Oxidative degradation of aminosilica adsorbents relevant to post-combustion CO ₂ capture

Temperature swing adsorption is an interesting alternative to the benchmark aqueous amine absorption process using monethanolamine (MEA) for CO ₂ capture from post-combustion flue gases (containing 5-10% oxygen). Unlike the absorption process, the stability of aminosilica adsorbents remains relatively unexplored. Here, oxidative degradation of aminosilica materials is studied under accelerated oxidizing conditions to assess how different supported amine structures react with oxygen. It was found that both amine type and proximity have a significant effect on oxidative degradation rates. In particular, the supported primary and tertiary amines proved to be stable to the oxidizing conditions used, whereas the secondary amines degraded at elevated treatment temperatures. However, when primary amines separated from secondary amines by ethyl linkers are exposed to oxidative conditions, the primary amines in this adsorbent are no longer stable. The hypothesis that a co-operative oxidation mechanism exists is further tested by varying the alkyl chain length separating the amines.