KR20160084043A - Method for producing conjugated diene - Google Patents

Abstract

The present invention relates to a manufacturing method of conjugated diene. According to the present invention, a manufacturing method of conjugated diene such as butadiene, or the like, through a contact oxidative dehydrogenation reaction of mono-olefin such as n-butene, or the like can effectively remove byproducts such as acrolein, butenone, benzaldehyde, and the like, during a dehydration process after a cooling process without using a desiccant. The manufacturing method comprises the following steps of: a) manufacturing a product gas including butadiene by oxidative dehydrogenation of a raw gas including n-butene; b) cooling the product gas, and manufacturing an organic solution by making the product gas absorb to an organic solvent; and c) obtaining crude butadiene by degassing and stripping the organic solution.

Description

METHOD FOR PRODUCING CONJUGATED DIENE [0002]

More particularly, the present invention relates to a method for producing a conjugated diene such as butadiene by a catalytic oxidative dehydrogenation reaction of a monoolefin such as n-butene or the like, Which can effectively remove by-products such as acrolein, butenone, and benzaldehyde.

As a method for producing a conjugated diene such as butadiene (hereinafter also referred to as " BD ") by oxidative dehydrogenation reaction of a monoolefin such as n-butene in the presence of a catalyst, a catalytic dehydrogenation reaction . In this reaction, water is by-produced.

C4H8 + 1 / 2O2 - > C4H6 + H2O

After recovering the butadiene-containing hydrocarbon from the product gas by using a solvent after producing butadiene by the oxidative dehydrogenation reaction of the butene, most C4 components including butadiene are absorbed before the crude butadiene separation A technique of circulating the residual gas through the degassing process to the reactor has been proposed (see U.S. Patent No. 4595788). However, there is a need for an efficient method for the isobaric absorption step and the subsequent solvent separation step, which further have a disadvantage that a step of absorbing an absorption solvent (e.g., xylene) in a gas used in the above literature with a higher boiling point solvent is further required.

Japanese Patent Application Laid-Open No. 2006-006395 discloses a process for removing impurities from a solvent used in a solvent absorption process or a solvent separation process by moisture in each step of a post- And in particular, the use of a drying agent such as calcium oxide or molecular sieve in the dewatering process is disclosed. However, if an absorbing solvent containing a halogen compound is used as the drying agent, an expensive material is required to prevent corrosion of the apparatus, thereby increasing the investment cost. In the case of using an alkaline absorbing agent such as calcium oxide, It is difficult to expect a stable operation. When an acidic solvent is used, a large amount of water is injected into the organic acid aqueous solution during the injection into the aldehyde removing tower, which causes a problem that the amount of waste water generated is greatly increased. It is necessary to propose an appropriate dewatering process.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and it is an object of the present invention to provide a method for producing a conjugated diene such as butadiene by a catalytic oxidative dehydrogenation reaction of a monoolefin such as n-butene, , And a method for producing a conjugated diene capable of effectively removing by-products such as benzaldehyde.

A method for producing a conjugated diene according to the present invention comprises:

a) preparing a product gas containing butadiene by subjecting a raw material gas containing N-butene to an oxidative dehydrogenation reaction under a catalyst; b) cooling the product gas and absorbing it in an organic solvent to produce an organic solution; And c) degassing and stripping the organic solution to obtain crude butadiene,

The cooling in step b) is carried out by water spraying at a temperature of 30-50 ° C in the upper part of the cooling tower, and then the lower outlet water of the cooling tower is cooled and recycled and partially treated with wastewater. The cooling tower top exhaust gas is introduced into the aldehyde removal tower, And the bottom drainage water discharged by the water injection at 30 DEG C is retained for 1 hour or less under reduced pressure heating and recirculated.

According to the present invention, there is provided a process for producing a conjugated diene such as butadiene by catalytic oxidative dehydrogenation of a monoolefin such as n-butene, wherein the step of dehydration after the cooling step is carried out in the absence of a desiccant to produce acrolein, butenone, It is effective to provide a method for producing a conjugated diene including an improved dehydration process which can remove organisms effectively and the amount of wastewater increase is only about 25%.

Hereinafter, the present invention will be described in detail.

A method for producing a conjugated diene according to the present invention comprises the steps of: a) preparing a product gas containing butadiene by subjecting a raw material gas containing N-butene to an oxidative dehydrogenation reaction under a catalyst; b) cooling the product gas and absorbing it in an organic solvent to produce an organic solution; And c) degassing and stripping the organic solution to obtain crude butadiene,

The cooling in step b) is carried out by water spraying at a temperature of 30-50 ° C in the upper part of the cooling tower, and then the lower outlet water of the cooling tower is cooled and recycled and partially treated with wastewater. The cooling tower top exhaust gas is introduced into the aldehyde removal tower, And the bottom drainage water discharged by the water injection at 30 DEG C is retained for 1 hour or less under reduced pressure heating and recirculated.

The product gas that is absorbed into the organic solvent after cooling in the step b) is, for example, 50% or 97.5% of the by-products of acrolein, butenone, and benzaldehyde under a non-drying agent have.

The term " non-drying agent " refers to those that do not include the type of desiccant conventionally used in the dehydration process, unless otherwise specified.

Hereinafter, the manufacturing method will be described in detail for each step.

First, in the step a), a raw material gas containing N-butene such as monoolefins having 4 or more carbon atoms, for example, 1-butene, 2-butene or a mixture thereof is reacted with a molecular oxygen- The corresponding conjugated diene is prepared by an oxidative dehydrogenation reaction.

Examples of the raw material gas include n-butene, which is produced by separating butadiene and isobutene from C ₄ olefins produced as a by-product of naphtha cracking, and dehydrogenated or dehydrogenated dehydrogenated N-butane Butane oil, a reaction product gas obtained by dimerization of ethylene, or a gas containing hydrocarbons having 4 carbon atoms obtained from Fluid Catalytic Cracking of heavy oil fractions.

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

Specifically, the catalyst may be a multicomponent bismuth molybdate catalyst having a divalent cationic metal component, a metal component having a trivalent cation, bismuth, and molybdenum. It is possible to produce various multicomponent bismuth molybdate catalysts depending on the kind and the ratio of the constituent components.

As another example, the catalyst may be a composite 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.

The raw material gas and the molecular oxygen-containing gas may be mixed, and the mixed gas may be supplied to the reactor.

The ratio of the source gas in the mixed gas may be 4.2 to 20.0% by volume.

The molecular oxygen-containing gas may be 10 vol.% Or more, or 10 to 50 vol.%, For example, of molecular oxygen.

The molecular oxygen-containing gas may be air.

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

In addition to the mixed gas, for example, nitrogen gas and / or steam can be supplied to the reactor. The introduction of the nitrogen gas has the effect of controlling the concentration of the combustible gas and oxygen so that the mixed gas does not form a detonating gas The water vapor controls the concentration of the combustible gas and the oxygen, and has an effect of suppressing deterioration of the catalyst.

The reactor used for the oxidative dehydrogenation reaction may be, for example, a tubular reactor, a shaping reactor, a fluidized bed reactor, or a fixed bed reactor.

The fixed-bed reactor may be, for example, a multi-tubular reactor or a plate reactor.

The fixed-bed reactor may include a catalyst layer on which the oxidative dehydrogenation catalyst is fixed. The catalyst bed may be composed of only a catalyst, or may be composed of a solid material having no reactivity with the catalyst. The solid- May be composed of a single layer or a plurality of layers.

In the case of including the solid or solid-containing layer, a rapid temperature rise of the catalyst layer due to heat generation during the reaction can be suppressed. When a plurality of catalyst layers are provided, the plurality of layers may be formed in a layer shape from the inlet of the reactor toward the outlet of the product gas in the reactor.

When the catalyst layer comprises a layer composed of a solid that is not reactive with the catalyst, the dilution ratio of the catalyst represented by the following formula may be 10 to 99% by volume.

Dilution ratio (volume%) = [(volume of solids) / (volume of catalyst + volume of catalyst and solids)] x 100

The non-reactive solid matter is not limited as long as it is stable under the conditions for producing conjugated dienes, is a raw material such as a monoolefin having 4 or more carbon atoms, and a material that is not reactive with products such as conjugated dienes. A ceramic material such as alumina or zirconia, or the like.

The shape thereof may be spherical, cylindrical, ring, or irregular.

The size may be, for example, the same size as the catalyst used in the present invention, and the particle size may be about 2 to 10 mm, for example.

The charging length of the catalyst layer can be determined by calculation of a material resin and a heat resin when the size of the reactor to be charged, the reaction material gas temperature, the reaction temperature, and the reaction conditions are determined.

The oxidative dehydrogenation reaction is an exothermic reaction, and when the reaction is intact (activity as a diluted catalyst when diluted with a solid having no reactivity), the solution temperature is increased. In the present invention, however, the reaction temperature can be adjusted to 250 to 450 ° C . In this case, the reaction temperature can be controlled by using a heating medium (for example, dibenzyltoluene or nitrite).

If the reaction temperature, that is, the temperature of the catalyst layer exceeds 450 ° C, there is a fear that the catalytic activity is rapidly lowered as the reaction continues. If the reaction temperature is lower than 250 ° C, the yield of the conjugated diene as the desired product may be lowered.

The pressure in the reactor may be greater than or equal to 0 MPaG and less than or equal to 0.5 MPaG and the residence time may be from 0.36 to 72 seconds. The ratio of the flow rate of the mixed gas to the amount of catalyst in the reactor may be 50 to 10000 h < ^-1 >.

The flow rate difference between the inlet and the outlet of the reactor depends on the flow rate of the raw material gas at the reactor inlet and the flow rate of the product gas at the reactor outlet but it is preferable that the ratio of the flow rate of the outlet to the inlet flow rate is 100 to 110% Lt; / RTI > In this manner, the conjugated diene corresponding to the monoolefin is produced by the oxidative dehydrogenation reaction of the monoolefin in the raw material gas, and the produced gas containing the conjugated diene is obtained at the outlet of the reactor. The concentration of the conjugated diene corresponding to the monoolefin in the feed gas contained in the produced gas depends on the concentration of the monoolefin contained in the feed gas, but may be 1 to 15% by volume, and the concentration of the unreacted monoolefin is 0 To 7% by volume.

The by-product contained in the product gas differs depending on the kind of the impurity contained in the raw material gas to be used. For example, it may be contained in the product gas in an amount of 0.05 to 0.50% by volume.

The oxidative dehydrogenation reaction in step a) is, for example, a conversion of 95% or more, or 96% or more. In the above range, unsaturated aldehydes present in the solution before crude butadiene separation Acrolein, butenone, and benzaldehyde) is preferably small.

The method for producing a conjugated diene of the present invention may include a cooling step, a solvent absorption step, a separation step, a purification step and the like in order to separate the conjugated diene from the product gas containing the conjugated diene, The gas becomes a compressed gas and dehydrated gas in the dehydration process. However, since these gases have the same content ratios except for water, the generated gas, compressed gas, and dehydrated gas are hereinafter sometimes referred to as " generated gas ".

In the present invention, a cooling step is carried out to cool the product gas containing the conjugated diene obtained from the reactor. Is not limited as long as it is capable of cooling the product gas obtained from the outlet of the reactor. However, for example, the product can be cooled by bringing the cooling solvent directly into contact with the product gas. As the cooling solvent, for example, water or an aqueous alkali solution can be used.

The cooling temperature of the generated gas differs depending on the temperature of the produced gas obtained from the outlet of the reactor, the kind of the cooling solvent, and the like, but is cooled to 5-100 deg. The higher the cooling temperature, the lower the construction cost and the cost of operation, and the lower the load of the process of compressing the product gas, the lower the cost. The pressure in the cooling tower is 0.03 MPaG, for example.

As a specific example, the cooling in step b) is performed by water spraying at 30-50 ° C or 35-45 ° C on the top of the cooling tower, and the bottom outlet water of the cooling tower is cooled to be recycled and partially treated with wastewater. And the bottom effluent discharged from the top of the stripping tower discharged at 10 to 30 DEG C or 15 to 25 DEG C by water jetting is allowed to stand for 1 hour or less or 40 minutes to 1 hour under reduced pressure heating to evaporate water, And recycled to the tower.

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

The product gas that is absorbed into the organic solvent after cooling in the step b) is, for example, 50% or 97.5% of the by-products of acrolein, butenone, and benzaldehyde under a non-drying agent have.

The absorption of step (b) is preferably carried out by absorbing the generated gas into the solvent to recover the conjugated diene from the viewpoint of reducing the energy cost required for the separation of the conjugated diene. In the step of absorbing the generated gas, As a specific method for making it, a spray tower, a bell tower, and a perforated plate type absorption tower can be used.

In the case of using the absorption tower, for example, a monoolefin (such as N-butene) having 4 or more carbon atoms unreacted with the conjugated diene in the product gas and a hydrocarbon having 3 or less carbon atoms The compound is absorbed into the solvent. Examples of the hydrocarbon compound having 3 or less carbon atoms include methane, acetylene, ethylene, ethane, methyl acetylene, propylene, propane, and allene.

The countercurrent flow may be formed by, for example, passing the water-cooled product gas under an absorber column and flowing the amide organic solvent through the column.

Examples of the absorption solvent include C ₆ to C ₁₀ saturated hydrocarbons, C ₆ to C ₈ aromatic hydrocarbons, and amide compounds. Specific examples thereof include dimethylformamide (DMF), toluene, xylene, N-methyl-2-pyrrolidone (NMP) and the like.

The absorption solvent may be used in a ratio of 1 to 100 by weight based on the flow rate of the target product supplied to the recovery process. The greater the amount of the absorption solvent used, the less economical and less the recovery efficiency of the conjugated diene .

The pressure inside the absorption column (absorption tower) may be, for example, 0.1-2.0 MPaG. The larger the pressure, the better the absorption efficiency, and the smaller the energy required for the pressure increase at the time of introducing the gas into the absorption tower The amount of dissolved oxygen in the liquid can be further reduced.

The temperature inside the absorber may be, for example, 0 to 50 ° C. The larger the temperature is, the less oxygen or nitrogen is absorbed in the solvent. The smaller the absorber is, the better the absorption efficiency of hydrocarbons such as conjugated diene can be.

The conjugated diene-containing solvent obtained in the solvent absorption step mainly contains the conjugated diene which is a target product, and the concentration of the conjugated diene in the solvent absorption liquid may be, for example, 1 to 20% by weight.

The higher the concentration of the conjugated diene in the solvent, the greater the amount of disappearance due to polymerization or volatilization of the conjugated diene. The lower the higher the concentration of the conjugated diene, the greater the required amount of circulation of the solvent at the same production yield, .

In the step b), the butadiene absorption rate of the discharged gas may be in the range of 99.5% or more. The butadiene absorption rate can be expressed in terms of% by mol (amount of butadiene in the solution containing butadiene discharged from the top of the solvent absorption tower) / (amount of butadiene in the exhaust gas flowing into the bottom of the solvent absorption tower) x 100.

In the step (c), the degassing process corresponds to the step of gasifying and removing nitrogen or oxygen dissolved in the solvent because a slight amount of nitrogen and oxygen are also absorbed in the solvent containing the conjugated diene.

The degassing treatment in the step c) may be performed, for example, by spraying the organic solution above the degassing tower at a feed temperature of 30 to 40 ° C.

It is possible to carry out stripping (separation step) of separating the crude conjugated diene from the solvent containing the conjugated diene obtained in the degassing step.

The stripping (separation step) is not limited as long as it can separate the crude conjugated diene from the absorption liquid of the solvent of the conjugated diene. For example, the stripping can be effected by distillation separation.

Specifically, the distillation separation is carried out by distillative separation of the conjugated diene by a reboiler and a condenser, and the purified butadiene is extracted from the column top and the absorption solvent is discharged from the bottom of the column. The discharged absorption solvent may be reused as an organic solvent in step b), for example.

The stripping can be performed, for example, by cooling the organic solution from which the residual gas has been removed by the deaeration treatment to a temperature of 20 to 30 캜 and spraying the organic solution onto the solvent separation tower.

As the distillation column, both packed column and shelf column can be used, but multi-stage distillation is preferable. In order to separate the conjugated diene from the solvent, the distillation column theoretical stage can be, for example, five or more, or 10 to 20 stages, and the distillation column having more than 50 stages can be used for the economical efficiency of the distillation column construction, On the other hand, if the number of stages is too small, separation is difficult.

For example, the purified butadiene may have a purity of 97.0% by weight or more, or 97.7% by weight or more. The solution remaining after stripping the purified butadiene can also be reused as an organic solvent in step b).

The method of producing the conjugated diene can efficiently remove the by-product in the dehydration step after the cooling step without using the desiccant. By way of example, the by-products of acrolein, butenone, and benzaldehyde may be included in an amount of 0.01 to 2 wt%, or 0.01 to 1 wt%.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the scope and spirit of the invention as disclosed in the accompanying claims. Changes and modifications may fall within the scope of the appended claims.

[Example]

Example 1

a) an oxidative dehydrogenation reaction step;

A multi-component bismuth molybdenum catalyst (composite 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) And subjected to an oxidative dehydrogenation reaction at 320 ° C while being supplied at a space velocity of 75h-1, oxygen / 1-butene = 1, steam / 1-butene = 3 and nitrogen / The produced gas was prepared. The conversion rate measured after the reaction was 98%.

b-1) cooling step

The product gas obtained in the step a) was sprayed at a flow rate of 9 kg / hr of water at a temperature of 40 캜 at the top of a quencher (a packed column of 3 m in height), and the water discharged from the bottom was cooled and circulated to the top of the cooling tower , And some of the circulating water was treated with wastewater at a flow rate of 400 g / hr.

Then, the gas discharged from the top of the quencher was introduced into an aldehyde removing column (a packed column having a height of 3.5 m), cooled at 20 ° C and a flow rate of 4.5 kg / hr at the top of the removing column, The discharged water was put into vessel (cylindrical glass vessel of 3L size) and the reduced pressure heating condition of 70 mbar / 50 캜 was maintained for about 40 minutes, and the water evaporated was further removed at a flow rate of about 100 g / hr.

The product gas obtained in the step a) and the gas at the top of the aldehyde removing tower were measured by gas chromatography (GC) and the results of the components removed from the aldehyde removing column in the included by-products are shown in Table 1 below.

b-2) Absorption step

The gas discharged from the upper part of the aldehyde removing column of the step b-1) was cooled to 30 to 35 캜 and supplied to an absorption tower (a column having a height of 7 m), and dimethylformamide (DMF ) To prepare an organic solution.

c-1) degassing step

The organic solution produced in the step b-2) was heated from the lower part of the absorption tower to the upper part of the degassing tower (the packed column having a height of 3.5 m) at a feeding temperature of 30 to 40 캜 while heating the column at a low temperature of 90 캜, The residual gas such as nitrogen and oxygen was removed while maintaining 2 bar.

c-2) Stripping step

The organic solution discharged from the bottom of the degassing tower was cooled to 20 to 30 DEG C, sprayed on top of a solvent separation tower (packed tower having a height of 3.5 m), heated to 150 DEG C, And the solvent was separated and circulated to the absorption tower of step b-2).

In addition, the butadiene-containing gas on the top of the solvent separation tower was recovered through the condenser and a trace amount of the absorption solvent, and then purified butadiene was obtained.

The purified gas was analyzed by gas chromatography (GC) to find that the purity of 1,3-butadiene was 97.5%.

Example 2

In the step (b-1) of Example 1, the reduced pressure heating conditions of the vessel were set at room temperature, 100 mbar The same experiment as in Example 1 was repeated.

Comparative Example 1

In the step (b-1) of Example 1, the reduced pressure heating condition of the vessel was set at room temperature and normal pressure

The same experiment as in Example 1 was repeated.

* Total: The content of by-products in hydrocarbon in the obtained product gas was measured by GC analysis

* After: The content of by-products of hydrocarbons in the gas at the top of the tower was measured by GC analysis

As shown in Table 1, according to Examples 1 and 2 in which the upper exhaust gas of the cooling tower of the present invention is put into the aldehyde removing column and the lower drainage water is heated under reduced pressure, the by- It was possible to efficiently remove it in the yield.

On the other hand, according to Comparative Example 1 in which the upper exhaust gas of the cooling tower was charged into the aldehyde removing column and the lower effluent was circulated under the normal pressure normal temperature condition, acrolein in the by-product was not removed at all, butenone was more than 49% Was removed by about 70%.

Claims (8)

a) preparing a product gas containing butadiene by subjecting a raw material gas containing N-butene to an oxidative dehydrogenation reaction under a catalyst; b) cooling the product gas and absorbing it in an organic solvent to produce an organic solution; And c) degassing and stripping the organic solution to obtain crude butadiene,
The cooling in step b) is carried out by water spraying at a temperature of 30-50 ° C in the upper part of the cooling tower, and then the lower outlet water of the cooling tower is cooled and recycled and partially treated with wastewater. The cooling tower top exhaust gas is introduced into the aldehyde removal tower, Wherein the distillate effluent discharged by water jetting at 30 DEG C is retained for 1 hour or less under reduced pressure heating and recirculated. The method according to claim 1,
Wherein the product gas absorbed into the organic solvent after cooling in the step b) is a product obtained by removing at least 50% of by-products of acrolein, butenone, and benzaldehyde under a non-drying agent. The method according to claim 1,
Wherein the reduced pressure heating condition is 30 to 150 mbar and 30 to 60 ° C. The method according to claim 1,
Wherein the catalyst of step a) is a molybdate-bismuth-based catalyst. 5. The method of claim 4,
Wherein the catalyst is a composite 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. The method according to claim 1,
Wherein the oxidation dehydrogenation reaction in step a) has a conversion of 95% or more. The method according to claim 1,
Wherein the organic solvent in step b) is at least one selected from the group consisting of C ₆ to C ₁₀ saturated hydrocarbons, C ₆ to C ₈ aromatic hydrocarbons, and amide compounds. The method according to claim 1,
Wherein the solution in which the crude butadiene is stripped in the step c) is reused as the organic solvent of the step b).