CO2 Absorption Research Articles

INVESTIGATION OF CARBON DIOXIDE ABSORPTION CAPACITY AND DISSOLUTION RATE WITH AMINO ACID SALT SOLUTIONS: SODIUM AND POTASSIUM GLYCINATE

Global warming is a major world problem and causes climate change. The primary cause of global warming is carbon dioxide (CO2) emissions. Ongoing studies are being conducted to mitigate the effects of this problem. Anthropogenic CO2 emissions occur by burning fossil fuels to generate power and heat. To combat this problem, CO2 must be captured from point emission sources or directly from air. The conventional method to remove CO2 at the point emission sources is post-combustion systems. In these systems, absorption process is generally used to diminish CO2 emission and capturing at the source. Current researches aim to find an efficient and alternative solution to absorption. In this work, sodium glycinate (NaGly) and potassium glycinate (KGly), which are amino acid salt solutions, were investigated for CO2 absorption. Amino acid salt solutions have shown similar absorption kinetics and capacities to amine-based solutions due to same functional group. These solutions are usually more stable to oxidative degradation and have low volatilities, higher surface tensions and the viscosities are very close to waters. Experiments were performed using a stirred cell system at ambient temperature (20°C) and atmospheric pressure (91 kPa), in Ankara, Türkiye. In experiments, sodium glycinate and potassium glycinate concentration was ranged between 0.1 and 1.5 M. The experiments were also repeated with sodium hydroxide and potassium hydroxide in the same concentration range for comparison. In addition, the amino acid salt solutions examined in this study were compared with alkaline solutions and glycine in terms of total CO2 absorption capacity and CO2 dissolution rate. As a result of the experiments, the potassium glycinate solutions gave approximately 1.4 times better results than the sodium glycinate solutions at the highest concentration. Also, functional groups were determined by FTIR analysis of pure and CO2-loaded potassium glycinate solution.

Graph transformer based transfer learning for aqueous pKa prediction of organic small molecules

The acid-base dissociation constant (pKa) is an essential physicochemical parameter that indicates the extent of proton dissociation. However, accurately predicting pKa values is still challenging due to limited data availability for organic small molecules in aqueous solutions. In this work, we propose an open-source pKa prediction tool based on Graph Transformer, which combines the graph neural network and transformer to take both local and global information into account. To address the limitation of data scarcity, the experimental dataset is expanded, while transfer learning is employed by pre-training on the ChEMBL (computational) dataset and fine-tuning on the experimental dataset. The performance and generalization of the obtained models are comprehensively evaluated on both internal and external test sets. Additionally, two exemplary applications, namely the screening of tertiary amines for CO2 absorption and acidic ionic liquids for reactive extraction, are investigated to validate the reliability of our tool. The results show that our model can effectively guide the identification of promising candidates for the target applications by achieving accurate pKa predictions.

Metal-organic frameworks (MOFs) for photoreduction of CO2

In recent decades, human industrialisation has become increasingly advanced, and the quality of life has also improved. Subsequently, the excessive consumption of fossil fuels has caused a series of problems, for example, global environmental warming caused by excessive CO2 emissions. Among numerous CO2 reduction technologies, using solar energy as an energy source for the CO2 photoreduction is considered one of the most prospective technologies. This method not only reduces the amount of CO2, but also enables to converse CO2 into other valuable chemicals, thereby achieving carbon cycling. Metal-organic frameworks (MOFs) are composed of metal ions and organic ligands as three-dimensional porous materials. MOFs have many advantages, including sizeable specific surface area, excellent CO2 absorption capacity and modifiable pore structure, leading to broad application potential in photocatalytic reduction of CO2. This article mainly introduces three aspects: functionalisation and modification of pure MOFs, MOF-based composite materials, and MOF-derived materials, which further improve the CO2 photocatalytic efficiency of MOFs. Furthermore, it includes the analysis of reported examples, discussion and outlook on reaction mechanisms and challenges. At present, the main difficulties faced by MOFs-based photocatalysts lie in their economic feasibility and poor material stability. Therefore, this review aims to help stimulate in-depth research in this area as well as better exert the advantages of MOFs.

Investigation of CO2 capture performance of polyamine/organic alcohol ether non-aqueous absorbent regulated by ethylene glycol

The use of non-aqueous absorbents has great potential in reducing energy consumption during CO2 capture. However, current obstacles include the formation of precipitation or gelatinous substances after CO2 absorption, which significantly hinder their further application. Moreover, it is crucial to address concerns about insufficient CO2 capture performance and excessive regeneration energy. Therefore, non-aqueous homogeneous absorbents that do not produce precipitates, gels, or solids have gained considerable attention in recent years. In this study, a novel non-aqueous homogeneous absorbent based on polyamine/complex solvent was successfully developed by introducing ethylene glycol into the precipitation-producing polyamine/organic alcohol ether system. This modification resulted in improved CO2 capture performance and reduced regeneration energy. The AEEA/EG/2EE non-aqueous homogeneous absorbent showed a CO2 absorption capacity of 2.67 mol/kg and achieved an impressive regeneration efficiency of up to 81.65 % at the optimal desorption temperature (393 K) in only 40 min, surpassing the conventional MEA/H2O absorbent by a substantial margin (31.65 %). Thermodynamic analysis revealed that this absorbent exhibited a substantial reduction in both sensible and latent heat during CO2 desorption, resulting in a remarkable decrease of 42.8 % in total regeneration energy compared to the conventional MEA/H2O absorbent. The composite solvent EG/2EE was found not to be involved in the reaction process according to the 13C NMR analysis. The main absorption process involved the reaction between organic amine AEEA and CO2 to form carbamate, while the desorption process entailed reverse decomposition of carbamate for CO2 release. Therefore, utilizing ethylene glycol's advantageous properties for regulating polyamine/organic solvent systems presents a promising.

Computational Investigation of Co-Solvent Influence on CO2 Absorption and Diffusion in Water Lean Solvents

Computational Investigation of Co-Solvent Influence on CO2 Absorption and Diffusion in Water Lean Solvents

Two distinct molecular cloud populations detected in massive galaxies

ABSTRACT We present new ALMA observations of CO, CN, CS, HCN, and HCO$^{+}$ absorption seen against the bright and compact radio continuum sources of eight galaxies. Combined with archival observations, they reveal two distinct populations of molecular clouds, which we identify by combining CO emission and absorption profiles to unambiguously reveal each cloud’s direction of motion and likely location. In galaxy discs, we see clouds with low velocity dispersions, low line-of-sight velocities, and a lack of any systemic inflow or outflow. In galactic cores, we find high velocity dispersion clouds inflowing at up to 550 km s−1. This provides observational evidence in favour of cold accretion on to galactic centres, which likely contributes to the fuelling of active galactic nuclei. We also see a wide range in the CO(2-1)/CO(1-0) ratios of the absorption lines. This is likely the combined effect of hierarchical substructure within the molecular clouds and continuum sources which vary in size with frequency.

Environmental, economic and energy evaluation of alternative fuels for a steam power plant: Focus on biodiesel-nanoparticles utilization

Power plants are among the largest producers of GHGs. The fuel used in power plants is the main factor in the production of the emissions. Therefore, choosing a fuel that is environmentally optimal while being energy-efficient and economical is a key way to reduce GHG emissions. The addition of nanoparticles to biodiesel fuel not only improves the combustion efficiency of the fuel but also reduces the undesirable products. In this research, three supplementary fuels - fuel oil, diesel, and biodiesel-nanoparticles - are compared in terms of environmental, economic, and energy efficiency in a steam power plant. The changes in the power plant's self-consumption were measured by calculating the power consumption of the pump that delivers the fuel to the boiler. The results showed that diesel reduced the plant's efficiency by 0.00022 compared to using natural gas, which was the least of the other alternatives. The environmental analysis revealed that diesel produced the least amount of CO2 eq, but biodiesel-nanoparticle had a better CO2 footprint due to the higher absorption of CO2 in the cultivation phase of the raw material for biodiesel. The economic analysis for the fuels was carried out over ten years and based on the lifetime of the equipment purchased. Consequently, the total cost over the ten years for diesel was $967332.5161, which was $124475.8381 less than that for biodiesel-nanoparticle and $240935.3341 less than that for fuel oil. Finally, an overall comparison was made between the fuels using the AHP method. As the environmental criterion was the most important decision criterion, biodiesel-nanoparticle fuel was chosen with a marginal difference compared to diesel.

A novel non-aqueous tertiary amine system for low energy CO2 capture developed via molecular dynamics simulation

The current technology for capturing CO2 using alkanolamine aqueous solutions is known for its high energy and capital costs. As a result, developing new absorbents for low-energy CO2 removal remains a challenge. An additional activator can promote CO2 absorption performance. However, it is based on experimental screening. In this study, based on molecular dynamic simulation, we have successfully developed a novel and energy-efficient CO2 absorbent by combining N, N-Dimethylethanolamine (DMEA), and ethylene glycol (EG), with different activators, including ethanolamine (MEA), ethylenediamine (EDA), and piperazine (PZ). The addition of these activators significantly enhances the CO2 absorption performance of DMEA-based absorbents. Among them, DMEA-PZ-EG exhibits the maximum CO2 absorption rate and capacity, achieving 6.35 (g-CO2/(kg-soln.·min.)) and 96.5 (g-CO2/kg-soln.), respectively, representing a 230.1 % and 206.35 % improvement over 2M DMEA-EG absorbent. Moreover, compared to a 30 wt% MEA solution, the energy consumption of DMEA-based absorbents is reduced by 33.93–51.56 %. The reaction products were characterized using various spectroscopic techniques, including Attenuated Total Reflectance Fourier Transform Infrared spectroscopy (ATR-FTIR), and 1D and 2D Nuclear Magnetic Resonance spectroscopy (1H and 13C NMR). The NMR results confirmed that DMEA becomes protonated after CO2 absorption in the DMEA-EG mixture. The deprotonation of EG promote its reaction with CO2, resulting in the forming of EG carbonates. This assumption has been confirmed by the IR spectrum. Furthermore, the effect of activators on CO2 absorption has been analysed at the molecular level through molecular dynamics simulation and a new method is proposed to predict the CO2 absorption performance of non-aqueous solvents. Using non-aqueous DMEA absorbents presents a promising approach for improving CO2 capture efficiency, reducing energy consumption, and facilitating regeneration.

Prediction of CO2 absorbing performance of amine aqueous solution using random forest models

Designing an amine(s) solution for the chemical absorption of CO2 for carbon capture, utilization and storage is a significant challenge. To accelerate the development of high-performance amine solutions, a method for predicting the CO2 loading of amine(s) solution is studied. Available literature data are curated (45 amines, 3151 data points), and random forest regression is conducted using the data with descriptors calculated using HSPiP or RDkit software. The CO2 loadings of single amine aqueous solutions are regressed with high accuracy (R2 = 0.943, RMSE = 0.072–0.073 for the validation data). Feature importance analysis suggests that the partial charge of atoms in the amine is an important descriptor, as well as process parameters such as CO2 partial pressure and temperature. Based on the analysis, a simpler descriptor list is developed with temperature, CO2 partial pressure, and partial charges of N atoms calculated by density functional theory. CO2 loading of a single amine solution is regressed with an accuracy comparable to that of the above models (R2 = 0.931, RMSE = 0.079) with only 5 descriptors. Moreover, data including both single and blended amine solutions are regressed with high accuracy (R2 = 0.944, RMSE = 0.073) with only 8 descriptors. The generalization performances of the models are evaluated using the leave-one-group-out procedure. Although some outliers exist, the overall trend of almost all amines can be predicted using the procedure in this study.

Experimental study and analysis of CO2 and SO2 absorption in various water-based nanofluids by response surface methodology

The absorption of acidic gases in the oil and gas industries is important due to their toxicity and corrosive effects. Recently, the application of nanofluids based on aqueous or organic solvents as absorbents has been examined by a variety of researchers. In this study, a single bubble column was exploited to study the effect of water-based nanofluids on the absorption processes of SO2 and CO2 using response surface methodology (RSM) based on Box-Behnken three-level experiment design. With this in mind, CO2 and SO2 are separately injected at the bottom of a bubble column filled with one of the nanofluids: Al2O3-water, SiO2-water, or ZnO-water for each experiment. Then, the rate of SO2 or CO2 absorption in the nanofluids has been elucidated. The effect of important parameters including the weight fraction of the nanoparticles (NPs) (0.01, 0.055, and 0.1 wt.%), gas–liquid contact time (150, 300, and 450 s), and the diameter of nozzle for gas injection (0.46, 0.57, and 0.68 mm) have been studied. Results revealed that the maximum molar flux of both gases was observed in the ZnO-water nanofluid, followed by the SiO2-water nanofluid. In addition, increasing the nanoparticle mass fraction and the bubble size causes the molar flux to rise. However, increasing the gas–liquid contact time causes the molar flux of the mentioned gases to decrease. Finally, a set of the accurate equations has been proposed to predict the molar flux of SO2 and CO2 in the various nanofluids assessed in this work.

Heterologous expression of ACC deaminase gene in Pelargonium graveolens showed elevated tolerance to chromium stress.

An essential aromatic plant, Pelargonium graveolens, does not grow well in areas where chromium contamination is a problem. Because of oxidative stress and the collapse of the photosynthetic system, crops frequently sustain severe damage. The production of excess ethylene, known as stress ethylene, which is detrimental to plant growth, the formation of roots, and early senescence, is also increased by heavy metal exposure. The effectiveness of the 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase gene in transgenic Pelargonium graveolens under the control of CaMV 35S promoter was investigated to lessen the stress ethylene during chromium stress. Chromium was administered as potassium dichromate (K2Cr2O7) at four distinct concentrations (100µM, 200µM, 300µM, and 500µM) to transgenic and wild-type P. graveolens and stress-induced physiological changes were monitored. Transgenic P. graveolens demonstrated greater tolerance to chromium stress than wild-type P. graveolens, as evidenced by higher leaf-relative water content, chlorophyll content, CO2 absorption, transpiration rate, stomatal conductance, proline buildup, and antioxidant activity. The L1, L5, and L7, ACC deaminase-expressing transgenic lines also show a drop in ACC content during chromium stress, which subsequently lowered ethylene synthesis. Therefore, the reported transgenic P. graveolens lines having the ACC deaminase gene could be useful resources for growing in chromium-prone regions.

Energy consumption optimization of CO2 capture and compression in natural gas combined cycle power plant through configuration modification and process integration

Currently, natural gas combined cycle (NGCC) power plants account for a quarter of global electricity power supply and lead to greenhouse gas emissions. Carbon capture and storage (CCS) is one of the most effective technologies to reduce carbon emissions in the short term. However, the monoethanolamine (MEA)-based CO2 absorption and compression process is energy-intensive, which significantly reduces the power generation efficiency of NGCC. In addition, the waste hot and cold energy from NGCC and liquefied natural gas (LNG) regasification process, which are generally wasted, can be recovered for the CCS process. Therefore, this study aims to reduce the energy consumption of the carbon capture process and recover waste LNG cold energy and hot energy in the NGCC through configuration modification and process integration. The results show that the energy consumption of CO2 regeneration in the proposed CO2 capture process configuration is reduced by 18.03 %, and the net power efficiency of the NGCC plant increases from 48.88 % to 50.10 %. Furthermore, a cascade two-stage organic Rankine cycle is integrated into the system for waste heat recovery, which can generate 5.04 MW electric power and reduce the efficiency penalty of the plant from 13.72 % to 10.29 %. By contrast, the alternative application of LNG cold energy to the CO2 compression process reduces compression power by 3.95 MW with a lower footprint and utility requirement while the efficiency penalty is decreased by 3.15 %.

Improving O₂ Absorption in PVDF Membrane with Cross-Linked Polymer Coatings

Surface modification of polyvinylidene fluoride (PVDF) membranes using various polymers, including chitosan, nylon, dopamine, and EDA, was examined through SEM and FTIR analyses. SEM imaging unveiled the preservation of membrane porosity post-modification, affirming successful polymer integration without pore obstruction. Nylon coatings induced alterations in surface morphology, with enlarged pore apertures and roughened surfaces attributed to formic acid exposure during dissolution. FTIR spectroscopy confirmed the presence of the respective polymers, exhibiting characteristic peaks for each. Notably, membranes coated with EDA exhibited enhanced CO2 absorption flux owing to their inherently hydrophilic nature and larger pore dimensions. Optimization of EDA coating parameters, including deposition time and concentration, revealed a direct correlation between increased EDA deposition and enhanced CO2 absorption flux, emphasizing the significant impact of these parameters on membrane performance in gas absorption. Consequently, tailored surface modifications offer a promising avenue for enhancing membrane functionality in gas separation applications

The Essential of Trembesi in Djawatan: Identifikasi Persebaran Pohon Trembesi sebagai Penentu Biodiversitas di Kawasan Hutan Djawatan

Trembesi (Samanea saman) plays an important role in the Djawatan forest area. The presence of Djawatan forest in the city adds vital value to trembesi, such as maintaining ecosystem stability, soil stability, water supply stability, O2 supply, and CO2 absorption. This study aims to determine the density of trembesi trees in the Djawatan forest area. The presence of trembesi in the Djawatan forest is crucial for the numerous flora and fauna sheltered beneath it. Therefore, understanding the distribution pattern of trembesi in the Djawatan forest area is essential to ascertain environmental influences on the growth of trembesi. The research method used in this study was descriptive qualitative through observation and interviews. Trembesi distribution in this study was observed in four different zones: waterfront, rice field edge, central Djawatan forest, and settlement edge. Based on the research results, it is known that trembesi distribution is influenced by the surrounding environmental conditions. This is evidenced by data showing that the highest average density of trembesi is found in the central Djawatan forest area, which is 0.50%.

Diversity of carbon cycle-linked phyllosphere microorganisms: A key driver of CO2 flux in macrophyte-dominated aquatic systems

Planktonic microorganisms have been recognized as important components in biogeochemical cycling in lakes. However, research into the impact of phyllosphere microorganisms, particularly those involved in carbon cycling, on CO2 fluxes in macrophyte-dominated lakes within the context of global environmental changes remains scarce. Here, by employing high-throughput sequencing techniques, we experimentally tested how nutrient enrichment, top-down effects of fish and increases in dissolved organic carbon (DOC) affect CO2 exchange flux at the water-air interface by altering the community structure and functioning of phyllosphere bacteria on macrophytes. We found that our mesocosm ecosystems exhibited a net absorption of CO2, but nutrient enrichment significantly decreased the absorption ability. Mantel tests and multiple regression modeling also showed that eutrophication-associated parameters (total nitrogen, total phosphorus and ammonium nitrogen), pH, and extinction coefficient were the key drivers influencing abundance of phyllosphere functional microorganisms. In addition, these experimental treatments significantly altered the composition, diversity and co-occurrence networks of carbon cycling-associated phyllosphere microorganisms, which impacted the CO2 flux. Structural equation models and linear regression further showed that the Shannon Index of phyllosphere functional microorganisms related to carbon cycling (rather than plant volume inhabited - PVI) had a significant positive impact on CO2 fixation. This means that environmental changes—especially eutrophication—may hinder carbon sequestration by decreasing the diversity of phyllosphere microorganisms rather than reducing the abundance of submerged macrophytes. This study increases our understanding of carbon cycling processes in aquatic environments from a management perspective by emphasizing the importance of protecting the diversity of phyllosphere microorganisms in macrophyte-dominated lakes.

Toward an ecologically realistic experimental system to investigate the multigenerational effects of ocean warming and acidification on benthic invertebrates

AbstractHuman activities over the past 150 yr have led to significant carbon dioxide (CO2) emissions, causing global warming and ocean acidification. Surface ocean temperature has risen by 0.93°C since 1850, with projections of an additional +1.42°C to 3.47°C by 2080–2099. Ocean acidification, driven by CO2 absorption, has already lowered seawater pH by 0.1 units, affecting calcifying organisms, including shelled mollusks. Long‐term multigenerational studies on mollusk responses to both ocean acidification and warming, under realistic environmental conditions, are scarce. To address this knowledge gap, two mobile experimental units that can be deployed at the vicinity of shellfish farming areas were developed within the framework of the CocoriCO2 project. The experimental systems were designed to manipulate temperature and pH as offsets from ambient conditions. The experimental units have shown their effectiveness in terms of controlling and maintaining pH and temperature to assess the multigenerational effects of ocean warming and acidification on benthic invertebrates. Finally, the developed experimental systems can be modified easily to provide an educated assessment of the impact of other relevant environmental changes such as deoxygenation and changes in salinity.

An energy-efficient cyclic amine system developed for carbon capture from both flue gas and air

High energy consumption is a major barrier to the large-scale deployment of carbon capture processes from flue gases or air (direct air capture, DAC). The non-aqueous amines reported in literature possess a high energy efficiency for CO2 capture from flue gases, they struggle with gas streams containing ultra-dilute CO2, like air, due to poor absorption kinetics. This study developed novel 2-PE (2-piperidineethanol)/APZ (Aminoethylpiperazine) based CO2 absorbents to address these problems. The experiments and MD simulation results showed that the 2-PE/APZ-based absorbents possessed a superior absorption performance both in flue gas and air. Among the developed absorbents, when 2-PE/APZ mixed with DMF (Dimethylformamide), the CO2 loading reached to 1.004 mol/mole, as the theoretical maximum. In DAC tests, 87.31 % CO2 from the air was captured in 24 h experiments. The regeneration heat duty of 2-PE/APZ/DMF decreased to 1.694 KJ/g CO2, a 55.89 % reduction compared to the benchmark 30 wt% MEA. The CO2 absorption/desorption mechanism was analysed by NMR, In-situ FT-IR, and DFT calculation. It indicated that this significant improvement in CO2 absorption performance and the reduction in energy consumption are due to the synergistic effect of 2-PE and APZ. During CO2 absorption, CO2 reacts with APZ forming APZ zwitterion rapidly, then deprotonation to the 2-PE. The formation of protonated 2-PEH+ ion pairs with APZCOO- reduces hydrogen bonds and van der Waals forces among the amine-CO2 complex, facilitating easy regeneration at mild conditions while maintaining high reactivity. The combination of theoretical and experimental results indicates that 2-PE/APZ-based absorbents can serve as a promising alternative for carbon capture from flue gas to air with low energy usage.

Temperature-Driven Activated Sludge Bacterial Community Assembly and Carbon Transformation Potential: A Case Study of Industrial Plants in the Yangtze River Delta.

Temperature plays a critical role in the efficiency and stability of industrial wastewater treatment plants (WWTPs). This study focuses on the effects of temperature on activated sludge (AS) communities within the A2O process of 19 industrial WWTPs in the Yangtze River Delta, a key industrial region in China. The investigation aims to understand how temperature influences AS community composition, functional assembly, and carbon transformation processes, including CO2 emission potential. Our findings reveal that increased operating temperatures lead to a decrease in alpha diversity, simplifying community structure and increasing modularity. Dominant species become more prevalent, with significant decreases in the relative abundance of Chloroflexi and Actinobacteria, and increases in Bacteroidetes and Firmicutes. Moreover, higher temperatures enhance the overall carbon conversion potential of AS, particularly boosting CO2 absorption in anaerobic conditions as the potential for CO2 emission during glycolysis and TCA cycles grows and diminishes, respectively. The study highlights that temperature is a major factor affecting microbial community characteristics and CO2 fluxes, with more pronounced effects observed in anaerobic sludge. This study provides valuable insights for maintaining stable A2O system operations, understanding carbon footprints, and improving COD removal efficiency in industrial WWTPs.

Dicationic ionic liquid‐grafted UiO‐66 as efficient catalyst for CO2 conversion into cyclocarbonate under cocatalyst‐free and solventless conditions

CO2 chemical fixation offers a feasible approach for carbon mitigation and high‐value utilization, but it is still challenging to develop an efficient catalyst for CO2 conversion into cyclic carbonate. Herein, the triethylenediamine‐derived dicationic ionic liquids (DIL‐X, X = Cl, Br, and I) were grafted into UiO‐66 linkers through self‐assembly of Zr4+ ions and the mixed ligands of terephthalic acid and DIL‐bearing dicarboxylic acid, resulting in UiO‐66‐DIL‐Xn, (n designated as molar amount of the feeding DIL‐X). Their catalytic performance was evaluated by the epoxide cycloaddition reaction in the absence of solvent and cocatalyst. Among them, the UiO‐66‐DIL‐Cl0.4 catalyst exhibited outstanding performance, with a chloropropene carbonate yield of 92% and a high selectivity of 99% under 0.1 MPa CO2 at 110 °C for 16 h. Its high activity could be ascribed to the cooperativity among Lewis acidity of MOF nodes, the enhanced CO2 absorption, and the strong nucleophilicity offered by halogen ions of ionic liquid‐modified MOF. Moreover, UiO‐66‐DIL‐Cl0.4 presented excellent recyclability and substrate extension. A potential catalytic mechanism for the epoxide‐CO2 cycloaddition into cyclic carbonate has been proposed. This work will shed light on the rational design of functionalized MOFs‐based catalysts for CO₂ utilization.

Phase separation behavior and CO2 absorption kinetic analysis of DETA/DEA/DMAC biphasic absorbent

Lower regeneration energy and superior cyclic capacity have enabled biphasic absorbents great potential in the area of flue gas CO2capture. The liquid film mass transfer coefficient(kL) is a vital parameter in the development of absorbents with efficient CO2 absorption mass transfer performance, while the phase separation behavior of biphasic solutions could be an essential factor for the absorption mass transfer and the stability of absorber. However, systemic kinetic research towards biphasic absorbents, especially the impact of phase separation behavior, is limited. In this study, a typical amide-based biphasic absorbent diethylenetriamine(DETA)/diethanolamine(DEA)/N, N-dimethylacetamide(DMAC) which has achieved great reduction in regeneration energy, was selected as the subject of kinetic investigation in a wetted wall column. The CO2 overall mass transfer coefficient(KG) of DETA/DEA/DMAC exceeded other biphasic solvents, blended amine solution, and 40% K2CO3 solution, with 3 times that of 40% K2CO3 solution. Moreover, various operational conditions including absorption temperature, gas flow rate, and water content of solution were taken into account to build a multiple-condition kinetic mechanism to offer guidance for biphasic absorbents. Furthermore, phase separation behavior was revealed as the main blame for the deterioration in the liquid film chemical mass transfer process of biphasic solvents in the CO2 absorption process, resulting in the kL of DETA/DEA/DMAC before phase separation decreased by 75.3% at the phase separation stage. Therefore, it is crucial to ensure that the CO2 loading of the solution entering absorber is lower than the phase separation point in applications. After phase separation, DETA/DEA/DMAC split into the organic and aqueous phases, the kL of the aqueous phase gradually exceeded that of the organic phase as CO2 loading increased for its higher chemical enhancement factor(E).