Editorial

3 pages, 183 KiB

Open AccessEditorial

Zeolite Membrane: From Microstructure to Separation Performance

by Tomohiro Kyotani and Hannes Richter

Membranes 2022, 12(2), 176; https://0-doi-org.brum.beds.ac.uk/10.3390/membranes12020176 - 02 Feb 2022

Cited by 3 | Viewed by 1715

Zeolite membrane have been investigated all over the world as an attractive tool in the development of separation processes for both liquid and gaseous components [...] Full article

(This article belongs to the Special Issue Zeolite Membrane: From Microstructure to Separation Performance)

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9 pages, 2586 KiB

Open AccessArticle

Membrane Reactor for Methanol Synthesis Using Si-Rich LTA Zeolite Membrane

by Masahiro Seshimo, Bo Liu, Hey Ryeon Lee, Katsunori Yogo, Yuichiro Yamaguchi, Nobuyuki Shigaki, Yasuhiro Mogi, Hidetoshi Kita and Shin-ichi Nakao

Membranes 2021, 11(7), 505; https://0-doi-org.brum.beds.ac.uk/10.3390/membranes11070505 - 30 Jun 2021

Cited by 10 | Viewed by 3429

Abstract

We successfully demonstrated the effect of a membrane reactor for methanol synthesis to improve one-pass CO₂ conversion. An Si-rich LTA membrane for dehydration from a methanol synthesis reaction field was synthesized by the seed-assisted hydrothermal synthesis method. The H₂O permselective [...] Read more.

We successfully demonstrated the effect of a membrane reactor for methanol synthesis to improve one-pass CO₂ conversion. An Si-rich LTA membrane for dehydration from a methanol synthesis reaction field was synthesized by the seed-assisted hydrothermal synthesis method. The H₂O permselective performance of the membrane showed 1.5 × 10⁻⁶ mol m⁻² s⁻¹ Pa⁻¹ as H₂O permeance and around 2000 as selectivity of H₂O/MeOH at 473 K. From the results of membrane reactor tests, the CO₂ conversion of the membrane reactor was higher than that of the conventional packed-bed reactor under the all of experimental conditions. Especially, at 4 MPa of reaction pressure, the conversion using the membrane reactor was around 60%. In the case of using a packed-bed reactor, the conversion was 20% under the same conditions. In addition, the calculated and experimental conversion were in good agreement in both the case of the membrane reactor and packed-bed reactor. Full article

(This article belongs to the Special Issue Zeolite Membrane: From Microstructure to Separation Performance)

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15 pages, 2865 KiB

Open AccessArticle

Separation of H₂O/CO₂ Mixtures by MFI Membranes: Experiment and Monte Carlo Study

by Alexander Wotzka, Majid Namayandeh Jorabchi and Sebastian Wohlrab

Membranes 2021, 11(6), 439; https://0-doi-org.brum.beds.ac.uk/10.3390/membranes11060439 - 10 Jun 2021

Cited by 13 | Viewed by 3486

Abstract

The separation of CO₂ from gas streams is a central process to close the carbon cycle. Established amine scrubbing methods often require hot water vapour to desorb the previously stored CO₂. In this work, the applicability of MFI membranes for [...] Read more.

The separation of CO₂ from gas streams is a central process to close the carbon cycle. Established amine scrubbing methods often require hot water vapour to desorb the previously stored CO₂. In this work, the applicability of MFI membranes for H₂O/CO₂ separation is principally demonstrated by means of realistic adsorption isotherms computed by configurational-biased Monte Carlo (CBMC) simulations, then parameters such as temperatures, pressures and compositions were identified at which inorganic membranes with high selectivity can separate hot water vapour and thus make it available for recycling. Capillary condensation/adsorption by water in the microporous membranes used drastically reduces the transport and thus the CO₂ permeance. Thus, separation factors of α_H2O/CO2 = 6970 could be achieved at 70 °C and 1.8 bar feed pressure. Furthermore, the membranes were tested for stability against typical amines used in gas scrubbing processes. The preferred MFI membrane showed particularly high stability under application conditions. Full article

(This article belongs to the Special Issue Zeolite Membrane: From Microstructure to Separation Performance)

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9 pages, 2863 KiB

Open AccessArticle

Contribution of Pore-Connectivity to Permeation Performance of Silicalite-1 Membrane; Part II, Diffusivity of C₆ Hydrocarbon in Micropore

by Motomu Sakai, Yukichi Sasaki, Takuya Kaneko and Masahiko Matsukata

Membranes 2021, 11(6), 399; https://0-doi-org.brum.beds.ac.uk/10.3390/membranes11060399 - 27 May 2021

Cited by 5 | Viewed by 2282

Abstract

This study investigated the permeation behaviors of n-hexane and 2-methylpentane through two-types of silicalite-1 membranes that have different pore-connectivity. The permeation mechanisms of these hydrocarbons were able to be explained by the adsorption–diffusion model. In addition, the fluxes through silicalite-1 membranes could [...] Read more.

This study investigated the permeation behaviors of n-hexane and 2-methylpentane through two-types of silicalite-1 membranes that have different pore-connectivity. The permeation mechanisms of these hydrocarbons were able to be explained by the adsorption–diffusion model. In addition, the fluxes through silicalite-1 membranes could be expressed by the modified Fick’s first law. The hydrocarbon fluxes through S-1_S with better pore-connectivity were ca. 3–20 times larger than those through S-1_M with poor pore-connectivity. For these membranes with different pore-connectivity, the activation energy of diffusion of n-hexane was 17.5 kJ mol⁻¹ for the membrane with better pore-connectivity and 18.0 kJ mol⁻¹ for the membrane with poorer pore-connectivity, whereas for 2-methylpentane it was 17.9 and 33.0 kJ mol⁻¹, respectively. We concluded that the pore-connectivity in silicalite-1 membrane significantly influences the molecular diffusivities. Full article

(This article belongs to the Special Issue Zeolite Membrane: From Microstructure to Separation Performance)

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13 pages, 4077 KiB

Open AccessArticle

Prediction of Adsorption and Diffusion Behaviors of CO₂ and CH₄ in All-Silica Zeolites Using Molecular Simulation

by Yasuhisa Hasegawa and Chie Abe

Membranes 2021, 11(6), 392; https://0-doi-org.brum.beds.ac.uk/10.3390/membranes11060392 - 26 May 2021

Cited by 4 | Viewed by 2794

Abstract

Computational chemistry is a promising technique for the prediction of material properties. Adsorption and diffusion behaviors in zeolite micropores are important for zeolite membranes. In this study, we investigated novel non-bonding interaction parameters of all-silica zeolites for the prediction of the adsorption and [...] Read more.

Computational chemistry is a promising technique for the prediction of material properties. Adsorption and diffusion behaviors in zeolite micropores are important for zeolite membranes. In this study, we investigated novel non-bonding interaction parameters of all-silica zeolites for the prediction of the adsorption and diffusion behaviors by focusing on the Si atom of zeolite frameworks. Our parameters (σ = 0.421 nm, ε = 0.954 kJ mol⁻¹, and q = +1.10 e) were close to theoretically derived values, and the adsorption isotherms of CO₂ and CH₄ on several zeolites could be predicted with high accuracy. Furthermore, the parameters gave the suitable self-diffusivities of CO₂ and CH₄ within MFI-type zeolite micropores through molecular dynamics simulation. Those suggest that our derived parameters are useful for selecting zeolite structure as the membrane material. Full article

(This article belongs to the Special Issue Zeolite Membrane: From Microstructure to Separation Performance)

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14 pages, 4549 KiB

Open AccessArticle

Contribution of Pore-Connectivity to Permeation Performance of Silicalite-1 Membrane; Part I, Pore Volume and Effective Pore Size

by Motomu Sakai, Yukichi Sasaki, Takuya Kaneko and Masahiko Matsukata

Membranes 2021, 11(6), 382; https://0-doi-org.brum.beds.ac.uk/10.3390/membranes11060382 - 24 May 2021

Cited by 9 | Viewed by 2250

Abstract

The micropore volumes and effective pore sizes of two types of silicalite-1 membranes were compared with those of a typical silicalite-1 powder. The silicalite-1 membrane with fewer grain boundaries in the membrane layer showed similar micropore volume and effective pores size to those [...] Read more.

The micropore volumes and effective pore sizes of two types of silicalite-1 membranes were compared with those of a typical silicalite-1 powder. The silicalite-1 membrane with fewer grain boundaries in the membrane layer showed similar micropore volume and effective pores size to those of the silicalite-1 powder. In contrast, when the silicalite-1 membrane contained many grain boundaries, relatively small micropore volume and effective pore size were observed, suggesting that narrowing and obstruction of the micropore would occur along grain boundaries due to the disconnection of the zeolite pore. The silicalite-1 membrane with fewer grain boundaries exhibited relatively high permeation properties for C₆-C₈ hydrocarbons. There was an over 50-fold difference in benzene permeance between these two types of membranes. We concluded that it is important to reduce grain boundaries and improve pore-connectivity to develop an effective preparation method for obtaining a highly permeable membrane. Full article

(This article belongs to the Special Issue Zeolite Membrane: From Microstructure to Separation Performance)

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10 pages, 711 KiB

Open AccessArticle

Development of Ammonia Selectively Permeable Zeolite Membrane for Sensor in Sewer System

by Hisao Inami, Chie Abe and Yasuhisa Hasegawa

Membranes 2021, 11(5), 348; https://0-doi-org.brum.beds.ac.uk/10.3390/membranes11050348 - 10 May 2021

Cited by 9 | Viewed by 2756

Abstract

Ammonia (NH₃) and hydrogen sulfide (H₂S) are hazardous and odorous gases. A special device that is not affected by other gases is necessary so that it can detect such gases. Zeolite membranes can separate the desired component selectively by [...] Read more.

Ammonia (NH₃) and hydrogen sulfide (H₂S) are hazardous and odorous gases. A special device that is not affected by other gases is necessary so that it can detect such gases. Zeolite membranes can separate the desired component selectively by molecular sieving and selective adsorption. LTA-, MFI-, and FAU-type zeolite membranes were prepared in this study, and the permeation and separation performances were determined for the ternary mixture of NH₃, H₂S, and N₂ to develop an NH₃ selectively permeable membrane. Although the separation factors of NH₃ were high enough for the LTA-type zeolite membrane, the NH₃ permeance was the lowest among the three membranes. In contrast, the FAU-type zeolite membrane with Si/Al = 1.35 showed a high enough NH₃ permeance and a NH₃/N₂ separation factor. The membrane modification and varying the membrane composition were carried out to reduce the H₂S permeance. As a result, the H₂S permeance could be decreased by modification with silane coupling agents, and a separation factor of NH₃ toward H₂S of over 3000 was achieved. Full article

(This article belongs to the Special Issue Zeolite Membrane: From Microstructure to Separation Performance)

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13 pages, 9073 KiB

Open AccessArticle

Influence of Organic Solvent Species on Dehydration Behaviors of NaA-Type Zeolite Membrane

by Yasuhisa Hasegawa, Wakako Matsuura, Chie Abe and Ayumi Ikeda

Membranes 2021, 11(5), 347; https://0-doi-org.brum.beds.ac.uk/10.3390/membranes11050347 - 10 May 2021

Cited by 10 | Viewed by 2604

Abstract

In this study, an NaA-type zeolite membrane was prepared, and the dehydration performances of the membrane were determined by the pervaporation for several organic solvents to understand the lower dehydration performances of zeolite membranes for NMP solutions than those for alcohols. For a [...] Read more.

In this study, an NaA-type zeolite membrane was prepared, and the dehydration performances of the membrane were determined by the pervaporation for several organic solvents to understand the lower dehydration performances of zeolite membranes for NMP solutions than those for alcohols. For a 90 wt% ethanol solution at 348 K, the permeation flux and separation factor of the membrane were 3.82 kg m⁻² h⁻¹ and 73,800, respectively. The high dehydration performances were also obtained for alcohols and low boiling solvents (acetonitrile, acetone, methyl ethyl ketone (MEK) and tetrahydrofuran (THF)). However, the permeation flux and separation factors decreased significantly for high boiling solvents, such as N,N-dimethylacetamide (DMA), N,N-dimethyl formamide (DMF), dimethyl sulfoxide (DMSO) and N-methyl-2-pyrrolidone (NMP). The influences of the water content and temperature on the dehydration performances for the NMP solutions were determined to understand the lower dehydration performances for those solvents. Those results suggest that the lower dehydration performances for the high boiling solvents were attributed to the lower vapor pressures of water and the higher permeances of those solvents. Furthermore, this study proposes that the permeation behaviors through zeolite membranes could be understood by the determination of the effect of temperature on the permeance of individual components. Full article

(This article belongs to the Special Issue Zeolite Membrane: From Microstructure to Separation Performance)

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10 pages, 2360 KiB

Open AccessArticle

Gas Permeation Properties of High-Silica CHA-Type Zeolite Membrane

by Yasuhisa Hasegawa, Chie Abe, Mayumi Natsui and Ayumi Ikeda

Membranes 2021, 11(4), 249; https://0-doi-org.brum.beds.ac.uk/10.3390/membranes11040249 - 30 Mar 2021

Cited by 23 | Viewed by 2816

Abstract

The polycrystalline CHA-type zeolite layer with Si/Al = 18 was formed on the porous α-Al₂O₃ tube in this study, and the gas permeation properties were determined using single-component H₂, CO₂, N₂, CH₄, [...] Read more.

The polycrystalline CHA-type zeolite layer with Si/Al = 18 was formed on the porous α-Al₂O₃ tube in this study, and the gas permeation properties were determined using single-component H₂, CO₂, N₂, CH₄, n-C₄H₁₀, and SF₆ at 303–473 K. The membrane showed permeation behavior, wherein the permeance reduced with the molecular size, attributed to the effect of molecular sieving. The separation performances were also determined using the equimolar mixtures of N₂–SF₆, CO₂–N₂, and CO₂–CH₄. As a result, the N₂/SF₆ and CO₂/CH₄ selectivities were as high as 710 and 240, respectively. However, the CO₂/N₂ selectivity was only 25. These results propose that the high-silica CHA-type zeolite membrane is suitable for the separation of CO₂ from CH₄ by the effect of molecular sieving. Full article

(This article belongs to the Special Issue Zeolite Membrane: From Microstructure to Separation Performance)

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13 pages, 11554 KiB

Open AccessArticle

Pervaporative Dehydration of Organic Solvents Using High-Silica CHA-Type Zeolite Membrane

by Yasuhisa Hasegawa, Chie Abe and Ayumi Ikeda

Membranes 2021, 11(3), 229; https://0-doi-org.brum.beds.ac.uk/10.3390/membranes11030229 - 23 Mar 2021

Cited by 24 | Viewed by 3206

Abstract

A high-silica chabazite (CHA) type zeolite membrane was prepared on the porous α-Al₂O₃ support tube by the secondary growth of seed particles. The dehydration performances of the membrane were determined using methanol, ethanol, 2-propanol, acetone, acetic acid, methyl ethyl ketone [...] Read more.

A high-silica chabazite (CHA) type zeolite membrane was prepared on the porous α-Al₂O₃ support tube by the secondary growth of seed particles. The dehydration performances of the membrane were determined using methanol, ethanol, 2-propanol, acetone, acetic acid, methyl ethyl ketone (MEK), tetrahydrofuran (THF), N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), and N-methyl-2-pyrolidone (NMP) at 303–373 K. As a result, the dehydration performances of the membrane were categorized to following three types: (1) 2-propanol, acetone, THF, and MEK; (2) ethanol and acetic acid; and (3) methanol, DMF, and DMSO, and NMP. The adsorption isotherms of water, methanol, ethanol, and 2-propanol were determined to discuss the influences of the organic solvents on the permeation and separation performances of the membrane. For 2-propanol, acetone, MEK, and THF solutions, the high permeation fluxes and separation factors were obtained because of the preferential adsorption of water due to molecular sieving. In contrast, the permeation fluxes and separation factors were relatively low for methanol, DMF, and DMSO, and NMP solutions. The lower dehydration performance for the methanol solution was due to the adsorption of methanol. The permeation fluxes for ethanol and acetic acid solution were ca. 1 kg m⁻² h⁻¹. The significantly low flux was attributed to the similar molecular diameter to the micropore size of CHA-type zeolite. Full article

(This article belongs to the Special Issue Zeolite Membrane: From Microstructure to Separation Performance)

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14 pages, 3724 KiB

Open AccessFeature PaperArticle

Effect of Pore Connectivity on the Behavior of Fluids Confined in Sub-Nanometer Pores: Ethane and CO₂ Confined in ZSM-22

by Mohammed Musthafa Kummali, David Cole and Siddharth Gautam

Membranes 2021, 11(2), 113; https://0-doi-org.brum.beds.ac.uk/10.3390/membranes11020113 - 05 Feb 2021

Cited by 7 | Viewed by 4119

Abstract

The behavior of fluids under nano-confinement varies from that in bulk due to an interplay of several factors including pore connectivity. In this work, we use molecular dynamics simulations to study the behavior of two fluids—ethane and CO₂ confined in ZSM-22, a [...] Read more.

The behavior of fluids under nano-confinement varies from that in bulk due to an interplay of several factors including pore connectivity. In this work, we use molecular dynamics simulations to study the behavior of two fluids—ethane and CO₂ confined in ZSM-22, a zeolite with channel-like pores of diameter 0.55 nm isolated from each other. By comparing the behavior of the two fluids in ZSM-22 with that reported earlier in ZSM-5, a zeolite with pores of similar shape and size connected to each other via sinusoidal pores running perpendicular to them, we reveal the important role of pore connectivity. Further, by artificially imposing pore connectivity in ZSM-22 via inserting a 2-dimensional slab-like inter-crystalline space of thickness 0.5 nm, we also studied the effect of the dimensionality and geometry of pore connectivity. While the translational motion of both ethane and CO₂ in ZSM-22 is suppressed as a result of connecting the pores by perpendicular quasi-one-dimensional pores of similar dimensions, the effect of connecting the pores by inserting the inter-crystalline space is different on the translational motion of the two fluids. For ethane, pores connected via inter-crystalline space facilitate translational motion but suppress rotational motion, whereas in the case of CO₂, both types of motion are suppressed by pore connection due to the strong interaction of CO₂ with the surface of the substrate. Full article

(This article belongs to the Special Issue Zeolite Membrane: From Microstructure to Separation Performance)

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