Membranes For CO2 Capture Research Articles

Recent advances in polymeric membranes for CO2 capture

Abstract Membrane and membrane process have been considered as one of the most promising technologies for mitigating CO2 emissions from the use of fossil fuels. In this paper, recent advances in polymeric membranes for CO2 capture are reviewed in terms of material design and membrane formation. The selected polymeric materials are grouped based on their gas transport mechanisms, i.e., solution‐diffusion and facilitated transport. The discussion of solution‐diffusion membranes encompasses the recent efforts to shift the upper bound barrier, including the enhanced CO2 solubility in several rubbery polymers and novel methods to construct shape-persisting macromolecules with unprecedented sieving ability. The carrier-bearing facilitated transport membranes are categorized based on the specific CO2-carrier chemistry. Finally, opportunities and challenges in practical applications are also discussed, including post-combustion carbon capture (CO2/N2), hydrogen purification (CO2/H2), and natural gas sweetening (CO2/CH4).

Amine-impregnated porous nanofiber membranes for CO2 capture

Global warming is a worldwide issue, mainly caused by excessive emission of carbon dioxide (CO2), thus, demands the development of robust and flexible sorbents with consider CO2 capturing capacity. Herein, we report an easy and facile two-step fabrication of hierarchically structured and highly porous polystyrene (PS)/polyurethane (PU) electrospun nanofiber membrane impregnated with various amines for post-combustion CO2 capture. Synthesized porous nanofiber membranes have highly flexible and strong mechanical characteristics. The comparative analysis of porous membranes functionalized with three functional amines shows that low molecular weight polyethyleneimine (PEIL) impregnated porous nanofiber membranes offer relatively higher CO2 adsorption (1.64 mmol/g) at 40 °C. In addition, optimized samples exhibit excellent regenerability, (≥ 90% of their original value) even after 19 adsorption-desorption cycles showing a stable and durable CO2 capture performance. This work paves the way for developing electrospun nanofiber membranes capable of efficient CO2 adsorption.

Scale-up of amine-containing thin-film composite membranes for CO2 capture from flue gas

Membrane technology is a cost-effective and energy-efficient separation process for CO2 removal from flue gas. Recently, there have been remarkable advances in the development of polyvinylamine (PVAm)/piperazine glycinate (PG)-containing facilitated transport membranes for CO2 removal. The advanced PVAm/PG-containing membranes have demonstrated desirably high CO2/N2 selectivity of greater than 140 and good CO2 permeance of > 700 GPU (1 GPU = 10−6 cm3 (STP)/(s cm2 cmHg)) at the typical flue gas temperature of 57 °C. This work investigated the scale-up fabrication of the PVAm/PG-containing membranes and demonstrated it successfully. Effective and efficient continuous fabrication of the membranes in a roll-to-roll manner was developed using the thin-film coating (TFC) assembly of the pilot-scale machine at Ohio State. The design of the TFC assembly was improved and several operating parameters were optimized for the fabrication with desirable membrane thickness and gas transport performance. A total of > 2000 feet long and 14-in. wide membranes with a selective layer thickness of < 200 nm was successfully fabricated. In addition, small representative samples taken from the scale-up membranes were tested, showing the CO2 permeance and CO2/N2 selectivity at 57 °C in reasonably good agreement with those obtained from the lab-synthesized membranes.

Pursuit of efficient CO2-capture membranes: graphene oxide- and MOF-integrated Ultrason® membranes

High-performance mixed-matrix membranes (MMMs) were developed to help control the global warming by capturing and sequestrating carbon dioxide (CO2) from post combustion flue gas originating from burning of fossil fuels. MMMs of different compositions were prepared by synergistically doping glassy polymer Ultrason® S 6010 (US) with nanosheets of graphene oxide (GO) and nanocrystals of zeolitic imidazolate frameworks (ZIF-300) in varying degrees. Solution-casting technique was used to fabricate various MMMs to optimize their CO2 capturing performance from a CO2-enriched gas mixture. The prepared composite membranes indicated enhanced filler–polymer interfacial adhesion, consistent distribution of nanofillers, and thermally stable matrix configuration. Owing to the synergistic effect of incorporated nanofillers, CO2 permeability, and CO2/N2 permselectivity of the membranes were enhanced as demonstrated by gas sorption and permeation experiments. As compared to neat Ultrason® membrane, CO2 permeability and CO2/N2 ideal selectivity of fabricated MMMs doped with 30 wt% ZIF-300 nanocrystals and 1 wt% GO nanosheets were considerably improved. Key features of the fabricated MMMs include their structural and thermal stability coupled with improved gas separation performance.

Fabrication of ultra-performance non-compact graphene/carbon hollow fibers/graphene stationary junction like membrane for CO2-Capture

Ultra-performance non-compact Graphene/Carbon Hollow Fibers/Graphene ∼(G/CHF/G) junction like membrane was successfully fabricated by chemical vapor deposition (CVD) of graphene on the two sides of carbon fibers pellet of with thickness of 6 mm. Mono-, bi-junction and tri-units junction membranes were loaded in column with specific parameters suitable for junction size. The column was made from special glass with controlled in/outlet stopper. The adsorption capacities of Mono-, bi-junction and tri-units junction like membranes were measured from adsorption isotherm at 25 °C and found to be 76, 93 and 117 mmol. CO2/gm G/CHF/G respectively. These promising results are attributable to G/CHF/G junction like membrane has ultra-high surface area coupled with mesoporous structure. Furthermore compactness of graphene layers with thickness average 67.5 Å on the surface of carbon hollow fibers act as true membrane reinforced by adsorption on cavities of carbon hollow fibers.

Permeability and Selectivity of PPO/Graphene Composites as Mixed Matrix Membranes for CO₂ Capture and Gas Separation.

We fabricated novel composite (mixed matrix) membranes based on a permeable glassy polymer, Poly(2,6-dimethyl-1,4-phenylene oxide) (PPO), and variable loadings of few-layer graphene, to test their potential in gas separation and CO2 capture applications. The permeability, selectivity and diffusivity of different gases as a function of graphene loading, from 0.3 to 15 wt %, was measured at 35 and 65 °C. Samples with small loadings of graphene show a higher permeability and He/CO2 selectivity than pure PPO, due to a favorable effect of the nanofillers on the polymer morphology. Higher amounts of graphene lower the permeability of the polymer, due to the prevailing effect of increased tortuosity of the gas molecules in the membrane. Graphene also allows dramatically reducing the increase of permeability with temperature, acting as a “stabilizer” for the polymer matrix. Such effect reduces the temperature-induced loss of size-selectivity for He/N2 and CO2/N2, and enhances the temperature-induced increase of selectivity for He/CO2. The study confirms that, as observed in the case of other graphene-based mixed matrix glassy membranes, the optimal concentration of graphene in the polymer is below 1 wt %. Below such threshold, the morphology of the nanoscopic filler added in solution affects positively the glassy chains packing, enhancing permeability and selectivity, and improving the selectivity of the membrane at increasing temperatures. These results suggest that small additions of graphene to polymers can enhance their permselectivity and stabilize their properties.

Life cycle analysis of a combined CO2 capture and conversion membrane reactor

This paper reports a life cycle analysis of a combined CO2 capture and conversion “all-in-one” membrane reactor system. The reactor is composed of a high-temperature mixed electronic and carbonate-ion conductor (MECC) membrane for CO2 capture and a solid oxide electrolysis cell (SOEC) for CO2/H2O co-reduction. The results show that the parasitic energy (PE) using MECC membrane to capture CO2 is 321kJ for every kilogram CO2 captured, less than half of the consumption of the stat-of the-art MEA plant. The energy efficiency of the combined system can reach 82%. A cost analysis further shows that the cost of electricity dictates the price of synthetic fuel produced by the reactor at a lower SOEC area (lower capital cost), while both electricity cost and SOEC capital cost play an important role for higher SOEC area (higher capital cost). Finally, the synthetic fuel produced from Ag-based MECC and NiO-based MECC capture/conversion systems are comparable to that of biomass derived liquids (carbon neutral) when the electricity cost is < $0.059/kWh and < $0.096/kWh, respectively.

Development of robust fluorinated TiO2/PVDF composite hollow fiber membrane for CO2 capture in gas-liquid membrane contactor

Gas-liquid membrane contactor (GLMC) is a promising method to attain high efficiency for CO2 capture from flue gas, biogas and natural gas. However, membranes used in GLMC are prone to pore wetting due to insufficient hydrophobicity and low chemical resistance, resulting in significant increase in mass transfer resistance. To mitigate this issue, inorganic-organic fluorinated titania/polyvinylidene fluoride (fTiO2/PVDF) composite hollow fiber (HF) membranes was prepared via facile in-situ vapor induced hydrolyzation method, followed by hydrophobic modification. The proposed composite membranes were expected to couple the superb chemical stability of inorganic and high permeability/low cost of organic materials. The continuous fTiO2 layer deposited on top of PVDF substrate was found to possess a tighter microstructure and better hydrophobicity, which effectively prevented the membrane from wetting and lead to a high CO2 absorption flux (12.7 × 10−3 mol m−2 s−1). In a stability test with 21-day operation of GLMC using 1M monoethanolamine (MEA) as the absorbent, the fTiO2/PVDF membrane remained to be intact with a CO2 absorption flux decline of ∼16%, while the pristine PVDF membrane suffered from a flux decline of ∼80% due to membrane damage. Overall, this work provides an insight into the preparation of high-quality inorganic/organic composite HF membranes for CO2 capture in GLMC application.

Ultrathin graphene oxide-based hollow fiber membranes with brush-like CO2-philic agent for highly efficient CO2 capture

Among the current CO2 capture technologies, membrane gas separation has many inherent advantages over other conventional techniques. However, fabricating gas separation membranes with both high CO2 permeance and high CO2/N2 selectivity, especially under wet conditions, is a challenge. In this study, sub-20-nm thick, layered graphene oxide (GO)-based hollow fiber membranes with grafted, brush-like CO2-philic agent alternating between GO layers are prepared by a facile coating process for highly efficient CO2/N2 separation under wet conditions. Piperazine, as an effective CO2-philic agent, is introduced as a carrier-brush into the GO nanochannels with chemical bonding. The membrane exhibits excellent separation performance under simulated flue gas conditions with CO2 permeance of 1,020 GPU and CO2/N2 selectivity as high as 680, demonstrating its potential for CO2 capture from flue gas. We expect this GO-based membrane structure combined with the facile coating process to facilitate the development of ultrathin GO-based membranes for CO2 capture.

High-Performance Self-Cross-Linked PGP–POEM Comb Copolymer Membranes for CO2 Capture

We report a high performance CO2 capture membrane based on the copolymerization and self-cross-linking of poly(glycidyl methacrylate-g-poly(propylene glycol))-co-poly(oxyethylene methacrylate) (PGP–POEM) comb copolymer. The epoxide–amine reaction is responsible for the self-cross-linking reaction, which takes place under mild conditions without any additional cross-linkers or catalysts. The effects of self-cross-linking on the membrane properties are investigated by comparing the copolymers with those containing a low PPG grafting density (l-PGP–POEM). Furthermore, the gas separation performance of the membranes is systematically investigated as a function of POEM content in the comb copolymer. Both the permeance and selectivity of the PGP–POEM membranes are enhanced simultaneously with increase in the POEM content up to 51.2 wt % (PGP–POEM13), at which the best performance was achieved among the membranes. The high performance results from the reduced diffusion of N2 due to the self-cross-linked structur...

Dual-Channel, Molecular-Sieving Core/Shell ZIF@MOF Architectures as Engineered Fillers in Hybrid Membranes for Highly Selective CO2 Separation.

A novel core/shell porous crystalline structure was prepared using a large pore metal organic framework (MOF, UiO-66-NH2, pore size, ∼ 0.6 nm) as core surrounded by a small pore zeolitic imidazolate framework (ZIF, ZIF-8, pore size, ∼ 0.4 nm) through a layer-by-layer deposition method and subsequently used as an engineered filler to construct hybrid polysulfone (PSF) membranes for CO2 capture. Compared to traditional fillers utilizing only one type of porous material with rigid channels (either large or small), our custom designed core/shell fillers possess clear advantages via pore engineering: the large internal channels of the UiO-66-NH2 MOFs create molecular highways to accelerate molecular transport through the membrane, while the thin shells with small pores (ZIF-8) or even smaller pores generated at the interface by the imperfect registry between the overlapping pores of ZIF and MOF enhance molecular sieving thus serving to distinguish slightly larger N2 molecules (kinetic diameter, 0.364 nm) from smaller CO2 molecules (kinetic diameter, 0.33 nm). The resultant core/shell ZIF@MOF and as-prepared hybrid PSF membranes were characterized by transmission electron microscopy, X-ray diffraction, wide-angle X-ray scattering, scanning electron microscopy, Fourier transform infrared, thermogravimetric analysis, differential scanning calorimetry, and contact angle tests. The dependence of the separation performance of the membranes on the MOF/ZIF ratio was also studied by varying the number of layers of ZIF coatings. The integrated PSF-ZIF@MOF hybrid membrane (40 wt % loading) with optimized ZIF coating cycles showed improved hydrophobicity and excellent CO2 separation performance by simultaneously increasing CO2 permeability (CO2 permeability of 45.2 barrer, 710% higher than PSF membrane) and CO2/N2 selectivity (CO2/N2 selectivity of 39, 50% higher than PSF membrane), which is superior to most reported hybrid PSF membranes. The strategy of using dual-channel molecular sieving core/shell porous crystals in hybrid membranes thus provides a promising means for CO2 capture from flue gas.

Pilot testing on fixed-site-carrier membranes for CO2 capture from flue gas

One way of contributing to combat the climate change is to capture CO2 from fossil fuel flue gases, and utilize CO2 as feedstocks or store underground. Membranes will for sure represent one of the emerging technologies to be used for CO2 capture. In this work, a pilot installation using polyvinylamine (PVAm) based fixed-site-carrier (FSC) hollow fiber membranes at the Tiller plant (Trondheim, Norway) was reported with the possibility to vary the feed CO2 concentration over a range of 9.5–12.4vol.%. The semi-commercial scale hollow fiber polysulfone support modules were coated with PVAm in-situ. The pilot tests were performed with two modules in parallel in a single stage process, and the operating parameters such as feed and permeate pressure, temperature, feed flow, operation mode, etc. were investigated. The testing results indicated that a 60 vol.% CO2 purity could be achieved in the permeate from a 9.5vol.% CO2 in feed flue gas. Moreover, the water permeation through the FSC membrane was also studied. Engineering design on process and module was likewise discussed. The results from this one stage process give the basis for an optimized two stage process for CO2 capture at a set goal for capture ratio.

Porous graphene nanosheets functionalized thin film nanocomposite membrane prepared by interfacial polymerization for CO2/N2 separation

The inherent defects of porous graphene (PG) formed during reduction etching process could serve as nanopores, making PG emerge a potential application for the preparation of micrometre-sized separation membranes. Here, we introduced PG as inorganic nanofiller to fabricate thin film nanocomposite (TFN) membranes for CO2 capture via interfacial polymerization technique. The PG selective nanolayers not only possessed a good adhesion with polymers but also benefited from hydrogen bonding actions, simultaneously, thus ensuring the formation of high-efficiency molecular sieving passageway in the separation layer of membranes. Furthermore, the thin PG nanosheets were verified to have an significantly affect for permeability and selectivity of membranes (PG, 0.05wt%, 1bar), with exhibiting about 21% and 20.8% enhancement of the CO2 permeance and the CO2/N2 selectively compared to that of the membrane without PG separately. Simultaneously, the membrane also showed higher stability and the porous surface morphology of PG shortened greatly the gas transfer path. The approach offers a potential promising to exploit the ultra-thin film composite membrane for efficient gas separation.

Facile synthesis of a nitrogen-doped carbon membrane for CO2 capture

A controllable one-pot method to synthesize a nitrogen-doped carbon membrane by pyrolysis of urea/novalac resin composite on a green novalac resin support is reported. The microporosity was increased by decomposition of the urea during pyrolysis without post-treatment. Further, the presence of nitrogen in the resulting carbon membrane significantly increased the CO2 adsorption capacity of carbon membrane, which led to a reduction in CO2 permeance. The carbon membrane showed high H2 and N2 permeances of 4.2×10−6 and 0.74×10−6molm−2s−1Pa−1, and moderate H2/CO2 and N2/CO2 ideal selectivities of 9.2 and 1.6, respectively. This carbon membrane may have potential applications for efficient CO2 capture from industrial mixtures at high temperatures.

Ionic-Liquid-Based CO2 Capture Systems: Structure, Interaction and Process.

The inherent structure tunability, good affinity with CO2, and nonvolatility of ionic liquids (ILs) drive their exploration and exploitation in CO2 separation field, and has attracted remarkable interest from both industries and academia. The aim of this Review is to give a detailed overview on the recent advances on IL-based materials, including pure ILs, IL-based solvents, and IL-based membranes for CO2 capture and separation from the viewpoint of molecule to engineering. The effects of anions, cations and functional groups on CO2 solubility and selectivity of ILs, as well as the studies on degradability of ILs are reviewed, and the recent developments on functionalized ILs, IL-based solvents, and IL-based membranes are also discussed. CO2 separation mechanism with IL-based solvents and IL-based membranes are explained by combining molecular simulation and experimental characterization. Taking into consideration of the applications and industrialization, the recent achievements and developments on the transport properties of IL fluids and the process design of IL-based processes are highlighted. Finally, the future research challenges and perspectives of the commercialization of CO2 capture and separation with IL-based materials are posed.

Preferential CO2 Separation Over Nitrogen by a Free-standing and Nanometer-thick Membrane

Membrane thinning is important approach to enhance gas permeation properties of CO2 capture membranes. We employed cross linkable polymer materials, conventional epoxy resin containing amino groups, for the preparation of free-standing and ultrathin nanomembrane. By simple spincoating, nanometer-thick epoxy membranes were fabricated and detached as a free-standing membrane. The thickness of a membrane was readily controllable by spincoating speed and polymer concentration. Although as-prepared nanomembrane did not show CO2 selectivity over N2, wet membrane shows high CO2 selectively. Further sophistication of membrane material design and reduction of membrane thickness would be a promising approach to prepare preferential CO2 separation membrane with high gas flux.

Enhanced selectivity in mixed matrix membranes for CO2 capture through efficient dispersion of amine-functionalized MOF nanoparticles

Mixed matrix membranes (MMMs) for gas separation applications have enhanced selectivity when compared with the pure polymer matrix, but are commonly reported with low intrinsic permeability, which has major cost implications for implementation of membrane technologies in large-scale carbon capture projects. High-permeability polymers rarely generate sufficient selectivity for energy-efficient CO2 capture. Here we report substantial selectivity enhancements within high-permeability polymers as a result of the efficient dispersion of amine-functionalized, nanosized metal–organic framework (MOF) additives. The enhancement effects under optimal mixing conditions occur with minimal loss in overall permeability. Nanosizing of the MOF enhances its dispersion within the polymer matrix to minimize non-selective microvoid formation around the particles. Amination of such MOFs increases their interaction with thepolymer matrix, resulting in a measured rigidification and enhanced selectivity of the overall composite. The optimal MOF MMM performance was verified in three different polymer systems, and also over pressure and temperature ranges suitable for carbon capture. Mixed matrix membranes can separate CO2 from flue gas mixtures but increasing selectivity without sacrificing permeability remains challenging. Selectivity can be increased with little loss in permeability by using nanoparticulate, amine-functionalized metal–organic framework fillers.

A multiscale approach to predict the mixed gas separation performance of glassy polymeric membranes for CO2 capture: the case of CO2/CH4 mixture in Matrimid®

The gas solubility in polymeric membranes affects the separation performance, particularly in the case of CO2 capture processes. Solubility and solubility-selectivity in membranes of multicomponent mixtures can deviate rather markedly from the corresponding pure gas values, due to swelling and competition phenomena, and require dedicated time-consuming measurements. Many experiments can be avoided by using a suitable thermodynamic tool, such as an Equation of State (EoS) model, to represent the gases sorption in the membrane. Such models require, for parameterization, knowledge of the polymer behavior above the glass transition Tg, which is a limit for membrane modeling, because the most attractive polymers for gas separation are rigid matrices characterized by very high Tg values, difficult to reach experimentally. In this work, we study the sorption of CO2/CH4 mixtures in a high-Tg polyimide membrane (Matrimid®) using a bottom-up approach. Pressure-volume-temperature data for Matrimid® above Tg are generated using NPT Molecular Dynamics simulations: the results are regressed to find Matrimid® parameters for the PC-SAFT Equation of State. Finally, the Non Equilibrium PC-SAFT macroscopic model (NE-PC-SAFT) is used to calculate CO2 and CH4 solubility and solubility-selectivity as a function of gas mixture pressure, composition and temperature. The approach is tested successfully over many experimental pure gas and vapor sorption data in Matrimid®. Mixed gas calculations predict a marked competition, which affects more methane than CO2 sorption, and results in a higher-than-ideal value of solubility-selectivity. Combined with the fact that experimental mixed gas permeability-selectivity is lower than the ideal value, such results indicate that the diffusivity of CH4 in Matrimid® is significantly enhanced in presence of CO2, causing a decrease of diffusivity-selectivity.

ATR-FTIR study of the interaction of CO2 with bacterial cellulose-based membranes

Bacterial cellulose (BC) was used as an active material for fabrication of the membrane for CO2 capture. The BC-membrane is further modified with silk fibroin protein and ZnO nanoparticles in order to increase the number of sites that may bind CO2. The interaction of the CO2 with the membranes was investigated by means of ATR-FTIR spectroscopy. The argon purged membranes were used as the control samples. After pressurizing the membranes in CO2 at 3bar, FTIR spectra were recorded and compared to the spectra of the controls. The interaction of the membrane materials with CO2 were studied by examining two regions of the spectra: 740–610cm−1 (bending vibrations of CO2) and 2400–2320cm−1 (asymmetric stretching vibrations of CO2). The envelope of the bending mode peak in 740–610cm−1 region is resolved into particular peaks and the appearance of the additional line at 654cm−1 suggested that the absorption bands of CO2 alters because of the Lewis acid-base type of interaction with membranes. The changes in the region of asymmetric stretching vibrations of CO2 were even more pronounced after pressurization. The presence of the number of different sites (active groups) for the CO2 adsorption reflected in the appearance of several additional asymmetric stretching peaks. Also, due to the entrapment of the CO2 in the membrane, a typical CO asymmetric stretching vibration line at ∼2340cm−1 is shifted towards lower frequencies. The analysis of the results suggested that there is a strong interaction of CO2 with BC membrane, which is additionally improved by its modification with silk fibroin and ZnO nanoparticles. From the results of CO2 permeation experiment, the basic BC membrane, silk fibroin-modified BC membrane and ZnO nanoparticles-modified BC membrane exhibited the CO2 permeability of 2.73, 2.69 and 2.66 Barrer, respectively.

CO2 capture from natural gas combined cycles by CO2 selective membranes

This paper performs a techno-economic analysis of natural gas-fired combined cycle (NGCC) power plants integrated with CO2 selective membranes for post-combustion CO2 capture. The configuration assessed is based on a two-membrane system: a CO2 capture membrane that separates the CO2 for final sequestration and a CO2 recycle membrane that selectively recycles CO2 to the gas turbine compressor inlet in order to increase the CO2 concentration in the gas turbine flue gas. Three different membrane technologies with different permeability and selectivity have been investigated. The mass and energy balances are calculated by integrating a power plant model, a membrane model and a CO2 purification unit model. An economic model is then used to estimate the cost of electricity and of CO2 avoided. A sensitivity analysis on the main process parameters and economic assumptions is also performed. It was found that a combination of a high permeability membrane with moderate selectivity as a recycle membrane and a very high selectivity membrane with high permeability used for the capture membrane resulted in the lowest CO2 avoided cost of 75US$/tCO2. This plant features a feed pressure of 1.5bar and a permeate pressure of 0.2bar for the capture membrane. This result suggests that membrane systems can be competitive for CO2 capture from NGCC power plants when compared with MEA absorption. However, to achieve significant advantages with respect to benchmark MEA capture, better membrane permeability and lower costs are needed with respect to the state of the art technology. In addition, due to the selective recycle, the gas turbine operates with a working fluid highly enriched with CO2. This requires redesigning gas turbine components, which may represent a major challenge for commercial deployment.