In this work, defect-free thin-film-composite (TFC) hollow fiber membranes containing various amino acid salts as CO2 facilitated transport carriers were fabricated via dip-coating. Four different ...amino acid salts, i.e., potassium prolinate (ProK), potassium argininate (ArgK), potassium glycinate (GlyK) and potassium cysteinate (CysK), were selected and embedded within polyvinyl alcohol (PVA) matrix. TGA, FTIR, SEM and humid mixed gas permeation test were used for the evaluation. Experiments show that adding amino acid salts into the PVA matrix significantly increases the CO2 permeance with little influence on the CO2/N2 selectivity. ProK was found the most effective within the four investigated mobile carriers; The addition of 40% ProK into the PVA matrix nearly doubled the CO2 permeance (from 399 to 791 GPU). The PVA/amino acid salt membranes also exhibited good long-term stability, in which both CO2 permeance and CO2/N2 selectivity remained nearly unchanged in a 20-h test and after a two-week shutdown period.
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•Four amino acid salts were used as mobile carriers in PVA-based membranes to enhance CO2 transport.•Defect-free TFC hollow fiber membranes with selective layer thicknesses of <500 nm were fabricated.•Lab-size hollow fiber membrane module was prepared and tested using humid mixed feed gas.•Adding amino acid salt improves the CO2 permeance significantly without sacrificing the selectivity.•The membranes show good long-term stability in the test and after a shutdown operation.
Application of conventional polymeric membranes in CO₂ separation processes are limited by the existing trade-off between permeability and selectivity represented by the renowned upper bound. ...Addition of porous nanofillers in polymeric membranes is a promising approach to transcend the upper bound, owing to their superior separation capabilities. Porous nanofillers entice increased attention over nonporous counterparts due to their inherent CO₂ uptake capacities and secondary transport pathways when added to polymer matrices. Infinite possibilities of tuning the porous architecture of these nanofillers also facilitate simultaneous enhancement of permeability, selectivity and stability features of the membrane conveniently heading in the direction towards industrial realization. This review focuses on presenting a complete synopsis of inherent capacities of several porous nanofillers, like metal organic frameworks (MOFs), Zeolites, and porous organic frameworks (POFs) and the effects on their addition to polymeric membranes. Gas permeation performances of select hybrids with these three-dimensional (3D) fillers and porous nanosheets have been summarized and discussed with respect to each type. Consequently, the benefits and shortcomings of each class of materials have been outlined and future research directions concerning the hybrids with 3D fillers have been suggested.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
Numerous studies have been reported on CO2 facilitated transport membrane synthesis, but few works have dealt with the interaction between material synthesis and transport modelling aspects for ...optimization purposes. In this work, a hybrid fixed-site carrier membrane was prepared using polyallylamine with 10 wt% polyvinyl alcohol and 0.2 wt% graphene oxide. The membrane was tested using the feed gases with different relative humidity and at different CO2 partial pressures. Selected facilitated transport models reported in the literature were used to fit the experimental data with good agreement. The key dimensionless facilitated transport parameters were obtained from the modelling and data fitting. Based on the values of these parameters, it was shown that the diffusion of the amine-CO2 reaction product was the rate-controlling step of the overall CO2 transport through the membrane. It was shown theoretically that by decreasing the membrane selective layer thickness below the actual value of 1 µm to a value of 0.1 µm, a CO2 permeance as high as 2500 GPU can be attained while maintaining the selectivity at a value of about 19. Furthermore, improving the carrier concentration by a factor of two might shift the performances above the Robeson upper bound. These potential paths for membrane performance improvement have to be confirmed by targeted experimental work.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
Urgent actions are needed to reduce CO2 emissions and mitigate the increasingly severe impacts of climate change. Since the 1990s, the membrane research group (MEMFO) at the Norwegian University of ...Science and Technology has been committed to developing effective membranes and membrane processes for CO2 separation. MEMFO's research can be categorized into five main themes: facilitated transport membranes, hybrid membranes, carbon membranes, membrane contactors, and related modeling and process simulation. These themes are tied to industrial applications in CO2 capture from flue gas, biogas upgrading, natural gas sweetening, and hydrogen purification. Promising membranes, identified based on their laboratory-scale performances, have been selected for onsite testing in industrial processes to validate their performances as well as stability and durability. Verified membranes are upscaled for pilot tests. This account paper summarizes MEMFO's research and development outcomes over the past decade and discusses our research strategies and perspectives for future work.
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Realization of suitable membrane-based technology for efficient CO2 capture to mitigate climate change relies on the development of thin-film composite (TFC) membranes with superior separation ...performance. Graphene oxide (GO), due to its 2D morphology, intrinsic strength and chemical compatibility, was used as a nanofiller to enhance CO2 separation performance and stability of a facilitated transport membrane. SHPAA (sterically hindered polyallylamine)-based blend matrix was selected as the polymeric matrix material in this work. The high aspect ratio of GO-based fillers, when coupled with optimized coating protocol, resulted in TFC membranes of ultrathin (200 nm) selective layers with the in-plane orientation of nanoplatelets, leading to enhanced separation properties that can be retained for long term. Porous graphene oxide (pGO) was also incorporated as nanofillers, resulting in significantly improved gas permeation at a very low filler loading of 0.2 wt%; A CO2 permeance of up to 607 GPU with a CO2/N2 separation factor of 36 in flat-sheet configuration was documented. Chemical modification of GO with PEG groups was found to further increase the selectivity of the membranes but reduces the CO2 permeance, showing a CO2/N2 separation factor of 90 with a CO2 permeance of 205 GPU. The effect of various 2D nanoplatelets on CO2 transport properties in the membranes of hydrophilic PVA (polyvinyl alcohol) matrix and facilitated transport SHPAA/PVA matrix was elucidated with respect to the nanofiller property and loading.
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•GO-based 2D nanoplatelets were employed as nanofillers in polymeric membranes.•SHPAA and PVA were used as polymeric matrices to study facilitated transport effect.•Hybrid TFC membranes with defect-free selective layers (~200 nm) were fabricated.•In-plane orientated 2D nanoplatelets at very low loading influences transport properties.•CO2 permeance increased due to enhanced sorption and water re-distribution resulted in by GO.
•Impact of positioning membranes of different properties in two-stage cascades is studied.•Two classes of industrially validated membranes were used as simulation basis.•Using high permeance ...membranes as bulk separator in the 1st stage is advantageous.•High selectivity in the 2nd stage helps enhancing CO2 purity.•Combinations of different membranes in two-stage process provide optimal solutions.
The use of membrane module performance data obtained in industrially-relevant environment as the basis in process simulation can lead to a more realistic prediction of a CO2 capture system. In this work, we report the use of two classes of industrially validated membranes, i.e., hybrid facilitated transport membranes (HFTMs), which are characterized by higher permeances and lower selectivity, and the fixed site carrier (FSC) polyvinylamine (PVAm) membrane, which is characterized by lower permeance and higher selectivity relative to each other, to study the potential of these membranes in two-stage configurations for post-combustion CO2 capture applications. Two-stage cascades with and without recycle streams were simulated for a target CO2 recovery of >80% and purity of 80–99.5%. Recycle systems were found to contribute in reaching high purity targets of CO2 >90% at the fixed recovery of 90%. The positioning of membranes with different properties in different stages was found to influence the performance of the system significantly. Processes employing HFTMs in the first stage coupled with a PVAm membrane in the second stage performed best with the lowest total energy/membrane area requirement and recycle ratio for a target of 90% recovery and >90% purity of CO2. The process employing HFTMs in both stages outperformed all other cases in terms of membrane area required. The case employing PVAm membranes in both stages performs at its optimum only at a lower purity requirement (<90%). This study reveals the importance of using an optimized combination of membranes with different separation capabilities at different stages.
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Membrane technology for CO2/H2 separation, especially when using CO2-selective membranes to keep H2 on the high-pressure retentate side, has been considered promising and energy-efficient for further ...H2 transport and utilization. This work prepared and optimized a CO2-selective membrane based on polyvinylamine (PVAm) with embedded graphene oxide (GO) and grafted GO for CO2/H2 separation. The facilitated transport effect of PVAm enhances CO2 transport, while the GO-based 2D nanosheets bring in a barrier effect to compensate for the high H2 diffusivity. The GO-modified surface with higher CO2 affinity also provides additional CO2 sorption sites. The membranes’ chemical structure, thermal stability, and morphology were characterized. The effects of GO and PVA-GO in the PVAm matrix and optimal loadings of GO or PVA-GO were investigated. Introducing GO into PVAm significantly increased CO2 permeance with a slight increase in CO2/H2 selectivity. While by adding 0.5 wt% PVA-GO, CO2/H2 selectivity significantly increased from 10 to 22. The selective layer thickness also greatly affects CO2/H2 separation. By increasing the coating layer thickness to approx. 11 μm, the CO2/H2 selectivity substantially increased. The separation performances of the studied membrane are far above the current CO2/H2 upper bound.
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•CO2-selective facilitated transport membranes were synthesized for CO2/H2 separation.•PVAm provides CO2-facilitated carriers and embedded GO nanosheets retard H2 diffusion.•PVA grafted GO was used to improve nanosheets' dispersion and enhance CO2 sorption.•CO2/H2 selectivity significantly increases by adding a small amount of PVA-GO.•Increasing selective layer thickness increases the CO2/H2 selectivity.
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•Pre-pilot scale hybrid facilitated transport hollow fiber membrane modules were fabricated.•Three different modules were tested using untreated real flue gas from the cement ...industry.•1.5–1.9x higher CO2 permeances compared to lab tests were documented in field tests.•Membrane modules showed long-term stability with negligible effects from impurities.•Simulation studies reveal the high potential of the membranes for CO2 capture.
Alarming increase in global CO2 emissions warrants acceleration of CO2 capture technologies. In this work, testing of pre-pilot scale membrane modules containing hybrid facilitated transport membranes in hollow fiber configuration is reported. The tests were carried out using real flue gas from a slipstream in the Colacem cement plant located in Gubbio, Italy. With the fabricated modules, CO2 flux of up to 750 NL m−2h−1 with a CO2 permeate purity ranging from 50 to 55 vol% was recorded. All pre-pilot membrane modules showed increased CO2 permeance in industrial testing (1.5 to 1.9x higher) compared to laboratory evaluation owing to the reliable water profile and high temperature of the flue gas from the chimney. Influence of operating parameters (e.g., pressures in the feed and permeate) were studied. Long-term testing showed no obvious reduction in permeation performance. Furthermore, the membranes with mobile carriers when exposed to the feed gas containing SOx and NOx exhibited good resistance to performance deterioration despite high concentrations of acidic impurities. Simulation studies based on validated experimental performance under industrial conditions reveal the high potential of the fabricated membranes as an efficient separation unit capable of achieving industrial capture rate and CO2 purity requirements using a relatively low membrane area.
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•A process using CO2-selective membranes was designed for dark fermentative bio-hydrogen purification.•The optimized two-stage process enables H2 purification of 99.5 % purity at a ...low cost of 0.156$/Nm3.•A 3rd-stage membrane is added to achieve simultaneous CO2 capture obtaining various CO2 purities.•The benefits of using H2-selective or CO2-selective membrane in the 3rd-stage is analyzed and compared.
In this work, a membrane separation process is designed and optimized to purify dark fermentative biohydrogen by removing CO2. A CO2-selective PVAm-based nanocomposite membrane was selected considering its high CO2/H2 separation performance and unique features suitable for the process. We tested the membrane performances under the separation conditions to provide a more accurate simulation basis. Several design scenarios were investigated. A two-stage process with a recycle stream is determined as the optimal design, in which the specific cost for purifying H2 to 99.5 vol% with H2 loss of <10% reaches only 0.156 $/Nm3. The techno-economic feasibility study of biohydrogen purification with simultaneous CO2 capture was also performed through an alternative design by introducing a 3rd-stage using the same membrane or an H2-selective membrane. Adding a 3rd-stage membrane can capture and purify CO2 as a side product of various purities, which further decreases the H2 loss, leading to additional economic benefits.
Membrane technology has the potential to be an eco-friendly and energy-saving solution for the separation of CO₂ from different gaseous streams due to the lower cost and the superior manufacturing ...features. However, the performances of membranes made of conventional polymers are limited by the trade-off between the permeability and selectivity. Improving the membrane performance through the addition of nanofillers within the polymer matrix offers a promising strategy to achieve superior separation performance. This review aims at providing a complete overview of the recent advances in nanocomposite membranes for enhanced CO₂ separation. Nanofillers of various dimensions and properties are categorized and effects of nature and morphology of the 0D to 2D nanofillers in the corresponding nanocomposite membranes of different polymeric matrixes are discussed with regard to the CO₂ permeation properties. Moreover, a comprehensive summary of the performance data of various nanocomposite membranes is presented. Finally, the advantages and challenges of various nanocomposite membranes are discussed and the future research and development opportunities are proposed.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
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