The need for effective and adaptive technologies for carbon dioxide (CO2) mitigation targeting global net‐zero carbon emissions is critically growing. Hence, innovative technologies for CO2 reduction ...have attracted worldwide interest from scientific research communities. The use of liquid metals for the conversion of CO2 into carbon or solid carbonaceous products has gained increasing attention in recent years due to their high activity and resistance to coking. Here, a facile approach for the reduction of CO2 to solid carbon using liquid Mg at and near room temperature, and atmospheric pressure is presented. In this process, magnesium (Mg) plays a major role in driving the dissociation of CO2 to its elemental constituents, carbon and oxygen. During the reaction process, Mg ions dissolve in gallium (Ga) liquid metal alloy, diffuse to the gas–liquid interface, and reduce CO2 to carbon while undergoing an oxidation reaction. The electrochemical method ensures a sustainable cyclic process by reducing Mg and Ga ions back to their metallic counterpart. The use of liquid metal alloys for CO2 reduction reactions can enable to achieve CO2 capture and storage at room temperature, setting a new foundation for the future exploration of efficient CO2 mitigation issues.
This work demonstrates a low temperature CO2 conversion to solid products using Mg–Ga liquid metal alloy. Magnesium metal in liquid form diffuses to the interface of liquid alloy and preferentially reacts with CO2 forming carbonous material and oxides. Oxides including MgO are converted back to Mg using a novel biphasic electrolysis presenting a sustainable platform for CO2 capture and conversion.
The high energy demand of CO2 absorption–desorption technologies has significantly inhibited their industrial utilization and implementation of the Paris Climate Accord. Catalytic solvent ...regeneration is of considerable interest due to its low operating temperature and high energy efficiency. Of the catalysts available, heterogeneous catalysts have exhibited relatively poor performances and are hindered by other challenges, which have slowed their large-scale deployment. Herein, we report a facile and eco-friendly approach for synthesizing water-dispersible Fe3O4 nanocatalysts coated with a wide range of amino acids (12 representative molecules) in aqueous media. The acidic properties of water-dispersible nanocatalysts can be easily tuned by introducing different functional groups during the hydrothermal synthesis procedure. We demonstrate that the prepared nanocatalysts can be used in energy-efficient CO2 capture plants with ease-of-use, at very low concentrations (0.1 wt %) and with extra-high efficiencies (up to ∼75% energy reductions). They can be applied in a range of solutions, including amino acids (i.e., short-chain, long-chain, and cyclic) and amines (i.e., primary, tertiary, and primary-tertiary mixture). Considering the superiority of the presented water-dispersible nanocatalysts, this technology is expected to provide a new pathway for the development of energy-efficient CO2 capture technologies.
MIL-101(Cr), a class of metal-organic framework, is a potential candidate for CO2 capture applications because of its high capacity of adsorption and separation capability. However, the intrinsic ...microporous structure of this nanomaterial poses limitations on its adsorption kinetics. Techniques employed to enhance its adsorption kinetics often adversely impact its adsorption capacity at equilibrium. Herein, as a new approach, we prepared amine-functionalized FAC@MIL-101(Cr) composites with adjustable micro-mesoporous structure and tunable nitrogen content by embedding different ratios of amine-functionalized activated carbon throughout the framework of MIL-101(Cr). This led to a simultaneous improvement in both kinetics and adsorption capacity for CO2. The best adsorbent, FAC-6@MIL-101(Cr), has excellent textural properties with a high surface area (1763.1 m2.g−1), great pore volume (1.29 cm3.g−1), and suitable nitrogen content (4.7 wt%). The adsorption analysis revealed that the modification of MIL-101(Cr) improved its CO2 adsorption capacity from 3.21 to 5.27 mmol/g under standard conditions of 1 bar and 25 °C. Furthermore, the FAC-6@MIL-101(Cr) adsorbent demonstrated fast CO2 adsorption kinetics (three times more relative to the pure MIL-101(Cr)), high CO2/N2 selectivity, and remarkable cyclic stability. The results confirmed that hybridization enhanced the polarizability of FAC@MIL-101(Cr) samples, causing more robust CO2-adsorbent surface interactions. Simultaneously, the existence of mesopores in the structure facilitated the transport of CO2 into the interior pores, resulting in a more efficient contact of CO2 molecules with all of the amine sites and a faster adsorption rate as well as more efficient regeneration. According to density functional theory (DFT) calculations, hybridization process induces significant changes in composites’ electronic structure, enhancing their capacity to interact with CO2 molecules more effectively. On the other hand, DFT calculations confirm that N2 molecule is less activated on the FAC@MIL-101(Cr) as evidenced by calculated small adsorption energy and charge-transfer values.
•Anovel hybride of MIL-(Cr) with mesopore and amine function, enhanced CO2 adsorption capacity and kinetics.•With Addeding of FAC to MIL-101(Cr), tuning of textural properties were obtaind.•Amine site accesibilty with mespore cause 70% improvment in CO2 Adsorption.•Exceptional adsorption kinetics and cyclic stability were achieved due to mesoproe.
Aqueous solutions of tertiary amines are promising absorbents for CO2 capture, as they are typically characterized by a high absorption capacity, low heat of reaction, and low corrosivity. However, ...tertiary amines also exhibit very low kinetics of CO2 absorption, which has made them unattractive options for large-scale utilization. Here, a series of novel nanoporous carbonaceous promoters (NCPs) with different properties were synthesized, characterized, and used as rate promoters for CO2 absorption in aqueous N, N-diethylethanolamine (DEEA) solutions. To prepare a DEEA–NCP nanofluid, NCPs were dispersed into aqueous 3 mol·L−1 DEEA solution using ultrasonication. The results revealed that among microporous (GC) and mesoporous (GS) carbonaceous structures functionalized with ethylenediamine (EDA) and polyethyleneimine (PEI) molecules, the GC–EDA promoter exhibited the best performance. A comparison between DEEA–GC–EDA nanofluid and typical aqueous DEEA solutions highlighted that the GC-EDA promoter enhances the rate of CO2 absorption at 40 °C by 38.6% (36.8–50.7 kPa·min−1) and improves the equilibrium CO2 absorption capacity (15 kPa; 40 °C) by 13.2% (0.69–0.78 mol of CO2 per mole of DEEA). Moreover, the recyclability of DEEA–GC–EDA nanofluid was determined and a promotion mechanism is suggested. The outcomes demonstrate that NCP–GC–EDA in tertiary amines is a promising strategy to enhance the rate of CO2 absorption and facilitate their large-scale deployment.
The data presented in this paper are related to the published research article “Development of aqueous-based phase change amino acid solvents for energy-efficient CO2 capture: The role of ...antisolvent” 1. The raw and analyzed data include the equilibrium and kinetics of CO2 absorption, the density and concentration of different CO2-containing species at upper and lower liquid phases, and particle size distribution of solid particles precipitated during CO2 absorption of aqueous and aqueous-based amino acid solvents. In addition, the SEM images of solid precipitates at the end of CO2 absorption are presented. The detailed values of this phase change amino acid solvent are crucial for large-scale implementation of CO2 capture systems with phase change behavior.
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•A hybrid synthesis method was utilized to engineer the structural defects of M-CN.•Tunable textural properties were obtained for M-CN and DP-CN materials.•For the first time, the ...performance of CN materials for H2S adsorption was studied.•Exceptional CO2 and H2S adsorption capacities were acquired for DP-CN materials.
Carbon nitride (CN) materials with intrinsic high nitrogen content are potential candidates for acidic gas adsorption. However, these nanomaterials should be further treated to achieve tunable textural properties for ultra-high gas adsorption. Herein, we synthesized dual-pore carbon nitride materials (DP-CN) with a series of ethylenediamine to carbon tetrachloride ratios with different amounts of potassium hydroxide (KOH) as a chemical activator using nanosilica (SiO2) as a hard template to tune the physicochemical properties of the materials. The prepared DP-CN adsorbents had a large surface area (up to 2036.9 m2/g), great pore volume (up to 1.15 cm3/g), and high nitrogen content (10.6 to 15.1 wt%). The best DP-CN displayed ultra-high CO2 and H2S adsorption capacity at 1 bar (8.3 and 13.8 mmol/g, respectively), 10 bar (16.9 and 23.1 mmol/g, respectively), and 30 bar (22.9 mmol/g for CO2) at 25 °C, which was significantly higher than those of other pure mesoporous carbon nitrides (M-CN) and carbon-based adsorbents. Moreover, the best adsorbent exhibited good CO2/N2, CO2/CH4, H2S/N2, and H2S/CH4 selectivity, suitable heat of adsorption, and excellent cyclic stability. According to density functional theory calculations, H2S adsorbs more strongly than CO2 on carbon nitride surfaces, and the adsorption energies of CO2 and H2S are related to charge-transfer values from the surface to the adsorbed species. The results revealed that the exceptional textural properties and high nitrogen content of the materials could play the main role in the superior adsorption of CO2 and H2S. This generation of CN materials is expected to be practical for a various range of separation processes, catalysis, capacitors, and energy storage.
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•MIL-101(Cr) was synthesized in kilogram hydrothermal batch reactor.•Surface area of 3101 m2/g and pore volume of 1.50 cm3/g were obtained.•Powder material shaped by sodium alginate ...and CaCl2 through ionotropic gelation.•Performance of prepared adsorbent was investigated by breakthrough curves.•Hydrothermal stability were studied over consecutive adsorption/desorption cycles.
Recently, MIL-101(Cr) as a porous coordination polymer is of great interestin water adsorption due to its water stability and excellent water uptake capacity. However, its microcrystalline nature puts limitations on its practical applications. Therefore, achieving an efficient method to produce the desired shaped forms while preserving the intrinsic properties of the powder has been a challenge. In this study, the MIL-101(Cr) powder material was produced in >300 g quantities with an overall yield of around 65% and an average SBET = 3101 m2 g−1 and it was shaped into spherical beads with mean size of 2.1 ± 0.2 mm by using sodium alginate and calcium chloride solution through an ionotropic gelation technique. The water vapor adsorption and the breakthrough behavior of prepared adsorbent were investigated in comparison with commercial adsorbents. In addition, hydrothermal stability, optimized regeneration temperature and mechanical strength of the adsorbent beads were examined. The results showed that at 25 °C and 1 bar the shaped adsorbent affording of water uptake of 1.1 g/g at 75% relative humidity, which is 290, 250 and 350 % more than activated alumina, 13X and 3A molecular sieves, respectively. Furthermore, it showed a breakthrough time as high as that for activated alumina and 3A molecular sieve. The complete regeneration was achieved at as low as 80 °C and the adsorbent showed stable performance after 20 consecutive water adsorption/desorption cycles. The outcome of this study suggests the high potential of the ionotropic gelation to shape MIL-101(Cr) powder material into bead form and use in water adsorption applications.
•A sustainable hybrid technology for DAC proposed.•Combination of amino acids and dense hollow fiber membrane provide stable CO2 absorption.•Vacuum low-temperature regeneration is a viable approach ...for CO2.•Potassium glycinate (GlyK) selected as the most suitable solvent for DAC.
Direct air capture (DAC) of CO2 using liquid sorbent technology is gaining attention as a promising approach in tackling the looming climate crisis. Despite technical advancements, critical aspects such as contactor selection, energy efficiency, sustainability, and environmental compatibility still pose uncertainties. In this study, various green amino acid salts performances in a DAC system were explored using non-porous hollow fiber membrane contactors (HFMCs). Two DAC absorption and desorption apparatuses were developed. For the DAC-absorption unit, the thermodynamic and kinetic behavior of five types of aqueous amino acid salt solutions were evaluated in long-term operations. High absorption stability for most of the solutions in different solvent loadings (up to 80% CO2 solvent loaded) were observed and potassium glycinate (GlyK) was selected as the most suitable candidate for DAC. To enhance the CO2 separation efficiency, parametric analysis on air and solvent flow rates, solvent temperature and concentration were conducted using GlyK. Vacuum low-temperature desorption experiments were carried out with GlyK to evaluate the CO2 removal efficiency over a range of solvent temperatures and concentrations, CO2 loadings, vacuum pressures, and vacuum/sweep gas mode. The results successfully quantified the effect of each operational parameter under various conditions on CO2 removal in a DAC system. Finally, to investigate the impact of membrane characteristics on DAC absorption–desorption performance, a developed and validated model was used. Taken all together, hybrid technology of membrane modules and green amino acid salts is shown to be a viable pathway towards a sustainable DAC process.
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•The vapor–liquid equilibria and absorption kinetics of CO2 in GlyK are evaluated.•GlyK is identified as a viable solvent for use in direct air capture applications.•A model simulates ...the performance of GlyK in commercial scale HFMCs.•GlyK can remove up to 83 % of the CO2 in ambient air.•Solvent regeneration temperatures can be kept well below 100 °C.
Current direct air capture (DAC) technology is largely cost-prohibitive for large scale implementation due to the excessive energy required to operate a combined absorption–desorption cycle. As the desorption process consumes much of the supplied energy, there is a demand to find more sustainable sorbent materials that maintain high absorptive capacities yet can be regenerated at lower working temperatures. This work evaluates potassium glycinate (GlyK) as one such alternative absorbent. Through conducting vapor–liquid equilibria and wetted wall column kinetic studies, GlyK is found to have comparable working capacities and liquid mass transfer coefficients to those reported for the industrial standard, monoethanolamine (MEA), yet outperforms it with regards to its distinctly low regeneration temperature. To further understand how GlyK would perform in an industrial scale DAC system, an Aspen Custom Modeler® (ACM) model is developed that integrates the experimentally obtained equilibria and kinetic data with the performance characteristics of a gas-solvent hollow fiber membrane contactor (HFMC). Full-scale simulations show that via implementing a 20°–90 °C absorption–desorption cycle, GlyK can capture up to 83 % of the CO2 in atmospheric air and be 55 % regenerated within a single membrane contactor pass. As these low working temperatures vastly outperform the conventional ∼ 40°–140 °C temperature swing currently implemented in industrial CO2 processing, GlyK is concluded to be a viable and sustainable option for use within energy-efficient DAC technology whereby renewable heat sources can be used.
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