The Role of Bicarbonate in Ion Speciation Plots in DEAB and Blended MEA-DEAB Systems, an NMR Study

Abstract:

The MEA-DEAB-CO₂-H₂O solutions contain complex ions in the solution. Carbamate (RNH-COO^-) and bicarbonate (HCO₃^-) anions are the major format of CO₂ dissolved in the solutions. The ion concentrations of both components are constrained by the reaction equilibrium and VLE model of CO₂-amine interactions. For the MEA-CO₂-H₂O systems, the majority of [CO₂]₀ is carbamate. For the DEAB systems, the majority is bicarbonate. The blended amine system such as MEA-DEAB-CO₂-H₂O contains both carbamate and bicarbonate at different ratios, which is affected by variations of amine ratio, CO₂ loading and operation temperatures. This work summarized VLE plots from ¹³C NMR analysis of single and blended amine solutions, both in room temperature (24°C) and higher temperature (70°C) to detect trend of the ratio of bicarbonate vs carbamate in the blended amine (MEA-DEAB) systems under both absorption and regeneration conditions. These experimental data indicated the carbamate exchange reaction is endothermic. With increase of temperature, ratio of bicarbonate increased accordingly and that of carbamate decrease. The increased concentrations of bicarbonate can facilitate the amine regeneration with reduced heat duty.

• Periodical: Key Engineering Materials (Volume 727)
• Pages: 870-877
• DOI: https://doi.org/10.4028/www.scientific.net/KEM.727.870
• Online since: January 2017
• Authors: Zhi Hao Yu, Lin Hua Jiang*
• Keywords: ¹³C NMR Spectroscopy, Amine Regeneration, Bicarbonate, Blended Amine Solutions, Carbamate, CO₂ Absorption, CO₂ Desorption, Single Amine Solutions, Vapor Liquid Equilibrium

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