Chemistry Reference
In-Depth Information
Table 6.7
Initial reaction rates for Nafion
®
resin/silica-catalysed reactions in the liquid phase
Rate
Conversion
a
(%)
Reaction
Type 1 (via alkoxide route)
Type 2 (via silicate route)
Benzene/dodecene alkylation (a)
32
430
99
Transalkylation (d)
1100
30
8
6
9
8
Benzene propylation (c)
46
2
8
9
30
Freidel-Crafts acylation (b)
200
900
8
0
1-Dodecene isomerisation (e)
12
8
0
15
8
0
99
AMS dimerisation (f)
6500
19
8
0
9
8
Hydroperoxide decomposition (g)
1750
1040
99
a
Conversions shown are found using the optimum catalyst (typically 5 wt.% loading) according to the following conditions: (a)
at
8
0°C from benzene (21.5 g) alkylation with 1-dodecene (10 g) using 2 g of catalyst after 2 h of reaction time; (b) acylation of
m
-
xylene (21 g) with benzoyl chloride (10 g) at 140°C after 2 h with 1 g of catalyst; (c) benzene alkylation with propene at 70°C (using
a 20-g solution of benzene saturated in bubbling propene) with 1 g of catalyst after 1 h of reaction time; (d)
t
-butyl-
p
-cresol (10 g)
with toluene (30 g) with 1 g of catalyst at 115°C after 1 h of reaction time; (e) 1-dodecene (25 g) at
8
0°C with 1 g of catalyst after
1 h of reaction time; (f) alphamethylstyrene dimerisation (6 g of AMS in 54 g of cumene as solvent, 0.5 g of catalyst added) at
50°C after 20 min of reaction time; (g) decomposition of cumene hydroperoxide (35 g) with 0.1 g of catalyst at 50°C to form
phenol and acetone after 1 h of reaction time.
alytic activity of a number of industrially important
reactions by tailoring the microstructure.
Butene/isobutane
4.3 Haldor-Topsoe alkylation process to
high-octane fuels
One of the most important reactions in the petro-
leum industry is the 1-butene alkylation of isobu-
tane. Isobutane is one of the key ingredients and
every gallon of petrol we use contains about 10-15%
of the alkylate isooctane from this reaction. The
reaction is catalysed using either HF or sulfuric acid.
The total catalyst sales are about $600M per year.
This reaction has been studied intensively in both
industry and academia due to its enormous impor-
tance. New processing routes have been explored
because there is a drive to replace the HF or sulfuric
acid. The HF is hazardous and sulfuric acid is more
costly (the cost of the catalyst is higher per barrel of
alkylate than HF) and there is a lack of infrastruc-
ture in some areas.
The ideal catalyst would most likely be a solid acid
catalyst but over many years and numerous studies
no suitable catalyst has been identified. The main
problem is that the solid acid catalysts, although
being very active at the beginning, die quickly and
the reactivity is very short-lived. Haldor-Topsoe have
developed a new fixed-bed alkylation technology by
applying a supported liquid superacid (triflic acid) in
Moving bed of
CF
3
SO
3
H
SiO
2
Octanes
Fig. 6.
8
Supported liquid acid.
a moveable catalyst zone. The reactor system is
shown in Fig. 6.8.
In a typical process a mixture of 1-butene and
isobutane is fed into a bed of the catalyst. The homo-
geneous acid moves slowly down the column. Ex-
cellent alkylation chemistry is found, with 100%
conversion to the desired alkylates (up to 80%
