CO2 Absorption Capacity Research Articles

An amine-functionalized strategy to enhance the CO2 absorption of type III porous liquids

Porous liquids (PLs) is a new material with two seemingly unrelated characteristics: porosity and liquidity. In this study, an amine functionalized strategy was proposed to enhance the CO2 absorption of Type III Porous Liquids. 2-Methylimidazole zinc salt (ZIF-8) modified by tetraethylenepentamine (TEPA) was chosen for providing porosities and the 1-Ethyl-3-methylimidazolium Bis(trifluoro-methanesulfonyl)-imide ([EMlm][NTf2]) was chosen as sterically hindered solvent, an amine-functionalized type Ⅲ porous liquids were reported. First, amine groups were successfully loaded on the ZIF-8. Then, the effect of amine loading on ZIF-8 was investigated. It was found the 30 TEPA@ZIF-8 nanoparticles were the optimum candidates based on CO2 absorption capacity and micropore analysis. Subsequently, the CO2 absorption capacity of absorbent was studied. 5-30TEPA@ZIF-8/[EMlm][NTf2] had a CO2 absorption capacity of 0.124 mmol g−1, which was 4.43 times higher than 5-0TEPA@ZIF-8/[EMlm][NTf2]. And the corresponding absorption rate increased by 745%. Three kinetics models were used for describing the absorption process, and the result showed the fractional-order kinetic model was the most accurate. Finally, the absorbent had a low heat absorption with a value of −1.38 kJ/mol. The CO2 absorption capacity lost just 4.3% after five cycles. All the results indicate the prepared porous liquids had an application potential in CO2 capture.

Enhancing the CO2, CH4, and N2 adsorption and kinetic performance on FAU zeolites for CO2 capture from flue gas by metal incorporation technique

Various metals including alkali (Na+, K+), alkaline earth (Mg2+ and Ca2+), and transition metals (Cu2+ and Fe3+) were successfully incorporated into the structure of faujasite zeolites (X and Y) by novel post-synthesis modification method. The effect of metal-doping on the CO2, CH4, and N2 adsorption and kinetic performance in the context of flue gas carbon capture and natural gas purification was examined by four approaches; (i) the impact on structural properties was examined by XRD, FTIR, UV–visible, H2-TPR, FESEM, EDX Dot-Mapping, and BET analysis; (ii) the influence on the CO2, CH4, and N2 adsorption capacity was acquired by volumetric method up to 100 kPa at 25 °C (iii) the effect on binary CO2/CH4 and CO2/N2 selectivity was determined by the Henry constant and IAST selectivity; (iv) the micropore - macropore kinetic model was utilized to study the influence on diffusion coefficients. The dual-site Langmuir-Freundlich (DSLF) isotherm was found to be the best adaptability to the experimental isotherms data. The results showed an extraordinary increase in CO2 absorption capacity to 4.9 and 7 for KX and KY, respectively. Faujasite zeolite with a lower Si/Al ratio (zeolite X) outperforms CO2/CH4 and CO2/N2 separation performance than higher ones (zeolite Y). Among all samples, KX showed the highest CO2/CH4 and CO2/N2 IAST selectivity with values of 61 and 152 at 100 kPa, respectively, in addition to the highest diffusion coefficients for CH4 and N2. The incorporated potassium metal into the faujasite zeolites showed promising sorbents for the separation of CO2 from flue gas and natural gas streams.

Sacred groves: a model of Zagros forests for carbon sequestration and climate change mitigation

SummaryForests are the most important carbon pools among terrestrial ecosystems, and ensuring less disturbance of sacred groves might constitute a form of forest management for carbon sequestration and climate change reduction. The carbon contents in Zagros oak sacred groves and silvopastoral lands were compared to determine the carbon sequestration potential of these forests. Using a nested sampling design, we measured total carbon content (tC ha–1; aboveground tree biomass, aboveground sapling biomass, belowground biomass, soil organic carbon, leaf litter, herbs and grasses and dead wood and fallen stumps) in both forest groves and silvopastoral lands. The mean total biomass and mean total carbon content varied between sacred groves (453.8 t ha–1 and 338.79 tC ha–1, respectively) and silvopastoral lands (89.4 t ha–1 and 113.46 tC ha–1, respectively). Mean soil organic carbon was significantly lower (71.44 tC ha–1) in silvopastoral lands than in sacred groves (125.49 tC ha–1). The mean total sequestered carbon dioxide (CO2) was 1243.36 tCO2 ha–1 in the sacred groves and 416.40 tCO2 ha–1 in silvopastoral lands. We conclude that human activities have reduced the CO2 absorption capacity of the forests. The substantial disparities between the landscapes emphasize the need to restore damaged forests, and sacred groves might be a useful model for increasing carbon storage in these forests.

Revolutionizing CO2 capture: Molecular complexes of deep eutectic solvents with enhanced hydrogen bond accepting interaction for superior absorption performance

In this study, functionalized deep eutectic solvents (DESs) were synthesized to enhance the CO2 absorption characteristics, such as absorption capacity and reaction rate, compared to conventional alkanolamine-based absorbents. DES consists of a hydrogen bond donor (HBD) and hydrogen bond acceptor (HBA) and has the advantages of facile synthesis without complex molecular design as well as low vapor pressure and low synthesis cost. It is a liquid material formed by large networks of molecular architectures via static interactions, including hydrogen bonds. Hence, it is possible to capture CO2 physically via intermolecular vacancies, and chemical absorption is possible via functionalization by introducing suitable HBAs and HBDs that have functional groups that are reactive toward CO2. Herein, two amino acids, glycine (GLY) and proline (PRO), were used to prepare HBAs by converting them into amino acid salts. Upon conversion, the proton attached to the carboxyl group is detached and the potassium cation supports the loss of an electron charge. Hence intermolecular interactions are enhanced, and they are available for DES formation.Alkanolamines, such as monoethanolamine (MEA), diethanolamine (DEA), and Nmethyldiethanolamine (MDEA), were used as HBDs with these HBAs to functionalize DESs for enhancing the CO2 absorption capacity. Using FT-IR, DSC, and 13C NMR the characteristics of CO2 absorption by the new DESs were determined and compared with those of conventional absorbents. The relationship of equilibrium capacity and reaction rate with the order of amines and molecular free volume was evaluated to ascertain the effects of HBA and HBD on the absorption characteristics.

Evaluation of novel aqueous piperazine-based physical-chemical solutions as biphasic solvents for CO2 capture: Initial absorption rate, equilibrium solubility, phase separation and desorption rate

Novel aqueous piperazine-based physical–chemical solutions were proposed as promising liquid–liquid biphasic solvents for energy-efficient CO2 capture in order to enhance the absorption and desorption performance. Various phase-change systems including Piperazine (PZ), 1-(2-aminoethyl) piperazine (AEP), methyldiethanolamine (MDEA), sulfolane, 1-propanol and water with different concentration ratios were investigated comprehensively in terms of initial absorption rate, equilibrium solubility, phase splitting and desorption rate in the present work. Experimental results indicated that with the aid of organic solvents, PZ and AEP were proved to be promising candidates to accelerate the initial absorption and desorption rates, as well as enhance the CO2 absorption capacity due to their excellent reaction kinetics. The tunable phase separation property could be achieved by varying the concentration ratios of amine/organic solvent. After achieving equilibrium, the two liquid–liquid phases would not return back to one homogeneous liquid phase. Among these biphasic solvents, aqueous 2.5 M PZ + 2.5 M sulfolane with a large CO2 loading 0.85 mol CO2/mol amine at the phase change point was the optimal choice owing to good phase separation and great absorption and desorption properties. Compared to aqueous 2.5 M PZ single solvent, it demonstrated a 16% higher initial absorption rate, 9% larger CO2 absorption capacity and double desorption rate. This research provided a potential alternative absorbent for CO2 capture.

Room-Temperature Absorption of Carbon Dioxide on an Improved Soda Lime-Based Absorber

Soda lime beads are generally used for carbon dioxide (CO2) capturing at room temperature due to their higher absorption capacity compared to other absorbers. For this, the soda lime is synthesized using alumina as the doping material, which acts as a hardener to provide strength to the beads. The crushing load strength of the beads is an important parameter of the CO2 absorber material for the ease of handling and to prevent dust formation. In the present work, an improved soda lime-based absorbent has been developed by the addition of silicon dioxide in the raw material to produce calcium silicate, which provides more crushing load strength to the improved soda lime beads. The effect of the addition of silicon dioxide in the raw material on the soda lime bead crushing strength and CO2 absorption capacity was studied. It was found that the crushing load strength of the beads as well as the CO2 adsorption capacity of the beads increased with increase in the addition of silicon dioxide. From a dynamic performance study, it was found that the CO2 absorption capacity of a soda lime-based pebble bed increased with increase in the flowrate of CO2 containing air due to the decrease in channeling formation of gas, which occurs at lower flowrates.

A Novel Carbon Dioxide Desorption Phenomena using Potassium Acetate Aqueous Solution

A novel CO2 absorbent, 50–75 wt.% aqueous potassium acetate solution (AcK(aq)), which showed a CO2 absorption capacity of ~ 0.2 mol CO2/mol, and could almost immediately completely desorb CO2 on addition of 40 wt.% H2O at 30 ℃ was investigated. This novel phenomenon seemed contrary to the Le Chatelier's principle because H2O is reactant in this system. After characteristics of products by FTIR and XRD diffraction pattern, the novel desorption behavior was attributed to the acid-base reaction between KH(CH3COO)2 and KHCO3 precipitates within the absorbent sludge. As H2O was added, both compounds re-dissolved and CO2 was released. A similar observation was made when the absorbent sludge was heated to temperatures above 60 ℃, owing to an increase in solubility with temperature. The mechanism of CO2 captured and released by AcK(aq) was proposed in this study. This novel energy-saving CO2 absorption and desorption behavior reveals that AcK(aq) has a high potential for application in the commercial production process.

Functionalized cross-linking mechanism of biochar “adsorption-reaction microunit” on the promotion of new ammonia-based CO2 capture

Ammonia-based CO2 capture technology has crucial impacts on power plants carbon emission reduction, which has become one of the most concerning issues. However, there are limitations faced by traditional capture technology in the absorption rate, ammonia escape and regeneration energy consumption. The functionalized biochar (with a specific surface area of up to 2835.36 m2/g, micropores volume of 77.4 %) was used to enhance the mass transfer process of new ammonia-based (ammonia-ethanol mixed absorbent) CO2 capture by the bubbling absorption experiment system, combined with Monte Carlo simulations, which explored the adsorption and release characteristics of CO2/NH3 molecules in biochar with different pore sizes. The results show that the CO2 absorption flux added biochar RH-900 is 59.67 L·min, increased by 16.16 % compared with pure absorbent. And the volume mass transfer coefficient is 1.226 × 10-4mol/m2·s·Pa, increased by 15.3 % compared with the SiO2. The addition of RH-900 also promotes the CO2 load capacity of the carbonated solution up to 0.5255 mol/L, enhancing the CO2 absorption capacity and CO2 capture efficiency significantly. The ultra-micropores adsorb CO2, while the surface of larger pores distributes and achieves the adequate fixation of NH3. Besides, the mesopores and macropores provide space where the CO2 is transported and diffused, and the free ammonia concentration is maintained. The study provides an innovative thought for improving the ammonia-based CO2 capture method and significantly reducing of harmful carbon emissions by biomass energy-carbon capture and storage (BECCS) technology.

COSMO-RS Exploration of Highly CO2-Selective Hydrogen-Bonded Binary Liquid Absorbents under Humid Conditions: Role of Trace Ionic Species.

It is critical to improve carbon capture efficiency while reducing costs to popularize carbon capture and storage. Considering the green chemistry and engineering objectives, this study theoretically explores the CO2 absorption capacity of 1,533,528 hydrogen-bonded mixtures, i.e., deep eutectic solvents in a broad sense. Exhaustive statistical thermodynamic calculations well explain the experimental reports; it is confirmed that deep eutectic solvents containing ionic compounds have higher CO2 selective absorption capacity than those composed of non-ionic species. Quantitative evaluation of hydrogen-bonding interaction also predicts that the capacity is higher when the ionic compounds work as hydrogen-bonding donors. This is because the trace ionic species weaken the hydrogen-bonding network in the mixtures to improve CO2 physisorption.

Fine-tuning the Basicity of Deep Eutectic Solvents by Substituting Guanidine for Urea in Reline.

The physicochemical properties of deep eutectic solvents (DESs) depend on the combination of hydrogen bond acceptors and hydrogen bond donors used. The basicity of a DES significantly influences its performance in CO2 chemical absorption, biomass and protein dissolution, and catalytic reactions. To the best of our knowledge, a strategy for fine-tuning the basicity of DESs has not yet been reported. Therefore, in this study, we substituted the base urea (Ur) in reline, which is a 1:2 mixture of choline chloride (ChCl) and Ur, with the superbase guanidine (Gu) to fine-tune its basicity. Binary (2Gu-ChCl) and ternary (Gu-Ur-ChCl) DESs were prepared, and their CO2 absorption capacities were investigated at 313.2 K. The equimolar mixture Gu-Ur-ChCl absorbed CO2 gas up to the molar ratio [CO2]/[ChCl] ≈ 1.0. Therefore, the basicity of ChCl-based DES can be continuously varied by substituting more molecules of Ur with Gu. Our strategy of combining functional and non-functional molecules with similar structures to vary the basicity of DESs has potentially wide applications that utilize DESs in the future.

Comparative Study for the Absorption of Carbon Dioxide in Aqueous Amine Solvents for Enhanced Loading

Aims: The current study aimed to investigate the CO2 absorption capacity of the aqueous alkanolamine, including primary, secondary, tertiary, and sterically hindered amines and polyamines, i.e., monoethanolamine (MEA), diethanolamine (DEA), triethanolamine (TEA) and 2- amino-2-methyl-1-propanol (AMP), tetraethylenepentamine (TEPA), triethylenetetramine (TETA), 3- (Methylamino)propylamine (MAPA), and diethylenetriamine (DETA) at 40, 60, and 80°C at 1.1 bar. Methods: An increase in reaction temperature caused a decrement in CO2 loading across the board for all solvents. The trend of CO2 loading was TEA < MEA < DEA < AMP < MAPA < DETA < TETA < TEPA at 40 ºC, TEA < DEA < MEA < AMP < MAPA < DETA < TETA < TEPA, at 60ºC and TEA < DEA < AMP < MEA < MAPA < DETA < TETA < TEPA at 80ºC. Results: The results indicated that TEPA has great potential to be utilized as an energy-efficient and non-corrosive solvent for CO2 capture since it has outperformed all other aqueous amine solvents in this present study. Furthermore, the CO2 loading of sterically hindered amine (AMP) at the same temperature was found to be higher than primary, secondary, and tertiary amines. Heat of absorption (Δ Η abs) was also determined to gauge the energy requirement to regenerate absorbents for cyclic loading from an economic viewpoint. Conclusion: DETA has the highest Δ Η abs = 84.48 kJ/mol. On the contrary, the long-chain tertiary amine TEA resulted in the least Δ Η abs = 40.21 kJ/mol, among all other solvents. Whereas the sterically hindered amine (AMP) was observed to possess mid-range Δ Η abs, i.e., 58.76 kJ/mol. Among all selected solvents, polyamines showed higher Δ Η abs than other conventional amines pertaining to the precedence of TEA<AMP<DEA< MEA<TETA<TEPA<MAPA<DETA.

Dual-functionalized ionic liquid biphasic solvents with aqueous-lean for industrial carbon capture: Energy-saving and high efficiency

A novel, sustainable, dual-functionalized amino ionic liquid biphasic solvent of 3-(Dimethylamino)-1-propylamine-1,2,4-triazole/poly (ethylene glycol) dimethyl ether/water ([DMAPA][TZ]/NHD/water) was proposed for CO2 capture to reduce the consumption of regeneration energy. Experimental results showed that the CO2 absorption loading of the solvent was 1.95 mol CO2·L−1 solvent at a CO2 partial pressure of 15 kPa. The volume of the CO2-rich phase was 40 vol% of the total volume, with a loading of up to 4.65 mol CO2·L−1 solvent, accounting for approximately 95.4% of the blended CO2 loading in the solvent. The CO2-rich phase could be regenerated by 92.3% in 10 min at 373 K, without the presence of a lean phase. The regeneration efficiency of the solvent was maintained at 83% after 10 adsorption and desorption cycles. The reaction, regeneration, and phase-change mechanism were investigated using 13C NMR and phase composition analysis. CO2 reacted with [DMAPA][TZ] to form two kinds of carbamate during solubilization, and all carbamates could be further hydrolyzed to form HCO3− and CO32−. The solvent effect, phase-change behavior, and CO2 physical dissolution of NHD could promote the absorption and desorption rate and absorption capacity of CO2. The energy consumption for CO2 desorption could be reduced to 1.335 GJ·t−1 CO2, which was 67% lower than that of 30 wt% ethanolamine (3.99 GJ·t−1 CO2), given the lower heat of reaction, specific heat capacity, and solvent loss. Thus, this solvent presents a sustainable strategy for advancing carbon capture technologies.

Encapsulated deep eutectic solvent and carbonic anhydrase jointly by microfluidics for high capture performance of carbon dioxide

Excessive carbon dioxide (CO2) emissions from fossil fuel combustion have a profound impact on environment, leading to different associated climate disasters. Although deep eutectic solvents (DES) have the advantage of high absorption capacity of CO2, their high viscosities sharply decrease absorption performance due to the low absorption rates. Herein, one of DES choline chloride / urea (CU) and carbonic anhydrase (CA) was encapsulated jointly by microfluidics and crosslinked thermally (microcapsule@(CU + CA)), which was designed for high capture performance of CO2. The absorption abilities of microcapsules have been significantly improved by the increase of specific surface area, in which the absorption capacity and absorption rate of microcapsule@(CU + CA) were 74 times and 253 times higher than that of neat CU. In addition, the selectivity of CO2/CH4 also increased 62 times via encapsulation. The high cyclic performance of microcapsule@(CU + CA) was achieved for its high absorption performance and high ability to desorb CO2 from microcapsule. DES and CA encapsulated jointly by microfluidics can realize high absorption capacity, high absorption rate and high absorption selectivity simultaneously, and it also provides a potential pathway for the efficient capture of various gases.

2D/2D Carbon Nitride/Zn-Doped Bismuth Vanadium Oxide S-Scheme Heterojunction for Enhancing Photocatalytic CO2 Reduction into Methanol

Developing superior photocatalytic CO2 conversion systems for the generation of high-valued fuels or chemicals is highly desirable but is still challenging work. Herein, the well-organized carbon nitride/Zn-doped bismuth vanadium oxide (CN-ZnBVO) nanohybrids were constructed by a facile CTAB-assisted solvothermal strategy to achieve an efficient photocatalytic reduction of CO2 to CH3OH under UV–vis light. Impressively, the distinctive butterfly-like 2D/2D CN-ZnBVO catalyst showed markedly enhanced photocatalytic performance in alkaline medium, with the largest CH3OH generation rate of 609.1 μmol g–1 h–1 and a high selectivity of 90.5%, outperforming most recently reported CO2 photoreduction systems. Moreover, the yield of CH3OH remained nearly constant over three successive repeated cycles, signifying its good stability. Detailed characterization and theoretical calculations revealed that the outstanding photocatalytic activity owes much to the more accessible reaction sites and improved CO2 absorption capacity induced by the distinctive micromorphology effect, as well as the localized charge density distribution and fast spatial charge separation and transfer caused by the 2D/2D S-scheme heterojunction, thus providing more photogenerated electrons for efficient CH3OH formation. The present work offers a new perspective for the in situ construction of highly active S-scheme heterostructures for selective photocatalytic CO2 reduction.

Experimental and Computational Evaluation of 1,2,4-Triazolium-Based Ionic Liquids for Carbon Dioxide Capture

Utilization of ionic liquids (ILs) for carbon dioxide (CO2) capture is continuously growing, and further understanding of the factors that influence its solubility (notably for new ILs) is crucial. Herein, CO2 absorption of two 1,2,4-triazolium-based ILs was compared with imidazolium-based Ils of different anions, namely bis(trifluoromethylsulfonyl)imide, tetrafluoroborate, and glycinate. The CO2 absorption capacity was determined using an isochoric saturation method and compared with predicted solubility employing COnductor-like Screening Model for Real Solvents (COSMO-RS). To gain an understanding of the effects of cations and anions of the ILs on the CO2 solubility, the molecular orbitals energy levels were calculated using TURBOMOLE. Triazolium-based ILs exhibit higher absorption capacity when compared to imidazolium-based ILs for the same anions. The results also showed that the anions’ energy levels are more determinant towards solubility than the cations’ energy levels, which can be explained by the higher tendency of CO2 to accept electrons than to donate them.

Thermodynamic model for CO2 absorption in imidazolium-based ionic liquids using cubic plus association equation of state

In order to achieve efficient capture of carbon dioxide (CO2) by ionic liquids (ILs), IL with good performance of high CO2 absorption capacity and low energy consumption need to be explored. Density, heat capacity, CO2 solubility and absorption enthalpy are key properties for the performance evaluation of IL solvents. In this work, the cubic plus association equation of state (CPA EoS) was applied for the integrated modelling of above properties in CO2 physical and chemical absorption by 22 imidazolium-based ILs. The results show that the density, heat capacity of pure ILs and CO2 solubility in a broad range of temperature (281–403 K) and pressure (0.1–23 MPa) were accurately calculated with deviations less than 1.27%, 0.54% and 3.73%, respectively. CO2 chemisorption was satisfactorily described by CPA EoS with an error of 0.12% considering interactions for the reactive sites between CO2 and amino groups in IL. Furthermore, the prediction capabilities of CPA EoS were verified with results showing good quantitative agreement with density and solubility data in literature. The effects of structures of ILs studied in this work on the CO2 solubility and absorption enthalpy were analyzed. [NH2emim][BF4], [Omim][Tf2N] and [Emim][eFAP] were found to have better performance of CO2 absorption. This model provides a feasible approach to determine synthetically the key properties of CO2-IL systems for the selection of proper ILs, design and simulation of the CO2 capture process.

Spatiotemporal distributions of air-sea CO2 flux modulated by windseas in the Southern Indian Ocean

The Southern Indian Ocean is a major reservoir for rapid carbon exchange with the atmosphere, plays a key role in the world’s carbon cycle. To understand the importance of anthropogenic CO2 uptake in the Southern Indian Ocean, a variety of methods have been used to quantify the magnitude of the CO2 flux between air and sea. The basic approach is based on the bulk formula—the air-sea CO2 flux is commonly calculated by the difference in the CO2 partial pressure between the ocean and the atmosphere, the gas transfer velocity, the surface wind speed, and the CO2 solubility in seawater. However, relying solely on wind speed to measure the gas transfer velocity at the sea surface increases the uncertainty of CO2 flux estimation. Recent studies have shown that the generation and breaking of ocean waves also significantly affect the gas transfer process at the air-sea interface. In this study, we highlight the impact of windseas on the process of air-sea CO2 exchange and address its important role in CO2 uptake in the Southern Indian Ocean. We run the WAVEWATCH III model to simulate surface waves in this region over the period from January 1st 2002 to December 31st 2021. Then, we use the spectral partitioning method to isolate windseas and swells from total wave fields. Finally, we calculate the CO2 flux based on the new semiempirical equation for gas transfer velocity considering only windseas. We found that after considering windseas’ impact, the seasonal mean zonal flux (mmol/m2·d) increased approximately 10%-20% compared with that calculated solely on wind speed in all seasons. Evolution of air-sea net carbon flux (PgC) increased around 5.87%-32.12% in the latest 5 years with the most significant seasonal improvement appeared in summer. Long-term trend analysis also indicated that the CO2 absorption capacity of the whole Southern Indian Ocean gradually increased during the past 20 years. These findings extend the understanding of the roles of the Southern Indian Ocean in the global carbon cycle and are useful for making management policies associated with marine environmental protection and global climatic change mitigation.

A novel approach based on detailed structural and molar free volume analyses to characteristics of deep eutectic solvents specialized for CO2 absorption

This study presents a novel approach based on structural and molar free volume analyses to characterize deep eutectic solvents (DESs) with functional groups possessing CO2 affinity based on analytical prediction and data. Although DESs have garnered attention due to their high tunability and applicability in various fields, there is paucity of literature containing their detailed analyses. In this investigation, HBDs with amino (–NH2), carbonyl (CO), and ether (R-O-R') groups were chosen to determine the effect of functional groups on the CO2 absorption capacity and structural properties of DESs. Based on FT-IR and 1D/2D NMR measurements on DESs, it was confirmed that the hydrogen used for the formation of hydrogen bonds exhibited a distinct property and that DESs were successfully formed. In addition, the DES including tetraethylammonium bromide, 3-amino-1-propanol, and water with an amino group exhibited a high capacity for chemical CO2 absorption. In the case of the DES, structural configuration prediction was proposed using the chemical CO2 absorption capacity. The proportional relationship between the physical CO2 absorption and molar free volume of DESs was also confirmed using analytical data. Finally, these novel approaches to DESs can be used as a guide for applying and developing new DESs with structural properties.

Mesoporous MgO enriched in Lewis base sites as effective catalysts for efficient CO2 capture

Capturing CO2 has become increasingly important. However, wide industrial applications of conventional CO2 capture technologies are limited by their slow CO2 sorption and desorption kinetics. Accordingly, this research is designed to overcome the challenge by synthesizing mesoporous MgO nanoparticles (MgO-NPs) with a new method that uses PEG 1500 as a soft template. MgO surface structure is nonstoichiometric due to its distinctive shape; the abundant Lewis base sites provided by oxygen vacancies promote CO2 capture. Adding 2 wt % MgO-NPs to 20 wt % monoethanolamine (MEA) can increase the breakthrough time (the time with 90% CO2 capturing efficiency) by ∼3000% and can increase the CO2 absorption capacity within the breakthrough time by ∼3660%. The data suggest that MgO-NPs can accelerate the rate and increase CO2 desorption capacity by up to ∼8740% and ∼2290% at 90 °C, respectively. Also, the excellent stability of the system within 50 cycles is verified. These findings demonstrate a new strategy to innovate MEA absorbents currently widely used in commercial post-combustion CO2 capture plants.

Study on CO2 absorption by novel choline chloride-diethylenetriamine-water deep eutectic solvents in a rotor-stator reactor

Excessive CO2 emissions from flue gas lead to the greenhouse effect and catastrophic climate change and have become a global concern. To address this problem, novel choline chloride-diethylenetriamine-water (ChCl-DETA-H2O) deep eutectic solvents (DESs) with high CO2 absorption capacity was synthesized in this study. It was found that the DES with a composition of 1ChCl-5DETA-2H2O had the highest CO2 absorption capacity, which was up to 0.250 gCO2/gDES. The as-synthesized DESs were adopted for CO2 absorption in a rotor-stator reactor (RSR), and the effects of ChCl-DETA-H2O molar ratio, high gravity factor, liquid flow rate, gas flow rate, temperature, and inlet CO2 concentration on the CO2 absorption efficiency, overall gas-phase volumetric mass-transfer coefficient (KGa) and height of a transfer unit in the RSR were investigated. Analyses on the mechanism of CO2 absorption in the DES suggest that carbamate formed after CO2 absorption by 1ChCl-5DETA-2H2O. A comparison with the traditional packed columns indicates that the KGa in the 1ChCl-5DETA-2H2O/RSR process was about one order of magnitude larger than that in the DETA/packed column process. Also, the 1ChCl-5DETA-2H2O/RSR process achieved a higher CO2 absorption efficiency and KGa than the DETA/rotating packed bed process. This work demonstrates that the RSR enhanced the absorption of CO2 by the DES and the combination of RSR and DES can provide an efficient process for CO2 capture.