Carbon Molecular Sieve Research Articles

Dual-stage vacuum pressure swing adsorption for green hydrogen recovery from natural gas grids

Purification of green hydrogen (GH) from natural gas grids (NGG) can be expensive and challenging through a single-step Pressure Swing Adsorption (PSA) process due to the low H2 concentration in the grid (<20 % v/v). Herein, we report for the first time the design of a dual-stage vacuum pressure swing adsorption process (DS-VPSA) to purify H2 blended in NGG with a synergy action of two types of adsorbents: a Carbon Molecular Sieve 3K (CMS) in stage 1 and zeolite 13X in stage 2. In Stage 1, the CMS kinetically separates H2 from CH4, pre-concentrating H2 from 20 % to over 50–60 % (v/v), followed by Stage 2, where a thermodynamic separation with zeolite 13X achieves a final product with a high H2 purity content (>99 % v/v). A mathematical model is developed in Aspen adsorption, where numerical simulations are performed to establish the best operating conditions of the global DS-VPSA. A parametric study is also conducted to optimize performance parameters such as recovery, purity, productivity, and specific energy. The results indicate that it is possible to achieve a final H2 product with a purity of 99.97 % (fuel cell grade), a recovery of 67 %, and productivity of 1.60x10-2 kgH2/kgads/hr, and a total specific energy consumption of 10.06 MJ/kgH2, which is a significant achievement reported so far.

Leveraging molecular scale free volume generation to improve gas separation performance of carbon molecular sieve membranes

Carbon molecular sieve (CMS) membranes have proven to be promising candidates for next-generation gas separations. Modification of polymeric precursors is a critical tool that permits fine-tuning of CMS structure and performance for a wide variety of gas mixtures. Here, we make a targeted alteration to a polyimide CMS precursor through substitution of free-volume-generating trifluoromethyl groups for aliphatic methyl groups on the polymer backbone. Gas separation performance shows a vast improvement, demonstrated by up to an eightfold increase in gas permeability as well as higher mixed gas separation factors in some cases. We investigate these properties, and their dependence on pyrolysis temperature, with detailed measurements of gas sorption and permeation in CMS dense film membranes with additional analysis through classical materials characterization methods. Our observations indicate that addition of free-volume-generating groups into polymeric precursors is a powerful tool for developing state-of-the-art CMS membranes, especially in cases when high permeability is an important design parameter.

Precursor-chemistry engineering toward ultrapermeable carbon molecular sieve membrane for CO2 capture

Carbon capture is an important strategy and is implemented to achieve the goals of CO2 reduction and carbon neutrality. As a high energy-efficient technology, membrane-based separation plays a crucial role in CO2 capture. It is urgently needed for membrane-based CO2 capture to develop the high-performance membrane materials with high permeability, selectivity, and stability. Herein, ultrapermeable carbon molecular sieve (CMS) membranes are fabricated by pyrolyzing a finely-engineered benzoxazole-containing copolyimide precursor for efficient CO2 capture. The microstructure of CMS membrane has been optimized by initially engineering the precursor-chemistry and subsequently tuning the pyrolysis process. Deep insights into the structure-property relationship of CMSs are provided in detail by a combination of experimental characterization and molecular simulations. We demonstrate that the intrinsically high free volume environment of the precursor, coupled with the steric hindrance of thermostable contorted fragments, promotes the formation of loosely packed and ultramicroporous carbon structures within the resultant CMS membrane, thereby enabling efficient CO2 discrimination via size sieving and affinity. The membrane achieves an ultrahigh CO2 permeability, good selectivity, and excellent stability. After one month of long-term operation, the CO2 permeability in the mixed gas is maintained at 11,800 Barrer, with a CO2/N2 selectivity exceeding 60. This study provides insights into the relationship between precursor-chemistry and CMS performance, and our ultrapermeable CMS membrane, which is scalable using thin film manufacturing, holds great potential for industrial CO2 capture.

Carbon Molecular Sieve Membranes from Poly(oxo-biphenylene-isatin) with Increasingly Bulky Fluorine Substitution: Characterization and Gas Transport Properties

Carbon Molecular Sieve Membranes from Poly(oxo-biphenylene-isatin) with Increasingly Bulky Fluorine Substitution: Characterization and Gas Transport Properties

Synergistic effect of carbon molecular sieve and alkali metal nitrate on promoting intermediate-temperature adsorption of CO2 over MgAl-layered double hydroxide

The development of intermediate-temperature adsorbents with high CO2 adsorption capacity is crucial for the tandem integration with CO2 hydrogenation catalyst, aimed at enhancing economy viability and minimizing energy consumption in Carbon capture, utilization and storage (CCUS). Although certain porous carbon materials (PCM) have been employed to enhance CO2 adsorption capability of layered double hydroxide (LDH), there remains an urgent necessity to identify more cost-effective and efficient PCM alternatives. Herein, alkali metal nitrates ((Li0.3Na0.18K0.52)NO3, hereafter referred to as LiNaK) modified layered double hydroxide (LDH)/carbon molecular sieve (CMS) composite (LiNaK-LDH/CMS) as promising adsorbents for CO2 capture was reported. The effects of CMS addition and nitrate loading, the calcination and adsorption temperature, as well as the cycling stability were investigated systematically. The results revealed that the CO2 capture capacity of the LiNaK-modified layered double oxide (LDO)/CMS composite (30 mol%LiNaK-LDO/CMS15%)-incorporating with 15 wt% CMS addition and 30 mol% nitrate loading-achieved a remarkable CO2 adsorption capacity of 1.32 mmol/g at 300 °C due to the synergetic interactions between CMS and nitrate; this represents nearly a sevenfold enhancement compared to initial LDO performance. Moreover, the 30 mol%LiNaK-LDO/CMS15% adsorbent also demonstrated commendable cyclic stability after ten adsorption/desorption cycles, retaining over 85 % of its initial adsorption capacity within half of adsorption time. Based on both obtained adsorption performance and characterization data from the adsorbents, a pre-adsorption enhancing CO2 intermediate-temperature adsorption mechanism over LiNaK-LDH/CMS composite through air calcination processes is proposed. This study significantly advances LDH-based adsorbent for future research into CO2 intermediate-temperature adsorption.

Innovative thermal crosslinked polyimide gas separation membrane with highly selective and resistance to physical aging base on phenyl ethynyl

In this study, a high performance phenyl ethynyl thermal crosslinked 6FDA-based polyimide (CR-4ETA-x) was developed, which has high gas permeability and selectivity, resistance to physical aging. By introducing 4,4′-(Acetylene-1,2-diyl) diphthalic anhydride (4ETA) monomer into the polyimide structure, the thermal crosslinking precursor membrane was formed. The precursor membrane was heat treated at 440℃ to obtain CR-4ETA-x. After heat treatment, we detected the olefin radical in the crosslinked membrane by electron paramagnetic resonance, which proved that the polyimide network was formed. This allows the crosslinked membrane to have greater d-spacing, higher rigidity, and BET surface area. The CO2 permeability of CR-4ETA-5% is 4114 barrer and the CO2/CH4 selectivity is 19.22. Compared to 6FDA-DAM, the CO2 permeability increased by 477% while the selectivity decreased by only 17%. CR-4ETA-20% shows the CO2 permeability of 3560 Barrer and CO2/CH4 selectivity of 21.1 in CO2/CH4 mixed-gas. After 60 days of aging the permeability maintenance of CR-4ETA-20% were 88%, 84%, 83% and 91% for O2, N2, CO2 and CH4. In addition, in the long-term stability test of more than 100 h, the separation performance of CR-4ETA-20% did not decrease significantly. However, CR-4ETA-x also has limitations, such as poor stability in alkaline environments and lower gas permeability than some advanced carbon molecular sieve membranes. In general, the method of phenyl ethynyl thermal crosslinking provides an effective way for the development of CO2 separation membranes with possible applications.

Techno-Economic Analysis of a Carbon Molecular Sieve-Based Xylene Isomer Purification Process.

The separation and purification of xylene isomers is critical to the production of polyethylene terephthalate (PET). These separations are complex to operate and demand tremendous amounts of energy and thus are an opportunity for reducing industrial energy consumption. Membranes provide a low-energy footprint technology with simpler operation, and recently, membrane materials have been developed that are capable of separating xylene isomers. While these materials have demonstrated the ability to separate xylenes, they have yet to be commercially deployed. This work conducts a techno-economic analysis (TEA) to provide insight on the commercial attractiveness of a p-xylene selective carbon molecular sieve (CMS) membrane from both a cost and energy standpoint. This TEA was conducted through the pairing of a Maxwell-Stefan transport framework for rigid microporous materials with process modeling. Single-stage organic solvent reverse osmosis (OSRO) and pervaporation processes were used to evaluate the effects of recovery, selectivity, and diffusivity on the energy intensity and cost of the xylene separation. The final analysis used two systems, a single pervaporation stage followed by two OSRO stages, which was compared against a three-stage OSRO cascade. These were benchmarked against the commercial Parex process. We estimate that the membrane processes have the potential to enable impressive cost savings compared to the Parex process. While both systems outperformed the Parex process in terms of cost, the pervaporation/OSRO hybrid process was able to achieve the lowest cost of all due to its reduced membrane surface area compared to standalone OSRO. These findings demonstrate the potential of membrane systems in the field of difficult small molecule solvent separations.

Carbon molecular sieve gas separation membranes derived from in-situ crosslinked polyimide containing bromine groups

The network polyimide (PI) precursor is a promising candidate to fabricate the advanced carbon molecular sieve (CMS) membrane since its robust crosslinked structure could prevent pore structure collapse during CMS formation. Exploring the relationship between network PI precursor structure and CMS membrane is highly significant. Herein, a novel brominated network PI precursor was fabricated via in-situ cross-linking technique firstly, and then the thermally induced bromination/debromination process was applied to tune the microporosity and gas transport properties of network PI precursor and its derived CMS membranes. After the bromination/debromination and carbonization at 550 °C, the resultant CMS membrane exhibited both high gas permeability and gas selectivities compared to its un-brominated network PI precursor derived CMS membrane. This is due to the bromination/debromination and carbonization enable the CMS membrane possesses large d-spacing values (11.06 Å), high BET surface areas (538.57 m2/g), and high percentage (∼71 %) of ultra-micropores. For instance, 6F-TA/TA-Br-550/30 membrane exhibits great CO2/CH4 separation ability, with a CO2 permeability of 6300 Barrer and a CO2/CH4 selectivity of 46.11, which is suppressed the latest 2019 trade-off curves. We anticipate that the present bromination/debromination and carbonization could provide a fresh perspective on the rational design of network PI precursor and its derived CMS membrane with excellent gas separation performance.

High-performance carbon molecular sieve membrane derived from PEK-N polymer for CO2 separation

Carbon molecular sieve (CMS) membranes demonstrate promising economic and environmental advantages in gas separation applications. In this work, we synthesized a novel polymer precursor of PEK-N and utilized it to fabricate a series of PEK-N derived CMS membranes. With varying carbonization temperature and time, the pore structures and gas separation performance were finely tuned. The gas separation properties of membranes with different carbonization temperature were comprehensively evaluated. In particular, by carbonizing the sample at 650 °C for 1 h, PEK-N derived CMS membranes (CMS-650-1) achieved the highest CO2 permeability around 2176 Barrer, and selectivities of 48.2 for CO2/N2 and 57.8 for CO2/CH4 in their gas mixtures. Our study suggests that the use of rationally designed polymers has the potential to bring about high gas separation performance for polymer-derived carbon molecular sieve membranes.

Synergistic tuning of microstructure and morphology in carbon molecular sieve hollow fibers for propylene/propane separation

Asymmetric carbon molecular sieve (CMS) hollow fiber membranes with tunable micro‐ and macro‐structural morphologies for energy efficient propylene‐propane separation are reported here. A sub‐glass transition temperature (sub‐Tg) thermal oxidative crosslinking strategy enables simultaneous optimization of the intrinsic molecular sieving properties while also reducing the thickness of the CMS “skin” derived from the 6FDA:BPDA/DAM polyimide precursors. Such synergistic tuning of CMS microstructure and macroscopic morphology of CMS hollow fibers enables significantly increased propylene permeance (reaching 186.5 GPU) while maintaining an appealing propylene/propane selectivity of 13.3 for 50/50 propylene/propane mixed gas feeds. Our findings reveal a more refined and versatile tool than available with previous O2‐doping pretreatments. The advanced approach here should be broadly useful to other polyimide precursors and diverse gas pairs.

Synergistic Tuning of Microstructure and Morphology in Carbon Molecular Sieve Hollow Fibers for Propylene/Propane Separation.

Asymmetric carbon molecular sieve (CMS) hollow fiber membranes with tunable micro- and macro-structural morphologies for energy efficient propylene-propane separation are reported here. A sub-glass transition temperature (sub-Tg) thermal oxidative crosslinking strategy enables simultaneous optimization of the intrinsic molecular sieving properties while also reducing the thickness of the CMS "skin" derived from the 6FDA : BPDA/DAM polyimide precursors. Such synergistic tuning of CMS microstructure and macroscopic morphology of CMS hollow fibers enables significantly increased propylene permeance (reaching 186.5 GPU) while maintaining an appealing propylene/propane selectivity of 13.3 for 50/50 propylene/propane mixed gas feeds. Our findings reveal a more refined and versatile tool than available with previous O2-doping pretreatments. The advanced approach here should be broadly useful to other polyimide precursors and diverse gas pairs.

Tailoring the properties of carbon molecular sieves membranes for the separation of propionic acid from aqueous solutions

In the fermentative production of propionic acid (PA), the major problem with batch fermentation systems is the strong inhibitory effect of PA on the production yield; one way to increase the yield is the in-situ removal of PA by using pervaporation. Acetic acid (AA) is the most important by-product in the fermentation; therefore, the membrane should be able to remove selectively PA from an aqueous solution containing AA. Considering that PA is more hydrophobic than AA and their kinetic diameter are 0.480 and 0.436 nm respectively, hydrophobic membranes with main pores in the range of around 0.5–0.6 nm with high permeation are required.Supported thin Carbon Molecular Sieve Membranes (CMSM) were prepared by the dip coating a porous alumina support into a solution containing resorcinol phenolic resin as carbon source. The hydrophobicity was obtained by carbonizing the polymer at temperatures higher than 750 °C and adding polyvinyl butyral (PVB) as pore forming agent and carbon contributor. PA with 88 % of purity was obtained by pervaporation of an aqueous solution containing 5 % of PA and 5 % of AA using a CMSM carbonized at 850 °C containing 1 % of PVB in the dipping solution.

Unveiling the Mystery: How TR precursors lead to exceptional gas separation performance in CMSMs

One of the main issues with membrane-based gas separation lies in the unexplored relationship between the precursors and their derived carbon molecular sieve membranes (CMSMs). Herein, we designed a series of TR polymers with gradient PBO content as precursors to investigate the carbonization mechanisms of PBO structure. The process of transforming the polymer precursor into carbon structure throughout pyrolysis involves utilizing an array of characterization techniques along with pyrolysis simulation. Results indicated that a higher PBO content leads to stronger molecular sieving effect of the resulting CMSM. The TR-CMS-50 membrane demonstrated exceptional gas separation performance with high permeability (PH2 = 3154 and PCO2 = 1495 Barrer) as well as ultra-high H2/CH4 (384) and CO2/CH4 (166) selectivity, which far exceeded the newest Upper bound line, showing significant potential for practical applications. This may can be attributed to “delayed effect” of the PBO structure which requires pyrolysis at higher temperatures, leading to more intense pyrolysis and the release of nitrogen-containing substances. Meanwhile, PBO has a cyclic system with a strong aromatic structure that closely resembles a carbon strand, which probably facilitates aromatization and enables it to more easily integrate into CMS structure, resulting in a more orderly arrangement in the Langmuir phase and generating higher concentration of pyrrolic-N (58.7 % vs. 44.1 %) as well as graphitic-N (31.6 % vs. 17.2 %). Thus, increasing the PBO content makes the derived CMS denser and significantly enhances its molecular sieving capacity. This study offers new insights into the development of precursor structures that creates high-performance CMSMs.

Long-term pure- and mixed-gas performance of carbon molecular sieve membranes derived from a tetraphenylethylene-based ladder polymer of intrinsic microporosity (TPE-PIM) for propylene/propane separation

Continuous long-term evaluation of propylene and propane permeation through narrow slit carbon molecular sieve (CMS) membranes is essential for an in-depth study of their steady-state separation performance. CMS membranes are characterized by finely tuned ultramicroporous structures, exceptional thermal and chemical stability, and hold great promise for the energy-intensive separation of propylene and propane. However, the gradual changes in their performance over time due to penetrant-induced structural chain rearrangements have often been overlooked. In this study, we prepared CMS membranes using a polymer of intrinsic microporosity (PIM) with a highly aromatic tetraphenylethylene (TPE) based building block. The presence of bulky and sterically hindered TPE repeat units renders this polymer an excellent precursor for the fabrication of high-performance CMS membranes. The TPE-PIM-based precursor underwent pyrolysis at temperatures ranging from 550 to 700 °C for 1 h. Pure- and mixed-gas permeation tests were accompanied by various characterization techniques to assess the carbonization state of the CMS materials. The CMS pyrolyzed at 700 °C exhibited a decline in pure-gas C3H6/C3H8 selectivity from an initial value of 300 to 161 at steady state over a 20-day period. Even more notable, under equimolar mixed-gas feed conditions, the isotropic CMS film displayed a substantial C3H6/C3H8 selectivity reduction from 214 to 62 over a 24-day period. This performance decline can be attributed to competitive sorption and very slow dilation kinetics, which led to moderately reduced propylene permeability while significantly enhancing propane permeability. Our study suggests that long-term, continuously performed mixed-gas permeation experiments are essential to assess the ‘steady-state’ performance of CMS membranes for mixtures containing highly sorbing feed components, as observed for propylene/propane separation.

2D Carbonaceous Materials for Molecular Transport and Functional Interfaces: Simulations and Insights.

ConspectusCarbon-based two-dimensional (2D) functional materials exhibit potential across a wide spectrum of applications from chemical separations to catalysis and energy storage and conversion. In this Account, we focus on recent advances in the manipulation of 2D carbonaceous materials and their composites through computational design and simulations to address how the precise control over material structure at the atomic level correlates with enhanced functional properties such as gas permeation, selectivity, membrane transport, and charge storage. We highlight several key concepts in the computational design and tuning of 2D structures, such as controlled stacking, ion gating, interlayer pillaring, and heterostructure charge transfer.The process of creating and adjusting pores within graphene sheets is vital for effective molecular separation. Simulations show the power of controlling the offset distance between layers of porous graphene in precisely regulating the pore size to enhance gas separation and entropic selectivity. This strategy of controlled stacking extends beyond graphene to include covalent organic frameworks (COFs) such as covalent triazine frameworks (CTFs). Experimental assembly of the layers has been achieved through electrostatic interactions, thermal transformation, and control of side chain interactions.Graphene can interface with ionic liquids in various forms to enhance its functionality. A computational proof-of-concept showcases an ion-gating concept in which the interaction of anions with the pores in graphene allows the anions to dynamically gate the pores for selective gas transport. Realization of the concept has been achieved in both porous graphene and carbon molecular sieve membranes. Ionic liquids can also intercalate between graphene layers to form interlayer pillaring structures, opening the slit space. Grand canonical Monte Carlo simulations show that these structures can be used for efficient gas capture and separation. Experiments have demonstrated that the interlayer space can be tuned by the density of the pillars and that, when fully filled with ionic liquids and forming a confined interface structure, the graphene oxide membrane achieves much higher selectivity for gas separations. Moreover, graphene can interface with other 2D materials to form heterostructures where interfacial charge transfers take place and impact the function. Both ion transport and charge storage are influenced by both the local electric field and chemical interactions.Fullerene can be used as a building block and covalently linked together to construct a new type of 2D carbon material beyond a one-atom-thin layer that also has long-range-ordered subnanometer pores. The interstitial sites among fullerenes form funnel-shaped pores of 2.0-3.3 Å depending on the crystalline phase. The quasi-tetragonal phases are shown by molecular dynamics simulations to be efficient for H2 separation. In addition, defects such as fullerene vacancies can be introduced to create larger pores for the separation of organic solvents.In conclusion, the key to imputing functions to 2D carbonaceous materials is to create new interactions and interfaces and to go beyond a single-atom layer. First-principles and molecular simulations can further guide the discovery of new 2D carbonaceous materials and interfaces and provide atomistic insights into their functions.

Porous organic cage induced high CO2/CH4 separation efficiency of carbon molecular sieve membranes

Porous fillers have been incorporated into precursor membranes to fabricate carbon molecular sieve (CMS) membranes, where the interfacial compatibility between fillers and matrix significantly influences the separation performance of converted CMS membranes. To address this issue, we introduce molecular fillers of porous organic cages (POCs) into precursor membranes, the organic composition and discrete molecular characteristics of which can enhance the compatibility with the polymer matrix (PIM-1), bringing enhanced porosity and narrowed pore size distribution, especially in the ultra-micropore region, to the CMS membranes. The obtained CMS membrane shows simultaneously improved gas permeability and selectivity wherein the optimized CMS membrane pyrolyzed at 600 °C with 10 wt% POCs loading (CMS-10%-600) exhibits a CO2 permeability of 2002 Barrer and a CO2/CH4 selectivity of 221.6, surpassing the 2019 CO2/CH4 upper bound and superior to most of reported CMS membranes. Due to the incorporation of POC, the CMS-10%-600 membrane demonstrates a 147.5 % increase in CO2 permeability and a 297.1 % increase in CO2/CH4 selectivity compared to pristine PIM-1-based CMS membrane, along with the excellent aging resistance for over 30 days. This study provides new insights into the design of high-performance CMS membranes for gas separation.

High-Performance Carbon Molecular Sieve Membranes Derived from a PPA-Cross-linked Polyimide Precursor for Gas Separation.

Carbon molecular sieve (CMS) membranes have emerged as attractive gas membranes due to their tunable pore structure and consequently high gas separation performances. In particular, polyimides (PIs) have been considered as promising CMS precursors because of their tunable structure, superior gas separation performance, and excellent thermal and mechanical strength. In the present work, polyphosphoric acid (PPA) was employed as both cross-linker and porogen, it created pores within the PI polymeric matrix, while it also effectively acting as a cross-linker to regulate the ultramicropores of the CMS membranes, thus simultaneously improving both permeability and selectivity of the CMS membranes. By employing PI/PPA hybrid with PPA content of 5 wt % as a precursor, the obtained CMS membrane exhibited a CO2 and He permeability of 1378.3 Barrer and 1431.4 Barrer, respectively, which was an approximately 10-fold increase compared to the precursor membrane. Under optimized conditions, the CO2/CH4 and He/CH4 selectivity of the obtained CMS membrane reached 81.5 and 89.9, respectively, which was 278% and 307% higher than that of the pristine PI membrane. In addition, the membrane exhibited good long-term stability during a one-week continuous test. This study clearly denoted PPA can be used for precisely tailoring the ultramicroporosity of CMS membranes.

Huge improved gas separation performance of carbon molecular sieve membrane by forming a double crosslinked polyimide precursor

A vital issue in searching for advanced gas separation membranes is understanding the precursor structure-gas separation properties of carbon molecular sieve (CMS) membranes. Here, we reported two crosslinked polyimides and used as CMS precursors, in which, the DCPI-4 is a double cross-linkable polyimide with 4 % triptycene triamine as a crosslinker (Type I) and COOH group that can be crosslinked at 350 °C by decarboxylation (Type II), whereas the DCPI-0 with COOH (Type II). After pyrolysis at 550 °C, the DCPI-4-CMS showed a higher SBET (812 vs 713 m2g-1), larger ultra-microporosity ratio (26.6 % vs 17.8 %), larger d-spacing (4.08 vs 3.94 Å), less graphitization (sp3/sp2 of 0.156 vs 0.118), 5.5 times higher CO2 permeability (7573 vs 1391 Barrer) and same CO2/CH4 selectivity (∼62) than DCPI-0-CMS. We consider this is due to the type I crosslinking enhances the rigidity of the polyimide backbone, and inhibits the collapse of micropores during the carbonization, which causes improved ultra-microporosity and ultra-micropore ratio that both enhances the gas diffusion and solubility coefficient as well activation energy difference of gas pairs. Conclusively, this double crosslinking method provides a good perspective for achieving CMS membranes with excellent gas separation performance.

Controlled organic solvent transport in ultramicroporous carbon membranes

The drive to decarbonize chemical processes necessitates exploring low-energy solutions for separating complex liquid mixtures ubiquitous in food, pharmaceuticals, petrochemical, and synthetic fuel production industries. This report comprehensively investigates conceptualizing and implementing two novel organic solvent separation processes: Organic Solvent Forward Osmosis (OSFO) and Organic Solvent Pressure Assisted Osmosis (OSPAO). The intrinsic molecular specificity of ultramicroporous carbon molecular sieve (CMS) membranes allowed the unprecedented separation of a complex mixture of short-chain alcohols (e.g., methyl alcohol, ethyl alcohol, and isopropyl alcohol) at room temperature. A new hybridized membrane-based separation methodology, OSPAO, that combines the elements of organic solvent nanofiltration (OSN) and OSFO is introduced. CMS-based OSPAO demonstrated a marked enhancement in the flux of organic species permeate, considerably improving separation efficiencies. The separation modalities presented in this report underscore the essential role of osmosis in the differentiation of organic solvents, thereby contributing valuable insights to osmosis-based separation technologies.

Hydrogen purification to fuel cell quality using pressure swing adsorption for CO2 separation over activated carbon molecular sieve: Experimental and dynamic modelling evaluation under non-isothermal condition

Hydrogen purification is a crucial step in producing high-quality fuel cell-grade hydrogen. This study evaluates the efficacy of activated carbon molecular sieve (CMS) as an adsorbent for CO2 removal from hydrogen streams using pressure swing adsorption (PSA) under non-isothermal conditions. A dynamic model was developed to investigate the effects of bed temperature, solid bulk density, and hydrogen feed concentration on hydrogen purity. To verify the model's accuracy, comparison between the simulated results and experimental data was made under similar operating conditions. By employing a central composite design, the interaction effects of the investigated parameters on the PSA system were also studied. The results show that the observed H2 purity of 99.5% and recovery of 58.82% were obtained. By optimizing the parameters to a bed temperature of 300K, solid bulk density of 720 kg/m3, and hydrogen concentration of 88%, improved hydrogen purity of 99.99% was obtained.