Separation Performance Research Articles

Influence mechanism of hydrocyclone main diameter on separation performance

The main diameter of hydrocyclone (HC) has significant effects on separation performance. However, the differences of flow field characteristics within different HCs have not been understood well yet, which makes it impossible to grasp the influence mechanism of the main diameter on the separation performance. Through the study of the migration trajectories of particles, it is found that the greater the diameter and the finer the particles, the more particles escape from the overflow outlet. The relationships between the longest residence time and the HC main diameter for particles with 10 and 15 μm were, respectively, clarified. The high-speed video and particle image velocimetry experiments were performed and found although the main diameter of a large-HC (LHC) is twice that of a mini-HC (MHC), its air-core diameter is much larger than twice that of MHC, which is not beneficial for separations. The axial velocity around the central axis area in LHC is higher than that of the MHC, which helps separate low-density discrete phases from the overflow outlet at a faster speed but not for the separations of high-density discrete phases from the underflow outlet. The angle of the locus of zero vertical velocity in MHC is larger than that of LHC, which is anticipated to enhance the separation efficiency for the high-density discrete phase. This study first reveals the influence mechanism of the HC main diameter on its separation performance from the perspective of the flow field characteristics, which would hopefully provide significant references for the applications of HCs.

Preparation of carboxyl-functionalized silica core-shell microspheres and their applications in weak cation exchange chromatography, heavy metal removal, and lysozyme enrichment.

Chromatography is a technique of separation based on adsorption and/or interaction of target molecules with stationary phases. Herein, we report the design and fabrication of BTDA@SiO2 core-shell microspheres as a new class of stationary phase and demonstrate its impressive performance for chromatographic separations. The silica microspheres of BTDA@SiO2 were synthesized by in situ method with 1,3,5-benzenetricarboxaldehyde and 3,5-diaminobenzoic to separate peptides and proteins on high-performance liquid chromatography. The BTDA@SiO2 core-shell structure has a high specific surface area and retention factor of 4.27 and 8.31 for anionic and cationic peptides, respectively. The separation factor and resolution were high as well. A typical chromatogram illustrated nearly baseline resolution of the two peptides in less than 3 min. The BTDA@SiO2 was also highly stable in the pH range of 1 to 14. Furthermore, the prepared BTDA@SiO2 core-shell material not only be used for chromatographic separation but also as heavy metal removal from water. Using a BTDA@SiO2, we also achieved a lysozyme enrichment with a maximum saturated adsorption capacity reaching 714mg/g. In summary, BTDA@SiO2 has great application prospects and significance in separation and purification systems.

ANALYSIS OF EXPERIMENTAL TEST RESULTS OF CURRENT AND NEW COMPOSITION COLONS

In the process of separating cotton fiber from seed in a sawed fiber separator, the formation of raw material depends on several factors. The most important of them are the speed of rotation of the raw material, fiber, density, the amount of seeds separated from the fiber, etc. In addition, it is necessary to take into account the force of friction created by the walls of the working chamber due to the pressure created in the raw material. A high coefficient of friction of the colossal working surface has a negative effect on work efficiency, in particular, frictional forces cause the seed separated from the fiber to remain on the colossal working surface. These factors have an effect on the performance of the fiber separator and the quality of the extracted fiber. It is known that in the process of ginning, 25% of the fiber and seeds separated from the fiber remain in the raw material pile, causing mechanical damage. The main goal of the research is to prevent fiber and seed damage in the process of separating cotton fiber from the seed by installing a colosnik structure with the new recommended composition, to increase the efficiency of the seed exit from the working chamber, and at the same time to study ways to reduce energy consumption during the ginning process. This research paper presents an analysis of the results obtained after installing one of the working parts of the gin machine on the DL-10 gin machine of the existing and recommended composition of colosniks. The main purpose of introducing the new construction is to increase the efficiency of the DL-10 gin machine of the society, to develop it by filling it with new technologies, and to obtain quality fiber and seed.

Investigation of resistance performance of anti-icing wave-plate separators for marine gas turbines intake system

Abstract Due to their high power and efficiency, gas turbines are commonly used propulsion systems in hovercraft propulsion systems. In polar and cold marine environments, when a hovercraft rises, a significant number of droplets are generated on the water surface and are drawn into the gas turbine’s air intake with the cold air. This paper takes the structure of the original wave-plate separator as a reference and designs two structures: the rhombic anti-icing wave-plate separator (RAWS) and the streamlined anti-icing wave-plate separator (SAWS). Experimental and numerical simulation methods are employed to calculate the air intake resistance of the two structures at speeds ranging from 1 to 10 m/s. The results show that the K-ε standard enhanced wall function turbulent model is the closest to experimental measurements, with all calculated results having an error below 5%, demonstrating reliability. Compared to RAWS, the calculated total pressure loss for the SAWS structure decreases by 200 Pa under a designed air intake velocity of 7 m/s, representing a relative reduction of 40.8%. This provides a valuable reference for the design and resistance optimization of ship air intake anti-icing devices.

Detection of myclobutanil and tebuconazole in apple using magnetic molecularly imprinted polymer surface-enhanced Raman spectroscopy

The main challenge in Raman detection of pesticide residues in agricultural products is matrix interference, which hinders accurate identification of trace compounds in complicated agricultural samples. In this study, a novel surface-enhanced Raman spectroscopy approach based on magnetic molecularly imprinted polymers (MMIP-SERS) was introduced for the rapid analysis of myclobutanil and tebuconazole in apples. The synthesized magnetic molecularly imprinted polymer selectively adsorbed triazole pesticides, effectively eliminating matrix interference in real samples. The saturation adsorption time for MMIPs was only 10 min. In addition, the synthesized colloidal gold served as an excellent substrate for enhancing the specific signals for myclobutanil and tebuconazole. We successfully identified the characteristic peak of tebuconazole at 1089 cm−1, while myclobutanil showed its characteristic peak at 632 cm−1. The series of experiments and recovery tests confirmed the high sensitivity of the developed MMIP-SERS method using colloidal gold as an enhanced substrate for fungicide analysis in apple samples. The linear detection ranges for myclobutanil and tebuconazole in apples were determined to be 0.2–10 mg/kg and 0.5–10 mg/kg, respectively. The limit of detection was 0.09 mg/kg for tebuconazole and 0.05 mg/kg for myclobutanil. This study provides a rapid and simple method for detecting myclobutanil and tebuconazole based on the synergistic effect of the imprinted polymer and SERS with good separation and detection performance.

Biomimetic designing MOFs nanosheet based membranes with self-recovery two-dimensional selective channels for specific molecules long-lasting precise separation

Two-dimensional (2D) materials-based membranes with artificial transfer channels have shown significant potential for selective separation. However, the challenges such as uncontrollable interlayer spacing and undesirable molecular sieving capabilities of 2D channels have impeded their further application in separation. Inspired by biological selectivity transport channels with proper steric and affinity sites, herein we have designed biomimetic 2D selective transport channels based on a ZIF-L nanosheet membrane. In this design, the UiO-66-NH2 nanoparticles tune the appropriate interlayer confinement and compensate for laminate framework defects of 2D selectivity transport channels, the artificial imprinting recognition sites establishes the essential chemical environment for specific separation. As a result, the obtained MOFs nanosheet based membranes with imprinted recognition sites (MN-IMs) exhibited enhanced permeation flux (J = 1.0847 × 10−3 and 1.0423 × 10−3 mg min−1 cm−2) and permselectivity (α = 3.77 and 4.10), outperforming state-of-the-art similar technologies. Besides, the composite MOFs demonstrated good photoinduced self-recovery ability, which also enables MN-IMs to have long-lasting selective separation performance (the separation efficiency is 90.76 %) in the continuous separation process. This study introduces a novel design strategy for developing sophisticated 2D materials-based membranes and offers new insights into the precise separation of specific molecules.

Influence of polar solvent in formation and organic solvent separation performance of novel fluorine-containing polyamide membranes

Polyamide thin film composite (PA-TFC) membranes have shown great potential in organic solvent separations. However, the intrinsic polar feature of the amide group limits their permeability to specific solvents, such as nonpolar solvents. In this study, we used a fluorine-containing monomer [4,4′-oxybis(3-(trifluoromethyl)aniline), OTFA] to conduct interfacial polymerization (IP) with trimesoyl chloride, resulting in the fabrication of novel PA-TFC membranes with permeability to both polar and nonpolar solvents. Interestingly, by simply adjusting the composition of OTFA solvents [DMF and DMF/water (1:1, v: v)], we obtained two PA-TFC membranes (OTFA-D and OTFA-DH, respectively) featuring completely different structures and surface properties, including PA layer thickness, water contact angle, surface element composition, surface charge, and polarity. Due to their distinct structures and surface features, the two membranes exhibited different performances in organic solvent nanofiltration (OSN). The OTFA-DH membrane showed higher permeability to polar solvents (e.g., methanol), while the OTFA-D membrane was more permeable to nonpolar solvents (e.g., toluene). The mechanism on the formation of the two PA layers was clarified by combining the experimental results with the molecular dynamics simulations. The significantly different interfacial properties and monomer diffusion during IP led to the substantial differences in the formation of the PA network. This work provides a strategy to fabricate tailored PA-TFC membranes for various OSN scenarios by simply adjusting the solvent compositions.

Preparation of PVDF-nSiO2/PVSQ high-flux composite membrane by chemical grafting and separation of composite brine by membrane distillation

The large-scale application of membrane distillation (MD), an important method for desalting seawater, is limited due to membrane fouling. In this study, ethyl orthosilicate (TEOS) was polymerized to obtain different nSiO2 particles. Vinyl triethoxysilane (VTES) was hydrolysed and polycondensation was used to produce spherical polyethylene-sesquioxane (PVSQ) microparticles, which were modified to construct micro/nano particles. Then grafted on the surface of polyvinylidene fluoride (PVDF) composite membrane. The low-surface-energy hydrophobic groups present on the surfaces of the vinyl and ethoxy particles greatly enhanced the membrane hydrophobicity. The particle size of nSiO2 can change the properties of the membrane. The separation performance of the membrane was tested by direct contact membrane distillation (DCMD). In the separation of a constant concentration of feed solution (3.5wt% NaCl), the membrane flux was relatively stable at 23.8kg·m−2·h−1, and the salt interception rate reached 99.99%. In the subsequent separation of a salt/humic acid solution, the flux remained stable and the good anti-fouling performance indicating that this system outperformed the unmodified membrane. Finally, the effect of different cations on the water diffusivity was studied using a molecular simulation method. Both Ca2+ and Mg2+ reduced the diffusion coefficient of water. However, when these two ions were present simultaneously, Ca2+ inhibited the binding of Mg2+ to water, and the diffusion coefficient of water increased. This study provides a novel approach for preparing hydrophobic membranes for the separation of complex brines.

Optimizing COF crystallinity for high-resolution GC separation

This research explores the influence of crystallinity on gas chromatographic (GC) separation using covalent organic frameworks (COFs) as stationary phases. Three COF materials (CTF-DCBs) with varying crystallinity were synthesized and characterized. CTF-DCB-1, with superior crystallinity, demonstrated high-selectivity GC separation of benzene isomers as well as styrene/phenylacetylene mixtures, while CTF-DCB-2 and CTF-DCB-3 exhibited lower crystallinity and worse separation performance. Thermodynamic and kinetic tests showed that CTF-DCB-1 had the worst thermodynamic adsorption but low diffusion mass transfer resistance, which resulted in the best separation. Therefore, optimizing the crystallinity of COFs is necessary for balancing the kinetic diffusion and thermodynamic interactions towards the analytes, achieving high-performance GC stationary phases.

Covalently modified MoS2 for the fabrication of interlayered thin film composite membranes with excellent structural stability against swelling and drying in organic solvent nanofiltration

Thin film nanocomposite (TFNi) membranes interlayered with 2D nanomaterials are promising for organic solvent nanofiltration (OSN) applications. However, swelling and drying problems can arise due to the instability of the 2D nanomaterial interlayer in different solvents and humidity conditions. To address this issue, covalently modified molybdenum disulfide (MoS2) nanosheets (MoS2–COOH and MoS2–CONH2) were used as interlayers in the fabrication of TFNi membranes. The covalent groups acted as spacers to stabilize the interlayer spacing of the MoS2 interlayer and regulate its structural stability in diverse solvents and drying conditions. The TFNi membranes interlayered with MoS2–COOH and MoS2–CONH2 nanosheets demonstrated excellent structural stability and maintained their high permeance even after exposure to various solvents and drying conditions. The TFNi-MoS2-CONH2 membrane exhibited the highest permeance of 8.60 ± 0.23 L m−2 h−1 bar−1 for MeOH, with a high rejection of 87.1 ± 1.3 % for Evans Blue (EB). Furthermore, the TFNi membranes exhibited sustained separation performance throughout the 72 h test, demonstrating their structural stability. This study highlights the potential of TFNi membranes interlayered with covalently modified MoS2 nanosheets for OSN applications, providing high permeance and structural stability in diverse solvents and drying conditions.

Biogas upgrading to biomethane with zeolite membranes: Separation performance and economic analysis

Biogas represents an important renewable source alternative to fossil fuels, which can significantly contribute to the reduction of global warming and the gradual decarbonisation. In this work, the purification of CH4 and CO2 from a biogas mixture was investigated using DD3R zeolite membrane modules, as a possible solution to replace the traditional techniques at higher environmental impact (i.e., solvent absorption and cryogenic distillation). Multistage membrane configurations operating at 25°C and 30 bar were proposed and explored to get highly pure biomethane (concentration of 98 %) and carbon dioxide (concentration of 99.5 %), imposing a recovery of both the species higher than 90 %. Then, an economic analysis was carried out, evaluating the economic potential of each configuration as a function of several parameters, such as membrane module cost, biomethane selling price, CO2 permeance, CO2/CH4 selectivity, feed flow rate and pressure. The multistage schemes were found to be promising in a wide range of zeolite membrane module cost (i.e., up to 2000 $/m2), providing positive values of the economic potential, due to the good recovery of both the components, which produced high revenues. The increment of the CO2 permeance and, especially, of the feed flow rate (i.e., plant size) allowed for a more profitable process. In particular, if feed flow rate increased from 100 to 1000 Nm3/h, the economic potential would grow of about 12 times, from 113 to 1370 thousand dollars per year. Hence, this preliminary economic assessment showed that zeolite membranes can be successfully used in biogas treatment to get pure CH4 and CO2. Such an analysis can be applied to any membrane materials, once permeance and selectivity are fixed.

Measuring cells as a potential tool for the design and retrofit of columns with structured packings

In-depth experiments regarding the separation performance and pressure drop within a novel measuring cell, for the determination of structured packing characteristics for distillation processes, are presented. Furthermore, experiments with a pilot plant column (DN 250) were conducted and compared to the retrieved results from the measuring cell. Additionally, mass transfer coefficients were obtained from the conducted separation performance measurements of the measuring cell through a rate-based model. These coefficients were then used to predict the separation performance of a DN 250 column with an accuracy as good as using the Delft model for the prediction of the mass transfer coefficients. After introducing a maldistribution factor, the prediction of the separation performance of the DN 250 column with the measuring cell mass transfer coefficients could be significantly improved. Changing the packing type within the measuring cell revealed that the measuring cell can give reliable and reproducible results for packings with specific surface areas of 500m2m−3 and 250m2m−3, while at the same time investigating a close boiling system. The presented results indicate that the measuring cell is a promising tool for supporting the retrofit and design of columns with structured packings.

Mixed matrix membranes consisting of PDMS and IL@MoS2 for enhancing 2-phenylethanol pervaporation separation

The MoS2-based mixed matrix membranes (MMMs) exhibited excellent pervaporation separation for aromatic compounds, but the narrow interlayer spacing and few affinity sites in MoS2 limited the simultaneous improvement in the total flux and separation factor. Therefore, constructing 2-PE transport channels and affinity sites in MMMs is of significant importance to improve the pervaporation separation performance. Herein, 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (IL) was intercalated into the interlayer of the molybdenum disulfide (MoS2) under electrostatic and concentration diffusion interactions to obtain IL@MoS2. Then, IL@MoS2 was incorporated into polydimethylsiloxane (PDMS) to prepare MMMs for efficient 2-PE separation, which had good miscibility with polymer matrix. The total flux, separation factor and pervaporation separation index of as-prepared MMMs reached 1466 g m−2 h−1, 33 and 47,571 g m−2 h−1, separately, which increased by 26 %, 31 % and 44 % compared with that of PDMS embedding with MoS2. This is because IL@MoS2 in MMMs not only can afford 2-PE transport channels, but also provide 2-PE affinity sites due to the hydrogen bonds and π-π interactions, which promotes the solubility of 2-PE in MMMs. When the concentration of maltol increased to 1500 ppm in 2-PE aqueous solution, the 2-PE flux and separation factor of 2-PE/water only decreased by 23 % and 26 %, revealing that MMMs had good 2-PE selectivity in 2-PE/maltol/water mixture. In addition, it displayed exceptional durability during 168 h testing, demonstrating that this membrane had a good application prospect for 2-PE separation.

GO and surfactant assisted regulation of polyamide nanofiltration membranes for improved separation performance

Fabricating nanofiltration membranes with high water permeance and selectivity by tailoring the structure and morphology is crucial to efficient water purification. In this work, the fabrication of thin film nanocomposite (TFN) nanofiltration membranes by combining two methods, the surfactant-assembly interfacial polymerization (SARIP) and the addition of graphene oxide (GO) or ionic liquid functionalized graphene oxide (GO-IL) for the preparation of the selective PA layer on a novel porous substrate is reported. For the preparation of the porous substrate, mechanically robust, aromatic polyethers containing polar pyridine units (PDSPP) were chosen targeting to improved hydrophilicity and thus enhanced water permeability. The anionic sodium dodecyl sulfate (SDS) surfactant was used to regulate the interfacial polymerization thereby enabling the formation of dense PA layers with high cross-linking degree and consequently high salt rejections. On the other hand, the addition of GO/GO-IL nanosheets could impart hydrophilicity and antifouling properties. The novel porous PDSPP substrate was selected for the fabrication of TFN membranes due to its improved water permeability and superior salt rejection and increased hydrophilicity compared to commercial PSf substrate. The detailed study of the fabricated TFN membranes by ATR-FT-IR, SEM, AFM, XPS, contact angle measurements revealed the formation of polyamide selective layers with rougher surfaces, increased hydrophilicity and high cross-linking degrees (from 44 % to 94 %), resulted from the synergistic effect of SDS and GO incorporation. Moreover, the prepared TFN membranes exhibited high salt rejections while maintaining a moderate water permeability. In particular, the membrane containing the neat GO (TFNGO50) displayed excellent Na2SO4 and MgSO4 rejections (98.8 % and 99.5 %, respectively) while the NaCl rejection was 47.0 % and a water permeability value of 4.2 L m-2h−1 bar−1. The divalent salt rejections were among the highest values reported in the literature in comparison with commercial NF membranes and TFN membranes containing GO/functionalized GO. When GO-IL nanosheets were embedded in the PA layer, the water permeability was slightly improved while the salt rejections were significantly reduced compared to TFNGO50. Lastly, the incorporation of GO enhanced the anti-fouling properties of the prepared membranes due to increased hydrophilicity of the PA surface.

Solvent-responsive switching wettability of superoleophobic/superhydrophilic quartz sand filter medium facilitates rapidly oil/water separation and demulsification

Oil-spill accidents occur frequently, and the oil pollution caused by oil spills is attracting extensive attention from all circles of society. To resolve this problem, solvent-responsive superoleophobic/superhydrophilic quartz sand (SSQS) was manufactured by introducing ZnO nanoparticles, short-chain fluorinated compounds, and hydrophilic-induced units into the surface of quartz sand. Experimental results showed that SSQS can reversibly convert the superoleophobic/superhydrophilic surfaces into superoleophilic/underoil superhydrophobic surfaces within 10 s. The solvent-responsive surface of SSQS demonstrated selective separation performance for mixtures of oil/water and various surfactant-stabilized oil-in-water emulsions and water-in-oil emulsions before and after wettability conversion. Oil/water solutions were separated synchronously and continuously using the "┴" type of oil/water separating system, with a separation efficiencies of 99.33 % at high flux. After ten runs of the wettability transition, the oil/water mixture's separation efficiency remained over 99 %. More importantly, SSQS can accomplish the on-demand, gravity-driven demulsification and separation of oil/water emulsions with excellent separation efficiency and flux. The directional migration of oil droplets on the SSQS surface could possibly be described by the wetting performance of oil phase on the special wettability surface, and the solvent-responsive wettability transition of the SSQS surface. SSQS also exhibited brilliant mechanical durability, anticorrosion ability, and wetting stability under severe conditions. Therefore, this work provided a new research direction for the reversible wettability transition of granular filter media.

Rapid and accurate identification of effective metal organic frameworks for tetrafluoromethane/nitrogen separation by machine learning

BackgroundEffectively capturing tetrafluoromethane (CF4), a notorious greenhouse gas having a greenhouse warming potential 6630 times higher than carbon dioxide, is important to mitigate climate change. Metal organic frameworks (MOFs) are promising adsorbents to entrap CF4 with extreme high selectivity because they contain versatile functionalized ligands and tunable pores. However, the large population makes experimental methods unpractical to perform the large-scale screening and rational selection of efficient MOFs. MethodsIn this work, an intelligent method based on machine learning was developed to identify the important features of MOFs governing their CF4/N2 separation performances and establish the relationship between these features and performance metrics, including the CF4 adsorption capacity, the adsorption selectivity of CF4 over N2, and their trade-off. Significant findingsThe random forest (RF) machine learning algorithm was found to exhibit the highest accuracy in performance prediction. The heat of adsorption, the relative molecular mass of MOFs, and the density of MOFs were three critical features that influenced the CF4/N2 separation performances. These dominant features indicate that the pore geometry, framework geometry, and the interaction law between CF4 and MOFs significantly affected their CF4/N2 separation efficiency. Machine learning is thus a powerful tool to guide the design of CF4-selective MOFs and extend the applicability of machine learning among chemical and environmental communities.

A microchip gas chromatography column assembly with a 3D metal printing micro column oven and a flexible stainless-steel column

In this work, a microchip gas chromatography (GC) column assembly utilizing a three-dimensional (3D) printed micro oven and a flexible stainless steel capillary column was developed. The assembly's performance and separation capabilities were characterized. The key components include a 3D printed aluminum plate (7.50 × 7.50 × 0.16 cm) with a 3-meter-long circular spiral channel, serving as the oven, and the column coiled on the channel with an inner diameter of 320 μm and a stationary phase of OV-1. A heating ceramic plate was affixed on the opposite side of the plate. The assembly weighed 40.3 g. The design allows for easy disassembly, or stacking of heating devices and columns, enabling flexibility in adjusting column length. When using n-C13 as the test analyte at 140 °C, a retention factor (k) was 8.5, and 7797 plates (2599 plates/m) were obtained. The assembly, employing resistance heating, demonstrated effective separation performance for samples containing alkanes, aromatics, alcohols and ketones, with good reproducibility. The reduction in theoretical plates compared to oven heating was only 2.95 %. In the boiling point range of C6 to C18, rapid temperature programming (120 °C/min) was achieved with a power consumption of 119.512 W. The assembly was successfully employed to separate benzene series compounds, gasoline and volatile organic compounds (VOCs), demonstrating excellent separation performance. This innovative design addresses the challenges of the complexity and low repeatability of the fabrication process and the high cost associated with microchip columns. Furthermore, its versatility makes it suitable for outdoor analysis applications.

The influence of debromination and TR on the microstructure and properties of CMSMs

One unique challenging in achieving advanced carbon molecular sieve membranes (CMSMs) is tailoring their gas separation properties from the precursor. To clarify this, we designed two homo-polyimides with a bromine (PI-Br) and a hydroxyl (PI-OH) groups in the ortho position of imide group, and carbonized them into CMSMs at 550 °C (PI-Br-550 and PI-OH-550). There are debromination (510 °C) and carbonization occurred for PI-Br-550 whereas the PI-OH underwent thermally rearrangement (TR, 450 °C) and then pyrolysis to CMSM. After carbonization, both CMSMs showed excellent gas separation properties, with their CO2/CH4 separation performance surpassed the latest 2019 pure-gas and 2018 mixed-gas trade-off curves, additionally, the PI-Br-550 demonstrated a relatively smaller CO2 permeability (12462 vs 14,253 Barrer), lower PCO2 increment ratio (199 vs 1480), and less CO2/CH4 dropping ratio (69.7 to 45.5 vs 87.5 to 36.1) than the PI-OH-550 from their precursors. Their XPS, Raman, and WXRD characterization results indicated that debromination boosts the gas separation performance of CMSM by creating more ultra-micropore “plate” (pyrrolic-N of 36.0 % vs 19.0 %) and smaller d-spacing (3.89 vs 4.15 Å) than the TR precursor, which boosts the permeability of CMSM is due to the high stability of PBO intermediates that retarded the decomposition of the polymer main chian and caused some big pores. The above results provided a good route to get highly efficient CMSM by molecular designing of their precursors.

Ideal Cage‐like Pores for Molecular Sieving of Butane Isomers with High Purity and Record Productivity

Abstractn‐C4H10 and iso‐C4H10 are both important petrochemical raw materials. Considering the coexistence of the isomers in the production process, it is necessary to achieve their efficient separation through an economical way. However, to obtain high‐purity n‐C4H10 and iso‐C4H10 in one‐step separation process, developing iso‐C4H10‐exclusion adsorbents with high n‐C4H10 adsorption capacity is crucial. Herein, we report a cage‐like MOF (SIFSIX‐Cu‐TPA) with small windows and large cavities which can selectively allow smaller n‐C4H10 enter the pore and accommodate a large amount of n‐C4H10 simultaneously. Adsorption isotherms reveal that SIFSIX‐Cu‐TPA not only completely excludes iso‐C4H10 in a wide temperature range, but also exhibits a very high n‐C4H10 adsorption capacity of 94.2 cm3 g−1 at 100 kPa and 298 K, which is the highest value among iso‐C4H10‐exclusion‐type adsorbents. Breakthrough experiments show that SIFSIX‐Cu‐TPA has excellent n/iso‐C4H10 separation performance and can achieve a record‐high productivity of iso‐C4H10 (3.2 mol kg−1) with high purity (>99.95 %) as well as 3.0 mol kg−1 of n‐C4H10 (>99 %) in one separation circle. More importantly, SIFSIX‐Cu‐TPA can realize the efficient separation of butanes at different flow rates, temperatures, as well as under high humid condition, which indicates that SIFSIX‐Cu‐TPA can be deemed as an ideal platform for industrial butane isomers separation.

Controlling the curing process of novolac phenolic resin during preparation of carbon molecular sieve membrane for propylene/propane separation

A carbon molecular sieve (CMS) membrane was prepared for propylene/propane separation using a phenolic resin as a cost-effective polymer precursor. However, to achieve a desirable separation performance, the pre-treatment process of phenolic resin should be affordably carried out. In this study, novolac phenolic resin was cured with hexamine as a curing agent. The curing conditions were varied in terms of the curing time and concentration of the curing agent, both of which led to a higher degree of crosslinking of the phenolic resin, resulting in improved thermal stability. The propylene/propane separation factor of 6.33 for the CMS membrane derived from the phenolic resin cured for 1 h increased to 18.5 when the curing time was 4 h, whereas the propylene permeance decreased from 153 to 53.5 GPU. A similar trend was observed for higher concentrations of the curing agent. Moreover, the long-term stability of the CMS membrane was significantly improved after prolonged curing with a higher concentration of the curing agent. The CMS membranes derived from cured phenolic resins possess more selective carbon structures and better structural stabilities.