Stabilization of Monoethanolamine Solutions in Carbon Dioxide Scrubbers.

Abstract

Monoethanolamine (MEA), the regenerative absorbent used in C02 scrubbers aboard nuclear submarines, is now stabilized with a chelating agent, the monosodium salt of , -diethanolglycine (VFS). This inhibitor is not effective against oxidative degradation at 55°C. in the presence of procatalytic metals, particularly copper. Effective stabilization in the presence of copper is given by tetrasodium (ethylenedinitrilo) tetraacetate (EDTA). At 98°C ., with small quantities of typical metal contaminants added, both VFS and EDTA are required for stabilization. The additive combination is ineffective at 138°and 149°C. with limited amounts of oxygen present. Pyrolytic stability of the formulation is adequate at these temperatures. VFS and EDTA are both true antioxidants for MEA in their own right. Their reactivity with peroxides, and their prevention of peroxide formation in oxidized MEA, suggest that their antioxidant activity results from an ability to interrupt an autocatalytic oxidation chain reaction. Less efficient additives did not prevent peroxide formation in MEA.

Influence of Dissolved Metals and Oxidative Degradation Inhibitors on the Oxidative and Thermal Degradation of Monoethanolamine in Postcombustion CO2 Capture

“…In this case, metals facilitate the propagation steps by catalyzing the generation of radicals from hydroperoxides as presented in Figure 1 15,16 . Hydroperoxides are generated by the presence of O 2 in water and their presence in oxidized MEA solutions has been evidenced previously 10 , which further supports this reaction pathway. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 Moreover, the presence of hydroperoxides is also due to the catalytic action of metals.…”

Experimental Evaluation of Effect of Oxidative Degradation of Aqueous Monoethanolamine on Heat of CO2 Absorption, Vapor Liquid Equilibrium and CO2 Absorption Rate

“…The catalytic effect of dissolved metals present in MEA solutions on the oxidative degradation rate has been reported [6]. In recent work, this effect was analyzed for the presence of ammonia as an indicator of MEA oxidative degradation.…”

Oxidation Inhibitors for Copper and Iron Catalyzed Degradation of Monoethanolamine in CO2 Capture Processes

“…Experiments from the 1960s, performed by the U.S. Department of the Navy, identified EDTA as an additive to stabilize MEA solutions to oxidative degradation. 10,42,43 These studies also identified bicine as a stabilizer, but it was much less effective. Previous studies in this research group confirmed these findings and found that EDTA was the most effective chelating agent for both Fe and Cu.…”