CO₂ desorption tests of blended monoethanolamine–diethanolamine solutions to discover novel energy efficient solvents

Abstract

The CO 2 desorption tests were conducted at 363-378 K for 5.0 mol/L blended monoethanolamine (MEA)-diethanolamine (DEA) solutions to develop the energy efficient solvents with high CO 2 production and low energy consumptions. These desorption tests were performed with a recirculation process for various preloaded, 5 mol/L (4.5 + 0.5 to 0.5 + 4.5) MEA-DEA solutions to find out the optimized solvents with minimum heat duty. Therefore, 1-4 mol/L and 0.5-0.45 mol/L MEA-DEA solvents have larger CO 2 production (nCO 2 ) and lower heat duties (H CO 2 ) than 5 mol/L DEA under similar operation conditions. They have lower heat duty (510 and 538 kJ/mol) than DEA (572 kJ/mol) due to increased CO 2 desorption rates, despite 10% higher heat input (Q Total ) than DEA. Moreover, the critical points were studied as research focus of amine regeneration curves, along with reaction energy calculation. Finally, secondary amines blending minor MEA (<20%) as promotor turned out to be an alternative approach of solvents improvement with low energy requirement.

Study of “coordinative effect” within bi‐blended amine MEA + AMP and MEA + BEA at 0.1 + 2–0.5 + 2 mol/L with absorption–desorption parameter analyses

“…It is apparent that introducing MEA can enhance CO 2 absorption toward the single amine but deteriorate CO 2 desorption 14 due to its strong carbamate stability and higher energy cost 5 . However, a previous study indicated that blending MEA with DEA (0.5/4.5 or 1 + 4 mol/L) can reach lower heat duty than 5.0 M DEA 18 . The principle of that effect works as follows: Introducing small concentration of MEA will certainly increase heat input Q input to 5–10%, but it will boost CO 2 production to 10%–20% and then reduce heat duty ( H = Q input /nCO 2 ) to 5%–10% 20 .…”

“…A recent method of solvent improvement was the application of the “coordinative effect” by blending small amount of MEA into secondary amine (DEA) 16–20 or related blended amine solvents (BEA + AMP) since 2019. Liu 17 .…”

“…Liu 17 . and the author 18 discovered “coordinative effect” of MEA + DEA (RR'NH), which could facilitate CO 2 absorption 17 and desorption 18,19 simultaneouly. From the mechanism study of “coordinative effect,” 17,18 the potential amine candidate is secondary amine or other amines generating carbamate when amine reacts with CO 2 17 .…”

“…and the author 18 discovered “coordinative effect” of MEA + DEA (RR'NH), which could facilitate CO 2 absorption 17 and desorption 18,19 simultaneouly. From the mechanism study of “coordinative effect,” 17,18 the potential amine candidate is secondary amine or other amines generating carbamate when amine reacts with CO 2 17 . Later on, the author's group developed a new solvent improvement method: application of “coordinative effects” by blending small amount of MEA with other secondary amines (RR'NH) blends at specific ratios of 0.1–0.5/2.…”

Study of Catalytic CO2 Absorption and Desorption with Tertiary Amine DEEA and 1DMA-2P with the Aid of Solid Acid and Solid Alkaline Chemicals

“…An open recirculation-process (Figure S2) vessel equipped with an electrometer [9,26,37] was adopted to conduct the CO 2 desorption tests under atmosphere to extract DEEA and 1DMA-2P solvents at 1.0 mol/L, 1.5 mol/L and 2.0 mol/L, and two types of solid acid catalyst were used as γ-Al 2 O 3 and H-ZSM-5 representing Lewis acids and Brønsted acids [9,26]. The acidic catalytic conditions were 5.0 g, 7.5 g and 10.0 g, This CO 2 desorption process was similar to that of others in the literature [9,26].…”