Carbon Dioxide Separation Research Articles

Porous Organic Cages CC3 and CC2 as Adsorbents for the Separation of Carbon Dioxide from Nitrogen and Hydrogen

Porous Organic Cages CC3 and CC2 as Adsorbents for the Separation of Carbon Dioxide from Nitrogen and Hydrogen

Valorization of spent disposable wooden chopstick as the CO2 adsorbent for a CO2/H2 mixed gas purification

A series of activated carbons (ACs) derived from spent disposable wooden chopsticks was prepared via steam activation and used to separate carbon dioxide (CO2) from a CO2/hydrogen (H2) mixed gas at atmospheric pressure. A factorial design was employed to investigate the effects of the activation temperature and time as well as their interactions on the production yield of ACs and their CO2 adsorption capacity. The activation temperature exhibited a much higher impact on both the production yield and the CO2 adsorption capacity of ACs than the activation time. The interaction of both parameters did not significantly affect the yield of ACs, but did affect the CO2 adsorption capacity. The optimal preparation condition provided ACs with a desirable yield of around 23.18% and a CO2 adsorption capacity of 85.19 mg/g at 25 °C and 1 atm and consumed the total energy of 225.28 MJ/kg AC or 116.4 MJ/g-mol CO2. A H2 purity of greater than 96.8 mol% was achieved from a mixed gas with low CO2 concentration (< 20 mol%) during the first 3 min of adsorption and likewise around 90 mol% from a mixed gas with a high CO2 concentration (> 30 mol%) during the first 2 min. The CO2 adsorption on the as-prepared ACs proceeded dominantly via multilayer physical adsorption and was affected by both the surface area and micropore volume of the ACs. The adsorption capacity was diminished by around 18% after six adsorption/desorption cycles. The regeneration of the as-prepared chopstick-derived ACs can be easily performed via heating at a low temperature and ambient pressure, suggesting their potential application in the temperature swing adsorption process.

An integrated materials approach to ultrapermeable and ultraselective CO 2 polymer membranes

Advances in membrane technologies that combine greatly improved carbon dioxide (CO 2 ) separation efficacy with low costs, facile fabrication, feasible upscaling, and mechanical robustness are needed to help mitigate global climate change. We introduce a hybrid-integrated membrane strategy wherein a high-permeability thin film is chemically functionalized with a patchy CO 2 -philic grafted chain surface layer. A high-solubility mechanism enriches the concentration of CO 2 in the surface layer hydrated by water vapor naturally present in target gas streams, followed by fast CO 2 transport through a highly permeable (but low-selectivity) polymer substrate. Analytical methods confirm the existence of an amine surface layer. Integrated multilayer membranes prepared in this way are not diffusion limited and retain much of their high CO 2 permeability, and their CO 2 selectivity is concurrently increased in some cases by more than ~150-fold.

Membrane for industrial exhaust gas treatment possesses high separation factor

Ceramics company NGK Insulators Ltd has developed a carbon dioxide (CO2) separation membrane for treating industrial exhaust gas. Tests have confirmed that it possesses a significantly higher separation factor than that of a conventional deca-dodecasil rhombohedral (DDR) zeolite membrane. Here, we briefly look at the technology that is set to be commercialised in 2030.

Tape-casting and freeze-drying gadolinia-doped ceria composite membranes for carbon dioxide permeation

Porous ceria: 20 mol% gadolinia (20GDC) ceramic membranes were prepared by tape casting (TC) and freeze-drying (FD) techniques, obtaining ceramic matrices with randomly dispersed round pores and with an aligned pore structure, respectively. Samples were sintered at 1450 °C, followed by infiltration of molten eutectic sodium-lithium carbonates (NLC). The pore morphology of 20GDC-TC and 20GDC-FD composite membranes was evaluated by analysis of scanning electron microscopy images. The electrical resistivity was determined by electrochemical impedance spectroscopy in the 1 Hz - 10 MHz frequency range from 300 °C to 700 °C, covering the solid-to-molten NLC temperature range, showing that the aligned pore structure improved the conductivity of the ceramic matrix in addition to facilitating molten carbonate infiltration, improving the total (bulk + interfaces) electrical conductivity of the composite membrane. Permeation experiments showed high CO 2 permeation rates reached 5.35 × 10 −7 mol m −2 s −1 Pa −1 at 800 °C. The infiltration of molten sodium-lithium carbonate in gadolinium-doped ceria prepared by the freeze-drying technique is proposed as an optimized procedure for producing membranes for carbon dioxide separation. - Ceramic-carbonate dual-phase membranes were successfully prepared by tape casting and freeze-drying techniques. - Ceramic matrices were produced with aligned porosity for optimizing carbon dioxide permeation. - Electrochemical impedance spectroscopy measurements indicated improved carbonate and oxygen ion conductivity in the membranes with porous matrices obtained by freeze drying. - CO 2 permeance for the membrane produced by freeze-drying reached 5.35 × 10 −7 mol m −2 s −1 Pa −1 at 800 °C

Research progress of biogas decarbonization

Taking biogas decarbonization process as the theme, this paper introduces several kinds of process methods for producing dry ice by separating carbon dioxide based on biogas, relevant research results at home and abroad, as well as the advantages and disadvantages of various process methods. Finally, the relevant application cases and the new direction of future development are introduced. This paper introduces the biogas decarbonization process and related equipment, which provides theoretical support for future research.

Thermodynamic Modeling of CO2 Separation Systems with Soluble, Redox-Active Capture Species

Electrochemical approaches hold promise for energy-efficient and modular carbon dioxide (CO2) separation systems that can make direct use of renewably generated electricity. Here, we employ a thermodynamic modeling approach to estimate the upper performance bounds of CO2 separation processes that use soluble, redox-active capture species. We contemplate the impact of tunable molecular and electrolyte properties on the thermodynamic and faradaic efficiencies of four characteristic system configurations. We find a trade-off between these efficiency metrics and propose a new metric, the combined efficiency, that can be used to further explore this trade-off and identify desirable property sets that balance energy and materials requirements. Subsequently, we determine effective CO2 binding affinities of redox-active capture molecules and demonstrate how these values are dependent upon molecular properties, system format, and operating conditions. Overall, this analytical framework can help guide molecular discovery and electrolyte engineering in this emerging field by providing insight into target material properties.

N- and S-Doped Carbons Derived from Polyacrylonitrile for Gases Separation

The CO2 capture using adsorption can reduce the carbon footprint, increasing the sustainability of the process without the production of wastes present in commonly used industrial operations. The present research work analyses the effect of the doping-agents incorporation in carbon materials upon adsorption and separation of gases, specifically for carbon dioxide and nitrogen. The carbons precursor was polyacrylonitrile (PAN), which enabled the incorporation of nitrogen atoms in the structure, whereas sulphur doping was reached using pure sulphur after the carbonisation step. The influence of several variables (such as temperature or pressure) and characteristics of synthesised materials (mainly corresponding to surface characteristics) on carbon dioxide separation has been evaluated. Adsorption isotherms were determined for each gas (CO2 and N2) at different temperatures and pressures. Different adsorption models were evaluated to fit the experimental data. In general, the Toth isotherm described better the adsorption for both gases. Important parameters such as CO2/N2 selectivity and heat of adsorption were determined using the IAS theory and the experimental isotherms at different temperatures, respectively. Non-activated carbons generated from PAN carbonisation without sulphur addition showed the highest values of selectivity (up to 400) and adsorption heat (up to 40 kJ mol−1), mainly at low pressures and at low carbon dioxide uptakes, respectively. Furthermore, thanks to their high adsorption capacity, these carbons can be applied for carbon dioxide separation from mixtures with nitrogen.

Sono-hollow fiber membrane contactors: A new approach for CO2 separation by physical/chemical absorbents

Herein, the nano adsorbents of Fe3O4 and Fe3O4@SiO2–NH2 were first synthesized and then dispersed in distilled water as a base fluid for Carbon dioxide (CO2) separation from a gas stream using a polypropylene hollow fiber membrane contactor (PP HFMC) and the separation experiment was performed under non-ultrasonic/ultrasonic irradiation for the first time. The impacts of varying liquid and gas flow rates, nanoparticles (NPs) loading, absorbents viscosity, NPs stability, and ultrasonic irradiation intensity were evaluated on the performance of Fe3O4 and Fe3O4@SiO2–NH2 nanofluids in CO2 separation. According to the obtained results, Fe3O4@SiO2–NH2 nanofluid was considerably powerful compared to Fe3O4 nanofluid due to the advantage of chemical reaction with CO2. Furthermore, ultrasound irradiation effectively raised the CO2 absorption capacity of Fe3O4 and Fe3O4@SiO2–NH2 nanofluids up to 13.37 and 16.41%, respectively. Ultimately, at the best operational condition, the CO2 separation enhancement factors of 58.44 and 84.45% were achieved by Fe3O4@SiO2–NH2 nanofluid under non-ultrasonic irradiation and ultrasonic irradiation conditions.

Control of zeolite framework flexibility for ultra-selective carbon dioxide separation

Molecular sieving membranes with uniform pore size are highly desired for carbon dioxide separation. All-silica zeolite membranes feature well-defined micropores, but the size-exclusion effect is significantly compromised by the non-selective macro-pores generated during detemplation. Here we propose a template modulated crystal transition (TMCT) approach to tune the flexibility of Decadodecasil 3 R (DD3R) zeolite to prepare ultra-selective membranes for CO2/CH4 separation. An instantaneous overheating is applied to synchronize the template decomposition with the structure relaxation. The organic template molecules are transitionally converted to tight carbon species by the one-minute overheating at 700 °C, which are facilely burnt out by a following moderate thermal treatment. The resulting membranes exhibit CO2/CH4 selectivity of 157~1,172 and CO2 permeance of (890~1,540) × 10−10 mol m−2 s−1 Pa−1. The CO2 flux and CO2/CH4 mixture selectivity reach 3.6 Nm3 m−2 h−1 and 43 even at feed pressure up to 31 bar. Such strategy could pave the way of all-silica zeolite membranes to practical applications.

The effect of protic ionic liquids incorporation on CO2 separation performance of Pebax-based membranes

• Two protic ionic liquids/Pebax blended membranes were developed for CO 2 separation. • [TMGH][Im]/Pebax blended membrane showed better CO 2 permeability and selectivity. • Gas permeability increased and CO 2 selectivity declined at higher temperatures. The separation of carbon dioxide (CO 2 ) is of great importance for environment protection and gas resource purification. The ionic liquids (ILs)-based gas separation membrane provides a new chance for efficient CO 2 separation, while high permeability and selectivity of membranes is a great challenge. In this study, the influence of two protic ILs with different anion ([TMGH][Im] and [TMGH][PhO]) on the CO 2 separation performance of the prepared ILs/Pebax blended membranes were systematically investigated at different temperature. The results showed the CO 2 permeability exhibits the rising trend for ILs/Pebax blended membranes with the increment of IL content. Especially, the [TMGH][Im] with low viscosity and high CO 2 absorption capacity leads to the blended membranes showing better CO 2 permeability and ideal CO 2 selectivity than that of membranes with [TMGH][PhO] at high IL content. Besides, with operating temperature increasing, the gas permeability of 20% (mass) [TMGH][Im]/Pebax blended membrane increases due to the decreasing viscosity of IL and the rising chain mobility of polymer. Inversely, the gas selectivity shows decreasing trend because CO 2 absorption capacity obviously decreased at higher temperature.

Chemical Looping Combustion: A Brief Overview

The current development of chemical looping combustion (CLC) technology is presented in this paper. This technique of energy conversion enables burning of hydrocarbon fuels with dramatically reduced CO2 emission into the atmosphere, since the inherent separation of carbon dioxide takes place directly in a combustion unit. In the beginning, the general idea of the CLC process is described, which takes advantage of solids (so-called oxygen carriers) being able to transport oxygen between combustion air and burning fuel. The main groups of oxygen carriers (OC) are characterized and compared, which are Fe-, Mn-, Cu-, Ni-, and Co-based materials. Moreover, different constructions of reactors tailored to perform the CLC process are described, including fluidized-bed reactors, swing reactors, and rotary reactors. The whole systems are based on the chemical looping concept, such as syngas CLC (SG-CLC), in situ Gasification CLC (iG-CLC), chemical looping with oxygen uncoupling (CLOU), and chemical looping reforming (CLR), are discussed as well. Finally, a comparison with other pro-CCS (carbon capture and storage) technologies is provided.

The State-of-the-Art Functionalized Nanomaterials for Carbon Dioxide Separation Membrane.

Nanocomposite membrane (NCM) is deemed as a practical and green separation solution which has found application in various fields, due to its potential to delivery excellent separation performance economically. NCM is enabled by nanofiller, which comes in a wide range of geometries and chemical features. Despite numerous advantages offered by nanofiller incorporation, fabrication of NCM often met processing issues arising from incompatibility between inorganic nanofiller and polymeric membrane. Contemporary, functionalization of nanofiller which modify the surface properties of inorganic material using chemical agents is a viable approach and vigorously pursued to refine NCM processing and improve the odds of obtaining a defect-free high-performance membrane. This review highlights the recent progress on nanofiller functionalization employed in the fabrication of gas-separative NCMs. Apart from the different approaches used to obtain functionalized nanofiller (FN) with good dispersion in solvent and polymer matrix, this review discusses the implication of functionalization in altering the structure and chemical properties of nanofiller which favor interaction with specific gas species. These changes eventually led to the enhancement in the gas separation efficiency of NCMs. The most frequently used chemical agents are identified for each type of gas. Finally, the future perspective of gas-separative NCMs are highlighted.

Carbon dioxide recovery from a simulated dry exhaust gas by an internally heated and cooled temperature swing adsorption packed with a typical hydrophobic adsorbent

• Internally heated / cooled temperature swing adsorption was tested for CO 2 capture. • Two typical hydrophobic adsorbents were employed for wet emission gas processing. • The separation performance of High Silica Zeolite was explored. • The unique separation behavior of Carbon Molecular Sieves was examined. This study focused on the carbon dioxide (CO 2 ) separation and recovery by an internally heated and cooled thermal swing adsorption process. As part of the preliminary investigation, the CO 2 capture and enrichment performance of carbon molecular sieve (CMS), a typical hydrophobic adsorbent, and high silica zeolite (HSZ), which indicates hydrophobic behavior among zeolites, were examined in a simulated dry exhaust gas. In addition, the hydroscopic adsorbent, CaA type zeolite, was employed for comparison. The effects of the regeneration temperature and the regeneration air flow rate on the separation performance were primarily investigated. In general, the CaA type of zeolite indicated a greater CO 2 concentration performance and recovery ratio due to its relatively larger adsorption capacity. Comparison between HSZ and CMS showed that the CO 2 separation and recovery performance of HSZ were greater than that of CMS. A CO 2 concentration four times higher than that of the feed gas was obtained at a regeneration temperature of 80 °C. Moreover, further enrichment of CO 2 at the desorption outlet was achieved by reducing the regeneration air flow rate to 1/40 of the feed gas of the adsorption process in exchange for lowering the CO 2 recovery ratio. In contrast, CMS could only produce three times greater the concentration of enriched CO 2 when compared to the feed gas. The enriched CO 2 concentration was almost independent of the regeneration air flow rate. This behavior was due to a lower CO 2 adsorption selectivity of CMS; this interpretation was supported by time profiles of desorption gas outlet volume and the CO 2 concentration.

Unveiling the critical role of biogas compositions on carbon dioxide separation in biogas upgrading using pressure swing adsorption

Unveiling the critical role of biogas compositions on carbon dioxide separation in biogas upgrading using pressure swing adsorption

CO2 capture and separation from H2/CH4/N2 gas mixtures by a novel ternary pentagonal monolayer “Penta-BCN”: First principles investigation

In the present study, applications of novel 2D ternary pentagonal monolayer “penta-BCN” are investigated for selective capturing of CO2, using density functional theory approach. The adsorption energy (Ead) result shows that pristine penta-BCN monolayer chemisorbed CO2 molecule with Ead value of −20.71 kcal/mol. Moreover, the kinetics study indicates that the conversion of physisorption to chemisorption need a smaller energy barrier (0.12 eV). The penta-BCN monolayer can uptake up to six CO2 molecules, which is higher storage capacity compared to previous studies. The obtained results evince that penta-BCN can selectively capture CO2 from CO2/N2, CO2/H2 and CO2/CH4 gas mixture. The electronic properties of penta-BCN tuned with the adsorption of CO2 molecules, indicates the sensitivity of the monolayer towards the CO2. The recovery time analysis shows that the regeneration of the substrate after carbon dioxide gas adsorption is feasible at 350 K. The results of the present study demonstrate that the penta-BCN can be used as an emerging 2D material for an efficient carbon dioxide capture and separation.

A facile one-pot preparation of porphyrin-based microporous organic polymers for adsorption of carbon dioxide, ethane, and methane

Achieving a cost-effective preparation of 3D porphyrin-based microporous organic polymers (PMOPs) for the adsorption and separation of carbon dioxide (CO2), ethane (C2H6), and methane (CH4) remains difficult.

Electrospun, non-woven fiber membranes of porous polyimides with high carbon dioxide uptakes and selectivities

Microporous organic polyimides are well suited for carbon dioxide separation from gas mixtures based on their polar surface and their tendency towards ultramicroporosity. Nevertheless, their application potential is limited due to an inherent insolubility and infusibility, preventing an easy processing into functional objects like membranes. By establishing a three-step synthesis procedure for the literature known network NPI-I, here, a solution to this challenge is demonstrated. The central step is electrospinning of a solution of the linkers tetrakis(4-aminophenyl)methane and naphthalene 1,4,5,8-tetracarboxylic dianhydride and the auxiliary polymer polyvinylpyrrolidone into a precursor fiber mat. The mat was then heated to polymerize the linkers into the polyimide. Subsequently, PVP was removed by pyrolysis obtaining a robust, flexible and self-standing membrane. The NPI-I fiber mat exhibits a remarkable microporosity with a BET surface area of 222 m 2 /g, a total pore volume of 0.121 cm 3 /g and a high amount of ultramicropores. Its CO 2 uptake of 3.0 mmol/g (0 °C, 1 bar) and its CO 2 /CH 4 selectivity of about 20 (0 °C, 1 bar) even exceed the literature values for bulk NPI-I. This study reveals that PVP acts as a template on molecular level influencing, primarily the micropore formation, reducing the BET surface area by roughly a factor of three compared to the bulk material. In contrast, the ultramicroporosity of the porous polyimides remains mainly unaffected. We envision that this three-step synthesis can be transferred to a broad variety of porous polymers. With electrospinning the large-scale production of self-standing membranes becomes realistic rendering the application of porous polymers for gas separation more likely. • Shaping of ultramicroporous polyimides into non-woven, robust and flexible fiber membranes with a hierarchical porosity • Development of a three-step synthesis procedure based on electrospinning with thermally labile auxiliary polymer • Auxiliary polymer acts as template which influences the micro- and mesoporosity of the fibrous membranes • Synthesis procedure retains the ultramicroporous character of the polyimides

Spontaneous self-healing ionogels for efficient and reliable carbon dioxide separation

Spontaneous self-healing ionogels with imine bond cross-linked supramolecular polymer networks were fabricated for efficient and reliable CO2 separation.

H-passivated nanoporous graphene membranes for CO2/N2 separation: A reactive molecular dynamic simulation

We used a reactive force-field (ReaxFF) to investigate the capability of H-passivated nanoporous graphene as a membrane for the separation of carbon dioxide from nitrogen. Unlike traditional atomistic force-fields, the reactive force field considers chemical bond-forming/braking and estimates the polarisation effect more accurately. We examined the effect of pore size and pore shape in several gas mixtures with different mole ratios. We assessed the selectivity of six H-passivated pores by counting the number of transmitted molecules from them. The simulation shows that the H-modified porous graphene membrane with pore diameter (short side) of about 2.4 Å only allow N2 molecules to permeate through and have the best separation selectivity. The CO2 molecules can pass through pores greater than 4.2 Å diameters. However, they tend to accumulate near the graphene membranes due to non-bonded interactions and do not diffuse in the vacuum until they saturate the graphene walls.