Recent advances in polymeric membranes for CO2 capture

Laser Patterning of Porous Support Membranes to Enhance the Effective Surface Area of Thin-Film Composite-Facilitated Transport Membranes for CO2 Separation

Although thin-film composite membranes have achieved great success in CO2 separation, further improvements in the CO2 permeance are required to reduce the size and cost of the CO2 separation process. Herein, we report the fabrication of composite membranes with high CO2 permeability using a laser-patterned porous membrane as the support membrane. High-aspect-ratio micropatterns with well-defined micropores on their surface were carved on microporous polymer supports by a direct laser writing process using a short-pulsed laser. By using a Galvano scanner and optimizing the laser conditions and target materials, in-plane micropatterns, such as microhole arrays, microline grating, microlattices, and out-of-plane hierarchical micropatterns, were created on porous membranes. An aqueous suspension of hydrogel microparticles doped with an amine-based mobile carrier was sprayed onto the patterned surface to form a defect-free thin separation layer. The surface area of the separation layer on the patterned support is up to 80% larger than that of flat pristine membranes, resulting in a 52% higher CO2 permeance (1106 GPU) with a CO2/N2 selectivity of 172. The laser-patterned porous membranes allow the development of inexpensive and high-performance functional membranes not only for CO2 separation but also for other applications, such as water treatment, cell culture, micro-TAS, and membrane reactors.

Incorporation of canola meal as a sustainable natural filler in PLA foams

The canola oil industry generates significant waste as canola meal (CM) which has limited scope and applications. This study demonstrates the possibility of valorization of CM as a sustainable natural filler in a biodegradable polymer composite of Poly(lactic acid) (PLA). Generally, interfacial bonding between natural fibers and the polymer matrix in the composite is weak and non-uniform. One possible solution is to derivatize natural fibre to introduce interfacial bond strength and compatibility with the PLA polymer matrix. Here, CM was succinylated in a reactive extrusion process using succinic anhydride at 30 wt% to get 14% derivatization with 0.02 g of -COOH density per g of CM. The CM or succinylated CM at 5 and 15 wt% was co-extruded with amorphous PLA to get composite fibers. CM-PLA and succinylated CM-PLA biocomposites were foamed using a mild and green microcellular foaming process, with CO2 as an impregnating agent without any addition of organic solvents. The properties of the foams were analyzed using differential scanning calorimetry (DSC), Dynamic mechanical thermal analysis (DMTA), shrinkage, and imaging. The addition of CM or succinylated CM as a natural filler did not significantly change the glass transition temperature, melting point, percent crystallization, stiffness, and thermal stability of PLA foams. This suggests succinylation (modification) of CM is not a mandatory step for improving interphase compatibility with the amorphous PLA. The new PLA-CM foams can be a good alternative in the packaging industry replacing the existing petroleum-based polymer foams.

Optimization of K2CO3 exposure conditions using response surface methodology for CO2 capture with 2-methylpiperazine and monoethanolamine as promoters

In this study, the optimization of potassium carbonate (K2CO3) exposure conditions for CO2 capture with the use of 2-methypiperazine (2MPz) and monoethanolamine (MEA) as promoters was investigated. The tested operating conditions for the CO2 capture process included the pH, temperature, K2CO3 dose, gas flow rate, and pressure, and their effect on the CO2 absorption/desorption rate and CO2 absorption efficiency was assessed. Response surface methodology (RSM) was also employed to determine the equations for the optimal long-term operating conditions. The results showed that the CO2 absorption rate and efficiency increased under K2CO3 exposure with an increase in the pressure and loading rate. Moreover, for the temperature the absorption efficiency first increase and then decreases with increase in temperature, however, the with increase in temperature the faster absorption were observed with lower absorption loading rate. Furthermore, pH had a more complex effect due to its variable effects on the speciation of bicarbonate ions (HCO3-) and carbonate ions (CO32-). Under higher pH conditions, there was an increase in the concentration of HCO3-, which has a higher CO2 loading capacity than CO32-. Contouring maps were also used to visualize the effect of different exposure conditions on the CO2 absorption rate and efficiency and the role of 2MPz and MEA as promoters in the K2CO3 solution for CO2 absorption. The results showed that the mean CO2 absorption rate was 6.76 × 10-4 M/L/s with an R2 of 0.9693 for the K2CO3 solution containing 2MPz. The highest absorption rate (6.56-7.20 × 10-4 M/L/s) was observed at a temperature of 298-313 K, a pressure of >2 bar, a pH of 8-9, and a loading rate of 80-120 L/h for a concentration of 1-3 M K2CO3 and 0.05-1.5 M 2MPz. The CO2 absorption efficiency exhibited a variation of 56-70% under the same conditions.

Membrane Separation Technology in Direct Air Capture

Direct air capture (DAC) is an emerging negative CO2 emission technology that aims to introduce a feasible method for CO2 capture from the atmosphere. Unlike carbon capture from point sources, which deals with flue gas at high CO2 concentrations, carbon capture directly from the atmosphere has proved difficult due to the low CO2 concentration in ambient air. Current DAC technologies mainly consider sorbent-based systems; however, membrane technology can be considered a promising DAC approach since it provides several advantages, e.g., lower energy and operational costs, less environmental footprint, and more potential for small-scale ubiquitous installations. Several recent advancements in validating the feasibility of highly permeable gas separation membrane fabrication and system design show that membrane-based direct air capture (m-DAC) could be a complementary approach to sorbent-based DAC, e.g., as part of a hybrid system design that incorporates other DAC technologies (e.g., solvent or sorbent-based DAC). In this article, the ongoing research and DAC application attempts via membrane separation have been reviewed. The reported membrane materials that could potentially be used for m-DAC are summarized. In addition, the future direction of m-DAC development is discussed, which could provide perspective and encourage new researchers' further work in the field of m-DAC.

Carbonate-Induced Structural Transformation of Lithium-Sodium Orthoborate to a Low-Viscosity Metaborate via CO2 Capture

This paper reports on the structural changes occurring within the lithium-sodium orthoborate crystal lattice during the solid-state absorption of CO2. Results derived from Fourier transform infrared measurements indicate that the CO2-saturated mixed-alkali metal orthoborate and its CO2-lean metaborate counterpart essentially present the same spectral profile, suggesting that CO2 capture results in a fundamental shift of the orthoborate composition to the metaborate one. The implications of such a structural transformation were examined in the molten state at elevated temperatures through rheological measurements, and although confirming that the CO2-lean metaborate exhibits a higher viscosity than the CO2-lean orthoborate, the results suggest that incorporation of CO2 in the orthoborate ionic lattice dilutes the melt, leading to a remarkable reduction in its overall viscosity, despite causing a structural transformation from the less viscous orthoborate form to the more viscous metaborate one.

Polymers of Intrinsic Microporosity Based on Dibenzodioxin Linkage: Design, Synthesis, Properties, and Applications

The development of polymers of intrinsic microporosity (PIMs) over the last two decades has established them as a distinct class of microporous materials, which combine the attributes of microporous solid materials and the soluble nature of glassy polymers. Due to their solubility in common organic solvents, PIMs are easily processable materials that potentially find application in membrane-based separation, catalysis, ion separation in electrochemical energy storage devices, sensing, etc. Dibenzodioxin linkage, Tröger's base, and imide bond-forming reactions have widely been utilized for synthesis of a large number of PIMs. Among these linkages, however, most of the studies have been based on dibenzodioxin-based PIMs. Therefore, this review focuses precisely on dibenzodioxin linkage chemistry. Herein, the design principles of different rigid and contorted monomer scaffolds are discussed, as well as synthetic strategies of the polymers through dibenzodioxin-forming reactions including copolymerization and postsynthetic modifications, their characteristic properties and potential applications studied so far. Towards the end, the prospects of these materials are examined with respect to their utility in industrial purposes. Further, the structure-property correlation of dibenzodioxin PIMs is analyzed, which is essential for tailored synthesis and tunable properties of these PIMs and their molecular level engineering for enhanced performances making these materials suitable for commercial usage.

Vacuum-Assisted Self-Healing Amphiphilic Copolymer Membranes for Gas Separation

Membrane gas separation provides a multitude of benefits over alternative separation techniques, especially in terms of energy efficiency and environmental sustainability. While polymeric membranes have been extensively investigated for gas separations, their self-healing capabilities have often been neglected. In this work, we have developed innovative self-healing amphiphilic copolymers by strategically incorporating three functional segments: n-butyl acrylate (BA), N-(hydroxymethyl)acrylamide (NMA), and methacrylic acid (MAA). Utilizing these three functional components, we have synthesized two distinct amphiphilic copolymers, namely, AP_NMA (PBA_x-co-PNMA_y) and AP_MAA (PBA_x-co-PMAA_y). These copolymers have been meticulously designed for gas separation applications. During the creation of these amphiphilic copolymers, BA and NMA segments were selected due to their vital role in the ease of tuning mechanical and self-healing properties. The functional groups (-OH and -NH) present on the NMA segment interact with CO₂ through hydrogen bonding, thereby boosting CO₂/N₂ separation and achieving superior selectivity. We assessed the self-healing potential of these amphiphilic copolymer membranes using two distinct strategies: conventional and vacuum-assisted self-healing. In the vacuum-assisted approach, a robust vacuum pump generates a suction force, leading to the formation of a cone-like shape in the membrane. This formation allows common fracture sites to adhere and trigger the self-healing process. As a result, AP_NMA maintains its high gas permeability and CO₂/N₂ selectivity even after the vacuum-assisted self-healing operation. The ideal CO₂/N₂ selectivity of the AP_NMA membrane aligns closely with the commercially available PEBAX-1657 membrane (17.54 vs 20.09). Notably, the gas selectivity of the AP_NMA membrane can be readily restored after damage, in contrast to the PEBAX-1657 membrane, which loses its selectivity upon damage.

Amphipathic Solvent-Assisted Synthetic Strategy for Random Lamellae of the Clinoptilolites with Flower-like Morphology and Thinner Nanosheet for Adsorption and Separation of CO2 and CH4

The random lamellae of the synthetic CP were synthesized with a hydrothermal approach using o-Phenylenediamine (OPD) as a modifier. The decreases in the order degree of the CP synthesized in the presence of the OPD resulted from the loss of long-range order in a certain direction. Subsequently, the ultrasonic treatment and washing were conducive to further facilitate the disordered arrangements of its lamellae. The possible promotion mechanism regarding the nucleation and growth behaviors of the sol-gel particles was proposed. The fractal evolutions of the aluminosilicate species with crystallization time implied that the aluminosilicate species became gradually smooth to rough during the crystallization procedures since the amorphous structures transformed into flower-like morphologies. Their gas adsorption and separation performances indicated that the adsorption capacity of CO₂ at 273 K reached up to 2.14 mmol·g^-1 at 1 bar, and the selective factor (CO₂/CH₄) up to 3.4, much higher than that of the CPs synthesized without additive OPD. The breakthrough experiments displayed a longer breakthrough time and enhancement of CO₂ uptake, showing better performance for CO₂/CH₄ separation. The cycling test further highlighted their efficiency for CO₂/CH₄ separation.

Study on the Performance of Cellulose Triacetate Hollow Fiber Mixed Matrix Membrane Incorporated with Amine-Functionalized NH2-MIL-125(Ti) for CO2 and CH4 Separation

The increase in the global population has caused an increment in energy demand, and therefore, energy production has to be maximized through various means including the burning of natural gas. However, the purification of natural gas has caused CO2 levels to increase. Hollow fiber membranes offer advantages over other carbon capture technologies mainly due to their large surface-to-volume ratio, smaller footprint, and higher energy efficiency. In this work, hollow fiber mixed matrix membranes (HFMMMs) were fabricated by utilizing cellulose triacetate (CTA) as the polymer and amine-functionalized metal-organic framework (NH2-MIL-125(Ti)) as the filler for CO2 and CH4 gas permeation. CTA and NH2-MIL-125(Ti) are known for exhibiting a high affinity towards CO2. In addition, the utilization of these components as membrane materials for CO2 and CH4 gas permeation is hardly found in the literature. In this work, NH2-MIL-125(Ti)/CTA HFMMMs were spun by varying the air gap ranging from 1 cm to 7 cm. The filler dispersion, crystallinity, and functional groups of the fabricated HFMMMs were examined using EDX mapping, SEM, XRD, and FTIR. From the gas permeation testing, it was found that the NH2-MIL-125(Ti)/CTA HFMMM spun at an air gap of 1 cm demonstrated a CO2/CH4 ideal gas selectivity of 6.87 and a CO2 permeability of 26.46 GPU.

Critical Assessment of Membrane Technology Integration in a Coal-Fired Power Plant

Despite the many technologies for CO₂ capture (e.g., chemical or physical absorption or adsorption), researchers are looking to develop other technologies that can reduce CAPEX and OPEX costs as well as the energy requirements associated with their integration into thermal power plants. The aim of this paper was to analyze the technical and economic integration of spiral wound membranes in a coal-fired power plant with an installed capacity of 330 MW (the case of the Rovinari power plant-in Romania). The study modeled energy processes using CHEMCAD version 8.1 software and polymer membranes developed in the CO₂ Hybrid research project. Thus, different configurations such as a single membrane step with and without the use of a vacuum pump and two membrane steps placed in series were analyzed. In all cases, a compressor placed before the membrane system was considered. The use of two serialized stages allows for both high efficiency (minimum 90%) and CO₂ purity of a minimum of 95%. However, the overall plant efficiency decreased from 45.78 to 23.96% and the LCOE increased from 75.6 to 170 €/kWh. The energy consumption required to capture 1 kg of CO₂ is 2.46 MJ_el and 4.52 MJ_th.

CO2 Capture and Low-Temperature Release by Poly(aminoethyl methacrylate) and Derivatives

Poly(aminoethyl methacrylate) (PAEMA), poly(ethylene oxide)-block-(aminoethyl methacrylate) (PEO-PAEMA), and their guanidinylated derivates, poly(guanidine ethyl methacrylate) (PGEMA) and poly(ethylene oxide)-block-(guanidine ethyl methacrylate) (PEO-PGEMA), were prepared to study their capabilities for CO₂ adsorption and release. The polymers of different forms or degree of guanidinylation were thoroughly characterized, and their interaction with CO₂ was studied by NMR and calorimetry. The extent and kinetics of adsorption and desorption of N₂ and CO₂ were investigated by thermogravimetry under controlled gas atmospheres. The materials did not adsorb N₂, whereas CO₂ could be reversibly adsorbed at room temperature and released by an elevated temperature. The most promising polymer was PGEMA with a guanidinylation degree of 7% showing a CO₂ adsorption capacity of 2.4 mmol/g at room temperature and a desorption temperature of 72 °C. The study also revealed relations between the polymer chemical composition and CO₂ adsorption and release characteristics that are useful in future formulations for CO₂ adsorbent polymer materials.

Development of Amine-Functionalized Metal-Organic Frameworks Hollow Fiber Mixed Matrix Membranes for CO2 and CH4 Separation: A Review

CO₂ separation from raw natural gas can be achieved through the use of the promising membrane-based technology. Polymeric membranes are a known method for separating CO₂ but suffer from trade-offs between its permeability and selectivity. Therefore, through the use of mixed matrix membranes (MMMs) which utilizes inorganic or hybrid fillers such as metal-organic frameworks (MOFs) in polymeric matrix, the permeability and selectivity trade-off can be overcome and possibly surpass the Robeson Upper Bounds. In this study, various types of MOFs are explored in terms of its structure and properties such as thermal and chemical stability. Next, the use of amine and non-amine functionalized MOFs in MMMs development are compared in order to investigate the effects of amine functionalization on the membrane gas separation performance for flat sheet and hollow fiber configurations as reported in the literature. Moreover, the gas transport properties and various challenges faced by hollow fiber mixed matrix membranes (HFMMMs) are discussed. In addition, the utilization of amine functionalization MOF for mitigating the challenges faced is included. Finally, the future directions of amine-functionalized MOF HFMMMs are discussed for the fields of CO₂ separation.

Recent Advances in Molten-Carbonate Membranes for Carbon Dioxide Separation: Focus on Material Selection, Geometry, and Surface Modification

Membranes for carbon dioxide permeation have been recognized as potential candidates for CO₂ separation technology, particularly in the energy sector. Supported molten-salt membranes provide ionic routes to facilitate carbon dioxide transport across the membrane, permit the use of membrane at higher temperature, and offer selectivity based on ionic affinity of targeted compound. In this review, molten-carbonate ceramic membranes have been evaluated for CO₂ separation. Various research studies regarding mechanisms of permeation, properties of molten salt, significance of material selection, geometry of support materials, and surface modifications have been assessed with reference to membrane stabilities and operational flux rates. In addition, the outcomes of permeation experiments, stability tests, selection of the compatible materials, and the role of interfacial reactions for membrane degradation have also been discussed. At the end, major challenges and possible solutions are highlighted along with future recommendations for fabricating efficient carbon dioxide separation membranes.

CO2-selective poly (ether-block-amide)/polyethylene glycol composite blend membrane for CO2 separation from gas mixtures

This work focuses on the preparation of composite blend membranes based on poly (ether-block-amide) (Pebax-1657) by incorporating polyethylene glycol (PEG) for gas separation applications. The influence of PEG with different molecular weights (PEG600, PEG1500, and PEG4000) at loading content in the range of 10%wt. to 40%wt. was investigated on the microstructure and gas separation performance of the prepared blend membranes. The fabricated membranes were characterized using SEM, XRD, and water contact angle analyses. Based on the experimental results, the blending of low molecular weight PEG (PEG600) into the Pebax-1657 matrix increased the chain mobility of the membrane, led to a smooth microstructure, and improved the hydrophilicity of the blend membranes, as well as enhanced the gas permeability of N₂, O₂, CH₄, and CO₂, but only slightly affected the ideal selectivity of O₂/N₂, CH₄/N₂, CO₂/N₂, and CO₂/CH₄. In contrast, the incorporation of PEG1500 and PEG4000 meaningfully increased the membrane crystallinity, decreased chain mobility, resulted in a rough microstructure, and reduced the blend membranes' hydrophilicity. For CO₂/N₂ mixture, the Pebax/40%PEG600 membrane had CO₂ permeability of 62.9 Barrer and selectivity of 83.8, while the Pebax/20%PEG600 showed the CO₂ permeability of 63.12 Barrer and selectivity of 23.6 for CO₂/CH₄ separation.

Advances in the Use of Nanocomposite Membranes for Carbon Capture Operations

The adoption of nanodoped membranes in the areas of gas stream separation, water, and wastewater treatments due to the physical and operational advantages of such membranes has significantly increased. The literature has shown that the surface structure and physicochemical properties of nanodoped membranes contribute significantly to the interaction and rejection characteristics when compared to bare membranes. This study reviews the recent developments on nanodoped membranes, and their hybrids for carbon capture and gas separation operations. Features such as the nanoparticles/materials and hybrids used for membrane doping and the effect of physicochemical properties and water vapour in nanodoped membrane performance for carbon capture are discussed. The highlights of this review show that nanodoped membrane is a facile modification technique which improves the membrane performance in most cases and holds a great potential for carbon capture. Membrane module design and material, thickness, structure, and configuration were identified as key factors that contribute directly, to nanodoped membrane performance. This study also affirms that the three core parameters satisfied before turning a microporous material into a membrane are as follows: high permeability and selectivity, ease of fabrication, and robust structure. From the findings, it is also observed that the application of smart models and knowledge-based systems have not been extensively studied in nanoparticle-/material-doped membranes. More studies are encouraged because technical improvements are needed in order to achieve high performance of carbon capture using nanodoped membranes, as well as improving their durability, permeability, and selectivity of the membrane.

Interfacial Design of Mixed Matrix Membranes via Grafting PVA on UiO-66-NH2 to Enhance the Gas Separation Performance

In this study, defect-free facilitated transport mixed matrix membrane (MMM) with high loading amount of UiO-66-NH2 nanoparticles as metal-organic frameworks (MOFs) was fabricated. The MOFs were covalently bonded with poly (vinyl alcohol) (PVA) to incorporate into a poly (vinyl amine) (PVAm) matrix solution. A uniform UiO-66-NH2 dispersion up to 55 wt.% was observed without precipitation and agglomeration after one month. This can be attributed to the high covalent interaction at interfaces of UiO-66-NH2 and PVAm, which was provided by PVA as a functionalized organic linker. The CO2 permeability and CO2/N2 and selectivity were significantly enhanced for the fabricated MMM by using optimal fabrication parameters. This improvement in gas performance is due to the strong impact of solubility and decreasing diffusion in obtained dense membrane to promote CO2 transport with a bicarbonate reversible reaction. Therefore, the highest amount of amine functional groups of PVAm among all polymers, plus the abundant amount of amines from UiO-66-NH2, facilitated the preferential CO2 permeation through the bicarbonate reversible reaction between CO2 and -NH2 in humidified conditions. XRD and FTIR were employed to study the MMM chemical structure and polymers-MOF particle interactions. Cross-sectional and surface morphology of the MMM was observed by SEM-EDX and 3D optical profilometer to detect the dispersion of MOFs into the polymer matrix and explore their interfacial morphology. This approach can be extended for a variety of polymer-filler interfacial designs for gas separation applications.

Understanding the Effect of Water on CO2 Adsorption

Carbon capture from large sources and ambient air is one of the most promising strategies to curb the deleterious effect of greenhouse gases. Among different technologies, CO₂ adsorption has drawn widespread attention mostly because of its low energy requirements. Considering that water vapor is a ubiquitous component in air and almost all CO₂-rich industrial gas streams, understanding its impact on CO₂ adsorption is of critical importance. Owing to the large diversity of adsorbents, water plays many different roles from a severe inhibitor of CO₂ adsorption to an excellent promoter. Water may also increase the rate of CO₂ capture or have the opposite effect. In the presence of amine-containing adsorbents, water is even necessary for their long-term stability. The current contribution is a comprehensive review of the effects of water whether in the gas feed or as adsorbent moisture on CO₂ adsorption. For convenience, we discuss the effect of water vapor on CO₂ adsorption over four broadly defined groups of materials separately, namely (i) physical adsorbents, including carbons, zeolites and MOFs, (ii) amine-functionalized adsorbents, and (iii) reactive adsorbents, including metal carbonates and oxides. For each category, the effects of humidity level on CO₂ uptake, selectivity, and adsorption kinetics under different operational conditions are discussed. Whenever possible, findings from different sources are compared, paying particular attention to both similarities and inconsistencies. For completeness, the effect of water on membrane CO₂ separation is also discussed, albeit briefly.

Mechanism and Compatibility of Pretreated Lignocellulosic Biomass and Polymeric Mixed Matrix Membranes: A Review

In this paper, a review of the compatibility of polymeric membranes with lignocellulosic biomass is presented. The structure and composition of lignocellulosic biomass which could enhance membrane fabrications are considered. However, strong cell walls and interchain hindrances have limited the commercial-scale applications of raw lignocellulosic biomasses. These shortcomings can be surpassed to improve lignocellulosic biomass applications by using the proposed pretreatment methods, including physical and chemical methods, before incorporation into a single-polymer or copolymer matrix. It is imperative to understand the characteristics of lignocellulosic biomass and polymeric membranes, as well as to investigate membrane materials and how the separation performance of polymeric membranes containing lignocellulosic biomass can be influenced. Hence, lignocellulosic biomass and polymer modification and interfacial morphology improvement become necessary in producing mixed matrix membranes (MMMs). In general, the present study has shown that future membrane generations could attain high performance, e.g., CO2 separation using MMMs containing pretreated lignocellulosic biomasses with reachable hydroxyl group radicals.

Recent Progress in the Engineering of Polymeric Membranes for CO2 Capture from Flue Gas

CO2 capture from coal- or natural gas-derived flue gas has been widely considered as the next opportunity for the large-scale deployment of gas separation membranes. Despite the tremendous progress made in the synthesis of polymeric membranes with high CO2/N2 separation performance, only a few membrane technologies were advanced to the bench-scale study or above from a highly idealized laboratory setting. Therefore, the recent progress in polymeric membranes is reviewed in the perspectives of capture system energetics, process synthesis, membrane scale-up, modular fabrication, and field tests. These engineering considerations can provide a holistic approach to better guide membrane research and accelerate the commercialization of gas separation membranes for post-combustion carbon capture.

Amine-Containing Membranes with Functionalized Multi-Walled Carbon Nanotubes for CO2/H2 Separation

Amine-containing mixed-matrix membranes incorporated with amino-functionalized multi-walled carbon nanotubes (AF-MWNTs) were synthesized for CO₂/H₂ separation based on the facilitated transport mechanism. AF-MWNTs were chosen primarily as the mechanical reinforcing filler to enhance the membrane stability. At 107 °C and 0.2-MPa feed pressure, the membrane incorporated with 10 wt.% AF-MWNTs showed a CO₂ permeability of 3196 Barrers and a CO₂/H₂ selectivity of 205. At the higher feed pressure of 1.5 MPa, owing to the carrier saturation phenomenon, the same membrane exhibited reduced transport performance with a CO₂ permeability of 776 Barrers and a CO₂/H₂ selectivity of 31. These separation performances at both the low and high feed pressures were well above the theoretical upper bound. Furthermore, the incorporation of 10 wt.% AF-MWNTs led to a significant improvement on membrane stability. The transport performance and selective layer thickness of this membrane maintained for 100 h, which suggested that the incorporation of AF-MWNTs improved the resistance to membrane compaction upon a high feed pressure. Therefore, this work is considered as one of the crucial steps to enable the application of facilitated transport membranes to high-pressure gas processing such as syngas purification.

Pebax® 2533/Graphene Oxide Nanocomposite Membranes for Carbon Capture

In this work, the behavior of new GO-based mixed matrix membranes was tested in view of their use as CO₂-selective membrane in post combustion carbon capture applications. In particular, the new materials were obtained by mixing of Pebax^® 2533 copolymer with different types of graphene oxide (GO). Pebax^® 2533 has indeed lower selectivity, but higher permeability than Pebax^® 1657, which is more commonly used for membranes, and it could therefore benefit from the addition of GO, which is endowed with very high selectivity of CO₂ with respect to nitrogen. The mixed matrix membranes were obtained by adding different amounts of GO, from 0.02 to 1% by weight, to the commercial block copolymers. Porous graphene oxide (PGO) and GO functionalized with polyetheramine (PEAGO) were also considered in composites produced with similar procedure, with a loading of 0.02%wt. The obtained films were then characterized by using SEM, DSC, XPS analysis and permeability experiments. In particular, permeation tests with pure CO₂ and N₂ at 35°C and 1 bar of upstream pressure were conducted for the different materials to evaluate their separation performance. It has been discovered that adding these GO-based nanofillers to Pebax^® 2533 matrix does not improve the ideal selectivity of the material, but it allows to increase CO₂ permeability when a low filler content, not higher than 0.02 wt%, is considered. Among the different types of GO, then, porous GO seems the most promising as it shows CO₂ permeability in the order of 400 barrer (with an increase of about 10% with respect to the unloaded block copolymer), obtained without reducing the CO₂/N₂ selectivity of the materials, which remained in the order of 25.

Surface Modifications of Nanofillers for Carbon Dioxide Separation Nanocomposite Membrane

CO2 separation is an important process for a wide spectrum of industries including petrochemical, refinery and coal-fired power plant industries. The membrane-based process is a promising operation for CO2 separation owing to its fundamental engineering and economic benefits over the conventionally used separation processes. Asymmetric polymer–inorganic nanocomposite membranes are endowed with interesting properties for gas separation processes. The presence of nanosized inorganic nanofiller has offered unprecedented opportunities to address the issues of conventionally used polymeric membranes. Surface modification of nanofillers has become an important strategy to address the shortcomings of nanocomposite membranes in terms of nanofiller agglomeration and poor dispersion and polymer–nanofiller incompatibility. In the context of CO2 gas separation, surface modification of nanofiller is also accomplished to render additional CO2 sorption capacity and facilitated transport properties. This article focuses on the current strategies employed for the surface modification of nanofillers used in the development of CO2 separation nanocomposite membranes. A review based on the recent progresses made in physical and chemical modifications of nanofiller using various techniques and modifying agents is presented. The effectiveness of each strategy and the correlation between the surface modified nanofiller and the CO2 separation performance of the resultant nanocomposite membranes are thoroughly discussed.

Materials and logistics for carbon dioxide capture, storage and utilization

The efforts to curtail carbon dioxide presence in the atmosphere are a strong function of the available technologies to capture, store and usefully utilize it. Materials with adequate CO₂ sorption kinetics that are both effective and economical are of prime importance for the whole capture system to be built around. This work identifies such materials that are currently used in CO₂ adsorption beds/columns at different global locations, along with their vital operational parameters, logistics and costs. Three main classes of materials currently in use to that end are discussed in detail here, namely solid sorbents, advanced solvents membrane systems. These materials are then compared in terms of their potential CO₂ uptake, operating parameters and ease of use and implementation of the respective technology. Tabular data are appended to each technology covered with the most relevant advantages and disadvantages. With such comprehensive survey of the recent state-of-the-art materials, recommendations are also made to facilitate the selection of systems based on their CO₂ yield, price and suitability to the geographical location.