Selective separation of CO2–CH4 mixed gases via magnesium aminoethylphosphonate nanoparticles

Abstract

Magnesium 2-aminoethylphosphonate (Mg₂O(2AEP) × 4H₂O) nanoparticles (particle diameter: 20–30 nm; specific surface area: 360 m² g⁻¹) are presented for selective separation of CO₂ and CH₄. Due to the base amino function, the nanoparticles can reversibly absorb CO₂ with a maximal uptake of 153 mg g⁻¹. Absorption and desorption are studied by infrared spectroscopy as well as by gravimetric sorption analysis. Furthermore, Mg₂O(2AEP) × 4H₂O shows reversible selective separation of CO₂ from CH₄. Here, pure and mixed gas adsorption isotherms (25 °C, 25 bar) of CO₂ and CH₄ show maximal uptakes of 153 mg g⁻¹ (CO₂) and 15 mg g⁻¹ (CH₄). Especially, data of mixed gas isotherms are comparably rare, but highly relevant for material characterization. Experimental isotherms were fitted by a dual-site Langmuir isotherm model (CO₂) and a Tòth model (CH₄). Mixed adsorption isotherms were modelled by volumetric-chromatographic methods resulting in a selectivity of α = 8 to 20.