Highly active and stable performance of catalytic vapor phase Koch-type carbonylation of tert-butyl alcohol over H-zeolites

Article abstract of DOI:10.1039/b304353c

A high catalytic activity and excellent stability of the vapor phase Koch-type carbonylation of tert-butyl alcohol towards 2,2-dimethylpropanoic acid on a H-ZSM-5 catalyst were achieved with a yield as high as 90% without any threat of deactivation in 120 h.

Full text of DOI:10.1039/b304353c

Highly active and stable performance of catalytic vapor phase Koch-type
carbonylation of tert-butyl alcohol over H-zeolites
Tao Li, Nobuko Tsumori, Yoshie Souma and Qiang Xu*
National Institute of Advanced Industrial Science and Technology (AIST), 1-8-31 Midorigaoka, Ikeda, Osaka
563-8577, Japan. E-mail: q.xu@aist.go.jp; Fax: +81 72 751 9629; Tel: +81 72 751 9652
Received (in Cambridge, UK) 22nd April 2003, Accepted 30th June 2003
First published as an Advance Article on the web 10th July 2003
A high catalytic activity and excellent stability of the vapor
various H-type zeolites are shown in Table 1. It can be seen that
tert-butyl alcohol easily reacts on the acid catalysts. All the tert-
butyl alcohol disappears on the three H-ZSM-5 zeolites with
2 2 3
different SiO /Al O molar ratios, and only a small amount of
unreacted alcohol remained on H-Mordenite, H-Beta and H-
USY. Isobutene is formed as the main product of the
dehydration, and no ethers are formed on all the H-zeolites.
Besides isobutene, the dimer (C8) species are the second by-
products, and only traces of the trimer species are detected on
H-Mordenite and H-USY. The maximum yield of 2,2-dimethyl-
phase Koch-type carbonylation of tert-butyl alcohol towards
2
,2-dimethylpropanoic acid on a H-ZSM-5 catalyst were
achieved with a yield as high as 90% without any threat of
deactivation in 120 h.
As one of the most important tert-carboxylic acids, 2,2-dime-
thylpropanoic acid has been widely used as a starting material
for various agrochemicals, pharmaceuticals, fragrance chem-
icals, specialty chemicals and polymer additives. Since the work
reported by Koch in 1955, it has been known that tertiary
carboxylic acids can be produced by the reaction of CO with
propanoic acid is obtained on H-ZSM-5 (50) (SiO
50), and the yield of the main product decreases with increasing
SiO /Al molar ratio. The yield of 2,2-dimethylpropanoic
acid on H-ZSM-5 (50) is much higher than those on the other
three H-zeolites with similar SiO /Al molar ratios. No
2 2 3
/Al O =
alcohols or olefins and H
2
O in a strong acid medium, such as
2
2 3
O
–3
H
2
SO , HF or BF ·H
4
3
2
O under high CO pressure.1 The huge
amount of acids used for this reaction results in serious
corrosion, difficulties in product separation and disposal
problems. Although we have found that cationic metal carbonyl
catalysts enabled this reaction to proceed at room temperature
and atmosphere CO pressure,4 a strong inorganic liquid acid
medium was also inevitably employed. Therefore, the use of
more environmentally friendly solid acids as catalysts instead of
strong liquid acids would be of significant advantage. There
have been only a few reports on solid acid-catalyzed carbonyla-
tion, although solid acids have been widely used as catalysts and
2
2 3
O
significant amounts of higher carboxylic acids are observed in
the vapor phase carbonylation, probably due to the short contact
time in comparison with that during the liquid phase carbonyla-
tion, in which C9 and C13 carboxylic acids ( > 40%) along with
2,2-dimethylpropanoic acid were observed on H-Mordenite, H-
Beta and H-USY whereas only 2,2-dimethylpropanoic acid was
–8
14
formed on H-ZSM-5.
From the reaction mechanism,1
of H O facilitates the conversion of the tert-butyl acylium ion
4,15
it seems that the addition
2
9
are indispensable in many reactions. Until now, no solid acid
intermediate to 2,2-dimethylpropanoic acid. Only a slight
improvement in the yield of 2,2-dimethylpropanoic acid was
could catalyze Koch-type carbonylation to produce acceptable
yields unless the reaction was carried out at very high pressures
and temperatures, assisted by an additional corrosive Lewis acid
or operated in multiple steps.10 Recently, Stepanov et al.
reported the direct NMR observation of the Koch reaction in
achieved by the addition of H
carbonylation of tert-butyl alcohol on H-ZSM-5,14 whereas a
significant influence of H O was observed during the vapor
phase carbonylation (Table 2). The addition of an equimolar
amount of H O into the tert-butyl alcohol causes the yield of
2
O during the liquid phase
2
zeolite H-ZSM-5 at room temperature without using pressur-
2
ized conditions.1
1–13
Based on this discovery, we have suc-
2,2-dimethylpropanoic acid to increase from 8.3 to 13.5%. The
yield of 2,2-dimethylpropanoic acid reaches the highest value at
ceeded in the carbonylation of tert-butyl alcohol with CO in the
liquid phase over various H-type zeolites,14 and a selectivity for
H
O/tert-butyl alcohol (molar ratio) = 3–5. The yield of
2,2-dimethylpropanoic acid begins to decrease with further H
addition, and at the same time, a small amount of unreacted tert-
butyl alcohol appears. Obviously, the coadsorption of H O and
2
2,2-dimethylpropanoic acid as high as 100% was obtained over
2
O
H-ZSM-5. So far, no studies concerning vapor phase Koch
carbonylation have been reported. Obviously, fixed bed reactors
offer many advantages such as no use of large amounts of
organic solvent, continuity of operation, ease of product work-
up and catalyst reusability. We now report the vapor phase
carbonylation of tert-butyl alcohol with CO over H-zeolites.
The catalytic reaction of the carbonylation of tert-butyl
alcohol with CO was carried out in a high-pressure fixed-bed
continuous-flow stainless steel reactor operated in the down-
flow mode. Catalyst (2.0 g; particle size: 0.2–0.35 mm) was
placed at the center of the reactor with a pre-heating zone of
quartz sand. Prior to the reaction, the catalyst was pretreated in
dried air at 450 °C for 3 h. The reactor temperature was then
2
the tert-butyl acylium ion intermediate on the acidic sites
facilitates the formation of 2,2-dimethylpropanoic acid. On the
other hand, the addition of H O may moderate the acidity of the
2
Table 1 Carbonylation of tert-butyl alcohol over various H-type zeolitesa
Yield of
Conversion of tert-
butyl alcohol (%)
2,2-dimethylpropanoic
acid (%)
Catalystb
c
H-ZSM-5 (50)
100
100
100
94.0
96.8
98.2
8.3
2.4
0.3
4.1
3.7
1.9
lowered to the reaction temperature under flowing N
2
. After
H-ZSM-5 (300)d
H-ZSM-5 (1000)
e
thoroughly purging the catalyst with flowing CO, the reaction
pressure was maintained at a constant value using a back-
pressure regulator in the outlet of the reactor. tert-Butyl alcohol
was supplied using a microfeeder. The reaction products were
analyzed on-line by a gas chromatograph equipped with an FID.
A complete C balance was established through internal
calibration using pure standards of the main compounds
involved in the reaction.
e
H-Mordenite (20)
H-Beta (25)d
H-USY (30)d
a
Reaction conditions: catalyst = 2.0 g, reaction temp. = 200 °C, WHSV
2
1
21
of tert-butyl alcohol = 0.10 h , CO stream = 0.8 MPa, 30 ml min
SiO /Al O molar ratio in parentheses. Purchased from N. E. Chemcat
2 2 3
Corporation. Purchased from Zeolyst International. Offered by Catalysis
Society of Japan as reference catalysts.
.
b
c
d
e
The results of the reaction of tert-butyl alcohol with CO over
2
070
CHEM. COMMUN., 2003, 2070–2071
This journal is © The Royal Society of Chemistry 2003

Table 2 Influence of H
over H-ZSM5 (50)
2
O addition on the carbonylation of tert-butyl alcohol
a
Yield of
H
2
O/tert-butyl alcohol Conversion of tert-
2,2-dimethylpropanoic
acid (%)
(molar ratio)
butyl alcohol (%)
0
100
100
100
100
100
99.6
97.2
8.3
13.5
16.3
18.9
18.8
14.2
4.5
1
2
3
5
.0
.0
.0
.0
1
5
a
0.0
0.0
Fig. 1 Time-on-stream (TOS) dependence of the yield of 2,2-dimethylpro-
panoic acid catalyzed by the H-ZSM-5 (50) catalyst. (Reaction conditions:
Reaction conditions: catalyst = 2.0 g, reaction temp. = 200 °C, WHSV
of tert-butyl alcohol = 0.10 h2 , CO stream = 0.8 MPa, 30 ml min
1
21
.
catalyst = 2.0 g, reaction temp. = 200 °C, H
2
O/tert-butyl alcohol (molar
21
ratio) = 3.0, WHSV of tert-butyl alcohol = 0.10 h , CO stream = 9.0
2
1
MPa, 30 ml min .)
acidic sites on the catalyst and, therefore, depress the oligo-
merization.
A high CO pressure is also advantageous for Koch-type
carbonylation. Table 3 shows the effect of reaction pressure on
the carbonylation of tert-butyl alcohol over H-ZSM-5 (50). At
In summary, we have successfully demonstrated for the first
time that the H-ZSM-5 catalyst exhibits a very high and stable
catalytic performance for the vapor phase Koch-type carbonyla-
tion of tert-butyl alcohol to produce 2,2-dimethylpropanoic
acid. This catalytic system is more efficient and environmen-
tally friendly in comparison to any known liquid phase
carbonylation, and we believe that this advantage may extend to
other alcohols or olefins as well as being of practical
application.
0
.1 MPa CO, only a small amount of 2,2-dimethylpropanoic
acid is formed. By raising the CO pressure, the yield of
,2-dimethylpropanoic acid dramatically increased with a yield
2
as high as 90.8% at 9.0 MPa CO. This value is much higher than
the highest yield (about 60%) for liquid phase carbonylation on
the H-ZSM-5 catalyst at the same CO pressure. Fig. 1 shows the
time-on-stream (TOS) dependence of the yield of 2,2-dimethyl-
propanoic acid over H-ZSM-5 (50). Obviously, the yield of
This work was financially supported by METI and NEDO of
Japan.
2,2-dimethylpropanoic acid remains constant during the TOS
for 120 h. No threat of deactivation is observed. In addition, no
significant change in the color of the catalyst was observed after
Notes and references
120 h reaction, indicating nearly no coke built up on the catalyst
after so long on stream.
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over H-ZSM5 (50)
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,2-Di-
Dimer
(C8)
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CO
Conversion methyl-
Trimer
pressure
of tert-butyl propanoic Isobutene + species + species +
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(MPa)
alcohol (%) acid
ULP
UMP
UHP
7
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0
0
3
5
6
9
a
.1
.8
.0
.0
.5
.0
100
100
100
100
100
100
2.3
18.9
39.8
74.2
82.8
90.8
75.6
47.6
27.6
11.7
6.3
22.1
33.5
32.1
12.7
7.4
0
0
0.6
1.5
3.4
2.3
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3.2
3.7
2
Reaction conditions: catalyst = 2.0 g, reaction temp. = 200 °C, H O/tert-
21
butyl alcohol (molar ratio) = 3.0, WHSV of tert-butyl alcohol = 0.10 h
,
CO stream = 30 ml min2
1
b
.
By-products consist mainly of isobutene,
1
dimer (C8) species and trimer species together with traces of unidentified
low-weight (ULP), medium-weight (UMP) and high-weight (UHP) prod-
ucts.
1
5 N. Tsumori, Q. Xu, Y. Souma and H. Mori, J. Mol. Catal. A, 2002, 179,
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71.
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