Influences of Epoxide Functionalization and PEG Additives on Oxidation Stability and CO ₂ Adsorption Properties of Polyethylenimine/Silica Adsorbents

The epoxy alkane functionalization of amine is one efficient strategy to mitigate the oxidative degradation of poly(ethylenimine) (PEI)-impregnated solid amine adsorbents. Herein, the degree of modification and epoxy butane (EB) modified amine loading are systematically regulated to explore their effects on the oxidation stability of silica-supported solid amine adsorbents. In addition, the impacts of polyethylene glycol (PEG) on antioxidation behavior and CO2 uptake are also examined. The EB modification strategy markedly inhibits amine oxidation without significantly compromising the adsorption capacity. The adsorption capacity of 11EB-40PEI/C807 is 10% higher than that of 40PEI/C807 with an improved antioxidation performance. The antioxidant capability increases with increasing EB-PEI loadings. After oxidative aging at 110 °C for 12 h, the optimal 22EB-40PEI/C807 adsorbent retains 94.44% of its initial capacity (1.80 mmol/g in 10% CO2). In over 100 adsorption–desorption cycles under air desorption conditions, the EB-modified adsorbent exhibits a significantly improved long-term cycling stability. The degradation rate of EB-modified adsorbents is remarkably suppressed, showing a reduction of up to 69.65% compared with the unmodified 40PEI/C807 adsorbent. PEG exhibits no notable benefits with respect to the improvement of oxidation resistance in amine-based adsorbents, while the thermal treatment is found to enhance the CO2 adsorption capacity of PEG-doped adsorbents up to ∼20% attributed to PEI chain mobility changes.