Amine Adsorbents Research Articles

Molecule‐level Design to Form Pocket Structures for Improving Amine Efficiency in CO2 Capture

AbstractSolid amine adsorbents represent a promising class of CO2 sorbents, but their amine efficiency is limited by the inaccessibility of peripheral amines. The surface of mesocellular silica foam (MCF) is functionalized with the mixture of short‐chain 3‐Glycidyloxypropyl) triethoxysilane (GPTES) and long‐chain Octadecyltrimethoxysilane (OTMS), forming pocket structures on the support surface, thereby exposing more amine sites and enhancing the amine efficiency of polyethylenimine (PEI). The resulting adsorbent demonstrates a high CO2 adsorption capacity (5.02 mmol g−1 at 50 °C, 10 vol.% CO2, and 50%RH), high amine efficiency (0.43 at the dry condition), outstanding cyclic stability (0.5% performance decline per cycle under the conditions of dry CO2 regeneration), and fast adsorption kinetics (15 min for adsorption saturation at 50 °C). First‐principles calculations and CO2 temperature‐programmed desorption (TPD) experiments demonstrate that the introduction of GPTES and OTMS is beneficial to decreasing adsorption energy and forming paired carbamic acid states and ammonium carbamate states.

Hierarchically fibrillated spunlaced nonwovens from waste wool supported ionic liquid as solid amine adsorbents for CO2 capture

The environmental crisis caused by excessive emissions of carbon dioxide-based greenhouse gases has garnered widespread public concern. Solid amine is considered to be one of the most effective carbon dioxide (CO2) adsorbents. However, traditional solid amine carriers have problems such as structural collapse, low efficiency and poor regeneration. In this study, waste wool having hierarchical fibrous structure was spunlaced, fibrillated and later compounded with amino acid ionic liquids (AAIL) leading to the formation of the AAIL@feather-like wool nonwoven absorbents. A synergistic co-amine effect was observed after primary and secondary fibrillation without any sacrifice in the mechanical property of wool nonwovens. Also, the fibrillated nonwovens had high specific area which provided high loading rate (13.53 %) on AAIL. Compared with untreated wool nonwovens, the CO2 adsorption capacity of feather-like wool nonwovens was higher by 65 % (11.75 mmol/g) after loading AAIL. Furthermore, the CO2 adsorption capacity was retained (95.2 %) even after 12 cycles at 80 ℃, indicating that the AAIL@ feather-like wool nonwovens possess good long-term stability. This work paves the way for large scale manufacturing of biobased solid adsorbents with a hierarchical nonwoven structure for efficient CO2 capture.

Analysis on temperature vacuum swing adsorption from wet flue gas carbon capture by using solid amine adsorbent with co-adsorption equilibrium models

Adsorption carbon capture has attracted extensive attention due to its low regeneration heat consumption, eco-friendly impacts and simplicity. However, there is a lack of comprehensive analysis of its energy consumption, economy and environment impact of adsorption carbon capture. This study aims to investigate the working performance using temperature vacuum swing adsorption (TVSA) from wet flue gas carbon capture utilizing co-adsorption equilibrium models for metal–organic framework (MOF) based amine materials. TVSA model is then carried out in terms of the continuous operational state, the dynamic changes in physical properties inside the bed, and the differences in properties at different positions within the bed layer. It is found that they often cannot simultaneously meet high CO2 recovery rates, productivity, and equivalent work. The analysis reveals that the optimal conditions, namely an adsorption temperature of 318 K and a CO2 component of 0.02 kmol during desorption, collectively result in reduced equivalent work and heightened productivity. The maximum productivity could reach 46.35 kg·m−3·h−1 for 5.6 v% water content and 308 K adsorption temperature. It is demonstrated that temperature vacuum swing adsorption for wet flue gas carbon capture using MOF based amine adsorbent is quite promising in terms of energy consumption and CO2 productivity in the future.

Solid amine adsorbent with surfactant modification for Direct Air Capture (DAC) under different temperature and humidity conditions

Direct air capture (DAC) technologies have been vigorously pursued to achieve the goal of net-zero CO2 emissions due to the dramatic increase in atmosphere CO2 concentrations and global temperatures. In practical DAC conditions, variations in temperature and humidity can lead to different CO2 adsorption outcomes. Current studies lack comprehensive information on the optimal temperature and humidity conditions for DAC. In this study, a comparison between PMSU-F (impregnating polyethyleneimine (PEI600) on MSU-F support) and PPMSU-F (co-impregnating polyethylene glycol (PEG200) with PEI600 on MSU-F support) under different temperature and relative humidity conditions were conducted. Under dry conditions, the addition of PEG200 effectively enhanced the adsorption capacity, adsorption rate, and amine efficiency and decreased the energy consumption for desorption depending on the comparison of the two absorbents. Under the popular atmospheric temperature ranges (−5 °C–45 °C), an increase in temperature favors CO2 adsorption. Under humid conditions, the presence of PEG200 had a negative effect due to its strong hydrophilicity. By comparing dry and humid conditions, the introduction of moisture generally enhanced overall CO2 adsorption performance, and the adsorption capacity interestingly further increased under low-temperature conditions. The highest CO2 adsorbing capacity of PMSU-F (3.82 mmol/g) and PPMSU-F (3.76 mmol/g) appeared at −5 °C and 75% relative humidity, indicating that low temperature and relatively high relative humidity were more favorable for DAC, which is possibly attributed to the thermodynamic control under low temperatures with moisture. The results indicate that the adsorbents chosen in this study are promising for DAC under low temperatures and relatively high humidity conditions. The performances of modified DAC adsorbents, e.g., adsorption capacity, stability, antioxidant property for industrial-grade DAC system should be evaluated in the next work.

Amine-impregnated cellulose aerogels prepared from old corrugated containers: Microstructure characterization and CO2 capture performance

Here, five different amines (MEA, DETA, TEPA, PEI, and PEPA) were immobilized onto a mesoporous cellulose aerogels (CAs) support prepared from old corrugated containers (OCCs) using the impregnation method, and the thermal stabilities, pore structures, and CO2 adsorption capacities of the resulting amine loaded materials were investigated. The results showed that the thermal stabilities and pore textures of the materials decreased relative to the unmodified CAs support. Additionally, the addition of high molecular weight amines improved the thermal stability of the resulting materials, in the order of PEI>PEPA>TEPA>DETA>MEA. The adsorption capacities of the five Amine40@CAs materials tested ranged from 111.76 to 62.48 mg.g−1 and were in the order of DETA>PEI>MEA>TEPA>PEPA. Considering both thermal stability and CO2 adsorption capacity, PEI is the most suitable for physical immobilization in the CAs support. Consequently, the sample loaded with 30 % PEI exhibits a maximum CO2 capture capacity of 136.84 mg.g−1 material. However, a loading above 30 % results in pore blockage due to amine infiltration into the pore structure, leading to a decrease in the specific surface area and hence the CO2 adsorption capacity. This indicates that there is a balance to be struck between amine loading and CO2 uptake in the solid amine adsorbents using the physical impregnation method, and it is necessary to choose an appropriate method for improving the pore structure in order to maximize the amine loading and thus enhance the CO2 capture capacity.

Amine/vermiculite composite aerogels fabricated by polyethyleneimine-induced vermiculite nanosheet gelation for efficient direct air capture

Direct air capture (DAC), being able to remove the accumulated CO2 in atmosphere and CO2 carbon emission from discrete sources, is a promising technology for mitigating the global greenhouse effect and achieving carbon neutrality. However, achieving high-capacity, low-cost DAC of CO2 through simple methods remains a significant challenge. In this study, a simple, cost-effective, and environmentally friendly method for fabricating amine/vermiculite composite aerogels is proposed for capturing CO2 from ambient air. Natural two-dimensional material, vermiculite nanosheets with exposed surface and intrinsic negative charge, was utilized as the the building blocks for fabricating aerogel as solid amine adsorbents, via the fast gelatin between vermiculite and amine, significantly reducing the cost of adsorbent preparation while achieving promising CO2 capture capability. The effects of amine loading, amine molecular weight, and porosity on CO2 capture capacity and amine efficiency were investigated. It is found that the amine with larger molecular weights endows more stable amine anchoring in the composite aerogel, the aerogels using amine with higher molecular weights demonstrated higher residual amine ratios under vacuum conditions during the aerogel adsorbent synthesis, consequently enhancing the CO2 capture capacity of the adsorbents. By optimizing synthesis strategy and the amine loading of the composite aerogels, the highest CO2 capture capacity (0.72 mmol/g) and amine efficiency (0.29) were achieved. The monolithic structure of the aerogels ensures low pressure drop of 0.35 hPa during gas flow-through, enhancing their integration and applicability in adsorption devices. The vermiculite-based adsorbents exhibit unique advantages in practical DAC processes, including lower cost, higher amine efficiency, and stable cyclic performance. These findings hold significant promise for the application and advancement of DAC technologies.

Exceptional indoor carbon capture using epoxide-modified polyamine functionalized materials

In addressing concerns related to symptoms like dizziness, nausea, and reduced productivity stemming from elevated indoor CO2 levels, the primary objective of the current CO2 adsorption technology is to enhance the adsorption capacity. However, the stability and applicability of the adsorbent are of greater importance in indoor carbon capture than in other settings. This study examines the performance and stability of indoor CO2 capture using propylene oxide-modified tetraethylenepentamine supported on novel super carbon, gas-phase hydrophilic silica dioxide, and graphitic phase carbon nitride carriers. The corresponding painted films were developed to facilitate the application in indoor CO2 capture. Thermogravimetric analysis demonstrates that the propylene oxide-modified materials are more stable than the unmodified compositions. The findings indicate that an optimal adsorption capacity is achieved when water is used as the solvent and carboxymethyl cellulose sodium as a dispersant, while maintaining a carrier-to-tetraethylenepentamine mass ratio of 1:0.75. Furthermore, the painted films are stably formed by using isopropanol instead of water, and the tetraethylenepentamine-to-propylene oxide molar ratio of 1:2 for super carbon and graphitic phase carbon nitride as carriers, which exhibit notable enhancements in adsorption performance by 160.0 % and 41.8 %, respectively. The film using super carbon as supporter exhibited the highest adsorption capacity of 122.83 mg/g. This suggests that the compositions are more readily available for indoor CO2 capture by coating in everyday scenarios. Notably, even after undergoing five adsorption–desorption cycles, the desorption efficiency of the solid amine adsorbent remains consistently above 95 %.

Design of blend-amine solid adsorbents for CO2 capture: Enhances adsorption- equilibrium cycle strategies and mechanism

Blend amine-functionalized absorbents show great potential in the field of amine scrubbing for CO2, as they harness the absorption benefits of various monomer amines in combination. However, there is a lack of research on the application of the emerging concept of blend amines to solid amine adsorbents. Building upon this foundation, this study firstly incorporated Aminoethylethanolamine (AEEA) into Polyethyleneimine (PEI) of varying molecular weights to create a range of new binary solid amine adsorbents. The research then compared the adsorption performance differences between these binary adsorbents and pure PEI adsorbents. The enhanced dispersion of PEI by AEEA results in an increase in the effective active sites available. The amine efficiency and CO2 adsorption capacity of the AEEA-PEI blend amine system were maximally increased by 92.0% and 84.6%, respectively, compared to the pure PEI system. Furthermore, through DFT calculations, it is clear that the presence of AEEA lowers the overall activation energy of the reaction due to its superior proton acceptance compared to PEI. However, the AEEA-PEI system exhibits weak cycling stability attributed to the limited regeneration capacity of AEEA. Fortunately, this issue can be successfully addressed by introducing a strong base, N,N,N',N'',N''-pentamethyl diethylenetriamine (PMDETA). The CO2 adsorption cycling stability for AEEA-PEI-PMDETA system maximally improved by up to 17.1% compared to the AEEA-PEI system. The mechanism behind the effectively suppression of cycling losses by PMDETA was further elucidated through DFT calculations. Consequently, the novel ternary amine solid adsorbent introduced in this study, aimed at enhancing the CO2 adsorption performance of monomer amine solid adsorbents, offers a fresh strategy for fundamental theoretical investigations into CO2 adsorption.

Enhanced adsorption of trace carbon dioxide from acetylene using Polyethyleneimine-Diethanolamine blends

The removal of trace carbon dioxide (CO2) from acetylene (C2H2) through adsorption poses a significant challenge due to their similar kinetic diameters and physical properties. Here, we report a novel solid amine adsorbent, polyethyleneimine-diethanolamine functionalized silica dioxide (termed P/D-SD), which exhibited a remarkable CO2 adsorption capacity of 1.76 mmol/g at 298 K and 0.0004 bar. The IAST selectivity of the CO2/C2H2 (1/99, v/v) mixture of P/D-SD was 7.98E + 05. The exceptional separation performance of P/D-SD is demonstrated through breakthrough experiments, producing ultra-high purity C2H2 (greater than 99.9 %) from CO2/C2H2 (1/99) mixtures. Its CO2 adsorption performance remains largely unaffected under different humidity condition. Furthermore, P/D-SD exhibited excellent stability in the adsorption–desorption cycle and rapid CO2 adsorption kinetics at different temperatures when compared with P-SD. The adsorption mechanism of P/D-SD with CO2 was studied as a chemisorption process via in situ DRIFTS.

Amine-impregnated natural inorganic nanotubes via layer-by-layer electrostatically self-assembly approach for efficient CO2 adsorption

Developing cost-effective and high-performance solid amine adsorbents has considered as an important way to alleviate the greenhouse effect. How to precisely regulate its pore structure and surface interface characteristics, and how to cooperate to optimize the dynamic mass transfer and adsorption–desorption behavior of gas in the adsorbent are still challenging work. Herein, we demonstrated a facile and efficient approach to construct polyethyleneimine (PEI) impregnated halloysite nanotubes (HNTs) as an emerging nanocomposite for CO2 capture. Based on the natural electrostatic differences of inner and outer walls for HNTs, the hollow tubular structures of adsorbents were constructed by selective surface modification and layer-by-layer electrostatic self-assembly technology to improve the CO2 uptake capacity and cyclic stability, in which poly(sodium-p-styrene sulfonate) (PSS) and PEI were used as polyanionic and polycationic layer, respectively, to coat the inner walls of HNTs. The loading capacity of PSS-PEI composite ionic layers in HNTs and the influence of PSS polyanionic layer on PEI dispersion were specifically discussed according to the CO2 uptake capacity, adsorption heat, thermodynamics and kinetics of the adsorbents. The optimal PEI20-0.5PHNTs adsorbent exhibited a higher CO2 uptake of 0.87 mmol/g at 80 °C in the flow of 40 vol% N2/60 vol% CO2 than that of PEI20-HNTs, owing to the high amine efficiency due to the uniform dispersion of PEI in the electrostatic composite ionic layers. Furthermore, PEI20-0.5PHNTs reached 75 % of the maximum adsorption capacity at the 5th min of the adsorption process and released the most heat during adsorption at − 18.28 kJ/mol due to the presence of electrostatic composite ionic layers. PEI20-0.5PHNTs showed excellent cyclic stability with a slight loss of 7.4 %. The electrostatic self-assembled adsorbent obtained by layer-by-layer loading of PSS and PEI based on the unique surface charge characteristics of HNTs is an inspiration for the synthesis of cost-effective solid amine adsorbents for practical CO2 capture and separation.

Mild preparation of structured solid amine adsorbent pellets with the assistance of alginate for efficient and stable CO2 adsorption

The industrialization of solid amine adsorbents requires the molding of the adsorbents, and the blockage or collapse of the pore structure caused by the molding process will inevitably affect the CO2 adsorption performance. Herein, the structured solid amine adsorbent pellets (SA-T/M) were fabricated based on the crosslinking of alginate and Ca2+ under mild conditions. The pelletized SA-T/M well preserved the pore structure of the original support, with only a 26.8 % diminution in specific surface area, which profited to a more uniform loading and dispersion of amine. Benefitting from the influence of pore structure on amine dispersion, SA-T/M achieved a pretty CO2 adsorption capacity of 2.49 mmol g−1. The hydroxyl group of alginates can form hydrogen bonds with the amines, which greatly improved the amine stability of the adsorbent and enabled SA-T/M to exhibit excellent cyclic stability. After 30 adsorption-desorption cycles, the adsorption capacity of SA-T/M merely decreased by 15.6 %. Considering the adsorption capacity and stability of structured adsorbents, the molding strategy with the assistance of alginate provides a potential path for the industrial application of solid amine adsorbent molding technique.

Ultra-highly efficient adsorbent for CO2 capture from air by directional deprotonation regulation of MOFs-based amine grafting

In recent years, the solid amine of Metal-Organic Frameworks (MOFs) has shown promise as a direct air capture (DAC) adsorbent. However, the efficiency of amine groups under ultra-low CO2 concentrations requires improvement. In this study, we propose a novel method to regulate proton migration through solvent effects during amine grafting, to enhance the synthesis of MOFs as solid amine adsorbents and improve amine group utilization. This approach yielded outstanding results with a MIL-100(Cr)-based DAC adsorbent, demonstrating a CO2 adsorption capacity of 2.15 mmol/g and an ultra-high amine group utilization of 89.6 % at ambient conditions. By directional deprotonation regulation, the CO2 adsorption performance of the UiO-66(Zr)-based adsorbent significantly increased from 0.06 mmol/g of using H2O as solvent to 1.71 mmol/g of using NMP, with a 27.5-fold increase. Specifically, organic polar aprotic solvents enhanced the binding energy and reduced the energy barrier for deprotonation during the grafting process, thereby improving CO2 adsorption performance and amine group utilization, which shed a new light on the development of MOFs based CO2 adsorbent. Furthermore, due to the coordination of secondary amine groups with metal sites leads to the decrease of hydrophilic functional groups in the CO2 adsorption products, the hydrophobicity of products was reduced significantly resulting in an increase in the ΔS of the hydrated ion pairs after the adsorption, which reduced the heat of CO2 adsorption about 15 % than that reported in the literature. Based on changes in humidity conditions, the regeneration energy consumption of the MF-Cr-AEEA is less than 2.5 GJ/t CO2 under a relatively lower humidity, demonstrating outstanding industrial applications potential of the adsorbent.

Process design and adsorbent screening of VSA and exchanger type VTSA for flue gas CO2 capture

Carbon capture, as a core technology for mitigating greenhouse gas emissions, the greatest challenge is the balance between separation performance and energy consumption. This study seeks to evaluate and screen the separation performance and energy consumption of four typical adsorbents (13X, Mg-MOF-74, activated carbon, and Lewatit VP OV 1065) in vacuum temperature swing adsorption (VTSA) and vacuum swing adsorption (VSA) through optimization approach, which will support in-depth research and decision-making on adsorption processes. A non-isothermal non-adiabatic numerical model was carried out to describe a novel 4-bed 10-step VTSA cycle developed on an exchange type adsorption unit (ETAU), and the model was validated by binary breakthrough and temperature swing experiments. A 4-bed 10-step VSA cycle was in turn established and investigated. Parametric analysis of the two cycles was performed by varying the operating variables including feed gas flow rate, recycle time, and purge-to-feed ratio. Process optimization of the multiplicative fraction evaluation function, simultaneously considering purity, recovery, and productivity, was achieved using a dual convergence algorithm. Results showed that all four adsorbents could achieve more than 90 % purity and recovery on the VTSA process employing the ETAU for post-combustion carbon capture, and the separation performance was substantially superior to that of the VSA cycle. Mg-MOF-74 obtained a CO2 product with 97.90 % purity, 98.48 % recovery, and 5.48 mol/kgads/hr productivity at a desorption temperature of 383.15 K; it has a specific heat consumption of 1.45 GJth/ton and a specific power consumption of 0.55 GJel/ton. The total energy consumption of 13X was slightly lower than that of amine adsorbents, giving 95.00 % purity, 97.60 % recovery, and 1.91 mol/kgads/hr productivity. Relatively low desorption temperature is expected to introduce ultra-low-grade waste heat for partial heat source substitution, contributing to the energy sustainability of adsorption carbon capture technology.

Alginate-derived solid-liquid hybrid structured adsorbent for CO2 capture

The development of highly stable structured solid amine adsorbent is crucial for the large-scale deployment of CO2 capture systems. Here, we report a structured solid amine adsorbent using the solid-liquid hybrid wrapping method, wherein a suspension of tetraethylenepentamine (TEPA) and ZSM-22 support is encapsulated within a calcium alginate film through freeze-drying. The textural properties of the structured adsorbents (SA@S/TX) were investigated using scanning electron microscopy, N2 adsorption-desorption, Fourier transform infrared spectroscopy, and thermal gravimetric analyzer. The CO2 adsorption capacity of SA@S/TX displayed an initial increase followed by a decrease with increasing TEPA loading, and the adsorption rate exhibited a similar trend according to the pseudo-first-order model. The maximum adsorption capacity and adsorption rate (k) were observed to be 2.22 mmol/g and 0.98 min−1 (under conditions of pure CO2, 1 atm and 25 °C), respectively, at a TEPA content of 0.5. In addition, SA@S/TX exhibited good regeneration stability with a low loss in capacity of 10.8 % during 30 cycle of CO2 adsorption–desorption tests, and high thermal stability with a low amine loss of 2.0 % under conditions of 100 °C and 12 h. These results demonstrate that the solid–liquid hybrid wrapping method effectively shapes the powdered adsorbent while significantly reducing TEPA volatilization, offering a possibility for the industrial applications of solid amine adsorbents.

Facile and efficient amine@AD-SiO2 adsorbents from coal fly ash: Comparison of various amines for CO2 adsorption capacity and cyclic stability

Solid amine adsorbent is recognized as an efficient CO2 capture route for globe climate change mitigation. The pore structure of nano supports generally plays a crucial role in the CO2 adsorption performance of solid amine adsorbents; however, the involving of costly and toxic pore-expanding agents limited their scalable application. Herein, an azeotropic-distillation nano-SiO2 (AD-SiO2) support was recycled from coal fly ash (CFA) using the CO2-assisted precipitation and n-butanol AD methods, and possessed a super pore volume of 2.52 cm3·g−1 and an average pore size of 36.6 nm. After impregnating the triethyltetramine, tetraethylenepentamine, pentaethylenehexamine (PEHA), or polyethyleneimine, the synthesized amine@AD-SiO2 adsorbents achieved the excellent adsorption capacity of 3.50–6.13 mmol·g−1 and the fast adsorption kinetics, owing to the superior pore structure of AD-SiO2 support. Based on the viscosity, TGA and liquid-NMR characterization, we explained that the large amine molecule would block the CO2 diffusion channel and thus restrict the active sites, while the small amine molecule would evaporate during the regeneration process. Inspiringly, the PEHA@AD-SiO2 adsorbent possessed the excellent cyclic stability with merely 0.18 % decay per cycle and achieved a final CO2 uptake of 4.24 mmol·g−1 over 50 cycles. This study notably improved the long-term adsorption capacity of solid amine adsorbents via the pore-expanded AD-SiO2 support from CFA, thereby is a low-carbon technology for large-scale industrial CO2 capture.

Experimental testing and mechanism investigation of amine-functionalized layered vermiculite for CO2 capture

Solid amine adsorbents have attracted significant attention due to their low energy consumption, high selectivity, and environmental friendliness, positioning them as the most promising technology for CO2 capture. However, current adsorbent carrier materials commonly encounter challenges such as expensive costs and inadequate stability. In this study, acid-activated expanded vermiculite carrier (AEV) with a large pore volume and hierarchical pore structure was prepared. Subsequently, a series of functionalized polyethyleneimine (PEI) adsorbents were synthesized and employed in CO2 capture experiments to investigate the impact of PEI loading and temperature on adsorption characteristics. The results showed that the acid-modified expanded vermiculite with a large pore volume structure significantly increased amine loading, while the layered structure network promoted amine dispersion. Under the conditions of 50 wt% PEI loading, the CO2 capture capacity of AEV reached 3.29 mmol/L at 75 ℃. Furthermore, density functional theory was utilized to calculate the adsorption energy and Gibbs free energy change of CO2 and polyethyleneimine molecules. The HOMO and LUMO distributions of CO2 molecules with different polyethyleneimine chains were determined using frontier orbital theory, combined with infrared spectroscopy results confirming the conversion of CO2 into carbamate. Additionally, AEV-PEI50 adsorbent exhibited good stability during 8 cycles of the adsorption process. The obtained results demonstrate that the utilization of layered mesoporous scaffolds offers notable benefits in terms of efficient CO2 capture.

Synergistic effect of surfactant and silica nanoflowers support on CO2 capture from simulated flue gas by solid amine adsorbents

Solid amine adsorbents were synthesized by functionalizing silica nanoflowers (MSN) with large pore volume using Pluronic P123 (P123) and Polyethyleneimine (PEI) to explore their synergistic effect of CO2 capture. At the optimal loading of 65 wt% PEI and 5 wt% P123, the adsorbent (65PEI/5P123-MSN) displayed peak adsorption performance of 4.12 mmol/g under the dry condition. Notably, the introduction of 3 vol% moisture further increased the adsorption capacity of 65PEI/5P123-MSN to 5.33 mmol/g. Meanwhile, the Avrami kinetic model and the thermodynamic analysis shows that adding P123 reduces adsorption heat (55.89 kJ/mol) and regeneration energy (2.01 GJ/ton) of the adsorbent.

Co-grafting of polyethyleneimine on facilely synthesized mesoporous P(DVB-D) for highly effective CO2 adsorption and enhanced oxidation resistance

Solid amine adsorbents are showing promise as effective adsorbents for the capture of CO2 from various gas mixtures, including biogas and flue exhaust gas. In this study, we introduced a co-grafting strategy using 1,4-butanediol diglycidyl ether (BDDE) on the surface of P(DVB-D). This approach aimed to exploit the reaction involving the opening of epoxy groups with amine groups, forming covalent bonds between polyethyleneimine (PEI) and mesoporous organic polymers, along with the introduction of hydroxy groups to enhance adsorbent long-term stability and antioxidation ability. After an extensive assessment, P(DVB-D)@B-41.2 %PEI exhibited a maximum CO2 capture capacity of 4.53 mmol/g at 50 °C and 50 % RH. Notably, its remarkable CO2 adsorption performance persisted across a diverse temperature spectrum (30–90 °C) and an extensive concentration span (5–30 % vol.). In contrast to conventional adsorbents prepared solely through impregnation methods, P(DVB-D)@B-41.2 %PEI exhibited impressive long-term stability throughout 50 successive cycles and excellent resistance to oxidative degradation. These findings underscore the considerable potential of P(DVB-D)@B-41.2 %PEI in the realm of carbon capture and sequestration (CCS) technology.

Amine-functionalized high-surface-area Al2O3 adsorbent for CO2 capture: Effect of the support calcination conditions

Porous alumina has garnered interest as a substrate in the development of solid amine adsorbents for CO2 capture. However, the calcination conditions of alumina can significantly alter its properties, which in turn affects the adsorption performance of the resulting adsorbents. In this study, high-surface-area alumina was synthesized using a reverse microemulsion method. The impact of the calcination conditions on the pore structure and surface properties of the alumina precursor was examined. Additionally, the porous alumina produced under various calcination conditions served as the support for tetraethylenepentamine (TEPA) loading, and the CO2 capture performance of the resultant adsorbents was assessed. The adsorption kinetics and activation energy were analyzed, emphasizing the cyclic stability when regenerated in a realistic CO2 atmosphere. Our findings indicate that alumina calcined under an air atmosphere with a lid exhibited the highest capture capacity (reaching 89.97 mg/g after a 40 wt% TEPA loading), compared to other alumina samples. The adsorption kinetics corresponded closely with the Avrami model, yielding an activation energy (Ea) of 4.75 kJ/mol. Both alumina samples calcined in air, with and without a lid, demonstrated robust cycling stability and resistance to urea formation. The underlying anti-urea mechanisms were also elucidated in the study.

Two-dimensional interfacial enhanced CO2 adsorption performance of porous organic amine solids: Structure-activity relationships and DFT calculations

The utilization of inexpensive and efficient amine-functionalized adsorbents has become a research hotspot in post-combustion capture technology. Meanwhile, the structure of the support and the selection of organic amines are the primary considerations affecting the CO2 adsorption performance. Herein, the novel solid amine adsorbent materials with amine-support interfacial effect were successfully synthesized in this study by loading four organic amines (TETA, TEPA, PEHA, and PEI) onto expanded vermiculite (EVMT) support with the layered structure. The results indicated that EVMT-50TETA exhibited superior CO2 adsorption capacity (132.5 mg/g) along with effective regeneration capability. This was attributed to the unique layered structure of EVMT that facilitates the dispersion of TETA on its surface or between layers as well as the formation of hydrogen bonds between surface functional groups (–OH) and amines to enhance the amine-support interfacial interaction. Furthermore, the minimal volume expansion of TETA during CO2 adsorption enables improved diffusion of CO2 in channels and enhanced accessibility to active sites. DFT calculations show higher binding energies and faster CO2 adsorption-diffusion rates between TETA and EVMT support. In situ DRIFTS experiments revealed that the process of CO2 adsorption followed the zwitterion mechanism, in which the zwitterion can be reversibly deprotonated to form ammonium carbamate and carbamic acid. This study provides comprehensive insights into the supports and amines interfacial effects through systematic investigation, offering both simplified synthesis strategies and profound theoretical support for studying solid amine adsorbents.