous adsorbents are considered as a promising technology for biogas upgrading because of low energy consumption and low capital investment in comparison to conventional separation methods such as ammonia or amine solvent absorption. The use of porous materials such as activated carbons (AC)¹, zeolites², metal-organic frameworks (MOFs)³, covalent organic frameworks (COFs)⁴, and mesoporous silica⁵ have been extensively researched in CO₂ separation technologies. However, many of these materials exhibit poor selectivity, low adsorption capacity, poor water resistance, and low tolerance to impurities present in LFG, which limit their applications. Commercial adsorption resin, HP2MGL, is a crosslinked polymethacrylate with a porous structure and has been successfully modified with PEI and used in separating low-concentration CO₂ from atmospheric air⁶. The objective of this work is to evaluate its potential for use with biogas upgrading.

In the present work, we synthesized the PEI-impregnated polymeric resin (HP2MGL) sorbent for the utilization in biogas upgrading to methane via CO₂ adsorption for the first time. Samples were characterized using N₂ physisorption, FTIR, CO₂ chemisorption, and in-situ DRIFTS techniques. Through the characterization of the pore properties and chemical components of the sorbent, we explored the underlying causes of parameter influence and the potential degradation mechanism. The effects of loadings, adsorption, and regeneration were studied. The sorbent exhibited the highest adsorption capacity of 2.73 mmol_CO2/g_ads at 30% amine mass loading, with negligible CH₄ adsorbed in simulated biogas experiments, proving a high affinity towards CO₂ over CH₄. In the presence of water, the saturation capacity of the sorbent increased to 2.92 mmol_CO2/g_ads. The sorbent was regenerated completely at 100 °C.Cyclic stability, tolerance of impurities such as H₂S in the feed gas and column breakthrough experiments will be conducted in a fixed-bed system, in addition to the test of the economic viability of the PEI-impregnated resin via techno-economic analysis and results will be reported.

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