The Studies Of Adsorption And Porosity Properties
THE STUDIES OF ADSORPTION AND POROSITY PROPERTIES
OF NATURAL ZEOLITE SAMPLES BY MEANS OF THERMAL ANALYSIS AND SORPTOMETRIC METHODS
P. Staszczuk1, V. O. Vasylechko2, T. Danielkiewicz1, M. Matyjewicz1
1Maria Curie-Sklodowska University, Chemistry Faculty
M. Curie-Sklodowska Sq. 3, 20-031 Lublin, Poland
2Ivan Franco National University of L’viv, Department of Analytical Chemistry Kyrila & Mephodiya Str. 6, 79005 Lviv, Ukraine
The natural zeolites were know in ancient Egypt as building material. Zeolites story started in the 18th cetaury. In 1756 the Swedish mineralogist, amateur, A.F. von Cronstedt discovered and called them zeolites which in Greek means boiling stones. Till now, there have been discovered over 40 types of natural zeolites and synthetic zeolites and molecular sieves (e.g. MCM-41) [1,2,3] production exceeds 100 generations, but most of them do not have equivalents in nature. The natural and synthetic zeolites and molecular sieves have already been used to obtain adsorbents [4] and catalysts for practical application in different technology processes for example of ethylene and propylene production from methanol [5].
The quasi-isothermal technique of the thermal analysis and sorptometric methods have been used to obtain important information on the heterogeneous properties, adsorbed liquid films and liquid-solid interactions of the natural modenite and clinoptilolite samples. The measurements of the programmed thermodesorption of polar (water, n-butanol) and nonpolar (benzene, n-octane) liquids from zeolite-clinoptilolite and zeolite-mordenite samples (from Sokyrnytsa and Lypcha, Ukrainian Transcarpathian region [6,7]) were made using the simultaneous derivatograph Q-1500D (MOM Hungary). In the studies of liquids thermodesorption process the zeolite samples were wetted with liquid vapors in a vacuum desiccator where the relative vapor pressure p/po was 1. The Q-TG mass loss and the first derivative Q-DTG mass loss with respect to temperature and time were registered [8,9]. Moreover, porosity of samples were estimated by means of nitrogen adsorption at 77.4 K, with the
BET and BHJ equations employed using a sorptomat apparatus of the type ASAP 2405 V1.01 (Micrometrics Inc., USA).
From obtained data it follows that steps and/or inflections of the thermodesorption process, i.e. evaporation of liquids from capillary tubes, pores, windows and active centers of zeolite surfaces were obtained. It is worth noting that the Q-DTG curves are characterized by high selectivity and resolving power distribution. It can be considered as certain type of ?spectrum’ of thermodesorption process describing an energetic state of liquid molecules on the surface and reflecting the distribution function of desorption energy of liquid adsorbed on surface and pore-size distribution function i.e. total heterogeneity properties of tested sample [10]. On the basis of the obtained sorptometric data specific surface area, pore volume and radius as well as pore-size distribution functions were calculated, compared with analogous one from thermogravimetry data and good correlation was obtained.
It can be stated that it is possible to obtain from one simple experiment important information concerning surface capacity (thickness and volume of adsorbed films) and wetting phenomena, nature of active centres, discontinuous change of adsorption layer properties, mechanism of surface film destruction, kinetic thermodesorption of films and its stability. The method presented is very quick and convenient in studies of surface heterogeneity with respect to different adsorbates. Moreover, it is possible to study the effect of heterogeneity by chemical modification of sorbents on the wettability of solids and formation of liquid films [4]. Using experimental thermogravimetry adsorption and porosity parameters i.e. total heterogeneity [10] of the tested materials can be studied and compared with analogous ones obtained by classical techniques.
References
1. K. Korzan (1996), T. Danielkiewicz (1997), J. Kołodziejczyk (1998), M. Kaszak (1999), M. Sc. Thesis, UMCS, Chemistry Faculty, Department of Physicochemistry of Solid Surfaces, Lublin.
2. P. Staszczuk, J. Klinowski, T. Danielkiewicz, in: Program and Abstract: 27th Internat. Vacuum Microbalance Techniques Conference, (P. Staszczuk, Ed.), UMCS Lublin, 1997, p. 92.
3. P. Staszczuk, T. Danielkiewicz, Report, Chemistry Faculty, Maria Curie-Sklodowska University, 1998, pp. 79-80; 1999, pp. 65-66.
4. P. Staszczuk, T. Danielkiewicz, M. Majdan, M. Kowalska-Ternes, The Investigations of Adsorption and Porosity Properties of Pure and Modified Zeolite Samples Using Thermal Analysis and Sorptometric Methods,
1. in: Proceedings: 2nd West Ukrainian Symposium in Adsorption and Chromatography, June 5-7, 2000, L’viv, Ukraine.
5. P. Staszczuk, T. Danielkiewicz, J, Klinowski, Adsorption Sci. & Technology, accepted for publication.
6. V.O. Vasylechko, G.V. Gryshchouk, L.O. Lebedynets, Yu.B. Kuz’ma, L.O. Vasyletchko, V.P. Zakordonskiy, Adsorption Sci. & Technology, 17, 1999, 125.
7. V.O. Vasylechko, L.O. Lebedynets, L.O. Vasylechko, G.V. Gryshchouk, Yu.B. Kuz’ma, T.M. Bernats’ka, Adsorption Sci. & Technology, 14, 1996, 267.
8. P. Staszczuk, J. Thermal Anal. and Cal., 53, 1998, 597.
9. P. Staszczuk, D. Głażewski, J. Thermal Anal. and Cal., 55, 1999, 467.
10. V.I. Bogillo, P. Staszczuk, J. Thermal Anal. and Cal., 55, 1999, 483.
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