Chemistry Reference
In-Depth Information
Fig. 9 Illustration of the pore systems in a) AFI, b) MOR and c) BEA zeolites.
Table 2 Density and strength of acid sites in zeolite catalysts reported in this contribution.
Dn(OH) (cm
1
)
upon CO adsorption
Dimensionality/
ring size
Topology (Material)
Si/Al ratio
Reference
CHA (SSZ-13)
3D/8 ring
12
314
47
TON (ZSM-22)
1D/10 ring
B
30
320
48
MEL (ZSM-11)
3D/10 ring
B
20
328
49
IMF (IM-5)
3D/10 ring
B
20
328
49
MFI (ZSM-5)
3D/10 ring
B
20
328
49
TUN (TNU-9)
3D/10 ring
B
20
328
49
332
a
MOR (Mordenite)
1D/12 ring
22
50
319
b
BEA (Beta)
3D/12 ring
19
36
AFI (SSZ-24)
1D/12 ring
35
316
51
a
Data from literature, using a material with Si/Al
=
18.
b
Data from literature, using a material with Si/Al
=
12.5.
1.3.1 Acid properties. In this work, the O-H stretch frequency of
selected materials was monitored by FTIR before and after adsorption of
a small, weakly basic probe, CO. The measured change in the O-H stretch
frequency upon CO adsorption at
196 1C was used as a measure of the
acid strength and is reported in Table 2.
2 The Methanol to Hydrocarbons (MTH) reaction
The global demand for energy and petrochemical products is increasing
and it is forecasted that crude oil reservoirs will soon be insucient to meet
the increasing demand. This situation calls for both alternative and sup-
plementary carbon sources to supply the planet with fuels and chemicals in
the future. Alternative carbon sources such as coal, natural gas, petro-
chemical residue, agricultural wastes, municipal garbage and wood etc. are
believed to be successors of the depleting crude oil in the future.
46
Even
CO
2
is considered to be a future carbon source.
52,53
Methanol is a highly
relevant chemical intermediate in this respect, because it may be produced
from practically any of the carbon sources mentioned above. The con-
version of methanol to hydrocarbons (MTH) constitutes the final step in
one conversion route of such alternative sources to value added products.
2.1 Historical development
The catalytic conversion of methanol to hydrocarbons (MTH) was
fortuitously discovered by Mobil in the 1970s.
54
Researchers at Mobil
