JP2010090082A - Method of producing conjugated diene - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of producing a conjugated diene capable of omitting an extractive distillation process for separating acetylenic hydrocarbons contained in a product gas, or of reducing the load of the extractive distillation, upon producing a conjugated diene by way of the catalytic oxidative dehydrogenation of a monoolefin. <P>SOLUTION: The method of producing a conjugated diene including a reaction process of producing a product gas comprising a corresponding conjugated diene by carrying out the oxidative dehydrogenation, in the presence of a catalyst, of a raw material gas comprising a 4C or higher monoolefin fed into a reactor together with a gas comprising molecular oxygen, is characterized in that the concentration of acetylenic hydrocarbons in the product gas is 0.016 vol% or lower. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for producing a conjugated diene, and more particularly to a method for producing a conjugated diene such as butadiene by a catalytic oxidative dehydrogenation reaction of a monoolefin having 4 or more carbon atoms such as n-butene.

A method for producing a conjugated diene such as butadiene by subjecting a monoolefin such as n-butene to an oxidative dehydrogenation reaction in the presence of a catalyst is conventionally known.
This reaction proceeds, for example, according to the following reaction formula, and water is by-produced.
C ₄ H ₈ + 1 / 2O ₂ → C ₄ H ₆ + H ₂ O

The production of butadiene by the catalytic oxidative dehydrogenation reaction of n-butene is industrially made from a C ₄ fraction (C ₄ hydrocarbon mixture, hereinafter sometimes referred to as “BB”) by-produced by naphtha cracking. In the butadiene extraction and separation process, a mixture containing 1-butene, 2-butene, butane and the like obtained by separating butadiene in an extractive distillation column (hereinafter, this mixture may be referred to as “BBSS”). ) Has been proposed for producing butadiene from butene contained therein.

Figure 2 is a representative flow diagram illustrating a butadiene extraction separation process from C ₄ fraction, C ₄ fraction is introduced into the first extractive distillation column 32 through the evaporation tower 31, extractant (dimethylformamide ( DMF) etc.) and other C ₄ components (hereinafter sometimes referred to as “BBS”) are removed by evaporation. Next, the i-butene is removed from the BBS in the i-butene separation column 33, and BBSS is discharged out of the system. The butadiene extract from the first extractive distillation column 32 is then separated in the pre-dispersion tower 34 and the first diffusion tower 35 from the extractant DMF and the like, and then introduced into the second extractive distillation tower 37 via the compressor 36. , And re-extracted with an extractant (DMF, etc.). The acetylenes separated in the second extractive distillation tower 37 are recovered as fuel through a butadiene recovery tower 38 and a second diffusion tower 39. The crude butadiene from the second extractive distillation column 37 is further purified by the first distillation column 40 and the second distillation column 41 to recover high purity 1,3-butadiene. In FIG. 2, reference numerals 200 to 219 denote piping.

Conventionally, the following techniques have been proposed as a method for producing butadiene by catalytic oxidative dehydrogenation of n-butene.
(1) After producing butadiene by a catalytic oxidative dehydrogenation reaction, by-product heavy matter is decomposed and removed by further treating the product gas at a high temperature in the presence of a specific catalyst to produce a by-product weight in the subsequent cooling step. A method of preventing pipe clogging, material contamination and corrosion due to material (Patent Document 1).
(2) A method of obtaining butadiene in a high yield at a relatively low reaction temperature from a raw material gas having a low purity of n-butene by using a specific catalyst (Patent Document 2).

  In Patent Document 1, it is described that a general catalyst such as a Mo-Bi system is used as the catalyst for the oxidative dehydrogenation reaction, and a specific production method of the catalyst is not particularly described. Patent Document 2 is characterized by using a catalyst having a specific composition. In the specific production of the catalyst, the source compounds of all the elements constituting the catalyst are mixed in an aqueous solution, and then dried. Firing is performed.

  In Patent Documents 1 and 2, no consideration is given to acetylene hydrocarbons in the product gas obtained when butadiene is produced by oxidative dehydrogenation of butene, and acetylene hydrocarbons are removed from the product gas. However, in the conventional method for producing a conjugated diene such as butadiene by the catalytic oxidative dehydrogenation reaction of a monoolefin such as n-butene, there is 0.15 to 1 vol in the raw material gas. % Of acetylenic hydrocarbon is described as a by-product, and it is suggested that acetylenes increase by oxidative dehydrogenation reaction.

In Patent Document 4, as a method for separating a relatively easily soluble hydrocarbon from a hydrocarbon mixture, a relatively easily soluble hydrocarbon containing butadiene is separated from a C ₄ hydrocarbon mixture, and further acetylene hydrocarbons are extracted and removed. To produce high purity butadiene.
More specifically, in Patent Document 4, butadiene is extracted into a solvent by extractive distillation using a solvent such as dimethylformamide or N-methyl-2-pyrrolidone from a hydrocarbon mixture having 4 carbon atoms produced by ethylene cracking. To do. Next, after butadiene is once diffused from the solvent as a gas, extractive distillation is performed again using the solvent. At this time, the operating conditions of the extractive distillation column are adjusted so that mainly acetylenic hydrocarbons of impurities are extracted into the solvent, and butadiene is obtained as a gas that has not been extracted.

The composite oxide catalyst to be described later used in the present invention is described in Patent Document 5. In this Patent Document 5, this composite oxide catalyst is used as a catalyst for producing butadiene by oxidative dehydrogenation of butene. Although there is no description of a specific method for producing butadiene, there is no suggestion about the concentration of acetylenic hydrocarbons in the product gas obtained when butadiene is produced from butene using the catalyst. Absent.
JP-A-57-140730 JP 60-1139 A JP 57-164730 A Japanese Patent Laid-Open No. 57-4926 JP 2003-220335 A

  As described above, Patent Documents 1 and 2 do not consider any acetylene hydrocarbons in the product gas obtained when butadiene is produced by oxidative dehydrogenation of butene. From the product gas, acetylene hydrocarbons are not considered. However, in the conventional method for producing a conjugated diene such as butadiene by the catalytic oxidative dehydrogenation reaction of a monoolefin such as n-butene, for example, Patent Document 3 discloses in the raw material gas Describes that acetylene-based hydrocarbons of about 0.15 to 1 vol% are contained as by-products, suggesting that acetylenes increase due to oxidative dehydrogenation reaction.

  However, since butadiene and acetylene hydrocarbons in the product gas are difficult to separate by ordinary distillation because of their close boiling points, a complicated method combining extractive distillation and emission as described in Patent Document 4 Need to be separated. In such a conventional method that combines extractive distillation and stripping, extraction efficiency is not good, so that there is a problem that an extractive distillation column of about 100 to 200 stages is required. In particular, extractive distillation must be performed not only for the extraction of butadiene as a product but also for separation of acetylenic hydrocarbons as impurities, which has led to an increase in construction costs and operation costs.

  The present invention has been made in view of the above-described conventional situation, and in a method for producing a conjugated diene such as butadiene by a catalytic oxidative dehydrogenation reaction of a monoolefin such as n-butene, the acetylene contained in the product gas It is an object of the present invention to provide a method for producing a conjugated diene that can omit the extractive distillation step for separating the hydrocarbon, or can reduce the distillation load even when the extractive distillation step is performed.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors have separated the acetylene hydrocarbon contained in the product gas by obtaining a product gas with a small amount of by-product acetylene hydrocarbon in the catalytic oxidative dehydrogenation reaction. It has been found that the extractive distillation step can be omitted or the load of this extractive distillation can be greatly reduced.

  The present invention has been achieved on the basis of such findings, and the gist thereof is as follows.

[1] A source gas containing a monoolefin having 4 or more carbon atoms and a molecular oxygen-containing gas are supplied to a reactor, and a product gas containing a corresponding conjugated diene is obtained by an oxidative dehydrogenation reaction in the presence of a catalyst. In the method for producing a conjugated diene having the reaction step to be obtained, the acetylene hydrocarbon concentration of the product gas is 0.016 vol% or less.

[2] The method for producing a conjugated diene according to [1], wherein the catalyst is a composite oxide catalyst represented by the following general formula (1).
Mo _a Bi _b Co _c Ni _{d F e} X _f Y _g Z _h Si _i O _j (1)
Wherein X is at least one element selected from the group consisting of magnesium (Mg), calcium (Ca), zinc (Zn), cerium (Ce) and samarium (Sm), and Y is sodium (Na) , Potassium (K), rubidium (Rb), cesium (Cs) and at least one element selected from the group consisting of thallium (Tl), Z is boron (B), phosphorus (P), arsenic (As) And at least one element selected from the group consisting of tungsten (W), and a to j represent atomic ratios of the respective elements, and when a = 12, b = 0.5 to 7, c = 0-10, d = 0-10 (where c + d = 1-10), e = 0.05-3, f = 0-2, g = 0.04-2, h = 0-3, i = 5 48, and j satisfies the oxidation state of other elements Numerical value is.)

[3] A method in which the composite oxide catalyst is manufactured through a process in which the source compounds of the component elements constituting the composite oxide catalyst are integrated and heated in an aqueous system, the molybdenum compound, the iron compound, A pre-process for producing a catalyst precursor by heating a raw material compound aqueous solution containing at least one selected from the group consisting of a nickel compound and a cobalt compound and silica, or a dried product obtained by drying the aqueous solution, and the catalyst precursor; The method for producing a conjugated diene according to [2], wherein the method is produced by a method comprising a step of integrating a body, a molybdenum compound and a bismuth compound together with an aqueous solvent, followed by drying and firing.

[4] From the cooling step for cooling the product gas, the recovery step for recovering the conjugated diene produced by bringing the cooled gas into contact with the solvent in the solvent, and the solution containing the conjugated diene obtained in the recovery step A method for producing a conjugated diene according to any one of [1] to [3], further comprising a separation step of separating the crude conjugated diene.

[5] Crude butadiene is obtained from the C ₄ fraction obtained by naphtha decomposition through the first extractive distillation column and the second extractive distillation column, and after removing light boiling components from the crude butadiene in the first distillation column, in butadiene extraction separation process from C ₄ fraction to obtain the purified butadiene by removing heavy boiling fraction in a distillation column, obtained by separating and removing the first extractive distillation column butadiene extraction from residue i- butene n -The method for producing a conjugated diene according to any one of [1] to [4], wherein a butene-containing gas is used as the source gas.

[6] The method for producing a conjugated diene according to [5], wherein the crude conjugated diene obtained in the separation step is sent to the first extractive distillation column for purification.

  According to the present invention, a product gas having a low acetylene hydrocarbon concentration is obtained by a catalytic oxidative dehydrogenation reaction of monoolefin, thereby omitting an extractive distillation step for separating acetylene hydrocarbons contained in the product gas. Alternatively, even when this extractive distillation step is performed, the distillation load can be greatly reduced, and the equipment construction cost and the operation cost can be reduced.

  In the present invention, the oxidative dehydrogenation reaction catalyst is preferably a composite oxide catalyst represented by the following general formula (1) (Claim 2), and this composite oxide catalyst constitutes the composite oxide catalyst. A method for producing a component compound through a step of integrating and heating a source compound of each component element in an aqueous system, wherein at least one selected from the group consisting of a molybdenum compound, an iron compound, a nickel compound, and a cobalt compound and silica An aqueous raw material compound solution or a dried product obtained by drying the same is heated, and the catalyst precursor, the molybdenum compound and the bismuth compound are integrated with an aqueous solvent, dried and fired. It is preferably produced by a method having a post-process (claim 3).

Mo _a Bi _b Co _c Ni _{d F e} X _f Y _g Z _h Si _i O _j (1)
Wherein X is at least one element selected from the group consisting of magnesium (Mg), calcium (Ca), zinc (Zn), cerium (Ce) and samarium (Sm), and Y is sodium (Na) , Potassium (K), rubidium (Rb), cesium (Cs) and at least one element selected from the group consisting of thallium (Tl), Z is boron (B), phosphorus (P), arsenic (As) And at least one element selected from the group consisting of tungsten (W), and a to j represent atomic ratios of the respective elements, and when a = 12, b = 0.5 to 7, c = 0-10, d = 0-10 (where c + d = 1-10), e = 0.05-3, f = 0-2, g = 0.04-2, h = 0-3, i = 5 48, and j satisfies the oxidation state of other elements Numerical value is.)

  Further, the method of the present invention comprises a cooling step for cooling the product gas obtained in the reaction step, and a recovery for recovering the conjugated diene produced by contacting the cooled gas with a solvent in the solvent. Preferably, the method includes a step and a separation step of separating the crude conjugated diene from the solution containing the conjugated diene obtained in the recovery step.

In addition, as a raw material gas for the method for producing a conjugated diene of the present invention, crude butadiene is obtained from a C ₄ fraction obtained by naphtha cracking through a first extractive distillation column and a second extractive distillation column, and the first from the crude butadiene. after removing the low-boiling fraction in a distillation column, in butadiene extraction separation process from C ₄ fraction to obtain the purified butadiene by removing heavy boiling component in the second distillation column, butadiene extraction residue of the first extractive distillation column It is preferable to use an n-butene-containing gas obtained by separating and removing i-butene from the component (claim 5). In this case, the crude conjugated diene obtained in the separation step is used in the extraction separation process of butadiene. It is preferable to feed the first extractive distillation column for purification (Claim 6).

  Hereinafter, embodiments of the method for producing a conjugated diene of the present invention will be described in detail. However, the description described below is an example (representative example) of an embodiment of the present invention, and the present invention is limited to these contents. Not.

  The method for producing a conjugated diene according to the present invention is performed by supplying a raw material gas containing a monoolefin having 4 or more carbon atoms and a molecular oxygen-containing gas to a reactor and performing an oxidative dehydrogenation reaction in the presence of a catalyst. In the method for producing a conjugated diene having a reaction step for obtaining a product gas containing a conjugated diene, the product gas is characterized in that an acetylene hydrocarbon concentration of the product gas is 0.016 vol% or less.

In the present invention, “acetylene hydrocarbon” is represented by the general formula C _n H _2n-2 , an unsaturated chain hydrocarbon having one triple bond, and an alkyl group in the unsaturated chain hydrocarbon. A derivative into which a substituent such as a vinyl group, a phenyl group, a cycloalkyl group, or an allyl group is introduced. The substituent is not particularly limited as long as it does not inhibit the effect of the present invention. In the production of butadiene by the catalytic oxidative dehydrogenation reaction of n-butene, acetylene hydrocarbons mainly include acetylene, methylacetylene, ethylacetylene, vinylacetylene, phenylacetylene and the like. One type or two or more types of acetylene hydrocarbons may be used.
In the following, “acetylene hydrocarbon” may be referred to as “acetylenes”.

Hereinafter, the present invention will be described in detail with reference to FIG. 1 showing a system diagram of a production process in the case of producing butadiene from n-butene according to the method for producing a conjugated diene of the present invention. Not only the production of butadiene from butene (1-butene, 2-butene), but also catalytic oxidative dehydrogenation of monoolefins having 4 or more carbon atoms, preferably 4 to 6 carbon atoms, such as pentene, methylbutene and dimethylbutene. Is effectively applied to the production of the corresponding conjugated dienes. These monoolefins do not necessarily need to be used in an isolated form, and can be used in the form of any mixture as required. For example, when 1,3-butanediene is to be obtained, high-purity 1-butene or 2-butene can be used as a raw material, but butadiene from the C ₄ fraction (BB) by-produced in the above-described naphtha decomposition. And a fraction (BBSS) mainly composed of n-butene (1-butene and 2-butene) obtained by separating i-butene and a butene fraction produced by dehydrogenation or oxidative dehydrogenation of n-butane. It can also be used. The main component as used herein refers to a component that is usually contained in an amount of 40 vol% or more, preferably 60 vol% or more, more preferably 75 vol% or more, and particularly preferably 99 vol% or more with respect to the raw material gas. Further, the source gas may contain an arbitrary impurity as long as the effects of the present invention are not impaired. Specific examples of impurities that may be contained include saturated hydrocarbons such as propane, n-butane, i-butane, and pentane, olefins such as propylene and pentene, dienes such as 1,2-butadiene, methylacetylene, and vinyl. Examples include acetylenes such as acetylene and ethylacetylene. The content of these impurities in the raw material gas is usually 60 vol% or less, preferably 40 vol% or less, more preferably 1 vol% or less. If this amount is too large, the concentration of 1-butene or 2-butene as the main raw material will decrease, and the reaction will be slow, or undesirable by-products will tend to increase.

  In FIG. 1, 1 is a reactor, 2 is a quench tower, 3, 6 and 13 are coolers (heat exchangers), 4, 7 and 14 are drain pots, 8A and 8B are dehydration towers, and 9 is a heater (heat (Exchanger), 10 is a solvent absorption tower, 11 is a degassing tower, 12 is a solvent separation tower, and 100 to 126 are pipes.

[Reaction process]
In the reaction step, a raw material n-butene or a mixture containing n-butene such as BBSS is gasified by a vaporizer (not shown) and introduced from the pipe 101 and from the pipes 102, 103, and 104. Then, nitrogen gas, air (molecular oxygen-containing gas), and water (water vapor) are introduced, and the mixed gas is heated to about 150 to 250 ° C. with a preheater (not shown), and then the catalyst is supplied from the pipe 100. The charged oxidative dehydrogenation reactor 1 is supplied. The raw material, nitrogen gas, air, and water (steam) may be supplied directly to the oxidative dehydrogenation reactor 1 through separate pipes, but may be supplied to the oxidative dehydrogenation reactor 1 in a uniformly mixed state. preferable. This is a merit that it is possible to prevent a situation in which a non-uniform mixed gas partially forms a squeal in the reactor or a raw material having a different composition is supplied to each tube in a multi-tube reactor. Because there is.

The molecular oxygen-containing gas is usually a gas containing 10 vol% or more of molecular oxygen, preferably 15 vol% or more, more preferably 20 vol% or more, and specifically preferably air. From the viewpoint of cost required for industrially preparing the molecular oxygen-containing gas, the molecular oxygen content in the molecular oxygen-containing gas is 50 vol% or less, preferably 30 vol% or less, more preferably 1 vol%. The following is preferable. In addition, the molecular oxygen-containing gas may contain an arbitrary impurity as long as the effects of the present invention are not impaired. Specific examples of impurities that may be included include nitrogen, argon, neon, helium, CO, CO ₂ , and water. In the case of nitrogen, the content of these impurities in the molecular oxygen-containing gas is usually 90 vol% or less, preferably 85 vol% or less, more preferably 80 vol% or less. In the case of components other than nitrogen, it is usually 10 vol% or less, preferably 1 vol% or less. When there is too much content of these impurities, it exists in the tendency for it to become difficult to supply oxygen required for reaction.

  Further, when supplying the raw material gas to the reactor 1, nitrogen gas and water (water vapor) may be simultaneously supplied. Nitrogen gas adjusts the concentration of flammable gas such as butene and oxygen so that the reaction gas does not form explosive gas, so water (steam) has the same concentration of flammable gas and oxygen as nitrogen gas. For reasons of adjusting and suppressing coking of the catalyst, it is preferable to supply them together with n-butene as a raw material and a molecular oxygen-containing gas to the reactor 1 as a raw material gas.

  Since the raw material gas supplied to the reactor 1 is a mixture of oxygen and combustible gas, each gas (butene, air, and, if necessary, nitrogen gas and water (water vapor) so as not to enter the explosion range) The composition at the inlet of the reactor is controlled while monitoring the flow rate with a flow meter installed in the pipe for supplying the gas), and adjusted to the following raw material gas composition, for example. The explosion range here is a range having a composition in which a mixed gas of oxygen and combustible gas is ignited in the presence of some ignition source. It is known that if the concentration of combustible gas is lower than a certain value, it will not ignite even if an ignition source is present, and this concentration is called the lower explosion limit. It is also known that if the concentration of combustible gas is higher than a certain value, it will not ignite even if an ignition source is present, and this concentration is called the upper limit of explosion. Each value depends on the oxygen concentration. In general, the lower the oxygen concentration, the closer the values are, and the two match when the oxygen concentration reaches a certain value. The oxygen concentration at this time is called a critical oxygen concentration. If the oxygen concentration is lower than this, the mixed gas will not be ignited regardless of the concentration of the combustible gas.

  When starting the reaction of the present invention, first, the amount of molecular oxygen-containing gas such as air, nitrogen, and water vapor supplied to the reactor 1 is adjusted so that the oxygen concentration at the inlet of the reactor is below the critical oxygen concentration. After that, the supply of the combustible gas is started, and then the supply amount of the combustible gas and the molecular oxygen-containing gas such as air is increased so that the combustible gas concentration becomes higher than the upper limit of explosion.

<Raw gas composition>
n- butene: _{C 4} fraction 50～100Vol% of the total
C ₄ fractions total: 5-15 vol%
O _{2: C 4} 40~120vol% relative fraction total
N _{2: C 4} 500~1000vol% relative fraction total
H ₂ O: _{C 4} fraction 90～900Vol% of the total

  The reactor 1 is filled with an after-mentioned oxidative dehydrogenation reaction catalyst, and n-butene reacts with oxygen on the catalyst to produce butadiene and water. This oxidative dehydrogenation reaction is an exothermic reaction, and the temperature rises due to the reaction. The reaction temperature is preferably adjusted to a range of 280 to 400 ° C. Therefore, the reactor 1 is appropriately cooled (for example, a heat medium (dibenzyl The temperature of the catalyst layer is controlled to be constant by removing heat with toluene or nitrite).

  The pressure in the reactor 1 is not particularly limited, but the lower limit is usually 0 MPaG or more, preferably 0.02 MPaG or more, more preferably 0.05 MPaG or more. There is an advantage that a larger amount of reaction gas can be supplied to the reactor 1 as this value increases. On the other hand, the upper limit is 0.5 MPaG or less, preferably 0.3 MPaG or less, and more preferably 0.1 MPaG. As this value becomes smaller, the explosion range tends to become narrower.

  The residence time of the reactor 1 is not particularly limited, but the lower limit is usually 0.36 seconds or longer, preferably 0.72 seconds or longer, more preferably 1.2 seconds or longer. There is a merit that the higher the value, the higher the conversion rate. On the other hand, the upper limit is 7.2 seconds or less, preferably 3.6 seconds or less, and more preferably 1.8 seconds. The smaller this value, the smaller the reactor.

  In the present invention, after the reaction is carried out in the reactor 1, the concentration of acetylenes at the outlet of the reactor in the resulting product gas is within a detection limit (about 10 ppm) or less to 0.016 vol% by gas chromatography analysis. Preferably, a product gas in the range of 0.005 to 0.01 vol% is obtained. Thus, by obtaining a product gas having a low acetylene content, a complicated extractive distillation step for removing acetylenes is unnecessary, or the load of the extractive distillation step can be reduced.

  When the concentration of acetylenes in the product gas is more than 0.016 vol%, the extractive distillation step for removing acetylenes cannot be omitted, and the load becomes large. In the present invention, it is also possible to reduce the acetylene concentration to such an extent that it cannot be detected by gas chromatography analysis. However, since it also depends on the acetylene concentration of the raw material, the lower limit of the acetylene concentration of the product gas is usually 0.005 vol%.

  Thus, in order to obtain a product gas having a low concentration of acetylenes, for example, a method using a composite oxide catalyst described later as a catalyst, a method of contacting with oxygen sufficient to react with acetylene, a treatment at a temperature of 280 ° C. or higher The method of doing is mentioned.

  The concentration of the conjugated diene corresponding to the monoolefin in the raw material gas contained in the product gas depends on the concentration of the monoolefin contained in the raw material gas, but usually 1 to 15 vol%, preferably 5 to 13 vol%, More preferably, it is 9-11 vol%. The higher the conjugated diene concentration, the lower the recovery cost, and the lower the conjugated diene, the lower the advantage that side reactions such as polymerization hardly occur when compressed in the next step. In addition, unreacted monoolefin may also be contained in the product gas, and the concentration thereof is usually 0 to 7 vol%, preferably 0 to 4 vol%, more preferably 0 to 2 vol%.

  When the composition at the inlet of the reactor 1 is above the upper explosion limit, the composition at the outlet of the reactor 1 is also usually above the upper explosion limit and there is no risk of explosion. However, in the present invention, there is a possibility that the concentration of hydrocarbons in the gas decreases and enters the explosion range in the step of bringing the produced gas into contact with an absorbing solvent and absorbing hydrocarbons such as olefins and conjugated dienes in the solvent. To avoid this, it is conceivable that the product gas is diluted with an inert gas such as nitrogen and then contacted with the absorbing solvent. It is easier to adjust the inlet conditions and reaction conditions of the vessel 1. For example, an oxygen concentration meter may be installed at the outlet of the quench tower 2, and the flow rate of air supplied to the reactor 1 or the reaction temperature may be adjusted so that the measured oxygen concentration is 8 vol% or less.

The flow rate difference between the inlet and the outlet of the reactor 1 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 the ratio of the outlet flow rate to the normal inlet flow rate is 100. -110 mol%, Preferably, it is 102-107 mol%, More preferably, it is 103-105 mol%. The outlet flow rate increases because the number of molecules increases stoichiometrically in the reaction in which butene is oxidatively dehydrogenated to produce butadiene and water, and in the reaction in which CO and CO ₂ are produced as a side reaction. A small increase in the outlet flow rate is not preferable because the reaction does not proceed, and an excessive increase in the outlet flow rate is not preferable because CO and CO ₂ increase due to side reactions.

[Cooling process]
The reaction product gas from the reactor 1 is then fed to the quench tower 2 through the pipe 105 and cooled to about 20 to 99 ° C. Cooling water is introduced into the quench tower 2 from the pipe 106, and water that has cooled the generated gas by countercurrent contact with the generated gas is discharged from the pipe 107. The cooling waste water is cooled by a heat exchanger (not shown) and is circulated again in the quench tower 2. The temperature of the cooling water depends on the cooling temperature of the reaction product gas, but is usually 10 to 90 ° C, preferably 20 to 70 ° C, more preferably 30 to 60 ° C.

[Dehydration process]
The product gas cooled in the quench tower 2 flows out from the top of the tower, and this cooling gas is then cooled to the room temperature (about 10 to 30 ° C.) through the pipe 108 through the cooler 3. The condensed water generated by cooling is separated into the drain pot 4 through the pipe 109. The water-separated gas is further pressurized to about 0.1 to 0.5 MPa by the compressor 5 through the pipe 110, and cooled again to about 10 to 30 ° C. by the cooler 6 through the pipe 111. Condensed water generated by cooling is separated from the pipe 112 into the drain pot 7. The compressed gas after the water separation is usually a wet gas having a water content of about 0.5 to 2 vol% and a dew point of about 0 to 20 ° C. This gas is introduced into the dehydration towers 8A and 8B and dehydrated. Is done.

In FIG. 1, the dehydration towers 8A and 8B are filled with a desiccant (moisture adsorbent) such as a molecular sieve, whereby dehydration of the compressed gas and regeneration by heating and drying of the desiccant are performed alternately.
That is, the compressed gas is first introduced into the dehydration tower 8A through the pipes 113 and 113a and dehydrated, and the dehydrated gas is supplied to the solvent absorption tower 10 through the pipes 114a and 114. During this time, nitrogen gas heated to about 150 to 250 ° C. is introduced into the dehydration tower 8B through the pipe 122, the heater 9, and the pipes 123 and 123b, and moisture is desorbed by heating the desiccant. The nitrogen gas containing the desorbed water is cooled to room temperature by the cooler 13 through the pipes 124 b and 124, and the condensed water is separated from the pipe 125 into the drain pot 14 and then discharged from the pipe 126.
When the desiccant in the dehydration tower 8A reaches saturation, the gas flow path is switched, the compressed gas is dehydrated in the dehydration tower 8B, and the desiccant in the dehydration tower 8A is regenerated.
The regeneration time of the desiccant in the dehydration tower in the dehydration step is not particularly limited, but is usually 6 to 48 hours, preferably 12 to 36 hours, and more preferably 18 to 30 hours.

  Although dehydration treatment by the dehydration towers 8A and 8B is not necessarily required, by performing such dehydration treatment, it is possible to prevent equipment corrosion and decomposition of the solvent due to moisture in the butadiene recovery process due to subsequent solvent absorption. ,preferable.

  Usually, in a dehydration treatment using a desiccant such as molecular sieve, the water content in the dehydrated gas supplied to the solvent absorption tower 10 can be removed to a high degree of about −50 to −60 ° C. as a dew point. .

[Recovery process]
The dehydrated gas from the dehydration towers 8A and 8B is cooled to about 10 to 30 ° C. by a cooler (not shown) as necessary, and then sent to the solvent absorption tower 10 to be supplied with the solvent from the pipe 115. By the fluid contact, butadiene in the gas and unreacted n-butene and butane are absorbed by the solvent. The component (residual gas) that has not been absorbed by the solvent is discharged from the top of the solvent absorption tower through the pipe 117 and is discarded by combustion.

  Although the pressure in the solvent absorption tower 10 is not specifically limited, Usually, 0.1-0.5 MPaG, Preferably it is 0.2-0.4 MPaG, More preferably, it is 0.25-0.35 MPaG. The larger the pressure, the better the absorption efficiency, and the smaller the pressure, the lower the construction and operation costs.

  Although the temperature in the solvent absorption tower 10 is not specifically limited, Usually, 0-50 degreeC, Preferably it is 10-40 degreeC, More preferably, it is 20-30 degreeC. The higher this temperature is, the more advantageous it is that oxygen, nitrogen and the like are less likely to be absorbed by the solvent, and the smaller, there is an advantage that the absorption efficiency of hydrocarbons such as butadiene is improved.

  The solvent absorption liquid is extracted from the bottom of the solvent absorption tower and sent to the deaeration tower 11 through the pipe 116.

  As the absorption solvent used for the recovery of butadiene in the solvent absorption tower 10, a saturated hydrocarbon having 6 to 10 carbon atoms, an aromatic hydrocarbon having 6 to 8 carbon atoms, an amide compound, or the like is used. For example, dimethylformamide (DMF), toluene, N-methyl-2-pyrrolidone (NMP), etc. can be used. The amount of the solvent used is not particularly limited, but it is uneconomical if it is too much, and the recovery efficiency of butadiene is lowered if it is too small. Therefore, it is preferable to supply the solvent in such an amount that the butadiene concentration in the obtained solvent absorbing solution is about 1 to 20% by weight, preferably about 3 to 10% by weight.

[Deaeration process]
Since some amount of nitrogen and oxygen are also absorbed in the solvent absorption liquid of butadiene obtained in the solvent absorption tower 10, this solvent absorption liquid is then supplied to the deaeration tower 11 and heated to about 50 to 150 ° C. Thus, nitrogen and oxygen dissolved in the liquid are gasified and removed. At this time, since butene, butadiene, and a part of the solvent are also gasified, they are liquefied by a capacitor provided at the top of the degassing tower 11 and recovered in the absorbing liquid. Butene and butadiene which have not been condensed are withdrawn from the pipe 118 as a mixed gas of nitrogen and oxygen, and are circulated to the inlet side of the compressor 5 and processed again in order to increase the recovery rate of butadiene. On the other hand, the degassed treatment liquid is fed to the solvent separation tower 12 through the pipe 119.

[Butadiene separation process]
In the solvent separation column 12, butadiene is distilled and separated by a reboiler and a condenser, and a butadiene fraction is extracted from the top of the column via a pipe 120. The separated solvent is extracted from the bottom of the tower through a pipe 121 and circulated and used as an absorbing solvent for the solvent absorbing tower 10.

  Although the pressure at the time of distillation of the distillation column used here can be set arbitrarily, it is usually preferred that the column top pressure is 0.05 to 0.4 MPaG. More preferably, the tower top pressure is 0.1 to 0.3 MPaG, and particularly preferably in the range of 0.15 to 0.2 MPaG. If the pressure at the top of the column is too low, a large amount of cost is required to condense the distilled butadiene at a low temperature, and if it is too high, the temperature at the bottom of the distillation column increases, resulting in an increase in steam costs. .

  The tower low temperature is usually 100 ° C to 200 ° C, preferably 120 ° C to 180 ° C, more preferably 140 ° C to 160 ° C. If the tower low temperature is too low, it will be difficult to distill butadiene from the top pressure. If the temperature is too high, the solvent will be distilled off from the top of the column. The reflux ratio may be 1 to 10, and preferably 2 to 4.

  As the distillation column, either a packed column or a plate column can be used, but multistage distillation is preferred. In order to separate butadiene and the solvent, it is preferable that the theoretical column of the distillation column is 5 or more, particularly 10 to 20 stages. A distillation column having more than 50 stages is not preferable for economics of construction of the distillation column, operational difficulty, and safety management. If the number of stages is too small, separation becomes difficult.

[Purification of crude butadiene]
The crude butadiene obtained in the butadiene separation step is usually a crude butadiene having a butadiene purity of about 40 to 98 vol% and an acetylene concentration of about 0 to 0.14 vol%.

Purified butadiene can be obtained by purifying the crude butadiene according to a conventional method. In the present invention, in particular, the butadiene is discharged from the extraction separation process of butadiene from the C ₄ fraction obtained by naphtha decomposition shown in FIG. When BBSS containing n-butene is used as a raw material gas for the catalytic oxidative dehydrogenation reaction, or when this butadiene extraction and separation process is provided close to the butadiene production process by this catalytic oxidative dehydrogenation reaction The crude butadiene obtained in the separation step is preferably supplied to the inlet side of the first extractive distillation column 32 of the extraction separation process shown in FIG. 2 and purified together with the C ₄ fraction obtained by naphtha decomposition. When pure 1-butene or 2-butene is used as a raw material for the catalytic oxidative dehydrogenation and all butene is converted into butadiene, it is supplied to the inlet side of the first distillation column 40 and supplied from the second extractive distillation column 37. Along with the crude butadiene, the light distillation component may be removed by the first distillation column 40 and then the heavy distillation component may be removed by the second distillation column 41 for purification.

That is, when the catalytic oxidative dehydrogenation reaction of n-butene is carried out according to the conventional method, the concentration of acetylenes in the product gas is usually about 0.15 to 1 vol%. Even if butadiene is separated and recovered by this method, only crude butadiene having a butadiene purity of 40 to 98 vol% and an acetylene concentration of 0.15 to 1 vol% can be obtained. Such crude butadiene requires the removal of acetylenes. Therefore, when this is supplied to the butadiene extraction and separation process shown in FIG. 2 to be purified, it is sent to the inlet side of the first extractive distillation column 32 or the pre-dispersion column 34 shown in FIG. After the butenes and the like are separated, the acetylenes must be removed by extractive distillation in the second extractive distillation column 37.
In contrast, according to the present invention, the obtained crude butadiene is fed to the inlet side of the first extractive distillation column 32 or the pre-dispersion column 34 to separate unreacted butenes and the like. Separation of acetylenes by the extractive distillation column 37 becomes unnecessary. When the C ₄ fraction (BB) is also fed to the inlet side of the first extractive distillation column 32 or the pre-dispersion column 34, the second extractive distillation column 37 cannot be omitted. The load of 37 facilities can be reduced and the apparatus can be reduced in size. As described above, when the raw material for oxidative dehydrogenation does not contain butane or isobutylene, the obtained crude butene can be fed to the first distillation column 40 at the subsequent stage of the second extractive distillation column 37.

[Composite oxide catalyst]
Hereinafter, the oxidative dehydrogenation catalyst suitably used in the present invention will be described.

The oxidative dehydrogenation reaction composite oxide catalyst used in the present invention is preferably a composite oxide catalyst represented by the following general formula (1).
Mo _a Bi _b Co _c Ni _{d F e} X _f Y _g Z _h Si _i O _j (1)
Wherein X is at least one element selected from the group consisting of magnesium (Mg), calcium (Ca), zinc (Zn), cerium (Ce) and samarium (Sm), and Y is sodium (Na) , Potassium (K), rubidium (Rb), cesium (Cs) and at least one element selected from the group consisting of thallium (Tl), Z is boron (B), phosphorus (P), arsenic (As) And at least one element selected from the group consisting of tungsten (W), and a to j represent atomic ratios of the respective elements, and when a = 12, b = 0.5 to 7, c = 0-10, d = 0-10 (where c + d = 1-10), e = 0.05-3, f = 0-2, g = 0.04-2, h = 0-3, i = 5 48, and j satisfies the oxidation state of other elements Numerical value is.)

  In addition, this composite oxide catalyst is a method of manufacturing through a step of heating the source compounds of the component elements constituting the composite oxide catalyst by integrating them in an aqueous system, and the molybdenum oxide, iron compound, nickel A pre-process for producing a catalyst precursor by heat-treating a raw material compound aqueous solution containing at least one selected from the group consisting of a compound and a cobalt compound and silica, or a dried product obtained by drying the same, and the catalyst precursor The molybdenum compound and the bismuth compound are preferably produced by a method having a post-process of integrating and drying and calcining with an aqueous solvent, and if it is a composite oxide catalyst produced by such a method, A conjugated diene such as butadiene can be produced with a high catalytic activity and a high yield, and a reaction product gas having a low acetylene content can be obtained.

  Hereinafter, a method for producing a composite oxide catalyst suitable for the present invention will be described.

In this method for producing a composite oxide catalyst, the molybdenum used in the preceding step is molybdenum corresponding to a partial atomic ratio (a ₁ ) of the total atomic ratio (a) of molybdenum, The molybdenum used is preferably molybdenum corresponding to the remaining atomic ratio (a ₂ ) obtained by subtracting a ₁ from the total atomic ratio (a) of molybdenum. The a ₁ is preferably a value satisfying 1 <a ₁ / (c + d + e) <3. Furthermore, it is preferable that a ₂ is a value satisfying 0 <a ₂ / b <8.

  Source compounds of the above component elements include oxides, nitrates, carbonates, ammonium salts, hydroxides, carboxylates, ammonium carboxylates, ammonium halides, hydrogen acids, acetylacetonates, alkoxides of the component elements. The following are mentioned as the specific example.

Examples of Mo supply source compounds include ammonium paramolybdate, molybdenum trioxide, molybdic acid, ammonium phosphomolybdate, and phosphomolybdic acid.
Examples of Fe source compounds include ferric nitrate, ferric sulfate, ferric chloride, and ferric acetate.
Examples of the Co source compound include cobalt nitrate, cobalt sulfate, cobalt chloride, cobalt carbonate, and cobalt acetate.
Examples of the Ni source compound include nickel nitrate, nickel sulfate, nickel chloride, nickel carbonate, nickel acetate and the like.
Examples of Si source compounds include silica, granular silica, colloidal silica, and fumed silica.

  Examples of Bi source compounds include bismuth chloride, bismuth nitrate, bismuth oxide, and bismuth subcarbonate. In addition, Bi component in which X component (one or more of Mg, Ca, Zn, Ce, and Sm) and Y component (one or more of Na, K, Rb, Cs, and Tl) are dissolved. It can also be supplied as a complex carbonate compound of the X component and the Y component.

For example, when Na is used as the Y component, a complex carbonate compound of Bi and Na can be obtained by dropping an aqueous solution of a water-soluble bismuth compound such as bismuth nitrate into an aqueous solution of sodium carbonate or sodium bicarbonate. The precipitate can be produced by washing with water and drying.
In addition, the complex carbonate compound of Bi and the X component is prepared by mixing an aqueous solution of a water-soluble compound such as bismuth nitrate and nitrate of the X component with an aqueous solution of ammonium carbonate or ammonium bicarbonate, etc. It can be produced by washing with water and drying.
When sodium carbonate or sodium bicarbonate is used instead of the above ammonium carbonate or ammonium bicarbonate, a complex carbonate compound with Bi, Na and X components can be produced.

Examples of source compounds of other component elements include the following.
Examples of the source compound for K include potassium nitrate, potassium sulfate, potassium chloride, potassium carbonate, and potassium acetate.
Examples of Rb source compounds include rubidium nitrate, rubidium sulfate, rubidium chloride, rubidium carbonate, and rubidium acetate.
Examples of the Cs supply source compound include cesium nitrate, cesium sulfate, cesium chloride, cesium carbonate, and cesium acetate.
Examples of Tl source compounds include thallium nitrate, thallium chloride, thallium carbonate, and thallium acetate.

Examples of the source compound for B include borax, ammonium borate, and boric acid.
Examples of P source compounds include ammonium phosphomolybdate, ammonium phosphate, phosphoric acid, phosphorus pentoxide, and the like.
Examples of the source compound for As include dialsenooctammonium molybdate, ammonium dialseno18 tungstate, and the like.
Examples of W source compounds include ammonium paratungstate, tungsten trioxide, tungstic acid, and phosphotungstic acid.

Examples of the Mg source compound include magnesium nitrate, magnesium sulfate, magnesium chloride, magnesium carbonate, and magnesium acetate.
Examples of the source compound for Ca include calcium nitrate, calcium sulfate, calcium chloride, calcium carbonate, and calcium acetate.
Examples of the Zn source compound include zinc nitrate, zinc sulfate, zinc chloride, zinc carbonate, and zinc acetate.
Examples of the Ce source compound include cerium nitrate, cerium sulfate, cerium chloride, cerium carbonate, and cerium acetate.
Examples of Sm source compounds include samarium nitrate, samarium sulfate, samarium chloride, samarium carbonate, and samarium acetate.

The raw material compound aqueous solution used in the previous step is an aqueous solution, water slurry or cake containing at least molybdenum (corresponding to a ₁ in the total atomic ratio a), iron, nickel or cobalt, and silica as a catalyst component.

  The raw material compound aqueous solution is prepared by integrating the source compound in an aqueous system. Here, the integration of each component element source compound in an aqueous system means that the aqueous solution or aqueous dispersion of each component element source compound is mixed or / and aged in stages. Say. (B) a method of mixing the above-mentioned source compounds in a lump, (b) a method of mixing the above-mentioned source compounds in a lump and aging, and (c) a method of mixing each of the above-mentioned source compounds. Supply of each component element is a method of stepwise mixing, (d) a method of repeatedly mixing and aging the above-mentioned source compounds stepwise, and a method of combining (b) to (d). It is included in the concept of integration of the source compound in an aqueous system. Here, aging refers to the processing of industrial raw materials or semi-finished products under specific conditions such as constant temperature for a certain period of time to obtain the required physical and chemical properties, increase or advance the prescribed reaction, etc. The fixed time is usually in the range of 10 minutes to 24 hours, and the fixed temperature is usually in the range of room temperature to the boiling point of the aqueous solution or aqueous dispersion.

  As a specific method of the above integration, for example, a solution obtained by mixing an acidic salt selected from catalyst components, and a solution obtained by mixing a basic salt selected from catalyst components, Specific examples include a method of adding a mixture of an iron compound and a nickel compound and / or a cobalt compound to an aqueous solution of a molybdenum compound while heating, and mixing silica.

  The raw material compound aqueous solution (slurry) containing silica thus obtained is heated to 60 to 90 ° C. and aged.

  The aging means that the catalyst precursor slurry is stirred at a predetermined temperature for a predetermined time. This aging increases the viscosity of the slurry, reduces the sedimentation of the solid components in the slurry, and is particularly effective in suppressing the heterogeneity of components in the subsequent drying process. The catalytic activity such as the raw material conversion rate and selectivity of the product catalyst becomes better.

  60-90 degreeC is preferable and the temperature in the said ripening has more preferable 70-85 degreeC. When the aging temperature is less than 60 ° C., the aging effect is not sufficient, and good activity may not be obtained. On the other hand, when it exceeds 90 ° C., the water is often evaporated during the aging time, which is disadvantageous for industrial implementation. Further, if the temperature exceeds 100 ° C., a pressure vessel is required for the dissolution tank, and handling becomes complicated, which is extremely disadvantageous in terms of economy and operability.

  The aging time is preferably 2 to 12 hours, and preferably 3 to 8 hours. If the aging time is less than 2 hours, the activity and selectivity of the catalyst may not be sufficiently developed. On the other hand, the aging effect does not increase even if it exceeds 12 hours, which is disadvantageous for industrial implementation.

  Any method can be adopted as the stirring method, and examples thereof include a method using a stirrer having a stirring blade and a method using external circulation using a pump.

  The aged slurry is subjected to heat treatment as it is or after drying. There is no particular limitation on the drying method in the case of drying and the state of the dried product to be obtained. For example, a powdery dried product may be obtained using a normal spray dryer, slurry dryer, drum dryer, etc. Alternatively, a block-like or flake-like dried product may be obtained using a normal box-type dryer or a tunnel-type firing furnace.

  The raw material salt aqueous solution or granules or cakes obtained by drying the aqueous salt solution are heat-treated in air at a temperature of 200 to 400 ° C., preferably 250 to 350 ° C. for a short time. There are no particular limitations on the type and method of the furnace at that time, and for example, it may be heated with a dry matter fixed using a normal box-type furnace, tunnel-type furnace, etc., or a rotary kiln. It is possible to heat the dried product while flowing it.

The ignition loss of the catalyst precursor obtained after the heat treatment is preferably 0.5 to 5% by weight, more preferably 1 to 3% by weight. By setting the ignition loss within this range, a catalyst having a high raw material conversion rate and high selectivity can be obtained. Note that the loss on ignition is a value given by the following equation as described above.
Burning loss (%) = [(W ₀ −W ₁ ) / W ₀ ] × 100
W ₀ : Weight (g) of the catalyst precursor after drying at 150 ° C. for 3 hours to remove adhering moisture
W ₁ : after further heat-treating the catalyst precursor excluding adhering moisture at 500 ° C. for 2 hours
Weight (g)

In a later step, the integration of the above procatalyst precursor and the molybdenum compound obtained in step (remaining a ₂ corresponds to minus a ₁ equivalent of the total atomic ratio a) and bismuth compounds, carried out in an aqueous solvent. At this time, it is preferable to add ammonia water. The addition of the X, Y, and Z components is also preferably performed in the subsequent step. Further, the bismuth source compound of the present invention is bismuth which is hardly soluble or insoluble in water. This compound is preferably used in the form of a powder. These compounds as the catalyst production raw material may be particles larger than the powder, but are preferably smaller particles in view of the heating step in which thermal diffusion should be performed. Therefore, if these compounds as raw materials are not such particles, they should be pulverized before the heating step.

  Next, the obtained slurry is sufficiently stirred and then dried. The dried product thus obtained is shaped into an arbitrary shape by a method such as extrusion molding, tableting molding or support molding. Next, this is preferably subjected to a final heat treatment for about 1 to 16 hours under a temperature condition of 450 to 650 ° C. As described above, a composite oxide catalyst having a high activity and a desired oxidation product in a high yield can be obtained.

The composite oxide catalyst thus obtained is usually packed in a reactor together with an inert ball for adjusting the reaction activity to form a fixed bed.
As the inert ball, a ceramic spherical body such as alumina or zirconia is used. The inert ball is usually the same size as the composite oxide catalyst, and its particle size is about 2 to 10 mm.

  Hereinafter, the present invention will be described more specifically with reference to examples.

[Production Example 1: Preparation of composite oxide catalyst]
Based on the description in JP-A-2003-220335, a composite oxide catalyst having the following atomic ratio was produced.
Mo: Bi: Co: Ni: Fe: Na: B: K: Si
= 12: 5: 2.5: 2.5: 0.4: 0.35: 0.2: 0.08: 24
The atomic ratio of _{a 1} and _{a 2} of molybdenum during catalyst preparation was 6.9 and 5.1 respectively.

[Example 1: Production of 1,3-butadiene]
1,3-butadiene was produced by the method shown in FIG.
The reaction tube in the reactor 1 provided with 113 reaction tubes having an inner diameter of 27 mm and a length of 3500 mm, and 1162 ml of the composite oxide catalyst produced in Production Example 1 and an inert ball (manufactured by Tipton Corp.) per reaction tube. 407 ml was charged.
BBSS discharged from the butadiene extraction and separation process from the C ₄ fraction by-produced by naphtha decomposition, air, nitrogen and water vapor are supplied at the following flow rates (per reactor reaction tube) as raw material gas After mixing and heating to 214 ° C. with a preheater, it was fed to the reactor 1. Around the reaction tube in the reactor 1, a heating medium of 320 ° C. was passed to adjust the temperature inside the reaction tube to 332 to 350 ° C.

BBSS: 13.2 capacity parts / hr
Air: 69.9 parts by volume / hr
Nitrogen: 36 parts by volume / hr
Water vapor: 22.4 parts by volume / hr
The raw material gas composition at this time is as follows.
n- butene: _{C 4} fraction 66Vol% of the total
C ₄ fractions total: 9.5 vol%
O ₂ : 111 vol% based on the total of C ₄ fractions
N ₂ : 671 vol% based on the total of C ₄ fractions
172 vol% with respect to the total of H ₂ O: C ₄ fractions

  The product gas from the reactor 1 was brought into contact with water in the quench tower 2 and cooled to 90 ° C., and further cooled to room temperature in the cooler 3.

The composition of BBSS used as a raw material and the composition of the reactor inlet gas and the reactor outlet gas (as the reactor outlet gas, the gas after cooling in the cooler 3 was sampled) were analyzed by gas chromatography, The results are shown in Table 1.
The reaction results are shown in Table 2.

[Example 2]
In Example 1, the gas flow rate introduced into the reactor was as follows, the temperature of the heat medium around the reaction tube was 278 ° C., and the temperature inside the reaction tube was 280 to 285 ° C. Butadiene was produced. Similarly, the composition of BBSS used as a raw material and the composition of the reactor inlet gas and the reactor outlet gas were analyzed by gas chromatography. The results are shown in Table 3. The reaction results are shown in Table 4.

BBSS: 13.2 capacity parts / hr
Air: 30 parts by volume / hr
Nitrogen: 64.7 parts by volume / hr
Water vapor: 20.7 parts by volume / hr
The raw material gas composition at this time is as follows.
n- butene: _{C 4} fraction 71 vol% of the total
C ₄ fractions total: 10 vol%
48.9 vol% with respect to the total of O ₂ : C ₄ fractions
N ₂ : 686 vol% with respect to the total of C ₄ fractions
161 vol% with respect to the total of H ₂ O: C ₄ fractions

  From Tables 1 to 4, according to the present invention, acetylenes such as methylacetylene and ethylacetylene contained in the raw material BBSS are reduced to below the detection limit value after the reaction, and therefore, for separation of acetylenes It can be seen that the extractive distillation step can be omitted.

  In Example 2, the butene conversion is lower than that in Example 1, but in this case as well, the concentration of acetylenes in the product gas is sufficiently low, and the effectiveness of the present invention is clear.

It is a systematic diagram which shows embodiment of the manufacturing method of the conjugated diene of this invention. It is a system diagram showing an extraction separation process butadiene from C ₄ fraction.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Reactor 2 Quench tower 3, 6, 13 Cooler 4, 7, 14 Drain pot 8A, 8B Dehydrator 9 Heater 10 Solvent absorption tower 11 Deaeration tower 12 Solvent separation tower 31 Evaporation tower 32 First extraction distillation tower 33 i-butene separation tower 34 Pre-dispersion tower 35 First dispersion tower 36 Compressor 37 Second extraction distillation tower 38 Butadiene recovery tower 39 Second dispersion tower 40 First distillation tower 42 Second distillation tower

Claims (6)

A reaction step of supplying a raw material gas containing a monoolefin having 4 or more carbon atoms and a molecular oxygen-containing gas to a reactor and obtaining a product gas containing a corresponding conjugated diene by oxidative dehydrogenation reaction in the presence of a catalyst In the method for producing a conjugated diene having
A method for producing a conjugated diene, wherein the product gas has an acetylene hydrocarbon concentration of 0.016 vol% or less. The said catalyst is a complex oxide catalyst represented by following General formula (1), The manufacturing method of the conjugated diene of Claim 1 characterized by the above-mentioned.
Mo _a Bi _b Co _c Ni _{d F e} X _f Y _g Z _h Si _i O _j (1)
Wherein X is at least one element selected from the group consisting of magnesium (Mg), calcium (Ca), zinc (Zn), cerium (Ce) and samarium (Sm), and Y is sodium (Na) , Potassium (K), rubidium (Rb), cesium (Cs) and at least one element selected from the group consisting of thallium (Tl), Z is boron (B), phosphorus (P), arsenic (As) And at least one element selected from the group consisting of tungsten (W), and a to j represent atomic ratios of the respective elements, and when a = 12, b = 0.5 to 7, c = 0-10, d = 0-10 (where c + d = 1-10), e = 0.05-3, f = 0-2, g = 0.04-2, h = 0-3, i = 5 48, and j satisfies the oxidation state of other elements Numerical value is.)   The composite oxide catalyst is a method of manufacturing through a step of heating a source compound of each component element constituting the composite oxide catalyst integrated in an aqueous system, comprising a molybdenum compound, an iron compound, a nickel compound, and A pre-process for producing a catalyst precursor by heat-treating a raw material compound aqueous solution containing at least one selected from the group consisting of cobalt compounds and silica, or a dried product obtained by drying the same, and the catalyst precursor, molybdenum The method for producing a conjugated diene according to claim 2, wherein the compound and the bismuth compound are produced together with an aqueous solvent, and are produced by a method having subsequent steps of drying and firing.   A cooling step for cooling the product gas; a recovery step for recovering the conjugated diene produced by bringing the cooled gas into contact with a solvent; and a crude conjugated diene from a solution containing the conjugated diene obtained in the recovery step. A method for producing a conjugated diene according to any one of claims 1 to 3, further comprising a separation step of separating the conjugated diene. Crude butadiene is obtained from the C ₄ fraction obtained by naphtha cracking through the first extractive distillation column and the second extractive distillation column, and light boiling components are removed from the crude butadiene in the first distillation column, and then in the second distillation column. in butadiene extraction separation process from the heavy boiling fraction C ₄ fraction to obtain the purified butadiene by removing, n- butene content obtained by separating and removing the first extractive distillation column butadiene extraction from residue i- butene The method for producing a conjugated diene according to any one of claims 1 to 4, wherein a gas is used as the source gas.   6. The method for producing a conjugated diene according to claim 5, wherein the crude conjugated diene obtained in the separation step is sent to the first extractive distillation column for purification.

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