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Oriented AlPO-18 membranes with super high CO2 permeance were prepared for the first time by single secondary hydrothermal synthesis using directly synthesized nanosheet seeds. The membranes were grown on the inner surface of tubular asymmetric alumina supports. The morphology of membrane crystals and the membrane quality were highly affected by synthesis temperature and the amount of the structure directing agent in the membrane gel. The optimized AlPO-18 membranes had a ∼3 μm (110)-oriented top AlPO-18 layer upon a ∼1 μm (002)-oriented one. Both channels in the (110) and (002) directions of AlPO-18 zeolite provide fast transport channels, and thus the (110) & (002)-oriented AlPO-18 membranes showed the highest separation index [=CO2 permeance × (selectivity − 1) × permeate pressure] for CO2/CH4 separation among those reported in the literature. Single-gas permeances for H2, CO2, N2 and CH4 with different temperature and pressure drop were measured. The effects of temperature and pressure drop on the separation performance of the oriented membrane were also studied. The best membrane showed CO2 permeance as high as 3.6 × 10−6 mol (m2 s Pa)−1 (∼10 500 GPU) with a CO2/CH4 selectivity of 91.5 for an equimolar CO2/CH4 mixture at 0.2 MPa pressure drop and room temperature. [ABSTRACT FROM AUTHOR]

Given that hydrogen production often involves impurities such as CO 2 , CH 4 , H 2 O, and alkanes, hydrogen purification is crucial for global green energy applications. Mixed matrix membranes (MMMs) using metal-organic framework (MOF) materials offer a non-thermal, energy-efficient method for hydrogen purification. These membranes have controllable structures and promote environmental sustainability. However, challenges such as filler aggregation and matrix-filler incompatibility during the preparation of MOF-MMMs are difficult to avoid and can adversely affect separation performance. In this study, 4-(trifluoromethyl) benzoic acid (4-TFMBA) was introduced in situ to grow synchronously with polyvinyl pyrrolidone (PVP) on UiO-66-NH 2 , forming a hydrophobic bifunctional nanoparticle composite, PVP-Zr-MOF-F. Furthermore, in situ loading of PVP-Zr-MOF-F onto a PVDF polymer matrix was achieved using a wet method and the NIPS technique to prepare PVP-Zr-MOF-F@PVDF. The introduction of 4-TFMBA, with highly electronegative F atoms, enhances hydrophobicity and increases H 2 affinity through polarization and hydrogen bonding induced by C–F bonds. PVP promotes the formation of smaller Zr-MOF particles, increases the proportion of small pores, prevents aggregation, and acts as a pore-forming agent, facilitating the in situ loading and dispersion of PVP-Zr-MOF-F within PVDF chains. This bifunctionalization not only improves the compatibility and dispersion of the nanofillers but also increases the number of small pores, enhancing van der Waals forces and confinement effects on H 2 molecules, making it suitable for gas separation under humid conditions. The results indicate that the H 2 permeance of PVP2–Zr-MOF-F@PVDF can reach 114,735 GPU, with selectivities of 19, 21, 24, and 120 for H 2 /CO 2 , H 2 /CH 4 , H 2 /C 2 H 4 , and H 2 / n -C 6 H 14 , respectively, surpassing the 2008 Robeson's upper bound. Notably, under high humidity conditions, the selectivities for H 2 /CO 2 , H 2 /CH 4 , and H 2 / n -C 6 H 14 are 1566 %, 1891 %, and 3264 % higher than those of the original PVDF membrane, achieving high selectivity separation. Additionally, after repetitive experiments with varying humidity, the membrane's selectivity remained almost unchanged, demonstrating the high hydrothermal stability of PVP2–Zr-MOF-F@PVDF. This research provides a new reference for hydrogen purification and holds significant implications for the sustainable development of green energy. [Display omitted] • Two-step in situ method for bifunctional hydrophobic MOF-MMMs. • PVP induces nucleation, prevents aggregation, and acts as a pore-forming agent. • Fluorine atoms enhance hydrophobicity and improve H 2 and hydrocarbon affinity. • High selectivity and permeability, enabling effective hydrogen purification. • Maintains efficient H 2 purification and hydrothermal stability under high humidity. [ABSTRACT FROM AUTHOR]

• 50-cm-long SSZ-13 zeolite membranes were prepared by secondary growth. • The typical large-area SSZ-13 zeolite membrane showed high N 2 /CH 4 selectivity of 13.3. • Membrane synthesis had a good reproducibility. • The membrane was stable in the presence of ethane, propane and saturated water vapor. Separating N 2 from CH 4 is challenging but critical for the purification of unconventional natural gas. Herein, large-area and high-quality SSZ-13 membranes were reproducibly produced on the 50-cm-long tubular alumina supports for the N 2 /CH 4 separation for the first time. The effects of test parameters such as pressure drop, temperature, feed flow rate, water vapor and hydrocarbon impurities on separation performance of the membrane were investigated. A mathematic model for concentration polarization (CP) index was established to evaluate the extent of CP. The CP can be released by decreasing feed pressure and increasing feed flow rate. Separation performance of semi-industrial-scale SSZ-13 membrane was superior to most small-area zeolite membranes. The membrane showed excellent stability in the presence of 5–10 % ethane and propane and saturated water vapor. Selectivity and permeance of the membrane can be restored to its initial values when the impurities are removed. The up-scaling and high-quality membranes have the great potentials for the industrial application in natural gas purification. [ABSTRACT FROM AUTHOR]

The usage of normal alumina supports brings the uncertain and undesirable aluminum transformation to the high-silica zeolite membranes to reduce Si/Al ratio in framework. In this current study, a novel aluminum-free silica carbide (SiC) monolithic support is used for the synthesis of SSZ-13 membranes with enhanced Si/Al ratio for the first time. Moreover, this high-porosity and monolithic SiC support enables membrane to increase gas permeance and surface-to-volume ratio. High-quality SSZ-13 membranes were prepared after rational modification of synthesis parameters such as synthesis temperature and time and support material. The effects of test temperature, pressure drop, feed flow rate and humidity on separation performance of the monolithic membranes were studied. The formation mechanism of SSZ-13 membrane was also investigated. The Si/Al ratio and CO 2 permeance of SSZ-13 membranes on SiC monolith were 100% and 60% higher than that of membrane on alumina monolith, respectively. This monolithic membrane had comparable separation performance but about 2.3 times higher surface-to-volume ratios to the reported tubular zeolite membranes. This solution could be suitable to prepare other high-silica and all-silica zeolite membranes. [Display omitted] • Uniform large-area SSZ-13 membranes were fabricated on novel SiC monolith. • CO 2 permeance is 50% higher than that of membrane on alumina monolith. • Si/Al ratio of zeolite membrane on SiC support is twice of that on alumina one. • The resistance to humidity increases compared with that of membrane on alumina support. • Surface-to-volume ratio of monolithic membrane is 2.3 times higher than that of tubular one. [ABSTRACT FROM AUTHOR]

Membrane-based pervaporation (PV) is an energy-efficient separation technology for liquid molecular mixtures, which is an increasingly important function in chemical industries. This work accomplished the first synthesis of high-performance FAU (NaX type) zeolite membranes on α-alumina tubular supports via the secondary growth method using 50 nm nanoseeds. The effects that the synthesis parameters exerted on the crystal structures, morphologies, and PV performance of FAU membranes were systematically investigated. The nanosized seeds showed high levels of activity that promoted the rapid growth of the zeolite layer. In addition, either extending the crystallization time or raising the temperature readily caused trans -crystallization to form NaP impurity zeolites, which decreased the membrane flux and separation factor. When synthesis conditions were optimized, a high-quality and pure-phase FAU membrane was obtained and tested for the permeation of single gases and for the PV dehydration of various organic solvents (methanol, ethanol, n-propanol, iso-propanol, and tert-butanol). The relationships between the single-gas permeance, PV permeance, and polarity index were investigated using a similar size range of permeate molecules (0.289–0.5061 nm). The results show that gas permeance exhibits Knudsen selectivity. The PV permeance, however, correlated well with the polarity index of the permeate, which indicates that PV dehydration through the FAU membrane is controlled by an adsorption-diffusion mechanism. Moreover, the correlation provides a new tool for predicting PV performance. Compared with studies using FAU membranes, the as-synthesized FAU membrane features good reproducibility, excellent stability, and high PV performance, which suggests the great potential of FAU membranes for use in industrial organic solvent dehydration. Schematic illustrations of the hydrothermal synthesis of FAU membranes derived from nanoseeds for pervaporation dehydration, as well as a PV performance prediction via the polarity index. [Display omitted] • Synthesis parameters are optimized to form a high-performance FAU membrane. • Nanoseeds are highly active and promote the growth of the zeolite layer. • PV dehydration is controlled by the adsorption-diffusion mechanism. • PV performance correlated well with the polarity index of solvents. • Polarity index is used to predict PV performance. [ABSTRACT FROM AUTHOR]

[Display omitted] • Semi-industrial-scale silicalite-1 membranes are applied to n -butane/methane separation. • The membranes have excellent separation performance for n -butane/methane mixtures. • The highest n -butane/methane separation factor of 935 so far is obtained. • Semi-industrial-scale silicalite-1 membranes display good long-term stability. The semi-industrial-scale tubular silicalite-1 membranes with a thickness of 8.4–8.9 µm were prepared and used for the separation of n -butane/methane mixture for the first time. The membranes remained highly [h0h] oriented. The effects of temperature, pressure and feed flow rate (Reynold numbers) on the separation performance for the 6-cm-long and 50-cm-long membranes were investigated. Separation stability of the semi-industrial-scale tubular silicalite-1 membrane was studied. The short silicalite-1 membranes displayed the highest n -butane/methane separation factor of 935 among the literature data so far and a permeance of n -butane of 0.5 × 10−8 mol/(m2 s Pa) at 243 K. Two long silicalite-1 membranes showed n- butane permeances of 3.1 × 10−8 and 1.9 × 10−8 mol/(m2 s Pa) and n- butane/methane separation factors of 72 and 110 at 298 K in the 10/90 mol% n -butane/methane mixture, respectively. The results displayed that silicalite-1 membranes have great potential application for removal of n -butane from natural gas mixtures. [ABSTRACT FROM AUTHOR]

The development of acid-stable zeolite membrane is still a great challenge for pervaporative dehydration of water/acetic acid mixtures. Herein, we reported the fabrication of high-quality zeolite SSZ-13 membranes on the 50-cm-long tubular alumina supports via vacuum seeding method. The uniform seed layer by vacuum seeding method resulted in a uniform and intergrown zeolite membrane with thickness of 8.0–9.0 μm. The typical membrane with membrane area of 180 cm2 and Si/Al ratio of 12 displayed extremely high water permeance of 2.4 × 10−6 mol m−2 s−1 Pa−1 and high selectivity of 7700 in a 40/60 wt% water/AcOH mixture at 363 K. The corresponding water flux and separation index were 7.0 kg m−2 h−1 and 1.95 mol m−2 s−1, respectively. The overall separation performance (for example separation index) of the large-area SSZ-13 membrane was the highest one among the reported membranes for water/acetic acid separation. The effects of feed concentration and temperature on membrane performances were investigated for the separation of H 2 O/AcOH mixtures. Water flux increased greatly but water permeance decreased a little with increasing water content in the mixture and temperature. Permeance is a driving force normalized form and reflects the inherent property of the membrane only. Stability of the membrane in aqueous AcOH solutions was also studied in the 10-d continuous test. [Display omitted] • Uniform 50-cm-long tubular SSZ-13 membranes were fabricated. • The membranes displayed the highest separation performance for water/AcOH separation. • Permeance was calculated to explain the partial pressure-derived separation. • The membrane displayed excellent acidic resistance in the hot acids over 7.0 d. [ABSTRACT FROM AUTHOR]

[Display omitted] • Pilot-scale SSZ-13 membranes were used for field test of CO 2 removal of biogas for the first time. • Ten SSZ-13 membranes displayed average CO 2 permeance of 2100 GPU and average CO 2 /CH 4 selectivity of 103. • Increasing the feed flow rate reduces the effect of concentration polarization. Large-area SSZ-13 membranes were reproducibly prepared on 50-cm-long commercial and alumina tubes by secondary growth. Separation performance of the long membranes were higher than that of most small-area membranes. The effects of operation parameters such as pressure, temperature, feed flow rate and CO 2 concentration on the separation performance of membranes were investigated. A mathematic model for concentration polarization index was established to evaluate the extent of concentration polarization in the single-tube and the muti-module test. A separation system with four single-tube modules connected in series was applied to field test of real biogas. The biogas could be purified to pipeline-grade natural gas (>98 mol%) by this small system at feed flow rate of 12 standard liter per minute at 1.4 MPa pressure drop. The membrane displayed long-term stability in the wet and dry biogas. This work has made an important progress toward the industrialization of zeolite membranes for gas separation. [ABSTRACT FROM AUTHOR]

High-quality tubular SSZ-13 zeolite membranes were fabricated by a facile in-situ approach for the first time. The in-situ approach requires only a single hydrothermal step for membrane growth, which is much simpler than the normal multi-step secondary-growth approach with seed preparation and seeding steps. The proper aging time and relatively high synthesis temperature provide sufficient nuclei for SSZ-13 growth, which further facilitates the in-situ formation of continuous membranes on the substrates. Three SSZ-13 zeolite membranes fabricated by the simple in-situ approach displayed ultrahigh average selectivity of (233 ± 46) and high average carbon dioxide permeance of (1220 ± 100) × 10−9 mol (m2 s Pa)−1 [∼3660 ± 300 Gas Permeation Unit (GPU), 1 GPU = 3.348 × 10−10 mol/(m2 s Pa)] at 298 K in the CO 2 /CH 4 (50/50 in mol) mixture. The overall separation performance of the current membranes exceeded that of most reported zeolite membranes in the CO 2 /CH 4 mixture. It indicated that the current in-situ synthesis approach had good reproducibility. The typical membrane also showed excellent separation performance in the CO 2 /N 2 mixture toward the carbon capture from flue gas. The long-term stability of this membrane was investigated in the humidified CO 2 /CH 4 mixture with a relative humidity close to 100%. This simple in-situ approach is suitable to prepare other zeolite membranes for gas separation after improving the gel nucleation. [Display omitted] • High-quality SSZ-13 membranes are fabricated by in-situ approach for the first time. • Sufficient nuclei in gel by rational synthesis modification is important. • These membranes display ultrahigh CO 2 /CH 4 selectivities and high CO 2 permeances. • The simple method is suitable to synthesize other zeolite membranes for gas separations. [ABSTRACT FROM AUTHOR]

[Display omitted] • 50-cm-long tubular silicalite-1 membranes were reproducibly prepared for the first time. • The membranes displayed high separation performance for butane isomer separation. • Membrane module properties were investigated using the industrial butane mixtures. • Isobutane recovery was as high as 93 % for a pilot-scale one-stage membrane system. We have reported scale-up synthesis of 50-cm-long tubular sililcalite-1 membranes and separation of industrial n -butane/ i -butane mixtures using the membrane modules for the first time. The membranes had 6-μm-thick, well-intergrown and [h0h]- oriented silicalite-1 layers. Twenty silicalite-1 membranes of the total twenty-one ones exhibited an average n -butane permeance, n -butane flux and separation factor of (6.5 ± 1.1) × 10-8 mol/(m2 s Pa), (35 ± 5.1) × 10-4 mol/(m2 s) and 25 ± 3.7, respectively, for the industrial n -butane/ i -butane (∼30/70 mol%) mixture at 363 K. It suggests that membrane fabrication had good reproducibility. The separation performance of membrane modules with different membrane elements was studied. A practical separation test was performed for the industrial n -/ i -butane mixture using membrane setup assembled by seven 3-tube membrane modules with a total membrane area of 0.38 m2. The separation system displayed excellent separation performance and stability during continuous test for 48 h. Isobutane concentration in the retentate side was enriched to > 98 mol% from 70 mol% in the feed with recovery of 83 % for the one-stage separation system at 363 K when the flow rate was 3.0 standard L/min (4.32 m3/d). The results show that silicalite-1 membranes are promising candidates for industrial separation of n -/ i -butane mixtures. [ABSTRACT FROM AUTHOR]

Continuous and thin all-silica zeolite CHA membranes were prepared successfully on the tubular zirconia/alumina supports by a novel fluoride-free synthesis approach using lithium hydroxide as mineralizer. Membrane synthesis using the uniform and low-viscosity gel displayed good reproductivity. The influences of pressure and temperature on separation data of the membrane in the dry and wet mixtures were comprehensively investigated. The typical membrane had CO 2 /CH 4 and CO 2 /N 2 selectivities of 170 and 33 and carbon dioxide permeances of 950 × 10−9 and 1200 × 10−9 mol/(m2 s Pa) [∼3600 GPU, Gas Permeation Unit: 1GPU = 3.348 × 10−10 mol/(m2 s Pa)] at 298 K in dry CO 2 /CH 4 and CO 2 /N 2 (50/50 in mol) mixtures, respectively. The unprecedentedly high CO 2 /CH 4 selectivity of 430 was obtained for the zeolite membrane at 298 K in wet CO 2 /CH 4 mixture with saturated water vapor. The long-term stability of this membrane was also investigated in humidified mixture with relative humidity of close to 100%. The possible water-gated molecular sieve mechanism in the presence of moisture was proposed. [Display omitted] • Si-CHA zeolite membrane was prepared using a new fluorite-free route using LiOH. • ZrO 2 was acted as a barrier layer to inhibit the aluminum transformation from the support. • The membrane displayed extremely high CO 2 /CH 4 selectivity of over 400 in wet mixture. • High performance zeolite Si-CHA membranes were reproducibly synthesized. [ABSTRACT FROM AUTHOR]

Background: Although highly heterogeneous among countries, the incidence rates of low birth weight (LBW), preterm birth (PTB), and small for gestational age (SGA) have been increasing globally over the past two decades. To better understand the cause of these secular trends, this study aimed to investigate the effects of age, period, and birth cohort on LBW, PTB, and SGA rates in Shanghai., Methods: Data from 2,958,695 singleton live births at 24-41 gestational weeks between 2004 and 2020 were obtained for this study. Age-period-cohort models based on Poisson regression were used to evaluate the independent effects of maternal age, delivery period, and maternal birth cohort on the trends in LBW, PTB, and SGA., Results: The overall prevalence rates of LBW, PTB, and SGA were 2.9%, 4.7%, and 9.3%, respectively, and significant changes were observed (average annual change: + 10.7‰, + 9.1‰, -11.9‰) from 2004 to 2020. Cohort effect increased steadily, from 1960 (risk ratio [RR] = 0.71, 95% confidence interval [CI]: 0.65-0.78) to 1993 (RR = 0.97, 95% CI: 0.94-1.01) for LBW and from 1960 (RR = 0.69, 95% CI: 0.64-0.75) to 2004 (RR = 1.02, 95% CI: 0.94-1.12) for PTB. A strong cohort effect was found with the highest risk of SGA (RR = 1.82, 95% CI: 1.72-1.93) in 1960 and the lowest risk (RR = 0.57, 95% CI: 0.54-0.61) in 2004, compared with the reference cohort of 1985. There was a "U-shaped" maternal age effect on LBW and PTB and a weak period effect on the three birth outcomes., Conclusions: Our findings suggested a significant independent effect of age, period, and birth cohort on the three birth outcomes. The increasing rates of LBW and PTB motivated us to focus on young and advanced pregnant women. Meanwhile, the prevalence of SGA decreased steadily, illustrating the need for further research on the mechanisms underlying these trends., (© 2023. The Author(s).)

Cation-free zirconosilicate zeolite CHA and thin zirconia-supported membranes were in situ synthesized in a fluoride-free gel for the first time. The usage of the ZrO 2 /Al 2 O 3 composite support inhibited the transportation of aluminum from the support into zeolite membranes. No fluorite source was used for the synthesis of cation-free zeolite CHA membranes, indicating the green property of the synthesis. The thickness of the membrane was only 1.0 μm. The best cation-free zeolite CHA membrane prepared by the green in situ synthesis displayed a high CO 2 permeance of 1.1 × 10 -6 mol/(m 2 s Pa) and CO 2 /CH 4 selectivity of 79 at 298 K and 0.2 MPa pressure drop for an equimolar CO 2 /CH 4 mixture.

Precise molecular and ion separations depend largely on the size and uniformity of the nanochannels in a defect-free microporous nanofilm. Ordered and perpendicular nanochannels with uniform pore size are assembled into a continuous and defect-free film by a "gel nuclei-less" route. The ultrathin (<50 nm) zeolite nanosheets seeding layer induces the formation of defect-free zeolite nanofilms (500-800 nm) with preferential [100] orientation well-aligned to the transport pathway. The large-area and thin silicoaluminophosphate-34 (SAPO-34) nanofilm consisting of uniform and straight nanochannels shows a milestone CO 2 permeance of ≈1.0 × 10 -5 mol (m 2 s Pa) -1 and high CO 2 /CH 4 and CO 2 /N 2 selectivities of 135 and 41 in equimolar binary mixtures at room temperature and 0.2 MPa feed pressure, respectively. These results suggest that highly oriented and thin SAPO-34 nanofilms prepared from nanosheets might have great potential for CO 2 capture from natural gas, biogas, and flue gas., (© 2020 Wiley-VCH GmbH.)