CO2 Absorption Rate Research Articles

Computational study on CO2 absorption mechanism and structure–activity relationship of biphasic solvent

The biphasic solvents are conducive to improving the efficiency of CO2 capture and reducing the energy consumption caused by regeneration. This study explored their reaction process at the molecular level based on density functional theory (DFT): selection of diamines such as active amines with distinct amino groups, 1,4-butanediamine (BDA) and N-(2-aminoethyl)ethanolamine (AEEA), and with typical phase separation promoters, 2-(diethylamino)ethanolamine (DEEA), and N,N,N′,N′,N′′-pentamethyldiethylenetriamine (PMDETA). This study systematically explores the potential reaction paths in CO2 capture to quantitatively assesse the structure–activity relationships among different amines in different stages of absorption, the influence of reaction sequence on reaction rates, and further elucidates the characteristics of product formation and its impact on the phase separation process. The results indicated that the zwitterion mechanism is widely applicable and remains the dominant explanation for the biphasic solvent CO2 capture mechanism. The intramolecular proton transfer reaction is the key to influencing the absorption rate of CO2, but in the case of interproton transfer, the rate-determining step needs to be judged in conjunction with the type of amino groups on it. And the amine groups on AEEA react with CO2 in different orders, forming distinct zwitterions that have similar activity in later intramolecular proton transfers. Under the zwitterion mechanism, primary amino groups exhibit stronger proton affinity than secondary ones. In solvents approaching saturation stage, DEEA reacts with AEEA and CO2 earlier than PMDETA. This study reveals the reaction mechanism of biphasic solvents and the key paths in different phases, providing insights for developing new solvents.

Enhancing CO2 capture efficiency: Computational fluid dynamics investigation of gas-liquid vortex reactor configurations for process intensification

This study employs non-thermal Computational Fluid Dynamics (CFD) simulations to explore the efficacy of a gas–liquid vortex reactor (GLVR) for intensifying CO2 capture. The investigation concentrates on the multiphase flow and mass transfer behavior in diverse GLVR experimental units. Employing a multiphase Euler-Euler CFD model integrated with a Population Balance Model (CFD-PBM), a mass transfer model, and reaction kinetics, allows us to accurately simulate the reactive absorption of CO2 into aqueous Monoethanolamine (MEA). Experiments are conducted using a 30 wt% MEA solution for CO2 absorption, serving the purpose of model validation. This comprehensive approach enables a simulation of complex dynamics within the GLVR, emphasizing bubble breakage, coalescence, and reactive mass transfer processes. Examining bubble size distribution, pressure drop, CO2 absorption efficiency, and energy input systematically across various reactor geometries and operational conditions, our findings demonstrate that an optimized GLVR configuration significantly enhances CO2 absorption compared to the original design. Furthermore, the optimized GLVR outperforms state-of-the-art process intensification equipment in terms of CO2 absorption rate per unit reactor volume and energy efficiency.

Mass transfer and kinetic measurement and modeling for CO2 absorption into aqueous EAE and water-lean EAE/NMP solvents

Chemical absorption using amine solvent is currently available technology for CO2 capture from post-combustion flue gas. It is hindered by high operating cost and high capital cost due to high regeneration energy and slow CO2 absorption rate of amine solvent. Water-lean solvent of 2-(ethylamino) ethanol (EAE)/1-methyl-2-pyrrolidinone (NMP)/water could be a potential solution as it achieved significantly low regeneration energy of 2.3 GJ/tCO2 tested in a pilot plant. However, kinetics of CO2 reaction with EAE and mass transfer rate of CO2 absorption into EAE/NMP solvent are not fully understood. In this work, kinetics of CO2 absorption into unloaded aqueous EAE in 1–5 mol/L at 300–313 K and mass transfer of CO2 absorption into CO2-loaded EAE/NMP water-lean solvent in 5 mol/L with equilibrium CO2 partial pressure (PCO2*) range of 0.3–7 kPa at 312 K were studied in a wetted wall column. Kinetic data of aqueous EAE is interpreted by zwitterion mechanism, and the reaction is of first order with respect to EAE concentration in 1–5 mol/L at 300–313 K. CO2 absorption rate (kg’) of EAE/NMP water-lean solvent is 1.3–2.1 times greater than aqueous EAE due to the greater CO2 physical solubility. At lean and rich loading conditions, 5 M EAE in 3NMP/1water and 9NMP/1water show 2–7 times faster kg’ than 30 % MEA, and 1.4–2.5 times faster kg’ than 30 % PZ. It is found that EAE activity coefficient may increase in the presence of NMP in the solvent, and the estimated EAE activity coefficient in 1NMP/1water, 3NMP/1water, and 9NMP/1water are 2.13, 3.50, and 4.72, respectively. CO2 capacity of EAE/NMP solvent is 2–3.7 times greater than 30 % MEA and 1.2–2 times greater than 30 % PZ.

An integrated technology for the absorption and utilization of CO2 in alkanolamine solution for the preparation of BaCO3 in a high-gravity environment

In this study, an integrated technology is proposed for the absorption and utilization of CO2 in alkanolamine solution for the preparation of BaCO3 in a high gravity environment. The effects of absorbent type, high gravity factor, gas/liquid ratio, and initial BaCl2 concentration on the absorption rate and amount of CO2 and the preparation of BaCO3 are investigated. The results reveal that the absorption rate and amount of CO2 follow the order of ethyl alkanolamine (MEA) > diethanol amine (DEA) > N-methyldiethanolamine (MDEA), and thus MEA is the most effective absorbent for CO2 absorption. The absorption rate and amount of CO2 under high gravity are higher than that under normal gravity. Notably, the absorption rate at 75 min under high gravity is approximately 2 times that under normal gravity. This is because the centrifugal force resulting from the high-speed rotation of the packing can greatly increase gas-liquid mass transfer and micromixing. The particle size of BaCO3 prepared in the rotating packed bed is in the range of 57.2−89 nm, which is much smaller than that prepared in the bubbling reactor (>100.3 nm), and it also has higher purity (99.6 %) and larger specific surface area (14.119 m2/g). It is concluded that the high gravity technology has the potential to increase the absorption and utilization of CO2 in alkanolamine solution for the preparation of BaCO3. This study provides new insights into carbon emissions reduction and carbon utilization.

Hybrid behaviors of CO2 absorption into blended DEEA‐based solution for the improvement of capture performance

AbstractBACKGROUNDAt present, the chemical absorption method of CO2 capture is considered to be an effective means to reduce carbon emissions. The development of blended amine systems with excellent CO2 capture performance is the focus of research.RESULTThe hybrid behaviors of N,N‐diethylethanolamine (DEEA) with addition of monoethanolamine (MEA), 2‐(methylamino)ethanol(MAE) and 2‐((2‐aminoethyl)amino)‐ethanol(AEEA) as absorbents were investigated and developed to reduce the energy consumption for solvent regeneration in the CO2 capture process. The equilibrium solubility of CO2 for blended DEEA/MEA, DEEA/MAE and DEEA/AEEA with a series of molar ratios (0.0:2.0, 0.5:1.5, 1.0:1.0, 1.5:0.5 and 2.0:0.0) was examined. The experimental results showed that the values of CO2 equilibrium solubility of amine blends exhibited a compromise behavior between each individual amine solution. Additionally, the effects of molar ratios on the relative CO2 absorption rate, regeneration rate and CO2 cyclic capacity for the tested amine blends were studied using an improved rapid absorbent screening method.CONCLUSIONThe experimental data showed that the blended DEEA/MAE solution exhibits much higher CO2 cyclic capacity than that of DEEA/AEEA under the nitrogen atomic conservation. However, the mixing DEEA and AEEA could obviously reduce the CO2 equilibrium solubility and CO2 cyclic capacity compared with that of individual AEEA solution, indicating the DEEA had an inhibiting effect on AEEA. Furthermore, the mass transfer performances of DEEA, DEEA/MAE and DEEA/AEEA were tested in order to validate the accuracy of the improved rapid absorbent screening method. © 2024 Society of Chemical Industry (SCI).

Solar induced low-temperature phase separation in thermomorphic solvents for CO2 capture

Replacing steam with solar for CO2 regeneration is an incredibly promising approach. However, the high temperature required for solvent regeneration and the less-than-optimal photothermal conversion efficiency that prevents reaching the necessary regeneration temperature are significant limitations to this approach. In this work, thermomorphic solvents containing dimethylcyclohexylamine, N-methylcyclohexylamine and photothermal nanoparticles were prepared for CO2 capture. Nano carbon black, multi-walled carbon nanotube and carboxyl group functionalized multi-walled carbon nanotube were used as promoter for photothermal conversion. The experimental results exhibit the high CO2 absorption capacity of 0.1081 g/g solvent for the carboxyl group functionalized multi-walled carbon nanotube based solvent, and it can be efficiently regenerated under solar irradiation at a low temperature of ∼ 323 K. It is noteworthy that the photothermal material not only raise the solution temperature(∼325 K) during solar irradiation but also boosts the CO2 absorption rate, and leads to a ∼ 20.8 % increase in CO2 absorption capacity during the absorption process. Furthermore, the utilisation of photothermal regeneration for thermomorphic solvents can achieve an efficiency of 78.6 %, with a regeneration heat of 2.35 GJ/t CO2, resulting in an energy consumption reduction of approximately 41.1 % in comparison to 30 wt% monoethanolamine. The photo triggered regeneration of the thermomorphic solvent investigated in this study shows promising potential as an energy-efficient carbon capture technology.

Artificial Intelligence in Carbon Capture: Modeling CO2 Absorption Using Amine Blends

Carbon dioxide (CO2) from burning fossil fuels and other modernistic industrial processes is the main contributor to the greenhouse gas impact and global warming. The substantial quantities of CO2 produced by this exercise emphasize the pressing need to produce effective processes for removing it from gas products in order to prevent hazardous emissions into the atmosphere. This work an aim is to develop a predictive model for estimating the CO2 absorbed rate in various amine blends. The model was used an artificial neural network (ANN) with three inputs, which was trained on a dataset of 159 experimental data points associated with CO2 absorption by amine blends. Sterically hindered amines, primary amines, tertiary amines, and a few promoters along with physical solvents were among the amine blends that were taken into consideration. Three crucial input variables that were included in the study: Amine temperature (T), Blended amine concentration (AmH) and the Partial pressure of CO2(PCO2 ), and. RCO2 (unit as, kmol.m−2.s−1), or the rate of CO2 absorption, was the model’s target value. 15 neurons were found to be the ideal count of neural network models, and the dataset’s mean square error (MSE) was found to be 21.18. These findings demonstrated how effectively the created ANN model predicted CO2 absorption rates, representing a crucial step in the processes of carbon capture and sequestration.

Performance of cementitious materials prepared with magnesium slag and concrete slurry waste

Concrete slurry waste (CSW) and magnesium slag (MS) have similar compositions to cement, and both pose challenges for conventional reuse. Considering the carbonation activity of MS due to the presence of γ-C2S, MS and CSW were utilized to produce a type of low carbon cementitious material through CO2 curing. The carbonation products and microstructure of the mixture pastes were analyzed using XRD, XPS, FTIR, SEM, MIP, TG-DSC and NMR. The mixture pastes, comprising 26.6 % CSW by weight, demonstrated robust strength, achieving a compressive strength of 52.5 MPa and a flexural strength of 10.7 MPa, with a calculated CO2 absorption rate of 11.26 %. CSW effectively influenced the CO2 absorption rate in mixture pastes, actively participated in their matrix structure construction, and contributed to the formation of C-(A)-S-H gel. Interwoven carbonation products, such as SiO2-gel, amorphous calcium carbonate, calcite, etc., contributed to the increase in strength. The stability of the mixture pastes was demonstrated by the sustained increase in compressive strength after curing in water for 56 days, which acted as a softening coefficient with a value higher than 1.0. After being cured in water, the hydration of residual silicate minerals in the specimen following carbonation, combined with the reaction of CO32− released from calcium carbonate with gels, including C–S–H and C-(A)-S-H, promoted the evolution of strength. Water curing promoted the development of finer pores and resulted in a denser matrix structure within the slurries.

Dissociation Constant of Di‐ and Tri‐Basic Solvents Based on Piperazine and Its Derivatives for Post‐Combustion CO2 Capture

AbstractAmine solvents remain popular in the industries for post combustion carbon dioxide (CO2) capture. Dissociation constant of basic amine solvents plays significant role to influence the CO2 absorption. It is thus important to study the dissociation of new amine solvents for assessing their viability for CO2 capture. In the present work, potentiometric titration method is employed to determine the dissociation constants of dibasic (e. g., Piperazine (PZ), 1‐methyl piperazine (1‐MPZ) and tribasic amines (1‐(2‐aminoethyl‐piperazine) (AEPZ) which could be promising for formulating blended solvent system towards enhancing the rate of CO2 absorption. The estimated dissociation constants for the PZ and 1‐MPZ while match well with reported results, the dissociation constants for AEPZ has been determined newly here within the temperature range 298—318 K. In addition, the structural geometric parameters and Natural Bond Order (NBO) calculations of the amine solvents are performed based on Density Functional Theory (DFT). The NBO calculations predict charge distribution on the nitrogen and other elements, and envisage its effect on the pKa values of the amines. Further, potential energy surface (PES) scanning calculations are performed for AEPZ to explain it's ring inversion which is responsible for obtaining a single pKa value in experimental studies.

Investigations to intensified hydrogen production via sorption enhanced water gas shift reaction

Sorption enhanced water gas shift (SEWGS) reaction for the equilibrium enhanced hydrogen production is investigated using lithium orthosilicate (Li4SiO4) sorbents mixed with 1 wt% Pt/Al2O3 catalysts. The Li4SiO4 sorbents, synthesized using novel surfactant-mediated method, are characterized by ultra-fast CO2 capture rates with CO2 absorption capacity in the range of 319–333 mgCO2·g−s1. The thermogravimetric analysis results show ∼ 26 wt% of the carbonation sites are participating in the fast CO2 absorption (∼ 298 mgCO2·g−s1·min−1). The use of these sorbents with 1 wt% Pt/Al2O3 catalysts in the water gas shift reaction show a 103% increase in the hydrogen yield compared to the equilibrium concentration at 600◦C. The Li4SiO4 sorbent-catalyst combination show a shift in the equilibrium by preventing the reverse reaction in the temperature range of 600–650◦C. The SEWGS experiments show that the CO2 absorption capacities, and consequently the hydrogen yields, are affected by the diffusional resistance across Li2CO3 and Li2SiO3 product domains in the sorbent. The Li4SiO4 conversion rates during the SEWGS reaction are measured by sampling at different points in the SEWGS reaction and subsequent Rietveld analysis of the XRD patterns. The XRD results suggest the decrease in CO2 absorption rates as a result of the formation of additional Li2CO3 and Li2SiO3 fractions with decreasing Li4SiO4 phase in this nano-structured composite.

Structural investigation of aqueous amine solutions for CO2 capture: CO2 loading, cyclic capacity, absorption–desorption rate, and pKa

Understanding the CO2 capture performance of individual amines based on their structure is essential for efficient CO2 capture. In this study, the effects of the molecular structure of amine on CO2 loading, cyclic capacity, absorption–desorption rate, and pKa were investigated, and promising candidates for CO2 capture, along with an amine blending strategy, were proposed. The results showed that electron-donating alkyl groups increased the CO2 loading by increasing the electron density and pKa of the amino groups, whereas the electron-withdrawing hydroxyl group exhibited the opposite effect. Thirty amines were tested and categorized into Group A, B, C, and D based on CO2 absorption rate and cyclic capacity. Amines in Group B had a slow absorption rate but high cyclic capacity and included sterically hindered primary or secondary amines (2-amino-2-methyl-1-propanol, 2-(isopropylamino)ethanol, and 2-(tert-butylamino)ethanol) and sterically hindered tertiary amines with one hydroxyl group on the β–carbon (1-dimethylamino-2-propanol, 1-(2-hydroxyethyl)piperidine, N,N-diethylethanolamine and 1-diethylamino-2-propanol). The best-performing amines, Group A, were primarily multiamines (1-(2-hydroxyethyl)piperazine, 2-methylpiperazine, 2-(2-aminoethylamino)ethanol, N,N-dimethyl-1,3-propanediamine, N,N-diethyl-1,3-diaminopropane, hexamethylenediamine, diethylenetriamine, and 3,3’-diamno-N-methyldipropylamine) and included a sterically hindered heterocyclic secondary amine (2-piperidineethanol) with a hydroxyalkyl substituent on the α–carbon. Thus, amines in Group A are promising absorbents for CO2 capture, and blending amines in Group B with amines that have a high CO2 absorption rate (e.g., Group A) can also be a potential strategy for efficient CO2 capture.

Post-combustion CO2 absorption-desorption performance of novel aqueous binary amine blend of Hexamethylenediamine (HMDA) and 2-Dimethylaminoethanol (DMAE)

In this investigation, a novel aqueous Hexamethylenediamine (HMDA) and 2-Dimethylaminoethanol (DMAE) amine blend was made to capture CO2, which would strongly contribute towards net-zero emission. The capability of the novel amine blend was investigated by conducting CO2 absorption and desorption experiments. The major research findings were equilibrium CO2 loading (α), cyclic capacity, heat duty, regeneration efficiency, CO2 absorption and desorption rate, pH, density, 13C NMR and FTIR characterization, process optimization, and toxicity assessment. CO2 absorption experimental operating conditions: temperature (T) = 298.15–333.15 K, CO2 partial pressure (PCO2) = 10.13–25.33 kPa, mole fraction of HMDA (mHMDA) = 0.05–0.20, and solution concentration (C) = 1–3 mol/L. The optimum equilibrium CO2 loading was found to be 1.2174 mol CO2/mol amine at T = 298.15 K, PCO2 = 25.33 kPa, mHMDA = 0.20, and C = 1 mol/L. Similarly, desorption experiments were performed at constant T = 393.15 K and PCO2 = 25.33 kPa. For C = 3 mol/L, cyclic capacity was 1.5951 mol CO2/L solution, which was 61.77 % higher than the benchmark 30 wt% monoethanolamine (MEA). The heat duty and regeneration efficiency for 3 mol/L solution were calculated to be 131.24 kJ/mol CO2 and 60.47 %, respectively. The novel amine blend's heat of CO2 absorption was calculated to be −75.50 kJ/mol. Response surface methodology (RSM) was used for modeling and optimization: αoptimum = 1.04583 mol CO2/mol amine at T = 306.90 K, PCO2 = 21.53 kPa, mHMDA = 0.16 and C = 1.5 mol/L.

Analysis of the Impact of Nanofluids on the Improvement in CO2 Absorption using Taguchi Method

Capturing Carbon dioxide (CO2) has been the most crucial issue due to the dangerous impact of emissions of CO2 on the warming of globe and climate change. A novel class of solvent has been effectively employed in absorption technology in recent decades to eliminate CO2. The process of employing nanofluids to enhance CO2 uptake is receiving a lot of attention. However, other studies are needed to enhance the nanofluid absorption rate. The purpose of this study was to use nanofluid (based on amines) to optimize the absorption process for CO2 from flue gas. The technique was designed to extract CO2 from exhaust gas. This paper discusses the removal of CO2 from flue gas and parameter adjustments that increase overall removal efficiency. The nanoparticle concentration, stirring speed, and nanoparticle size were all varied during the tests. The experimental design using Taguchi method was applied to determine the optimal conditions of nanofluid for the process of absorption. Taguchi experimental design to investigate the perfect setting for the highest possible rate of CO2 absorption. The best settings were found to be a nanoparticle beginning concentration of 0.01 vol%, a stirrer speed of 4 rpm, and a nano size of 60 nm, according to the results of multiple regression and signal to noise ratio (S/N). Additionally, the analysis of variance (ANOVA) was used to determine the relative significance of each factor. The results show that the proportion of contributions were as follows: mixing speed (rpm) 46.56%, nano concentration (vol.%) 4.33%, and nano size (nm) 43.18%. The most useful parameter was the mixing speed (rpm). The experimental and anticipated values agreed well with regression analysis (R2=97.26%), and the findings of the confirmation test demonstrated that the CO2 absorption rate was 0.0029 g/s; a success that is highly advantageous for industrial uses.

Adopting green absorbent for CO2 capture and agricultural utilization: Biogas slurry and biomass ash case

Previously, the once-through CO2 chemical absorption process by biogas slurry was experimentally verified to offer the unique advantages like low energy consumption, cost-effectiveness, and feasibility of CO2 fixation in plants. However, this technology also faces some challenges and limitations, including a low CO2 absorption rate and performance. To improve the effectiveness and reliability of this innovative carbon capture, utilization, and storage (CCUS) technology, this study proposes a novel method to enhance the CO2 absorption performance without affecting agricultural applications of CO2 by mixing biogas slurry with biomass ash as the green CO2 absorbent. The results indicate that when the solid-liquid mass ratio of biomass ash to biogas slurry is 5:10, the CO2 loading of the biomass ash and biogas slurry mixture (BA-BS) reaches 936.7 ± 59.1 mmol/kg. Furthermore, the pH of the BA-BS remains stable at 6.9, meeting the rhizosphere pH requirements for plant cultivation. The CO2 absorption of the BA-BS liquid phase, referred to as improved biogas slurry (IBS), reaches its maximum at 230.4 ± 3.5 mmol/L, which is 126.8% higher than that of the unimproved biogas slurry. The nitrogen content in the BA-BS solid phase, calling improved biomass ash (IBA), also reaches its maximum at 4.24 ± 0.74 mg/g, thereby expanding the agricultural utilization of biomass ash. The most reasonable and effective way of utilizing CO2-rich mixed biogas slurry and biomass ash involves use IBA as the base fertilizer for tomato cultivation, supplemented later with IBS to promote growth. This optimal application allows for substantial utilization of CO2, introduced into the tomato cultivation environment by IBA and IBS. The carbon fixation of a single tomato has improved by 108.2%. This study thus provides a feasible solution for high-value negative carbonization of biogas slurry and biomass ash.

Kinetic study on CO2 absorption by aqueous secondary amine + tertiary amine blends: Kinetic model and effect of the chain length of tertiary amine

To study the reaction kinetic of CO2 absorption in aqueous secondary amine + tertiary amine blends, 1-Diethylamino-2-propanol (DEA2P) and 1-Dimethylamino-2-propanol (DMA2P) were selected to form aqueous amine blended solutions with 2-(Ethylamino) ethanol (EAE), respectively. The reaction kinetics of CO2 absorption in aqueous EAE/DEA2P solutions and EAE/DMA2P solutions were explored using the stopped-flow apparatus, and the reaction mechanism was then explored by Density Functional Theory (DFT) calculations. Based on the zwitterion mechanism and the base-catalyzed hydration mechanism, experimental reaction kinetics models were established. It was found that in secondary amine + tertiary amine blends, tertiary amines played the key role of the proton acceptor in step of zwitterion deprotonation. With the increase of the chain length of tertiary amine, the CO2 absorption rate increased. Through analysis, it was found that the main reason for the increased CO2 absorption rate was the presence of H-bond or the stronger proton affinity of N atom.

Investigation of Rational Design of Amine Solvents for CO2 Capture: A Computational Approach

Solvent selection and design are critical in the CO2 capture process as the choice of solvent directly impacts the cost of the process, capture efficiency, equipment size, and regeneration energy. In the present study, 1MPZ-PZ, PZ, PIP, DEEA and MEA-DEEA are analyzed in terms of interaction intensity (attractive and repulsive) and diffusivity by molecular dynamic simulation. A high intermolecular interaction intensity promotes CO2 absorption, while intra-molecular interaction intensity affects CO2 desorption during the regeneration process. Diffusivity is also an important factor for a fast CO2 uptake rate, which is desirable for efficient CO2 capture. The interpretation of diffusivity and intermolecular interaction intensity findings is conducted through mean square displacement and radial distribution function analysis, respectively. The order of interaction intensity in various amines is DEEA>MEA-DEEA>PIP>1MPZ-PZ. It shows that DEEA can increase the CO2 absorption rate as it shows the highest interaction intensity in pure and blended amine systems. The results of the intramolecular interaction intensity show that it is easier to regenerate DEEA, PIP, PZ, and 1MPZ than MEA. The temperature effect on the interaction intensity is revealed at higher temperatures, where the molecular structure becomes unstable due to higher thermal motion, which is the cause of lower interaction intensity. On the other hand, the mean square displacement analysis for the diffusivity rate shows that PZ shows the highest diffusivity rate compared to other selected solvents. The order of diffusivity rate in various pure and blended amine systems is PZ>PIP>1-MPZ-PZ>MEA-DEEA. The diffusivity of various amine solvent systems increases with temperature. As examined in this current research, assessing solvent characteristics holds significant importance in optimizing the most effective solvent system.

Effect of UV Stress on the Antioxidant Capacity, Photosynthetic Activity, Flavonoid and Steviol Glycoside Accumulation of Stevia rebaudiana Bertoni

Lighting conditions are an important controller of plant growth and development, and they affect secondary metabolite synthesis. In this research, we explored the effect of additional UV irradiation of various ranges in addition to the main one at PPFD 160 µmol m−2 s−1 on the accumulation of some secondary metabolites of stevia (Stevia rebaudiana Bertoni). The fresh weight of leaves was slightly higher under additional UV-A and UV-B irradiation compared with the control variant, and the leaf surface area was significantly larger, respectively, by 23.3 and 20.7% than in the control variant, while the rate of photosynthesis did not decrease. Plants under additional UV-B and UV-C irradiation were under the greatest light stress, as evidenced by a decrease in antioxidant capacity by an average of 30% compared to the control and UV-A. The total flavonoid content was significantly higher (by 74%) under UV-B irradiation. The highest concentration of steviol glycoside was observed during budding and flowering under UV-B and UV-C irradiation (by 13.2 and 11.3%, respectively). Analysis of hyperspectral images, chlorophyll fluorescence, and vegetation indices showed light stress increasing under UV-C irradiation, which caused an increase in the relative chlorophyll content, scorches, leaf morphology changes, a CO2 absorption rate decrease, and plant growth inhibition. UV-B irradiation can be used as an optimal type of irradiation based on a set of indicators.

CO2 solubility and absorption rate analysis of a mixed poly(oxymethylene) dimethyl ethers (PODE3–5) solution

Efficient and economical carbon capture is critical to counteract the diverse problems of global warming. In this work, the solubility of carbon dioxide (CO2) in different poly(oxymethylene) dimethyl ethers (PODE) solutions was experimentally investigated at temperatures from 278.15 to 308.15 K and pressures up to 1.2 MPa. The Henry's law constants of CO2 in the PODE system were determined and compared with other types of physical absorbents, which revealed PODE3–5 has great CO2 absorption ability in terms of molar and mass fraction. Meanwhile, the initial absorption rate of the physical absorption process of PODE3–5 was calculated and compared with commercially available absorbents using a gas absorption rate relationship. It was shown that the absorption rate of PODE3–5 in the CO2 absorption process is faster than that of other commercial absorbents. The CO2 solubility data of PODE3–5 were also correlated using the Jou-Mather model and the perturbed-chain statistical association fluid theory (PC-SAFT) equation of state model, and the recycling performance of the PODE3–5 absorbent was tested.

Study on the zinc porphyrins as potential carbonic anhydrase mimics for promoting CO2 absorption in K2CO3 solution

Zinc porphyrins, boasting a coordination environment akin to that of natural carbonic anhydrase (CA), coupled with excellent structural stability, built-in hydrophobic pocket, and suitable charge of center Zn2+, were considered as potential CA-mimics for CO2 capture. To validate this assumption, three zinc porphyrin representatives, zinc porphin (ZnP), zinc protoporphyrin IX (ZnPP), and zinc meso-tetrakis(N-methylpyridinium-4-yl) porphyrin (ZnTMPyP), were prepared, and tested performance in enhancing CO2 absorption in water and K2CO3 solutions. The results from CO2 absorption experiments indicated that ZnTMPyP with the optimal dosage increased CO2 absorption rate by 44.25 % in water, and ZnPP with the optimal dosage increased the CO2 absorption rate by 63.67 % in 20 wt% of K2CO3 solution, which are respectively 1.53 and 2.07 times of CO2 absorption performance of zinc cyclen (ZnC), the most effective CA-mimic reported. Besides, the zinc porphyrins demonstrated excellent stability and reusability throughout five cycles of CO2 absorption and desorption, which are vital aspects for practical applications. Through the calorimetric method and density functional theory (DFT) calculations, it was confirmed that the prepared zinc porphyrins had similar enzymatic behavior and catalytic CO2 hydration pathway to natural CA. According to the results of characterization and DFT calculations, high dispersion, the lowest charge of the Zn2+ center, and the existence of additional CO2 adsorption sites (propionate ions), endow ZnPP with the highest catalytic activity in the K2CO3 solution.

Optimization of K2CO3 exposure conditions using response surface methodology for CO2 capture with 2-methylpiperazine and monoethanolamine as promoters

In this study, the optimization of potassium carbonate (K2CO3) exposure conditions for CO2 capture with the use of 2-methypiperazine (2MPz) and monoethanolamine (MEA) as promoters was investigated. The tested operating conditions for the CO2 capture process included the pH, temperature, K2CO3 dose, gas flow rate, and pressure, and their effect on the CO2 absorption/desorption rate and CO2 absorption efficiency was assessed. Response surface methodology (RSM) was also employed to determine the equations for the optimal long-term operating conditions. The results showed that the CO2 absorption rate and efficiency increased under K2CO3 exposure with an increase in the pressure and loading rate. Moreover, for the temperature the absorption efficiency first increase and then decreases with increase in temperature, however, the with increase in temperature the faster absorption were observed with lower absorption loading rate. Furthermore, pH had a more complex effect due to its variable effects on the speciation of bicarbonate ions (HCO3−) and carbonate ions (CO32−). Under higher pH conditions, there was an increase in the concentration of HCO3−, which has a higher CO2 loading capacity than CO32−. Contouring maps were also used to visualize the effect of different exposure conditions on the CO2 absorption rate and efficiency and the role of 2MPz and MEA as promoters in the K2CO3 solution for CO2 absorption. The results showed that the mean CO2 absorption rate was 6.76 × 10−4 M/L/s with an R2 of 0.9693 for the K2CO3 solution containing 2MPz. The highest absorption rate (6.56–7.20 × 10−4 M/L/s) was observed at a temperature of 298–313 K, a pressure of >2 bar, a pH of 8–9, and a loading rate of 80–120 L/h for a concentration of 1–3 M K2CO3 and 0.05–1.5 M 2MPz. The CO2 absorption efficiency exhibited a variation of 56–70% under the same conditions.