Liquid Amine Research Articles

Compartmental modeling of CO2 absorption in a rotating packed bed

Capturing carbon dioxide (CO2), i.e., the primary greenhouse gas that contributes to climate change, from CO2 containing gas mixtures in various industrial sectors, e.g., natural gas processing and treating refinery off-gases, is necessary. Rotating packed beds (RPBs) have shown great efficiency in CO2 capture from flue gases with an appreciable intensification in the absorber size compared to the conventional packed bed absorbers. Successful commercialization of an RPB technology requires a comprehensive understanding of its performance under various operating conditions, process configurations, and for different solvents. In this study, we presented a mathematical model describing the performance of an RPB absorber for CO2 capture by aqueous amine solutions. We established the compartmental model based on two plug-flow reactors for gas and liquid phases. We validated this model adopting two sets of experimental data from literature. We considered reaction rates of all compounds in the system in the model. We, subsequently, employed the validated model to highlight the potential parameters in enhancing the overall CO2 recovery by an RPB absorber. The developed model takes advantage of acquired knowledge and data from literature based on years of numerical studies on RPBs. We studied the effects of operating conditions, such as inlet gas and liquid flow rates, amine fraction, rotating speed, and inlet liquid and gas temperatures on the performance of an RPB by the validated model. Although we initially developed the model for the CO2-monoethanolamine (MEA) solvent, we also studied the effect of changing the solvent to methyl diethanolamine (MDEA) and piperazine (PZ) on the overall absorption performance of an RPB absorber. We further adopted the developed model as a design tool to assist us in replacing a pilot- and an industrial-scale packed bed absorber with corresponding single RPB absorbers.

Unraveling the mechanism and the role of hydrogen bonds in CO2 capture by diluent-free amine sorbents through a combination of experimental and theoretical methods

The utilization of water-lean and non-aqueous amine sorbents is regarded as an appealing approach to reduce the energy costs of CO2 capture via liquid sorbents. However, significant research is still needed to achieve the technological maturity required for industrial-scale implementation. Here, we present a detailed experimental and computational analysis at the molecular level of CO2 capture by dipropylamine (DPA) as a case study to deepen our understanding of the mechanisms governing CO2 absorption by liquid secondary amines that can be used without any additional diluent. CO2 uptake with pure DPA was investigated, and the species produced over time were determined by NMR and FT-IR spectroscopy. In particular, the NMR analysis revealed the formation of carbamic acid at high CO2/DPA ratios. A detailed DFT investigation explained the mechanism of the reaction revealing a dynamic evolution in product distribution as CO2 loading increases. At low CO2 loadings, adducts with at least four DPA molecules are formed, ultimately leading to the carbamate/ammonium ionic pair stabilized through H-bonding interactions with DPA moieties. Conversely, at higher CO2 levels some stabilizing DPA molecules of ionic pair are required for the CO2 activation, resulting in the formation of carbamic acid. A reasonable mechanism for the evolution of product distribution is provided, and the main steps of the mechanistic picture are depicted and commented on. The dependence of carbamate and carbamic acid on the availability of hydrogen bond donors and acceptors in solution is also highlighted.

Smartphone-based detection and discrimination of amine vapors by a single dye-adsorbed material

Smartphone-assisted analysis has become widely utilized for detecting various species in recent years. In such studies, multiple dyes should be employed to ensure selectivity and analyte discrimination. In our research, we have demonstrated the capability of a specially synthesized dye to selectively detect and discriminate liquid amine vapors. The developed material employs meso-toluene-α,β,α’,β’-tetrabromoBODIPY immobilized on a thin-layer chromatography plate, exhibiting structure-specific color changes in response to amine vapors. The hue values of these colors, observed under both ambient and UV light, enable discrimination even among closely related amine structures. A mobile application has also been developed for the rapid interpretation of test results.

From insoluble to processable: Aminic solvent dissolution of donor–acceptor conjugated network polymers for fabrication of photocatalytic thin film

Conjugated network polymers (CNPs) have gained considerable attention as heterogeneous photocatalysts, however, their limited solubility in solvents poses a significant challenge in employing CNPs for photoreactors. Herein, we report the chemical dissolution of CNPs in aminic solvents to enhance solution processability. The CNPs, synthesized via the Knoevenagel polycondensation, were dissolved into corresponding polymer inks, forming thin films on various substrates through mild heating. Residual functional groups on the CNP surface provided latent reactive sites for liquid amines, facilitating structural disentanglement and dissolution without hindering the π-conjugation. The resulting polymer films on FTO electrodes exhibited broader light absorbance and > 2-fold enhanced photoresponse compared to CNP powder films. Photocatalytic production of H2O2 using the large-area polymer film (254.4 cm2) demonstrated sustained activity with a production rate of 0.21 mM H2O2 h−1 over 14 h without sacrificial agents. These findings lay the groundwork for applying CNP photocatalysts in chemical, optical, and electronic applications.

Sulfato‐β‐cyclodextrin induced multivalent supramolecular directional aggregation of cyanovinylene derivatives for achieving reversible near‐infrared fluorescence

AbstractMolecular aggregation or supramolecular aggregation‐induced emission is one of the research hotspots in chemistry, biology, and materials. Herein, we report negatively charged sulfato‐β‐cyclodextrin (SCD) induced cyanovinylene derivatives (DPy‐6C) directional aggregation to form regular nanorods (DPy‐6C@SCD) through supramolecular multivalent interactions, not only achieves ultraviolet‐visible absorption redshifted from 453 to 521 nm but also displays near‐infrared (NIR) aggregation‐induced emission with a large spectral redshift of 135 nm. The DPy‐6C monomer presents random nanosheets with weak fluorescence but obtains regular aggregates after assembly with SCD through electrostatic interactions. In the presence of H+, the DPy‐6C@SCD can further aggregate into elliptical nanosheets without fluorescence changes due to the protonation of secondary amines. In contrast, the morphology of DPy‐6C@SCD becomes flexible and sticks together upon the addition of OH− with an emission blue shift of 72 nm and a 90‐fold intensity increase because of disrupting the stacking mode of aggregates, thereby achieving acid‐base regulated reversible fluorescence behaviors that cannot be realized by DPy‐6C monomer. The DPy‐6C@SCD can efficiently select the detection of volatile organic amines both in liquid and gas phases within 5 s at the nanomolar level. Taking advantage of RGB analysis and calculation formula application, the DPy‐6C@SCD has been successfully used to monitor various organic amines on a smartphone, accompanied by naked‐eye visible photoluminescence. Therefore, the present research provides an efficient directional aggregation method through supramolecular multivalent interactions, which not only realizes topological morphology transformation but also achieves reversible NIR luminescent molecular switch and high sensitivity organic amines fluorescent sensing devices.

Evaluating regeneration performance of amine functionalized solid sorbents for direct air CO2 capture using microwave

The urgent challenge of climate change, primarily driven by global warming and carbon dioxide (CO2) emission, necessitates innovative solutions for carbon capture. CO2 capture by liquid amine has many drawbacks. These processes require significant energy to regenerate the solvents, releasing the captured CO2 for storage or utilization, which leads to increased operational costs and can diminish the overall efficiency of carbon capture systems. Recent research explores new promising techniques by CO2 capture using highly efficient solid sorbents. This study then focuses on enhancing a porous alumina material with potassium carbonate (K2CO3) and monoethanolamine (MEA) to optimize CO2 capture capacity and regeneration performance. The developed sorbent was conducted in a fluidized bed reactor, showcasing its effectiveness in capturing CO2 from air. This adsorbent can be reused by applying with microwave radiation for sorbent regeneration, a cutting-edge approach that allows precise temperature control and reduces regeneration time. The electrical microwave power, regeneration time and %closing regeneration time were study variables in sorbent regeneration process. By harnessing microwave, this method not only improves efficiency but also enhances the sorbent's reusability. This innovative technique presents a significant step forward in advancing cost-effective and energy-efficient CO2 capture technologies, crucial for mitigating the impact of climate change.

Effect of Additives on CO2 Adsorption of Polyethylene Polyamine-Loaded MCM-41.

Organic amine-modified mesoporous carriers are considered potential CO2 sorbents, in which the CO2 adsorption performance was limited by the agglomeration and volatility of liquid amines. In this study, four additives of ether compounds were separately coimpregnated with polyethylene polyamine (PEPA) into MCM-41 to prepare the composite chemisorbents for CO2 adsorption. The textural pore properties, surface functional groups and elemental contents of N for MCM-41 before and after functionalization were characterized; the effects of the type and amount of additives, adsorption temperature and influent velocity on CO2 adsorption were investigated; the amine efficiency was calculated; and the adsorption kinetics and regeneration for the optimized sorbent were studied. For 40 wt.% PEPA-loaded MCM-41, the CO2 adsorption capacity and amine efficiency at 60 °C were 1.34 mmol/g and 0.18 mol CO2/mol N, when the influent velocity of the simulated flue gas was 30 mL/min, which reached 1.81 mmol/g and 0.23 mol CO2/mol N after coimpregnating 10 wt.% of 2-propoxyethanol (1E). The maximum adsorption capacity of 2.16 mmol/g appeared when the influent velocity of the simulated flue gas was 20 mL/min. In addition, the additive of 1E improved the regeneration and kinetics of PEPA-loaded MCM-41, and the CO2 adsorption process showed multiple adsorption routes.

Lignin-based porous carbon adsorbents for CO2 capture.

A major driver of global climate change is the rising concentration of atmospheric CO2, the mitigation of which requires the development of efficient and sustainable carbon capture technologies. Solid porous adsorbents have emerged as promising alternatives to liquid amine counterparts due to their potential to reduce regeneration costs. Among them, porous carbons stand out for their high surface area, tailorable pore structure, and exceptional thermal and mechanical properties, making them highly robust and efficient in cycling operations. Moreover, porous carbons can be synthesized from readily available organic (waste) streams, reducing costs and promoting circularity. Lignin, a renewable and abundant by-product of the forest products industry and emerging biorefineries, is a complex organic polymer with a high carbon content, making it a suitable precursor for carbon-based adsorbents. This review explores lignin's sources, structure, and thermal properties, as well as traditional and emerging methods for producing lignin-based porous adsorbents. We examine the physicochemical properties, CO2 adsorption mechanisms, and performance of lignin-derived materials. Additionally, the review highlights recent advances in lignin valorization and provides critical insights into optimizing the design of lignin-based adsorbents to enhance CO2 capture efficiency. Finally, it addresses the prospects and challenges in the field, emphasizing the significant role that lignin-derived materials could play in advancing sustainable carbon capture technologies and mitigating climate change.

Investigation of microgravity vortex phase separator for spacecraft liquid amine CO2 removal system

Spacecraft cabin atmosphere revitalization, more specifically CO2 removal, is a key technology to pursue long-duration, crewed space missions, such as the ones to the Moon and Mars. The ISS currently uses the Carbon Dioxide Removal Assembly (CDRA) as the primary system that employs solid sorbent (zeolite) to remove CO2 from cabin air. However, CDRA cannot meet high reliability and low maintenance requirements. Liquid sorbents may be used as an alternative to solid sorbents and are estimated to attain 65 % less power, weight, and volume than solid based CO2 scrubbers. Liquid amines (liquid sorbent) are currently being researched by NASA for CO2 capture, however their implementation for space applications depends on an effective gas-liquid separation method under microgravity conditions. The Vortex Phase Separator (VPS) offers a new approach for a liquid amine CO2 removal system, and initial investigation of the prototype VPS system demonstrated up to 90.3 % CO2 removal from a humid CO2 stream at 1.47 l/min flow rate. Tests were conducted to determine the CO2 removal efficiency considering several operating parameters, including the liquid amine flow rate, initial fill (charge) level, and temperature; CO2 flow rate; extended-time operation; and CO2-amine pre-mixing length. Results provided key insights on design, operation, and performance aspects of a subscale system, and demonstrated the feasibility of the microgravity VPS for liquid amine CO2 removal system as an alternative, novel spacecraft air revitalization approach.

Developing High-Capacity Solid "Molecular Basket" Sorbents for Selective CO2 Capture and Separation.

ConspectusSince carbon-based energy continues to dominate (over 80%) the global primary energy supply, carbon dioxide capture, utilization, and sequestration (CCUS) is deemed to be a promising and viable option to mitigate greenhouse gas emissions and climate change, for which CO2 capture is critical to the overall success of CCUS. Although liquid amine scrubbing is a mature technology for carbon capture, it is energy-intensive and costly due to energy consumption in solvent heating and water evaporation apart from the energy needed to break amine-CO2 bonding. To address this challenge, Song's group developed a new design approach for adsorptive CO2 capture and separation, namely, "molecular basket" sorbents (MBS), without the need for dealing with solvent heating and water evaporation. The solid MBS consisting of polymeric amines (such as PEI) immobilized into nanoporous materials (such as SBA-15) possesses a high capacity for CO2 capture with high selectivity, fast kinetics, and good regenerability. Consequently, MBS can greatly reduce energy consumption and carbon capture cost. Conventional adsorbents such as zeolites, activated carbon, alumina, and silica have low adsorption capacities, and their use of CO2 adsorption requires prior removal of moisture and cooling of flue gas (∼35 °C). On the contrast, the CO2 sorption capacity of MBS can even be promoted by the presence of moisture/steam and reaches the best performance closer to flue gas temperature (∼75 °C). This Account presents an overview of our research progress in the material development and fundamental understanding of MBS for CO2 capture and the separation of CO2 from various gas streams. It begins with an illustration of the MBS concept, followed by efforts to improve the performance and pilot-scale demonstration of MBS for CO2 capture. With the systematic characterization of MBS by various ex situ and in situ techniques, a better understanding is developed for the CO2 sorption process mechanistically. Furthermore, this Account demonstrates how the fundamental understanding of the CO2 sorption mechanism promotes the further development of more robust and advanced sorbent materials with improved CO2 sorption capacity, kinetics of sorption and desorption, and cyclic stability. Finally, an outlook is provided for the future design and development of novel sorbent materials and the CO2 sorption process for various gas streams including flue gas, biogas, air, and hydrogen streams.

Simplifying the Synthesis of Metal-Organic Frameworks.

Metal-organic frameworks (MOFs) are porous, crystalline materials constructed from organic linkers and inorganic nodes that have attracted widespread interest due to their permanent porosity and highly modular structures. However, the large volumes of organic solvents and additives, long reaction times, and specialized equipment typically required to synthesize MOFs hinder their widespread adoption in both academia and industry. Recently, our lab has developed several user-friendly methods for the gram-scale (1-100 g) preparation of MOFs. Herein, we summarize our progress in the development of high-concentration solvothermal, mechanochemical, and ionothermal syntheses of MOFs, as well as in minimizing the amount of modulators required to prepare highly crystalline Zr-MOFs. To begin, we detail our work elucidating key features of acid modulation in Zr-MOFs to improve upon current dilute solvothermal syntheses. Choosing an optimal modulator maximizes the crystallinity and porosity of Zr-MOFs while minimizing the quantity of modulator needed, reducing the waste associated with MOF synthesis. By evaluating a range of modulators, we identify the pKa, size, and structural similarity of the modulator to the linker as controlling factors in modulating ability. In the following section, we describe two high-concentration solvothermal methods for the synthesis of Zr-MOFs and demonstrate their generality among a range of frameworks. We also target the M2(dobdc) (M = Mg, Mn, Fe, Co, Ni, Cu, Zn, Cd; dobdc4- = 2,5-dioxido-1,4-benzenedicarboxylate) family of MOFs for high-concentration synthesis and introduce a two-step preparation of several variants that proceeds through a novel kinetic phase. The high-concentration methods we discuss produce MOFs on multi-gram scale with comparable properties to those prepared under traditional dilute solvothermal conditions. Next, to further curtail solvent waste and accelerate reaction times, we discuss the mechanochemical preparation of M2(dobdc) MOFs utilizing liquid amine additives in a planetary ball mill, which we also apply to the synthesis of two related salicylate frameworks. These samples exhibit comparable porosities to traditional dilute solvothermal samples but can be synthesized in just minutes, as opposed to days, and require under 1 mL of liquid additive to prepare ~0.5 g of material. In the following section, we discuss our efforts to avoid specialized equipment and eliminate solvent use entirely by employing ionothermal conditions to prepare a variety of azolate- and salicylate-based MOFs. Simply combining metal chloride (hydrate) salts with organic linkers at temperatures above the melting points of the salts affords high-quality framework materials. Further, ionothermal conditions enable the syntheses of two new Fe(III) M2(dobdc) derivatives that cannot be synthesized under normal solvothermal conditions. Last, as a demonstrative example, we discuss our efforts to synthesize 100 g of high-quality Mg2(dobdc) in a single batch using a high-concentration (1.0 M) hydrothermal synthesis. Our Account will be of significant interest to researchers aiming to prepare gram-scale quantities of MOFs for further study.

Amine Adsorbents Stability for Post-Combustion CO2 Capture: Determination and Validation of Laboratory Degradation Rates in a Multi-staged Fluidized Bed Pilot Plant.

Alternative to current liquid amine technologies for post-combustion CO2 capture, new technologies such as adsorbent-based processes are developed, wherein material lifetime and degradation is important. Herein a robust method to determine degradation rates in a laboratory setup is developed, which was validated with a continuous multi-staged fluidized bed pilot plant designed to capture 1 ton CO2 per day. An amine functionalized polystyrene adsorbent showed very good agreement between the experimental 1000-hour laboratory degradation rates and 2200 hours of degradation in a pilot plant. This validates how laboratory experiments can be extrapolated for sorbent screening and for scale-up. Resulting, the oxidative degradation in the desorber at high temperatures (120 °C) and low O2 concentrations (150 ppmv) is 3 times higher compared to the adsorber at low temperatures and high O2 (56 °C, 7 vol %). Laboratory degradation experiments can hence be used to further optimize process operations to limit degradation or screen for potential new adsorbents.

Theoretical design of a space bioprocessing system to produce recombinant proteins

Space-based biomanufacturing has the potential to improve the sustainability of deep space exploration. To advance biomanufacturing, bioprocessing systems need to be developed for space applications. Here, commercial technologies were assessed to design space bioprocessing systems to supply a liquid amine carbon dioxide scrubber with active carbonic anhydrase produced recombinantly. Design workflows encompassed biomass dewatering of 1 L Escherichia coli cultures through to recombinant protein purification. Non-crew time equivalent system mass (ESM) analyses had limited utility for selecting specific technologies. Instead, bioprocessing system designs focused on minimizing complexity and enabling system versatility. Three designs that differed in biomass dewatering and protein purification approaches had nearly equivalent ESM of 357–522 kg eq. Values from the system complexity metric (SCM), technology readiness level (TRL), integration readiness level (IRL), and degree of crew assistance metric identified a simpler, less costly, and easier to operate design for automated biomass dewatering, cell lysis, and protein affinity purification.

Dual Salt Cation-Swing Process for Electrochemical CO2 Separation.

Electrochemical CO2 separations, which use electricity rather than thermal energy to reverse sorption of CO2 from concentrated point sources or air, are emerging as compelling alternatives to conventional approaches given their isothermal, ambient operating conditions, and ability to integrate with renewable energy inputs. Despite several electrochemical approaches proposed in previous studies, further explorations of new electrochemical CO2 separation methods are crucial to widen choices for different emissions sources. Herein, we report an electrochemical cation-swing process that is able to reversibly modulate the CO2 loading on liquid amine sorbents in dimethyl sulfoxide (DMSO) solvent. The process exploits a reversible carbamic acid-to-carbamate conversion reaction that is induced by changing the identity of Lewis acid cations (e.g. K+, Li+, Ca2+, Mg2+, and Zn2+) coordinated to the amine-CO2 adduct in the electrolyte. Using ethoxyethylamine (EEA) as a model amine, we present NMR-based speciation studies of carbamic acid-to-carbamate conversion as a function of amine/salt concentrations and cation identity. The reaction is further probed using gas-flow reaction microcalorimetry, revealing the energetic driving forces between cations and the amine-CO2 adduct that play a key role in the described re-speciation. A prototype electrochemical cell was further constructed comprising a Prussian white (PW) potassium (K+) intercalation cathode, zinc (Zn) foil anode, and EEA/DMSO electrolyte containing a dual KTFSI/Zn(TFSI)2 salt. A low CO2 separation energy of ∼22-39 kJ/mol CO2 (0.1-0.5 mA cm-2) was achieved with a practical CO2 loading delta of ∼0.15 mol CO2/mol amine. Further optimizations in electrolyte design and cell architectures toward continuous CO2 capture-release are expected to enhance rate performance while retaining favorable separation energies.

Structure Investigation of La, Y, and Nd Complexes in Solvent Extraction Process with Liquid Phosphine Oxide, Phosphinic Acid, and Amine Extractants

The main challenge in separating REEs through hydrometallurgical processes is their chemical similarities. Despite the literature widely presenting the possibilities for organic extractants, there is a lack of evaluation of the structures formed between the REEs and the extractants. The present study aimed to evaluate different extractants (neutral, anionic, and acid extractants) for separating La, Y, and Nd. The extraction efficiencies were evaluated, and the structure investigation was carried out in FT-IR. From the results obtained, it is clear that the extraction order is Alamine 336 <<< Cyanex 272 < Cyanex 923, where both acid extractants were more selective for Y than for La and Nd. The extraction achieved 99% at pH 5.0 in nitric acid media, and a Y/La ratio of 2 and a Y/Nd ratio of 4 using Cyanex 923. The present study also elucidated the organometallic complexation between Cyanex 923 and Cyanex 272 with Y and La, which may improve separation processes to obtain critical metals from primary and secondary sources.

Carbon Capture Using Porous Silica Materials.

As the primary greenhouse gas, CO2 emission has noticeably increased over the past decades resulting in global warming and climate change. Surprisingly, anthropogenic activities have increased atmospheric CO2 by 50% in less than 200 years, causing more frequent and severe rainfall, snowstorms, flash floods, droughts, heat waves, and rising sea levels in recent times. Hence, reducing the excess CO2 in the atmosphere is imperative to keep the global average temperature rise below 2 °C. Among many CO2 mitigation approaches, CO2 capture using porous materials is considered one of the most promising technologies. Porous solid materials such as carbons, silica, zeolites, hollow fibers, and alumina have been widely investigated in CO2 capture technologies. Interestingly, porous silica-based materials have recently emerged as excellent candidates for CO2 capture technologies due to their unique properties, including high surface area, pore volume, easy surface functionalization, excellent thermal, and mechanical stability, and low cost. Therefore, this review comprehensively covers major CO2 capture processes and their pros and cons, selecting a suitable sorbent, use of liquid amines, and highlights the recent progress of various porous silica materials, including amine-functionalized silica, their reaction mechanisms and synthesis processes. Moreover, CO2 adsorption capacities, gas selectivity, reusability, current challenges, and future directions of porous silica materials have also been discussed.

Insight into the application of amino acid-functionalized MIL-101(Cr) micro fluids for high-efficiency CO2 absorption: Effect of amine number and surface area

Today, the combination of liquid absorbents and different additives like nano/micro particles (NPs, MPs) and amines for carbon dioxide (CO2) absorption has significantly increased. In this work, as a new approach, by considering the outstanding benefits of metal organic framework (MOF) structures, MIL-101(Cr)-CH2-Glycine (MIL-101(Cr)-Glycine), MIL-101(Cr)-CH2-Histidine (MIL-101(Cr)-Histidine) and MIL-101(Cr)-CH2-Arginine (MIL-101(Cr)-Arginine) with different amine numbers (1 to 4) are synthesized and subsequently, employed as an additive for the CO2 absorption improvement of pure water in a batch mode. To evaluate the efficiency of the applied MOFs, the impact of varying operating parameters including pressure, MOF concentration, MOF stability in the liquid phase and amine number are examined. According to the obtained results, applying all amino acid-functionalized MOFs causes a better performance in CO2 absorption compared to bare MIL-101 due to chemical reactions of amino groups with CO2 and formation of carbamate during the absorption experiment. Ultimately, MIL-101(Cr)-Arginine micro fluid results in the highest CO2 absorption enhancement because of its four amine number and raises the CO2 absorption up to 39% compared to pure water as a base fluid.

Review on CO2 Capture Using Amine-Functionalized Materials.

CO2 capture from industry sectors or directly from the atmosphere is drawing much attention on a global scale because of the drastic changes in the climate and ecosystem which pose a potential threat to human health and life on Earth. In the past decades, CO2 capture technology relied on classical liquid amine scrubbing. Due to its high energy consumption and corrosive property, CO2 capture using solid materials has recently come under the spotlight. A variety of porous solid materials were reported such as zeolites and metal-organic frameworks. However, amine-functionalized porous materials outperform all others in terms of CO2 adsorption capacity and regeneration efficiency. This review provides a brief overview of CO2 capture by various amines and mechanistic aspects for newcomers entering into this field. This review also covers a state-of-the-art regeneration method, visible/UV light-triggered CO2 desorption at room temperature. In the last section, the current issues and future perspectives are summarized.

Critical Review on Carbon-Based Nanomaterial for Carbon Capture: Technical Challenges, Opportunities, and Future Perspectives

In the 21st century, climate change and global warming are considered to be one of the world’s most severe and biggest environmental threats to humans. Consequently, the CO2 capture and storage technique has been a concern as a superior technique by both industrial and academic research communities, which prohibits the mixing of CO2 from point sources, such as cement plants and fossil fuel power plants, into the atmosphere. Particularly, after the United Nations Climate Change Conference in 2015, which was held in Paris, France, researchers have been vigorously focusing on the reduction of greenhouse gases. Presently, liquid amine scrubbing has been used for CO2 capture technology, while solid sorbents are used for CO2 capture technology to overcome the drawbacks associated with amine scrubbing technology. In this review, different carbon nanomaterials, such as fullerene, carbon nanotubes, graphene oxide, biochar, and activated carbon, and their derivatives for CO2 capture applications are summarized. In addition, the review covers the fundamental requirements of solid sorbents, advantages and disadvantages of other solid sorbents, and policies proposed for reducing greenhouse gas emissions by developing and developed countries, which will be highly beneficial for making future policies and fabricating low-cost CO2 sorbents. Finally, the current technical challenges and opportunities for the development of efficient and practically possible carbon-based CO2 sorbents were discussed. Furthermore, future perspectives were proposed for the development of carbonaceous porous materials in place of existing liquid amine scrubbing technology in the future.

Hydrogen-powered Electrochemically-driven CO2 Removal from Air Containing 400 to 5000 ppm CO2

The performance of a hydrogen-powered, electrochemically-driven CO2 separator (EDCS) was demonstrated at cathode inlet CO2 concentrations from 400 ppm to 5,000 ppm. The impact of current density and CO2 concentration were evaluated to predict operating windows for various applications. The single-cell data was used to scale a 100 cm2, multi-cell stack using a shorted-membrane design for four applications: direct air capture (DAC), hydroxide exchange membrane fuel cell (HEMFC) air pretreatment, submarine life support, and space habitation. For DAC, a 339-cell EDCS stack (7.7 L, 17 kg) was projected to remove 1 tonne CO2 per year. The addition of the EDCS in HEMFC systems would result in nearly a 30% increase in volume, and therefore further improvements in performance would be necessary. A module containing five 338-cell EDCS stacks (38 L, 85 kg) in parallel can support a 150 person crew at 2.1% of the volume of the liquid amine system employed in submarines. For space habitation, a 109-cell EDCS stack (3.2 L, 10 kg) is adequate for 6 crewmembers, and is less than 1% the size and 5% the weight of the current CO2 removal system installed on the International Space Station.