JPS6215059B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing diacetoxybutene from butadiene in the presence of a palladium-based catalyst.

Specifically, the present invention provides an improved method for advantageously producing diacetoxybutene by streamlining the acetoxylation reaction system, butadiene recovery system, and exhaust gas treatment system.

In the production of diacetoxybutene by catalytic reaction of butadiene, acetic acid, and oxygen or oxygen-containing gas in the presence of a palladium-based catalyst, in the exhaust gas from the acetoxylation reaction process or the gas released from the purification system of the acetoxylation reaction product. A method for advantageously recycling the active ingredients contained in
Already known in 151115. However, in such a method, it is difficult to avoid the occurrence of butadiene polymer adhesion to the equipment, corrosion of the equipment, etc. in the purification system, especially in the butadiene recovery tower.
In industrial-scale operations, prevention of such troubles has become a serious issue in terms of economy and safety.

The inventors of the present invention have intensively investigated the operational problems in the butadiene recovery tower, especially methods for suppressing the polymerization of butadiene, and have recognized that oxygen-containing gas has the effect of suppressing the polymerization of butadiene. The present invention has been completed based on the discovery that by introducing this, it is possible to suppress the polymerization of butadiene very effectively and to operate under mild conditions.

That is, in the present invention, when producing diacetoxybutene by reacting butadiene, an oxygen-containing gas, and acetic acid in an acetoxylation reaction zone under pressure in the presence of a supported palladium catalyst, the reaction product obtained from the acetoxy reaction zone is Gas and liquid are separated, a part of the separated gas is supplied to the reaction zone, the remainder is supplied to the first butadiene absorption tower to absorb butadiene in acetic acid, and on the other hand, the separated liquid is supplied to the butadiene recovery tower after pressure reduction, At the same time, an oxygen-containing gas is supplied to the recovery tower, and the butadiene-containing gas distilled from the tower is supplied to a second butadiene absorption tower to absorb butadiene into acetic acid, which then flows out from the bottom of the first and second butadiene absorption towers. The present invention relates to a method for producing diacetoxybutene, which comprises supplying acetic acid containing butadiene to an acetoxylation reaction zone.

Next, the present invention will be explained in more detail.

It is desirable that the raw material butadiene used in this reaction be of high purity, but it does not necessarily have to be pure.
It may contain an inert gas such as argon, methane, or ethane. Acetic acid, which is another raw material for the reaction, is not particularly limited and is sufficient in terms of quality as long as it satisfies JST standards.However, when considering the selectivity of the reaction, the water content must be 20% (by weight) or less. It is desirable that the amount of formic acid contained in acetic acid be 1.0% (by weight) or less from the viewpoint of the material of the reactor. As a source of acetic acid, not only fresh acetic acid but also acetic acid which has absorbed butadiene in the first and second butadiene absorption towers according to the method of the present invention can be used. The amount of acetic acid used is within the range of stoichiometric or more and 60 mol or less per 1 mol of butadiene.

The oxygen used in the acetoxylation reaction is used as an oxygen-containing gas, but it is preferably diluted with an inert gas such as nitrogen or argon, and air is preferably used. In any case, it is necessary to ensure that virtually no explosive mixture is formed in the reactor; the oxygen concentration in the oxygen-containing gas is usually between 0.1 and 15% (by volume), preferably between 1 and 10% (by volume). selected within the range.

As the solid catalyst used in this reaction, a catalyst in which palladium metal alone or palladium metal and at least one promoter metal selected from bismuth, selenium, antimony, and tellurium is supported on a carrier is suitable. Any carrier can be selected as this catalyst carrier, but specifically, activated carbon, silica gel,
Examples include silica alumina, alumina, clay, bauxite, magnesia, diatomaceous earth, and pumice.

The amount of catalyst metal supported in the catalyst is usually 0.1 to 20% (by weight) for palladium metal, and for other promoter metals.
Selected in the range of 0.01 to 30% (by weight). The reaction is
Although it can be carried out in various ways, it is preferably carried out in a fixed bed.

The acetoxylation reaction needs to be carried out at a pressure of 20 kg/cm ² G or higher. If the pressure is too low and exceeds this pressure, a sufficient reaction rate cannot be obtained and this is not preferred industrially. In addition, if it exceeds 300 Kg/cm ² G, it is not preferable from the viewpoint of pressure resistance and safety of the device, and it is usually selected from the range of 40 to 150 Kg/cm ² G.

The reaction temperature is usually 40-180℃, preferably 60-120℃
Selected from the range of °C.

In the method of the present invention, the reaction product obtained in the acetoxylation reaction is separated into gas and liquid, a part of the separated gas obtained is circulated to the acetoxylation reaction zone, and the remainder is 20 kg/cm ² G or more, preferably 20~300, Kg/ ^cm2
G is more preferably fed to a first butadiene absorption tower operated at a pressure of 40 to 150 kg/cm ² G to absorb butadiene with acetic acid. The operating temperature of the first absorption tower is 10-50°C, preferably 20-40°C.

On the other hand, the reaction product liquid after separating the pre-gas is
After decompression, 0-20Kg/cm ² G, preferably 0.05-10
It is fed to a butadiene recovery column operated at a pressure of Kg/cm ² G, more preferably 0.05 to 4 Kg/cm ² G, and the dissolved butadiene is distilled off from the top of the column in gaseous form by distillation or diffusion.

At this time, in the method of the present invention, it is necessary to supply oxygen-containing gas to the butadiene recovery column.

The oxygen-containing gas supplied to the recovery tower is a gas whose oxygen concentration is not very high in order to avoid undesirable side reactions with the acetoxylation reaction product under the operating conditions of the recovery tower, and is usually oxygen-containing gas of 0.01~
The content is 21%, preferably 0.1 to 11%, and contains an inert gas such as nitrogen or argon as other inert components.

Furthermore, in the method of the present invention, the gas discharged from the first butadiene absorption tower usually contains oxygen, nitrogen, carbon dioxide, etc., and the content ratio varies depending on the acetoxylation reaction conditions, but the gas The oxygen concentration inside is approximately 1 to 10%. Therefore, as the oxygen-containing gas supplied to the recovery tower,
A part of the gas discharged from the butadiene absorption tower is
If necessary, the oxygen concentration in the gas may be adjusted before supplying the gas, making it even more efficient. In either case, it is of course important to avoid the formation of explosive mixtures in the recovery tower.

The amount of gas supplied is in the range of 0.01 to 100 times, preferably 0.1 to 50 times, the amount of butadiene treated in the recovery column. If the gas amount exceeds this range and is too small, a sufficient polymerization inhibiting effect cannot be achieved, and if it is too large, the diameter of the recovery column must be increased, which is economically disadvantageous. Moreover, the amount of gas other than butadiene supplied to the butadiene absorption tower increases, which is undesirable because it lowers the absorption rate.

The butadiene recovery column is operated at a bottom temperature of 20 to 140°C, preferably 30 to 130°C, more preferably 40 to 120°C. This is extremely advantageous in preventing butadiene polymerization since the operating pressure can be significantly lowered with the same operating pressure compared to when no supply is made.

Although a general distillation column may be used as the butadiene recovery column, use of a stripping column is advantageous because a reboiler is not required and construction costs and utility costs can be reduced.

In addition, the reaction product liquid is subjected to flash evaporation under a pressure slightly higher than the operating pressure of the butadiene recovery tower before being supplied to the butadiene recovery tower, and the generated gas is transferred to a second
It is preferable to supply the liquid to the bottom of a butadiene absorption tower (described later) and to supply the effluent liquid to a butadiene recovery tower. Thereby, the recovery rate of butadiene in the purification system can be increased.

The butadiene-containing gas distilled from the butadiene recovery tower is below the tower top pressure, preferably 0 to 4 Kg/cm ²
G, more preferably 0.2 to 1 kg/cm ² G, is supplied to a second butadiene absorption tower operated at a pressure of 0.2 to 1 kg/cm 2 G, and the butadiene is absorbed and treated with acetic acid. The operating temperature of the second absorption tower is 10-50°C, preferably 20-40°C.

There are no particular restrictions on the acetic acid used in the first and second butadiene absorption towers, and commercially available acetic acid may be used as well. For example, acetic acid produced by heating may be used.

As the butadiene absorption tower, any equipment used in normal absorption operations can be used, and examples thereof include packed towers, tray towers, spray towers, and the like.

The butadiene absorbed into acetic acid in the two absorption towers as described above is fed back to the acetoxylation reaction zone.

Gas-liquid separation of the acetoxylation reaction product can be carried out once depending on the conditions, but it may be carried out two or more times under different conditions depending on the case. For example, the gas separated in the gas-liquid separation (first gas-liquid separation) following the acetoxylation reaction, together with the butadiene-containing acetic acid obtained from the first butadiene absorption tower, is separated at a temperature lower than that in the first gas-liquid separation. Part of the separated gas thus obtained is supplied to the acetoxylation reaction zone, and the remainder is supplied to the first butadiene absorption tower. After the pressure is reduced, the separated liquid is supplied to the second butadiene absorption tower together with the distillate gas from the butadiene recovery tower and treated as described above.

In addition, in the method of the present invention, after the acetoxylation reaction product is separated into gas and liquid, a part of the separated gas is recycled to the acetoxylation reaction step, and the remainder is supplied to the first butadiene absorption tower. It is advantageous to use a rotary compressor with a liquid membrane shaft seal.

An example of an embodiment of the present invention will be described with reference to FIG. In the figure, indicates an acetoxylation reaction zone, indicates a gas-liquid separator, indicates a butadiene recovery column, indicates a first butadiene absorption column, and indicates a second butadiene absorption column.
Then, raw material butadiene, acetic acid, and oxygen-containing gas are introduced into the reaction zone to carry out an acetoxylation reaction.
The obtained reaction product is further introduced into a gas-liquid separator and subjected to gas-liquid separation. A gas-liquid separator can also be installed at the bottom of the acetoxylation reaction zone. After the pressure is reduced, the separated liquid is supplied to the butadiene recovery tower.
Collect dissolved unreacted butadiene. When a stripping tower is used as a recovery tower, a heat exchanger is provided as necessary in the middle of the line, and the temperature of the recovery tower is adjusted by heating or cooling. More oxygen-containing gas is supplied to the bottom of the butadiene recovery column, but in some cases, a portion of the gas flowing out from the top of the first butadiene absorption column may be introduced through the bottom.

A bottom liquor containing 1,4-diacetoxybutene and acetic acid as main components is obtained from the bottom of the butadiene recovery tower, and this is subsequently fed to a deacetate tower (not shown). A bottom liquor containing acetoxybutene as a main component is obtained. In addition, the acetic acid obtained from the top of the acetic acid removal column is separated from water and then transferred to the first and second
Advantageously, it is fed to a butadiene absorption column. The butadiene-containing gas obtained from the column section of the butadiene recovery column is further supplied to the second butadiene absorption column, and the butadiene is absorbed and treated with acetic acid supplied from the second butadiene absorption column. The butadiene-containing acetic acid flowing out from the bottom of the column is supplied to the acetoxylation reaction zone, and the gas flowing out from the top of the column is purged out of the system.

A portion of the separated gas obtained from the separator described above is introduced into the first butadiene absorption tower. In the first absorption tower, butadiene is absorbed by the acetic acid supplied from above, and acetic acid containing butadiene is obtained from the bottom of the tower, which is further supplied to the acetoxylation reaction zone. The gas flowing out from the top of the column is purged out of the system, but if necessary, a portion of it is introduced into the bottom of the butadiene recovery column. The gas to be purged is preferably treated by absorbing acetic acid in the gas with water prior to purging.

As described above, according to the method of the present invention, by supplying oxygen-containing gas to the butadiene recovery column, the butadiene polymerization preventing effect of oxygen itself and the polymerization preventing effect due to the reduction in operating temperature are combined, and the polymerization of butadiene is extremely advantageously suppressed. It is possible to produce diacetoxybutene safely and economically by preventing troubles in the purification system of acetoxylation reaction products caused by butadiene polymer adhesion to the inside of the recovery tower, equipment corrosion, etc. can do. or,
A more economically advantageous closed system can be obtained by using the exhaust gas from the first butadiene absorption tower as the oxygen-containing gas.

Next, the present invention will be explained in more detail based on Examples, but the present invention is not limited to the following Examples unless it exceeds the gist thereof.

Example 1 1400, 2290, 63630, and 25450 parts of butadiene, air, recycled gas, and recycled acetic acid, respectively.
hr, to the acetoxylation reaction zone at a pressure of 93 Kg/cm ² G and a temperature of 50°C. The reaction area has an inner diameter of 1800 mm.
Two reactors made of SUS316 with a height of 8000 mm are connected, and each reactor is filled with 4 to 6 mesh coconut shell activated carbon supporting palladium and tellurium.
Partially filled.

The outlet pressure of the reaction zone is 91Kg/cm ² G, and the temperature is 80℃.
Under these conditions, the product is separated into gas and liquid at the bottom of the reactor, resulting in an effluent containing mainly 1,4-diacetoxybutene (13.7wt%) and acetic acid.
27,240 parts/hr and 65,530 parts/hr of effluent gas containing oxygen and butadiene were obtained.

The effluent is depressurized and fed to a butadiene recovery tower.
At the same time, 179 parts/hr of distillate gas from the first butadiene absorption tower (described later) was supplied to the bottom of the recovery tower. 1,299 parts/hr of distillate gas containing 17.6 wt% butadiene was obtained from the top of the recovery column, and 26,120 parts/hr of bottoms containing 1,4-diacetoxybutene (14.3 wt%) and acetic acid was obtained from the bottom of the column. Obtained.

The butadiene recovery tower is made of SUS316 with an inner diameter of 1000 mm.
It is equipped with a 10-stage condenser and reboiler on perforated plate trays with a height of 7,000 mm and a top pressure of 0.65 Kg/cm ² G and reflux liquid volume by heating with the reboiler.
It was operated at a temperature of 56 parts/hr and a bottom temperature of 132°C.

This bottoms is continuously fed to a deacetic acid tower to obtain acetic acid with a purity of 98.5wt% from the top of the tower, and acetic acid with a purity of 98.5wt% is obtained from the bottom of the tower.
86.5 wt% of 1,4-diacetoxybutene was obtained.

On the other hand, the effluent gas from the acetoxylation reaction zone
65,530 parts/hr contains butadiene from the first butadiene absorption tower (described later) under a pressure of 90 Kg/cm ² G, and is cooled to 45°C together with 2,460 parts/hr of the effluent mainly containing acetic acid, and then further separated into gas and liquid. 65,120 parts/hr of a separated gas mainly composed of nitrogen containing 4.95 wt% oxygen and 2870 parts/hr of a separated liquid mainly composed of acetic acid were obtained.

After reducing the pressure of this separated liquid, it was supplied to the bottom of the second butadiene absorption tower together with 1299 parts/hr of distillate gas from the above-mentioned butadiene recovery tower, while at the same time it was supplied from the top of the tower.
Acetic acid at 35°C was supplied at a rate of 21,970 parts/hr and brought into contact with gas-liquid exchange within the column. The second butadiene absorption tower has an inner diameter of
Made of SUS316 with a length of 1000mm and a height of 15000mm, 35℃ and tower top pressure.
It was operated at 0.6 Kg/cm ² G, and 25,450 parts/hr of acetic acid containing butadiene was obtained from the bottom of the column. Additionally, from the top of the tower, waste gas with a butadiene content of 100 ppm (by volume) is discharged.
689 parts/hr was obtained, which was washed in a water washing tower and then discharged.

Of the 65,120 parts/hr of separated gas at a pressure of 90 Kg/cm ² G obtained in the gas-liquid separation described above, 1,490 parts/hr was supplied to the bottom of the first butadiene absorption tower, while acetic acid at 35°C was supplied from the top of the absorption tower. Supplying 2430 parts/hr at 96Kg/cm ² G,
A gas-liquid exchange contact was made. Waste gas with a butadiene content of 100 ppm (volume) is obtained from the top of the column at a rate of 1,460 parts/hr.
Of this amount, 179 parts/hr was supplied to the bottom of the recovery tower. In addition, the remaining 63,630 parts of separated gas at a pressure of 90 Kg/cm ² G
hr was recycled to the acetoxylation reaction zone.

From the bottom of the first butadiene absorption tower, 2460 parts/hr of acetic acid containing butadiene was obtained, which was recycled to the gas-liquid separator as described above. The first butadiene absorption tower was made of SUS316 with an inner diameter of 500 mm and a height of 10,000 mm, and was operated at 35° C. and 96 Kg/cm ² G.

When all the equipment was operated continuously under the above operating conditions, it was possible to continue operation for 3912 hours.

Example 2 All of the distillate gas from the first butadiene absorption tower was discharged outside the system, and a mixed gas of 20 parts/hr of oxygen and 159 parts/hr of nitrogen was supplied from outside the system to the bottom of the butadiene recovery tower. The same equipment as in Example 1 was used and operated under the same conditions. As a result, the butadiene recovery tower was able to operate continuously for 4178 hours.

Example 3 Of the distillate gas from the first butadiene absorption tower,
358 parts/hr was supplied to the bottom of the butadiene recovery column,
In addition, the butadiene recovery tower was constructed using the same equipment as in Example 1, except that no heat was applied to the reboiler, and the temperature inside the tower was maintained at 110°C by heating the feed liquid with a separately installed heater and then introducing it. was used and operated under the same conditions. As a result, the butadiene recovery tower was still in a state where it could continue to operate even after one year of continuous operation.

Comparative Example 1 Both the butadiene recovery tower and the second butadiene absorption tower are operated at normal pressure, and the butadiene recovery tower has a bottom temperature of 125°C by heating with a reboiler without supplying gas to the bottom. The same equipment as in Example 1 was used except that the reflux ratio condition of 0.05 was maintained,
It was operated under the same conditions. As a result, it became impossible to continue operation 1098 hours after the start of continuous operation. After the operation was stopped, the inside of the butadiene recovery tower was inspected and a large amount of rubbery material was found adhering to the perforated plate tray. When this was analyzed by IR spectroscopy and elemental analysis, it was confirmed that it was a butadiene polymer.

[Brief explanation of the drawing]

The figure is a flow sheet illustrating an example of an embodiment of the present invention, and shows an acetoxylation reaction zone, a gas-liquid separator, a butadiene recovery column, a first butadiene absorption column, and a second butadiene absorption column.

Claims (1)

[Scope of Claims] 1. In producing diacetoxybutene by reacting butadiene, an oxygen-containing gas, and acetic acid in an acetoxylation reaction zone under a pressure of 20 kg/cm ² G or higher in the presence of a supported palladium catalyst, an acetoxy reaction is performed. The reaction product obtained from the zone is separated into gas and liquid, a part of the separated gas is supplied to the reaction zone, and the remainder is supplied to the first butadiene absorption tower to absorb butadiene into acetic acid, while the separated liquid is The butadiene is then supplied to a butadiene recovery tower, and at the same time an oxygen-containing gas is supplied to the recovery tower, and the butadiene-containing gas distilled from the tower is supplied to a second butadiene absorption tower to absorb butadiene into acetic acid. A method for producing diacetoxybutene, characterized in that acetic acid containing butadiene flowing out from the bottom of a butadiene absorption tower is supplied to an acetoxylation reaction zone. 2. In the method set forth in claim 1, the first
A method for producing diacetoxybutene, which comprises supplying a part of the gas discharged from the top of a butadiene absorption tower to a butadiene recovery tower as an oxygen-containing gas. 3. A method for producing diacetoxybutene according to claim 1 or 2, characterized in that a stripping tower is used as the butadiene recovery tower.