Zeolite volume

RESINS + ZEOLITES - Volume produced 34.1 m. Cemented in 670 drums of 220 1... 

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. 

Gottardi, G. and Galli, E. aNatural Zeolites, Volume 18, Minerals and Rocks (1987), Springer-Veriag, Berlin... 

Volume 5 Catalysis by Zeolites. Proceedings of an International Symposium, Ecully (Lyon),... 

Volume 12 Metal Microstructures in Zeolites. Preparation - Properties -Applications. Proceedings of a Workshop, Bremen, September 22-24,1982 edited by P.A. Jacobs, N.l. Jaeger, P. Jitu and G. Schulz-Ekloff... 

Volume 24 Zeolites Synthesis, Structure, Technology and Application. Proceedings of an... 

Volu me 28 New Developments in Zeolite Science and Technology. Proceedings of the 7th International Zeolite Conference, Tokyo, August 17-22,1986 edited by Y. Murakami, A. lijima and J.W. Ward Volume 29 Metal Clusters in Catalysis... 

Volume 33 Synthesisof High-silica Aluminosilicate Zeolites edited by P.A. Jacobs and J.A. Martens... 

Volume 48 Structure and Reactivity of Surfaces. Proceedings of a European Conference, Trieste, September 13-16, 1988 edited by C. Morterra, A. Zecchina and G. Costa Volume 49 Zeolites Facts, Figures, Future. Proceedings of the 8th International Zeolite Conference, Amsterdam, July 10-14,1989. Parts A and B edited by P.A. Jacobs and R.A. van Santen... 

Proceedingsof the Annual International AlChE Meeting, Washington, DC, November 27-December 2, 1988 edited by M.L. Occelli and R.G. Anthony Volume 51 NewSolid Acids and Bases. Their Catalytic Properties by K. Tanabe, M. Misono, Y. Ono and H. Hattori Volume 52 Recent Advances in Zeolite Science. Proceedings of the 1989 Meeting of the British Zeolite Association, Cambridge, April 17-19,1989 edited by J. Klinowsky and P.J. Barrie... 

Volume 65 Catalysis and Adsorption by Zeolites. Proceedings of ZEOCAT 90, Leipzig,... 

Volume 83 Zeoli tes and Microporous Crystals. Proceedings of the International Symposium on Zeolites and Microporous Crystals, Nagoya, Japan, August 22-25,1993 edited by T. Hattori and T. Yashima... 

Volume 84 Zeolites and Related Microporous Materials State of the Art 1994. 

Proceedings ofthe 10th International Zeolite Conference, Garmisch-Partenkirchen, Germany, July 17-22,1994 edited by J. Weitkamp, H.G. Karge, H. Pfeifer and W. Holderich Volume 85 Advanced Zeolite Science and Applications... 

Volume 97 Zeolites A Refined Tool for Designing Catalytic Sites. Proceedings of... 

Volume 104 Equilibria and Dynamics of Gas Adsorption on Heterogeneous Solid Surfaces edited by W. Rudzihski, W.A. Steele and G. Zgrablich Volume 105 Progress in Zeolite and Microporous Materials... 

Presently, the most successful adsorbents arc microporous carbons, but there is considerable interest in other possible adsorbents, mainly porous polymers, silica based xerogels or zeolite type materials. Regardless of the type of material, the above principles still apply to achieving a satisfactory storage capacity. The limiting storage uptake will be directly proportional to the accessible micropore volume per volume of storage capacity. 

Mcntasty el al. [35] and others [13, 36] have measured methane uptakes on zeolites. These materials, such as the 4A, 5A and 13X zeolites, have methane uptakes which are lower than would be predicted using the above relationship. This suggests that either the zeolite cavity is more attractive to 77 K nitrogen than a carbon pore, or methane at 298 K, 3.4 MPa, is attracted more to a carbon pore than a zeolite. The latter proposition is supported by the modeling of Cracknel et al. [37, 38], who show that methane densities in silica cavities will be lower than for the equivalent size parallel slit shaped pore of their model carbon. Results reported by Ventura [39] for silica xerogels lead to a similar conclusion. Thus, porous silica adsorbents with equivalent nitrogen derived micropore volumes to carbons adsorb and deliver less methane. For delivery of 150 V./V a silica based adsorbent would requne a micropore volume in excess of 0.70 ml per ml of packed vessel volume. 

With lower heat-flux ratings and higher ratios of internal water volume to heating surface than is the norm today, complex external treatment was not always necessary where deemed necessary, it was often limited to basic sedimentaion or filtration techniques employing inorganic coagulants and flocculants, typically followed by the use of natural zeolites (see sections 9.2.3.1 and 9.2.5 for additional information). 

A second option is to apply the membrane on the particle level (millimeter scale) by coating catalyst particles with a selective layer. As a third option, application at the microlevel (submicrometer scale) is distinguished. This option encompasses, for example, zeolite-coated crystals or active clusters (e.g., metal nanoparticles). Advantages of the latter two ways of application are that there are no sealing issues, it is easy to scale-up, the membrane area is large per unit volume, and, if there is a defect in the membrane, this will have a very limited effect on the overall reactor performance. Because of these advantages, it is believed that using a zeolite... 

The following are some of the reasons that microreactors can be be used (i) reduced mass and heat transfer limitations, (ii) high area to volume ratio, (iii) safer operation, and (iv) ease of seating up by numbering out. The advantages of scaling down zeolite membranes are that it could be easier to create defect-free membranes and... 

The application of zeolite membranes in microreactors is still in an early stage of development, and suffers sometimes from unexpected problems arising from template removal [70]. However, several application examples of zeolite membranes in microstructured devices have been demonstrated yielding similar advantages as were to be expected from experiences on the macroscale. Because of the high surface to volume ratio of microreactors, the application of zeolite membranes in these systems has great potential. 

Although hollow fibers are thought to be an excellent candidate to be used as support-they are cheap and have a very high surface area to volume (>1000 m m ) - very few reports on hollow-fiber-supported zeolite membranes exist in the open literature. For zeohte membranes, ceramic hollow fibers are preferred because of their mechanical and thermal stability. Recently, Alshebani... 

Zeolite A is by far the most widely produced synthetic zeolite, with an annual production of some 1.3 million tonnes. As may be expected from this large volume its main use is not as a catalyst but as a detergent builder (Box 4.2). Since about 1970 the use of zeolite catalysts has provided huge economic and environmental benefits to the bulk chemical and petroleum refining industries. 

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