Search

The non-aqueous solid-liquid biphasic solvent of 2-amino-2-methyl-1-propanol (AMP)/piperazine (PZ)/dipropylene glycol dimethyl ether (DME) features a high CO 2 absorption loading, favorable phase separation behavior and high regeneration efficiency. Different with the liquid-liquid phase change solvent, the reaction kinetics of CO 2 capture into solid-liquid biphasic solvent was rarely studied. In the present work, the reaction kinetics of CO 2 absorption into AMP/PZ/DME solid-liquid biphasic solvent was investigated into the double stirred kettle reactor. The absorption reaction followed a pseudo-first-order kinetic model according to the zwitterion mechanism. The overall reaction rate constant (k ov) and the enhancement factor (E) of CO 2 absorption both increased with increasing temperature. The total mass transfer resistance of the absorbent decreased with increasing temperature and increased with increasing absorption loading, so the higher reaction temperature was conducive to the absorption, and the liquid phase mass transfer resistance was the main factor affecting the absorption rate. [ABSTRACT FROM AUTHOR]

[Display omitted] • A strategy that using AMP as a gelatinous product inhibitor in NNAs was proposed. • AMP-regulated NAAs did not yield insoluble gelatinous products during CO 2 absorption. • AMP-regulated NAAs featured good CO 2 capture performance. • CO 2 absorption mechanism was studied based on 13C NMR and theoretical calculations. • The inhibitory mechanism of AMP on the formation of gelatinous products was clarified. Diamines or polyamines with two or more amino groups are suitable for formulating non-aqueous absorbents (NAAs) with high CO 2 loading capacity and low regeneration energy consumption. However, these two types of amines in NAAs are prone to produce insoluble gelatinous products after absorbing CO 2 , resulting in difficult operation of the CO 2 capture system. In this study, by using 2-amino-2-methyl-1-propanol (AMP) as an inhibitor, the insoluble gelatinous products of the aminoethylethanolamine (AEEA)-N-methyl-2-pyrrolidone (NMP) (A-A-N) and 3-(methylamino)propylamine (MAPA)-NMP (M-A-N) NAAs were successfully eliminated. The experimental results showed that the AMP-regulated NAAs possessed a high absorption rate, high CO 2 loading capacity, excellent desorption efficiency, and stable recyclability. The reaction mechanism of CO 2 absorption and the inhibitory mechanism of AMP on the formation of gelatinous products were comprehensively elucidated. Taking the A-A-N system as a representative, AEEA reacted with CO 2 to form zwitterionic protonated carbamate species (AEEACO 2 − (P) H+ (S)), which tended to self-aggregate via hydrogen-bond interaction, resulting in the formation of insoluble gelatinous products. With the introduction of AMP, the AMP-derived products could combine easily with AEEACO 2 − (P) H+ (S) via strong electrostatic attraction to form ion pairs, preventing the AEEACO 2 − (P) H+ (S) molecules from self-aggregating to form insoluble gelatinous products. The regeneration heat duty of the A-A-N system was 1.89 GJ∙ton−1 CO 2 , which was 49.9 % lower than that of the benchmark 30 wt% MEA. Overall, introducing AMP as a gelatinous product inhibitor was beneficial for the development of NNAs with high CO 2 absorption capacity and low-energy consumption. [ABSTRACT FROM AUTHOR]

The large-scale deployment of non-aqueous amine solution for carbon dioxide (CO 2) capture is mainly limited by its high viscosity, even insoluble substances in saturated solution, which may result in equipment fouling and pipeline blockage. To avoid this problem, the polyamine 1,5-diamino-2-methyl-pentane (DA2MP) was screened as the main absorbent to ensure the high absorption load. While 2-amino-2-methyl-1-propanol (AMP) was used as the regulator to reduce the viscosity and eliminate insoluble substances, which dissolved in n-propanol (PrOH) to from the novel non-aqueous absorbent for CO 2 capture. The CO 2 absorption load of the novel absorbent was 0.95 mol·mol−1, and the viscosity of saturated solution was only 15.00 mPa·s, remarkably lower than that of the solution without AMP regulation. The solution maintained 97% of its initial CO 2 absorption capacity after fourth regeneration cycle. The regulation mechanism was investigated using 13C nuclear magnetic resonance (NMR) and quantum chemical calculations. It was proved that a strong and dense hydrogen bond network between DA2MP-carbamates was formed due to the self-deprotonation process, leading to insoluble products in the saturated DA2MP/PrOH solution. Through AMP regulation, there was another type of DA2MP-carbamates deprotonated by AMP formed in the solution with less hydrogen bond network, which could further react with PrOH to produce alkyl carbonates, achieving the elimination of insoluble products and reducing viscosity. Overall, the total regeneration energy consumption was 1.86 GJ·ton−1 CO 2 , only 50.27% of that of the benchmark monoethanolamine (MEA)-based solution, which would be a promising candidate for CO 2 capture. [Display omitted] ● Alkanolamine regulator was proposed to reduce the viscosity of non-aqueous solution. ● AMP was screened as the best alkanolamine regulator. ● AMP changed the structure of CO 2 product and converted it into alkyl carbonate. ● Reaction activation barriers for deprotonation process were decreased by AMP. ● The weak interaction between CO 2 product was revealed by DFT calculation. [ABSTRACT FROM AUTHOR]

[Display omitted] • Proposing an innovative strategy of using a regulator to trigger the phase transition of PCAs. • The AEEA/EAE/PMDETA/DMSO PCA exhibited tunable phase transition behavior. • The AEEA/EAE/PMDETA/DMSO PCA featured good CO 2 absorption and desorption performance. • The AEEA-regulated phase transition mechanism was elucidated from the molecular level. • The combined sensible heat and latent heat amounted to 0.32 GJ·ton−1 CO 2 , 84% less than 30 wt% MEA. Secondary amines are highly suitable candidates for constructing non-aqueous phase change absorbents (PCAs) that boast low viscosity and regeneration heat. However, the secondary amine-based PCAs often encounter the challenge of inadequate phase separation. This study proposed an innovative strategy of tailoring the polarity of absorption products to facilitate the controllable phase transition of the secondary amine-based PCA. Specifically, using aminoethylethanolamine (AEEA) as a regulator of product polarity to endow the 2-(ethylamino)ethanol (EAE)/pentamethyldiethylenetriamine (PMDETA)/dimethyl sulfoxide (DMSO) non-aqueous absorbent with tunable liquid–liquid phase transition behavior. The AEEA/EAE/PMDETA/DMSO (A/E/P/D) PCA realized a high CO 2 loading of 0.77 mol·mol−1, with over 92% of the absorbed CO 2 being enriched in the CO 2 -rich phase, which exhibited a low viscosity of 13.83 mPa·s. The A/E/P/D PCA also possessed good reusability, maintaining a cyclic loading of 0.65 mol·mol−1 even after five absorption–desorption cycles. Analysis of the phase change mechanism indicated that AEEA reacted with CO 2 to form highly polar AEEA-derived products, which played a pivotal role in driving the phase transition of the A/E/P/D system. In brief, the AEEA-derived product easily combined with polar DMSO, creating a "polar sink" that continually attracted the medium-polar EAE-derived products. Consequently, these products clustered together to form the CO 2 -rich phase with less polar PMDETA being isolated to form the CO 2 -lean phase. Moreover, estimation of the regeneration heat demonstrated that the combined sensible heat and latent heat of A/E/P/D amounted to 0.32 GJ·ton−1 CO 2 , representing a significant reduction of 84% compared to 30 wt% MEA. This study provided a novel idea to manipulate the phase behavior of PCAs and offered a promising A/E/P/D PCA for energy-efficient CO 2 capture. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel DBAPA absorbent featured 'self-extraction' property was used for CO 2 capture. • The saturated solution could regenerate efficiently by thermal desorption at 98 °C. • The self-extraction mechanism was clarified by theoretical and experimental analysis. • The polarity reversibility of DBAPA resulted in the performance of self extraction. Due to the strong bonding of amino groups with CO 2 , the alcohol amine-based absorbents for CO 2 capture suffer the disadvantage of high regeneration temperature and energy consumption. To promote the energy-saving regeneration, a novel 3-Dibutylamino-propylamine (DBAPA) aqueous absorbent featured 'self-extraction' property was proposed, for which the fresh solution maintained liquid–liquid two-phase and became homogeneous after CO 2 absorption. Due to the self-extraction regulation, its CO 2 products could be regenerated at a low temperature below the boiling point of water (98 °C). It kept 81.98 % of its initial loading (1.27 mol·mol−1) after the first regeneration and maintained 73.17 % after the sixth regeneration cycle at 98 °C, much higher than that of MEA (28.96 %). Based on the results of 13C NMR and quantum chemical calculations, the self-extraction regulation mechanism of DBAPA for CO 2 capture was clarified. It was proved that there was a vast polarity difference between DBAPA and H 2 O, resulting in phase separation before absorption. With the increasing CO 2 loading, CO 2 reacted with DBAPA to form DBAPA-carbamate, and the solution became homogeneous because of the increasing polarity of the CO 2 products and the strong hydrogen bonds between the products and H 2 O. The amine recovered to its low polarity during the desorption process, and the intermolecular hydrogen bonding with H 2 O decreased. DBAPA separated from the main solution to the upper phase, promoting the regeneration rate at 98 °C. Based on this self-extraction property, the regeneration energy consumption of DBAPA was estimated to be 1.89 GJ·ton−1 CO 2 , which was much lower than that of MEA (3.77 GJ·ton−1 CO 2). The results indicated that the novel DBAPA aqueous absorbent with self-extraction characteristics had good energy-saving potential for CO 2 capture. [ABSTRACT FROM AUTHOR]

[Display omitted] • EG was used as the activator to regulate the DA2MP/PrOH solution for CO 2 capture. • The regulation mechanism was clarified by theoretical and experimental analysis. • Carbamate was promoted to form alkyl carbonate by EG, resulting a decreasing viscosity. • The regeneration heat duty of DA2MP/PrOH/EG was estimated as 1.58 GJ·ton−1 CO 2. The non-aqueous amine solvents for CO 2 capture gaine an advantage in energy-saving potential, but with a sharp increase viscosity after saturated absorption would easily cause problems such as equipment scaling and pipe blockage. In the present work, th e ethylene glycol (EG) was used as co-solvent and activator to regulate the non-aqueous absorbent of 1,5-diamino-2-methyl-pentane (DA2MP) and n-propanol (PrOH) for CO 2 capture. The absorption loading of the mixture solution was 1.13 mol·mol−1 when the mass concentration of DA2MP was 25 wt% and the volume ratio of PrOH to EG was 8:2. By activated by EG, the viscosity of the saturated solution was only 9.05 mPa·s, which changed from viscous precipitation to clarify liquid compared with that of DA2MP/PrOH. The absorbent maintained 90.30% of its initial CO 2 absorption loading after 10th cycle regeneration under 393.15 K for 60 min. According to the quantum chemical calculations and experimental results, the reaction and regulation mechanism of CO 2 capture into DA2MP/PrOH/EG was clarified. In DA2MP-PrOH solution, CO 2 firstly reacted with DA2MP to form carbamate, and them the product further reacted with PrOH to form alkyl carbonates, which was viscous and insoluble due to the high intermolecular force between the CO 2 products. After adding appropriate amount of EG, the solubility of insoluble products in solvent was increased through weakening the intermolecular interaction of products and enhancing the intermolecular interaction between products and solvents, which further converted them into soluble alkyl carbonate and realized viscosity reduction. The regeneration heat duty of DA2MP/PrOH/EG solution was estimated as 1.58 GJ·ton−1 CO 2 , which was 29.5% and 58.42% less than that of DA2MP/PrOH and bench mark MEA solution, respectively, indicating a alternative candidate for CO 2 capture. [ABSTRACT FROM AUTHOR]

[Display omitted] • A functional ionic liquid with self-extraction property was proposed for CO 2 capture. • [DBAPAH][Im]-H 2 O could be regenerated at low temperature (98 °C). • Interaction between anion and cation reduced activation energy barrier of carbamate. • Self-extraction promoted the rapid separation of FILs from the main solution. Regarding the bottleneck of high regeneration consumption for the amine absorbents, it was innovatively proposed in this work to construct a novel functional ionic liquid absorbent (3-Dibutylamino-propylamine-imidazole, [DBAPAH][Im]) with the self-extraction property for CO 2 capture. The solvent changed from liquid-liquid two-phase to homogeneous as absorption loading increased, and it returned to a two-phase after desorption. The absorption loading of [DBAPAH][Im]-H 2 O solution for CO 2 capture was 1.49 mol mol−1, and its regeneration efficiency was found to be 92.09% for the first regeneration and remained at 81.34% even after six cycles with a low regeneration temperature of 98 °C. It was found that this ionic liquid featured a reversible polarity, for which the polarity of [DBAPAH][Im] was much lower than that of water before absorption. The solvent changed from liquid-liquid phase to homogeneous as absorption loading increased because the polarity of the carbamate product and the Van der Waals interaction between carbamate and water were all increased. After desorption, the ionic liquid resumed with the low polarity and was not miscible in water to form an organic extraction phase, which promoted the rapid separation of the ionic liquid from the main solution and finally achieved the purpose of low temperature regeneration. Due to the coordination between cations and ions, the desorption free energy of the products formed by [DBAPAH][Im] and CO 2 was very low (7.56 kJ mol−1). Furthermore, the energy consumption was estimated as 1.83 GJ t−1 CO 2 , which was much lower than that of benchmark monoethanolamine (MEA; 3.8 GJ t−1 CO 2), and finally achieve the purpose of low regeneration temperature and low energy consumption regeneration. [ABSTRACT FROM AUTHOR]

[Display omitted] • Synthesis of a novel Ionic Liquid with reversible polarity. • ILs regulates phase transition in binary water solid-liquid biphasic absorbent. • Polarity, solubility parameter and hydrogen bonding lead to solid-liquid phase separation. • High lattice energy determines that the products are solid powders. • [IPDAH][Im]–H 2 O solution has low regenerative energy consumption. Ionic liquids (ILs) solid-liquid biphasic solvents for CO 2 capture have the advantages of high CO 2 loading and low energy consumption, and their phase change behavior was regulated via phase separation agents. However, phase separator agents exhibit bottlenecks in terms of volatility loss and high-rich phase viscosity. A novel "reversible polarity" functionalized ionic liquids (isophorone diamine-imidazole, [IPDAH][Im]) was innovatively proposed in this work, which featured solid-liquid phase change behavior upon CO 2 absorption in water in the absence of a phase separation agent. After saturated absorption, CO 2 products were enriched into the lower phase and precipitated as a white crystalline powder with 91 % of the total CO 2 loading (1.15 mol mol−1) but only 60 % of the total volume. Products after thermal desorption (393.15 K), maintaining 80 % of its initial loading after the sixth regeneration cycle. Based on the results of experimental characterization and theoretical calculation, [IPDAH][Im] possessed reversible polarity, and its initial polarity was consistent with that of water. After absorption, [IPDAH][Im] interacted with CO 2 to form products whose polarity diminishes, resulting in the associated phase transition; after desorption, the high polarity is restored. The products existed as ion pairs (ILsCOO−-ILsH+), as evidenced by strong van der Waals interaction, and electrostatic attraction. Strong hydrogen bonding forces between the products and the Hansen solubility parameter, as well as the high lattice energy, led to the self-agglomeration formation of the products in water, resulting in the development of a solid powder product. The heat duty of [IPDAH][Im]–H 2 O was 1.23 GJ ton−1 CO 2 , which was approximately 67 % less than that of monoethanolamine (MEA; 3.77 GJ ton−1 CO 2), signifying a major potential for application in CO 2 capture. [ABSTRACT FROM AUTHOR]

[Display omitted] • Solid-liquid 'phase controllable' biphasic amine was firstly proposed for CO 2 capture. • The reaction rule of multistage amines was studied. • The activation barrier to form AMP+CO 2 -was higher than that of TETA+CO 2 –. • TETA+CO 2 – had two deprotonation pathways: self-deprotonation and AMP deprotonation. • The controllability was ascribed to the interaction of TETA intermediates was weak. The main issues in the application of biphasic amine absorbent include the inconvenient separation of the liquid–liquid biphase and the clogging that is associated with the solid–liquid mixture. A novel solid–liquid 'phase controllable' biphasic amine absorbent was therefore developed, in which the phase separation occurred only when the absorbent was near saturation. The absorbent, composed of triethylene tetramine (TETA), 2-amino-2-methyl-1-propanol (AMP), and N-methylformamide (NMF), turned into solid–liquid biphase under CO 2 loading of 0.85 mol mol−1, which is close to saturation (0.92 mol mol−1). The solid phase comprised white powder that accounted for only 42 % of the total volume while absorbing 91 % of the total load. Turbidity and particle size tests showed that the phase separation was self-aggregating. The mechanisms of absorption and regulation were obtained using 13C NMR and molecular simulation. During the absorption, CO 2 first combined with TETA to generate TETAH+CO 2 –/TETACO 2 – through the zwitterion mechanism, and then combined with AMP to generate AMPCO 2 – because of the lower reaction activity between CO 2 and AMP. The TETA-carbamate was found to greatly weakened the strength of the hydrogen bonds and the van der Waals forces between AMPH+ and AMPCO 2 –, increasing the solubility of the intermediate products, and therefore achieved the purpose of controlling the phases separation inherent in the reaction. [ABSTRACT FROM AUTHOR]