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 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.     

Improving Physical Adsorption of CO2 by Ionic Liquids‐Loaded Mesoporous Silica

CO₂ sorption capacities of the neat and silica‐supported 1‐butyl‐3‐methylimidazolium‐based ionic liquids (ILs) were measured under atmospheric pressure. The silica‐supported ILs were synthesized by the impregnation‐vaporization method and charactrized by N₂ adsorption/desorption and thermogravimeteric analysis (TGA). Evaluation of the effects of influential factors on sorption capacity demonstrated that by increase of the temperature, flow rate, and the weight percentage of ILs in sorbents, the sorption capacity decreases. Among the sorbents, [Bmim][TfO] and SiO₂‐[Bmim][BF₄](50) had the highest capacity. By increasing the IL portion in SiO₂‐[Bmim][BF₄], the selectivity for CO₂ to CH₄ could be improved. The CO₂‐rich sorbents could be easily recycled.     

Development of silica‐gel‐supported polyethylenimine sorbents for CO2 capture from flue gas

In order to reduce the sorbent preparation cost and improve its volume‐based sorption capacity, the use of an inexpensive and commercially available silica gel was explored as a support to prepare a solid polyethylenimine sorbent (PEI/SG) for CO₂ capture from flue gas. The effects of the pore volume and particle size of the silica gels, molecular weight of polyethylenimine and amount of polyethylenimine loaded, sorption temperature and moisture in the flue gas on the CO₂ sorption capacity of PEI/SG were examined. The sorption performance of the developed PEI/SG was evaluated by using a thermogravimetric analyzer and a fixed‐bed flow sorption system in comparison with the SBA‐15‐supported polyethylenimine sorbent (PEI/SBA‐15). The best PEI/SG sorbent showed a mass‐based CO₂ sorption capacity of 138 mg‐CO₂/g‐sorbent, which is almost the same as that of PEI/SBA‐15. In addition, the PEI/SG gave a high volume‐based sorption capacity of 83 mg‐CO₂/cm³‐sorbent, which is higher than that of PEI/SBA‐15 by a factor of 2.6. © 2011 American Institute of Chemical Engineers AIChE J, 58: 2495–2502, 2012     

Dynamic CO2 adsorption performance of internally cooled silica‐supported poly(ethylenimine) hollow fiber sorbents

The dynamic adsorption behavior of CO₂ under both nonisothermal and nearly isothermal conditions in silica supported poly(ethylenimine) (PEI) hollow fiber sorbents (Torlon®‐S‐PEI) is investigated in a rapid temperature swing adsorption (RTSA) process. A maximum CO₂ breakthrough capacity of 1.33 mmol/g‐fiber (2.66 mmol/g‐silica) is observed when the fibers are actively cooled by flowing cooling water in the fiber bores. Under dry CO₂ adsorption conditions, heat released from the CO₂‐amine interaction increases the CO₂ breakthrough capacity by reducing the severity of the diffusion resistance in the supported PEI. This internal resistance can also be alleviated by prehydrating the fiber sorbent with a humid N₂ feed. The CO₂ breakthrough capacity of prehydrated fibers is adversely affected by the release of the adsorption enthalpy (unlike the dry fibers); however, active cooling of the fiber results in a constant CO₂ breakthrough capacity even at high CO₂ delivery rates (i.e., high adsorption enthalpy delivery rates). In full RTSA cycles, a purity of 50% CO₂ is achieved and the adsorption enthalpy recovery rate can reach ～72%. Studies on the cyclic stability of uncooled fiber sorbents in the presence of SO₂ and NO contaminants indicate that exposure to NO at 200 ppm over 120 cycles does not lead to a significant degradation of the sorbents, but SO₂ exposure at a similar high concentration of 200 ppm causes 60% loss in CO₂ breakthrough capacity after 120 cycles. A simple amine reinfusion technique is successfully demonstrated to recover the adsorption capacity in poisoned fiber sorbents after deactivation by exposure to impurities such SO₂. © 2014 American Institute of Chemical Engineers AIChE J, 60: 3878–3887, 2014     

Diffusion kinetics of CO2 in amine-impregnated MIL-101, alumina,and silica adsorbents

CO₂ sorption kinetics of poly(ethylenimine) (PEI)-impregnated MIL-101, γ-alumina, and UVM-7 silica were investigated by the zero-length column technique for the purpose of understanding the effect of amine content, adsorbent porosity, and adsorption temperature on CO₂ sorption rates. Each of the adsorbents was impregnated with three different amine contents (20, 35, and 50 wt%) and the effective diffusion time constants were determined at 25°C. For each respective adsorbent, it was found that increasing the amine content results in diminished diffusion rates. Additionally, it was found that the pore size of the support has a profound effect on diffusional kinetics, where microporous MIL-101 yielded substantially slow desorption rates upon amine-functionalization compared to mesoporous γ-alumina. PEI-impregnated UVM-7 silica was further investigated at 50 and 75°C in order to provide insight into the effect of temperature on sorption kinetics. The results indicated that PEI-impregnated UVM-7 exhibited faster sorption kinetics at higher temperatures. Upon desorption, PEI-UVM-7 silica exhibited two distinct regions of mass-transfer control that occur at different sorption times. This is best explained by first the occurrence of surface diffusion followed by diffusion out of the bulky PEI polymer chains. The findings of this study provide novel kinetic characterizations on promising amino-adsorbents for carbon capture applications.     

Low Temperature Liquid State Synthesis of Lithium Zirconate and its Characteristics as a CO2 Sorbent

Abstract

In this study, a new preparation method providing greatly improved CO₂ sorption is introduced. Li₂ZrO₃ sorbent was prepared by low temperature co‐precipitation and compared in CO₂ sorption performance with a sorbent prepared by the conventional high temperature solid‐state reaction method. The two sorbents were characterized using scanning electron microscopy, X‐ray diffraction and thermo‐gravimetric analysis. The Li₂ZrO₃ powder prepared by the relatively simple co‐precipitation method showed significantly better performance than the one prepared by solid‐state reaction with respect to both kinetics and CO₂ sorption capacity. Extensive study of the powder prepared by co‐precipitation has been performed at various conditions.     

High temperature CO2 capture performance and kinetic analysis of Na4SiO4 ceramics

Alkali silicate-based ceramics sorbents were regarded as particularly suitable materials for CO₂ capture at high temperatures, however, the CO₂ capture behaviors of Na₄SiO₄ had been seldom investigated. In this work, the Na₄SiO₄ ceramics samples were prepared using the one-step synthesized method, and the CO₂ sorption/desorption performances at high temperatures, the thermal stability, and the cycling stability of Na₄SiO₄ were systematically investigated. It was demonstrated that the maximum CO₂ sorption capacity of SO-3 sample reached 19.4 wt% at 725 °C, and the optimal condition of cycling tests were 750 °C for sorption and 800 °C for desorption based on the sorption/desorption capacity and rate, which exhibited good thermal stability and high cyclic stability. Besides, the kinetic analysis results showed that the diffusion process was the rate-determining step of CO₂ adsorption, which was more dependent on temperature than the chemisorption process. The structure and surface morphology variations were also investigated, it was interesting that there was a special “fish scale” surface structure after the sorption process, revealing that the melting phenomenon happened during the chemisorption reaction process. By comparing with common sorbent Li₄SiO₄, the material and CO₂ capture costs of Na₄SiO₄ were much lower. These results proved that Na₄SiO₄ was expected to be a suitable high temperature CO₂ capture material as a good supplement to alkali silicate-based ceramics sorbents.     

Acidification Optimization and Granulation of a Steel‐Slag‐Derived Sorbent for CO2 Capture

Steel slag was used as a low‐cost feedstock to prepare CaO‐based sorbents for CO₂ capture by acidification treatment, and the acidification process was optimized. Four main acidification parameters (i.e., extraction time, extraction temperature, acetic acid concentration, and solid/liquid ratio) were investigated. The solid/liquid ratio and extraction time are the most important factors that affect the CO₂ capture capacity and stability of the sorbents. The CO₂ sorption performance of optimal steel‐slag‐derived sorbent is more stable than that of naturally occurring limestone, due to the low Si/Ca ratio and the presence of MgO with high anti‐sintering ability. CaO‐based pellets with high resistance to attrition and compression were produced by extrusion of the steel‐slag‐derived sorbent powders.     

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。     

CO2 capture efficiency in post‐combustion using MWNT‐PAA in a packed bed column

The adsorption capacity of polyaspartamide (PAA) and multi‐wall carbon nanotubes with polyaspartamide (MWNT‐PAA) was investigated through a packed bed column with the flowing of flue gas composed of 15 % CO₂, 5 % O₂ and the balance N₂. The adsorption performed at 25 °C, 110 kPa and inlet gas flow rate of 60 mL/min resulted in high CO₂ adsorption capacity of 5.70 and 10.20 mmol‐CO₂/g for PAA and MWNT‐PAA, respectively. The adsorption kinetics was very high, so 7 min were enough for the effluent gas to reach the breakthrough after saturation. The consistency of adsorbents in recurring regeneration was successful through a continuous TSA system of 10 cycle adsorption‐desorption with temperatures of 25–100 °C. The evaluation of heat through differential scanning calorimetry (DSC) resulted in exothermic adsorption with heat release of 45.14 kJ/mol and 124.38 kJ/mol for PAA and MWNT‐PAA, respectively. The heat release was found favourable to promote the desorption as the temperature could rise after adsorption. This is an advantage for energy efficiency, as it depicts the potential of energy recovery. Thus, both adsorbent PAA and MWNT‐PAA were demonstrated to be promising for CO₂ adsorption capture in post‐combustion.     

Synthesis of highly efficient,structurally improved Li4SiO4 sorbents for high-temperature CO2 capture

Li₄SiO₄ sorbents for high-temperature CO₂ removal have drawn extensive attention owing to their potential application in carbon capture and storage (CCS). The major challenge in the application lies in the poor CO₂ capture performance under realistic conditions of low CO₂ concentrations, owing to the dense structure and poor porosity. In this work, Li₄SiO₄ sorbents were prepared with porous micromorphologies and large contact areas using a variety of organometallic Li-precursors, achieving fast CO₂ sorption kinetics, high capacity and excellent cyclic stability at a low CO₂ concentration (15?vol%). It was found that a high conversion of ~?74% was maintained for pure Li₄SiO₄ even after 100 sorption/desorption cycles. Moreover, by doping with Na₂CO₃ to reduce the CO₂ diffusion resistance, the conversion of the sorbent was further enhanced to 93.2%. The enhancement mechanism of alkali carbonate have been proven here to be ascribed to the formation of the eutectic melt of Li/Na carbonates, the existence and function of which has been confirmed in this study.     

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     

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.     

High-temperature CO2 adsorption over Li4SiO4 sorbents derived from different lithium sources

Li₄SiO₄ is a promising sorbent for high temperature CO₂ capture. It could be synthesized from three different Li sources (LiNO₃, LiOH, and Li₂CO₃) by using the solid state reaction method. The effects of Li sources on the structure and CO₂ adsorption/desorption properties of Li₄SiO₄ sorbents were analyzed in this work. The results showed that Li₄SiO₄ sorbents could be synthesized at a lower temperature by using LiNO₃ and LiOH as the starting materials, which could reduce the sintering during the synthesis process and increase the surface area of synthesized Li₄SiO₄. During the CO₂ adsorption/desorption cycles, Li₄SiO₄ sorbents derived from LiNO₃ and LiOH presented higher initial CO₂ adsorption capacities than those from Li₂CO₃. After 15 cycles, the adsorption efficiency of Li₄SiO₄ derived from LiNO₃ showed no or slight decrease, while that from LiOH rapidly decreased to 20% of the initial value. This was because Li₄SiO₄ derived from LiNO₃ had high surface area and porosity before CO₂ adsorption/desorption cycles, and its surface area even increased after cycles. However, the surface area of Li₄SiO₄ derived from LiOH decreased greatly due to serious sintering. For Li₄SiO₄ derived from Li₂CO₃, its morphology and surface area were almost unchanged before and after CO₂ adsorption/desorption cycles.     

Comprehensive studies on polyethylenimine filled polypropylene and its potential application in carbon dioxide sequestration

Polypropylene (PP) was blended with branched polyethylenimine (PEI) with the aim to prepare blends having CO₂ adsorption property. The CO₂ adsorption properties will be conferred due to the presence of variety of amine functionality in PEI. PEI contains primary, secondary as well as tertiary amine groups. Before testing CO₂ adsorption, PP–PEI blends were characterized using variety of techniques, for example, differential scanning calorimetry, thermogravimetric analysis, dynamic mechanical analysis, scanning electron microscopy, and polarized light optical microscopy. In this work, we have studied in detail both compatibilized as well as noncompatibilized blends of PP and PEI. The compatibilization was achieved via addition of maleic anhydride grafted PP. Finally, all the compatibilized as well as noncompatibilized blends were studied for CO₂ adsorption. The compatibilized blends showed better thermal, mechanical as well as CO₂ adsorption properties as compared to the noncompatibilized blends. POLYM. ENG. SCI., 59:2092–2102, 2019. © 2019 Society of Plastics Engineers     

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.     

High‐Temperature Capture of CO2 on Lithium‐Based Sorbents Prepared by a Water‐Based Sol‐Gel Technique

A convenient water‐based sol‐gel technique was used to prepare a highly efficient lithium orthosilicate‐based sorbent (Li₄SiO₄‐G) for CO₂ capture at high temperature. The Li₄SiO₄‐G sorbent was systematically studied and compared with the Li₄SiO₄‐S sorbent prepared by solid‐state reaction. Both sorbents were characterized by X‐ray diffraction, scanning electron microscopy, nitrogen adsorption, and thermogravimetry. The CO₂ sorption stability was investigated in a dual fixed‐bed reactor. Li₄SiO₄‐G exhibited a special Li₄SiO₄ structure with smaller crystalline nanoparticles, larger surface area, and higher CO₂ adsorption properties as compared with Li₄SiO₄‐S. The Li₄SiO₄‐G sorbent also maintained higher capacities during multiple cycles.