Gas Pairs Research Articles

Synthesis, characterization and properties of polyimides with spirobisbenzoxazole scaffold structure

Novel diamines containing spirobisbenzoxazole scaffold structure were successfully synthesized. These diamines were homopolymerized with commercial 4,4’-(hexafluoroisopropylidene)diphthalic anhydride (6FDA) and cyclohexanedianhydride (H'PMDA) to prepare a series of benzoxazole based polyimides (PBOIs). The obtained PBOIs exhibited good organic solubility and outstanding thermal properties, including glass transition temperature ( T g ) of 355–400 °C and 5% thermal decomposition temperatures ( T d5% ) of 474–490 °C. Meanwhile, these polymer films exhibited excellent mechanical strength, such as tensile strength of 79.4–92.1 MPa and elongation at break of 19.5%∼31.2%. In addition, such PBOIs have been proved to be novel microporous polymer with pore width distribution of 5–7 Å and BET surface area of 281–378 m 2 /g. The permeability-selectivity relationship of H'PMDA based PBOIs was close to the 2008 Robeson upper bound for CO 2 /CH 4 and O 2 /N 2 gas pairs, showing promise in the field of gas separation. • Spirobibenzoxazole scaffold based Polyimides. • Good solubility and microporosity. • The permeability-selectivity relationship of H'PMDA based polyimides for CO 2 /CH 4 and O 2 /N 2 gas pairs close to the 2008 Robeson upper bound.

Synthesis and Visualization of Entangled 3D Covalent Organic Frameworks with High-Valency Stereoscopic Molecular Nodes for Gas Separation.

The structural diversity of three-dimensional (3D) covalent organic frameworks (COFs) are limited as there are only a few choices of building units with multiple symmetrically distributed connection sites. To date, 4 and 6-connected stereoscopic nodes with Td , D3h , D3d and C3 symmetries have been mostly reported, delivering limited 3D topologies. We propose an efficient approach to expand the 3D COF repertoire by introducing a high-valency quadrangular prism (D4h ) stereoscopic node with a connectivity of eight, based on which two isoreticular 3D imine-linked COFs can be created. Low-dose electron microscopy allows the direct visualization of their 2-fold interpenetrated bcu networks. These 3D COFs are endowed with unique pore architectures and strong molecular binding sites, and exhibit excellent performance in separating C2 H2 /CO2 and C2 H2 /CH4 gas pairs. The introduction of high-valency stereoscopic nodes would lead to an outburst of new topologies for 3D COFs.

Synthesis and Visualization of Entangled 3D Covalent Organic Frameworks with High‐Valency Stereoscopic Molecular Nodes for Gas Separation

AbstractThe structural diversity of three‐dimensional (3D) covalent organic frameworks (COFs) are limited as there are only a few choices of building units with multiple symmetrically distributed connection sites. To date, 4 and 6‐connected stereoscopic nodes with Td, D3h, D3d and C3 symmetries have been mostly reported, delivering limited 3D topologies. We propose an efficient approach to expand the 3D COF repertoire by introducing a high‐valency quadrangular prism (D4h) stereoscopic node with a connectivity of eight, based on which two isoreticular 3D imine‐linked COFs can be created. Low‐dose electron microscopy allows the direct visualization of their 2‐fold interpenetrated bcu networks. These 3D COFs are endowed with unique pore architectures and strong molecular binding sites, and exhibit excellent performance in separating C2H2/CO2 and C2H2/CH4 gas pairs. The introduction of high‐valency stereoscopic nodes would lead to an outburst of new topologies for 3D COFs.

Functionalized two-dimensional g-C3N4 nanosheets in PIM-1 mixed matrix membranes for gas separation

The virtuous of two-dimensional (2D) nanomaterials in high aspect ratio and tunable surface functionality have geared towards their implementation in mixed matrix membranes (MMMs) for advanced gas separation. In this study, the effects of functionalized 2D nanosheets in the MMMs for gas separation were investigated. The graphitic carbon nitride (g-C3N4) nanosheets were modified with various functional groups namely sulfuric acid group, aliphatic amino group, aromatic amino group, and sulfonic group via four different synthesis approaches. Polymers of intrinsic microporosity (PIMs, e.g., PIM-1) was selected as the continuous polymer phase due to its intrinsic high permeability and comparable selectivity towards different gas pair. The sulfonic acid functionalized g-C3N4 MMMs (e.g., PIM-1/g-C3N4-D) imparted high separation properties ascribed to the great CO2 affinity induced by the sulfonic acid groups. In particular, PIM-1/g-C3N4-D (99:1) MMM demonstrated promising CO2 separation performance, with CO2 permeability of 3740 Barrer and CO2/N2 selectivity of 19.8. Moreover, at 5 wt% loading of g-C3N4-D, the H2/N2 and O2/N2 separation of the MMMs had exceeded the 2008 Robeson upper bound, thanks to the periodic triangular ultramicropores in g-C3N4 that favor precise sieving of small gases. These results pave the way in using the developed membranes in practical H2 purification, air separation and CO2 capture.

Mixed Matrix Membranes Loaded with a Porous Organic Polymer Having Bipyridine Moieties.

Mixed matrix membranes (MMMs), derived from three aromatic polyimides (PIs), and an affordable porous organic polymer (POP) having basic bipyridine moieties were prepared. Matrimid and two fluorinated polyimides, which were derived from 4,4′-(hexafluoroisopropylidene)diphthalic anhydride and 2,2′-bis(4-aminophenyl)hexafluoropropane (6F6F) or 2,4,6-trimethyl-m-phenylenediamine (6FTMPD), were employed as polymer matrixes. The used POP was a highly microporous material (surface area of 805 m2 g−1) with excellent thermal and chemical stability. The MMMs showed good compatibility between the PIs and POP, high thermal stabilities and glass transition temperatures superior to those of the neat PI membranes, and good mechanical properties. The addition of POP to the matrix led to an increase in the gas diffusivity and, thus, in permeability, which was associated with an increase in the fractional free volume of MMMs. The increase in permeability was higher for the less permeable matrix. For example, at 30 wt.% of POP, the permeability to CO2 and CH4 of the MMMs increased by 4- and 7-fold for Matrimid and 3- and 4-fold for 6FTMPD. The highest CH4 permeability led to a decrease in CO2/CH4 selectivity. The CO2/N2 separation performance was interesting, as the selectivity remained practically constant. Finally, the POP showed no molecular sieving effect towards the C2H4/C2H6 and C3H6/C3H8 gas pairs, but the permeability increased by about 4-fold and the selectivity was close to that of the matrix. In addition, because the POP can form metal ion bipyridine complexes, modified POP-based MMMs could be employed for olefin/paraffin separations.

Interfacial design of polysulfone/Cu-BTC membrane using [Bmim][Tf2N] and [Dmim][Cl] RTILs for CO2 separation: Performance assessment for single and mixed gas separation

An upsurge in searching membranes with improved perm-selectivity and long-term stability is crucial in membrane-based gas separation. Herein, we engineered the interfacial characteristics of Cu-BTC MOFs with the polysulfone (PSf) matrix using ionic liquids (ILs) at the polymer-filler interface. Two different ILs, [Bmim][Tf2N] and [Dmim][Cl], were used to prepare composite PSf/Cu-BTC/[Bmim][Tf2N] and PSf/Cu-BTC/[Dmim][Cl] membranes. The membranes micro and chemical structures were characterized using XRD, FESEM, and XPS techniques. Results indicated that the multifunctional properties of ILs and Cu-BTC particles influenced the membrane formation mechanism. The uniform dispersion of Cu-BTC filler particles with the inclusion of [Bmim][Tf2N] and [Dmim][Cl] ILs on the membrane surface was evident from the morphological studies. The absence of a leaky interface by the ILs integration in the PSf/Cu-BTC/[Bmim][Tf2N] and PSf/Cu-BTC/[Dmim][Cl] membranes results in a pronounced increase in selectivities. For instance, PSf/Cu-BTC/[Dmim][Cl] membranes, the CO2 permeance was noticed to be 29.35 ± 0.35 GPU, and their corresponding gas pair selectivities were noted to be significantly higher than the neat and PSf/Cu-BTC membranes. Similarly, in PSf/Cu-BTC/[Bmim][Tf2N] membrane exhibited optimum CO2 permeance of 30.44 ± 0.49 GPU with the CO2/N2 and CO2/CH4 selectivities of 61 and 59.70%, respectively, higher than neat PSf membrane. Furthermore, these membranes showed better anti-aging resistance and long-term stability than the neat PSf membranes. The merits of a simultaneous increase in permeance and selectivities and the good stability and scalable properties make the proposed PSf/Cu-BTC/IL membranes of great interest for the industrial CO2 separation from the gas exhausts.

Stimuli-responsive of magnetic metal-organic frameworks (MMOF): Synthesis, dispersion control, and its tunability into polymer matrix under the augmented-magnetic field for H2 separation and CO2 capturing applications

Single-crystal magnetic-responsive core-shell MOF by grafting Fe3O4 nanoparticles onto the UiO-66-NH2 and their controlled embedding into gas separation mixed matrix membranes was reported. Obtained results confirmed the stimuli-responsive character of the MMOF during their dispersion of MMOF in a well-defined arrays structure in the PMMA matrix. Contrarily, an absence of a magnetic field results in the MMOF aggregation and sedimentation of the particles at the bottom of the membrane. Compared to the non-controlled ones, gas permeability increased by 26.2% for CO2 and 76.67% for H2, and selectivity increased 2.95 and 1.49 times for the CO2/N2 and H2/CO2 gas pairs, respectively. Moreover, obtained permeability-selectivity values for the H2/CO2 gas pairs overcome the appropriate modified 2008 Robeson upper bound.

ZIF-67 membranes supported on porous ZnO hollow fibers for hydrogen separation from gas mixtures

Co-based zeolitic imidazolate framework-67 (ZIF) membranes present impressive potential to be applied for efficient gas separation. However, the synthesis of ZIF-67 membrane is challenging because ZIF-67 crystals tend to nucleate and grow in the reaction solution rather than on the substrate surface. In this work, ZIF-67 membranes were developed on porous ZnO hollow fibers via in situ solvothermal growth method. The effects of different ZnO supports, surface activation, growth duration, and growing temperatures on the resultant membrane performance were carefully investigated. The optimized ZIF-67 composite hollow fiber membrane displayed desirable permeation performance, ideal selectivities for single gas, and separation factors for gas mixtures. The achieved H2 permeance was 8.98 × 10−8 mol m−2 s−1·Pa−1and ideal selectivities for H2 gas pairs with CO2, N2, and CH4 were 5.14, 11.75, and 15.89, respectively, which compared favorably with other reports in the literature. The developed ZIF-67 membrane exhibited good stability in terms of gas permeances between 30 and 200 °C. Furthermore, the membrane showed almost constant H2 permeance and H2/CH4 separation factor during the 50-h run at 150 °C, demonstrating the excellent thermal stability of membrane. The fabrication of the excellent ZIF-67 membrane can be achieved just in one cycle of growth with high reproducibility.

Hydrocarbon ladder polymers with ultrahigh permselectivity for membrane gas separations.

Membranes have the potential to substantially reduce energy consumption of industrial chemical separations, but their implementation has been limited owing to a performance upper bound-the trade-off between permeability and selectivity. Although recent developments of highly permeable polymer membranes have advanced the upper bounds for various gas pairs, these polymers typically exhibit limited selectivity. We report a class of hydrocarbon ladder polymers that can achieve both high selectivity and high permeability in membrane separations for many industrially relevant gas mixtures. Additionally, their corresponding films exhibit desirable mechanical and thermal properties. Tuning of the ladder polymer backbone configuration was found to have a profound effect on separation performance and aging behavior.

Effect of heat diffusivity for driving chain stitching of dual-type hybrid organosilica-derived membranes

In this study, the usage of dual hybrid organosilica is proposed for discussing the influence of thermal-driven chain stitching on the organosilica membrane structure for the first time. The influence of the gas thermal diffusivity on the hybrid organosilica membrane for separating H2 from CH4, C2H6, and C3H8, is discussed in detail. The characterization and permeation tests revealed that the optimal condition of the organosilica membrane fabrication is the usage of nitrogen as calcination atmosphere owing to the mild reaction. In addition, it is found that when N2 is used as the calcining gas and calcination is performed at a lower temperature, it is beneficial for the separation of small-molecule gases. However, calcination at higher temperatures is beneficial to the separation of gas pairs with a big difference in kinetic diameter. The as-prepared M−N2−300 exhibited the maximum selectivity of 37.32 for CO2/N2, 82.37 for CO2/CH4, 47.51 for H2/N4, and 109.28 for H2/CH4, and ideal H2 permeance of 2.24 × 10−8 mol/(m2sPa). Moreover, the as-prepared M−N2−500 exhibited the maximum selectivity for the following gases: 438.99 and 301.47 toward H2/C2H6 and H2/C3H8, respectively, at the ambient environment, and satisfactory H2 permeance of 5.14 × 10−8 mol/(m2sPa). This shows the potential and industrial relevance for gas-separation concerning applications like H2 energy production and olefins/paraffins recovery.

Confined facilitated transport within covalent organic frameworks for propylene/propane membrane separation

Energy-efficient membrane technology is sought to replace or integrate with conventional energy- and cost-intensive distillation for precise propylene/propane separation. Covalent organic framework (COF)-based composite membranes (CMs) are promising candidates for the representative difficult propylene/propane separation system. However, the large-size pore of COFs cannot achieve an effective separation of gas pairs with sub-angstrom (0.2 Å) size differences. Here, we design confined facilitated transport nanochannels within COFs as productive fillers to construct CMs. The anchored high-density Ag+ carriers facilitate C3H6 monomolecular high-speed transport along the nanochannel surface. Under this confined transport mechanism, the problem of over-sized COF pores can be partially circumvented, and high selectivity obtained. Moreover, the obtained asymmetric configuration of SCOF-Ag/PI CMs results in directional gas transport. As the first work of COF-based membranes for olefin/paraffin separation, SCOF-Ag/PI CMs demonstrate a high propylene permeability of 75.16 barrer and good propylene/propane selectivity of 35.45, out-performing most of the polymer-based membranes and approaching the performance of ZIF-8 membranes. Furthermore, SCOF-Ag/PI CMs exhibit over one-month durability. The excellent separation performance combined with operating stability provides a promising alternative approach toward efficient C3H6/C3H8 separation.

Tröger’s Base Polyimide Hybrid Membranes by Incorporating UiO-66-NH2 Nanoparticles for Gas Separation

Hybrid membranes based on the Tröger’s base polyimide (PI-TB) as a rigid microporous polymer matrix containing a kinked N-heterocycle and a kind of CO2-philic porous UiO-66-NH2 nano-filler were successfully fabricated for gas separation. This new hybrid membrane exhibits good interfacial compatibility through hydrogen bonds and charge transfer interactions between the PI-TB matrix and the UiO-66-NH2 nano-filler, thus enabling a relatively high loading and well dispersion of nano-filler. Meanwhile, the as-synthesized UiO-66-NH2 nanoparticles increase the average inter-chain spacing distance of PI-TB by interfering with the packing of polymer chains and thus providing additional transport pathways in the membranes. The pure gas permeabilities and ideal selectivities for CO2/CH4, CO2/N2, and O2/N2 systems were investigated at 35 °C and a feed pressure of 1 bar. Among them, the hybrid membrane containing 30 wt % UiO-66-NH2 exhibits the optimal gas separation performance with enhanced permeabilities of CO2 and O2 increased by ∼166% (415 and 92.3 Barrer, respectively) while maintaining comparable CO2/CH4, CO2/N2, and O2/N2 gas pair selectivities (25.0, 18.9, and 4.2, respectively) with the pristine PI-TB membrane. This work enriched the studies on the post-modification of PI-TB as a potential candidate membrane material for gas separation.

Unlocking the limits of diffusion and adsorption of metal-crosslinked reduced graphene oxide membranes for gas separation

Reduced graphene oxide (rGO) membranes have shown promising separation and purification in the fields of water treatment and gas capture due to their unique physicochemical characteristics. However, how to further reduce the transport resistance of rGO membranes and improve separation performance is still a thorny issue. In this work, the reported metal-crosslinked rGO membranes showed a reverse-selective separation behaviors for the adsorbed gas molecules at low pressure. The effect of metal ions on the membrane structure and the separation performance were investigated. Metal ions not only can improve the cross-linking structure and control interlamellar spacing of rGO membranes for the precise molecular sieve, but also can provide abundant metal sites to enhance the affinity, which led to a diffusion-controlled process for the targeted gas molecules. The resulting metal-crosslinked rGO membranes presented outstanding gas permeance and selectivity for gas pairs of the He/CO2, N2/CO2 and Kr/Xe, with the highest selectivity of 21, 11.4 and 4.1, respectively. The work will provide a new avenue towards specific molecule capture for the development of rGO membranes in the fields of natural gas purification and radioactive gas recovery.

Carbon nanotube supported oriented metal organic framework membrane for effective ethylene/ethane separation.

Zeolitic imidazolate framework 8 (ZIF-8) is effective for C3H6/C3H8 separation because of the “sieving effect” of a six-membered (6-M) window. Here, we demonstrate that ZIF-8 is a versatile material that could effectively separate C2H4 from C2H6 via its 4-M window along the <100> direction. We established a facile and environmentally friendly carbon nanotube (CNT)–induced oriented membrane (CNT-OM) approach to fabricate a {100}-oriented ZIF-8 membrane (100-M). In this approach, 2-methyimidazole was anchored onto the CNT surface followed by 3-hour in situ growth in aqueous solution at room temperature. The obtained 100-M, whose 4-M window is aligned along the transport pathway, showed ~3 times higher C2H4/C2H6 selectivity than a randomly oriented membrane. Thus, this work demonstrates that the membrane orientation plays an important role in tuning selectivity toward different gas pairs. Furthermore, 100-M exhibited excellent mechanical stability that could sustain the separation performance after bending at a curvature of ~109 m−1.

Carbon molecular sieve hollow fiber composite membrane derived from PMDA-ODA polyimide for gas separation

Carbon molecular sieve (CMS) membranes have excellent gas separation property over conventional polymeric membranes and superior anti-swelling property. PMDA-ODA polyimide has high thermal stability and good mechanical property. It has been extensively adopted as the precursor of CMS membrane. However, due to the insoluble nature, PMDA-ODA CMS membranes are limited to configurations like dense symmetric films or composite membranes using porous inorganic or metal substrates. In this work, CMS hollow fiber composite membranes based on an asymmetric PMDA-ODA hollow fiber were successfully prepared for the first time. The neat PMDA-ODA hollow fiber membrane was crosslinked by polyethyleneimine to alleviate pore collapsing during carbonization and then dip-coated by a PMDA-ODA PAA solution to seal the surface defects. The PDMA-ODA CMS composite hollow fiber membranes showed gas permeances of 93.4 GPU, 19.6 GPU, 6.5 GPU, and 4.7 GPU for CO2, O2, N2, and CH4, respectively, with an ideal selectivity of 14.4, 3.0, and 19.8 for CO2/N2, O2/N2, and CO2/CH4 gas pairs, respectively. The attractive gas separation property shows a great potential for industrial application.

Small-Pore Zeolite Membranes: A Review of Gas Separation Applications and Membrane Preparation

There have been significant advancements in small-pore zeolite membranes in recent years. With pore size closely related to many energy- or environment-related gas molecules, small-pore zeolite membranes have demonstrated great potential for the separation of some interested gas pairs, such as CO2/CH4, CO2/N2 and N2/CH4. Small-pore zeolite membranes share some characteristics but also have distinctive differences depending on their framework, structure and zeolite chemistry. Through this mini review, the separation performance of different types of zeolite membranes with respect to interested gas pairs will be compared. We aim to give readers an idea of membrane separation status. A few representative synthesis conditions are arbitrarily chosen and summarized, along with the corresponding separation performance. This review can be used as a quick reference with respect to the influence of synthesis conditions on membrane quality. At the end, some general findings and perspectives will be discussed.

Gas sorption and diffusion in perfluoro(butenyl vinyl ether) based perfluoropolymeric membranes

Amorphous glassy perfluoropolymers are characterized by high fractional free volume and hydrocarbon phobicity which means that they perform at the upper bound for several gas pairs. In this study, the sorption of a range of pure gases in Cytop® and a CyclAFlorTM random copolymer of perfluoro(butenyl vinyl ether) (PBVE) and perfluoro(2,2-dimethyl-1,3-dioxole) (PDD) are studied for the first time at different temperatures. The Non-Equilibrium Lattice Fluid (NELF) model is used to model the sorption isotherms in Cytop®, after the determination of the Sanchez-Lacombe model parameters from literature data of the polymer volumetric behavior. The Dual Mode Sorption model is used to model the sorption isotherms in Poly(50%PBVE-co-50%PDD). These results and previously published permeability data are then used within a transport model to determine the diffusivity and activation energy of diffusion for a range of gases within these polymers. The CyclAFlor™ copolymer is shown to have a higher CO2 diffusivity than Cytop®, while maintaining comparable CO2/CH4 diffusivity selectivity. Molecular Dynamics (MD) simulations are performed as a comparison, to calculate the Fickian diffusion coefficients at 35 °C. The diffusion coefficients obtained from MD are consistent with those calculated by the transport model for He and H2 but deviate for larger penetrants (i.e. CO2 and CH4). The results confirm the superior performance of the CyclAFlor™ copolymer for gas separation applications, with greater CO2 solubility and diffusivity than comparable polymers.

Fabrication of analogous mixed matrix membranes via partially in-situ generation of rigid porous moieties without interfacial defects

Herein, a kind of a nalogous m ixed m atrix m embrane (AMMM) was constructed via partially in-situ generation of thermally rearranged polybenzimidazole (TR-PBI) moiety within the network PI matrix that contains ortho -amino group adjacent to imide ring. The role of highly rigid and permeable TR-PBI moieties was very similar to that of the porous fillers in traditional MMMs. By using this strategy, the issues of interfacial incompatibility and filler agglomeration were readily circumvented since the rigid porous fillers are, in fact, the rigid porous moieties that are totally belonged to the part of polymeric matrix itself. After the partially TR conversion, the average microporous diameter within membranes was increased according to the results of N 2 adsorption isotherms and positron annihilation lifetime spectroscopy (PALS) analyses. Gas transport tests revealed that the prepared PBI-PI AMMM exhibited a ∼28.2-fold increasing of in CO 2 permeability (up to 4234.9 Barrer), ∼25.8-fold increasing in O 2 permeability (up to 794 Barrer), and ∼36-fold increasing in N 2 permeability (up to 203.6 Barrer) relative to those of its network PI precursor, along with the decent selectivity of 3.9 for O 2 /N 2 and 20.8 for CO 2 /N 2 . As a result, the comprehensive gas transport properties of PBI-PI AMMM for gas pairs of O 2 /N 2 and CO 2 /N 2 exceeded or approached the 2008 Robeson upper bounds. We hope this proof-of-concept study can open a new avenue to design the advanced AMMMs, especially without the issues of interfacial incompatibility and filler agglomeration. • A novel spirobifluorene pentamine was designed using to form the nascent network PI matrix. • AMMM was constructed via partially in-situ generation of TR-polybenzimidazole moiety. • Mean microporous diameter within AMMM was increased based on the BET and PALS analyses. • Exceptional permeability enhancement in AMMM was observed via partially TR conversion.

Tunning CO2 Separation Performance of Ionic Liquids through Asymmetric Anions.

This work aims to explore the gas permeation performance of two newly-designed ionic liquids, [C2mim][CF3BF3] and [C2mim][CF3SO2C(CN)2], in supported ionic liquid membranes (SILM) configuration, as another effort to provide an overall insight on the gas permeation performance of functionalized-ionic liquids with the [C2mim]+ cation. [C2mim][CF3BF3] and [C2mim][CF3SO2C(CN)2] single gas separation performance towards CO2, N2, and CH4 at T = 293 K and T = 308 K were measured using the time-lag method. Assessing the CO2 permeation results, [C2mim][CF3BF3] showed an undermined value of 710 Barrer at 293.15 K and 1 bar of feed pressure when compared to [C2mim][BF4], whereas for the [C2mim][CF3SO2C(CN)2] IL an unexpected CO2 permeability of 1095 Barrer was attained at the same experimental conditions, overcoming the results for the remaining ILs used for comparison. The prepared membranes exhibited diverse permselectivities, varying from 16.9 to 22.2 for CO2/CH4 and 37.0 to 44.4 for CO2/N2 gas pairs. The thermophysical properties of the [C2mim][CF3BF3] and [C2mim][CF3SO2C(CN)2] ILs were also determined in the range of T = 293.15 K up to T = 353.15 K at atmospheric pressure and compared with those for other ILs with the same cation and anion’s with similar chemical moieties.

Hydrodynamics of Similar Gases in Vortex Mixers: Effect of Physical Properties on the Onset of Instability

The effect of physical properties of gases on the flow hydrodynamics and on the onset of instability was studied to acquire information on how to design fast mixers specific for relevant operations where complete and improved gas mixing is important. To assess the effect of physical properties on the gas flow dynamics in vortex mixers, three gases hydrogen, nitrogen, and argon were chosen because of the viscosity and density differences they provide. Using flow visualization and PIV flow-field characterization techniques, critical Reynolds numbers of flow regime changes were identified from segregated to engulfment flow regimes for three pairs of gases. It was shown that the first critical point of the flow, where the gases have a full rotation in the chamber, depends on the inertial force in terms of dynamic pressure. While hydrogen having the highest kinematic viscosity had a full rotation at Re = 40, nitrogen and argon gases had their full rotation at Re = 70. After these points, a steady rotational flow as a consequence of the balance between the centrifugal and centripetal forces was observed. Similarly, the onset of the engulfment regime was observed earlier for hydrogen, at Re = 150, while it was at Re = 200 for nitrogen and Re = 220 for argon. The present study shows that the gas properties are effective parameters not only on the critical points but also on the shape of the swirling flow pattern formed in the mixer.