Search

Highly b‐oriented MFI zeolite (abbreviated as BOMZ) membranes are attractive due to less grain boundary defects and straight channels normal to the substrate, enhancing selectivity and flux in membrane separation. Herein, we demonstrate a novel, effective and easily‐amplified printing‐transfer oriented‐seed‐layer technique to manufacture uniform BOMZ seed monolayer on porous supports. Furthermore, a facile and effective approach for the synthesis of highly BOMZ membranes by introducing poly(hexamethylene biguanide) hydrochloride as a twin crystal inhibitor during seeded growth is demonstrated. Well‐intergrown BOMZ membranes (∼650 nm thick) obtained on porous Al2O3 supports show a flux of 2.8 kg m−2 h−1 with a separation factor as high as 71 for pervaporation in the 60 °C feed of EtOH/H2O (5 wt%), which is much higher than those of random membranes. The developed seed assembly technique on porous supports underlines great potential for facile preparation of oriented seed layers on porous supports. [ABSTRACT FROM AUTHOR]

Weakening the mass transfer resistance inside the selective layer of membrane can effectively increase the membrane separation performance. In this study, we introduce macropores into the conventional LTA zeolite membrane layer, resulting in an unprecedented hierarchical membrane structure. Specifically, the hierarchical LTA zeolite membranes composed of a macroporous zeolite layer and a thin dense top layer (600 nm), are fabricated on rough α -Al 2 O 3 tubular supports by vapor phase transformation method using mesoporous silica spheres (MSPs) as the porogen in the precursor layer. The H 2 (N 2) permeance of the hierarchical LTA zeolite membrane is near 10 times that of the conventional LTA zeolite membrane, indicating that the hierarchical pore structure can effectively weaken the mass transfer resistance inside the selective layer of membrane. And it has good pervaporation performance for 90 wt% ethanol aqueous solution at 348 K, i.e. , the flux can reach 4.54 kg m−2 h−1 with a separation factor of >10,000, which is much higher than that of the conventional LTA zeolite membrane. The preparation of LTA zeolite membranes with hierarchical pore structure using MSPs as a porogen is expected to open up a new way for the construction of zeolite membranes. • Mesoporous silica microspheres as the porogen and silica source. • Hierarchical membrane structure can effectively decrease the permeation resistance. • Solid waste was greatly reduced by vapor phase transformation process. [ABSTRACT FROM AUTHOR]

Zeolite membranes are broadly applied in separation, catalysis, and sensor, yet challenges remain in the preparation process. The design of support is an important component to simplify the synthesis protocol and improve the repeatability. Herein, we present a facile and universal strategy to fabricate high-performance zeolite membranes via engineering the skeleton of hollow fiber supports, on which a variety of high-performance zeolite membranes (e.g., MFI, LTA and FAU) can be obtained just by in-situ crystallization without any modification. The "reactive" support is fabricated by implanting zeolite crystals (e.g., NaA) in the precursor of porous ceramic alumina support. Being dissolved under alkaline condition of the synthesis solution, the zeolite calcination transformant (e.g., NaA-Cal) produced in the support during sintering process can effectively form nucleation sites on the support surface, and continuously provide active species to ensure the continuity of the membrane. This study contributes new insights into the importance of supports for high-performance zeolite membranes. Meanwhile, the synthetic methodology is expected to expand the preparation method of zeolite membranes and promote the large-scale application of zeolite membranes. [Display omitted] • Implanting zeolite crystals into the ceramic slurry for preparation of versatile supports. • A variety of high-performance zeolite membranes can be obtained on the support. • No modification or repeated synthesis is needed using the versatile support. [ABSTRACT FROM AUTHOR]

The hydrothermal synthesis for the fabrication of zeolite coatings is the most effective route and has been extensively studied, in which a large amount of water is indispensable to ensure efficient transport of nutrition. The disposal of waste solvent and chemicals remains a big challenge in practice and an alternative route is highly desired. Herein, we present an unprecedented solid-conversion secondary growth route for the fabrication of corrosion-resistant MFI-type zeolite coatings by mixing, grinding, and heating the mixture of silica source (Na 2 SiO 3 ·9H 2 O and SiO 2), template (TPABr) and acidity regulator (NH 4 Cl) without addition of water. The ZSM-5 zeolite seeded aluminum alloy 1060 plates were prepared by spray-coating method where water glass as a binder between seed and substrate was used to increase the adhesion of seeds to the substrate. The continuity of the coatings was investigated by manipulating the molar composition of synthesis mixture and the optimized molar composition is 1.0Na 2 SiO 3 ·9H 2 O: 1.19SiO 2 : 0.58TPABr: 1.82NH 4 Cl. The corrosion protection performance of MFI-type zeolite coatings on aluminum alloy plates was evaluated by a direct current polarization technique. The excellent corrosion-resistant was demonstrated in severely corrosive medium including in 0.5 M H 2 SO 4 aqueous solution and 0.5 M NaCl aqueous solution, which is comparable to the performance of zeolite coatings synthesized by hydrothermal synthesis. The features are also briefly discussed, which make this route highly attractive from a good perspective. Image 1 ● The synthesis of MFI-type zeolite coatings by solid-conversion secondary growth route. ● Spray-coating was introduced to produce a continuous seed layer. ● Significant effect of the composition of synthesis mixture in solid-conversion method. ● MFI-type zeolite coatings are corrosion-resistant in severely corrosive medium. [ABSTRACT FROM AUTHOR]

Microstructural manipulation has been proven to remarkably affect the performance of zeolite membranes/films in separation and catalysis. Accordingly, intensive research and significant progress have been achieved in the last decades on the microstructural manipulation of zeolite films/membranes. From the literature, various factors including supports, seed layer, growth methods, synthesis solution, crystallization condition, and post-treatment can result in the different microstructures of zeolite films/membranes including morphology, orientation, thickness, and composition of the dense layer. This review attempts to summarize the obtained progress in microstructural manipulation of MFI-type zeolite films/membranes and their relationship with the separation performance. Some key topics are detailed and discussed, including (1) controllable synthesis of orientated zeolite films/membranes; (2) rational design and synthesis of zeolite films/membranes with ultrathin separation layer; (3) construction of asymmetric zeolite membranes; (4) architectural design of zeolite films/membranes at the microscopic level (heteroatoms substituted zeolite films/membranes); (5) the challenges and strategies in scaling-up of zeolite film/membrane production. Concluding remarks and perspectives are also suggested in the end. [Display omitted] • The relationship between separation performance and microstructure is summarized. • Various microstructural engineering of zeolite membranes are described in detail. • The novel strategies for architectural design of zeolite membranes are highlighted. • The advancements and challenges of scale-up fabrication are discussed. • The prospective of zeolite membrane industrial application is proposed. [ABSTRACT FROM AUTHOR]