Membranes For CO2 Capture Research Articles

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.

SO2 interference on separation performance of amine-containing facilitated transport membranes for CO2 capture from flue gas

Post-combustion carbon capture using membranes is a key approach to control CO2 emissions from power plants using fossil fuels. The minor contaminants, such as SO2 and O2, may influence the long-term membrane performance. With the presence of SO2 in the feed gas, SO2 could preferably react with amine carriers and hinder the permeation of CO2 in the amine-containing facilitated transport membranes. Possible amine degradation and competitive reactions would reduce membrane performance with real flue gas. With SO2 concentrations of 0.7–5ppm, two amine-containing facilitated transport membranes were tested at 57 and 102°C, respectively. Unstable membrane performance was observed at 102°C for the membrane containing Lupamin® as fixed-site carrier and potassium glycinate (K-Gly) as mobile carrier in the presence of SO2. On the contrary, two membranes containing polyvinylamine (PVAm) as fixed-site carrier and amino acid salts as mobile carriers showed stable separation performance in the presence of 1–3ppm SO2 at 57°C. Therefore, the operating temperature plays a significant role in the membrane stabilities in the presence of SO2. In addition, the infrared (IR) spectra of the membrane components exposed to SO2 with respect to exposure time were collected. It was found that the amines reacted with SO2 to form sulfite products irreversibly at 102°C. The spectral results were consistent with the observed membrane separation performance. The stable membrane performances of the facilitated transport membranes at 57°C with SO2 at ppm levels indicate the applicability of the developed amine-containing membranes for use in CO2 capture from real flue gas.

Hybrid membranes of nanostructrual copolymer and ionic liquid for carbon dioxide capture

Efficient CO2 capture membranes were prepared using a hybrid comprising the poly(styrene-block-butadiene-block-styrene)-graft-poly(oxyethylene methacrylate) (SBS-g-POEM) nanostructural copolymer and the ionic liquid (IL) 1-ethyl-3-methylimidazolium dicyanamide (EMIMDCA). The SBS-g-POEM copolymer was synthesized via a mass-producible, cheap, free-radical polymerization process. The specific interaction of SBS-g-POEM with EMIMDCA and the good miscibility of these species were confirmed by Fourier transform infrared spectroscopy (FT–IR) and wide angle X-ray scattering (WAXS) and by using a universal testing machine (UTM). The microphase-separated nanostructure of the membranes and uniform distribution of EMIMDCA were also observed using transmission electron microscopy (TEM) and small angle X-ray scattering (SAXS). The neat SBS membrane exhibited a CO2 permeability of 372 Barrer (1 Barrer=10−10cm3(STP)·cm/(cm2·s·cmHg) and CO2/N2 selectivity of 16.4; these values increased to 407 Barrer and 21.6, respectively, for the SBS-g-POEM membrane due to the high CO2 affinity of the polar POEM side chains. Upon incorporation of EMIMDCA, the CO2 permeability increased to 514 Barrer without a large sacrifice of the selectivity. In contrast, the blend of neat SBS and EMIMDCA did not show any gas separation ability due to the inhomogeneity and poor mechanical properties, indicating the importance of grafting POEM to the SBS main chains.

A self-forming dual-phase membrane for high-temperature electrochemical CO2 capture

We report here a dual-phase mixed CO32−- and e−-conducting CO2 capture membrane self-formed at high temperatures from NiO and molten carbonate.

Room-temperature, one-pot process for CO2 capture membranes based on PEMA-g-PPG graft copolymer

Gas separation based on membrane technology can possibly be used to offset the greenhouse effect because of its high energy efficiency and low cost. To achieve commercialization, it is essential that the gas-separation membrane demonstrates high performance and scalability. Here, we first report the room-temperature, one-pot process for CO2 capture membranes based on the synthesis of a graft copolymer comprising of poly(ethylene-alt-maleic anhydride) (PEMA) main chains and poly(propylene glycol) (PPG) side chains. As confirmed by Fourier transform infrared (FT-IR) and nuclear magnetic resonance (1H NMR) spectroscopy, the PEMA-g-PPG synthesis was based on the complete reaction (100% conversion) of O-(2-aminopropyl)-O′-(2-methoxyethyl) polypropylene glycol (AMPPG) with PEMA in butanol (BuOH) at room temperature. X-ray diffraction (XRD) and differential scanning calorimetry (DSC) revealed that the PEMA-g-PPG graft copolymer exists in an amorphous rubbery state with a bimodal microstructure. Without any post-treatment, the as-synthesized PEMA-g-PPG in BuOH was directly coated onto a microporous polysulfone support to form thin-film composite membranes. The membrane exhibited high selectivity (i.e. 82.6 for CO2/N2 and 26.8 for CO2/CH4) and good CO2 permeability (99.1Barrer), outperforming conventional PEBAX block copolymer membranes. CO2 uptake measurements confirmed enhanced CO2 permeation resulting from the improved solubility of CO2 in PEMA-g-PPG compared with those of neat PEMA and PEBAX. The PEMA-g-PPG membrane could be commercially feasible owing to its simple coating process, low cost, high selectivity, and scalability.

Nanocellulose-based membranes for CO2 capture

A new type of hydrophilic polymeric membrane based on microfibrillated cellulose (MFC) has been investigated to determine its potential in the field of gas separation, with special reference to carbon capture and natural gas sweetening. In particular, pure MFC films and MFC/Lupamin® (a commercial polyvinylamine produced by BASF) nanocomposite membrane have been synthesized and characterized. The effect of relative humidity on gas permeability was considered and independent water vapor sorption experiments were also carried out in order to correlate the permeation results to the actual water content in the materials. The experimental results showed that very good CO2/N2 and CO2/CH4 selectivity (in the order of 500 and 350 respectively) could be reached by using pure MFC films, which however showed limited CO2 permeability, never exceeding 25Barrer, even at the highest relative humidity investigated. To increase the transmembrane flux, a hydrophilic polyvinylamine (Lupamin®) has been added to the pure MFC: the addition caused a marked increase in permeability of up to one order of magnitude but decreased the selectivity to about the same extent, thus decreasing the overall membrane performance. The reason of such behavior seems to be related to the amount of water absorbed by the membrane as the MFC/Lupamin nanocomposite resulted to be highly swollen by water vapor.Nonetheless, both the investigated materials showed separation performances that are above the 2008 Robeson's upper bound for CO2/N2 and CO2/CH4 systems, disclosing an attractive potential for the production of advanced gas separation membranes.

Preparation of facilitated transport hollow fiber membrane for gas separation using cobalt tetraphenylporphyrin complex as a coating material

In this work, a study regarding removal of O2 from post-combustion flue gas using polymer membrane for CO2 capture has been performed. A facilitated transport hollow fiber membrane was prepared and the morphology was examined by scanning electron microscope to understand the correlation of the morphology with the permeation of the membrane. Chemical characterizations of the membranes were conducted by Attenuated total reflectance Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy analysis. The effects of the parameters involved in the spinning procedure of polyethersulfone hollow fiber, poly(n-butyl methacrylate) layer deposition, and cobalt tetraphenylporphyrin complex selective composite membranes were investigated. As a result, the maximum ideal gas selectivities for O2/N2 and O2/CO2 were achieved at 3.2 and 1.17, respectively, at a pressure of 0.098 bar, with a considerably high O2 permeance of 17 GPU for a M4 membrane. This membrane showed facilitated oxygen transport with nitrogen and carbon dioxide at low pressure. The convinced changes in the polymer morphology and separation performance data were evaluated to single gas permeation. Obtained results are useful to develop this membrane further for oxygen removal from flue gas in the area of CO2 capture and storage as a pretreatment process for prevention of the degradation of CO2 absorbents.

Amphiphilic Graft Copolymer Nanospheres: From Colloidal Self-Assembly to CO2 Capture Membranes.

Colloidal nanosphere self-assembly effectively generates ordered nanostructures, prompting tremendous interest in many applications such as photonic crystals and templates for inverse opal fabrication. Here we report the self-assembly of low-cost, graft copolymer nanospheres for CO2 capture membranes. Specifically, poly(dimethylsiloxane)-graft-poly(4-vinylpyridine) (PDMS-g-P4VP) is synthesized via one-pot, free radical dispersion polymerization to give discrete monodisperse nanospheres. These nanospheres comprise a surface-anchored highly permeable PDMS layer and internal CO2-philic P4VP spherical core. Their diameter is controllable below the submicrometer range by varying grafting ratios. The colloidal dispersion forms a long-range, close-packed hexagonal array on a substrate by inclined deposition and convective assembly. The array shows dispersion medium-dependent packing characteristics. A thermodynamic correlation is determined using different solvents to obtain stable PDMS-g-P4VP dispersions and interpreted in terms of Flory-Huggins interaction parameter. As a proof-of-concept, the implementation of these nanospheres into membranes simultaneously enhances the CO2 permeability and CO2/N2 selectivity of PDMS-based transport matrixes. Upon physical aging of the solution, the CO2/N2 selectivity is improved up to 26, one of the highest values for highly permeable PDMS-based polymeric membranes.

Post-Combustion CO<sub>2</sub> Capture from Exhaust Gas by Amines and Membranes

There is a necessity to reduce GHG emission because climate change may have critical consequences in many places around the world. The main gas which causes climate change is CO2 which is released into atmosphere mainly by industries and vehicles. This research aims to compare two technologies for CO2 capture: chemical absorption with membranes, and to present hybrid processes using both of these. A review of the state of art for CO2 capture is used in this research. The capture by absorption with amines is the state of the art for post-combustion because it produces CO2 with higher purity and is cheaper. However, the energy and installation cost are high which does do not encourage its applicability. Membrane for CO2 capture from natural gas is promissory because of this. Thus, researchers have studied other technologies for CO2 capture to replace or add through including hybrid processes. Capture by membrane is a promising technology for this, provided that since it presents appropriate selectivity and permeability. This paper presents a comparison between CO2 capture by absorption with amines and by membranes. The goal is to discuss hybrid processes with these two technologies in series.

Few-layered ultrathin covalent organic framework membranes for gas separation: a computational study

This work found that energetic microenvironment controls the separation performance of few-layered 2D-COF membranes for CO2capture.

Preparation, characterization and laboratory-scale application of modified hydrophobic aluminum oxide hollow fiber membrane for CO2 capture using H2O as low-cost absorbent

The objective of this work was to apply the modified hydrophobic metal oxide hollow fiber membrane in a laboratory-scale gas–liquid membrane contacting process for CO2 capture applications using H2O as low-cost absorbent at room temperature. With this aim, the porous aluminum oxide (α-Al2O3) hollow fiber membranes were prepared by a phase inversion spinning technique and a sintering method. In order to render the hydrophilic surface of prepared Al2O3 hollow fiber membrane without changing its physical properties, a fluoroalkylsilanes (FAS) film was used. The fluoroalkylsilanized Al2O3 hollow fiber membrane surface was studied by performing thermal gravimetric analysis (TG), scanning electron microscopy (SEM), X-ray diffractometer (XRD). In addition, the hydrophobicity nature of modified Al2O3 hollow fiber membrane surfaces was measured by water drop contact angle test and break through pressure measurement. This work, for what we believe to be the first time, has successfully realized a room-temperature laboratory-scale gas–liquid membrane contactors using a single fluoroalkylsilanized Al2O3 hollow fiber membrane for CO2 capture. According to the experimental results, the correlations between water and gas flow rate, and CO2 mass transfer through the modified hydrophobic Al2O3 hollow fiber membranes are given. In addition, a comparative review was made between our modified hydrophobic aluminum oxide and traditional polymeric hollow fiber membrane for application in the field of CO2 absorption in water. The results indicated that studied fluoroalkylsilanized Al2O3 hollow fiber membrane may be possible candidates for the development of new gas–liquid membrane contactors for CO2 capture.

Anionic surfactant-doped Pebax membrane with optimal free volume characteristics for efficient CO2 separation

Calcium lignosulfonate (CaLS) is an organic anionic surfactant, which has been used for the first time as a charged additive to improve the performance of Pebax membranes for CO2 separation. Owing to the abundant hydrophobic groups and low charge density of lignosulfonate ion (LS2−), CaLS was found to efficiently interrupt the chain packing of Pebax 1657 matrix via both metal-organic complexation and hydrophobic interaction, endowing membranes with tunable fractional free volume (FFV). For dry membranes, CaLS could slightly enlarge membrane FFV without forming highly crosslinked structures. For humidified membranes, water-induced swelling led to a remarkable enhancement of FFV, while the hydrophobic interaction between CaLS and Pebax avoided excessive swelling. With the coexistence of CaLS and water, optimal FFV and moderate salting-out effect were acquired, resulting in very high CO2 permeability (3585Barrer) and fairly good CO2/gas selectivity (29 for CO2/CH4 and 71 for CO2/N2). The separation mechanism was discussed by analyzing the relationship between salting-out effect and the well-known solution-diffusion mechanism. Based on the performance comparison of Pebax–CaLS membrane with the previously reported Pebax–salt membranes, the guideline about the design of polymer electrolyte membranes for CO2 capture was tentatively proposed.

Janus composite nanoparticle-incorporated mixed matrix membranes for CO2 separation

Silver-containing Janus nanoparticles were synthesized by adhering silver onto polydopamine nanosphere and then were embedded in Pebax® MH 1657 polymer matrix to fabricate mixed matrix membranes for CO2 capture. The Janus nanoparticle was composed of a polydopamine nanosphere (~80nm) with plenty of catechol-chelated Ag+ ions and a catechol-reduced metallic Ag nanoparticle (~20nm) epitaxially growing from the surface of the polydopamine nanosphere. The highly loaded Ag+ ions (58.41wt% of total Ag content) served as CO2 facilitated transport carriers and thereby endowed the membrane with CO2 facilitated transport ability, and meanwhile the inorganic metallic Ag nanoparticle can interfere the polymer chain packing and optimize the membrane free volume characteristics therefore affecting the diffusion behavior of gas molecules. The membrane separation performance for pure gas (CO2, CH4, and N2) and binary gas mixtures (CO2/CH4 and CO2/N2) of the Janus nanoparticle-incorporated Pebax membrane was investigated and compared with that of the polydopamine nanosphere-incorporated membrane without silver modification. An anti-tradeoff effect was achieved by incorporation of the silver-containing Janus nanoparticles. The best separation performance of the Janus-incorporated Pebax membrane for pure gas was obtained with a CO2 permeability of 150Barrer and a CO2/gas selectivity of 26.3 for CO2/CH4 and 72.5 for CO2/N2, i.e., 83%, 42% and 39% higher than those of neat Pebax membrane, respectively. The results suggested that incorporation of the Janus nanoparticles could achieve both a diffusion tuning effect and a facilitated transport effect simultaneously.

Effects of coexistent gaseous components and fine particles in the flue gas on CO2 separation by flat-sheet polysulfone membranes

Nowadays, membrane separation technology has been one of the most effective technologies for CO2 capture. The coexistent components in the actual flue gas, such as water vapor, SO2, O2 and fine particles, may have a significant influence on the separation performance of polymeric membranes for CO2 capture. In order to comprehensively and systematically investigate the effects of these components, a series of lab-scale separation experiments for CO2 capture were conducted in the simulation test-bed with the commercially available flat-sheet polysulfone (PSF) membranes. At first, the operation conditions were optimized for CO2 separation by PSF membranes and the best operation conditions were 0.4MPa as the feed gas pressure, 400L/h as the residual gas flow rate and 50°C as the feed gas temperature. Then, the PSF membrane performances on CO2 separation in the presence of water vapor, SO2, O2 and fine particles in the actual flue gas were studied. It was found that water vapor promotes the CO2 separation performance of PSF membranes by a net increase of the CO2/N2 selectivity, CO2 permeability and CO2 enrichment efficiency. O2 slightly inhibits the CO2 separation performance, while the effect of SO2 is negligible. The gypsum fine particles significantly deteriorate CO2 separation performance of PSF membranes, which mainly results from the occupation of the effective membrane area, the increase of the mass transfer resistance and the partial adsorption of the gases by the gypsum fine particles deposited on the membranes.

Techno-economic assessment of two novel feeding systems for a dry-feed gasifier in an IGCC plant with Pd-membranes for CO2 capture

This study focuses on the application of Pd-based membranes for CO2 capture in coal fuelled power plants. In particular, membranes are applied to Integrated Gasification Combined Cycle with two innovative feeding systems. In the first feeding system investigated, CO2 is used both as fuel carrier and back-flushing gas for the candle filters, while in the second case N2 is the fuel carrier, and CO2 the back-flushing gas. The latter is investigated because current dry feed technology vents about half of the fuel carrier, which is detrimental for the CO2 avoidance in the CO2 case. The hydrogen separation is performed in membrane modules arranged in series; consistently with the IGCC plant layout, most of the hydrogen is separated at the pressure required to fuel the gas turbine. Furthermore, about 10% of the overall hydrogen permeated is separated at ambient pressure and used to post-fire the heat recovery steam generator. This layout significantly reduces membrane surface area while keeping low efficiency penalties.The resulting net electric efficiency is higher for both feeding systems, about 39%, compared to 36% of the reference Selexol-based capture plant. The CO2 avoidance depends on the type of feeding system adopted, and its amount of vented gas; it ranges from 60% to 98%. From the economic point of view, membrane costs are significant and shares about 20% of the overall plant cost. This leads in the more optimistic case to a CO2 avoidance cost of 35 €/tCO2, which is slightly lower than the reference case.

High-performance composite membrane with enriched CO2-philic groups and improved adhesion at the interface.

A novel strategy to design a high-performance composite membrane for CO2 capture via coating a thin layer of water-swellable polymers (WSPs) onto a porous support with enriched CO2-philic groups is demonstrated in this study. First, by employing a versatile platform technique combining non-solvent-induced phase separation and surface segregation, porous support membranes with abundant CO2-philic ethylene oxide (EO) groups at the surface are successfully prepared. Second, a thin selective layer composed of Pebax MH 1657 is deposited onto the support membranes via dip coating. Because of the water-swellable characteristic of Pebax and the enriched EO groups at the interface, the composite membranes exhibit high CO2 permeance above 1000 GPU with CO2/N2 selectivity above 40 at a humidified state (25 °C and 3 bar). By tuning the content of the PEO segment at the interface, the composite membranes can show either high CO2 permeance up to 2420 GPU with moderate selectivity of 46.0 or high selectivity up to 109.6 with fairly good CO2 permeance of 1275 GPU. Moreover, enrichment of the PEO segment at the interface significantly improves interfacial adhesion, as revealed by the T-peel test and positron annihilation spectroscopy measurement. In this way, the feasibility of designing WSP-based composite membranes by enriching CO2-philic groups at the interface is validated. We hope our findings may pave a generic way to fabricate high-performance composite membranes for CO2 capture using cost-effective materials and facile methods.

A highly permeable and selective amino-functionalized MOF CAU-1 membrane for CO2–N2 separation

A thin tubular CAU-1 membrane of 2-3 μm exhibiting a high CO2 permeance of up to 1.34 × 10(-6) mol m(-2) s(-1) Pa(-1) and a CO2-N2 selectivity of 17.4-22.8 for CO2-N2 mixtures was achieved, demonstrating for the first time that amino-functionalized MOF membranes can provide high CO2-N2 selectivity and possess the potential for CO2 capture from flue gas.

Imidazole-Based Solvents and Membranes for CO2 Capture Applications

ABSTRACTImidazoles present a tunable, versatile and economical platform for the development of novel liquid solvents and polymer membranes for CO2 capture. An overview of our studies in this area is presented, with emphasis on characterization of structure-property relationships in imidazole-based materials through both experimental and computational studies. To this end, a growing library of systematically varied imidazole compounds has been synthesized using only commercial available starting materials and straightforward reactions. Using this library of compounds, we have sought to understand and develop predictive models for thermophysical properties relating to process design, including: density, viscosity, vapor pressure, pKa and CO2 absorption capacity. Furthermore, we have discovered that imidazoles are stable in the presence of SO2 and can form reversible 1:1 adducts, which can be beneficial as SO2 is typically present at ppm levels alongside CO2 in flue gas from coal-fired power plants.

Performance Requirements for CO2 Capture Technologies; How Realistic are Capture Cost Targets?

This paper discusses a methodology used to set, already at an early stage of technology development, the key performance requirements for carbon dioxide capture technologies necessary to meet a certain capture cost target. The methodology also illustrates how realistic or unrealistic cost targets can be. Although, applicable for capture technologies in general (pre-, post combustion and oxy fuel), the usefulness of the methodology is illustrated for one pre-combustion capture technology in particular i.e., Pd membranes for CO2 capture in a NGCC power plant.