Tetraethylenepentamine Loading Research Articles

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.

Amine-Functionalized Meso-Macroporous Polymers for Efficient CO2 Capture from Ambient Air.

Over the past decade, direct air capture (DAC) of carbon dioxide (CO2) using solid nanoadsorbents has garnered attention as a negative emission technology with high energy efficiency. Although operational, the large-scale deployment of DAC technologies has been significantly delayed due to the low performance and high cost of solid DAC nanoadsorbents. Herein, we present a novel family of meso-macroporous melamine formaldehyde (MF) materials with a facile preparation methodology, low capital cost, and unique physicochemical characteristics for DAC. The fabricated MF materials exhibit an extra-large pore volume of 5.19 cm3/g with a 24.6 nm average pore diameter. We show that the synthesized MF materials can be used as substrates and impregnated with different amounts of tetraethylenepentamine (TEPA) to act as chemical nanoadsorbents for DAC. Owing to the ultrahigh pore volume of MF, a substantial amount of 71 wt % TEPA (i.e., MF-TEPA71%) can be loaded, resulting in 2.65 mmol/g of CO2 uptake under DAC conditions. In addition, the superior physicochemical properties of MF lead to a high CO2 loading of 2.07 mmol/g with low TEPA loading in MF-TEPA33%. The prepared MF-TEPA nanoadsorbents can be successfully employed in different shapes (i.e., droplets, pellets, and coatings) and maintain their superiority across different temperatures and CO2 concentrations. This study provides a promising approach for developing meso-macroporous substrates through a straightforward and scalable synthesis method, representing a new avenue for the next generation of DAC nanoadsorbents with superior performance for practical applications.

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.

High Gravity-Enhanced Direct Air Capture: A Leap Forward in CO2 Adsorption Technology

Given the global pressure of climate change and ecological equilibrium, there is an urgent need to develop effective carbon dioxide (CO2) capture technology. Due to its comprehensiveness and flexibility, Direct Air Capture (DAC) technology has emerged as a vital supplement to traditional emission reduction methods. This study aims to innovate Direct Air Capture (DAC) technology by utilizing the ultrasonic impregnation method to load Tetraethylenepentamine (TEPA) onto alumina (Al2O3) as the adsorbent. Furthermore, high gravity adsorption technology is integrated to significantly enhance the efficiency of DAC. Characterization tests, including BET, FTIR, TG, XRD, and SEM-EDS, confirm the structural stability and high capture capacity of the adsorbent. Additionally, this study demonstrates the rapid and efficient capture of CO2 from the air using TEPA-Al2O3 adsorbent under high gravity conditions for the first time. Under optimal conditions with TEPA loading at 15.06%, a high gravity factor of 2.67, and a gas flow rate of 30 L/min, TEPA-Al2O3 achieves a CO2 adsorption capacity of 48.5 mg/g in RAB, which is an improvement of 15.56 mg/g compared to traditional fixed-bed technology. Moreover, it reaches adsorption saturation faster under high gravity conditions, exhibiting a significantly higher adsorption rate compared to traditional fixed-bed systems. Furthermore, the adsorption process better conforms to the Avrami model. Steam stripping regeneration is utilized to regenerate the adsorbent, demonstrating excellent regeneration performance and stable adsorption capacity, thereby proving its feasibility and economic benefits as a DAC technology.

Synthesis of Ca-based metal–organic frameworks from carbide slag for CO2 adsorption

Metal-organic frameworks (MOFs) are a promising material for CO2 adsorption because of their great specific surface area, well-ordered porous structures ordered porous structure and various means available for functionalization. In this work, the calcium squarate (UTSA-280) was synthesized from carbide slag without pretreatment at room temperature by a rapid mechanochemical method, and then was further functionalized with tetraethylenepentamine (TEPA) to prepare CO2 adsorbents. The effects of water content, ball milling frequency, adsorption temperature, and TEPA loading on CO2 adsorption performance of various adsorbents were investigated. The results showed that the CO2 adsorption of the synthesized MOFs increased firstly and then decreased with increasing water content and ball milling frequency. The synthesized MOFs with water content of 300 mmol and ball milling frequency of 15 HZ exhibited the best crystallinity. The addition of TEPA provided additional adsorption sites and led to the increase of CO2 adsorption capacity. The UTSA-280–300-15-40TEPA demonstrated the highest CO2 adsorption capacity (2.89 mmol/g) at 25 °C. The CO2 adsorption kinetics analysis showed that the Avrami model fitted well with the experimental results. Furthermore, the UTSA-280–300-15-40TEPA exhibited excellent chemical stability during the adsorption–desorption cycles, with only a 14.53 % decrease in adsorption capacity after 10 cycles. This work demonstrated the possibility of preparing UTSA-280 using carbide slag for effective CO2 adsorption.

Direct Air Capture of CO2 over Amine-Modified Hierarchical Silica

The current study reports the utilization of tetraethylenepentamine (TEPA)-modified hierarchical silica particles having bimodal meso/macroporosity for CO2 capture under simulated direct air capture (DAC) conditions (400 ppm CO2 in He). Results infer a typical relation between TEPA loading and CO2 capture, where TEPA-impregnated HS (HS-TEPA-70) exhibits exceptionally high CO2 uptake (5.20 mmol/g), shorter adsorption half time (110 min), and excellent amine efficiency (0.32 mmol of CO2/mmol of N) with moderate CO2/N2 selectivity at 30 °C under DAC conditions. HS-TEPA-70 also showed appreciable CO2 adsorption performance (5.88 mmol/g) under humid conditions (50 ± 3% RH) with 400 ppm CO2 in He at 30 °C. TEPA-impregnated HS even displays better thermal stability up to 10 consecutive adsorption–desorption cycles with minimal amine leaching and moderate CO2 regeneration energy. Moreover, the pelletized form of HS-TEPA-70 also demonstrates better CO2 adsorption performance (3.34 mmol/g), which makes it a promising candidate for CO2 capture from ambient air by temperature swing adsorption.

Synthesis, Characterization and Gas Adsorption of Unfunctionalized and TEPA-Functionalized MSU-2

Michigan State University-2 (MSU-2) is notable potential adsorbent for carbon dioxide (CO2) due to its intrinsic properties, which include its highly interconnected three-dimensional (3D) wormhole-like framework structure, high specific surface area, and its large total pore volume, as well as its large amount of surface silanol hydroxyl groups, which facilitate the amine functionalization process. In this study, unfunctionalized MSU-2 was synthesized via a fluoride-assisted two-step process via the solution precipitation method, using Triton X-100 as the surfactant and tetraethylorthosilicate (TEOS) as the silica precursor. Then, the synthesized MSU-2 was functionalized using varying tetraethylenepentamine (TEPA) loadings of 20–60 wt%. The effect of different TEPA loadings on the properties and CO2 adsorption capacity of the MSU samples was investigated. Studies of the CO2 adsorption of the unfunctionalized and TEPA-functionalized MSU-2 samples was conducted at 40 °C and 1 bar of pressure. Furthermore, scanning electron microscopy (SEM); surface area and porosity (SAP) analysis; carbon, hydrogen, nitrogen, and sulfur (CHNS) analysis, X-ray diffractometry (XRD); Fourier transform infrared (FTIR) spectrometry; and thermogravimetric analysis (TGA) were utilized to characterize the resultant unfunctionalized and TEPA-functionalized MSU-2 with different TEPA loadings in order to study their morphologies, pore characteristics, elemental compositions, crystallographic structures, functional groups, chemical bonding, and thermal stability, respectively. The comprehensive results obtained from the analytical instruments and the CO2 adsorption studies indicated that the TEPA-functionalized MSU-2 with 40 wt% of TEPA loading achieved the highest average CO2 adsorption capacity of 3.38 mmol-CO2/g-adsorbent.

Adsorption application of tetraethylenepentamine (TEPA) modified SBA-15@MIL-101(Cr) in carbon capture and storage (CCS)

To design a better carbon capture material, a SBA-15@MIL-101(Cr) composite is prepared by an in situ synthesis method, and its adsorption performance is enhanced by TEPA modification. The SBA-15 with well-ordered mesopores acted as a carrier, which regulated the growth of MIL-101(Cr) crystals. The silicon hydroxyl group in SBA-15 stably binds to TEPA in the form of hydrogen bond, and the Lewis acid site (CUS) in MIL-101(Cr) makes it bind to TEPA in coordination bond. The unique pore cage structure of MIL-101(Cr) and the basic site provided by TEPA make the material contain both physical and chemical adsorption forces in the process of adsorption of CO2 molecules. The good thermal stability of SBA-15 improves the thermal stability of MIL-101(Cr) and TEPA in the SBA-15 channel. Compared with the original MIL-101(Cr), the composite and modified materials showed higher CO2 absorption capacity at 298K and 100 kPa. By fitting the Langmuir equation and Freundlich equation, it can be found that the adsorption behavior of the materials after TEPA loading has the non-uniformity of surface binding. The adsorption behavior is a typical exothermic process, so the adsorption capacity of the material is inversely proportional to the temperature. Compared with other similar materials, the materials designed in this work have good CO2 adsorption energy per unit area, and also have good reusability. Therefore, this study opens a new way for the design of graded porous amine-modified MOF-based materials with advanced gas adsorption properties.

Preparation and CO2 adsorption properties of TEPA-functionalized multi-level porous particles based on solid waste

In this paper, tetraethylenepentamine (TEPA)-functionalized solid waste-based porous particles were prepared by the wet impregnation method, and their functionalization characteristics and CO2 adsorption performances at different TEPA loadings were investigated. Through a scanning electron microscope test and a N2 adsorption/desorption test, it is found that, as the TEPA loading increases from 4 wt% to 20 wt%, the specific surface area and pore volume of the samples decrease slowly and micropores gradually disappear. Besides, the CO2 adsorption capacity of the samples was tested by a fixed-bed adsorption experimental device at 298 K and 0–1 bar. The results show that the CO2 adsorption capacity reaches the maximum (71.29 mg/g) at a 12 wt% TEPA loading, which is attributed to the high content of affinity sites in CO2. Furthermore, the effect of temperature (298–398 K) was investigated at 1 bar. It is concluded that an appropriate increase in adsorption temperature can enhance the flexibility of TEPA and greatly reduce its diffusion resistance. The highest adsorption capacity (83.05 mg/g) is achieved at 348 K. Then, the effect of pressure (0–40 bar) was analyzed at the optimal temperature (348 K) and optimal TEPA loading (12 wt%), and the results suggest that the adsorption capacity gradually strengthens with the increase in pressure, ultimately reaching a peak of 204.06 mg/g. The adsorption selectivities of CO2/N2 and CO2/H2 are 14.88 and 9.66, respectively, indicating that the porous particles have a stronger affinity for CO2 than for N2 and H2. The infrared spectra prove the formation of carbamates, which confirms that CO2 is sequestered in porous particles by chemical adsorption. The adsorption kinetics and adsorption thermodynamics results reveal the presence of both physical and chemical adsorptions of 12 wt% TEPA-porous particles in the adsorption process, and the chemical one is dominant.

A brief on tetraethylenepentamine (TEPA) functionalized-adsorbents in CO2 capture application

Abstract Among numerous carbon capture technologies, adsorption is considered one of the most effective approaches to reduce carbon dioxide (CO2) emissions in the atmosphere. Various modification approaches of adsorbents have been introduced to enhance the CO2 adsorption ability. Recently, an amine such as tetraethylenepentamine (TEPA) has been extensively used as an adsorbent’s promoter because of its high amine density, low viscosity, low cost, and low toxicity properties. This has added an advantage to the adsorbent in terms of economical and environmentally benign. Therefore, it is important to provide the latest review on TEPA-functionalized adsorbents, specifically on the effects of TEPA functionalization, different TEPA loading, diverse adsorption conditions, as well as the structure of adsorbents towards the CO2 adsorption capacity. Different adsorption conditions over a wide range of adsorption temperatures were thoroughly discussed and several recommendations for future studies were also been proposed.

A novel preparation of solid amine sorbents for enhancing CO2 adsorption capacity using alumina-extracted waste

A “wet gel impregnation” method (WGI) was applied to prepare modified CO2 sorbents derived from alumina-extracted residue of coal ash (AR). Tetraethylene pentamine (TEPA) was selected as an amine polymer and it was evenly dispersed on the surface of AR. And the effects of loading amount, impregnation method, and adsorption temperature on CO2 adsorption capacity of the sorbent were investigated by thermogravimetric analyzer (TGA). The results showed that the desired sorbent with 60% TEPA loading via WGI had the maximum CO2 adsorption capacity of 3.45 mmol/g under 100% CO2 at 75 °C. This was attributed to the fact that the loading in wet gel state dramatically improved TEPA dispersion on the supports and increased the saturated loading of amine. Moreover, the sorbent still maintained stable CO2 uptake after five repeated adsorption-desorption cycles. These results suggested that amine-impregnated AR sorbent synthesized by WGI was an excellent and low-cost sorbent for CO2 capture.

Single site Ni(II) anchored tetraethylene pentamine for enhancing CO2 kinetic adsorption rate and long-term cyclic stability

Rapid kinetic adsorption and long-term cyclic stability are two of the major obstacles to the industrialization of solid amine adsorbents. The morphology and dispersibility of the organic amine in the pore structure of the support can strongly affect the adsorption rate and stability of CO2. In this work, we propose a strategy that enhances the dispersion and stability of tetraethylene pentamine (TEPA) via anchoring TEPA with single site Ni(II) in the pore of the commercial mesoporous silica gel (SG). The microscopic morphology and dynamic behavior of TEPA molecules in the adsorbents preparation process were explored by molecular dynamics simulation, which proved that the dispersibility of anchored TEPA in the porous structure has been improved, resulting in enhanced mass transfer and increased kinetic adsorption rate. The anchored Ni-TEPA/SG adsorbents exhibit a 37.5% faster kinetic adsorption rate than TEPA/SG adsorbents at 30 wt% TEPA loading, and the time required to reach 90% of maximum adsorption capacity is shortened by 6 times. Besides, the CO2 adsorption performance of the optimized Ni-TEPA/SG adsorbent remains unchanged after 20 cycles, consolidating the potential of our proposed strategy in improving the kinetic adsorption rate and cyclic stability of solid amine adsorbents as well as promoting its industrialization.

Amine-impregnated polymeric resin with high CO2 adsorption capacity for biogas upgrading

Solid amine materials are promising adsorbents for CO2 capture from biogas, flue gas and other similar gas mixture. Here, tetraethylenepentamine (TEPA)-impregnated porous polymeric resin (ADS-17) with very high CO2 adsorption capacity was successfully prepared. Its CO2 separation performance from simulated biogas was investigated by breakthrough experiments. And the influence of parameters such as TEPA loading, adsorption temperature and flow rate on the adsorption behaviours were studied in detail. The optimal TEPA loading was 40 wt% (ADS-17–40%TEPA) and the CO2 adsorption capacity of this adsorbent reached the optimal value (ca. 264.2 mg▪g−1) at the flow rate of 200 mL▪min−1. The CO2 adsorption capacity of ADS-17–40%TEPA had no pronounced change from 25 °C to 70 °C, but it decreased obviously when the adsorbent was heated to 90 °C. At 100 °C, the adsorption capacity became negligible. According to detailed characterization, it was inferred that the pores of ADS-17–40%TEPA in the range of 13–115 nm were probably responsible for CO2 diffusion. In addition, ADS-17–40%TEPA possessed good reversibility and the CO2 adsorption capacity was nearly stable after two adsorption–desorption cycles. ADS-17–40%TEPA with high and fast CO2 adsorption exhibits a very promising application in CO2 separation from biogas.

Highly efficient CO2 adsorption by imidazole and tetraethylenepentamine functional sorbents: Optimization and analysis using response surface methodology

SBA-15 was selected as a support and modified with a mixture of tetraethylenepentamine (TEPA) and imidazole (Im) by impregnation method to prepare CO2 solid adsorbents. The Response Surface Methodology (RSM) based on Central Composite Design (CCD) was used to evaluate and optimize the effect of Im, TEPA loading and adsorption temperature as independent variables on the CO2 adsorption capacity as the response function. A good agreement between the model prediction and experimental results. The adsorbents were characterized by BET, XRD, FT-IR, TG, TEM and elemental analysis. The introduction of Im improved the adsorption capacity and thermal stability of the adsorbents, but did not change the structure of SBA-15. This is mainly because that the CO2-C3H4N2 complex formed by Im and CO2 reaction can effectively improve the adsorption efficiency of the adsorbent. SBA-15-39.5% TEPA-22% Im showed the highest adsorption energy by density functional theory (DFT) calculation, − 39.82 kJ/mol. SBA-15-39.5% TEPA-22% Im obtained the highest CO2 adsorption capacity of 4.27 mmol/g in 15 vol% CO2 at 50 °C. After 10 cycles, CO2 uptake remained relatively stable at 4.07 mmol/g.

Robust “dry amine” solid CO2 sorbent synthesized by a facile, cost-effective and environmental friendly pathway

The low cost and facile preparation of CO2 sorbents are extremely important for the practical CO2 capture application. In this study, we demonstrate a facile preparation of “dry amine” CO2 sorbents through a cost-effective and environmental friendly pathway. Commercially available mass-produced SiO2 nanoparticles were used as the support of “molecular basket” sorbents. Tetraethylenepentamine (TEPA) was quickly (60 s) loaded on the surface of SiO2 nanoparticles through high-speed mechanical mixing (22000 rpm) method. Compared with the conventional wet impregnation method, no solvent is required. Although this new pathway is simple, timesaving, cost-effective and environmental friendly, the prepared sorbents present excellent CO2 capture performance. The results show that with the increase of the TEPA loading, the CO2 adsorption amount of the TEPA/SiO2 sorbent increases first and then decreases. The 50TEPA/SiO2 sorbent shows much higher CO2 uptake (3.98 mmol/g) than SBA-15 based sorbent (2.45 mmol/g) prepared through the same method. And it also displays lower mass transfer resistance due to the small particle size and the open structure while 50TEPA/SBA-15 shows larger mass transfer resistance due to the channel structure. The results also show that 50TEPA/SiO2 has good reproducibility. Due to the low cost and facile preparation, the dry amine sorbents may also show the potential application for urgent use, such as SO2 leak or H2S leak.

Exfoliated vermiculite nanosheets supporting tetraethylenepentamine for CO2 capture

CO2 capture is a critical process to reduce CO2 emission into the atmosphere. Here we report a novel and inexpensive composite adsorbent for capturing CO2. The composite was prepared by supporting tetraethylenepentamine (TEPA) onto exfoliated vermiculite (E-VER) nanosheets using wet-impregnation and freeze-drying methods. Vermiculite, as a cheap and natural abundant clay, was delaminated into ultrathin nanosheets via liquid-phase exfoliation. The negatively charged E-VER has exposed surfaces and a large surface area, which is ideal for supporting TEPA with the desired loading. It was found out that the TEPA loading has a crucial impact on the pore structures, surface areas, and the CO2 adsorption capacities. E-VER-TEPA-2% with a TEPA loading of 2% demonstrates the optimal performance for CO2 capture, showing a CO2 adsorption capacity of 29.5 ​mmol/g at 45 ​bar and 25 ​°C and 22.6 ​mmol/g at 40 ​bar and 75 ​°C. The E-VER/TEPA composites are compressible, a volumetric capacity of 29.93 ​mmol/cm3 was obtained for E-VER-TEPA-2% at 45 ​bar and 25 ​°C after being compressed at 20 ​MPa. Furthermore, E-VER/TEPA composites exhibited excellent cyclic stability over six cycles and long-time heat-treatment.

Optimization of CO2 Adsorption on Solid-Supported Amines and Thermal Regeneration Mode Comparison.

For improving the CO2 adsorption capacity of solid-supported amines, five commercial porous supports have been selected and impregnated with tetraethylenepentamine (TEPA), and their CO2 adsorption performances have been evaluated using a fixed-bed reactor coupled with mass spectrometry. For solid-supported amines, CO2 adsorption capacities coincide with the texture characterization of the adsorbent supports (mesoporous alumina, montmorillonite, silica gel, porous resin, MCM-41 molecular sieve), and the optimum TEPA loading amount is mainly affected by the pore volume. The mesoporous supports were found to be more conducive to uniform loading of organic amine, with more than 370 mg/g CO2 adsorbed per unit TEPA. Other components in flue gas, especially H2O, favor CO2 adsorption on solid-supported amines. SO2 inhibited the CO2 adsorption, which was mainly attributable to the strong and irreversible binding of SO2 on some amine sites. NO had little effect on CO2 adsorption. Thermal stabilities of solid-supported amines have been tested based on thermogravimetry curves, and the main weight loss peak for TEPA appears at 513 K for solid-supported amines. Linear and step regeneration modes have been compared, revealing that the temperature for step regeneration is 37 K lower than that for the linear regeneration mode. Moreover, the desorption peak area for the step regeneration mode is 20% higher than that for the linear regeneration mode, indicating that the step regeneration mode can be used in practical applications, to reduce energy consumption during regeneration.

Characteristics and carbon dioxide adsorption performance of amine-impregnated KCC-1 with different loading ratio

With our climate condition worsening day by day, the effort to mitigate this effect has been intensified. One of the ways to curb this issue is by reducing the release of carbon dioxide (CO2) to the atmosphere via CO2 capture. Among all the material used for CO2 capture, amine-impregnated porous silica was observed to be a promising adsorbent. Research has shown its potential, but the accessibility issues caused by its narrow pore opening limits its capabilities. KCC-1, the latest member of the porous silica family, possesses unique fibrous morphology that can solve this problem. In this paper, a series of Tetraethylenepentamine (TEPA)-impregnated KCC-1 (KCC-1/TEPA) synthesized at three different loading ratios (KCC-1 to TEPA 2:1, 1:1 and 1:2) is reported. Characteristics study was conducted to determine the effect of loading ratio on its properties, and its CO2 adsorption capacity was evaluated. FTIR peaks at 3430 cm−1, 3300 cm−1, 2950 cm−1, 2841 cm−1, 1658 cm−1, 1565 cm−1 and 1465 cm−1 revealed that the impregnation was successful, while XRD diffractogram indicated that KCC-1 structure remained preserved in all impregnated samples. Increased surface area and pore volume reduction was observed with the increase of TEPA-loading ratio. KCC-1/T1:2 reported the highest CO2 adsorption value among all three impregnated sample with 141 mg/g, while KCC-1/T2:1 recorded the lowest (82 mg/g). Results indicated that increasing TEPA loading ratio increases the number of active sites for CO2 to attached, hence lead to increase CO2 capture. Overall, it was shown that amount of CO2 adsorbed is related to the amount of TEPA loaded to the sorbent.

TEPA impregnation of electrospun carbon nanofibers for enhanced low-level CO2 adsorption

The CO2 adsorption selectivity of plain activated carbon nanofibers (ANF) is generally low. For enhancement, nitrogen functionalities favorable for CO2 adsorption are usually tethered to the ANF. In the current study, we adopted chemical impregnation using 0.5 wt% tetraethylenepentamine (TEPA) solution as an impregnant. To enhance the impregnation of TEPA further, preliminary oxidation of the nanofibers with 70% HNO3 was conducted. The effects of HNO3 and TEPA treatments on the modified ANFs were investigated for physical (using N2 monosorb, thermogravimetric analyzer, scanning electron microscopy) and chemical (X-ray photoelectron spectrometer) changes. From the results, we found that although TEPA impregnation reduced the specific surface area and pore volume of the ANFs (from 673.7 and 15.61 to 278.8 m2/g and 0.284 cm3/g, respectively), whereas the HNO3 pre-oxidation increased the number of carboxylic groups on the ANF. Upon TEPA loading, pyridinic nitrogen was tethered and further enhanced by pre-oxidation. The surface treatment cumulatively increased the amine content from 5.81% to 13.31%. Consequently, the final adsorption capacity for low (0.3%) and pure CO2 levels were enhanced from 0.20 and 1.89 to 0.33 and 2.96 mmol/g, respectively. Hence, the two-step pre-oxidation and TEPA treatments were efficient for improved CO2 affinity.

Amine functionalized hierarchical bimodal mesoporous silicas as a promising nanocomposite for highly efficient CO2 capture

Amine loaded solid adsorbents are promising for the post-combustion CO2 capture. A current challenge is how to synthesize support with excellent pore structure by cost-effective methods as supports for amine loading. Herein, hierarchical bimodal mesoporous silica (HMS) was synthesized by using P123 as template through the partitioned cooperative self-assembly process. The prepared HMS is found to have large pore volumes and hierarchical pore networks. Subsequently, a series of tetraethylenepent amine (TEPA) functionalized adsorbents is prepared and CO2 capture measurements were implemented in a fixed-bed reactor to investigate the effects of TEPA loading and mesoporous structure. And the influence of CO2 concentration on capture performance was also studied in both In-situ DRIFTS and adsorption kinetic ways. The results show that the CO2 capture amount of HMS is up to 5.82 mmol/g at 70 wt.% TEPA loading and 75 ℃ with 15 vol% CO2. The large pore volumes significantly increase the amine loading and the interconnected hierarchical mesopores networks facilitated the dispersion of amine. The higher CO2 concentrations is conducive to the formation of carbamic acid and the decrease of CO2 adsorption activation energy, thereby facilitating the CO2 adsorption. In addition, poly (propylene glycol) bis (2-aminopropyl ether) (PEA) was also introduced in the adsorbent to further improve the adsorption performance. The results show that the introduction of PEA can offer increased CO2 capture amount, improved thermal stability and regenerability due to the participation of the ether group in the reaction of CO2 with the amine group and improved the thermal stability of the TEPA and PEA co- functionalized adsorbent.