Note: Descriptions are shown in the official language in which they were submitted.
10940!99
The present inVention relates to a process for producing
diacetoxybutene from butadiene in the presence of a palladium
type catalyst. More particularly, the present invention relates
to a process for producing diacetoxybutene with improvements
of an acetoxylation system, a butadiene recovery system and a
waste gas treating system.
It is known to produce diacetoxybutene by reacting
butadiene, acetic acid and oxygen or an oxygen-containing gas
by contact in the presence of a palladium type catalyst. Various
methods have been proposed.
The active ingredients of oxygen, butadiene and acetic
- acid are included in the waste gas discharged from the acetoxyla-
tion system and in the gas discharged from a purification system
for the reaction mixture produced by the acetoxylation. When the
gases are discharged without any treatment, an economical loss
and a pollution problem are disadvantageously caused, and
accordingly, it is necessary to effectively recover the active
ingredients and to reuse them.
It is known to recover butadiene from the gases
discharged out of the systems by absorbing butadiene into acetic
acid. However, when all of the unreacted butadiene is absorbed
in one absorption tower, it is necessary to compress the feed
gas fed to the absorption tower so as to increase the pressure
or to use a large amount of acetic acid. It is relatively
difficult to compress the feed gas to recover butadiene in one
absorption tower and it is necessary to use a special compressor
such as a turbo-compressor with liquid film shaft seal. Again,
when a large amount of acetic acid is used for the absorption,
the amount of acetic acid fed with the butadiene into the reactor
is too high and it is necessary to recover acetic acid or to
separate butadiene from the acetic acid by stripping, and
accordingly, the energy required for the operation is increased.
-- 1 --
~0940~9
Accordingly, it is not advantageous to treat the gases in one
absorption tower.
When the gas discharged from the acetoxylation system
is compressed by a compressor and is recycled to the acetoxylation
system, oxygen in the gas can be effectively used. However, the
gas includes corrosive acetic acid and polymerizable butadiene
whereby a type of the compressor is limited.
The present invention provides a process for producing
diacetoxybutene with recycling active ingredients especially
butadiene and oxygen included in the waste gas to provide an
acetoxylation system of high efficiency.
The present invention also provides a process
for producing diacetoxybutene by reacting butadiene, acetic
acid and an oxygen-containing gas in the presence of a palladium
type catalyst with a carrier in high industrial efficiency.
According to the present invention there is provided
a process for producing diacetoxybuteneby reacting butadiene,
acetic acid and an oxygen source in the presence of a palladium
type catalyst supported on a carrier which compries;
reacting said compounds in an acetoxylation zone at a pressure
of 20 to 300 Kg/cm2 G. using a mixed gas of oxygen and an
inert gas as the oxygen source; subjecting the reaction mixture
to a gas-liquid separation; recycling a part of the separated
gas into the acetoxylation zone; feeding the remainder of the
separated gas into a first butadiene absorption tower to absorb
butadiene into acetic acid under a pressure of 20 to 300 Kg~cm2 G.;
distilling the separated liquid in a butadiene recovery tower
after decreasing the pressure to 0 to 20 Kg/cm2G.; feeding the
butadiene-containing gas discharged from the recovery tower
into a second butadiene absorption tower to absorb butadiene
into acetic acid under the pressure less than the pressure at
the top of the butadiene recovery tower; and recycling the
~0~4099
butadiene-containing acetic acid discharged from the flrst and
second absorption towers, to the acetoxylation zone for use
in the acetoxylation.
In one embodiment of the present invention there is
provided a process for producing diacetoxybutene by reacting
butadiene, acetic acid and an oxygen source in the presence of
a palladium type catalyst with a carrier which comprises; reacting
the compounds in an acetoxylation zone having a pressure of 20
to 300 Kg/cm2 G. using a mixed gas of oxygen and an inert gas
as the oxygen source; subjecting the reaction mixture to a
gas~ uid separation; compressing the separated gas bya turbo-
compressor with liquid film shaft seal; recycling a part of the
compressed gas to the acetoxylation zone; feeding the remainder
of the compressed gas into a first butadiene absorption tower
to absorb butadiene into acetic acid under a pressure of 20 to
300 Kg/cm2 G.; feeding the gas discharged from the butadiene
absorption tower through the shaft seal part of the compressor
into the compressor; distilling the separated liquid by a butadiene
recovery tower after decreasing the pressure to 0 to 2~ Kg/cm G.;
feeding the butadiene-containing gas discharged from the recovery
tower into a second butadiene absorption tower to absorb butadiene
into acetic acid under the pressure less than the pressure at the
top of the butadiene recovery tower; and recycling the butadiene-
containing acetic acid discharged from the first and second
absorption towers, to the acetoyxlation zone to use it in the
acetoxylation.
It is preferably to use butadiene having high purity
as the starting material in the acetoxylation. The butadiene
need not to be pure and can be one in the Industrial Standard or
one containing an inert gas such as nitrogen, argon, methane or
ethane.
-- 3 --
` 1094099
The quality of acetic acid as the starting material
is not limited but acetic acid in Japanese Industrial Standard
is satisfactorily used. From the viewpoint of the selectivity in
the acetoxylation, the water content in acetic acid is preferably
less than 20 wt.% and from the viewpoint of the material of the
~ reactor, the content of formic acid in acetic acid is preferably
- less than 1.0 wt. %. As the acetic acid source, the butadiene-
containing acetic acid obtianed by absorbing butadiene in the
first and second butadiene-absorption towers can be used as well
as fresh acetic acid. The amount of acetic acid is in a range
from stoichiometric amount to 60 moles per 1 mole of butadiene.
Oxygen is used in a form of the mixed gas of oxygen
and an inert gas such as nitrogen or argon, especially air.
It is however always necessary to prevent a formation of explosive
gas in the reactor. The concentration of oxygen in the gas fed
into the acetoxylation zone, that is the total gas of the mixed
gas and the recycled gas is usually in a range of 0.1 to 15 vol.%,
- preferably 1 to 10 vol. %, especially 3 to 6 vol. %.
The solid catalyst used in the acetoxylation is
preferably a catalyst of palladium metal alone or together with
a catalytic metal promotor selected from the group consisting
of Bi, Se, Sb, and Te which is supported on a carrier. The carrier
can be selected as desired. Suitable carriers include silica
gel, silica alumina, alumina, clay, bauxite, magnesia, diatomaceous
earth and pumice. The amounts of the catalytic metals in the
catalyst are usually 0.1 to 20 wt. % of Pd, preferably 1 to 4 wt. %
and 0.01 to 30 wt. % of the promoter catalytic metal. The
acetoxylation can be carried out by various methods and especially
in a fixed bed.
In the process of the present invention, it is necessary
to carry out the acetoxylation under a pressure of 20 to
300 Kg/cm2 G. When the pressure is slightly lower than the limit,
-- 4
109409g
the reaction velocity is not high enough to attain the industrial
advantage. From the viewpoints of the economical strength of
the reactor and the safety, it is not preferably to have a
pressure higher than 300 Kg/cm2 G. The pressure is usually
selected from the range of 40 to 150 Kg/cm G. The reaction
temperature is usually in a range of 40 to 180C preferably 60 to
120C. When the temperature is too low, enough reaction velocity
can not be attained whereas when the temperature is too high, the
disadvantageous side reactions such as a combustion of butadiene
and acetic acid, and a polymerization of butadiene are caused.
The butadiene included in the waste gases from the
acetoxylation and the treatment of the reaction mixture is
absorbed into acetic acid in the two butadiene-absorption towers
maintained in the specific pressure according to the process
of the present invention. The acetic acid used in the absorption
is not limited and can be a commercial product including acetic
acid recovered from the systems such as the acetic acid recovered
from the diacetoxybutene manufacture step or the acetic acid
formed by hydrolysis of diacetoxybutene. The butadiene-absorption
towers can be the conventional towers used for the conventional
absorption such as a packed tower, a plated tower and a spray
tower.
In the process of the present invention, the reaction
mixture formed by the acetoxylation is subjected to the gas-
liquid separation. A part of the separated gas is recycled
to the acetoxylation zone and the remainder of the gas is fed
into the first butadiene absorption tower which is operated
under a pressure higher than 20 Kg/cm2 G., preferably in the
range 20 to 300 Kg/cm2 G., especially 40 to 150 Kg/cm2 G. to
absorb butadiene into acetic acid. The operation temperature in
the first absorption tower is in the range of 10 to 50C,
preferably 20 to 40C.
1094099
The separated gas is rec~cled to the acetoxylation
zone at the rate of 5 to 200 parts peX one part of the gas fed
into the first butadiene absorption tower. Though the content
of butadiene in the separated gas ia remarkably low such as
0.3 to 1.7 vol. ~, when butadiene is absorbed into acetic
acid under the above-mentioned high pressure, the amount ofacetic
- acid can be decreased to give the economical advantage.
I The gas is separated from the reaction mixture
and the remaining liquid components are distilled after reducing
the pressure to 0 to 20 Kg/cm2 G., preferably 2 to 10 Kg/cm G.
The liquid components of the reaction mixture are distilled in
the butadiene recovery tower to distil off the dissolved
butadiene as a gas from the top of the tower. The distillation
tower is operated under a pressure of 0.05 to 4 Kg/cm2 G.,
preferably 0.2 to 1 Kgjcm2 G. The temperature at the bottom
of the distillation tower is 118 to 140C, preferably 120 to 130C.
When the distillation is carried out at higher than 140C, the
disadvantageous side reactions of the formation of the polymer
and decomposition of the product may be caused, and an expensive
anticorrosive material should be used. This is not economical.
The butadiene-containing gas discharged from the top
of the distillation tower is fed into the second butadiene
absorption tower which is operated at a pressure lower than
the pressure at the top of the distillation tower, preferably
0 to 4 Kg/cm2 G., especially 0.2 to 1 Kg/cm2 G. to absorb buta-
diene into acetic acid. The operation temperature of the second
butadiene absorption tcwer is in a range of 10 to 50C, preferably 20 to 40C.
Thecontent of butadiene in the gas discharged from the distillation
tower is high as 30 to 90 vol. % whereby even though it is
absorbed under relatively low pressure, a large amount of acetic
acid is not needed and satisfactory absorbing effect can be
attained. Butadiene absorbed into acetic acid in the two
lO9A099
butadiene absorption towers is fed into the acetoxylation zone.
The gas liquid separation for the reaction mixture of
the acetoxylation can be attained by only one separation in
certain condition, however, it can be carried out by two or
more separations in different conditions. For example, the gas
separated by thefirst gas-liquid separation followed by the
acetoxylation is subjected to the second gas-liquid separation
together with the butadiene-containing acetic acid discharged
from the first butadiene absorption tower at the temperature
of 20 to 60C lower than that ofthe first gas-liquid separation.
A part of the separated gas is fed into the acetoxylation zone
and the remainder of the separated gas is fed into the first
butadiene absorption tower. The separated liquid is fed after
reducing the pressure, with the gas discharged from the butadiene
recovery tower into the second butadiene absorption tower to
treat it as described.
In the process of the present invention, a part of the
gas separated by the gas-liquid separation of the reaction mixture
of the acetoxylation is recycled to the acetoxylation system and
remainder of the gas is fed into the first butadiene absorption
tower. In the operation, it is preferable to use a turbo-
compressor with liquid film shaft seal. In order to recycle or to
feed the gas, a compressor is generally used. But as the separa-
ted gas includes oxygen, corrosive acetic acid and a polymerizable
butadiene, in order to maintain the safety operation for a long
time, it is preferabe to prevent contact of the oxidzing gas
with a sliding part of the compressor and a moving contact part
causing trouble due to corrosion of the material, and the
clogging of the compressor when a reciprocating compressor is
used.
For the purpose, it is preferably to use a turbo-
compressor having no sliding part and moving contact part in the
`` 1094099
oxidizing gas atmosphere, i.e. an axial flow type or centrifugal
type compressor. The turbo-compressors have VariouS kinds of the
shaft seal parts. In the process of the invention, it is
preferable to use the turbo-compressor with liquid film shaft seal
which can be both side supported with bearlng ty~pe or cantilever
type. It is optimum to use the cantilever type turbo-compressor
with liquid film shaft seal.
The pressure of the gas discharged from the compressor
is preferably 2 to 8 Kg/cm2, especially 3 to S Kg/cm2 higher
than the sùcking pressure. When!the sucking pressure is in
a range of 2G to 300 Kg/cm2 G. preferably 40 to 150 Kg/cm2 G.,
the compression ratio of the recycling gas (discharge pressure
to suction pressure) may be less than l.4, preferably less than
1.2.
The turbo-compressor has lower compression ratio
for each step in comparison with the other compressors such as
a reciprocating compressor. However, the desirable compression
ratio can be easily attained by the turbo-compressor used in
the present invention. When the compression ratio is lower
than l.2, the cantilever type turbo-compressor with liquid
film shaft seal can be used in one step for compression.
A lubricant oil is usually used as the sealing liquid
for the compressor. When the gas containing a polymerizable
butadiene is compressed in the process of the invention, the
clogging of the oil is caused at the shaft seal part, if the
compressed gas is directly contacted with the sealing liquid,
such as sealing oil. Accordingly, it is necessary to prevent
the contact of the sealing oil with the compressed gas by feeding
a clean gas whichdoes not cause such trouble. Air compressed
in high pressure which is used in the acetoxylation cannot be
used as the clean gas source because of the danger of explosion.
Nitrogen is difficult to use as the clean gas because of an
" 1094099
unecon~mical disadvantage though the danger of explosion is
not considered. In the process of the present invention, a part
of the compressed recycling gas is treated with acetic acid
to remove butadiene by the absorption, and the resulting gas can
be used as the clean gas. It is preferable to directly use the
gas discharged fromthe first butadiene absorption tower. It is
unnecessary to remove the acetic acid entrained with the
discharged gas. However, when acetic acid is absorbed into
water, the corrosive property of the gas is advantageously
eliminated.
It is necessary to impart the pressure for feeding
the clean gas to be higher than the pressure at the shaft seal
part in order to feed the clean gas into the compressor. In
accordance with the process of the invention to feed the gas
discharged from the first absorption tower as the clean gas
source into the compressor, the pressure of the recycling gas
at the discharging part is several Kg/cm2 higher than the
pressure at the shaft sealing part. The discharged recycling
gas is fed into the first butadiene ab~orption tower which is
usually operated under the pressure at the discharge to about
1 Kg/cm lower than the discharge pressure. The gas discharged
from the absorption tower is fed into the compressor. When the
pressure in the absorption tower is too low below the range so
that the pressure of the discharged gas is lower than the pressure
at the shaft seal part, the discharged gas is compressed as
desired and is fed into the compressor in the process of the
invention. The gas cannot be directly fed into the discharging
part. Two steps of labyrinthes are disposed between the oil film
seal and the gas in the compressor and the suction side is
connected through a uniform pressure pipe to the middle part
between the labyrinthes. The cleaned compressed gas is fed
through the first labyrinth to the middle part between the first
~094099
labyrinth to the middle part between the first and second
labyrinthes. The gas is mixed with the gas in the compressor
leaked through the second labyrinth and the mixed gas is fed
through the uniform pressure pipe into the suction part, and
is further fed into the discharge part. It is possible to use
the restrictive rings instead of the labyrinth.
The present invention will be further illustrated
by way of the accompanying drawings in which;
Figure 1 is a flow sheet for illustrating one embodiment
of the process of the present invention.
Figure 2 is a partial enlarged view of the both
side supported with the bearing type turbo-compressor with liquid
film shaft seal and VII represents an oil film seal, VIII
designates labyrinth.
Referring to Figure 1, the reference I designates the
acetoxylation zone; II designates the gas-liquid separator;
III designates a butadiene recovery tower; IV designates the both
- side supported with bearing type turbo-compressor with liquid
film shaft seal; V designates the first butadiene absorption
tower and VI designates the second butadiene absorption tower.
The starting materials of butadiene, acetic acid and
the oxygen containing gas is fed through the conduit ~ into
the reactor (I) to complete the acetoxylation. The resulting
reaction mixture is fed through the conduit ~ into the gas-
liquid separator (II) to separate the gas from the liquid.
The separated liquid is fed through the conduit ~ into the
butadiene recovery tower (III) after reducing the pressure.
The liquid containing the main components of 1,4-diacetoxybutene
and acetic acid are discharged from the bottom of the tower
and is fed through the conduit ~ into the deacetic acid tower
(not shown) to obtain the liquid containing the main componen~
of 1,4-diacetoxybutene. The acetic acid discharged from the top
-- 10 --
1094099
of the deacetic acid tower is advantageously fed into the
butadiene absorption tower after separating water therefxom-.
The butadiene containing gas discharged from the top
of the butadiene recovery tower is fed through the conduit
into the second absorption tower (VI). Butadiene is absorbed
into acetic acid fed through the conduit ~ and the butadiene-
containing acetic acid is discharged from the bottom of the
tower and it is fed through the conduit ~ into the acetoxylation
zone. The gas discharged from the top of the tower is purged
through ~he conduit ~ out of the system. The separated
gas discharged from the gas-liquid separator ~II) is cooled
and is fed through the concuit ~ into the sucking part of the
compressor (IV). The pressurized oxidizing gas is obtained
from the discharge part.
- A part of the oxidizing gas is fed through the
conduit ~ into the first absorption tower (V) and the remainder
of the gas is fed through the part ~ into the acetoxylation zone.
In the first absorption tower, butadiene is absorbed into
acetic acid fed through the conduit ~ . The butadiene
containing acetic acid is discharged from the bottom of the tower
and it is fed through the conduit ~ into the acetoxylation zone.
When both sides supported with bearing type turbo-
compressore is used, a part of the gas discharged from the top
of the tower is recycled as the clean gas to the shaft seal part
of the compressor (IV) and the remainder of the gas is purged
together with the waste gas discharged from the top of the
second absorption tower out of the system. A half of the clean
gas is discharged together with the shaft sealing oil from
the shaft seal part of the compressor. The clean gas is
combined with the purged gas from the absorption tower and the
mixed gas is purged out of the system. It is preferable to
absorb acetic acid component in the purged gas into water before
1094099
purging it.
Figure 2 is a partial enlarged view of the both side
supported with bearing type turbo-compressor with liquid film
shaft seal (In Figure 1 (IV)) wherein the reference VII designates
an oil film seal and VIII designates a labyrinth.
A half the clean gas fed through the conduit ~ is
purged through the conduit ~ together with the sealing oil fed
through the conduit ~ out of the system. The remaining half
of the clean gas is fed into the middle part of the two steps
of the~labyrinthes and is fed together with the gas in the compressor
through the uniform pressure pipe into the suction part of the
compressor and then it is fed into the discharge part. The gas
is combined with the gas being compressed which is fed through
the conduit ~ , and through the conduit ~ , a part of the
mixed gas is fed into the first absorption tower and the remainder
of the gas is recycled to the acetoxylation zone.
In accordance with the process of the present invention,
the acetoxylation is carried out under a reaction pressure of
20 to 300 Kg/cm2 G. and two absorption towers at high pressure
and low pressure are provided whereby the gas discharged from
the butadiene recovery tower can be treated without the compression
to completely recover butadiene with acetic acid needed for the
acetoxylation. In accordance with the process of the present
invention, the recycle gas is compressed whereby the oxidizing
gas can be recycled to the acetoxylation zone in safety with
advantage.
Moreover and preferably when a part of the gas
discharged from the outlet is passed through the absorption tower
to absorb butadierieinto acetic acid and a part of the gas
discharged from the absorption tower is fed into the compressor,
the recovery of butadiene and the recovery of oxygen in the waste
gas can be simultaneously attained by one absorption tower.
1094099
The process of the present invention will be further
illustrated in detail by the following Example in which a part
means a part by weight unless otherwise specified.
Example:
Butadiene, air, recycle gas and recycle acetic acid
were respectively fed into an acetoxylation zone at 50C under
a pressure of 93 Kg/cm2 G. at the rates of 1400, 2290, 63,630 and
25,450 parts per 1 hour. The acetoxylation zone consisted of
two of reactors made of SUS 316 having an inner diameter of 1800mm
and a height of 8000mm which are connected. In each reactor,
4500 parts of a coconut shell active charcoal (4 to 6 mesh)
which supports palladium and tellurium was packed. At the output
of the acetoxylation zone, the pressure was 91 Kg/cm2 G. and
the temperature was 80C.
At the bottom of the reactor, the first gas-liquid
separation of the reaction mixture was carriedout under conditions
to obtain the liquid containing main components of 1,4-diacetoxy-
butene (13.7 wt.~) and acetic acid at a rate of 27,240 parts/hr.
and the gas containing oxygen and butadiene at a rate of 65,530
parts/hr.. The liqui-d was fed into the butadiene recovery tower
after reducing the pressure to the atmosphereic pressure. The
gas containing 20.4 wt.~ of butadiene was obtained from the top
of the butadiene recovery tower at a rate of 1,120 parts/hr.
and the bottom containing 1,4-diacetoxybutene (14.3 wt.%) and
acetic acid was obtained from the bottom of the tower at a rate
of 26.120 parts/hr.. The butadiene recovery tower was made of
SUS 316 and had an inner diameter of lOOOmm and a height of 7000mm
and had ten plates of perforated plate trays and was equipped
with a condenser and a reboiler. The operation of the recovery
tower was carried out under atmospheric pressure at the top of the
tower and a recycling ratio of 0.05. The bottom was consequently
fed into the deacetic acid tower to obtain acetic acid having a
--` 109~099
a purity of 98.5 wt.% from the top of the tower and to obtain
1,4-diacetoxybutene having a purity of 86.5 wt.% from the
bottom of the tower.
The gas discharged from the acetoxylation zone at
a rate of 65,530 parts/hr. was combined w1th the liquid contain-
ing butadiene and acetic acid as the main component which was
discharged from the first butadiene absorption tower under a
pressure of 90 Kg/cm G. at a rate of 2,470 parts/hr. and the
mixture was cooled to 45C and was separated by the second gas-
liquid separation to obtain the separate gas containing 4.95 wt. %
of oxygen and nitrogen as the main component at a rate of 65,130
parts/hr., and to obtain the separated liquid containing acetic
acid as the main component at a rate of 2870 parts/hr.
After reducing the pressure of the separated liquid
to atmospheric pressure, the liquid was fed together with the
gas discharged from the butadiene recovery tower at a rate of
1120 parts/hr. into the bottom of the second butadiene absorption
tower. Acetic acid at 35C was fed from the top tower under
atmospheric pressure at a rate of 21,970 parts/hr. to counter-
currently contact the gas with the liquid in the tower. The ,
second butadiene absorption tower was made of SUS 316 and had
an inner diameter of lOOOmm and a height of lSOOOmm. The operation
was carriedout at 35C under atmospheric pressure to obtain
the acetic acid containing butadiene from the bottom of the tower
at a rate of of 25,450 parts/hr., and to obtain the waste gas
containing 100 ppm (vol.) of butadiene from the top of the tower
at a rate of 510 parts/hr.. The waste gas was washed in a water
washing tower before discharging.
The separated gas under a pressure of gO Kg/cm2G.
obtained by the second gas-liquid separation at a rate of 64,130
parts/hr. was fed into the suction part of the turbo-compressor
with liquid film shaft seal (both sides supported with bearing
-` ~094099
type one step; 10,000 r.p.m. manufactured by Mitsubishi Heavy
Industries K.K.) to obtain the recycle gas having a higher
pressure of 96 Kg/cm2 G. from the discharge part at a
rate of 65,630 parts/hr. A part of the recycle gas at a rate
of 2,000 parts/hr. was fed into the bottom of the first butadiene
absorption tower and remainder was recycled to the acetoxylation
zone. Acetic acid at 35C was fed from the top of the absorption
tower under the pressure of 96 Kg/cm2 G. at a rate of 2,430
parts/hr. to counter-currently contact the gas with the liquid
1~ in the tower, to obtain the waste gas containing 100 ppm (vol.)
of butadiene from the top of the tower at a rate of 1,960 parts/hr.
The waste gas at a rage of 1,000 parts/hr. was divided into each
of the gas at a rate of 500 parts/hr. and was recycled as the
clean gas to the shaft seal part of the compressor. The acetic
acid containing butadiene was obtained from the bottom of the
first butadiene absorption tower at a rate of 2,470 parts/hr.
and it was recycled to the second gas-liquid separator as
described. The first butadiene absorption tower was made of
SUS 316 and had an inner diameter of 500mm and a height of
lOOOOmm. The operation was carried out at 35C under the
pressure of 96 Kg/cm G. From both the shaft seal parts of the
compressor, the clean gas was discharged at a rate of 250 parts/hr.,
respectively together with the seal oil, and it was washed with
a water washing tower before discharging it.
- 15 -
