Antioxidation Strategy of Modification with Low-Dose Inhibitors to Solid Amine Adsorbents for Long-Term Cyclic Carbon Capture from O ₂ -Containing Flue Gas

The existence of O₂ in flue gas, which can induce oxidative degradation and cause adsorption capacity losses, has been an obstacle for solid amine adsorbents in practical applications. Herein, a simple and scalable synthesis of PEI-impregnated silica modified with low-dose inhibitors is reported. Compared to previous studies, the novelty of this work lied in its simplicity and its ability to maintain high adsorption capacity (over 170 mg/g) when achieving excellent antioxidation and antiurea effects. The strategy can slow down the oxidation kinetics as well as relieve oxidative degradation of the adsorbents under conditions of high oxidation temperature, high O₂ concentration, and long oxidation time. The cyclic stability can be increased by 43.8%, and the O₂ resistance can be improved by 66.8%. Using a multitechnique approach, we have unraveled the effects of the separate and coexisting presence of CO₂ and O₂ in long-term applications and provided important guidance for the selection of certain inhibitors (NaH₂PO₄, Na₃PO₄, or HCOONa) based on actual application situations. This study demonstrated that the adsorbent modified with NaH₂PO₄ can avoid the weakening of antiurea effects when CO₂ and O₂ coexist, while Na₃PO₄ can still exhibit the overall effect of high cyclic stability even with the weakened antiurea effects; thus, NaH₂PO₄ and Na₃PO₄ have the potential for long-term carbon capture from O₂-containing flue gas.