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

Amine-functionalized materials have been widely investigated as promising candidates for CO2 capture. However, they are prone to degradation in the presence of O2, resulting in loss in the CO2 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 CO2 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.