Polymers zeolites

Wang, H., Holmberg, B.A., and Yan, Y. (2002) Homogeneous polymer-zeolite nanocomposite membranes by incorporating dispersible template-removed zeolite nanocrystals. /. Mater. Chem.,... 

Jiang, L.Y., Chung, T.S., and Kulprathipanja, S. (2006) A novel approach to fabricate mixed matrix hollow fibers with superior intimate polymer/zeolite interface for gas separation. AIChE/., 52, 2898-2908. 

C., Tatlier, M., Erdem-Senatalar, A., Schoeman, B., and Sterte, J. (2000) Effect of zeolite particle size on the performance of polymer-zeolite mixed matrix membranes./. Membr. Sci., 175 (2), 285-288. 

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. 

The main challenge of the first separation involves development of a viable membrane. An economical highly H2 selective membrane with the ability to reject both N2 and C02 is required for this stage, and such a membrane does not yet exist. Polymer-zeolite or ceramic-zeolite hybrid membranes may provide the required... 

Tricoli V and Nannetti F. Zeolite-Nafion composites as ion conducting membrane materials. Electrochim Acta 2003 48 2625-2633. Libby B, Smyrl WH, and Cussler EL. Polymer-zeolite composite membranes for direct methanol fuel ceUs. AIChE J 2003 49 991-1001. 

Bein and coworkers investigated the formation of poly(methyl methacrylate) (PMMA) through polymerization of methyl methacrylate (MMA) in channels of microporous crystals including Na-Y, mordenite, zeolite / , and ZSM-5, and mesoporous molecular sieves such as MCM-41 and MCM-48.[83] MMA in zeolites can also polymerize as acrylonitrile does, and with an increase in the host channel size the polymerization degree is enhanced. Electron microscopic observation indicates that the polymerization reaction proceeds mainly inside the zeolite channels, because almost no polymers are observable on the external surface of the zeolite particles. This is further confirmed by the fact that the polymer/zeolite composite lacks the characteristic glass transition temperature for a bulk polymer. 

The polymer/zeolite host-guest precursor for preparation of porous carbon can also be obtained through direct contact of monomers in a carrier gas with zeolite molecular sieves followed by polymerization. For example, propylene can enter into zeolite Y under the carriage of N2 and polymerize to form polypropylene. After pyrolysis, the polypropylene undergoes carbonization, and the host zeolite framework of the carbonization product can be removed by dissolution in acids, leaving carbon material with characteristic pores.[93] However, the pore-size distribution of the porous carbons obtained through this approach is not uniform, and hence they are hardly used as molecular sieves for sieving small molecules. 

Polymer-zeolite composite membranes are also studied in rectors, either as interphase contactors in liquid phase oxidation processes [65] or for improving the properties of Nafion in fuel cells applications [66],... 

Estimation of the interphase thickness and permeability in polymer-zeolite mixed matrix membranes... 

Libby B, Smyrl WH, Cussler EL. Polymer—zeolite composite membranes for direct methanol fuel cells. AIChE J 2003 49 991-1001. 

The preparation of defect-free zeolite layers on a large scale is extremely difficult and it seems doubtful that this will ever be achieved at a competitive price. However, the combination of the superior gas selectivities of molecular sieves with the processibility of polymeric membranes has attracted many researchers. The hybrid membranes consisting of inorganic molecular sieves and polymers are often referred to as mixed-matrix membranes. The term mixed-matrix membrane has been introduced by Kulprathipanja et al. [309], who performed pioneering work in the field of polymer/zeolite hybrid membranes. Kulprathipanja showed that the CO2/H2 selectivity of cellulose acetate could be reversed by addition of silicalite. The siHcaHte-CA membrane had a CO2/H2 selectivity of 5.1, whereas the pure CA membrane exhibited a selectivity of 0.77. 

Okumus et al. (1994) developed a mixed-matrix polymer-zeolite memljrane for PV. In the preparation of these manbranes, cellulose acetate (CA) as base polymer, AC, or DMF as solvent, and 13X or 4A zeolites as fillers were used. It was observed that the addition of zeolite to the membrane matrix improved the flux value twofold with respect to its homogeneous manbranes with some loss in their selectivity. For example, for a feed concentration of 74% EtOH at SO C and 1 mmHg, the flux value for the unfilled membrane was 0.6 1/m h, and for a 30% zeolite-filled man-brane, the flux was increased to 1.33. For these cases, the selectivities were 7.76 and 5.0 for the unfilled and filled membranes, respectively. 

In that regard, several reviews have been published showing the advances of SSNMR techniques appHed to polymers, zeolites, proteins, etc. [91,92]. In this section, we summarize the advances achieved in the past decade in SSNMR applied to polymorphism on pharmaceutical compounds. 

Liquid-Phase Carbonylation. An incentive for the development of immobilized solid catalysts in liquid-phase carbonylation is to retain the chemical characteristics of the soluble industrial catalysts (6) in the Reppe reaction and reduce the problems of corrosion as well as the separation of catalyst from reaction liquor. Various supporting materials such as active carbon, polymers, zeolites, and amorphous inorganic oxides are used to immobilize homogeneous carbonylation catalysts. 

Heterogeneous catalysts based on organic acids are also used in Biginelli reactions. Several solid supports have been tried, and most of them are recyclable. These include polymers, zeolites and silica, among others. 

Suer MG, Ba N, Yilmaz L. Gas permeation characteristics of polymer-zeolite mixed-matrix membranes. J MembrSci 1994 91(l-2) 77-86. 

A wide variety of materials (polymers, zeolites, ceramics and metals) have been reported for various gas separation applieations. Polymeric membranes are the only ones whieh are extensively used. Inorganic and metallic membranes have limited applieations in the gas separations. Palladium alloy membranes have been applied for the purifieation of hydrogen and mixed metal oxide membranes have been developed for high temperature air separations by ion transport meehanism. The state-of-the-art of gas separation membrane materials is presented in a reeent review article. ... 

Several polymers other than PDMS and PVA have been examined for solid-polymer mixed-matrix pervaporation. An activated earbon-block polyether-amide mixed-matrix membrane was investigated for the separation of volatile organie eompounds (VOCs). An enhancement in both trichloroethane and water flux was noted, as well as increase in trichloroethane-water selectivity compared to the neat polymer. Zeolite-polyimide mixed-matrix membranes were explored for xylraie isomo- separation. Solid-polymer adhesion was poor, resulting in a sieve-in-a-eage morphology therefore, no separation properties that exceeded neat polymer membranes were identified. Methanol-toluene separation was successfully performed with NaX—Viton mixed-matrix membranes, though other solid-polymer combinations were attempted and failed to form an enhanced membrane. 

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