CO2 Absorption Capacity Research Articles

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.

Performance comparation of MEA and EDA in electrochemically-mediated amine regeneration for CO2 capture

Electrochemically-mediated amine regeneration (EMAR) for CO2 capture was recently developed as a promising substitute for conventional amine-based CO2 capture by avoiding the amine thermal regeneration process. A suitable solvent is significant for the overall performance and the scale-up of the EMAR system. However, there is currently a lack of comprehensive solvent comparison methods. In this work, a systematic comparison was conducted to elucidate the absorption and desorption behavior of the most discussed monoethanolamine (MEA) and ethylenediamine (EDA) in the EMAR process. Firstly, the CO2 absorption performance was compared by considering the CO2 absorption capacity, absorption rate, and coordination ability separately. Subsequently, the performance of absorbents was compared from the perspective of thermodynamics. Results indicated that the complex of Cu(II)-EDA shows higher stability which means it is more competitive than MEA in releasing the absorbed CO2 in the EMAR process. Then, the electrochemical behaviors comparison of MEA and EDA shows that the electrochemical reactions in EDA solvent are simpler and easier to occur, but the poor diffusion performance of reactive ions in EDA hinders its scale-up application. Finally, the CO2 desorption performance in MEA and EDA was carefully studied. A competitive and practically instructive desorption energy consumption of 42.4 kJe/mol CO2 with 300 A/m2 current density was obtained in EDA solvent. Overall, compared with MEA, EDA is more recommended to be used as an absorbent in the EMAR system.

Elucidation of Operating Parameters Influencing the Ultrasonic-Assisted Absorption of Bulk CO2 Using Unpromoted and Promoted Methyldiethanolamine

Various acid gas sweetening processes can be used to separate CO2 from natural gas. As one of the most matured and widely utilized gas sweetening processes, absorption has been continuously improved to meet the stringent separation requirement. Ultrasonic irradiation has recently been introduced as an alternative technique to intensify the absorption process. Nevertheless, further studies are still needed to mature this new technique, particularly using slow kinetic absorbents possessing high inherent CO2 absorption capacity. Moreover, performing experimental studies using blended solvents in the high-frequency ultrasonic-assisted absorption system has also introduced a new idea in this field. This experimental study presents the CO2 absorption into aqueous solutions of methyldiethanolamine (MDEA) and piperazine (PZ)-promoted MDEA in an ultrasonic-assisted batch reactor. The influences of various operating parameters on CO2 absorption performance were evaluated in both promoted and unpromoted conditions. The parameters of the experiments included ultrasonic power at a frequency of 1.7 MHz, absorbent concentration, temperature, and CO2 partial pressure. Based on the results, ultrasonic power was found to be the most critical factor influencing the CO2 absorption rate. Moreover, the potential of the high-frequency ultrasonic-assisted CO2 absorption reactor was further elucidated via comparison with the conventional stirring and silent conditions under identical operating conditions. The highest CO2 absorption rate was achieved at an ultrasonic power of 12.36 W, a temperature of 70 °C, a CO2 partial pressure of 10 bar, an absorbent concentration of 50 wt %, and a promoter concentration of 5 wt %. In addition, the CO2 absorption rate in the high-frequency ultrasonic-assisted reactor using the MDEA absorbent was 28 and 52 times higher compared to stirring and silent conditions, respectively. The CO2 absorption rate enhancement was approximately 17 and 54 times higher for the PZ-MDEA.

Effective CO2 Capture and Selective Photocatalytic Conversion into CH3OH by Hierarchical Nanostructured GO-TiO2-Ag2O and GO-TiO2-Ag2O-Arg.

The attenuation of greenhouse gases, especially CO2, as one of the main causes of global warming and their conversion into valuable materials are among the challenges that must be met in the 21st century. For this purpose, hierarchical ternary and quaternary hybrid photocatalysts based on graphene oxide, TiO2, Ag2O, and arginine have been developed for combined CO2 capture and photocatalytic reductive conversion to methanol under visible and UV light irradiation. The material's band gap energy was estimated from the diffuse reflectance spectroscopy (DRS) Tauc analysis algorithm. Structural and morphological properties of the synthesized photocatalysts were studied using various analytical techniques such as Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The calculated band gaps for GO-TiO2-Ag2O and GO-TiO2-Ag2O-Arg were 3.18 and 2.62 eV, respectively. This reduction in the band gap showed that GO-TiO2-Ag2O-Arg has a significant visible light photocatalytic ability. The investigation of CO2 capture for the designed catalyst showed that GO-TiO2-Ag2O-Arg and GO-TiO2-Ag2O have high CO2 absorption capacities (1250 and 1185 mmol g-1, respectively, at 10 bar and 273 K under visible light irradiation). The amounts of methanol produced by GO-TiO2-Ag2O and GO-TiO2-Ag2O-Arg were 8.154 and 5.1 μmol·gcat1·h-1 respectively. The main advantages of this study are the high efficiencies and selectivity of catalysts toward methanol formation. The reaction mechanism to understand the role of hybrid photocatalysts for CO2 conversion is deliberated. In addition, these catalysts remain stable during the photocatalytic process and can be used repeatedly, proving to be enlightening for environmental research.

Extraction of total carbohydrates by solvents from the microalgae <em>Chlorella</em> vulgaris and analysis of the influence of NaNO3 and photoperiods on microalgae cell growth

The development of new resources for ethanol production has been changing over the years, and microalgae use has become one of the most ecological alternatives. Microalgae are increasingly being used due to their biochemical composition, rich in carbohydrates and proteins, in addition to several properties such as high CO2 absorption capacity. One of the most cultivated and studied microalgae today is Chlorella vulgaris since it has high growth rates and can be cultivated in different environments and conditions. Therefore, microalgae biomass is composed of potential ingredients for the production of biofuels. Considering the above, the objective of this work is to extract the total carbohydrates stored in the cellular structure of the microalgae by the organic solvent extraction method, hexane/ethanol (1:2) and by ionic liquid/ethanol (1:2), evaluating different conditions of microalgae cultivation. For this, 9 experiments were carried out, varying according to the culture medium in which the microalgae were introduced, containing BG-11 medium with different concentrations of NaNO3 (sodium nitrate) and forced aeration, in addition to different cultivation photoperiods. The reading of the results showed that the breakdown of the microalgae cell wall was better with acid hydrolysis and extraction with hexane. Thus, the highest efficiency in the extraction of carbohydrates was with a sodium nitrate concentration of 2300 and a photoperiod of 16 hours, during the entire period evaluated.

Calcium sulphoaluminate cement from solid waste with nano-TiO2 addition for high-efficiency CO2 capture

Calcium sulphoaluminate cement from solid waste (WCSA) has a relatively lower sintering temperature and low CO2 emission, meanwhile, the low cost of WCSA and the good CO2 absorption capacity make it one of the current hot topics of research. In this work, based on the optimal water-cement ratio, the effect of titanium oxide (TiO2) on the pore structure and the hydration process of WCSA were explored. The hydration process and microscopic evolution were studied by compressive strength test, carbonization test, Brunauer-Emmet-Teller measurement (BET), X-ray diffraction (XRD), the heat of hydration, thermogravimetric analysis (TG), and scanning electron microscope (SEM). The effect of nano-TiO2 on the carbon sequestration behavior of WCSA was also analyzed. The results show that WCSA with a water-cement ratio of 0.4 is the optimal carbonization substrate and nano-TiO2 will make the pore structure more uniform and dense, simultaneously increasing the adsorption pressure for the CO2. Meanwhile, the nano-TiO2 can effectively promote and regulate the crystallization, nucleation, and growth of ettringite crystals. It can be found that the WCSA containing 1% nano-TiO2 has the highest carbon capture ability among all the contents, and the ettringite crystal is concave hexahedron. The research considered that the concave surface with large specific surface energy can effectively increase the contact area between CO2 and ettringite, which greatly improved the CO2 absorption of ettringite. Overall, WCSA containing nano-TiO2 may provide some new opportunities for efficient carbon capture.

Synthesis and characterization of ammonium-based protic ionic liquids for carbon dioxide absorption.

A series of ammonium-based protic ionic liquids (APILs) namely ethanolammonium pentanoate [ETOHA][C5], ethanolammonium heptanoate [ETOHA][C7], triethanolammonium pentanoate [TRIETOHA][C5], triethanolammonium heptanoate [TRIETOHA][C7], tributylammonium pentanoate [TBA][C5] and tributylammonium heptanoate [TBA][C7] was synthesized via proton transfer. Their structural confirmation and physiochemical properties namely thermal stability, phase transition, density, heat capacity (Cp) and refractive index (RI) have been determined. Specifically, [TRIETOHA] APILs have crystallization peaks ranging from -31.67 to -1.00 °C, owing to their large density values. A comparison study revealed the low Cp values of APILs in comparison to monoethanolamine (MEA) which could be advantageous for APILs to be used in CO2 separation during recyclability processes. Additionally, the performance of APILs toward CO2 absorption was investigated by using a pressure drop technique under a pressure range of 1-20 bar at 298.15 K. It was observed that [TBA][C7] recorded the highest CO2 absorption capacity with the value of 0.74 mole fraction at 20 bar. Additionally, the regeneration of [TBA][C7] for CO2 absorption was studied. Analysis of the measured CO2 absorption data showed marginal reduction in the mole fraction of CO2 absorbed between fresh and recycled [TBA][C7] thus proving the promising potential of APILs as good liquid absorbents for CO2 removal.

Carbon dioxide absorption in packed bed of lithium orthosilicate pebbles

ABSTRACT Lithium orthosilicate (Li4SiO4) has the highest carbon dioxide (CO2) absorption capacity among the other lithium-based ceramic materials and is also suitable for high-temperature application for CO2 absorption. In this work, lithium orthosilicate pebbles of 1.0 mm size with 20% excess lithium carbonate were synthesized and fabricated by using Solid State Reaction Process (SSRP) and experiments were carried out to study the effect of various process parameters on its adsorption capacity of CO2 from air-CO2 mixture at elevated temperatures. The various process parameters studied were: operating gas flow rate, bed wall temperature and CO2 concentration in air on which very limited works have been reported. Effects of operating temperature, flow rate and inlet concentration of CO2 on absorption capacity have been studied to develop break through curves. The cyclic tests have been carried out with 15% CO2 concentration in air at 400°C and 200 LPH flowrate using the same material and carried out 135 consecutive absorption-desorption experimental runs. It was found that the CO2-absorption capacity of Li4SiO4 pebbles at 400°C and 200 LPH flowrates is about 31% for 30% carbon dioxide concentration in air and 22% for 15% carbon dioxide concentration in air. Moreover, no reduction in CO2-absorption capacity of the material was observed even after 135 consecutive absorption-desorption cycles.

Influence of alkyl substituent on thermophysical properties and CO2 absorption studies of diethylenetriamine- based ionic liquids

Diethylenetriamine (DETA) based protic ionic liquids (ILs) containing different carboxylate as anions have been synthesized and characterized by using NMR, ATR-FTIR, and mass spectroscopic techniques. The alkyl chain of carboxylate anion varied from formate (For) to octanoate (Oct). The synthesized DETA based ILs were subjected to CO2 absorption studies, and the results revealed that the CO2 absorption increases with increasing alkyl chain length of anion, and maximum CO2 absorption capacity were observed for [DETA][Oct]. The CO2 absorption results were confirmed by FTIR spectroscopic studies by monitoring the carbamate peak formation at 1634 cm−1. Furthermore, the physicochemical properties such as density (ρ), polarity, speed of sound (u), viscosity (η), and refractive index (nD) were determined at different temperatures from 293.15 to 333.15 K and pressure (0.1 MPa). The thermal stability of synthesized ILs was established using TGA analysis. The derived thermodynamic properties such as thermal expansion coefficient (α), isentropic compressibility (βS), intermolecular free length (Lf), lattice potential energy (UPOT), molecular volume (V), standard entropy (S°), activation energy (En), molar refraction (Rm) and free volume (Vf) were calculated from experimental data to predict the intermolecular interactions and space between constituent ions in the ILs and it was found that [DETA][Oct] having highest CO2 absorption capacity due to its higher free volume and basicity compare to other ionic liquids.

Mechanism Study of Imidazole-Type Deep Eutectic Solvents for Efficient Absorption of CO2.

Deep eutectic solvents (DESs) are a new class of green solvents that exhibit unique properties in various process applications. In this regard, this study evaluated imidazole-type DESs as solvents for carbon dioxide (CO2) capture. A series of imidazole-type DESs with different ratios was prepared through one-step synthesis. The absorption capacity of CO2 in imidazole-type DESs was measured through weighing, and the effects of temperature, hydrogen bond acceptors, hydrogen bond donors, and water content were discussed. DESs absorbed the effects of CO2. Im-MEA (1:2) was selected to linearly fit lnη and 1/T using the Arrhenius equation under variable temperature conditions, and a good linear relationship was found. The results show the best absorption effect for Im-MEA (1:4). At 303.15 K and 0.1 MPa, the absorption capacity of Im-MEA (1:4) was as high as 0.323 g CO2/g DES; through five times of absorption-desorption after the cycle, the absorption capacity of DES was almost unchanged. Finally, the mechanism of CO2 absorption was studied using Fourier transform infrared and nuclear magnetic resonance spectroscopy. The absorption mechanism of imidazole-type DESs synthesized using imidazole salt and an amine-based solution was chemical absorption, and the reaction formed carbamate (-NHCOO) to absorb CO2.

Metal Oxyhydroxide Catalysts Promoted CO2 Absorption and Desorption in Amine-Based Carbon Capture: A Feasibility Study.

The huge energy penalty of CO2 desorption is the greatest challenge impeding the commercial application of amine-based CO2 capture. To deal with this problem, a series of metal oxide and oxyhydroxide catalysts were synthesized in this study to kinetically facilitate the CO2 desorption from 5.0 M monoethanolamine (MEA). The effects of selected catalysts on CO2 absorption kinetics, CO2 absorption capacity, CO2 reaction enthalpy, and desorption duty reduction of 2.0 M MEA were investigated by a true heat flow reaction calorimeter to access the practical feasibility of the catalytic CO2 desorption. The kinetic study of catalytic CO2 desorption was also carried out. CO2 desorption chemistry, catalyst characterization, and structure-function relationships were investigated to reveal the underlying mechanisms. Results show that addition of the catalyst had slight effects on the CO2 absorption kinetics and CO2 reaction enthalpy of MEA. In contrast, the CO2 desorption efficiency greatly increased from 28% in reference MEA to 52% in ZrO(OH)2-aided MEA. Compared to the benchmark catalyst HZSM-5, ZrO(OH)2 exhibited a 13% improvement in CO2 desorption efficiency. More importantly, compared to the reference MEA, the CO2 desorption duties of ZrO(OH)2 and FeOOH-aided MEA significantly reduced by 45 and 47% respectively, which are better than those of most other reported catalysts. The large surface area, pore volume, pore diameter, and amount of surface hydroxyl groups of ZrO(OH)2 and FeOOH afforded the catalytic performance by promoting the adsorption of alkaline speciation (e.g., MEA and HCO3 -) onto the particle surface.

Sulphur vacancy-rich PCdS/NiCoLDH promotes highly selective and efficient photocatalytic CO2 reduction to MeOH

In this report, a facile hydrothermal approach is employed in modulated phosphorus-doped CdS (PCdS) nanorods over optimal molar ratio of Ni & Co in LDH to engineer a robust hierarchical PCdS/NiCoLDH photocatalytic system for efficient reduction of CO2 to methanol under visible light. The S vacancies and their impurity levels are approximately near towards the Fermi levels after interstitial P doping, and is found to be an efficient level to trap electrons in PCdS, which can affect the dynamic characteristics of photogenerated electrons and hence extend their lives. The time-dependent kinetics indicated the selective formation of CH3OH with 684 μmolg−1 cat, for 4 h (AQY= 3.8%) and 220 μmol-g−1cat, (AQY= 1.3%) under 20 W LED lamp. The correlation between the electronic structures and photo physical properties of the defect rich photocatalyst is substantiated from the experimental and theoretical studies. The enhanced activity is attributed to the increased CO2 absorption capacity over the mesoporous structures as well as the interlayer spaces. The sulphur vacancies over the PCdS can provide excess active sites towards activation, light absorption, as well as the CO2 conversion. This work presents deep insights into the synthesis of NiCo-LDH-based materials with rationally designed carrier transfer behaviors for not only in photocatalytic reactions but also in photovoltaic fields.

Comprehensive exploration of the adsorption capacity of innovative betaine-based deep eutectic solvents for carbon dioxide capture

Compared with traditional organic solvents and ionic liquids, deep eutectic solvents (DESs) as innovative emerging solvents has attracted widespread attentions in the field of CO2 absorption due to its remarkable advantages, such as low melting point, cheapness, easy preparation, regeneration and biodegradation. Herein the halogen-free DESs constituting of betaine as hydrogen bond acceptor, 1,2-propanediol and diethylene glycol as hydrogen bond donor were employed to absorb CO2. The CO2 absorption capacity of DESs with different molar ratios was measured at a certain temperature (303.15–348.15 K) and pressure (180–770 kPa). The results show that the solubility of CO2 in DESs can be improved by decreasing the temperature and increasing the pressure. The solubility of CO2 in DESs increases with increasing mole ratio of 1,2-propanediol, but decreases with increasing mole ratio of diethylene glycol. The Jou and Mather model was used to calculate the CO2 solubility data, which was compared with the experimental results. Through the estimated Henry's constant, the gibbs free energy, enthalpy and entropy of absorption were calculated and the results indicate that the CO2 dissolution in DESs is a non-spontaneous exothermic process. Regeneration can be achieved by depressurizing and heating the DES-CO2 system. By comparing with the Henry's constant Hm of the reported solvents, this work provides the possibility and space for further optimizing the use of new materials DESs to capture CO2.

Applying supervised intelligent scenarios to numerical investigate carbon dioxide capture using nanofluids

Nanofluids have recently been engaged in absorption-based processes to capture carbon dioxide (CO2) molecules. Pressure, temperature, nanoparticles type and dosage in host liquid, and gas-liquid contact time determine the CO2 absorption capacity of nanofluids. An accurate approach is required for the feasibility study, preliminary design, and optimization of any potential nanofluid-based process for CO2 removal. This study first constructs different artificial intelligent models and then compares their prediction performances to introduce the most reliable one. All models are developed and validated using 460 experimental datasets. The adaptive neuro-fuzzy (ANFIS) equipped with the Sugeno-type inference system (cluster radius = 0.5) is the most accurate model for the given purpose. The engineered ANFIS model simulates the absorption capacity of pure water and water-based nanofluids with the lowest uncertainty (i.e., AARD = 2.09%, MSE = 1.9 × 10−4, R = 0.99691). ANFIS predictions showed that the Fe3O4 nanoparticles enhance the CO2 absorption capacity of water more than the Al2O3, SiO2, and carbon nanotubes.

Regulatory mechanism of a novel non-aqueous absorbent for CO2 capture using 2-amino-2-methyl-1-propanol: Low viscosity and energy efficient

The large-scale deployment of non-aqueous amine solution for carbon dioxide (CO2) capture is mainly limited by its high viscosity, even insoluble substances in saturated solution, which may result in equipment fouling and pipeline blockage. To avoid this problem, the polyamine 1,5-diamino-2-methyl-pentane (DA2MP) was screened as the main absorbent to ensure the high absorption load. While 2-amino-2-methyl-1-propanol (AMP) was used as the regulator to reduce the viscosity and eliminate insoluble substances, which dissolved in n-propanol (PrOH) to from the novel non-aqueous absorbent for CO2 capture. The CO2 absorption load of the novel absorbent was 0.95 mol·mol−1, and the viscosity of saturated solution was only 15.00 mPa·s, remarkably lower than that of the solution without AMP regulation. The solution maintained 97% of its initial CO2 absorption capacity after fourth regeneration cycle. The regulation mechanism was investigated using 13C nuclear magnetic resonance (NMR) and quantum chemical calculations. It was proved that a strong and dense hydrogen bond network between DA2MP-carbamates was formed due to the self-deprotonation process, leading to insoluble products in the saturated DA2MP/PrOH solution. Through AMP regulation, there was another type of DA2MP-carbamates deprotonated by AMP formed in the solution with less hydrogen bond network, which could further react with PrOH to produce alkyl carbonates, achieving the elimination of insoluble products and reducing viscosity. Overall, the total regeneration energy consumption was 1.86 GJ·ton−1 CO2, only 50.27% of that of the benchmark monoethanolamine (MEA)-based solution, which would be a promising candidate for CO2 capture.

A simple multiple-amine heterogeneous composite for efficient conversion of CO2 to cyclic carbonates under atmospheric pressure

A novel process for efficient conversion of CO2 to cyclic carbonates under atmospheric pressure in the absence of solvents has been achieved by using cheap and readily available multiple-amine material (PS-PEI) as a catalyst. As a metal-free catalyst, PS-PEI showed excellent catalytic activity and CO2 absorption capacity. PS-PEI can participate in the cycloaddition of a variety of epoxides and CO2 with high yields. The structure and catalytic performance of this polymer material do not change significantly after being recycled four times. Based on the results of experiments and characterization, a possible mechanism was proposed, in which the collaboration of amine groups and chloride ion promotes the efficient activation of CO2 and epoxides. Moreover, the effect of various reaction parameters, temperature, catalyst dosage, and reaction time were investigated to optimize the reaction conditions.