Inhibitors of Oxidative Degradation of Polyamine-Modified Silica Sorbents for CO2 Capture

Amine-functionalized materials have been widely investigated as promising candidates for CO 2 capture. However, they are prone to degradation in the presence of O 2, resulting in loss in the CO 2 capture ability as well as a decrease in the sorbent lifetime. In this study, we evaluated the effect of different oxidation inhibitors on degradation of polyamines, including tetraethylenepentamine- and polyethylenimine-impregnated mesoporous silica. Sulfur-containing compounds and traditional antioxidants were selected as additives. Oxidative degradation tests of the amine solid sorbents were performed in a packed-bed reactor equipped with a temperature controller. The results showed that traditional antioxidants, such as butylated hydroxytoluene, N, N ′-diphenyl-1,4-phenylenediamine, N, N ′-di-2-butyl-1,4-phenylenediamine, 2,2′-thiodiethylene bis[3-(3,5-di- tert -butyl-4-hydroxyphenyl)propionate], and pentaerythritol tetrakis[3-(3,5-di- tert -butyl-4-hydroxyphenyl)propionate], catalyzed oxidative degradation. In contrast, sulfur-containing additives, which owe their effectiveness to free-radical scavenging and peroxide decomposition actions, decreased the oxidation rate. Amine solid sorbents containing such additives had 1.5–2 times higher CO 2 adsorption capacity retention values than the nonadditive sorbents under accelerated oxidation conditions. Furthermore, the long-term stability of the amine solid sorbents over 15 months storage was demonstrated. These sulfur-containing additives also delayed sorbent degradation.