Potassium Iodide as an Amine Oxidation Inhibitor in CO2 Capture

Amine oxidation presents a major barrier to the wide-scale deployment of amine scrubbing for post-combustion carbon capture (PCCC). This paper reviews previous work on the use of "Inhibitor A" (Inh A) to minimize amine oxidation, and this will be the first time Inh A has been identified as potassium iodide (KI). KI is effective at mitigating oxidation in monoethanolamine (MEA) and piperazine (PZ) at absorber conditions during bench-scale experiments. Bench-scale experiments with methyldiethanolamine (MDEA) and PZ blends showed no oxidation inhibition from KI at absorber conditions. However, in bench- and pilot-scale experiments with high-temperature cycling, KI proved largely ineffective at mitigating the oxidation of MEA, MDEA, and PZ. While the inhibitor may change oxidation pathways during temperature cycling, such as catalyzing the oxidation of ethylenediamine (EDA) to ammonia, the addition of KI had no impact on the overall degradation rate of the amine solvent. Based on the results reported here, KI will not inhibit oxidation meaningfully in industrial PCCC. This work highlights the importance of testing oxidation inhibitors under realistic conditions to determine their viability on the industrial scale.