The Change Of The Adsorption Properties
THE CHANGE OF THE ADSORPTION PROPERTIES
OF FCC CATALYSTS IN THE CATCRACKER INFERNO
K. Patrylak1, L. Patrylak1, R. Leboda2, J. Skubiszewska-Zięba2
1Institute of Bioorganic Chemistry and Petroleum Chemistry, Ukrainian National Academy of Sciences, Murmans’ka st. 1, 02094 Kyiv, Ukraine
2Department of Chemical Physics, Faculty of Chemistry, Maria Curie-Sklodowska University, Maria Curie-Sklodowska sq. 3, 20-031 Lublin, Poland
In the catcracker riser, the catalyst is deactivated by coke lay-down. Burning off this coke in the regenerator does not restore the catalytic performance completely because of substantial irreversible transformations occurred within the zeolite structure due to the high (up to 750° C) temperature and steam influence. Only high quality materials can survive these conditions.
The aim of this work was to investigate the changes of adsorption properties of FCC catalysts, which were subjected to steam-aging as simulation of real catcracker conditions.
Three (1-3) in situ synthesized and one (4) as mixing product of zeolite and matrix phases FCC samples were subjected to stabilization procedure in the pure steam flow for 2 h at 800° C using a special catalyst steamer [1]. The zeolite phase in sample 1 was represented by X type (Si/Al = 1.2-1.25), whereas in samples 2-4 – by Y type (Si/Al = 2.2-2.3).
Adsorption characteristics of the fresh and steam-aged samples were determined by means of an ASAP-2405N adsorption analyser from Micromeritics Instrument Corp., Norcross, GA, USA. Prior to nitrogen adsorption, the samples were degassed in vacuum (10-3 Torr) at 200° C.
Steaming decreases the fresh FCC catalysts microporosity dramatically (Table 1), especially in the case of samples 1 and 4. The decrease in microporosity is attributed to the crystallinity losses of the zeolite phase. Stabilization of all samples leads to increase of the average pore diameter and to both surface area and total pore volume reduction, but such a procedure seems to result in the preferential collapse of the sample 1 micropores.
The results obtained confirm extremely high sensitivity of X zeolite to the steaming (sample 1) as well as the great stabilization efficiency of the matrix towards the Y zeolite phase synthesized in situ (samples 2, 3).
Table 1. Adsorption Characteristics of Fresh and Steamed Samples
Characteristic and its
Fresh samples
Steamed samples
dimension
1
2
3
4
1
2
3
4
Surface area, m2/g
BET
Langmuir
308
386
344
431
162
202
131
163
138
175
217
272
90
112
45
57
Cumulative surface area of pores between 17 and 3000 Å diameter, m2/g
BJH (adsorption)
BJH (desorption)
204
230
204
227
48
55
26
37
160
189
181
213
41
49
23
29
Micropore area, m2/g
143
158
117
102
18
82
55
23
Cumulative pore volume of pores between 17 and 3000 Å diameter, cm3/g
BJH (adsorption)
BJH (desorption)
0.37
0.39
0.34
0.36
0.079
0.087
0.079
0.092
0.33
0.33
0.38
0.41
0.09
0.11
0.06
0.07
Micropore volume, cm3/g
0.063
0.069
0.052
0.045
0.008
0.036
0.024
0.01
Average pore diameter, Å
Langmuir
BJH (adsorption)
BJH (desorption)
41
72
68
35
66
64
24
66
63
29
122
99
90
82
70
68
84
77
39
95
87
45
108
99
Thus adsorption investigations confirm earlier conclusions about in situ zeolite stability [2, 3]. Such a stabilization of zeolite phase lies in the realization of a certain solid-state reaction between zeolite and matrix, which leads to a more significant mutual connection between them.
References
1. L. Patrylak, Adsorpt. Sci. Technol. 18 (2000) 399.
2. K.I. Patrylak, L.K. Patrylak, O.M. Taranookha, I.A. Manza, Abstracts 4th Europ. Cong. on Catalysis (EuropaCat-IV), Rimini (Italy), 1999, p. 122.
3. L.K. Patrylak, R.V. Likhniovskyi, A.V. Kukushkina, P.I. Bartosh, V.Yo. Vypyrailenko, K.I. Patrylak, Ukr. Chem. J. 66 (2000) 100 (Ukr.).
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