https://doi.org/10.1016/j.seppur.2020.118193
“Obtaining and treating vapor–liquid equilibrium data, kinetic rate data and mass transfer rate data can be incredibly time-consuming. For a quick evaluation of a large number of new solvents, fast methods such as checking their CO2 absorption capacities and absorption rates in a bubbling cell can be very practical.
Surely, this type of data is hierarchically less meaningful than VLE or kinetics. We are not making an unfair distinction in stating so. The CO2 capacity of a solvent is nothing more than one single vapor–liquid equilibrium point, taken at one single CO2 partial pressure and one single temperature. Similarly, its rate of absorption is confined by the very specific, hardly scalable experiment of bubbling CO2 into one flask of solvent. In other words, one can obtain capacity and rate information from VLE and kinetic data, but not the opposite.
And yet, some reports on rate and capacity are the most interesting one can find regarding water-lean solvents. Woertz [33] screened more than 20 different solvents at about 540 kPa of CO2 partial pressure and 25 °C, and many of the combinations that outperformed their aqueous counterparts (e.g.: aqueous MEA mixed DEGDME or NMP) are still being studied and re-invented to this day. Woertz [33] was also the first to note down the shifting in absorption rates in water-lean solvents, simply by writing down ‘fast’ or ‘slow’ on a list with diverse formulations, thus registering that absorption in TEG-MEA-water mixtures is particularly morose.
Going into details over each one of the publications presented on Table 7 would be too much for this review. Instead, we will quickly mention some of the topics that stand out as particularly interesting. Woertz et al. [33] identify remarkable performances in water-lean solvents with N-methyl-2-pyrrolidone and N,N-dimethylformamide. Another remarkable performance for N-methylformamide is observed by Bougie et al. [162]. Bougie et al. [162] additionally demonstrate how the temperatures of water-lean solvents with low volatility increase the most upon absorbing CO2, following the order N-methylformamide > DEGMEE > ethylene glycol/1-propanol > water in nonaqueous solvents with MEA.”
“Table 7. Publications that compare capacity and rate in water-lean solvents.”
Solvents with typical alkanolamines and piperazines | ||
---|---|---|
Reference | Amines | Diluents |
[33] | MEA, DEA, DIPA | Various |
[179] | MEA, DEA, CHA | BP, CH, DEG, MeOH, PEG400 |
[31] | MEA | Various |
[177] | MEA | PEG20000 |
[176] | MDEA | PEG20000 |
[56] | MEA | 1BuIMI |
[178] | MEA, DEA, DGA | PEG200, PEG300, PEG400 |
[175] | MEA, DEA/PZ, MDEA/PZ, AMP/PZ | TOU |
[180] | PZ/DETA | DEG, MeOH |
[27] | MEA, DEA, TEA, AMP, MMEA | Various vegetable oils |
[181] | DETA/PZ | DEG |
[162] | MEA | 1PrOH, CARB, MEG, NMF |
[182] | MEA, LysK, ProK | CARB, 2EE |
[48] | MEA, AMP, EAE, IPAE | Various alcohols |
Solvents with organic amines and aminoacids | ||
Reference | Amines | Diluents |
[183] | DMA | MeOH, NMP, TMS |
[184] | DBA | EtOH |
[173] | ProK | EtOH |
[174] | ProK | EtOH |
[185] | TBA | EtOH |
[171] | Various ethylenediamines | |
Solvents relying on phase separation | ||
Reference | Amines | Diluents |
[186] | MEA, DEA | 1HeOH, 1OcOH, 2EHeOH |
[187] | AMP | NMP, TEGDME |
[188] | TETA | EtOH |
[189] | MAPA | DMF |
[190] | MEA | 1PrOH |
[191] | DETA | DEGDME, DMC, EtOH, NMP |
[192] | PZ | DMF |
[193] | TETA, AMP | EtOH |
[194] | TETA | PEG200 |
[195] | DETA | TMS |
“Unremarkable or rather bad performances are observed for all oils [27] and polyethylene glycols [96], [176], [177], [178], which have been seen to decrease both capacities and absorption rates when mixed with amines. Sridharan and Sharma [179] were the first authors to register the reduction of mass transfer coefficients with the addition of glycols.”