Chemistry Reference
In-Depth Information
Fig. 7 Illustration of the pore system in a) TON b) MTT c) MWW and d) EUO zeolites.
Fig. 8 Illustration of the pore systems in a) TUN, b) IMF, c) MFI and d) MEL zeolites.
measuring 5.2
4.5 Å.
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MTT and EUO zeolites have 10-ring channels
slightly narrower than the pores in TON. However unlike TON, these
zeolites contain very large 12-ring pore extensions (12-ring side pockets).
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Figure 8 displays the pore systems of three-dimensional 10-ring zeo-
lites TUN, IMF, MFI and MEL. TUN consists of two differently sized
channel systems with channel dimensions 6.0
5.2 Å and 5.4
5.5 Å,
respectively. The smaller channels have full 2D connectivity and the
bigger channels provide connections between these 2-dimensional
sheets, thus forming a 3D channel system. The TUN topology consists of
large intersections where one of the 10-rings is expanded to a 12-ring.
IMF is a 10-ring zeolite consisting of two interconnected 2D channel
systems, thus providing limited 3D connectivity. The larger 2D channel
system has channel diameters 5.5
5.6 Å and 5.3
5.4 Å, and the smaller
one has channel diameters 4.8
5.4 Å and 5.1
5.3 Å. These two channel
systems are connected by a channel with diameter 5.3
5.9 Å. A side
pocket in one of the channels leads to an extended channel intersection
volume. Slabs of three 2D channel systems are separated by a dense
framework, thus forming limited 3-dimensionality. MFI has a pore sys-
tem made from interconnecting straight and sinusoidal 10-ring chan-
nels. The straight and sinusoidal channels have dimensions 5.1
5.5 Å
and 5.3
5.6 Å respectively. MEL has channels with diameter 5.3
5.4 Å
in two directions, and 3-dimensionality is created at the interface
between two perpendicular, slightly shifted straight channels.
Figure 9 displays the pore systems of 12-ring zeolites, AFI, MOR and
BEA. AFI has a cylindrical straight one-dimensional pore system. MOR is
a one-dimensional 12-ring zeolite. The material has 8-ring pores limited
by apertures of 5.7
2.6 Å between the 12-ring channels. In practice,
these 8-rings are not accessible to diffusion species, and the channel
structure is best described as a one-dimensional 12-ring channel with
side pockets. BEA is a disordered three-dimensional large pore zeolite
consisting of 12-ring pores of dimensions 7.3
7.1 Å and 5.6
5.6 Å.
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