Experimental study on phase change solvents in CO2 capture by NMR spectroscopy

Abstract

Abstract2-(Diethylamino)ethanol (DEEA) and 3-(Methylamino) propylamine (MAPA) in combination may represent a promising absorbent system for CO 2 capture due to high CO 2 loading capacity, high equilibrium temperature sensitivity, low energy requirement for regeneration and relatively high reaction rate.Three different systems: DEEA-CO 2 -H 2 O; MAPA-CO 2 -H 2 O and DEEA-MAPA-CO 2 -H 2 O were studied quantitatively by NMR spectroscopy and the data are reported in the present work. The main products quantified for these systems are: carbonate-bicarbonate for the DEEA-CO 2 -H 2 O system; primary, secondary carbamate, dicarbamate for the MAPA-CO 2 -H 2 O system, and primary/ secondary carbamate, dicarbamate, carbonate/bicarbonate in blended DEEA-MAPA-CO 2 -H 2 O. The speciation data of the three systems were measured and reported in the present work. The blended system of 5M DEEA-2M MAPA can form two liquid phases after being loaded with CO 2 and both phases were analyzed quantitatively by NMR spectroscopy. The experimental data shows that the lower phase is rich in CO 2 and MAPA while the upper phase was lean in CO 2 and rich in DEEA. The ratio DEEA-MAPA in the lower phase increases with increasing partial pressure whereas for the upper phase the opposite is true.

Kinetics of CO2 absorption by aqueous N,N-diethylethanolamine solutions: Literature review, experimental results and modelling

“…NMR analysis shows that the upper phase consists mostly of DEEA, especially at low loadings (Ciftja et al, 2013). The present work suggests that DEEA clusters, which are present in DEEA aqueous solutions (including the aqueous blends of DEEA and MAPA), are precursors to the observed DEEA-rich liquid phase.…”

VLE data and modelling of aqueous N,N-diethylethanolamine (DEEA) solutions

“…The 5M DEEA 2M MAPA blend forms two phases upon CO 2 loading, and after separation almost all the CO 2 is present in the lower phase, which is also rich in MAPA. The upper phase consists mainly of DEEA and needs not to be sent to the stripper (Ciftja et al, 2013). Regenerating only a fraction of the solution can lead to lower operational cost on the stripping side of the process.…”

Screening and evaluation of novel biphasic solvents for energy-efficient post-combustion CO2 capture

“…This was probably due to their different phase transition behaviors (discussed in detail in Section 3.2) because the hydrophobic DMCA molecules in the upper organic phase had to diffuse to the interface of dual liquid phases, where they could react with dissolved CO 2 molecules facilitated by component A in the lower aqueous phase. In comparison, DEEA molecules were present in a homogeneous phase and thus encountered no trans-phase diffusion at the initial stage of CO 2 absorption before the dual phases were formed (Ciftja et al, 2013).…”

“…The team proposed a multistage extraction process configuration that applied an inert alkyl solvent to extract the unreacted amines in the aqueous phase and thus facilitate the regeneration reactions of the carbamate and bicarbonate species. A Norwegian research group Ciftja et al, 2013;Hartono et al, 2013) conducted quantitative speciation analyses and vapor-liquid equilibrium (VLE) and absorption heat measurements for a solvent blend of 2 M 3-(methylamino) propylamine and 5 M 2-(diethylamino) ethanol (DEEA) that could form dual phases after CO 2 was loaded. A similar study on CO 2 absorption and speciation analysis was conducted by Xu et al (2013a,b) for a different biphasic solvent, a blend of 2 M 1,4-butanediamine and 4 M DEEA.…”