PREFACE
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t has been more than a quarter of a century since synthetic molecular sieve zeolites first became a commercial reality. The magnitude and importance of this new technology, as is often the case, initially grew at a modest pace by absolute standards. This growth rate exploded almost 20 years go, however, with the widespread application of these materials in petroleum cracking catalysts. Another sharp increase occurred about 10 years ago with the development of relatively sophisticated adsorptive proc esses for drying and purification in the petrochemical and natural gas industries. And now, in recent years, we have seen the emergence of large-scale uses for synthetic zeolites as ion exchangers, and the develop ment of complex high-technology systems employing these porous crystals in bulk separations of commodity-type liquids and gases.
The number of publications dealing with zeolites has grown similarly by leaps and bounds. A very rough estimation of the number of issued U.S. patents in which zeolites and their uses are disclosed rose from more than 2000 at the end of 1972 to over 5500 by the end of 1979. A similar approximation of the number of technical papers shows a rise from more than 7000 in 1972 to about 25,000 by 1980. Although a number of books now contain chapters or sections dealing with zeolites, this subject has been the primary focus in very few volumes. The most noteworthy of these is the treatise by D. W. Breck, Zeolite Mo lecular Sieves, published by Wiley in 1974. The earliest modern ones are the Russian texts on Molecular Sieves and Their Use, published by V . A . Sokolov, N . S. Torocheshnikov, and Ν . V . Kel'tsev in 1964, and S. P. Zhdanov's Chemistry of Zeolites in 1968. Other significant works include the 1976 A C S Monograph on Zeolite Chemistry and Catalysis edited by J. A . Rabo, and the volume on Zeolites and Clay Minerals as Sorbents and Molecular Sieves by R. M . Barrer, published in England in 1978. A number of conferences have now been held whose focus has been molecular sieve zeolites. The International Zeolite Association will have held the Fifth International Conference on Zeolites in Naples in June, 1980. The first such conference was organized by R. M . Barrer in London in 1967, and was followed by others in Worcester, Massachusetts in 1970, Zurich in 1973, and Chicago in 1977. Preceding these were the Ail-Union Conferences held in the USSR in 1961 and 1964; other European con ferences have included the First All-Union Conference * on Molecular Sieves in Catalysis held in Novosibirsk in 1976, the Symposium on Zeolites held in Szeged, Hungary in 1978, and the Symposium on Catalysis by ix
In Adsorption and Ion Exchange with Synthetic Zeolites; Flank, W.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.
Downloaded by UNIV OF PITTSBURGH on May 26, 2014 | http://pubs.acs.org Publication Date: August 15, 1980 | doi: 10.1021/bk-1980-0135.pr001
Zeolites to be held in Lyon in September, 1980. Also, a conference on natural zeolites was held in Tuscon, Arizona in 1976. Sessions on zeolites have become a regular feature at large technical meetings like those of the ACS and AIChE, and at smaller specialized ones like those of the Catalysis Society, the Clay Minerals Society, and the Gordon Conferences. While zeolite catalysis represents the largest application area for molecular sieve zeolites to date, and has been addressed separately in several recent symposia and books, adsorption and ion exchange with zeolites, the other major fields of application, have not been so treated. They have been considered either in conjunction with catalytic aspects, or as subsets of unit operations or materials used therein. As the number and size of applications for zeolites in these noncatalytic areas prepare to take a great leap forward, this is an appropriate time to gather together current work dealing with the principles and practice relating to adsorp tion and ion exchange applications of synthetic zeolites, and to consider them in some kind of perspective before specialized fragmentation renders such an attempt too overwhelming to contemplate. This, then, is the rationale behind the organization of this symposium. Among the principles addressed are those involving single and multicomponent adsorption modeling, mass transfer and surface diffusion in packed beds, and competitive sorption effects. A number of basic phenomena in adsorption and ion exchange are examined and discussed, including struc tural stability considerations, oxygen adsorption and energy transfer in copper-exchanged zeolite Y , and ion exchange behavior in zeolites A and Y . Applications include both simple and complex pressure-swing adsorp tion processes for bulk separations, recent advances in purification and drying, and selective separations of various types of adsorbates with some of the newer zeolites possessing high silica to alumina ratios in their framework composition. The sophistication and innovation evident in some of this work (e.g., the 1979 Kirkpatrick honors award-winning Polybed hydrogen separation process and the applications of high-silica zeolites) are indicative of the continuing growth and broad applicability of zeolites in an increasing number of fields. Thanks are due to several of my colleagues, particularly R. A . Ander son, D. W. Breck, Μ. Ν . Y . Lee, and J. D. Sherman, for helpful sugges tions and discussions in the organization of this symposium. The encour agement of the program committee of the Industrial and Engineering Chemistry Division of the ACS also is acknowledged. Finally, I want par ticularly to thank the reviewers, who contributed their valuable time and effort to the advancement of zeolite science and technology. Molecular Sieve Department Union Carbide Corporation Tarrytown, N Y April, 1980
WILLIAM H. F L A N K
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In Adsorption and Ion Exchange with Synthetic Zeolites; Flank, W.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.
