Mixed matrix composite membrane

Kulkami, S. and Hasse, D.J. (2007) Novel polyimide based mixed matrix composite membranes. US Patent Application 2007/0199445 Al. 

C.M. ZiMMERMANN, A. SiNGH, W.J. Koros, Tailoring mixed matrix composite membranes for gas separations. 

However, membranes can be symmetric or asymmetric. Many porous or dense membranes are asymmetric and have one or several more porous supporting layers and a thin skin layer which, in fact, gives selectivity. If these two layers are made of different materials, the membrane is a composite one. On some occasions, dense membranes have inclusions of other materials these are, of course, also composite membranes. In the case of gas separation membranes it has became usual to include inorganic charges in a polymeric membrane to get what is called a mixed matrix composite membrane. 

Finally, other possible way to produce useful membranes is to mix a certain material (usually a polymer with good mechanical and chemical properties) with another material (an activated carbon for example) with better selectivity-permeability performances but which it is not advisable to use alone in the actual gas environment for a given application or which is difficult to obtain in a resistant film layer. This constitutes what is called a mixed matrix composite membrane (MMCM). 

Figure S.l An scheme of the different possible ways of evolution of a given polymer by introduction of a filler depending on the quality of the interface formed in the resulting mixed matrix composite membrane.

Figure 1. Proposed MMC membrane formation. (Reprinted from J. Membr. Sci., 137, C. M. Zimmerman, A. Singh and W. J Koros, Tailoring mixed matrix composite membranes for gas separations, 145 - 154, Copyright (1997), with permission from Elsevier Science)...

Li T, Pan Y, Peinemann K-V, Lai Z. Carbon dioxide selective mixed matrix composite membrane containing ZIF-7 nanofiller. J Membr Sci 2013 425 235-12. 

Kulkarni, S.S.. Ekiner, O.M. and Hasse, D.J. (2005) Method for forming of mixed matrix composite permselective fluid sepn. membrane using washed mol. sieve particles, (USA). Application US 20050230305. 

Membrane cross section. Isotropic (symmetric], integrally anisotropic (asymmetric], bi- or multilayer, thin-layer, or mixed matrix composite. 

Adams FV. Polysulfone/p-cyclodextrin polyurethane mixed-matrix composite nanofiltration membrane for water treatment. PhD Thesis, University of Johannesburg 2013. 

The distribution of fillers across the membrane is vital to determine the morphology and performance of the composite hollow fibers. Jiang et al. [91] reported that (1) the shear rate within the spinneret, (2) the die swell at the outlet of the spinneret, and (3) the elongation draw at the air-gap region were the factors affecting the filler distribution in the mixed-matrix composite hollow fibers, whereas Xiao et al. [92] observed that a high elongation draw ratio can radially displace the fillers toward the bore and shell side of the composite hollow fibers. 

Various zeolites have been studied as the dispersed phase in the mixed-matrix membranes. Zeolite performance in the zeolite/polymer mixed-matrix membrane is determined by several key characteristics including pore size, pore dimension, framework structure, chemical composition (e.g., Si/Al ratio and cations), crystal morphology and crystal (or particle) size. These characteristics of zeolites are summarized in Chapter 6. 

The geometries for asymmetric mixed-matrix membranes include flat sheets, hollow fibers and thin-fihn composites. The flat sheet asymmetric mixed-matrix membranes are formed into spirally wound modules and the hollow fiber asymmetric mixed-matrix membranes are formed into hollow fiber modules. The thin-film composite mixed-matrix membranes can be fabricated into either spirally wound or hollow fiber modules. The thin-film composite geometry of mixed-matrix membranes enables selection of different membrane materials for the support layer and low-cost production of asymmetric mixed-matrix membranes utilizing a relatively high-cost zeolite/polymer separating layer on the support layer. 

Thin-Film Composite Mixed-Matrix Membranes... 

Thin-film composite mixed-matrix membranes can be made by a coating method or by a dual-layer co-extrusion technology, as discussed in Section 11.5.2.2. 

Jia and coworkers prepared thin-film composite zeolite-filled silicone rubber membranes by a dip-coating method [82]. The membranes have a thin silicalite-1/ silicone rubber mixed-matrix selective layer on top of a porous polyetherimide support. 

The new concept of using mixed-matrix membranes with commercially attractive thin-film composite geometry for desalination of water has been demonstrated by Jeong and coworkers [83]. 

Buttal, T., Bac, N., and Yilmaz, L. (1995) Effect of feed composition on the performance of polymer-zeolite mixed matrix gas separation membranes. Sep. Sci. Technol, 30 (11), 2365-2384. 

Cross-section structure. An anisotropic membrane (also called asymmetric ) has a thin porous or nonporous selective barrier, supported mechanically by a much thicker porous substructure. This type of morphology reduces the effective thickness of the selective barrier, and the permeate flux can be enhanced without changes in selectivity. Isotropic ( symmetric ) membrane cross-sections can be found for self-supported nonporous membranes (mainly ion-exchange) and macroporous microfiltration (MF) membranes (also often used in membrane contactors [1]). The only example for an established isotropic porous membrane for molecular separations is the case of track-etched polymer films with pore diameters down to about 10 run. All the above-mentioned membranes can in principle be made from one material. In contrast to such an integrally anisotropic membrane (homogeneous with respect to composition), a thin-film composite (TFC) membrane consists of different materials for the thin selective barrier layer and the support structure. In composite membranes in general, a combination of two (or more) materials with different characteristics is used with the aim to achieve synergetic properties. Other examples besides thin-film are pore-filled or pore surface-coated composite membranes or mixed-matrix membranes [3]. 

A wide variety of polymeric membranes with different barrier properties is already available, many of them in various formats and with various dedicated specifications. The ongoing development in the field is very dynamic and focused on further increasing barrier selectivities (if possible at maximum transmembrane fluxes) and/ or improving membrane stability in order to broaden the applicability. This tailoring of membrane performance is done via various routes controlled macro-molecular synthesis (with a focus on functional polymeric architectures), development of advanced polymer blends or mixed-matrix materials, preparation of novel composite membranes and selective surface modification are the most important trends. Advanced functional polymer membranes such as stimuli-responsive [54] or molecularly imprinted polymer (MIP) membranes [55] are examples of the development of another dimension in that field. On that basis, it is expected that polymeric membranes will play a major role in process intensification in many different fields. 

Miller, S.J. et al. (December 2002) Purification of p-xylene using composite mixed matrix membranes. US Patent 6,500,233. 

Membrane materials. Organic polymers, inorganic materials (oxides, ceramics, metals], mixed matrix, or composite materials. 

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