Characterization of zeolites

Characterization of zeolites is primarily carried out to assess tire quality of materials obtained from syntliesis and postsyntlietic modifications. Secondly, it facilitates tire understanding of tire relation between physical and chemical properties of zeolites and tlieir behaviour in certain applications. For tliis task, especially, in situ characterization metliods have become increasingly more important, tliat is, techniques which probe tire zeolite under actual process conditions. 

Karge FI G, Flunger M and Beyer FI K 1999 Characterization of zeolites—infrared and nuclear magnetic resonance spectroscopy and x-ray diffraction Catalysis and Zeolites, Fundamentals and Applications ed J Weitkamp and L... 

The Future and Impact of Quantum Mechanical Calculations in the Description and Characterization of Zeolites... 

The currently available quantum chemical computational methods and computer programs have not been utilized to their potential in elucidating the electronic origin of zeolite properties. As more and more physico-chemical methods are used successfully for the description and characterization of zeolites, (e.g. (42-45)), more questions will also arise where computational quantum chemistry may have a useful contribution towards the answer, e.g. in connection with combined approaches where zeolites and metal-metal bonded systems (e.g. (46,47)) are used in combination. The spectacular recent and projected future improvements in computer technology are bound to enlarge the scope of quantum chemical studies on zeolites. Detailed studies on optimum intercavity locations for a variety of molecules, and calculations on conformation analysis and reaction mechanism in zeolite cavities are among the promises what an extrapolation of current developments in computational quantum chemistry and computer technology holds out for zeolite chemistry. 

Combined Physical Techniques in the Characterization of Zeolite ZSM-5 and ZSM-11 Acidity and Basicity... 

Wang, J., Feng, S., and Xu, R. (1989) Synthesis and characterization of zeolitic microporous alumino-borates, in Zeolites Facts, Figures, Future (eds P.A. Jacobs, and R.A. van Santen), Stud. Surf. Sd. Catak, vol. 49A, Elsevier, Amsterdam, pp. 143-150. 

Bu, X., Feng, P and Stucky, G.D. (1997) Science, 278 (5346), 2080-2085 Feng, P Bu, X., and Stucky, G.D. (1997) Hydrothermal syntheses and structural characterization of zeolite analogue compounds based on cobalt phosphate. Nature, 388, 735-741 Feng, P Bu, X., Gier, T.E., and Stucky, G.D. (1998) Amine-directed syntheses and crystal structures of phosphate-based zeolite analogs. Microp. Mesoporous Mater., 23 (3-4), 221-229. 

X-Ray powder diffraction is a powerful tool for characterization of zeolites. The basic experiment is relatively easy to perform and can be done in most labs on standard diffractometers and the data obtained is easy to analyze for many applications. Powder diffraction can be used to determine whether a new zeolite has been synthesized, whether a desired zeolite has been made or whether a crystallization process has completed. As noted in Section 4.2, X-ray powder diffraction can be an integral tool in determining the details of the structure of a newly synthesized zeolite. In addition, it is a critical characterization technique that can be routinely used, for example, to identify contaminants present in a synthesis, to determine how much zeolite has been bound into a catalyst or adsorbent pellet, or to ascertain if heat treatment alters the zeolite structure. Of the techniques described in this chapter, powder diffraction is probably the most commonly used. Additional details can be found elsewhere [15-19]. 

Infrared spectroscopy has proven to be a very informative and powerful technique for the characterization of zeolitic materials. Most infrared spectrometers measure the absorption of radiation in the mid-infrared region of the electromagnetic spectrum (4000-400 cm or 2.5-25 xm). In this region of the spectrum, absorption is due to various vibrational modes in the sample. Analysis of these vibrational absorption bands provides information about the chemical species present. This includes information about the structure of the zeolite as well as other functional... 

Infrared Spectroscopy Characterization of Zeolitic Systems 129 Bronsted Acid Site Distribution... 

Lok, B.M., Marcus, K.K., and AngeU, C.L (1986) Characterization of zeolite addity. 11. Measurement of zeolite acidity by ammonia temperature programmed desorption and FTIR spectroscopy techniques. Zeolites, 6, 185-194. 

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