CH4 Separation Research Articles

Enhancing the natural gas upgrading and acetylene extraction performance of stable zirconium-organic frameworks PCN-605 by ligand functionalization

Exploring stable adsorbents for efficient separation of C2H2 and CO2 from CH4 is of great significance to meet the requirements of natural gas upgrading and high-purity C2H2 production. Despite excellent structure stability and large surface area/pore volume, low adsorbate affinity and co-adsorption of mixtures in zirconium-organic frameworks (Zr-MOFs) seriously limit their applications in gas separation. To overcome these limitations, we designed a series of stable adsorbents based on Zr-based PCN-605 by replacing two H atoms from two central ligand-aromatic rings with different functional groups (–F, –OH, –NH2, –SO3H, and –SO3Ag), which are expected to gain steric hindrance effect and charge-tuning effect in varying degrees. The adsorption and separation performances of C2H2/CH4 and CO2/CH4 in PCN-605 materials were theoretically investigated by combining grand canonical Monte Carlo and density functional theory. Thereinto, PCN-605-SO3Ag shows the largest selectivity of C2H2/CH4 (1031.5) and CO2/CH4 (271.1) under molar ratio 1:99 at 298 K, or increased by 43.3 and 11.9 times, as against the parent PCN-605. This improvement is attributed to a good synergism of steric hindrance effect with charge-tuning effect exerted by –SO3Ag, which modifies not only the pore surface structure but also the charge distribution, favoring special three-way adsorption to recognize C2H2, strengthening CO2 affinity with –SO3Ag, but suppressing CH4 uptake, etc. This work highlights the effect of precise surface-structure and charge-distribution control by ligand functionalization on C2H2/CH4 and CO2/CH4 separation in PCN-605 materials, and provides a feasible strategy to design function-oriented Zr-MOF adsorbents for applications of natural gas upgrading and C2H2 extraction.

A Zeolitic Octahedral Metal Oxide with Ultra-Microporosity for Inverse CO2 /C2 H2 Separation at High Temperature and Humidity.

Separation of CO2 /C2 H2 to obtain pure C2 H2 presents a challenge for the chemical industry. CO2 -selective adsorbents are favored because of the convenient separation process. However, there are only a few CO2 -selective adsorbents that can effectively isolate CO2 from CO2 /C2 H2 , and there is almost no research on CO2 /C2 H2 separation under harsh conditions, such as with high temperatures and humidities. Herein, a zeolitic octahedral metal oxide based on ϵ-Keggin polyoxometalates is utilized for separations of CO2 /C2 H2 at high temperatures and humidities. Single gas adsorption measurements show that the material only adsorbs CO2 with almost no C2 H2 taken up. Dynamic competitive adsorption experiments show that the material efficiently separates CO2 /C2 H2 , and highly pure C2 H2 is obtained directly. The robust material maintains a high separation performance at 333 K with 18.12 % water. The high stability of the material enables reuse without loss of separation performance.

An Ultramicroporous Hydrogen-Bonded Organic Framework Exhibiting High C2 H2 /CO2 Separation.

The separation of C2 H2 /CO2 is not only industrially important for acetylene purification but also great scientific challenge due to their very similar molecular size and physical properties. To address this difficulty, herein, we present an ultramicroporous hydrogen-bonded organic framework (HOF-FJU-1) from tetracyano bicarbazole to separate C2 H2 from CO2 by taking advantage of differences in their electrostatic potential distribution. This material possesses a suitable pore environment and electrostatic potential distribution fitting well to C2 H2 , thus showing extra strong affinity to C2 H2 (46.73 kJ mol-1 ) and the highest IAST selectivity of 6675 for C2 H2 /CO2 separation among the adsorbents reported. The single crystal X-ray diffraction reveals that the suitable pore environment in HOF-FJU-1 provides multiple C-H⋅⋅⋅π and hydrogen-bonded interactions N⋅⋅⋅H-C with C2 H2 molecules. Dynamic breakthrough experiments demonstrate its outstanding separation performance to C2 H2 /CO2 mixtures.

Regulating C2H2/CO2 adsorption selectivity by electronic-state manipulation of iron in metal-organic frameworks

The separation of C2H2 from C2H2/CO2 mixture is of great importance, yet highly challenging in the petrochemical industry due to their similar physicochemical properties. While open-metal sites (OMSs) in metal-organic frameworks (MOFs) are known to possess high affinity toward C2H2, its selective adsorption performance regulated by the electronic state of the same OMSs remains unexplored. Here, we report a metal electronic-state manipulation approach to construct a pair of isostructural Fe-MOFs, namely LIFM-26(Fe[II]/Fe[III]) and LIFM-27(Fe[III]) with different Fe[II] or Fe[III] oxidation states on the Fe centers, which display mixed-valent Fe[II]/Fe[III] centers in the former and sole Fe[III] centers in the latter. Remarkably, LIFM-26(Fe[II]/Fe[III]) shows significantly enhanced C2H2 uptake capacity than LIFM-27(Fe[III]), attested by adsorption isotherms and IAST calculations, as well as simulated and experimental breakthrough experiments. Furthermore, in situ infrared (IR) and molecular calculations unveil that the presence of Fe[II] in LIFM-26(Fe[II]/Fe[III]) results in stronger Fe[II]–C2H2 interactions than Fe[III]–C2H2, which plays a key role in the C2H2/CO2 separation.

Two-Dimensional Metal-Organic Framework with Ultrahigh Water Stability for Separation of Acetylene from Carbon Dioxide and Ethylene.

Highly selective separation and purification of acetylene (C2H2) from ethylene (C2H4) and carbon dioxide (CO2) are daunting challenges in light of their similar molecule sizes and physical properties. Herein, we report a two-dimensional (2D) stable metal-organic framework (MOF), NUM-11 ([Cu(Hmpba)2]·1.5DMF) (H2mpba = 4-(3,5-dimethyl-1H-pyrazol-4-yl)benzoic acid), with sql topology, stacked together through π-π interactions for efficient separation of C2H2 from C2H4 and CO2. The 2D-MOF material offers high hydrolytic stability and good purification capacity; especially, it could survive in water for 7 months, even longer. This stable MOF selectively captures C2H2 from mixtures containing C2H4 and CO2, as determined by adsorption isotherms. The ideal adsorbed solution theory selectivity calculations and transient breakthrough experiments were performed to verify the separation capacity. The low isosteric heat of NUM-11a (desolvated NUM-11) (18.24 kJ mol-1 for C2H2) validates the feasibility of adsorbent regeneration with low energy footprint consumption. Furthermore, Grand Canonical Monte Carlo simulations confirmed that the pore surface of the NUM-11 framework enabled preferential binding of C2H2 over C2H4 and CO2 via multiple C-H···O, C-H···π, and C-H···C interactions. This work provides some insights to prepare stable MOF materials toward the purification of C2H2, and the water-stable structure, low isosteric heat, and good cycling stability of NUM-11 make it very promising for practical industrial application.

A TIFSIX pillared MOF with unprecedented zsd topology for efficient separation of acetylene from quaternary mixtures

The separation of acetylene (C2H2) from carbon dioxide (CO2) and other C1-C2 light hydrocarbons is important to produce C2H2 in high purity as well as recover other gases. However, it is challenged by the trade-off between the adsorption capacity and selectivity due to the similar physical properties. In this work, we reported a new TiF62− anion (TIFSIX) pillared porous metal organic framework ZNU-4 (ZNU = Zhejiang Normal University) with unprecedented zsd topology for selective C2H2 capture. The utilization of 1,4-di(1H-imidazol-1-yl)benzene (DIB) as the organic linker in ZNU-4 generates a highly twisted framework, resulting in a distinctive topological net with unique narrow 1D channels suitable for C2H2 trap. ZNU-4 features robust-flexible isotherms for C2H2 adsorption and the capacity under 1 bar and 298 K is as high as 85 cm3/g, 1.9, 2.1 and 7.1 folds of CO2, C2H4 and CH4 uptake. The IAST selectivity of C2H2 over CO2, C2H4, CH4 is 9, 12, and 300, respectively, higher than those of most popular porous materials. Modelling study indicated that C2H2 is trapped by cooperative Ti-F···HC≡CH···N(DIB) hydrogen bonding along with other weak Van der Waals interactions. Such cooperative bonding interactions have never been disclosed in other fluorinated anions pillared MOFs due to the absence of second binding site from organic linkers. The breakthrough experiments further confirmed the highly selective C2H2 separation performance from binary C2H2/CO2 mixtures, ternary C2H2/CO2/CH4 mixtures and quaternary C2H2/CO2/CH4/C2H4 mixtures. The separation factor of ZNU-4 for equimolar C2H2/CO2 mixture is 5.4, superior to those of many other benchmark materials.

Improving CH4 uptake and CH4/N2 separation in pillar‐layered metal–organic frameworks using a regulating strategy of interlayer channels

AbstractA pore engineering strategy involving the regulation of pillars in a series of pillar‐layered metal–organic frameworks was presented to promote pore size adjustment and pore environment optimization for efficient separation of CH4 from coal‐mine methane. Compared with the original Ni(BTC)(BPY) and Ni(BTC)(TED), the suitable pore size and rich supply of carboxylate oxygens in the newly constructed Ni(BTC)(PIZ) resulted in the strongest recognition of CH4, leading to both high CH4 uptake (1.62 mmol/g) and CH4/N2 (50/50) selectivity (7.32) at 298 K and 1 bar. Its optimal balance performance between uptake and selectivity was better than most reported adsorbents, which further led to the most efficient separation of CH4 from CH4/N2 mixtures. The stability of the structure and performance was verified by repeated cycle tests. Overall, it is believed the structure constructed based on the regulation strategy of the interlayer channel would enable the application of promising metal–organic frameworks in industrial gas separation processes.

Efficient CH4 separation and vapor uptakes in a porous MOF featuring 2D interlaced channels: experiment and simulation exploration

A novel porous MOF [In0.5(dcpia)0.5·2H2O·2DMF·(Me2NH2)0.5]n (1) was successfully built by utilizing flexible 4-(3′,5′-dicarboxylphenoxy)isophthalic acid (H4dcpia) and In3+ ion, which shows a 3D porous structure with 2D perforating pore, and the unique polar pore environment result in high C2H2, CO2 and vapor uptakes together with high gas affinity and CH4 separation performances, which was further certified by IAST calculation, breakthrough curves and theoretical simulations. Moreover, GCMC simulations pointed out that different interactions between framework and gas are the reason for dissimilarity in adsorption process.

Large‐area vacuum‐treated ZIF‐8 mixed‐matrix membrane for highly efficient methane/nitrogen separation

AbstractDevelopment of materials with excellent separation performances remains an ongoing challenge in methane/nitrogen (CH4/N2) separation science. Herein, a facile and effective method for enhancing CH4 uptake, binding, and CH4/N2 selectivity using the surface‐carbonized and stiffened zeolitic imidazolate framework‐8 (CSZ) via high‐vacuum‐resistance calcination (HVRC) was demonstrated. Such vacuum‐treated CSZ nanoparticles, with carbonized structures that contain Zn‐rich sites, high stability, and satisfactory compatibility with polymers, were then uniformly mixed with the strong basic polymer polyvinylamine (PVAm) to obtain large‐area mixed‐matrix membranes (1120 cm2, which is ca. 2 pieces of A4‐size paper). Owing to the presence of Zn‐rich sites and amino groups, CH4 molecules were bound more readily to CSZ and PVAm than N2, as confirmed by gas adsorption isotherms and DFT calculations. The obtained MMM modules (ca. 2000 cm2) exhibited outstanding CH4 separation performances at 85 wt% CSZ loading, achieving a CH4 permeance of 7600 GPU and CH4/N2 selectivity of 4.35.

Multicomponent adsorptive separation of CO2, CH4, N2, and H2 over M-MOF-74 and AX-21@M-MOF-74 composite adsorbents

To develop an efficient hydrogen purification adsorbent, M-MOF-74 (M = Mg, Co, Ni, Zn and Cu) was synthesized by hydrothermal method, and super activated carbon (AX-21) was incorporated to form a new type of porous material for H2 purification from COG. Prepared samples were characterized by physical and structural properties and then compared by adsorption equilibrium. The dynamic adsorption performance of the materials during H2 purification was comprehensively evaluated by binary, multi-component measurements and multi-component breakthrough profiles. Adsorption isotherms were used to estimate selectivity values for CO2/H2, CH4/H2, N2/H2 and (CO2 + CH4 + N2)/H2. The results show that Mg-MOF-74 has the largest selectivity value among M-MOF-74. AX-Mg-MOF-74 incorporated with AX-21 at a mass ratio of 0.15 exhibited an average 30.88% increase in CO2, CH4, N2 and H2 adsorption capacity compared to pure Mg-MOF-74. In addition, the mean selectivity values for CO2/H2, CH4/H2, N2/H2 and (CO2 + CH4 + N2)/H2 are increased by 8.3%, 6.8%, 47.7% and 11.0% respectively.

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.

Fluorinated covalent triazine frameworks for effective CH4 separation and iodine vapor uptake

In this article, analogous covalent triazine framework (CTFs) were simply prepared through the trimerization of different nitrile building blocks (tetrafluoroterephthalonitrile or terephthalonitrile) under typical ionothermal conditions. We demonstrated that the fluorine contents could be simply altered by changing the comonomer compositions. Introducing fluorine could adjust the pore size distribution and electron structure of the network effectively. By increasing fluorine contents, an enhanced CO2/CH4 selectivity up to 15.5 was presented. Additionally, electron-concentrated fluorine strengthened CH/π interactions between the polymeric matrixes and guest CH4, offering a CH4/N2 selectivity up to 8.0. The obtained CTFs also exhibited noticeable iodine adsorption capacity in vapor phase (302 wt%) due to their abundance of heteroatoms and porosity. These results clearly demonstrated the promising aspect of introducing fluorine groups into the porous networks for developing efficient sorbent towards potential applications in separating methane gas or iodine vapors and also affording further insight into the development of high performance functional polymers.

Separation of methane and nitrogen using ionic liquidic zeolites by pressure vacuum swing adsorption

AbstractThe separation of methane (CH4) and nitrogen (N2) is a significant challenge to the enrichment and utilization of low concentration CH4 due to the similarity in the physical and chemical properties of the two molecules. In this work, we investigated the separation of CH4 from N2 using 100 kg of a new ionic liquidic zeolite (ILZ) material in a 6‐bed pilot‐scale pressure swing adsorption process. Feed gases with CH4 concentrations of 5.0% and 16.1% were upgraded to 11.5% and 34.6%, respectively, with CH4 recoveries higher than 80%. The pilot test results were used to anchor a numerical model that then allowed the efficient investigation of multiple operational parameters including desorption pressure and feed gas flow rates. The numerical model produced CH4 concentrations for both product streams consistent with those measured in the pilot experiments, with root mean square deviations below 2%. The modeling results revealed that sufficiently low desorption pressures can unexpectedly lead to lower heavy product purities under limited feed gas flow conditions. Furthermore, the optimum feed gas flow rate under which maximum heavy product purity is achieved increases with lower desorption pressure. The maximum CH4 concentrations increased from 31.8% to 41.5%, as desorption pressures decreased from 22.8 to 12.2 kPa for optimum feed flow rates between 78.2 and 105.5 mol/h. We also demonstrate a method of process optimization based on the bed capacity ratio, ℂ, which provides a scale‐independent measure of the degree to which the column is being used effectively. By varying feed flow rate and/or desorption pressure, ℂ values between 0.2 and 0.8 were explored, with maxima in the combined separation performance metric (methane recovery) × (methane purity) occurring for values of ℂ in the range 0.29–0.36. This separation performance optimization by adjusting ℂ provides an effective strategy for integrating and understanding the impact of multiple operating parameters.

Fine-tuning of pore-space-partitioned metal-organic frameworks for efficient C2H2/C2H4 and C2H2/CO2 separation

Acetylene (C2H2) and ethylene (C2H4) both are important chemical raw materials and energy fuel gasses. But the effective removement of trace C2H2 from C2H4 and the purification of C2H2 from carbon dioxide (CO2) are particularly challenging in the petrochemical industry. As a class of porous physical adsorbent, metal-organic frameworks (MOFs) have exhibited great success in separation and purification of light hydrocarbon gas. Herein, we rationally designed four novel MOFs by the strategy of pore space partition (PSP) via introducing triangular tri(pyridin-4-yl)-amine (TPA) into the 1D hexagonal channels of acs-type parent skeleton. By modulating the functional groups of linear dicarboxylate linkers for the parent skeleton, a series of isoreticular PSP-MOFs (SNNU-278−281) were successfully obtained. The synergistic effects of suitable pore size and Lewis basic functional groups make these MOFs ideal C2H2 adsorbents. The gas adsorption experimental results show that all MOFs have excellent C2H2 uptakes. Specially, SNNU-278 demonstrates a high C2H2 uptake of 149.7 cm3/g at 273 K and 1 atm. Meanwhile, SNNU-278−281 MOFs also show extremely great C2H2 separation from CO2 and C2H4. The optimized SNNU-281 with high-density hydroxy groups exhibits extraordinary C2H2/CO2 and C2H2/C2H4 dynamic breakthrough interval times up to 31 min/g and 17 min/g under 298 K and 1 bar.

Nickel-Based Metal-Organic Frameworks for Coal-Bed Methane Purification with Record CH4 /N2 Selectivity.

The enrichment and purification of coal-bed methane provides a source of energy and helps offset global warming. In this work, we demonstrate a strategy involving the regulation of the pore size and pore chemistry to promote the separation of CH4 /N2 mixtures in four nickel-based coordination networks, named Ni(ina)2 , Ni(3-ain)2 , Ni(2-ain)2 , and Ni(pba)2 , (where ina=isonicotinic acid, 3-ain=3-aminoisonicotinic acid, 2-ain=2-aminoisonicotinic acid, and pba=4-(4-pyridyl)benzoic acid). Among them, Ni(ina)2 and Ni(3-ain)2 can effectively separate CH4 from N2 with top-performing performance because of the suitable pore size (≈0.6 and 0.5 nm) and pore environment. Explicitly, Ni(ina)2 exhibits the highest ever reported CH4 /N2 selectivity of 15.8 and excellent CH4 uptake (40.8 cm3 g-1 ) at ambient conditions, thus setting new benchmarks for all reported MOFs and traditional adsorbents. The exceptional CH4 /N2 separation performance of Ni(ina)2 is confirmed by dynamic breakthrough experiments. Under different CH4 /N2 ratios, Ni(ina)2 selectively extracts methane from the gaseous blend and produces a high purity of CH4 (99 %). Theoretical calculations and CH4 -loading single-crystal structure analysis provide critical insight into the adsorption/separation mechanism. Ni(ina)2 and Ni(3-ain)2 can form rich intermolecular interactions with methane, indicating a strong adsorption affinity between pore walls and CH4 molecules. Importantly, Ni(ina)2 has good thermal and moisture stability and can easily be scaled up at a low cost ($25 per kilogram), which will be valuable for potential industrial applications. Overall, this work provides a powerful approach for the selective adsorption of CH4 from coal-bed methane.

Recovery of helium from natural gas using MFI membranes

The development of more efficient technology for the production of helium from natural gas is pressing as the current resources are dwindling. In the present work, ultra-thin MFI membranes were evaluated for the separation of an equimolar CH 4 /N 2 /He mixture in a wide temperature range 120–293K. The membrane was highly selective towards CH 4 and N 2 at all the investigated conditions, which resulted in a helium rich retentate. The observed selectivity should be a result of selective adsorption of CH 4 and N 2 . A maximum (CH 4 +N 2 )/He separation factor of 152 was observed at 153 K and a feed pressure of 3 bar and a permeate pressure of 0.2 bar. At these conditions, separation factors were 265 and 38 for CH 4 /He and N 2 /He, respectively, and the CH 4 and N 2 fluxes were 1.12 and 0.16 mol/(m 2 ⋅s), respectively. To the best of our knowledge, these are the best results reported in the open literature for the recovery of helium from natural gas using membrane technology. The high selectivity and flux indicated that the ultra-thin MFI membranes are a promising candidate for efficient helium production from natural gas. • Separation of CH 4 /N 2 /He mixture was performed in the temperature range 120–293K. • The membrane was highly selective towards CH 4 and N 2 at low temperature. • A maximum (CH 4 +N 2 )/He separation factor of 152 was observed at 153 K. • The separation factors were 265 and 38 for CH 4 /He and N 2 /He, respectively, at 153K.

High performance of PES-GNs MMMs for gas separation and selectivity

In this study, graphene nanosheets (GNs) were incorporated into polyethersulfone (PES) by phase inversion approach for preparing PES-GNs mixed matrix membranes (MMMs). To investigate the impact of filler content on membrane surface morphology, thermal stability, chemical composition, porosity and mechanical properties, MMMs were constructed with various GNs loadings (0.01, 0.02, 0.03, and 0.04 wt%). ​The performance of prepared MMMs was tested for separation and selectivity of CO2, N2, H2 and CH4 gases at various pressures from 1 to 6 bar and temperature varying from 20 to 60 °C. It was observed that, compared to the pristine PES membrane, the prepared MMMs significantly improved the gas separation and selectivity performance with adequate mechanical stability. The permeability of CO2, N2, H2 and CH4 for the PES + 0.04 wt% GNs increases from 9 to 2246, 11 to 2235, 9 to 7151, and 3 to 4176 Barrer respectively, as compared with pure PES membrane at 1 bar and 20 °C due to improving the membrane absorption and porosity. In addition, by increasing the pressure, the permeability and selectivity of CO2, N2, H2 and CH4 are increased due to the increased driving force for the transport of gas via membranes. Furthermore, the permeability of CO2, N2, H2 and CH4 increased by increasing the temperature from 20 to 60 °C due to the plasticization in the membranes and the improvement in polymer chain movement. This result proved that the prepared membranes can be used for gas separation applications.

Potential and design of imine-linked two-dimensional covalent organic framework membranes for Ethane/Methane separation

Membrane separation of CH4 and C2H6 is challenging due to the similar kinetic diameter and chemical affinity. In comparison with other crystalline porous materials, covalent organic frameworks (COFs) possess the advantages of low density, large surface area, tunable pore structure, versatile functionality, and so on, providing the COFs with great potential as separation membranes. Herein, we studied the membrane-based C2H6/CH4 separation performance of 80 two-dimensional imine-linked COFs. Monte Carlo and molecular dynamics simulations were employed to investigate the adsorption and diffusion of gas molecules in the COF membranes. 7 promising COF structures are screened by evaluating the membrane’s selectivity and permeability, and they are found to have small pore size (<20 Å), void fraction (<0.7), and surface area (<8000 m2·g−1) as well as high framework density (>200 kg·m−3). Pore size and framework density are demonstrated to be dominating factors in determining the selectivity and permeability. Based on two typical COFs, COF-LZU1 and NUS-15, grafting hydrocarbons onto the linker and introducing high-carbon additives into the pore can effectively improve the separation performance. Especially, with an appropriate additive concentration, the fullerenes can increase the C2H6/CH4 selectivity by>10 times. This work aims to explore the potential of COFs as membranes for C2H6/CH4 separation, and provides design strategies to optimize the separation performance, which are also applicable to other porous materials.

Study on the advantageous effect of nano-clay and polyurethane on structure and CO2 separation performance of polyethersulfone based ternary mixed matrix membranes

In recent years, many efforts have been made to develop new membrane materials for natural gas sweetening (CO2/CH4) and post-combustion CO2 capture from flue gas (CO2/N2), especially in coal-fired and natural gas-fired power plants. This study focused on the effect of polyurethane and nano-clay on structure and CO2 separating properties of polyethersulfone (PES) based three-component mixed matrix membranes (MMMs). The different weight fractions polyurethane (PU) (5−30 wt.%) together with clay nano-sheets (Cloisite® 15A) (0.5−10 wt.%) were blended to fabricate a novel PES-based ternary MMMs. The principal purpose was to investigate the effect of loading PU polymer and layered clay particles with 2D channels on the gas separation performance of the PES membranes. Pure gas permeability for N2, CH4, and CO2, and ideal gas separation for CO2/N2 and CO2/CH4 mixtures were examined through neat PES and modified PES membranes. By incorporating 20 wt.% of PU into PES, the permeability of CO2 and selectivities of CO2/N2 and CO2/CH4 were improved by 4, 1.4, and 1.7 times higher than the neat PES membrane, while by loading 20 wt.% of PU and 2 wt.% of nano-clay, the CO2 permeability, and CO2/N2, and CO2/CH4 selectivities were improved by 7.8, 1.8, and 2.2 times higher than the neat membrane, respectively. In general, PU and clay nano-sheets together as a filler into the PES matrix exhibited a meaningful improvement in the gas permeation and separation properties of PES and can be admitted as a worthy membrane for CO2 separation from the flue gas and natural gas.

A Microporous Metal-Organic Framework with Channels Constructed from Nonpolar Aromatic Rings for the Selective Separation of Ethane/Ethylene Mixtures.

The separation of ethane and ethylene is an important segment in the purification of chemical raw materials in industrial production. However, due to their similar physical and chemical properties, the separation of C2 H6 /C2 H4 is challenging. Herein, we report the selective adsorption of ethane over ethylene by a microporous metal-organic framework with nonpolar aromatic rings constructed channels, [Co1.5 (TATB)(H2 O)0.5 ] ⋅ 5DMA ⋅ 3H2 O (Co-TATB, H3 TATB=4,4',4''-(s-triazine-2,4,6-triyl) tribenzoic acid). This compound showed a higher ethane capacity than that of ethylene, and a low adsorption enthalpy of ethane only of 19.4 kJ mol-1 . Further, the dynamic breakthrough experimental confirmed that Co-TATB can selectively adsorb ethane from ethane/ethylene separation.