KR102008794B1 - Method for producing conjugated diene - Google Patents

Abstract

The present invention relates to a method for producing a conjugated diene, and according to the present invention, as an absorption treatment condition of an organic solution in which a product gas containing butadiene is absorbed in an organic solvent, an operating pressure of the absorption step or an input amount of an absorbing solvent can be reduced. The introduction of the process has the effect of providing a method for producing a conjugated diene with excellent economic efficiency, such as reduced investment costs or operating costs when the conjugated diene purification.

Description

Method for producing conjugated diene {METHOD FOR PRODUCING CONJUGATED DIENE}

The present invention relates to a method for producing a conjugated diene, and more particularly, an operating pressure of an absorption step or an input amount of an absorption solvent can be reduced as an absorption treatment condition of an organic solution in which a product gas containing butadiene is absorbed in an organic solvent. The present invention relates to a method for producing conjugated diene having excellent economic efficiency, such as reducing investment cost or operating cost when refining conjugated diene by introducing a process.

1,3-butadiene can be produced by oxidative dehydrogenation of a monoolefin such as n-butene in the presence of a catalyst.

As a prior art for recovering butadiene from a reaction mixture gas containing 1,3-butadiene produced by the oxidative dehydrogenation reaction, US Pat. No. 4,597,883 or the like discloses most of C4 including butadiene prior to crude butadiene separation. A technique is disclosed in which a component is absorbed using xylene as the absorption solvent and the residual gas is circulated through the degassing process to the reactor. However, according to these technologies, a process of absorbing the used absorbing solvent (xylene) as a higher boiling point solvent than xylene was needed. Therefore, economical technology development such as investment cost or operating cost reduction is still required in the butadiene purification process. to be.

In order to solve the problems of the prior art as described above, an object of the present invention is to provide a method for producing a conjugated diene with excellent economic efficiency by introducing a process capable of reducing the operating pressure or the input amount of the absorbing solvent in the absorption step.

In order to achieve the above object, the present invention comprises the steps of: a) oxidative dehydrogenation reaction of a source gas containing N-butene under a catalyst, to produce a product gas containing butadiene; b) cooling the product gas with water; c) absorbing the cooled product gas into an amide organic solvent to prepare an absorption solution; And d) degassing and stripping the absorbent solution to obtain crude butadiene, wherein the cooled product gas and the amide organic solvent of step c) are countercurrent flows. It provides a method for producing a conjugated diene having a (counterflow), wherein a portion of the prepared absorbing solution is recycled to the countercurrent flow.

According to the present invention, as an absorbent treatment condition of an absorbent solution in which a product gas containing butadiene is absorbed in an organic solvent, an investment cost or an operating cost can be reduced when the conjugated diene is purified by introducing a process that can reduce the operating pressure of the absorption step or the input amount of the absorbent solvent. It is effective to provide a method for producing conjugated diene having excellent economic efficiency.

1 is a process diagram schematically showing a manufacturing process of the conjugated diene according to the present invention.

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated in detail.

Method for producing a conjugated diene of the present invention, for example, a) oxidative dehydrogenation reaction of a raw material gas containing N-butene under a catalyst, to produce a product gas containing butadiene; b) cooling the product gas with water; c) absorbing the cooled product gas into an amide organic solvent to prepare an absorption solution; And d) degassing and stripping the absorbent solution to obtain crude butadiene, wherein the cooled product gas and the amide organic solvent of step c) are countercurrent flows. (counterflow), characterized in that part of the absorbent solution prepared is recycled to the countercurrent flow.

In the absorption step as described above, when the product gas cooled by the water and the organic solvent has a countercurrent flow, the lower flow of the countercurrent flow includes a recirculation stream can lower the operating pressure of the absorption tower itself or Since the amount of the amide-based organic solvent required can be reduced, an investment cost or an operation cost can be greatly reduced when the conjugated diene is purified.

 The countercurrent flow may be formed by sending the product gas cooled with water to the tower under an absorber column and sending the amide organic solvent from the tower to the bottom of the tower.

The amide organic solvent used as the absorption solvent in the present invention may be, for example, at least one selected from dimethylformamide, diethylformamide, and dimethylacetamide, and preferably dimethylformamide may be used.

 The amide organic solvent may be supplied at a temperature of 5 ° C. to 40 ° C., preferably 5 ° C. to 20 ° C., most preferably 5 ° C. to 10 ° C., above the absorber column, through the temperature range. It has an excellent effect on absorption.

The recirculation flow may be preferably formed by flowing the absorbent solution discharged from the lower outlet of the absorption tower back to the lower portion of the absorption tower. Here, the lower part of the absorption tower to which the recycle stream is connected may mean one point from the middle point of the absorption tower to the point where the product gas is introduced.

Absorption of step c) may be, for example, a weight ratio (DMF / BD) between the supply flow rate of butadiene contained in the cooled product gas and the supply flow rate of the amide organic solvent, 5 to 6.77, or 5.23 to 6.77, Within this range, there is an excellent effect of absorbency.

The recirculation flow is, for example, the countercurrent flow, that is, the product gas input in the absorption stage is less than 8 theoretical stages, preferably 10 or less stages, most preferably 11 or less stages in the absorber column of 15 stages Injecting above the point may provide the effect of using the least amount of solvent relative to the set reflux rate.

The recirculation flow is, for example, a minimum mass reflux ratio of 0.5 to 0.7, or 0.55 to 0.65 It can be in a range, and it is excellent in the effect which reduces an operating pressure or an organic solvent input amount in this range.

Absorption of step c) is, for example, the upper operating pressure of the absorber column (absorber column) 12 kg / cm ² g or less or 7 kg / cm ² g to 12 kg / cm ² g, and the absorption treatment temperature 0 ℃ to 50 ℃ or 5 It may be carried out under ℃ to 40 ℃. In particular, the upper operating pressure of the absorption tower is a range reduced by using a high pressure of more than 12kg / cm ² g, the aforementioned countercurrent flow and recirculation flow, the advantage of improving the economics according to the operating pressure reduction To provide.

The lower operating pressure of the absorber upon the upper operating pressure of the above-described absorber can typically range from, may be 12kg / cm ² g to about 12.5kg / cm ² g, for example.

Hereinafter, a method for producing a conjugated diene according to the present invention including the above absorption conditions will be described in detail with reference to the accompanying drawings.

1 is a process diagram schematically showing a manufacturing process of butadiene according to the present invention.

First, a) oxidative dehydrogenation reaction of a raw material gas containing N-butene under a catalyst to produce a product gas containing butadiene.

The N-butene is 1-butene, 2-butene or a mixture thereof.

For example, the raw material gas containing N-butene is a high-purity N-butene gas, an oil containing N-butene as a main component and N-butane obtained by separating butadiene and i-butene from a C ₄ fraction produced by naphtha decomposition. Butene gas produced by dehydrogenation or oxidative dehydrogenation reaction, reaction product gas obtained by dimerization of ethylene, or gas containing hydrocarbons having 4 carbon atoms obtained from fluid catalytic cracking of heavy oil oil. .

The raw material gas containing N-butene may include, for example, 40 vol% or more, preferably 60 vol% or more, more preferably 75 vol% or more, particularly preferably 99 vol% or more, of N-butene, Within this range, the reaction rate and yield are excellent.

The catalyst may be, for example, a molybdate-bismuth based catalyst.

The molybdate-bismuth-based catalyst is not particularly limited in the case of a molybdate-bismuth-based catalyst that can be typically used for oxidative dehydrogenation of butene.

The molybdate-bismuth based catalyst may be a composite oxide catalyst including, for example, molybdenum, bismuth, and cobalt.

The oxidative dehydrogenation reaction may be, for example, a reaction for producing butadiene by reacting a source gas containing N-butene with a molecular oxygen-containing gas under a catalyst.

The molecular oxygen-containing gas is, for example, a gas containing 10% by volume to 50% by volume of molecular oxygen, preferably 15% by volume to 30% by volume, more preferably 20% by volume to 25% by volume.

The molecular oxygen-containing gas may include, for example, impurities such as nitrogen, argon, neon, helium, and the like, which do not significantly inhibit the oxidative dehydrogenation reaction.

As another example, the molecular oxygen-containing gas may be air.

For example, in supplying the source gas and the molecular oxygen-containing gas to the reactor, the source gas and the molecular oxygen-containing gas may be mixed first, and the mixed gas may be supplied to the reactor. The proportion of source gas in the mixed gas may be, for example, 4.2% by volume to 20.0% by volume.

With the mixed gas, for example, nitrogen gas and / or water vapor may be supplied to the reactor, and the input of the nitrogen gas has an effect of adjusting the concentrations of the combustible gas and the oxygen so that the mixed gas does not form a detonating gas. In addition, the addition of the water vapor has the effect of controlling the concentration of the combustible gas and oxygen, and also suppress the deterioration of the catalyst.

The reactor used for the oxidative dehydrogenation reaction is not particularly limited as long as it is a conventional reactor used in the art, and may be, for example, a tubular reactor, a tank reactor, a fluidized bed reactor, or a fixed bed reactor.

The stationary phase reactor may be, for example, a multi-tube reactor or a plate reactor.

The fixed bed reactor includes, for example, a catalyst layer on which the oxidative dehydrogenation reaction catalyst is fixed. The catalyst layer may be composed of only a catalyst or a solid that is not reactive with a catalyst. The layers consisting of solids without these can be formed together or in plurality.

In the case of including the solid or the layer containing the solid, it is possible to suppress the rapid temperature rise of the catalyst layer due to the exotherm during the reaction. In addition, when there are a plurality of catalyst layers, the plurality of layers may be layered, for example, from the inlet of the reactor toward the direction of the output gas outlet of the reactor.

When the catalyst layer includes a layer composed of a solid material that is not reactive with the catalyst, the catalyst dilution rate represented by the following formula may be, for example, 10 vol% to 99 vol%.

Dilution rate = [(volume of solids) / (volume of catalyst + volume of solids)] X 100

The non-reactive solid is stable under the conditions for the formation of conjugated diene, and is not limited to a raw material such as monoolefin having 4 or more carbon atoms, and a material that is not reactive with a product such as conjugated diene. Ceramic materials such as alumina and zirconia.

The non-reactive solid may have a spherical shape, a cylindrical shape, a ring shape, or an irregular shape. In addition , the size may be, for example, the same size as the catalyst used in the present disclosure, and the particle size may be, for example, about 2 mm to 10 mm.

The filling length of the catalyst layer is determined by the activity of the catalyst to be charged (activity as a diluted catalyst, when diluted with an unreactive solid), the size of the reactor, the reaction raw material gas temperature, the reaction temperature, and the reaction conditions. It can be obtained by material balance and heat balance calculation.

The oxidative dehydrogenation reaction is usually an exothermic reaction. For example, the oxidative dehydrogenation reaction may be controlled at 250 ° C. to 450 ° C., and heat generation may be controlled by using a heat medium (for example, dibenzyltoluene or nitrite).

If the reaction temperature, i.e., the temperature of the catalyst layer exceeds 450 ° C, the reaction continues to decrease rapidly as the reaction continues. If the temperature of the catalyst layer is less than 250 ° C, the yield of conjugated diene as the target product tends to decrease. .

The pressure in the reactor may be, for example, at least 0 MPaG, or more than 0 MPaG to 0.5 MPaG, the residence time of the reactor may be 0.36 seconds to 72 seconds, and the ratio of the flow rate of the mixed gas to the amount of catalyst in the reactor is 50 h ⁻¹ to It may be 10000h ^-1 .

The flow rate difference between the inlet and the outlet of the reactor depends on the flow rate at the reactor inlet of the source gas and the flow rate at the reactor outlet of the generated gas, but the flow rate of the outlet relative to the inlet flow rate (100% by volume) is 100% by volume, for example. To 110% by volume. In this way, the oxidative dehydrogenation reaction of the monoolefin in source gas produces | generates the conjugated diene corresponding to this monoolefin, and acquires the generated gas containing the conjugated diene at the exit of a reactor. The concentration of the conjugated diene corresponding to the monoolefin in the source gas contained in this product gas depends on the concentration of the monoolefin contained in the source gas, but may be, for example, 1% by volume to 15% by volume, and unreacted monoolefin. The concentration of may be 0% to 7% by volume.

In addition, unless otherwise specified, the high boiling by-products contained in the product gas are substances referred to as the high boiling by-products such as butadiene dimer (BD dimer), 4-formylcyclohexene and 4-acetyl-1-cyclohexene. Can include them.

The high boiling point by-product may be included in an amount of 0.01 wt% to 2 wt%, or 0.1 wt% to 2 wt%, in the generated gas.

The oxidative dehydrogenation reaction of step a) is, for example, the conversion rate is 95% or more, or 96% or more, and the unsaturated aldehydes present in the solution before the separation of butadiene within the above range (acrolein corresponding to the high boiling point byproduct, part Tenon, benzaldehyde) is preferable because the content itself is small.

In FIG. 1, a product gas including butadiene produced by an oxidative dehydrogenation reaction in an oxidative dehydrogenation reactor (not shown) is supplied to a cooling tower (Quencher) as step b) and cooled, and contains butadiene discharged as step c). Steam, that is, the cooled product gas is absorbed into the organic solvent to prepare an organic solution, that is, an absorption solution.

In the cooling tower, the cooling water (Water) is introduced into the upper portion by the pipe, and is in countercurrent contact with the product gas introduced into the lower portion. The cooling water which cooled the product gas by this countercurrent contact is discharged | emitted to the piping of a tower bottom. At this time, the discharged cooling water may be partially or entirely cooled in the heat exchanger and used again in the cooling tower.

Specifically, the cooling is condensed by spraying water of 30 ℃ to 50 ℃, or 35 to 45 ℃ on the top of the cooling tower, the lower discharge water is cooled and recycled, waste water treatment of some of the recycle water, the top discharge gas of the cooling tower Is injected into an aldehyde removal tower and water is sprayed at 10 ° C. to 30 ° C., or 15 ° C. to 25 ° C. at the top of the removal tower, and the bottom discharge water is kept for 1 hour or less, or 40 minutes to 1 hour under reduced pressure heating conditions. After recirculation to the removal tower is characterized in that.

The reduced pressure heating conditions may be, for example, a condition of 30 mbar / (30 ℃ to 60 ℃) to 150 mbar / (30 ℃ to 60 ℃), or 50 mbar / (40 ℃ to 55 ℃) to 100 mbar / (40 ° C. to 55 ° C.).

The cooled product gas flows out to the top of the cooling tower, and is then boosted to a predetermined pressure through a compressor, and then supplied to the absorber as step c), and in countercurrent contact with the amide organic solvent as the absorption solvent. The amide organic solvent may be, for example, at least one selected from dimethylformamide, diethylformamide, and dimethylacetamide, and preferably dimethylformamide may be used, and the upper part of the absorber column may be 5 It may be supplied at a temperature of ℃ to 40 ℃.

The weight ratio (DMF / BD) between the supply flow rate of butadiene contained in the butadiene-containing steam and the supply flow rate of the amide organic solvent supplied to the absorption tower in step c) is 5.23 to May be 6.77.

Due to the countercurrent contact, butadiene in the product gas, unreacted raw material gas, and the like are absorbed into an organic solvent such as dimethylformamide. Herein, the gas component not absorbed in dimethylformamide may be discharged to the top of the absorption tower to be burned off (off gas) or sent back to the reactor for circulation.

The product gas absorbent liquid containing butadiene and unreacted raw material gas is discharged to the bottom of the absorption tower and supplied to the upper portion of the degassing tower through a pipe.

As a specific example of the recirculation flow, the absorbent solution may be introduced into 10 to 12 stages of theoretical stages in an absorber column of 15 stages, and may be introduced into 11 stages of the most preferable example.

For example, the recirculation flow may have a minimum mass reflux ratio in a range of 0.55 to 0.65.

Absorption of step c) is, for example, the upper operating pressure of the absorber column (absorber column) 7kg / cm ² g to 12kg / cm ² g, the lower operating pressure 12kg / cm ² g to 12.5kg / cm ² g, and the absorption The treatment may be performed at a temperature of 0 ° C. to 50 ° C., and absorption efficiency of hydrocarbons such as conjugated diene may be good without oxygen or nitrogen being well absorbed into the solvent within the above range.

The product gas absorbing liquid prepared in step c) may be subjected to a degassing process by spraying the organic solution on the degassing column at a supply temperature of 30 ° C. to 40 ° C. before the stripping process, for example. In this case, there is an effect of removing nitrogen or oxygen dissolved in the absorbent liquid.

Since a small amount of nitrogen and oxygen are also dissolved in the product gas absorption liquid obtained by the absorption tower, this product gas absorption liquid is supplied to the degassing column and heated as a first step of d) to remove them by gasification. At this time, since part of butadiene and raw material gas may be gasified, the gas discharged to the top of the degassing column is circulated to the inlet side of the compressor in order to increase the recovery rate of butadiene.

In the degassing step, a degassing process may be performed under a temperature condition of 110 ° C to 130 ° C, and the degassed product gas absorbent liquid is supplied to a solvent stripper as a second step of d) through a pipe. In the solvent separation column, the reboiler (bottom) and the condenser (top) are subjected to distillation of the product gas absorption liquid, and crude butadiene is extracted from the column top, and the separated dimethylformamide is discharged to the bottom. At this time, the dimethylformamide discharged to the bottom may be circulated as an absorption solvent.

If necessary, the condensed water may be separated and discharged from the product gas by passing through a cooler before the product gas flowing out of the top of the cooling tower is introduced into the compressor. In addition, after passing through the compressor, the pressurized product gas may be dewatered by passing through a dehydration tower filled with a drying material such as molecular sieves before introducing the boosted gas into the absorption tower.

The stripping is not particularly limited in the case of a stripping method capable of separating crude butadiene and a solvent.

In one example, the stripping may be by distillation separation.

The distillation separation may be a method of extracting crude butadiene from the column top by distilling the product gas absorbent liquid by a reboiler and a condenser as a specific example.

For example, the organic solution from which the residual gas is removed by the degassing treatment may be cooled to a supply temperature of 10 ° C. to 30 ° C., and then sprayed onto a solvent separation tower. Crude butadiene is stripped and the remaining solution can be reused with the organic solvent of the second step of b).

The crude butadiene of step d) is, for example, the purity of 1.3-butadiene is 91% to 99% by weight, or 95% to 98% by weight, 0.1% to 2% by weight of the high boiling by-products, or 0.1 wt% to 1 wt% may be included.

Hereinafter, preferred examples are provided to help the understanding of the present invention, but the following examples are merely for exemplifying the present invention, and various changes and modifications within the scope and spirit of the present invention are apparent to those skilled in the art. It goes without saying that changes and modifications belong to the appended claims.

EXAMPLE

The cooling tower used in the present example used a 3 m high filling column, and was designed to allow water input at the top and waste water discharge and reflux at the bottom, and the absorption tower used a 7 m high filling column. In order to enable extractive distillation, dimethylformamide (DMF) was added at the top, and butadiene-containing steam was input at the bottom, reboiler, and reflux (condenser) were designed to be possible.

Example  One

First, a multicomponent bismuth molybdenum catalyst (complex oxide catalyst having a composition ratio of Mo 1-15, Bi 1-10, Fe 1-10, Co 1-10, K 0.01-1.5, and Cs 0-1.5) was used. Packed in a tubular reactor and subjected to oxidative dehydrogenation at 320 ° C. while supplying raw gas at a molar ratio of 75 h ⁻¹ , oxygen / 1-butene = 1, steam / 1-butene = 3, and nitrogen / 1-butene = 9 A product gas containing 98% butadiene was converted.

The generated gas is cooled by injecting 9 kg / h of water at 40 ° C. from the top of the cooling tower, and discharged about 0.4 kg / h from the bottom of the cooling tower as wastewater containing high boiling by-products, and then discharged from the top of the cooling tower (quencher). The gas was compressed with a compressor (pneumatic gas booster) and then fed to the absorption tower. At this time, the temperature of the gas was 30 ℃ to 35 ℃, the flow rate of the product gas to the absorption tower was 49,705kg / h.

Dimethyl formamide (DMF) at 5 ° C. to 10 ° C. was injected onto the absorption tower, and was supplied at 47,786 kg / h, a flow rate of 5.23 times the weight ratio based on the supply flow rate of butadiene in the product gas introduced into the absorption tower.

Then, the flow of the absorption solution containing the unreacted product gas in the bottom discharge of the absorption tower was refluxed to the bottom of the absorption tower (11 theoretical stages) under the flow conditions of the recycling to form a recycle flow.

In this case, gas chromatography (model: Agilent Technologies 5890N, colum: HP-1 (FID) with PORAPAK-Q / Molecular sieve) is used to determine the composition of the gas discharged without being absorbed to the upper part of the absorption tower and the composition of the conjugated diene-containing absorption solution discharged to the lower part. 5A (TCD), and then held 0 ℃ to 22 minutes to 32 minutes the temperature was raised to 100 ℃, after 3 minutes the temperature holding that after by up to 51 minutes the temperature was raised to 260 ℃ analysis 71 minutes ended, wherein the temperature raising rate is 10 ℃ · min ^{- It was} measured using ¹ ), and the absorption rate (absorption amount / inflow amount) of the detection components including butadiene calculated from it are shown in Table 1 together.

<Absorption conditions and recycling Flow condition >

Gas inlet (kg / h): 49,705

Solvent inlet (kg / h): 47,786

Reflux rate (kg / h): 100,007

Reflux temperature (℃): 5.0

Reflux stage (#): 11

Column Top P (kg / cm ² g): 12.0

Top rate (kg / h): 36979.52

Absorbed rate (kg / h): 64010.83

Reflux flow rate / Bottom flow rate: 0.610 (Bottom flow rate is the total bottom flow rate before reflux)

Example  2

The same process as in Example 1 was repeated except that the absorption conditions and the flow conditions of the recycling in Example 1 were replaced as follows, and the absorption rates of the detection components including butadiene calculated therefrom are shown in Table 1 below. Indicated.

<Absorption conditions and recycling Flow condition >

Gas inlet (kg / h): 49,705

Solvent inlet (kg / h): 61,929

Reflux rate (kg / h): 100,001

Reflux temperature (℃): 5.0

Reflux stage (#): 11

Column Top P (kg / cm ² g): 8.5

Top rate (kg / h): 37136.17

Absorbed rate (kg / h): 77939.08

Reflux / Bottom: 0.562

Comparative example  One

The same process as in Example 1 was repeated except that the absorption conditions and the flow conditions of the recycling in Example 1 were replaced as follows, and the absorption rates of the detection components including butadiene calculated therefrom are shown in Table 1 below. Indicated.

<Absorption conditions and recycling Flow condition >

Gas inlet (kg / h): 49,705

Solvent inlet (kg / h): 62,476

Reflux rate (kg / h):-

Reflux temperature (℃):-

Reflux stage (#):-

Column Top P (kg / cm ² g): 12.0

 TABLE 1

As shown in Table 1, in the case of using a countercurrent flow and a recycle stream in accordance with the present invention, while reducing the input amount of the organic solvent as demonstrated in Example 1 while maintaining a high butadiene absorption rate of 99.5%, or 99.5 It was confirmed that the operating pressure can be reduced in the absorption step as demonstrated in Example 2 while maintaining the butadiene absorption rate of%.

On the other hand, when the countercurrent flow is used according to the prior art, but the recycle flow is not used together, as shown in Comparative Example 1, in order to maintain the butadiene absorption rate of 99.5% in the same manner as in Examples 1 and 2, the amount and operation of the organic solvent It was confirmed that the pressure can all be increased.

Claims (9)

a) oxidative dehydrogenation reaction of a source gas containing N-butene under a catalyst to produce a product gas containing butadiene; b) cooling the product gas with water; c) absorbing the cooled product gas into dimethylformamide (DMF) to prepare an absorption solution; And d) degassing and stripping the absorbent solution to obtain crude butadiene.
The cooled product gas and dimethylformamide of step c) have a counterflow, a portion of the absorbent solution prepared is recycled to the countercurrent flow,
The recirculation stream is formed by cooling the absorption liquid discharged from the lower outlet of the absorption tower and then flowing it to one of the points from the middle point of the absorption tower to the point where the product gas is introduced.
Dimethylformamide discharged to the bottom after the stripping is characterized in that the circulation is used as the absorption solvent
Method for preparing butadiene.
The method of claim 1,
The countercurrent flow is formed by sending the cooled product gas above the tower under an absorber column and directing the dimethylformamide from above the tower to the bottom of the tower.
Method for preparing butadiene.
delete The method of claim 1,
The dimethylformamide is supplied to the absorber column (above the absorber column) at a temperature of 5 ℃ ~ 40 ℃
Method for preparing butadiene.
delete The method of claim 1,
Absorption of step c) is a weight ratio (DMF / BD) between the supply flow rate of butadiene contained in the cooled product gas and the supply flow rate of the dimethylformamide is 5 to 6.77.
The method of claim 1,
The recirculation flow is characterized in that the absorbing solution is put in 8 or fewer theoretical stages of the absorber column of 15 stages
Method for preparing butadiene.
The method of claim 1,
Absorption of step c) is carried out under the upper operating pressure of 7kg / cm ² g to 12kg / cm ² g of the absorber column, and the absorption treatment temperature 0 ℃ to 50 ℃
Method for preparing butadiene.
The method of claim 1,
The catalyst of step a) is a method of producing butadiene, characterized in that the molybdate-bismuth-based catalyst.

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