108
M. Moliner et al. / Journal of Catalysis 254 (2008) 101–109
high Ge content, ITQ-33 remains stable provided that the or-
ganic is not removed. After calcination, it remains stable even
in the presence of moisture at high temperatures. But if the
zeolite is maintained in powder form at room temperature in
presence of moisture, it rapidly loses crystallinity. The crys-
tallinity loss is much slower in the zeolite in pelletized form.
ITQ-33 shows medium-strong acidity, similar to that presented
by 12-MR pore zeolites with the same chemical composition,
indicating that larger pore diameter does not necessarily imply
lower acid strength.
The benefits of the large pores and good acidity give ITQ-33
notable catalytic advantages for reacting bulkier molecules, as
well as giving high activities and selectivities in the synthesis
of cumene by alkylation of benzene with propylene.
Fig. 10. Propylene conversion for zeolite ITQ-33 (squares) and BETA (cir-
cles) at 398 K, 3.5 MPa, benzene/propylene = 3.5 (mol/mol) and WHSV of
−1
12 (black symbols) and 24 h (open symbols).
Table 2
Acknowledgments
Alkylation of benzene with propylene using ITQ-33 and BETA zeolites. Prod-
−1
uct selectivity (wt%) at different space velocities WHSV = 12 and 24 h at
−1
T = 398 K, P = 3.5 MPa, benzene/propylene = 3.5 mol mol , TOS = 1 h
The authors thank CICYT (MAT2003-07945-C02-01) for fi-
nancial support. M.M. thanks CSIC for an I3P fellowship. The
authors thank V. Clari for technical assistance and J. Martínez-
Triguero for the cracking experiments on Beta and UTD-1.
−1
−1
Catalyst WHSV = 12 h
WHSV = 24 h
X
S
S
S
X
S
S
S
TIPB
cumene
cumene
DIPB
TIPB
DIPB
ITQ-33 98.6 76.5
BETA 95.7 90.0
17.3
6.9
3.7
<0.1
98.7 63.8
78.2 86.9
23.0
9.0
7.8
0.7
References
Catalyst deactivation occurs when alkylation is carried out in
the presence of zeolites, due mainly to fouling or coking of
the catalyst by propylene oligomerization products. Although
commercial processes deal with this problem by combining re-
action/regeneration cycles [39], there is a need to minimize
olefin oligomerization and coking that increases catalyst life.
The special microporous structure of ITQ-33 favors the forma-
tion and diffusion of the alkylation products while reducing the
undesired propylene oligomerization. The benefits over the cat-
alyst lifetime of this new zeolite compared with Beta are very
clear, especially when space velocity is increased, as shown in
Fig. 10. Besides its high stability, ITQ-33 is highly selective
to alkylation products. The large 18-MR pores allow the for-
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propylbenzene obtained in our experimental conditions was
<100 ppm, a very good result compared with the specifica-
tions for commercial cumene processes, such as UOP Q-Max
(250–300 ppm) [43] or ENI SpA (<500 ppm) [44].
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