Porous polymers prepared via high internal phase emulsion polymerization for reversible CO2 capture

A series of porous polymers with different pore volumes, pore sizes, and crosslinking densities were synthesized by high internal phase emulsion (HIPE) polymerization. The crosslinked polymerized HIPEs (polyHIPEs) were formed by the copolymerization of 4-vinylbenzyl chloride and divinylbenzene using water droplets in conventional or Pickering HIPEs as the templates. These porous materials were further modified by quaternization and ion exchange to introduce quaternary ammonium hydroxide groups. The resulting polyHIPEs were utilized as sorbents for reversible CO₂ capture from air using the humidity swing. The effect of pore structure on the CO₂ adsorption and desorption processes was studied. The polyHIPEs containing large pores and interconnected porous structures showed improved swing sizes and faster adsorption/desorption kinetics of CO₂ compared to a commercial Excellion membrane with similar functional groups.     

离子液体-水复配吸收剂捕获CO2性能

基于绿色合成方法制备出亲水性离子液体(ILs)[NH₂-C₃mim][Br],从有效降低CO₂吸收-解吸操作成本出发,采用ILs-H₂O复配吸收剂,开展了常温加压CO₂吸收及吸收剂常温减压解吸再生实验。结果表明,比CO₂吸收量(基于复配吸收剂或离子液体组分)随复配吸收剂中ILs组分浓度而变;吸收初期,CO₂吸收速率随吸收剂配比变化显著;以CO₂高吸收率和吸收剂低成本为目标,优选出新型水基复配吸收剂(离子液体与水质量比为1.38:1)。分别以水基离子溶液、改良热钾碱液和活化复配醇胺液为吸收剂,在自行搭建的超重力场强化吸收-连续逆流接触(加热或减压)解吸再生台架实验装置上进行了CO₂捕获与吸收剂再生连续化实验。结果表明,在超重力场作用下,改良热钾碱液和活化复配醇胺液对CO₂有较好的捕获,吸收率分别在98%、96%和90%以上,3种吸收剂经加热或减压解吸再生后均可循环回用,水基离子溶液吸收剂在常温减压下解吸更具有实际可操作性。     

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。     

氨基改性层状双氢氧化物的制备及其二氧化碳吸附机理

以氨基硅烷为改性剂,采用超声剥脱的方法合成了氨基改性的层状双氢氧化物。利用元素分析、X射线衍射(XRD)、漫反射红外傅里叶变换光谱(DRIFTS)和热重分析(TGA)等技术对样品进行了表征。研究了样品在25～150℃温度范围内的二氧化碳吸附能力。在80℃下,NiMgAl N2在纯CO₂和15% CO₂/N₂混合气中达到最大吸附容量,分别为2.02 mmol·g^-1和1.89 mmol·g^-1。吸附/脱附再生实验显示140℃为最佳的脱附温度。利用原位漫反射傅里叶红外光谱对二氧化碳在样品上的吸附进行了机理研究。     

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.     

CO2 sorption performance by aminosilane functionalized spheres prepared via co‐condensation and post‐synthesis methods

Amine functionalized silica microspheres were synthesised via a modified Stöber reaction for carbon dioxide (CO₂) adsorption. A number of adsorbents were synthesized by co‐condensation and post synthesis immobilization of amines on porous silica spheres. CO₂ adsorption studies were carried out on a fixed bed gas adsorption rig with online mass spectrometry. Amine co‐condensed silica spheres were found to adsorb up to 66 mg CO₂ g^?1 solid in a 0.15 atm CO₂ stream at 35°C. Simple post‐synthesis addition of aminopropyltriethoxysilane to amine co‐condensed silica was found to significantly increase the uptake of CO₂ to 211 mg CO₂ g^?1 under similar conditions, with CO₂ desorption commencing at temperatures as low as 60°C. The optimum temperature for adsorption was found to be 35°C. This work presents a CO₂ adsorbent prepared via a simple synthesis method, with a high CO₂ adsorption capacity and favorable CO₂ adsorption/desorption performance under simulated flue gas conditions. © 2016 American Institute of Chemical Engineers AIChE J, 62: 2825–2832, 2016     

Fabrication of PEI-grafted porous polymer foam for CO2 capture

A polymer foam material with both the open-cell porous structure and the polyethylenemine (PEI)-grafted inner face was constructed for CO₂ capture. The porous poly(tert-butyl acrylate) foam was first prepared via a concentrated emulsion polymerization, and then the carboxyl groups were introduced on the interface of porous polymer after the hydrolysis reaction. Subsequently, the surface of the foam was grafted with PEI, and finally the PEI-grafted porous polymer foam designed as a CO₂ capture material was obtained. The structures of the foams were characterized by infrared spectroscopy, EDS, and SEM. The CO₂ adsorption properties were measured by adsorption/desorption cycles. As a result, the polymer foam contained a large number of amine groups (13.9 wt % N), and therefore possessed a high CO₂ adsorption capacity (5.91 mmol g⁻¹ at 40°C and 100 kPa). In addition, they also exhibited high CO₂ adsorption rate, good selectivity for CO₂-N₂ separation, and good stability according to CO₂ cyclic adsorption/desorption test. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47844.     

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.     

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.     

Adsorption of carbon dioxide on ionic liquids-modified active carbons and amino-modified polymer

Active carbons with various particle sizes (38–150, 300–500 and 800–1,200 μm) were modified by ionic liquids (ILs), and organic polymer was modified by acrylamide using a simple procedure, and these materials were applied to capture carbon dioxide (CO₂). The CO₂ adsorption amounts were calculated using a mass balance equation at three different temperatures (298.15, 308.15 and 318.15 K), respectively, and the influences of gas pressure, particle size and temperature on adsorption were discussed. Experimental results showed that the CO₂ adsorption capacity of ILs-modified active carbons was better than amino-modified polymer, and the smaller particle size (38–150 μm) ILsmodified active carbons had the largest adsorption capacity at 298.15 K. Compared with previous research about polyethyleneimine (PEI)-modified silica gel, the adsorption amount of CO₂ on ILs-modified active carbons has been greatly improved with lower cost.     

CO2 Adsorption by Modified Palm Shell Activated Carbon (PSAC) Via Chemical and Physical Activation and Metal Impregnation

The aim of this study was to verify the ability of nickel-impregnated palm shell activated carbon (PSAC) for CO₂ adsorption and compare its performance with the chemically and physically activated PSAC. Sodium hydroxide and CO₂ were used as activating agents for chemical and physical activation, respectively. Nickel nitrate hexahydrate (Ni(NO₃)₂·6H₂O) was used as a precursor for metal impregnation. The effect of different chemical loadings (NaOH: 20–50 wt%), metal impregnation (Ni(NO₃)₂·6H₂O: 16–28 wt%), and heat treatment time (1–4 h) was studied as parameters. Adsorption capacity was calculated using breakthrough graphs. The effect of humidity on CO₂ adsorption and desorption of CO₂ was also investigated in this study. The results revealed that chemically modified PSAC yields the highest adsorption capacity (48.2 mg/g) compared to other methods of activation. Interestingly, it was found that the adsorption capacity of nickel-impregnated PSAC was similar to other types of metal-impregnated activated carbon. Humidity gave a negative effect on CO₂ adsorption. In summary, results showed that chemical activation is an efficient technique to modify PSAC 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.     

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.     

Polymeric ionic liquid modified silica for CO2 adsorption and diffusivity

Two types of polymeric ionic liquids (PILs) modified porous silica for CO₂ sorption were synthesized by the polymerization of dialkylphosphate di‐butyl phosphate [VYIM][Bu₂PO₄] and 1‐allyl‐3‐methylimidazolium tetrafluoroborate [AMIM][BF₄] with alkoxyl‐modified silica. The PILs‐modified silica (SiO₂‐P[VYIM][Bu₂PO₄] and SiO₂‐P[AMIM][BF₄]) were evaluated by CO₂ adsorption isotherms at 273 K for investigating the porous structures. The adsorption and desorption behaviors of CO₂ (at 298, 313, and 333 K) and N₂ (at 313 K) up to 0.2 MPa were also investigated using a gravimetric method. In comparison with bare silica, the grafting of PILs on the support surface leads to a loss of microporosity, resulting in a slight decrease in CO₂ sorption capacity. The difference of CO₂ sorption capacity between SiO₂‐P[VYIM][Bu₂PO₄] and SiO₂‐P[AMIM][BF₄] is little, especially under 0.1 MPa. CO₂/N₂ selectivity is however notably improved, and especially [AMIM][BF₄] modified silica shows the best performance. The homogeneous surface diffusion model (HSDM) was used to estimate the diffusivities and good agreement between experimental values and fitting curves was obtained. The diffusion coefficients of CO₂ in the PILs‐modified silica are level with that of bare silica at level of 10⁻⁷−10⁻⁸ m²/s, about two to three orders of magnitude faster than that of reported [BMIM][BF₄]. POLYM. COMPOS., 38:759–766, 2017. © 2015 Society of Plastics Engineers     

Preparation of silica xerogel with high silanol content from sodium silicate and its application as CO2 adsorbent

In this study, silica xerogels with high silanol content were synthesized by using sodium silicate as low-cost silica source in the presence of hydrochloric acid and acetic acid via sol–gel process for CO₂ adsorption purpose. The effect of amount of acetic acid on the surface and structural properties of silica xerogel was investigated. Fourier transform infrared spectroscopy (FTIR) and thermal gravimetric analysis (TGA) revealed that the silanol groups existed on the surface of silica xerogel products and their concentration increased with increasing the amount of acetic acid. The BET surface area and total pore volume of the silica xerogel prepared using 6 mL of acetic acid (MMS-6) were found to be 1021 m²/g and 0.72 cm³/g, respectively. The pore structure of silica xerogel products consisted of the interparticle voids between the nanoparticles aggregates, and the interconnected wormhole microporous structure. The latter pore structure was more uniform on increasing the amount of acetic acid. CO₂ adsorption/desorption measurements were carried out using TGA unit with high purity CO₂ (99.999%). The highest CO₂ sorption capacity (83.6 mg_CO2/g_sorbent) was obtained with MMS-6 product. Thermal swing adsorption studies showed that the silica xerogel products exhibited strongly reversible CO₂ adsorption capacity and stable during 5-repeated cycle of adsorption/desorption experiment at 35 °C.     

Hypercrosslinked polymers incorporated with imidazolium salts for enhancing CO2 capture

Hypercrosslinked polymers (ILHCPs) incorporated with imidazolium salts were prepared using 4‐vinylbenzyl chloride, divinylbenzene, and imidazole ionic liquid monomers with various alkyl groups and anions by free radical copolymerization and Friedel‐Crafts alkylation reaction. The structures of ILHCPs were characterized by using FT‐IR, solid state ¹³C CP/MAS NMR spectroscopy, TGA, and gas adsorption. ILHCPs exhibit excellent capability of CO₂ adsorption compared with that of nonfunctional hypercrosslinked polymers (HCPs), although both the BET surface area (447–667 m²/g) and pore volume (0.24–0.28 cm³/g) of ILHCPs are less than HCPs. The synergistic effect from mirco/mesopore structures and imidazolium salts are proved to play a key role in enhancing the CO₂ adsorption capability and selectivity over other gases for ILHCPs. It can be found that the imidazolium salts content in HCPs is more important compared with the pore texture for adsorbing CO₂. An optimal molar content of imidazolium salts groups is found to be 10.5% with the maximum CO₂ uptake capability of 7.56 wt% and best CO₂ adsorption selectivity (CO₂/N₂) of 47.9/1 (273 K, 1 bar), while those of the HCPs are only 5.93 wt% and 27.9/1. Such results strongly suggest that ILHCPs can be promising applied in selective CO₂ separation. POLYM. ENG. SCI., 56:573–582, 2016. © 2016 Society of Plastics Engineers     

CO2 Adsorption and Desorption for CO2 Enrichment at Low-Concentrations Using Zeolite 13X

Adsorption of CO₂ using zeolite 13X as adsorbent has been studied extensively, but little attention has been paid to CO₂ adsorption at very low concentrations such as in the ambient air. Furthermore, there is almost no information on CO₂ desorption characteristics. In a carbon enrichment for plant stimulation system, ambient CO₂ is enriched from 400 to 1000 ppm to provide an enriched CO₂ stream for plant growth in greenhouses. To provide essential design data, systematic performance tests were carried out to evaluate both the adsorption and desorption capacity, enrichment factor, moisture content, and cyclic performance. It was found that the adsorption capacity and CO₂ concentration in the enriched air are a function of adsorption temperature and the difference of adsorption and desorption temperatures, for a given adsorbent loading at a properly selected gas flow rate.     

Graphene oxide functionalized by poly(ionic liquid)s for carbon dioxide capture

Poly(ionic liquid)s have been demonstrated as high efficient CO₂ absorbents. In the current study, a kind of poly(ionic liquid)s, Poly[2‐(methacryloyloxy)‐ethyl] trimethylammonium tetrafluoroborate (P[MATMA][BF₄]) was used to functionalize graphene oxide (GO). The hybrid in which P[MATMA][BF₄] was covalently bonded on GO platelets was prepared by a simple method, that is, traditional radical polymerization. The characterizations based on transmission electron microscopy, scanning electron microscope, Fourier transform infrared spectroscopy, Raman spectroscopy, X‐ray diffraction, and X‐ray photoelectron spectroscopy demonstrated the graft of P[MATMA][BF₄] on GO. N₂ adsorption measurements indicated that P[MATMA][BF₄] also greatly increased the specific surface area of GO. Due to the higher specific surface area and the CO₂ affinity of P[MATMA][BF₄], the GO‐P[MATMA][BF₄] hybrid exhibited a much higher CO₂ adsorption capacity compared with GO, GO‐NH₂, and P[MATMA][BF₄]. Their study showed that the combinations of poly(ionic liquid)s and GO could be promising CO₂ absorbents. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44592.     

Novel method for determination of gas solubilities in low vapor pressure liquids

A modified version of a standard device for measuring gas adsorption and desorption isotherms and surface area of adsorbents and catalysts (ASAP (Accelerated Surface Area and Porosimetry System) 2020, Micromeritics USA) is used for the first time to measure gas solubilities (i.e., CO₂) in low vapor pressure liquids (i.e., the IUPAC standard ionic liquid 1‐hexyl‐3‐methylimidazolium bis(trifluoromethylsulfonyl)imide ([C₆mim][Tf₂N])) in the Henry's law region. The solubility data are in very good agreement with the reported data in literature. Furthermore, the Henry's law constants are calculated from the solubility data and compared to the experimental data found in literature. The results from this study demonstrate that Micromeritics ASAP 2020 is a suitable apparatus for gas absorption by solvents with reduced vapor pressures. © 2017 American Institute of Chemical Engineers AIChE J, 63: 2981–2986, 2017     

Pith based spherical activated carbon for CO2 removal from flue gases

Serials of pitch based spherical activated carbons (PSACs) were prepared and used as adsorbent for CO₂ adsorption from flue gases. The results indicate that the ultrafine micropores (<1 nm) are effective pores for CO₂ adsorption, and the equilibrium adsorption capacity of CO₂ has a linear relationship with the specific surface area of ultrafine micropores (S_{<1 nm}). The adsorption capacity of CO₂ can obtain 1.12 mmol/g at 15 kPa and 30 °C on one of PSAC sample due to its high S_{<1 nm} (845 m²_/g). Because the molecular CO₂ can be polarized into polar molecules and has four kinds of adsorption configuration, the adsorption selectivities of CO₂ vs. N₂ and O₂ are 86.99% and 69.91%, respectively. When the combined Electric Swing Adsorption and Vacuum Swing Adsorption were applied for CO₂ desorption, about 100% desorption efficiency can be obtained, the desorption rate is twice of that with Temperature Swing Adsorption (TSA) and the energy consumption is only 69% of that with TSA.