Direct dual layer spinning of aminosilica/Torlon® hollow fiber sorbents with a lumen layer for CO2 separation by rapid temperature swing adsorption

The direct dual layer spinning of Torlon^®/silica hollow fibers with a neat Torlon^® lumen layer is reported here for the first time. The dual layer fibers containing a porous Torlon^®/silica main structure and a dense, pure Torlon^® polymer bore‐side coating provide a simplified, scalable platform from which to construct hollow fiber amine sorbents for postcombustion CO₂ capture. After fiber spinning, an amine infusion process is applied to incorporate PEI into the silica pores. After combining dilute Neoprene treatment followed by poly(aramid)/PDMS treatment, a helium permeance of the fiber sorbents of 2 GPU with a He/N₂ selectivity of 7.4 is achieved. Ten of the optimized amine‐containing hollow fibers are incorporated into a 22‐inch long, 1/2 inch OD shell‐and‐tube module and the module is then exposed on the shell side to simulated flue gas with an inert tracer (14 mol % CO₂, 72 mol % N₂, 14 mol % He [at 100% R.H.]) at 1 atm and 35°C in a RTSA system for preliminary CO₂ sorption experiments. The fibers are found to have a breakthrough and equilibrium CO₂ capacity of 0.8 and 1.2 mmol/g‐ dry fiber sorbent, respectively. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41845.     

CO2 adsorption performance of polyethyleneimine-modified ion-exchange resin

A series of solid amine adsorbents were prepared by the template method with ion-exchange resin (D001) as the carrier and polyethyleneimine (PEI) as the modifier. The absorbents were characterized by energy disperse spectroscopy (EDS), scanning electron microscope (SEM), N₂ adsorption–desorption, Fourier transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA) techniques. The effects of PEI loading, adsorption temperature and influent velocities on CO₂ adsorption capacity in a fixed-bed reactor were investigated. The results show that the solid amine adsorbent prepared by the template method had a better PEI dispersion, stability and CO₂ adsorption capacity. The maximum CO₂ adsorption capacity was 3.98 mmol·g^?1 when PEI loading was 30%, the adsorption temperature was 65°C and the influent velocity was 40 mL·min^?1. The CO₂ adsorption capacity decreased only by 9.50% after 10 cycles of adsorption–desorption tests. The study of kinetics indicates that both chemical adsorption and physical adsorption occurred in the CO₂ adsorption process. The CO₂ adsorption process included fast breakthrough adsorption and gradually approaching equilibrium stage. The particle internal diffusion process was the control step for CO₂ adsorption.     

Carbon dioxide capture under postcombustion conditions using amine-functionalized SBA-15: Kinetics and multicyclic performance

ABSTRACT

In this work, ordered mesoporous SBA-15 was synthesized and functionalized by polyethyleneimine (PEI). The morphological properties were characterized by N₂ adsorption/desorption, field–emission scanning electron microscopy (FE-SEM), high–resolution transmission electron microscopy (HR-TEM) and Fourier transform infrared (FTIR) spectroscopy methods. The carbon dioxide (CO₂) uptake on the sorbents, kinetics of CO₂ adsorption/desorption and long-term multicycle stability of PEI-impregnated sorbent were measured. An optimal amine loading of 50 wt.% showed a CO₂ adsorption capacity ~3.09 mmol g^?1 using 10% pre-humidified CO₂ at 75°C. The presence of moisture in flue gas showed a promoting effect in CO₂ sorption capacity. The temperature swing adsorption/desorption cycles showed excellent multicycle stability over 60 cycles during 65 h of operations under humid CO₂.     

Aminating modification of viscose fibers and their CO2 adsorption properties

An adsorbent for CO₂ capture was prepared by the grafting of acrylonitrile (AN) onto viscose fibers (VFs); this was followed by amination with triethylene tetramine (TETA). The effects of the reaction conditions, such as the concentrations of the monomer, initiator, and nitric acid, on the grafting degree and grafting efficiency were studied. The adsorption performance of the adsorbent for CO₂ was evaluated by fixed‐bed adsorption. The highest dynamic adsorption capacity of the adsorbent for CO₂ was 4.35 mmol/g when the amine content of the adsorbent VF–AN–TETA reached 13.21 mmol/g. Compared with the polypropylene (PP)‐fiber‐based adsorbent (PP–AN–TETA), VF–AN–TETA with hydroxyl groups on the fibers facilitated the diffusion of CO₂ and water and led to a higher CO₂ adsorption capacity than that of PP–AN–TETA. The VF–AN–TETA adsorbent also showed good regeneration performance: its CO₂ adsorption capacity could still retain almost the same capacity as the fresh adsorbent after 10 adsorption–desorption cycles. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 132, 42840.     

Kinetics of CO2 Adsorption/Desorption of Polyethyleneimine‐Mesoporous Silica

The kinetics of adsorption of CO₂ on solid sorbents based on polyethyleneimine/mesoporous silica (PEI/MPS) was studied by following the mass gain during CO₂ flow. Linear (PEI‐423) and branched (PEI‐10k) polymers were studied. The solid sorbents were synthesized by impregnating the PEI into MPS foam. The kinetics of adsorption was fitted with a double‐exponential model. In contrast, the desorption process obeyed first‐order kinetics. The activation energy of desorption of PEI‐423 was lower than that of PEI‐10k, presumably because the branched polymer required more energy to expose its nitrogen to CO₂. To increase the CO₂ sorption capacity, the MPS was treated with nonionic surfactant materials prior to impregnation with PEI. This also lowered the maximum sorption temperature and desorption activation energies.     

Synthesis and CO2 adsorption behavior of amine‐functionalized porous polystyrene adsorbent

A solid amine adsorbent was prepared by modifying a porous polystyrene resin (XAD‐4) with chloroacetyl chloride through a Friedel–Crafts acylation reaction, followed by aminating with tetraethylenepentamine (TEPA). The adsorption behavior of CO₂ from a simulated flue gas on the solid amine adsorbent was evaluated. Factors that could determine the CO₂ adsorption performance of the adsorbents such as amine species, adsorption temperature, and moisture were investigated. The experimental results showed that the solid amine adsorbent modified with TEPA (XAD‐4‐TEPA), which had a longer chain, showed an amine efficiency superior to the other two amine species with shorter chains. The CO₂ adsorption capacity decreased obviously as the temperature increased because the reaction between CO₂ and amine groups was an exothermic reaction, and its adsorption amount reached 1.7 mmol/g at 10 °C in dry conditions. The existence of water could significantly increase the CO₂ adsorption amount of the adsorbent by promoting the chemical adsorption of CO₂ on XAD‐4‐TEPA. The adsorbent kept almost the same adsorption amount after 10 cycles of adsorption–desorption. All of these results indicated that amine‐functionalized XAD‐4 resin was a promising CO₂ adsorbent. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45046.     

Amine modified mesocellular siliceous foam (MCF) as a sorbent for CO2

Adsorption is considered a promising method for carbon capture. CO₂ adsorbents take a variety of forms - but one approach is to fill mesoporous substrates with a polymeric CO₂ selective sorbent. SBA-15 and mesocellular siliceous foam (MCF) are high pore volume, high surface area ordered mesoporous materials for which modification with amine should result in high capacity, highly selective adsorbents. SBA-15 and MCF were separately loaded with approximately one pore volume equivalent of linear polyethyleneimine (PEI) (M_w = 2500) or branched PEI (M_n = 1200). CO₂ adsorption/desorption isotherms under dry CO₂ were obtained at 75, 105 and 115 °C. The CO₂ adsorption/desorption kinetics were improved with temperature, though the CO₂ capacities generally decreased. The adsorption capacity for MCF loaded with branched PEI at 105 and 115 °C were 151 and 133 mg/g adsorbent, respectively (in 50% CO₂/Ar, 20 min adsorption time). These are significantly higher than the adsorption capacity observed for SBA-15 loaded with branched PEI under same conditions, which were 107 and 83 mg/g adsorbent, respectively. Thus the results indicate that, on a unit mass basis, amine modified MCF's are potentially better adsorbents than amine modified SBA-15 for CO₂ capture at modestly elevated temperature in a vacuum swing adsorption process.     

Application of polyethylenimine‐impregnated solid adsorbents for direct capture of low‐concentration CO2

A systematic study of CO₂ capture on the amine‐impregnated solid adsorbents is carried out at CO₂ concentrations in the range of 400–5000 ppm, relating to the direct CO₂ capture from atmospheric air. The commercially available polymethacrylate‐based HP2MGL and polyethylenimine are screened to be the suitable support and amine, respectively, for preparation of the adsorbent. The adsorbents exhibit an excellent saturation adsorption capacity of 1.96 mmol/g for 400 ppm CO₂ and 2.13 mmol/g for 5000 ppm CO₂. Moisture plays a promoting effect on CO₂ adsorption but depends on the relative humidity. The presence of O₂ would lead to the decrease of adsorption capacity but do not affect the cyclic performance. The diffusion additive is efficient to improve the adsorption capacity and cyclic performance. Moreover, the adsorbents can be easily regenerated under a mild temperature. This study may have a positive impact on the design of high‐performance adsorbents for CO₂ capture from ambient air. © 2014 American Institute of Chemical Engineers AIChE J, 61: 972–980, 2015     

Promoted adsorption of CO2 on amine‐impregnated adsorbents by functionalized ionic liquids

Amine‐impregnated adsorbents are promising alternatives to aqueous amines for CO₂ capture. However, the diffusion‐controlled CO₂ adsorption process is a significant issue associated with them, resulting in the insufficient utilization of amine groups. Herein, we propose the use of functionalized ionic liquids 1‐ethyl‐3‐methylimidazolium acetate ([emim][Ac]) with chemical reactivity to CO₂ and low viscosity as the additive to amine‐impregnated adsorbents. The key is that [emim][Ac] does not show drastic increase in viscosity after reacting with CO₂. Taking the polyethyleneimine (PEI)‐impregnated SBA‐15 as a model system, it is found that the CO₂ capacities of PEI/SBA‐15 composites are improved by 86%, and the active site efficiencies are improved by 270%, after the addition of [emim][Ac]. The addition of [emim][Ac] to PEI/SBA‐15 composites also helps improve the CO₂ adsorption rate and recycling stability of composites. Therefore, [emim][Ac] offers the opportunity to fabricate amine‐impregnated adsorbents with simultaneously improved CO₂ capacities, adsorption kinetics, and recycling stability. © 2018 American Institute of Chemical Engineers AIChE J, 64: 3671–3680, 2018     

Simultaneous Adsorption of SO2, NO,and CO2 by K2CO3‐Modified γ‐Alumina

The simultaneous adsorption of SO₂, NO, and CO₂ on K₂CO₃‐modified γ‐alumina under different operating conditions was studied in a fixed‐bed reactor. The experimental results showed that the influence of a temperature increase on the simultaneous adsorption of the three gases was complex and different from the effects seen when both chemical adsorption and competitive adsorption existed. An increase in O₂ concentration and small amounts of water could enhance the adsorption of SO₂ and NO while the adsorption of CO₂ was not influenced. The breakthrough curves of the simultaneous adsorption experiments suggested that the investigated adsorbent may be a good candidate for the simultaneous adsorption of SO₂, NO, and part of the CO₂ while the adsorption capacity for CO₂ still needs to be enhanced.     

拟薄水铝石负载PEI/AMP吸附CO2性能

用富含胺基的物质对多孔材料进行修饰可以得到高CO₂吸附量的吸附剂。采用浸渍法将聚乙烯亚胺(PEI)和2-氨基-2-甲基-1-丙醇(AMP)负载在拟薄水铝石上,考察了CO₂压力、胺类物质负载量等对吸附性能的影响。采用低温N₂吸附/脱附法(BET)、扫描电镜(SEM)、傅里叶变换红外线光谱分析仪(FTIR)等手段表征了吸附剂的结构特征及其物理性质,并使用重量法微天平实验装置对吸附剂的性能进行了评价。实验结果表明,当温度恒定为50℃,压力小于1 MPa时,负载PEI的吸附剂最高的CO₂吸附量为77.53 mg CO₂·(g吸附剂)^-1,最佳负载量为85%;压力大于1 MPa时,负载PEI的吸附剂最高的CO₂吸附量为123.79 mg CO₂·(g吸附剂)^-1,最佳负载量为10%。负载AMP的吸附剂最高的CO₂吸附量为128.01 mg CO₂·(g吸附剂)^-1,最佳负载量为85%。CO₂吸附稳定性实验表明,吸附剂对CO₂的吸附性能稳定。     

Preparation and adsorption properties of polyethylenimine containing fibrous adsorbent for carbon dioxide capture

We successfully prepared a novel fibrous adsorbent for carbon dioxide (CO₂) capture by coating polyethylenimine (PEI) on a glass fiber matrix, using epoxy resin (EP) as crosslinking agent. The physicochemical properties of the fibrous adsorbents were characterized in terms of Fourier transform infrared spectrometry and thermogravimetric analysis. Factors that affected the adsorption capacity of the fibrous adsorbent were studied, including the crosslinking agent dosage, coating weight, moisture, adsorption temperature, and CO₂ concentration of the simulated flue gas. The experimental results indicate that the properly crosslinked fibrous adsorbent had a high thermal stability at about 280°C. With a PEI/EP ratio of 10:1, a maximum adsorption capacity of 276.96 mg of CO₂/g of PEI was obtained at 30°C. Moisture had a promoting influence on the adsorption of CO₂ from flue gas. The CO₂ adsorption capacity of the fibrous adsorbent in the presence of moisture could be 19 times higher than that in dry conditions. The fibrous adsorbent could be completely regenerated at 120°C. The CO₂ adsorption capacity of the regenerated fibrous adsorbent was almost the same as that of the fresh adsorbent. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Breakthrough and Sulfate Conversion Analysis during Removal of Sulfur Dioxide by Calcium Oxide Sorbents

Sorption of sulfur dioxide (SO₂) was carried out on calcium‐based sorbents under dynamic conditions in a fixed bed. The experimental conditions were reaction temperature (700 to 1000°C), SO₂ concentration (1000‐10 000 ppm), sorbent particles size (1 to 2 mm) and the types of sorbents (hydroxide or carbonate). The sorption process was found to be effective at low concentration levels (less than 10 000 ppm) as the breakthrough time significantly decreased with increase in concentration. The maximum removal of SO₂ was observed at a reaction temperature of 950°C. The hydroxide‐based sorbents of relatively smaller particle size were found to exhibit superior sorption performance in terms of longer breakthrough time and higher sulfate conversion. A mathematical model developed, assuming a porous structure of the sorbent materials, attributed the low sulfation conversion during SO₂ sorption due to a pore diffusion mechanism.     

CO2 adsorption on amine-modified mesoporous silicas

Mesoporous silicas with enhanced pore structures were synthesized and polyethylenimine (PEI) was immobilized in them to produce adsorbents for CO₂. The prepared samples were characterized by N₂ adsorption–desorption isotherms and small angle X-ray diffraction, and their CO₂ adsorption performance were evaluated. CO₂ adsorption capacity increased with operating temperature initially and then decreased. Besides, CO₂ adsorption capacity increased due to the PEI loading with more amine sites. The results showed that the structure of support played an important role in the CO₂ adsorption capacity. High surface area and large pore volume also favored the CO₂ adsorption capacity.     

混合胺改性SBA-15的二氧化碳吸附特性

为实现廉价高效的二氧化碳捕集，新型燃烧后CO₂捕集固体吸附材料的设计和开发具有重要的研究意义。为提高CO₂吸附量，胺功能化改性吸附剂的方法主要有湿浸渍和表面嫁接。基于此，提出了“混合胺”修饰的概念，把湿浸渍和表面嫁接两种改性技术结合起来。把3-氨丙基三甲氧基硅烷（APTS）嫁接到分子筛SBA-15孔道表面，再把聚乙烯亚胺（PEI）浸渍到载体孔道的间隙，制备出高密度胺功能化的CO₂吸附剂。主要考察了不同含量的PEI和APTS功能化SBA-15的结构性能、CO₂吸附量及胺吸附效率。CO₂吸附结果表明，混合胺功能化SBA-15吸附主要依赖于动力学扩散。其中，SBA-15-（APTS-0.5-PEI-50），SBA-15-（APTS-1.0-PEI-50）和SBA-15-（APTS-2.0-PEI-30）在75℃时具有很好的吸附潜力。混合胺功能化SBA-15的胺吸附效率介于单纯嫁接和单纯浸渍的胺功能化SBA-15之间。     

Enhanced CO2 adsorption capacity and stability using CaO‐based adsorbents treated by hydration

The synthesis of highly efficient CaO‐based sorbents using Ca(Ac)₂ as a precursor and ethanol as a modification agent for CO₂ capture is described. This adsorbent has several characteristics such as large surface area and pore volume and small particle size. The influence of ratio of ethanol and water on CO₂ adsorption capacity was evaluated considering that the ethanol concentration could affect the pore structure of sorbents. The results showed that CaO modified by ethanol solution had a higher carbonization and better stability. Particularly, when the volume ratio of ethanol and water was 3, a performance of adsorption capacity of 74% and conversion of 94% was observed. CaO modified by ethanol solution had a superior performance due to the decrease of grain size and the formation of loose porous structure. The influence of steam on stability of adsorbents at high temperatures was examined, and it was found that with the existence of steam diffusion, the capacity of the sorbent could remain at a higher level and the stability was evidently improved. After 18 cycles of adsorption/desorption process, the capacity remained as high as 65%. It was proposed that dynamic and cyclic steam injection was favorable for preventing the sintering of sorbents and facilitating the diffusion of CO₂. © 2013 American Institute of Chemical Engineers AIChE J, 59: 3586–3593, 2013     

Removal of Carbon Dioxide from Light Gas Mixtures using a Porous Strontium(II) Silicoaluminophosphate Fixed Bed: Closed Volume and Portable Applications

A Sr²⁺ -SAPO-34 bed was assembled to study CO₂ dynamic adsorption under conditions that emulate those found in closed volume and portable applications. Although the surface area was reduced by 7% during pelletization, adsorption capacities estimated from breakthrough curves compared well with static volumetric adsorption data. Modeling of the breakthrough adsorption was achieved using a Linear Driving Force mass transfer rate model, showing good agreement with the experimental data and confirming fast kinetics and efficient use of the bed. Fast kinetics were also evidenced by the length of the unused section of the bed as calculated from a Mass Transfer Zone model. Adsorption capacity degradation was not observed after multiple regeneration cycles. Apparent and equilibrium adsorption isotherm data estimated from the bed and static volumetric experiments at 25° C were compared to that of 5A Zeolite. These showed that Sr²⁺ -SAPO-34 is a superior adsorbent for CO₂ removal in the low partial pressure range (<1500 ppm). CO₂ and H₂ O multicomponent adsorption breakthrough curves were also gathered for a CO₂ inlet concentration of 1000 ppm and dew points of ?5 and 8° C. The addition of moisture resulted in a decrease in total processed gas volume by 31 and 47%, respectively.     

A novel IL/MOF nanocomposite tailored for trace SO2 efficient capture based on synergistic effects

Due to its toxicity and corrosiveness, it is of enormous significance to efficiently capture and recover sulfur dioxide (SO₂) from flue gas and natural gas. Herein, a new type of IL/MIL-0.7 composite was precisely designed to meet this challenge, which exhibits a high adsorption capacity for SO₂ (13.17 mmol g⁻¹) at 298 K and 1.0 bar while excludes almost completely carbon dioxide (CO₂, 0.27 mmol g⁻¹) and nitrogen (N₂, 0.07 mmol g⁻¹). The high IAST selectivity (at least 11,925) of IL/MIL-0.7 for SO₂/CO₂ can be achieved within the whole test pressure range. In addition, the breakthrough experiment also confirmed the excellent performance of the composite for deep removal of 2000 ppm SO₂. Furthermore, the IL/MIL-0.7 composites can maintain excellent performance after four adsorption/desorption cycles and the thermostability can up to ~450 K. Therefore, this stable IL/MOF composite has the potential application as an effective adsorbent for SO₂ removal from flue gas and natural gas.     

Competitive adsorption of NO,SO2 and H2O onto mordenite synthesized from perlite

A new material, mordenite synthesized from volcanic ash (perlite) in the presence of sodium salts, has been shown to be a weak sorbent for NO and a strong and reversible sorbent for SO₂. The mordenite's capacity to adsorb SO₂ was found to be related to the amount of sodium present in the material. Capacities as high as 8 wt% were achieved at 1250 ppm of SO₂ in helium at 25°C. In multicycle tests the mordenite maintained its capacity after more than 40 cycles when desorbing the SO₂ at 300°C. The adsorption rate of SO₂ in the absence of water was modelled and the adsorption activation energy was found to be 3.2 kcal mol⁻¹. Water significantly decreased the mordenite's capacity to adsorb SO₂ and also caused the SO₂ to be chromatographically desorbed in a roll-up peak. In these water-SO₂ adsorption experiments a peculiar breakthrough was observed for water, where the water concentration exiting the bed first decreased and then increased. This peculiar water breakthrough could not be explained by assuming independent adsorption of the two species, but was qualitatively predicted by assuming that water adsorption is enhanced by the presence of adsorbed SO₂.     

Adsorption microcalorimetry applied to the characterisation of adsorbents for CO2 capture

The present work presents the design, assembly and experimental validation of a microcalorimetric device coupled to a volumetric adsorption setup applied to the characterisation of adsorbents for carbon dioxide (CO₂) capture. Three adsorbents were evaluated for CO₂ adsorption at 273 K in the pressure range of vacuum to 101 kPa. The data for CO₂ on zeolite 13X agreed well with the available data reported in the literature, thus validating the device, which also provided reproducible results with an activated carbon sample. For the amine‐modified zeolite, the differential enthalpy at lower coverage was increased by a factor of 1.7 as compared to the zeolite matrix. This points out to the potential of such technique to characterise heterogeneities introduced by amine impregnation. However, the adsorption uptake was decreased by factor of 2.7 at 101 kPa. This fact suggests that amino groups may be blocking some physisorption sites, leading to restricted chemisorption on the outer surface. Thus, the main novelty of this study is the simultaneous measurement of adsorption isotherms and respective differential enthalpy curves for amine‐impregnated adsorbents, which may be considered a fingerprint of the modified surface chemistry. This work has been carried out in the framework of a cooperation project between three South American universities and is part of the effort to develop and fully characterise adsorbent materials intended for CO₂ capture. © 2012 Canadian Society for Chemical Engineering