Study of Formation of Bicarbonate Ions in CO₂-Loaded Aqueous Single 1DMA2P and MDEA Tertiary Amines and Blended MEA-1DMA2P and MEA-MDEA Amines for Low Heat of Regeneration

The formation of bicarbonate ions in an amine solution during CO₂ absorption results in lowering the heat duty for amine solvent regeneration in the CO₂ capture process because bicarbonate breakdown needs the lowest energy input to release CO₂. In this study, bicarbonate formation was conducted for two mixed solvents consisting of tertiary amines (1DMA2P (1 M) or MDEA (1 M)) blended with MEA in order to determine both formation rate and capacity of bicarbonate ions as compared to MEA alone. The amines and concentrations used in the study were MEA (5 M), MEA-MDEA (5:1 molar ratio, 6 M total), and MEA-1DMA2P (5:1 molar ratio, 6 M total) at various CO₂ loadings. The formation of bicarbonate ions was evaluated using ¹³C NMR technique at 293.15 K. The results show that for the single tertiary amine system higher concentrations of bicarbonate ions were formed for MDEA than for 1DMA2P for the same CO₂ loading. The results for the blended amine systems showed that bicarbonate ions were generated at CO₂ loadings lower with MEA alone than with MEA-1DMA2P generating bicarbonate ions at a CO₂ loading (0.34 mol CO₂/mol amine) lower than that with MEA-MDEA (0.38 mol CO₂/mol amine). Thus, as an additive in MEA, 1DMA2P has a better potential than does MDEA to generate bicarbonate ions at a leaner CO₂ loading with the attendant lowering of the regeneration energy. (Graph Presented).