Metal–Organic Frameworks for Separations

"Space—the final frontier." This preamble to a well-known television series captures the challenge encountered not only in space travel adventures, but also in the field of porous materials, which aims to control the size, shape and uniformity of the porous space and the atoms and molecules that define it. The past decade has seen significant advances in the ability to fabricate new porous solids with ordered structures from a wide range of different materials. This has resulted in materials with unusual properties and broadened their application range beyond the traditional use as catalysts and adsorbents. In fact, porous materials now seem set to contribute to developments in areas ranging from microelectronics to medical diagnosis.

Ordered porous materials for emerging applications

The Hydrothermal Synthesis of Zeolites: History and Development from the Earliest Days to the Present Time

3.2. Preparation 4090 3.3. Intermediate Layers 4090 3.4. Support 4090 3.5. Modification 4091 3.5.1. Silica Membrane Modification 4091 3.5.2. Membrane Structure Modification 4092 3.6. Operational Stability 4092 4. Zeolite Membranes 4092 4.1. Membrane Growth Methods 4093 4.2. Permeation and Gas Transport 4093 4.3. Defect Site Diffusion/Nonzeolitic Pores 4094 4.4. Thin Films 4094 4.5. Zeolite Membrane Modification 4094 4.6. CO2 Sequestration in H2 Separations 4095 4.7. Manufacturing 4095 5. Carbon-Based Membranes 4096 5.1. Carbon Membrane Preparations 4097 5.2. Carbon Membrane Post-treatment 4097 5.3. Carbon Membrane Module Construction 4097 5.4. Selective Surface Flow Membranes 4097 5.5. Disadvantages of Carbon Membranes 4098 5.6. Molecular Sieving Carbon Membranes 4098 5.7. Carbon Nanotubes 4099 6. Polymer Membranes for H2 Separations 4100 6.1. Dense Polymeric Membranes 4100 6.2. Hydrogen Selective Polymeric Membranes 4101 6.3. H2 versus CO2 Selective Polymeric Membranes 4103

Membranes for hydrogen separation.

Zeolite membranes – state of their development and perspective

Continuous polycrystalline films of ZSM-5 (MFI-type) crystals have been grown on porous ceramic (clay) supports. The films are thermomechanically stable upon calcination at 400 °C in air to remove template ions (tetrapropylammonium), during which process the porous support seems to have a stabilizing effect. When the hydrothermal conditions induce substantial aluminium leaching from the support, large analcime crystals are grown on the support. Gas permeation experiments with both pure gases (permanent gases, alkanes and difluorodichloromethane) and mixtures thereof have been performed on the MFI composite to investigate the separation potential of this new type of membrane. Expected selectivities as a result of large differences in diffusivity are found to be strongly reduced by differences in sorption of the same order of magnitude, and the reduced mobility of weakly adsorbing (fast moving) molecules caused by the slower moving species. However, from the observed low permeation rates it is expected that, owing to the presence of a porous support with relatively low porosity, the molecular sieving effect is reduced as well.

Synthesis and characterization of zeolite (MFI) membranes on porous ceramic supports

High-temperature stainless steel supported zeolite (MFI) membranes: Preparation, module construction, and permeation experiments

Calcination of large MFI-type single crystals, Part 2: Crack formation and thermomechanical properties in view of the preparation of zeolite membranes

Calcination of large MFI-type single crystals: Part 1. Evidence for the occurrence of consecutive growth forms and possible diffusion barriers arising thereof

Inorganic composite membrane containing molecular sieve crystals, comprising a macroporous support to which molecular sieve crystals and modifications thereof have been applied substantially as a monolayer, said crystals and modifications thereof having been oriented so that, to a substantial extent, the pores of the sieve crystals form a significant included angle with the support surface, there being present between the crystals a gastight matrix, at least gastight to a degree sufficient under practical conditions.

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E.R. Geus

Papers

Synthesis and characterization of zeolite (MFI) membranes on porous ceramic supports

High-temperature stainless steel supported zeolite (MFI) membranes: Preparation, module construction, and permeation experiments

Calcination of large MFI-type single crystals, Part 2: Crack formation and thermomechanical properties in view of the preparation of zeolite membranes

Calcination of large MFI-type single crystals: Part 1. Evidence for the occurrence of consecutive growth forms and possible diffusion barriers arising thereof

Inorganic composite membrane comprising molecular sieve crystals