Mixed-matrix membranes gas separation

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. 

Mahajan, R., and Koros, W. J. (1999, June). Mixed matrix gas separation membranes, International Congress on Membranes, Toronto Canada. 

Sen, D., Kalipcilar, H. and Yilmaz, L. 2007. Development of polycarbonate based zeolite 4A filled mixed matrix gas separation membranes.. 7. Memh. Sci. 303(1-2) 194-203. 

Fundamental and Practical Aspects of Mixed Matrix Gas Separation Membranes... 

Hacarlioglu P, Toppare L, Yihnaz L. Polycarbonate-polypyrrole mixed-matrix gas separation membranes. J Membr Sci 2003 225(l-2) 51-62. 

Mixed matrix hollow fiber membranes made with modified HSSZ-13 zeolite in polyetherimide polymer matrix for gas separation. /. Membr. Sd., 288, 195-207. 

Ekiner, O.M. and Kulkarni, S.S. (2003) Process for making mixed matrix hollow fiber membranes for gas separation. US Patent 5,553,805. 

Most of the more recent research has focused on developing membrane materials with a better balance of selectivity and productivity (permeability) as that seems the most likely route for expanding the use of this technology. There appear to be natural upper bounds [9,10] on this tradeoff that limit the extent of improvement that can be realized by manipulating the molecular structure of the polymer used for the selective layer of high-flux membranes, at least in many cases. This has led to interest in nonpolymeric and so-called mixed-matrix materials for membrane formation [8] however, at this time, polymers remain the materials of choice for gas-separation... 

Overcoming the current limitation faced by gas separation membranes may be accommodated by introducing two classes of materials that lie between conventional polymers and the high-performance molecular sieving materials. These two classes, illustrated in Fig. 11 and Fig. 12, respectively, are (i) crosslinked polymers and (ii) blends of molecular sieving domains in polymers, usually referred to as mixed matrix materials. Such materials... 

The mixed-matrix MOF polymer membranes exhibit enhanced gas permeabilities as well as selectivities. The improved separation performance is attributed to the precisely tunable MOF porosity. Separation performances of MOF-based MMMs comparable to the best polymer membranes have been reported. MOF-based MMMs can also reach similar performance as pure MOF membranes for the... 

Nanocomposite membranes, also known as mixed matrix membranes, and FTMs are two distinguished and promising generations of gas separation membranes. 

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. 

Gas separation membranes combining the desirable gas transport properties of molecular sieving media and the attractive mechanical and low cost properties of polymers are considered. A fundamental analysis of predicted mixed matrix membrane performance based on intrinsic molecular sieve and polymer matrix gas transport properties is discussed. This assists in proper materials selection for the given gas separation. In addition, to explore the practical applications of this concept, this paper describes the experimental incorporation of 4A zeolites and carbon molecular sieves in a Matrimid matrix with subsequent characterization of the gas transport properties. There is a discrepancy between the predicted and the observed permeabilities of O2/N2 in the mixed matrix membranes. This discrepancy is analyzed. Some conclusions are drawn and directions for further investigations are given. 

In the past 25 years, relatively few attempts to increase gas separation membrane performance with dense film mixed matrices of zeolite and rubbery or glassy polymer have been reported. Table I summarizes practically all of the reported O2/N2 mixed matrix membranes. Permeabilities and permselectivities are specified as a range to encompass the various zeolite volume fractions studied. In general, an increase in permeability is observed with zeolite addition coupled with a slight increase in permselectivity. Despite the wide variety of combinations of zeolites with rubbery and glassy polymers, reported mixed matrix membranes fail to exhibit the desired O2/N2 performance increases. These failures have generally been attributed to defects between the matrix and molecular sieve domains. While this is certainly a possible practical source of failure, our work earlier 8) has addressed a more fundamental source caused by inattention to matching the transport properties of the molecular sieve and polymer matrix domains. This topic is discussed briefly prior to consideration of the practical defect issue noted above. 

Successful spinning of mixed-matrix hollow-fiber membranes for gas separation has so far been only demonstrated in apatentby Ekineret al. ° A major hurdle to the commercial implementation of mixed-matrix membranes has been the lack of reproducibility in forming successful mixed-matrix membranes. Challenges with poor polymer- sieve interaction, variability in molecular sieve transport, surface characteristics, and effects of contaminants on molecular sieve performance have been identified in dense mixed-matrix... 

While porous defects between the solid and polymer are undesirable in microporous solid-polymer gas separation membranes, the opposite is tme for ultrafiltrafion and ion exchange mixed-matrix membranes.The presence of such voids enhances membrane performance as the solid acts only in the adsorbent capacity and not as a molecular sieve as required in the case of the microporous solid. 

Zeolite/polymer mixed-matrix membranes prepared from crosslinked polymers and surface-modified zeolite particles offered both outstanding separation properties and swelling resistance for some gas and vapor separations such as purification of natural gas. Hillock and coworkers reported that crosslinked mixed-matrix membranes prepared from modified SSZ-13 zeolite and 1,3-propane diol crosslinked polyimide (6FDA-DAM-DABA) synthesized from 2,2 -feis-(3,4-dicarboxyphenyl)hexafluoropropane dianhydride, p-dimethylaminobenzylamine-and 3,5-diaminobenzoic acid displayed high CO2/CH4 selectivities of up to 47 Barrer and CO2 permeabilities of up to 89 Barrer under mixed gas testing conditions [71]. Additionally, these crosslinked mixed-matrix membranes were resistant to CO2 plasticization up to 450 psia (3100kPa). 

Gas separation processes with membranes have undergone a major evolution since the introduchon of the first membrane-based industrial hydrogen separation process about two decades ago. The development of high selectivity mixed-matrix membranes will further advance the technology of membrane gas separation processes within the next decade. 

ZeoHte/polymer mixed-matrix membranes have been studied for a number of gas separations such as separation of N2 from air [37, 73, 75, 81, 84, 85], H2 and CO2 removal from natural gas [51, 54, 69, 81, 86-88], CO2 removal from N2 [74], n-pentane/i-pentane separation ]89] and separation of H2 from CO2 [65]. But a majority of the mixed-matrix membranes that have been evaluated for gas separations are mixed-matrix dense films. 

Chung, T.S., Jiang, L.Y., li, Y., and Kulprathipanja, S. (2007) Mixed matrix membranes (MMMs) comprising organic polymers with dispersed inorganic fillers for gas separation. Prog. Polym. Sci., 32 (4), 483-507. 

Gorgojo, P., Uriel, S., Tellez, C., and Coronas,). (2008) Development of mixed matrix membranes based on zeolite Nu-6(2) for gas separation. Micropor. Mesopor. Mater., 115, (1-2), 85-92. 

Mixed matrix membranes have been prepared from ABS and activated carbons. The membranes are intended for gas separation. A random agglomeration of the carbon particles was observed. A close interfacial contact between the polymeric and filler phases was observed. This morphology between inorganic and organic phases is believed to arise from the partial compatibility of the styrene/butadi-ene chains of the ABS copolymer and the activated carbon structure. A good permeability and selectivity for mixtures of carbon dioxide and methane has been reported (91,92). 

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