Zeolite-containing Microspheres On The Basis
ZEOLITE-CONTAINING MICROSPHERES ON THE BASIS
OF UKRAINIAN KAOLIN – THEIR ADSORPTION
AND CATALYTIC PROPERTIES
K. Patrylak1, R. Likhnyovskyi1, L. Patrylak1, V. Vypyraylenko1,
R. Leboda2, J. Skubiszewska-Zięba2
1Institute of Bioorganic Chemistry and Petrochemistry of National Academy of Sciences of Ukraine; 1, Murmans’ka vul., Kyiv, 02094 Ukraine
2Department of Chemical Physics, Faculty of Chemistry, Maria Curie-Sklodowska University; 20031 Lublin, Poland
An attempt of development of microspheric zeolite-containing cracking catalyst on the basis of Ukrainian (Prosyana deposit) kaolin has been undertaken. The technology consists in the kaolin microspheres (MS) (50-100 mcm) formation by spray-drying of kaolin suspension, in the transformation of MS formed to the Y-zeolite-containing MS (ZCMS) by in situ synthesis of the Y zeolite on account of the kaolin components, and, finally, in the activation of ZCMS by the ion exchange coupled with thermotreating procedures. To control the technology properly, not only the catalysts in their end forms are studied, but the intermediate compounds of each stage are investigated too.
The present paper deals with the adsorption and catalytic investigations of ZCMS of 39 wt % Y zeolite (Si/Al=2.25) content.
The kaolin MS formation and the following ZCMS preparation were carried out according to [1], for the adsorption and catalytic studies the low temperature nitrogen adsorption (77.4 K) and cumene cracking pulse microcatalytic [1, 2] methods were used.
The obtained ZCMS sample is characterized by relatively high total surface area: 498.7 and 620.3 sq.m/g according to BET and Langmuir methods respectively. These values show that the zeolite content, as being equal to 39 wt % (X-ray measurements [1]), is rather understated approximately by 10-15 wt %, especially as the micropore area is estimated as 359.1 sq.m/g. In accordance with the starting zeolite content, the ZCMS prepared may be classified as such one which belongs to the third, up-to-date cracking catalyst
generation [3]. The high BJH cumulative adsorption and desorption surface areas of pores between 17 and 300 Е in diameter (176.5 and 195.9 sq.m/g respectively) evidence the great part of transport pores. The last is confirmed also by high BJH cumulative adsorption and desorption volumes of pores between the above diameters – 0.322 and 0.340 cc/g respectively, whereas the micropore volume (0.158 cc/g) is approximately half the above volumes.
In general, the ZCMS, before the above mentioned activation, is of very low catalytic activity. Nevertheless, the last is of interest because of eventual unexpected features.
The testing was performed at 320 0C, liquid cumene being injected gradually (10-15 pulses) into the stream of heated helium at the reactor inlet.
The cumene of the first pulse is adsorbed practically entirely by sample. The further pulses of cumene do not display any signs of the cracking of the last: gradually enhances only its overshoot. But an interesting picture is exhibited on the reactor temperature increase to 450-500 0С, after the appearance of the cumene peak of the last pulse of cumene, – one receives the whole series of products: propene, benzene, toluene, non-converted cumene, n-propylbenzene. The ehtylbenzene absence in this row is the greatest surprise.
The toluene formation takes place through the preliminary cumene isomerization to the n-propylbenzene as a result of presence of the chemisorbed at 320 0C cumene on the catalyst surface during several first hours or in the consequence of the catalyst bed heating to 450 0C. At the same time the strength of the NaY acid sites is obviously insufficient for the isopropyl radical tertiary C-atom protonation with the successive formation of the ethylbenzene, which accompanies usual the above cracking products [2].
Therefore, on the basis of Ukrainian kaolin one manages to obtain the zeolite-containing microspheres of the proper adsorption characteristics. Being non-activated, the microspheres show only low catalytic activity, but the distribution of cumene cracking products is of certain originality.
References
1. Patrylak K.I., Nazarok V.I., Patrylak L.K., et al. J.Appl.Chem. (Russia), 72 (3), 798 (1999).
2. Patrylak L. Adsorpt. Sci. Technolog., 18 (5), (2000).
3. Avidan A.A. Akzo Catalysts Symposium 1991. Fluid Catalytic Cracking. Ed. B. van Keulen. Amersfort, The Netherlands; Akzo Chem. Div., 1991, 43.
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