JP2023031584A - Manufacturing method of 1,3-butadiene and manufacturing device of 1,3-butadiene - Google Patents

Abstract

To provide a manufacturing method of 1,3-butadiene capable of continuously manufacturing 1,3-butadiene with a high yield, and capable of suppressing of the occurrence of a by-product and a manufacturing device of butadiene.SOLUTION: A manufacturing method of 1,3-butadiene includes a first conversion step of bringing an ethanol-containing gas into contact with a first catalyst, converting part of the ethanol in the ethanol-containing gas into acetaldehyde, and obtaining an intermediate gas, and a second conversion step of bringing the intermediate gas, or a mixed gas obtained by mixing the intermediate gas and a gas containing the intermediate gas and ethanol into contact with a second catalyst, converting the intermediate gas or ethanol and acetaldehyde in the mixed gas into 1,3-butadiene, and obtaining a 1,3-butadiene-containing gas. A hydrogen concentration in the intermediate gas or the mixed gas is controlled to less than 15 vol.%.SELECTED DRAWING: None

Description

The present invention relates to a method for producing 1,3-butadiene and an apparatus for producing 1,3-butadiene.

Butadiene such as 1,3-butadiene is used as a raw material for styrene-butadiene rubber (SBR) and the like. As a method for producing 1,3-butadiene, for example, a first step of contacting ethanol with a first catalyst to convert ethanol to acetaldehyde, and further contacting ethanol and acetaldehyde with a second catalyst to produce 1 and a second step of converting to ,3-butadiene (US Pat.

Japanese Patent Publication No. 2017-532318

In the reaction of the first step, acetaldehyde and an equimolar amount of hydrogen are produced. When the inventors of the present application investigated a method for producing 1,3-butadiene including the first step and the second step described in Patent Document 1, the hydrogen generated in the first step caused 1, It was found that the yield of 3-butadiene decreased.

Furthermore, hydrogen at elevated temperatures is known to corrode equipment and piping made of metal in the butadiene production process. In particular, as a result of the increased frequency of contact with the flowing gas at the bent portion of the pipe, the pipe is likely to deteriorate.

An object of the present invention is to provide a method for producing 1,3-butadiene and an apparatus for producing butadiene that can continuously produce 1,3-butadiene at a high yield. and

The present invention has the following aspects.
[1] A method for producing 1,3-butadiene by continuously producing 1,3-butadiene from an ethanol-containing gas, wherein the ethanol-containing gas is contacted with a first catalyst to remove a first conversion step of converting part of ethanol to acetaldehyde to obtain an intermediate gas containing ethanol and acetaldehyde; and a mixed gas obtained by mixing the intermediate gas or the gas containing ethanol with the intermediate gas a second conversion step of contacting a second catalyst to convert ethanol and acetaldehyde in the intermediate gas or the mixed gas into 1,3-butadiene to obtain a 1,3-butadiene-containing gas. , A method for producing 1,3-butadiene, wherein the hydrogen concentration in the intermediate gas or the mixed gas is controlled to less than 15% by volume.
[2] 1, 3- according to [1], having a hydrogen concentration reduction step of reducing the hydrogen concentration in the intermediate gas or the mixed gas between the first conversion step and the second conversion step A method for producing butadiene.
[3] The hydrogen concentration reducing step includes a step of reducing the hydrogen concentration in the intermediate gas or the mixed gas by gas-liquid separation of the intermediate gas or the mixed gas. A method for producing 1,3-butadiene.
[4] In [2] or [3], wherein the hydrogen concentration reducing step includes a step of diluting the intermediate gas or the mixed gas to reduce the hydrogen concentration in the intermediate gas or the mixed gas A method for producing 1,3-butadiene as described.
[5] 1 according to any one of [1] to [4], wherein the ethanol conversion in the first conversion step is 25 to 80% and the aldehyde selectivity is 80 to 100%; A method for producing 3-butadiene.
[6] The method for producing 1,3-butadiene according to any one of [1] to [5], wherein the conversion rate of ethanol and acetaldehyde in the second conversion step is over 50%.
[7] A 1,3-butadiene production apparatus for continuously producing 1,3-butadiene from an ethanol-containing gas, comprising conversion means, wherein the conversion means brings the ethanol-containing gas into contact with a first catalyst. a first reactor for converting part of the ethanol in the ethanol-containing gas into acetaldehyde to form an intermediate gas containing ethanol and acetaldehyde; and the intermediate gas, or the intermediate gas and a gas containing ethanol. The mixed gas obtained by mixing the Production of 1,3-butadiene, comprising a second reactor and a hydrogen concentration reducing device for reducing the hydrogen concentration in the intermediate gas or the mixed gas between the first reactor and the second reactor. Device.
[8] The 1,3-butadiene according to [7], further comprising a dilution device for diluting the intermediate gas or the mixed gas with an inert gas between the first reactor and the second reactor. manufacturing equipment.
[9] further comprising purification means and a connecting pipe that connects the conversion means and the purification means, wherein the purification means is means for purifying the 1,3-butadiene-containing gas obtained by the conversion means; , The apparatus for producing 1,3-butadiene according to [7] or [8], wherein the connection pipe has at least one bend, and the bend has a radius of curvature of 20 mm or more.
[10] The apparatus for producing 1,3-butadiene according to [9], wherein the inner surface of the connecting pipe has an arithmetic average roughness of 1.02 μm or less.
[11] The apparatus for producing 1,3-butadiene according to [9] or [10], wherein the inner surface of the connecting pipe is coated with an organic compound having 6 to 12 carbon atoms.
[12] The apparatus for producing 1,3-butadiene according to any one of [9] to [11], wherein the connecting pipe has at least one bypass, and the bypass is removable.

According to the present invention, it is possible to provide a method for producing 1,3-butadiene and an apparatus for producing butadiene that can continuously produce 1,3-butadiene at a high yield.

1 is a schematic diagram of a butadiene production apparatus according to an embodiment of the present invention. FIG. 1 is a schematic diagram of a hydrogen concentration reducing device according to an embodiment of the present invention; FIG.

Embodiments of the present invention will be described in detail below, but the following description is an example of the embodiments of the present invention, and the present invention is not limited to these contents, and can be modified within the scope of the gist thereof. can do.

[Method for producing 1,3-butadiene]
The method for producing 1,3-butadiene of the present embodiment is a method for continuously producing 1,3-butadiene from an ethanol-containing gas, and is a method including the following steps B1 and B3. In the method for producing 1,3-butadiene of the present embodiment, the hydrogen concentration in the following intermediate gas or the following mixed gas is controlled to less than 15% by volume.
Step B1: A first conversion step of contacting an ethanol-containing gas with a first catalyst to convert part of the ethanol in the ethanol-containing gas into acetaldehyde to obtain an intermediate gas containing ethanol and acetaldehyde.
Step B3: contacting the intermediate gas or a mixed gas obtained by mixing the intermediate gas and a gas containing ethanol with a second catalyst to remove ethanol and acetaldehyde from the intermediate gas or the mixed gas, A second conversion step of converting to 1,3-butadiene to obtain a 1,3-butadiene-containing gas.

Step B3 is a second conversion step of contacting the mixed gas with a second catalyst to convert ethanol and acetaldehyde in the mixed gas into 1,3-butadiene to obtain a 1,3-butadiene-containing gas. In some cases, step B2 is included between steps B1 and B3.
Step B2: Mixed gas preparing step of mixing the intermediate gas obtained in the first conversion step and a gas containing ethanol to obtain a mixed gas.

The ethanol-containing gas in step B1 is not particularly limited, but an ethanol-containing gas prepared in step A below, for example, may be used.
Step A: Gas preparation step to prepare an ethanol-containing gas from an ethanol feedstock.

The 1,3-butadiene-containing gas produced in step B3 may be purified, for example, by step C below to obtain purified 1,3-butadiene.
Step C: Purification step of purifying the 1,3-butadiene-containing gas to obtain purified 1,3-butadiene.

(Process A)
Step A includes step A1 of vaporizing an ethanol feedstock under conditions of -1.0 to 3.0 MPaG in pressure and -100 to 400°C in temperature to form an ethanol-containing gas.
In this specification, a numerical range represented by "-" indicates a numerical range including numerical values before and after "-" as a lower limit and an upper limit.

The ethanol feedstock essentially contains ethanol, and may contain other components such as water as long as the effects of the present invention are not impaired. The ratio of ethanol in the ethanol feedstock is preferably 80% by mass or more, more preferably 90% by mass or more, and even more preferably 93% by mass or more, relative to the total mass of the ethanol feedstock. The upper limit of the proportion of ethanol is theoretically 100% by weight.

The ethanol feedstock is not particularly limited, and may be, for example, ethanol derived from fossils such as shale gas or petroleum, or bioethanol derived from biomass such as plants, animals, or garbage. Among them, bioethanol is preferable because it contains few impurities such as nitrogen compounds and sulfur compounds and the catalyst is less likely to deteriorate.

The pressure during vaporization of the ethanol feedstock in step A1 may be set in the range of -1.0 to 3.0 MPaG, preferably -0.5 to 2.0 MPaG, more preferably -0.3 to 1.0 MPaG. preferable. If the pressure at the time of vaporization is equal to or higher than the lower limit of the above range, the volume at the time of vaporization does not become excessive and the size of machinery and equipment can be suppressed. If the pressure at the time of vaporization is equal to or lower than the upper limit value of the above range, vaporization will be efficient.

The temperature during vaporization of the ethanol feedstock in step A1 may be set in the range of -100 to 400°C, preferably 0 to 200°C, more preferably 25 to 100°C. If the temperature at the time of vaporization is equal to or higher than the lower limit of the above range, vaporization will be efficient. Excessive heating is unnecessary if the temperature at the time of vaporization is equal to or lower than the upper limit of the above range.

In step A, if necessary, the ethanol-containing gas obtained in step A1 is mixed with one or more gases, and the concentration of ethanol in the ethanol-containing gas is adjusted within the range of 0.1 to 100% by volume. A2 may be further included.

The ethanol concentration of the ethanol-containing gas may be adjusted in the range of 0.1 to 100% by volume, preferably 10 to 100% by volume, more preferably 20 to 100% by volume. If the ethanol concentration is at least the lower limit of the above range, the yield of 1,3-butadiene is improved.
As one aspect of the present invention, the ethanol concentration in the ethanol-containing gas is preferably 0.1 to 95% by volume, more preferably 10 to 90% by volume, and even more preferably 20 to 85% by volume.

As the gas (diluent gas) to be mixed with the ethanol-containing gas, an inert gas that does not adversely affect the conversion reaction from ethanol to 1,3-butadiene can be used. Carbon dioxide can be exemplified. Among them, nitrogen gas and argon gas are preferable in terms of price and availability. The gas to be mixed with the ethanol-containing gas may be used singly or in combination of two or more.

(Step B1)
In step B1, for example, the ethanol-containing gas obtained in step A is subjected to a contact treatment with a first catalyst filled in a first reactor described later to convert part of the ethanol in the ethanol-containing gas into acetaldehyde, and ethanol and an intermediate gas containing acetaldehyde. The reaction of step B1 is represented by the following formula (1).
CH ₃ CH ₂ OH→CH ₃ CHO+H ₂ (1)

Any mode of the first reactor may be used as long as the ethanol-containing gas can be brought into contact with the first catalyst at a predetermined pressure and temperature. For example, a reaction bed is formed by filling the first catalyst in a reactor in which a heat medium is circulated in the side wall, and the supplied ethanol-containing gas is contacted with the first catalyst of the reaction bed. The reaction bed is not particularly limited, and examples thereof include fixed bed, moving bed and fluidized bed.

Two or more parallel reactors may be used in step B1. The number of reactors to be installed in parallel in step B1 can be set appropriately, and can be, for example, 2 to 5.

Any catalyst can be used as the first catalyst as long as it promotes the conversion reaction of ethanol to acetaldehyde, and examples thereof include a mixture of chromium oxide and copper oxide, zinc oxide, and a mixture of copper oxide and silicon oxide. Among them, a mixture of copper oxide and silicon oxide is preferable from the viewpoint of conversion to acetaldehyde. A 1st catalyst may be used individually by 1 type, and may use 2 or more types together.

The pressure of all gases in the first reactor during the conversion reaction in step B1 may be set in the range of 0 to 1.0 MPaG, preferably 0 to 0.5 MPaG, more preferably 0 to 0.3 MPaG. If the pressure in step B1 is equal to or higher than the lower limit of the range, the conversion of ethanol is improved. If the pressure in step B1 is equal to or lower than the upper limit of the range, liquefaction during the reaction can be suppressed.

The temperature during the conversion reaction in step B1 may be set in the range of 50 to 500°C, preferably 200 to 500°C, more preferably 250 to 350°C. When the temperature in step B1 is equal to or higher than the lower limit of the above range, the conversion of ethanol is improved. When the temperature in step B1 is equal to or lower than the upper limit of the range, excessive energy consumption can be suppressed.

In the present invention, the gas hourly space velocity (GHSV) is obtained by dividing the gas volume flow rate in terms of standard conditions by the volume of the catalyst. The gas hourly space velocity of the ethanol-containing gas with respect to the first catalyst is preferably 1000 to 20000 h ^-1 , more preferably 2000 to 15000 h ^-1 and even more preferably 3000 to 10000 h ^-1 in terms of standard conditions. When the GHSV is equal to or higher than the lower limit, the ethanol-containing gas processing capacity is increased. When the GHSV is equal to or less than the upper limit, the ethanol conversion rate is improved.

The GHSV of ethanol in the ethanol-containing gas for the first catalyst is preferably 500 to 20,000 h ⁻¹ , more preferably 1,000 to 15,000 h ⁻¹ , still more preferably 1,500 to 10,000 h ⁻¹ in terms of standard conditions. When the GHSV is equal to or higher than the lower limit, the ethanol-containing gas processing capacity is increased. When the GHSV is equal to or less than the upper limit, the ethanol conversion rate is improved.

The weight hourly space velocity (WHSV) of ethanol in the ethanol-containing gas with respect to the metal species of the first catalyst is preferably 20,000 to 500,000 h ^-1 , more preferably 50,000 to 450,000 h ^-1 , and 100,000 to 400,000 h ^-1 . More preferred. When the WHSV is equal to or higher than the lower limit, the ethanol-containing gas processing capacity is increased. When the WHSV is equal to or less than the upper limit, the conversion of ethanol improves.
WHSV can be obtained as follows. The content of the element of the metal species contained in the first catalyst is measured by an inductively coupled plasma atomic emission spectrometer or the like, and calculated in terms of oxide. For example, the above chromium oxide is converted to Cr ₂ O ₃ , copper oxide to CuO, zinc oxide to ZnO, and silicon oxide to SiO ₂ . WHSV is obtained by dividing the flow rate of ethanol in the ethanol-containing gas (unit: kg/h) by the mass of the metal species contained in the first catalyst in terms of oxide (unit: kg). can be done.

The ethanol conversion rate in step B1 is preferably 25 to 80%, more preferably 30 to 60%, even more preferably 40 to 50%.
The “conversion rate of ethanol” in step B1 is the number of moles per unit time of ethanol in the ethanol-containing gas supplied to the reactor in step B1, and the ethanol consumed in the reactor per unit time. means the ratio (percentage) of the number of moles of The number of moles per unit time of ethanol consumed in the reactor of step B1 is calculated from the number of moles per unit time of ethanol in the ethanol-containing gas supplied to the reactor of step B1 from the reactor of step B1. It is calculated by subtracting the number of moles per unit time of ethanol in the discharged intermediate gas.

The acetaldehyde selectivity of the conversion reaction in step B1 is preferably 80 to 100%, more preferably 90 to 100%. The “acetaldehyde selectivity” in step B1 refers to the ratio of the number of moles of ethanol converted to acetaldehyde per unit time to the number of moles per unit time of ethanol consumed in the reactor of step B1 ( percentage).
By-products that can be contained in the intermediate gas obtained in step B1 include crotonaldehyde, butyraldehyde, ethyl acetate, acetic acid, and the like.

The yield of acetaldehyde in the conversion reaction of step B1 is preferably 25-80%, more preferably 30-70%. The "yield of acetaldehyde" in step B1 means "conversion rate of ethanol" x "selectivity of acetaldehyde". When the yield of acetaldehyde is equal to or less than the upper limit, the amount of hydrogen produced decreases, the concentration of hydrogen in the intermediate gas or mixed gas described later decreases, and as a result the yield of 1,3-butadiene increases. .

(Step B2)
In step B2, the intermediate gas obtained in step B1 and a gas containing ethanol are mixed to obtain a mixed gas. Process B2 is performed between process B1 and process B3.

The molar ratio of ethanol to acetaldehyde in the mixed gas (ethanol/acetaldehyde) is preferably 1 to 100, more preferably 1 to 50, even more preferably 1 to 20, even more preferably 1 to 10, especially 1 to 5. preferable. When the molar ratio is within the above range, the yield of 1,3-butadiene is improved.

In step B2, based on the results of monitoring the molar ratio (ethanol/acetaldehyde) in the intermediate gas obtained in the first conversion step with an analyzer, the shortage of ethanol is increased so as to achieve the optimum reaction ratio. A gas containing ethanol is mixed with the intermediate gas. The ethanol-containing gas includes a portion of the ethanol-containing gas obtained in step A and a portion of the ethanol-containing gas supplied from another source. This makes it easier to control the molar ratio (ethanol/acetaldehyde) within the above range.
The analyzer is installed between the point where step B2 is performed and the inlet of the second reactor in step B3 described later, and the molar ratio (ethanol/aldehyde) of the gas supplied to the second reactor over time is measured. analyse. As a result, any change in gas flow rate, such as a change in each gas flow rate over the entire butadiene production process and a change in each gas flow rate due to deterioration of the catalyst and/or equipment over time, can be constantly observed.
Examples of analyzers include process mass spectrometers and gas analyzers.

(Step B3)
In step B3, the intermediate gas obtained in step B1 or the mixed gas obtained in step B2 is contacted with a second catalyst filled in a second reactor described later, and the intermediate gas or the mixed gas of ethanol and acetaldehyde are converted to 1,3-butadiene to obtain a 1,3-butadiene-containing gas. The reaction of step B3 is represented by the following formula (2).
CH ₃ CH ₂ OH+CH ₃ CHO→CH ₂ =CH-CH=CH ₂ +2H ₂ O (2)

As the aspect of the second reactor in step B3, the same aspects as those exemplified in the first reactor can be exemplified. In step B3, as in step B1, two or more parallel reactors may be used. The number of reactors to be installed in parallel in step B3 can be set appropriately, and can be, for example, 2 to 5.

Any catalyst can be used as the second catalyst as long as it promotes the conversion reaction of ethanol and acetaldehyde to 1,3-butadiene. Examples include tantalum, zirconium, niobium, hafnium, magnesium, zinc, and silicon. Among them, hafnium is preferable from the viewpoint of yield of 1,3-butadiene. A 2nd catalyst may be used individually by 1 type, and may use 2 or more types together.
Examples of the aspect of using the second catalyst include metals, oxides, and chlorides, and examples of using the second catalyst by supporting it on a carrier and using a mixture of two or more thereof can be exemplified.

The pressure of all gases in the second reactor during the conversion reaction in step B3 may be set in the range of 0 to 1.0 MPaG, preferably 0 to 0.5 MPaG, more preferably 0 to 0.3 MPaG. If the pressure in step B3 is at least the lower limit of the above range, the yield of 1,3-butadiene is improved. If the pressure in step B3 is equal to or lower than the upper limit of the above range, it is possible to suppress the decrease in yield of 1,3-butadiene due to excessive reaction.

The temperature during the conversion reaction in step B3 may be set in the range of 50 to 500°C, preferably 300 to 400°C, more preferably 320 to 370°C. If the temperature in step B3 is at least the lower limit of the above range, the yield of 1,3-butadiene is improved. If the temperature in step B3 is equal to or lower than the upper limit of the above range, it is possible to suppress the decrease in the yield of 1,3-butadiene due to overreaction.

The GHSV of the intermediate gas or the mixed gas with respect to the second catalyst is preferably 100 to 5000 h ⁻¹ , more preferably 200 to 4000 h ⁻¹ and even more preferably 400 to 3000 h ⁻¹ in terms of standard conditions. When the GHSV is equal to or higher than the lower limit value, the intermediate gas or the mixed gas can be treated with high performance. When the GHSV is equal to or less than the upper limit, the conversion rate of ethanol and acetaldehyde is improved.

The total GHSV of ethanol and acetaldehyde in the intermediate gas or mixed gas for the second catalyst is preferably 100 to 3000 h ^-1 , more preferably 200 to 2500 h ^-1 , and 400 to 2000 h ^-1 in terms of standard conditions. More preferred. When the GHSV is equal to or higher than the lower limit value, the intermediate gas or the mixed gas can be treated with high performance. When the GHSV is equal to or less than the upper limit, the conversion rate of ethanol and acetaldehyde is improved.

The conversion of ethanol and acetaldehyde in step B3 is preferably over 50%, more preferably over 60%, even more preferably over 70%.
The "conversion rate of ethanol and acetaldehyde" in step B3 refers to the number of moles per unit time of ethanol and acetaldehyde in the intermediate gas or mixed gas supplied to the reactor in step B3. means the molar ratio of the number of moles of ethanol and acetaldehyde consumed per unit time. The number of moles per unit time of ethanol and acetaldehyde consumed in the reactor of step B3 is the number of moles per unit time of ethanol and acetaldehyde in the intermediate gas or the mixed gas supplied to the reactor of step B3. from the number of moles per unit time of ethanol and acetaldehyde in the 1,3-butadiene-containing gas discharged from the reactor in step B3.

The selectivity of 1,3-butadiene in the conversion reaction of step B3 is preferably greater than 60%, more preferably greater than 70%, and even more preferably greater than 80%. The “1,3-butadiene selectivity” in step B3 refers to the number of moles per unit time of ethanol and acetaldehyde consumed in the reactor in step B3, and ethanol converted to 1,3-butadiene. and the ratio (percentage) of the number of moles of acetaldehyde per unit time.

The yield of 1,3-butadiene in the conversion reaction of step B3 is preferably 40 to 90%, more preferably 50 to 90%, even more preferably 60 to 90%. The “yield of 1,3-butadiene” in step B3 means “conversion rate of ethanol and acetaldehyde”דselectivity of 1,3-butadiene”.

Preferably, 65-100% of the acetaldehyde is converted to 1,3-butadiene in step B3.
By-products that can be contained in the 1,3-butadiene-containing gas obtained in step B3 include ethylene, propylene, diethyl ether, ethyl acetate, butanol, hexanol, 1-butene, 2-butene, isobutene, pentene, pentadiene, and hexene. , hexadiene and the like.

When the reaction results such as the conversion rate of ethanol and acetaldehyde are shown under the reaction conditions as described above, it means that the activity of the second catalyst is very high. When such a highly active second catalyst is used, when the second catalyst contains a metal oxide, the reactivity of the metal oxide not only to ethanol and acetaldehyde but also to hydrogen is increased. As a result of studies by the inventors of the present application, when a second catalyst containing a metal oxide and having a very high activity is used, the reactivity of the metal oxide to hydrogen becomes too high, and the metal oxide becomes more active. It has been found that a problem arises that the activity of the second catalyst is lowered due to the reduction to a metal having a low molecular weight. Furthermore, the addition of hydrogen activated by the metal oxide to the double bond of 1,3-butadiene produced in step B3 causes a problem of increased production of by-products such as butene. was also found. That is, the inventors of the present application have found that when a second catalyst containing a metal oxide and having a very high activity is used and the hydrogen concentration in the intermediate gas or the mixed gas is high, the yield of butadiene decreases. I learned something new.

In the method for producing 1,3-butadiene of the present embodiment, the hydrogen concentration in the intermediate gas or the mixed gas in step B3 is controlled to less than 15% by volume. The hydrogen concentration is preferably 10% by volume or less, more preferably 5% by volume or less. When the hydrogen concentration is less than the upper limit, the yield of 1,3-butadiene is improved.

An example of a method for controlling the hydrogen concentration is to set the yield of aldehyde in step B1 to the upper limit value or less. It can also be controlled by the dilution ratio in step A2.
In this embodiment, it is preferable to provide a hydrogen concentration reduction step between the steps B1 and B3 to control the hydrogen concentration in the intermediate gas or the mixed gas. The hydrogen concentration reduction step is not particularly limited, but includes, for example, one or more of the following steps B4-1 to B4-4.
Step B4-1: A hydrogen concentration reduction step of condensing a portion of the intermediate gas or the mixed gas to separate gas and liquid to reduce the hydrogen concentration in the intermediate gas or the mixed gas.
Step B4-2: A hydrogen concentration reduction step of diluting the intermediate gas or the mixed gas to reduce the hydrogen concentration in the intermediate gas or the mixed gas.
Step B4-3: A hydrogen concentration reduction step of gas-separating the intermediate gas or the mixed gas with a gas separator to reduce the hydrogen concentration in the intermediate gas or the mixed gas.
Step B4-4: A step of reducing the hydrogen concentration in the intermediate gas or the mixed gas by gas-liquid separation using a scrubber to reduce the hydrogen concentration in the intermediate gas or the mixed gas.

(Step B4-1)
In step B4-1, gas-liquid separation is performed by condensing a part of the intermediate gas obtained in step B1 or the mixed gas obtained in step B2, and the hydrogen concentration in the intermediate gas or the mixed gas to reduce

By gas-liquid separation, it can be separated into a liquid containing ethanol and acetaldehyde and a gas containing hydrogen. In this case, the liquid containing ethanol and acetaldehyde is heated, vaporized again, and supplied to the second reactor as an intermediate gas or mixed gas. The separated hydrogen-containing gas may be used as it is for another application, and ethanol, acetaldehyde, and butadiene contained in minute amounts may be recovered by distillation or the like.
Conditions for gas-liquid separation for separating a gas containing hydrogen from an intermediate gas or mixed gas are preferably conditions of pressure of 0 to 1.0 MPaG and temperature of 0°C to 100°C.

(Step B4-2)
In step B4-2, the intermediate gas obtained in step B1 or the mixed gas obtained in step B2 is diluted to reduce the hydrogen concentration in the intermediate gas or the mixed gas.

In step B4-2, based on the result of monitoring the hydrogen concentration in the intermediate gas obtained in step B1 or the mixed gas obtained in step B2 with a hydrogen analyzer, the hydrogen concentration is less than 15% by volume. diluent with diluent gas. Examples of the diluent gas include the diluent gas exemplified in step A2.

(Step B4-3)
In step B4-3, the intermediate gas obtained in step B1 or the mixed gas obtained in step B2 is separated by a gas separator to reduce the hydrogen concentration in the intermediate gas or mixed gas.

Gas separators include, for example, cryogenic (cryogenic) separators, pressure swing adsorption (PSA) separators, membrane separation separators, temperature swing adsorption (TSA) separators, metal ion (e.g., copper ions) and organic ligands (e.g., 5-azidoisophthalic acid) are combined into a separator using a porous coordination polymer (PCP), and separation using amine absorption. It can be configured using one or two or more of the vessels and the like.

(Step B4-4)
In step B4-4, the intermediate gas obtained in step B1 or the mixed gas obtained in step B2 is gas-liquid separated by a scrubber to reduce the hydrogen concentration in the intermediate gas or the mixed gas.

In the separation by a scrubber, the intermediate gas obtained in step B1 or the mixed gas obtained in step B2 is scrubbed with a solvent such as ethanol or acetaldehyde to obtain a liquid containing ethanol and acetaldehyde and a gas containing hydrogen. can be separated into In this case, a liquid containing ethanol, acetaldehyde, and a solvent is heated, vaporized again, and supplied to the second reactor as an intermediate gas or mixed gas.

The hydrogen analyzer is installed between the outlet of the first reactor in step B1 and the inlet of the second reactor in step B3, and the intermediate gas or the mixed gas supplied to the second reactor over time Analyze the hydrogen concentration in the When it is desired to analyze the hydrogen concentration in the mixed gas, a hydrogen analyzer is installed between the place where step B2 is performed and the inlet of the second reactor in step B3.
Examples of hydrogen analyzers include in-line hydrogen analyzers, thermal conductivity hydrogen analyzers, process mass spectrometers, gas analyzers, and the like.
When both steps B4-1 and B4-2 are performed, step B4-2 is preferably performed after step B4-1. When both steps B4-2 and B4-4 are performed, step B4-2 is preferably performed after step B4-4. When all steps B4-1 to B4-4 are performed, it is preferable to perform step B4-4, step B4-1, step B4-3, and step B4-2 in this order. That is, step B4-2 is preferably performed last.

(Process C)
Step C includes at least one step selected from the group consisting of steps C1 to C4 below.
Step C1: Butene (1-butene, 2-butene, isobutene) in the 1,3-butadiene-containing gas is subjected to a dehydrogenation reaction to convert to 1,3-butadiene.
Step C2: A 1,3-butadiene-containing liquid is obtained by separating a hydrogen-containing gas from a 1,3-butadiene-containing gas by gas-liquid separation.
Step C3: The liquefied product of 1,3-butadiene-containing gas or the 1,3-butadiene-containing liquid is distilled to separate into ethylene-containing gas, 1,3-butadiene-containing effluent and acetaldehyde-containing liquid.
Step C4: The acetaldehyde-containing liquid is distilled and separated into an acetaldehyde-containing gas and a residual liquid containing water.

In general, 1-butene, 2-butene and isobutene are difficult to separate from 1,3-butadiene by distillation or the like. In step C1, 1-butene, 2-butene and isobutene are dehydrogenated and converted to 1,3-butadiene, thereby increasing the proportion of 1,3-butadiene. In the method for producing 1,3-butadiene of the present embodiment, the hydrogen concentration in the intermediate gas or the mixed gas is controlled to less than 15% by volume, so the production of 1-butene, 2-butene, and isobutene is suppressed. be done.

When both the process C1 and the process C3 are performed in the process C, the process C1 may be performed before the process C3, and the process C1 may be performed after the process C3.
In step C1, for example, the 1,3-butadiene-containing gas obtained in step B3 or the 1,3-butadiene-containing effluent obtained in step C3 is fed to a third reactor, and in the presence of a third catalyst, pressure 1-butene, 2-butene and isobutene are dehydrogenated under the conditions of −1.0 to 1.0 MPaG and a temperature of 200 to 550° C. to convert them to 1,3-butadiene.
As the embodiment of the third reactor in step C1, the same embodiments as those exemplified for the first reactor can be exemplified.

Any catalyst can be used as the third catalyst as long as it promotes the dehydrogenation reaction of 1-butene, 2-butene and isobutene, and examples thereof include molybdenum, tungsten, bismuth, tin, iron and nickel. Among them, molybdenum is preferable from the viewpoint of yield of 1,3-butadiene. A 3rd catalyst may be used individually by 1 type, and may use 2 or more types together.

The pressure during the dehydrogenation reaction in step C1 may be set in the range of -1.0 to 1.0 MPaG, preferably -0.5 to 0.5 MPaG, more preferably -0.3 to 0.3 MPaG. .
If the pressure in step C1 is at least the lower limit of the above range, the yield of 1,3-butadiene is improved. If the pressure in step C1 is equal to or lower than the upper limit of the above range, it is possible to suppress the decrease in the yield of 1,3-butadiene due to excessive reaction.

The temperature during the dehydrogenation reaction in step C1 may be set in the range of 200 to 550°C, preferably 300 to 500°C, more preferably 300 to 450°C. If the temperature in step C1 is at least the lower limit of the above range, the yield of 1,3-butadiene is improved. If the temperature in step C1 is equal to or lower than the upper limit of the above range, it is possible to suppress the decrease in the yield of 1,3-butadiene due to excessive reaction.

In step C2, the 1,3-butadiene-containing gas obtained in step B3 or the 1,3-butadiene-containing gas after step C1 is subjected to gas-liquid separation to separate the hydrogen-containing gas into 1,3-butadiene-containing gas. - to obtain a butadiene-containing liquid. When the ethanol-containing gas, the intermediate gas, or the mixed gas is diluted with a diluent gas such as nitrogen gas in steps A2 and B4-2, the diluent gas is separated together with the hydrogen gas in step C2.
The conditions for the gas-liquid separation of the 1,3-butadiene-containing gas are preferably a pressure of 0 to 1.0 MPaG and a temperature of 0 to 100°C.

In step C3, the liquefied 1,3-butadiene-containing gas obtained in step B3, the liquefied 1,3-butadiene-containing gas after step C1, or the 1,3-butadiene-containing liquid after step C2 is supplied to the distillation column. and distill. This separates the ethylene-containing gas, the 1,3-butadiene-containing effluent and the acetaldehyde-containing liquid. More specifically, for example, using a plate distillation column or a packed distillation column, an ethylene-containing gas is extracted from the top of the column, an acetaldehyde-containing liquid is extracted from the bottom of the column, and a 1,3-butadiene-containing effluent is extracted from the intermediate portion. pull out. In step C3, two distillation columns are used, the ethylene-containing gas is separated in the first distillation column, and the 1,3-butadiene-containing effluent and the acetaldehyde-containing liquid are separated in the second distillation column. good too.

Ethylene-containing gas includes propylene, methane, ethane, etc. in addition to ethylene. When the liquefied 1,3-butadiene-containing gas obtained in step B3 is distilled without performing step C1, hydrogen gas and diluent gas such as nitrogen gas are separated together with the ethylene-containing gas in step C3.
The acetaldehyde-containing liquid includes not only acetaldehyde but also ethanol, water, and the like.

When step C3 is performed without step C2, the hydrogen-containing gas is also separated in step C3 together with the ethylene-containing gas. Further, when the ethanol-containing gas, the intermediate gas, or the mixed gas is diluted with a diluent gas such as nitrogen gas in steps A2 and B4-2, the diluent gas is separated together with the ethylene-containing gas in step C3. be done.

In step C4, the acetaldehyde-containing liquid obtained in step C3 is supplied to a distillation column and separated into an acetaldehyde-containing gas and a residual liquid containing water.
When performing Steps C3 and C4 in Step C, the method is not limited to performing Steps C3 and C4 separately, and Steps C3 and C4 may be performed at once in one distillation column.

The content of acetaldehyde in the acetaldehyde-containing gas obtained in step C4 is preferably 10% by volume or more, more preferably 20% by volume or more, and even more preferably 40% by volume or more. If the content of acetaldehyde is at least the above lower limit, the amount of by-products contained is small, so recovery of acetaldehyde and reuse of the acetaldehyde-containing gas are facilitated, improving economic efficiency.
The purity of the purified 1,3-butadiene obtained in step C is preferably 95.0% by mass or higher, more preferably 99.0% by mass or higher, and even more preferably 99.5% by mass or higher.
In this embodiment, the purifying steps of Steps C3 and C4 can provide a 1,3-butadiene- and acetaldehyde-containing gas with higher purity.

[Apparatus for producing 1,3-butadiene]
The 1,3-butadiene production apparatus of the present embodiment is a production apparatus for continuously producing 1,3-butadiene from an ethanol-containing gas. By using the apparatus for producing 1,3-butadiene of the present embodiment, the above-described method for producing 1,3-butadiene can be carried out.
The apparatus for producing 1,3-butadiene of the present invention comprises conversion means. The apparatus for producing 1,3-butadiene of the present invention may further comprise gas preparation means and purification means. Further, the apparatus for producing 1,3-butadiene of the present invention may comprise a connecting pipe that connects the conversion means and the purification means.

The gas preparation means is the means for step A and comprises a vaporizer for vaporizing the ethanol feedstock into an ethanol-containing gas. Any known vaporizer can be used as long as it can vaporize the ethanol feedstock.

The conversion means is a means for steps B1 to B3 and steps B4-1 to B4-4, and comprises a first reactor for carrying out step B1, a second reactor for carrying out step B3, A hydrogen concentration reducing device and/or a diluting device for performing steps B4-1 to B4-4 are provided between the first reactor and the second reactor. Any reactor can be used as long as it can bring the gas into contact with the catalyst at a predetermined pressure and temperature. For example, a reaction bed is formed by filling a catalyst in a reactor in which a heat transfer medium is circulated in the side wall, and the supplied gas is brought into contact with the catalyst in the reaction bed. The reaction bed is not particularly limited, and examples thereof include fixed bed, moving bed and fluidized bed. Examples of the hydrogen concentration reducing device include a gas-liquid separator, a gas separator, a scrubber, and the like.

The conversion means may comprise two or more parallel first reactors. The conversion means may comprise two or more parallel secondary reactors.

The purifying means is a means for Step C, and includes equipment capable of purifying a 1,3-butadiene-containing gas, such as a gas-liquid separator, a distillation column, or a reactor.
Step C1 can be carried out by the purification means having a reactor. The step C2 can be carried out by providing the purification means with a gas-liquid separator. Steps C3 and C4 can be carried out by providing the purification means with a distillation column. The purification means may comprise one of the devices described above alone, or may be a combination of two or more devices.

[Embodiment]
Hereinafter, specific examples of the method and apparatus for producing 1,3-butadiene of the present embodiment will be described. FIG. 1 is a schematic diagram of a 1,3-butadiene production apparatus 100 (hereinafter also referred to as "production apparatus 100") of the present embodiment. It should be noted that the dimensions and the like of the drawings illustrated in the following description are only examples, and the present invention is not necessarily limited to them, and can be implemented with appropriate changes within the scope of not changing the gist of the present invention. .

(Manufacturing equipment)
The manufacturing apparatus 100 includes gas preparation means 1 , conversion means 2 and purification means 3 .
The gas preparation means 1 includes a raw material container 102 , a vaporizer 104 , and a dilution gas container 106 . The conversion means 2 includes a first reactor 108 , a hydrogen concentration reducing device 109 and a second reactor 110 . The purification means 3 includes a gas-liquid separator 112 , a first distillation column 114 , a third reactor 116 , a second distillation column 118 and a recovery section 120 .

The raw material container 102 and the vaporizer 104 are connected by the pipe 10 . A flow indicator controller 11 is provided in the pipe 10 . Vaporizer 104 and first reactor 108 are connected by pipe 12 . The piping 12 is provided with a pressure indicator controller 14 for adjusting the flow rate based on the pressure in the vaporizer 104, a mixer 16, a heat exchanger 18, a temperature indicator controller 20, and a valve 22 in this order from the vaporizer 104 side. ing. The diluent gas container 106 is connected by a pipe 24 between the pressure indicating controller 14 and the mixer 16 in the pipe 12 . A flow indicator controller 26 is provided in the pipe 24 .

The two or more parallel first reactors 108 and the hydrogen concentration reduction device 109 are connected by a pipe 28 branched on the first reactor 108 side. A valve 30 is provided at each branched portion of the pipe 28 on the first reactor 108 side. The hydrogen concentration reducing device 109 and two or more parallel second reactors 110 are connected by a pipe 29 branched on the second reactor 110 side. A valve 32 is provided at each branch portion of the pipe 29 on the side of the second reactor 110 . An analyzer 34 is provided in the pipe 28 . Further, a pipe 36 is provided that branches from between the vaporizer 104 and the pressure indicator regulator 14 of the pipe 12 and is connected between the branch portion of the pipe 28 on the side of the first reactor 108 and the analyzer 34. . The pipe 36 is provided with a flow rate indicator adjuster 38 so that the flow rate of the pipe 36 can be adjusted based on the analysis result of the analyzer 34 . A pipe 29 is provided with a mixer 33 and an analyzer 35 in this order. Further, a pipe 37 is provided which branches from between the diluent gas storage portion 106 and the flow indicator controller 26 of the pipe 24 and is connected between the hydrogen concentration reducing device 109 of the pipe 29 and the analyzer 35 . The pipe 37 is provided with a flow rate indicator adjuster 27 so that the flow rate of the pipe 37 can be adjusted based on the analysis result of the analyzer 35 . The hydrogen concentration reduction device 109 is the hydrogen concentration reduction device 109-1 in which the heat exchanger 130, the gas-liquid separator 132, and the vaporizer 138 are installed in this order when step B4-1 is performed (FIG. 2). . The gas-liquid separator 132 is connected to the pipe 28 and the heat exchanger 130 is provided on the pipe 28 . The gas-liquid separator 132 is connected with a pipe 134 . The gas-liquid separator 132 and vaporizer 138 are connected by a pipe 136 . Vaporizer 138 is connected to pipe 29 . When performing step B4-3, a gas separator and a hydrogen concentration reduction device 109-2 (not shown) equipped with a pipe for discharging gas containing hydrogen, and when performing step B4-4, a scrubber, a vaporizer is the hydrogen concentration reducing device 109-3 (not shown) installed in this order. Note that any one or more of the hydrogen concentration reducing devices 109-1 to 109-3 may be provided.

Two or more parallel second reactors 110 and gas-liquid separators 112 are connected by connecting pipes 40 . In this embodiment, the connection pipe 40 is a connection pipe that connects the conversion means and the purification means. A valve 42 is provided at each branch portion of the connecting pipe 40 on the side of the second reactor 110 , and a heat exchanger 44 is provided at a position closer to the gas-liquid separator 112 . Between the valve 42 of the connection pipe 40 and the heat exchanger 44, three bends R1, R2, R3 are provided. Although there are three bent portions in this embodiment, the number of bent portions is not particularly limited. For example, the number of bends may be 0-20 or 1-10. A bypass 41 is provided in parallel with the connection pipe 40 , and a valve 45 is provided at each branch of the bypass 41 . A valve 43 is provided in a portion of the connecting pipe 40 parallel to the bypass 41 . The portion sandwiched between the valves 45 of the bypass 41 is removable. The portion sandwiched by the valve 43 of the connecting pipe 40 is detachable.
Gas-liquid separator 112 and first distillation column 114 are connected by pipe 46 . The pipe 46 is provided with a pump 48 and a level indicator adjuster 50 for adjusting the flow rate based on the liquid level in the gas-liquid separator 112 in this order from the gas-liquid separator 112 side.

A pipe 52 is connected to the top of the first distillation column 114 . Further, a pipe 54 that is connected to the gas phase portion of the gas-liquid separator 112 and merges with the pipe 52 is provided.
An intermediate portion of the first distillation column 114 and the third reactor 116 are connected by a pipe 56 .
The third reactor 116 and recovery section 120 are connected by a pipe 58 .

The bottom of first distillation column 114 and second distillation column 118 are connected by pipe 60 .

As the connection pipe 40 described above, a steel pipe made of stainless steel having corrosion resistance and heat resistance can be used. As the bypass 41, a steel pipe or the like similar to the connecting pipe 40 can be used.

The 1,3-butadiene-containing gas discharged from the reactor 110 flows through the connecting pipe 40 . Therefore, by-products generated by the conversion reaction may adhere to the inner surface (flow path) of the connecting pipe 40 . Adhesion of by-products to the inner surface of the connecting pipe 40 may cause clogging of the connecting pipe 40 and pressure loss. Therefore, it is preferable that the connection pipe 40 has the following configuration.

By-products produced in the conversion process include impurities (heavy substances) contained in the brown oil and impurities (light substances) contained in the 1,3-butadiene-containing gas.
Examples of brown oils include hydrocarbons having 5 or more carbon atoms, alcohols having 3 or more carbon atoms, aldehydes having 3 or more carbon atoms, ketones having 2 or more carbon atoms, ethers having 3 or more carbon atoms, esters having 2 or more carbon atoms, Examples thereof include carboxylic acids having 1 or more carbon atoms.
The upper limit of the carbon number of the brown oil is not particularly limited, but is set to 50, for example.

Examples of impurities (light substances) contained in the 1,3-butadiene-containing gas include ethylene, propylene, diethyl ether, ethyl acetate, butanol, hexanol, 1-butene, 2-butene, isobutene, pentene, pentadiene, hexene, hexadiene and the like.

Specifically, the bent portion of the connection pipe includes the bent portion Rm of the connection pipe 40, and the radius of curvature thereof is preferably 20 mm or more, more preferably 25 mm or more, and even more preferably 30 mm or more. When the radius of curvature of the bent portion Rm is equal to or greater than the above lower limit, it is possible to prevent accumulation of by-products, particularly brown oil. The upper limit of the radius of curvature of the bent portion Rm is not particularly limited, and is set to 100 mm, for example.
The radius of curvature of each bent portion Rm is given by the radius of a circle when the curve of the inner surface of each bent portion Rm is regarded as an arc. Here, m is the number of bends and is a natural number. For example, m is preferably from 1 to 20, more preferably from 1 to 10, and even more preferably from 1 to 5. In this embodiment, m is 1-3. Note that m increases as the distance from the second reactor 110 increases, as shown in FIG. For example, if there are three bends as shown in FIG. 1, the bend closest to the second reactor 110 is R1 and the furthest bend is R3.
When two straight pipes are connected by a joint or the like to form a bent portion, the curvature radius of the joint or the like is regarded as the curvature radius of the connecting pipe 40 at the bent portion.

The value (r _Rm /T _Rm ) obtained by dividing the radius of curvature (r _Rm (mm)) of the bent portion Rm by the temperature T _Rm (K) of the inner surface of the bent portion Rm is preferably 0.03 to 100 mm/K, and 0 0.05 to 80 mm/K is more preferred, and 0.07 to 60 mm/K is even more preferred. When r _Rm /T _Rm is equal to or higher than the above lower limit, the temperature T _Rm is high, and the brown oil has a high fluidity, so that the brown oil is less likely to accumulate on the inner surface of the bent portion Rm. When r _Rm /T _Rm is equal to or less than the above upper limit value, the radius of curvature (r _Rm ) is large, so brown oil is less likely to accumulate on the inner surface of the bent portion Rm.

The value (r _Rm /r' Rm ) obtained by dividing the radius of curvature (r _Rm (mm)) of the bend Rm by the radius (r' _Rm (mm)) of the pipe at the bend _Rm is 0.02 to 1.00. is preferred, 0.03 to 0.80 is more preferred, and 0.05 to 0.60 is even more preferred. When r _Rm /r′ _Rm is equal to or higher than the above lower limit, the radius (r′ _Rm (mm)) of the pipe at the bent portion Rm is small, and the dispersibility of the brown oil is increased. hard to accumulate. When r _Rm /r′ _Rm is equal to or less than the above upper limit value, the radius of curvature (r _Rm (mm)) of the bent portion Rm is large, so brown oil is less likely to accumulate on the inner surface of the bent portion Rm. The radius (r' _Rm (mm)) of the pipe at the bent portion Rm means the length obtained by dividing the inner diameter of the pipe at the bent portion Rm by 2.

The value (r _Rm /μ _Rm ) obtained by dividing the radius of curvature (r _Rm (mm)) of the bent portion Rm by the viscosity (μ _Rm (mPa·s)) of the by-product adhering to the inner surface of the bent portion Rm is 0. 04 mm/mPa·s or more is preferable, 0.05 mm/mPa·s or more is more preferable, and 0.06 mm/mPa·s or more is even more preferable. When r _Rm /μ _Rm is equal to or greater than the above lower limit value, the radius of curvature (r _Rm (mm)) of the bent portion Rm is large, so brown oil is less likely to accumulate on the inner surface of the bent portion Rm. Although the upper limit of r _Rm /μ _Rm is not particularly limited, it is, for example, 1.0 mm/mPa·s. The viscosity (μ _Rm (mPa s)) of the by-product adhering to the inner surface of the bending portion Rm was measured by collecting 10 mL of the by-product adhering to the inner surface of the bending portion Rm and using a Brookfield viscometer. The value shall be measured at 190°C.

The arithmetic average roughness (Ra ₄₀ (μm)) of the inner surface of the connection pipe 40 is preferably 1.02 μm or less, more preferably 1.00 μm or less, still more preferably 0.90 μm or less, and particularly preferably 0.80 μm or less. When the arithmetic mean roughness of the inner surface of the connecting pipe 40 is equal to or less than the above upper limit value, adhesion of by-products, particularly brown oil, can be suppressed. The lower limit of the arithmetic mean roughness of the inner surface of the connecting pipe 40 is not particularly limited, but is set to 0.01 μm, for example.
The arithmetic mean roughness of the inner surface of the connection pipe 40 is measured using a roughness curve described in JIS B0601:2013 with a cutoff value of 2.5 using Handysurf E-35B manufactured by Tokyo Seimitsu Co., Ltd. Arithmetic mean roughness.
The arithmetic average roughness of the inner surface of the connection pipe 40 can be adjusted by the material of the connection pipe 40, maintenance of the connection pipe 40, and the like.

When the temperature of the inner surface of the connecting pipe 40 is T ₄₀ (K), the product of the arithmetic mean roughness (Ra ₄₀ (μm)) of the connecting pipe 40 and T ₄₀ ( Ra ₄₀ ·T ₄₀ ) is preferably from 0.1 to 750 µm·K, more preferably from 0.5 to 550 µm·K, and even more preferably from 1.0 to 480 µm·K. When Ra ₄₀ ·T ₄₀ is equal to or higher than the above lower limit, the temperature T ₄₀ is high, and the brown oil has a high fluidity. When Ra ₄₀ ·T ₄₀ is equal to or less than the above upper limit, brown oil is less likely to accumulate on the inner surface of the connection pipe 40 because Ra ₄₀ is small.
Note that T ₄₀ (K) is the temperature of the inner surface of the connecting pipe 40 at the position having the arithmetic mean roughness.

When the pipe radius of the connecting pipe 40 is r ₄₀ (mm), the product of the arithmetic mean roughness (Ra ₄₀ (μm)) of the connecting pipe 40 and r ₄₀ (Ra ₄₀ ·r ₄₀ ) is 0.002 to 1 mm ² is preferred, 0.005-0.8 mm ² is more preferred, and 0.01-0.5 mm ² is even more preferred. If Ra ₄₀ ·r ₄₀ is equal to or greater than the above lower limit, brown oil is less likely to accumulate on the inner surface of the connecting pipe 40 because Ra ₄₀ is small. When Ra ₄₀ ·r ₄₀ is equal to or less than the above upper limit, the pipe radius r ₄₀ is wide, and brown oil is less likely to accumulate on the inner surface of the connection pipe 40 because the dispersibility of brown oil increases.
Note that r ₄₀ (mm) is the radius of the connecting pipe 40 (1/2 of the inner diameter of the pipe) at the position having the arithmetic mean roughness.

A value obtained by dividing the arithmetic mean roughness (Ra ₄₀ (μm)) of the connecting pipe 40 by μ 40 _{(Ra 40 /} μ ₄₀ ), where μ ₄₀ (mPa·s) is the viscosity of the by-product in the connecting pipe 40 is preferably 0.0001 µm/mPa·s or more, more preferably 0.0002 µm/mPa·s or more, and still more preferably 0.0005 µm/mPa·s or more. When Ra ₄₀ /μ ₄₀ is equal to or higher than the above lower limit, brown oil is less likely to accumulate on the inner surface of the connection pipe 40 because Ra ₄₀ is small. The upper limit of Ra ₄₀ /μ ₄₀ is not particularly limited, but is, for example, 0.01 μm/mPa·s.
Note that μ ₄₀ (mPa·s) is the viscosity at 190° C. of the by-product at the position having the arithmetic mean roughness in the connecting pipe 40 .

The inner surface of the connecting pipe 40 is preferably coated with an organic compound having 6 to 12 carbon atoms. Since the inner surface of the connecting pipe 40 is coated with an organic compound having 6 to 12 carbon atoms, it is possible to suppress adhesion of brown oil to the inner surface of the connecting pipe 40 .
Examples of organic compounds having 6 to 12 carbon atoms include hydrocarbons having 7 to 10 carbon atoms, alcohols, aldehydes, ketones, ethers, esters, carboxylic acids, phenols and the like. More specific examples include δ-hexanolactone, 2,6-diisopropylphenol, 1-adamantylmethylketone and the like.

As used herein, the term “coated” means that a coating layer having a thickness of 100 mm or less is formed on the inner surface of the connecting pipe 40 . The thickness of the coating layer is preferably 0.001-100 mm, more preferably 0.01-10 mm. If the thickness of the coating layer is equal to or greater than the lower limit value, adhesion of brown oil to the inner surface of the connecting pipe 40 can be suppressed. When the thickness of the coating layer is equal to or less than the above upper limit, clogging of piping and pressure loss can be suppressed. The thickness of the coating layer can be measured by observing, with a microscope or the like, a cross section obtained by cutting the bent portion of the connecting pipe 40 closest to the reactor 110 in the thickness direction of the connecting pipe 40 . In this case, the thickness of the coating layer is measured at 10 randomly selected points from the flow channel at the bend closest to the reactor 110 of the connection pipe 40, and the arithmetic mean value of the measured values is the "thickness of the coating layer. ”.
In addition, “the bent portion of the connecting pipe 40 closest to the reactor 110 ” refers to the portion of the connecting pipe 40 that has a radius of curvature of 100 mm or less and is closest to the reactor 110 . In this embodiment, the bent portion R1 is the bent portion of the connecting pipe 40 that is closest to the reactor 110 .

The temperature of the inner surface of the connecting pipe 40 at the bend closest to the reactor 110 (T _R1 (K)) is relative to the temperature of the inner surface of the reactor 110 (T ₁₁₀ (K), the temperature of the central portion of the catalyst layer). , -250°C or higher is preferred, -200°C or higher is more preferred, and -150°C or higher is even more preferred. When the temperature of the inner surface of the connecting pipe 40 at the bent portion closest to the reactor 110 is equal to or higher than the above lower limit value, adhesion of brown oil to the inner surface of the connecting pipe 40 can be suppressed. The upper limit of the temperature of the inner surface of the connecting pipe 40 at the bend closest to the reactor 110 is not particularly limited, but is set to ±0° C. with respect to the temperature of the inner surface of the reactor 110, for example.

The temperature drop of the inner surface of the connecting pipe 40 at the bend closest to the reactor 110 (hereinafter also simply referred to as “temperature drop”) is 70% relative to the temperature of the inner surface of the reactor 110 (T ₁₁₀ (K)). % or less is preferable, 60% or less is more preferable, and 50% or less is even more preferable. If the temperature drop is equal to or less than the upper limit value, adhesion of brown oil to the inner surface of the connecting pipe 40 can be suppressed. The lower limit of the temperature drop is not particularly limited, but is set to 0%, for example.
Note that the temperature drop is obtained by the following formula (3).
Temperature drop (%) = (T ₁₁₀ (K) - T _R1 (K))/T ₁₁₀ (K) x 100 (3)

The pipe radius (r′ _R1 (mm)) of the connecting pipe 40 at the bend closest to the reactor 110 is preferably 50 to 1000 mm, more preferably 80 to 800 mm, and even more preferably 100 to 500 mm. If the pipe radius (r′ _R1 (mm)) is equal to or greater than the above lower limit value, adhesion of brown oil to the inner surface of the connecting pipe 40 can be suppressed. When the pipe radius (r' _R1 (mm)) is equal to or less than the above upper limit, maintenance of the connection pipe 40 is facilitated. The radius of the pipe (r' _R1 (mm)) is the radius of the pipe at the bent portion R1 (1/2 of the inner diameter of the pipe).

The reduction rate of the pipe radius at the bend closest to the reactor 110 of the connection pipe 40 is, with respect to the pipe radius before the bend (r' _front (mm), 1/2 of the inner diameter of the pipe before the bend), 70% or less is preferable, 60% or less is more preferable, and 50% or less is even more preferable. If the reduction rate of the pipe radius is equal to or less than the upper limit value, adhesion of brown oil to the inner surface of the connection pipe 40 can be suppressed. The lower limit of the pipe radius reduction rate is not particularly limited, but is set to 0%, for example. In addition, the reduction rate of the pipe radius is obtained by the following formula (4).
Pipe radius reduction rate (%) = (r' _front (mm) - r' _rear (mm)) / r' _front (mm) x 100 (4)
In Equation (4), _after r' (mm) is the radius of the pipe after bending (1/2 of the inner diameter of the pipe after the bend).

A main component of the by-product that may adhere to the inner surface of the bent portion of the connecting pipe 40 closest to the reactor 110 is a compound having 4 or more carbon atoms produced by polymerization of acetaldehyde. Examples of these compounds include δ-hexanolactone, 2,6-diisopropylphenol, 1-adamantylmethylketone and the like. These compounds can be detected by analyzing by-products trapped in bypass 41 of manufacturing apparatus 100A by gas chromatography (GC).
The viscosity (μ _R1 (mPa·s)) of by-products that can adhere to the inner surface of the bent portion of connecting pipe 40 closest to reactor 110 varies depending on the mixing ratio of these compounds. The viscosity (μ _R1 (mPa·s)) of the by-product is preferably 100 to 800 mPa·s. The viscosity of the by-product (μ _R1 (mPa s)) is the viscosity measured at 20° C. using a coaxial double cylindrical rotational viscometer (constant inner cylinder speed method) described in JIS Z8803:2011. is.

A bypass 41 is provided in parallel with the connection pipe 40 . By closing the valve 43 and opening the valve 45 , the 1,3-butadiene-containing gas can flow through the bypass 41 . By making the arithmetic mean roughness (Ra ₄₁ ) of the inner surface of the bypass 41 larger than Ra ₄₀ and making the temperature T ₄₁ of the inner surface of the bypass 41 lower than T ₄₀ , by-products, In particular, brown oil can be easily collected. That is, the bypass 41 can be used as a by-product trap. By providing the bypass 41 with a bent portion with a small radius of curvature or installing a filter with an appropriate grid size, the function as a trap can be further enhanced.

The bypass 41 has a detachable portion sandwiched between the valves 45 . By making the bypass 41 removable, maintenance can be performed without stopping the continuous operation of the manufacturing apparatus 100 by replacing it with a new bypass or cleaning the inner surface when the by-product adheres to the inner surface. can do. When the bypass 41 is to be maintained, the valve 45 is closed and the bypass 41 is removed. In addition to the trap by the bypass pipe, install a detachable filter with an appropriate grid size on the connecting pipe and/or the bypass pipe, and maintain the manufacturing equipment by appropriately removing the adhered and accumulated by-products. can also

When the by-product adheres to the inner surface of the connection pipe 40 , the valve 43 is closed and the valve 45 is opened to allow the 1,3-butadiene-containing gas to flow through the bypass 41 . Since the portion sandwiched by the valve 43 of the connecting pipe 40 is detachable, it is possible to perform maintenance on this portion.

A bypass other than the bypass 41 may be provided in the connection pipe 40 . By providing a bypass other than the bypass 41, more by-products can be recovered.
The number of bypasses may be one, or two or more.

A method for producing 1,3-butadiene according to the first embodiment using the production apparatus 100 will be described below.
The ethanol feedstock is supplied from the raw material storage unit 102 to the vaporizer 104 through the pipe 10, and the ethanol feedstock is vaporized under the conditions of -1.0 MPaG to 1.0 MPaG and the temperature of -100°C to 200°C to contain ethanol. It is made into gas (process A1). Ethanol-containing gas is sent from the vaporizer 104 to the pipe 12 , and nitrogen gas (dilution gas) is joined from the diluent gas storage unit 106 through the pipe 24 and mixed by the mixer 16 . Then, the ethanol concentration of the ethanol-containing gas is adjusted within the range of 0.1% by volume to 100% by volume (step A2).

The ethanol-containing gas with adjusted ethanol concentration is heated by the heat exchanger 18 and supplied to two or more parallel first reactors 108 . In each first reactor 108, for example, the ethanol-containing gas is contacted with the first catalyst under conditions of a pressure of 0 to 1.0 MPaG and a temperature of 50° C. to 500° C., so that ethanol in the ethanol-containing gas is A portion is converted to acetaldehyde (step B1). An intermediate gas containing ethanol and acetaldehyde is sent from each first reactor 108 to the pipe 28 .

A part of the ethanol-containing gas obtained in the vaporizer 104 (step A1) is mixed with the intermediate gas through the pipe 36 to obtain a mixed gas (step B2). The analyzer 34 analyzes the molar ratio (ethanol/aldehyde) in the intermediate gas or mixed gas supplied to the second reactor 110 . Based on the result, the flow rate indicator adjuster 38 adjusts the flow rate of the ethanol-containing gas from the pipe 36, and adjusts the molar ratio (ethanol/aldehyde) of the mixed gas supplied to the second reactor 110 within the range of 1 to 100. (Step B2). Specifically, when the molar ratio (ethanol/aldehyde) decreases during operation of the manufacturing process, the flow rate of the ethanol-containing gas supplied from the pipe 36 is increased to increase the molar ratio (ethanol/aldehyde). can do. Conversely, when the molar ratio (ethanol/aldehyde) increases, the molar ratio (ethanol/aldehyde) can be decreased by reducing the flow rate of the ethanol-containing gas supplied from the pipe 36 .

The intermediate gas or the mixed gas is sent to the hydrogen concentration reduction device 109 . The intermediate gas or the mixed gas is separated into ethanol and acetaldehyde and a hydrogen-containing gas. In one embodiment, when the hydrogen concentration reduction device 109 is the hydrogen concentration reduction device 109 - 1 described above, the intermediate gas or the mixed gas is cooled by the heat exchanger 130 and supplied to the gas-liquid separator 132 . A gas containing hydrogen is separated from the intermediate gas or the mixed gas in the gas-liquid separator 132 . Specifically, gas-liquid separation can separate into a liquid containing ethanol and acetaldehyde and a gas containing hydrogen (step B4-1). In this case, the liquid containing ethanol and acetaldehyde is heated by the vaporizer 138, vaporized again, and supplied to the second reactor 110 through the pipe 29 as the intermediate gas or mixed gas. The hydrogen-containing gas separated by the gas-liquid separator 132 is processed outside through a pipe 134 . In another embodiment, when the hydrogen concentration reduction device 109 is the hydrogen concentration reduction device 109-2 described above, the intermediate gas or the mixed gas is supplied to a gas separator, and a gas containing ethanol and acetaldehyde and hydrogen are separated. It is separated from the containing gas (step B4-3). The hydrogen-containing gas may be discharged from a pipe (not shown) that discharges the hydrogen-containing gas. A gas containing ethanol and acetaldehyde is supplied to the second reactor 110 as the intermediate gas or mixed gas. In another embodiment, when the hydrogen concentration reduction device 109 is the above-described hydrogen concentration reduction device 109-3, the intermediate gas or the mixed gas is gas-liquid separated by a scrubber, and a liquid containing ethanol and acetaldehyde and hydrogen (step B4-4). In this case, a liquid containing ethanol and acetaldehyde is heated by a vaporizer, vaporized again, and supplied to the second reactor 110 as the intermediate gas or mixed gas. The hydrogen-containing gas may be discharged from a pipe (not shown) that discharges the hydrogen-containing gas.

The concentration of hydrogen in the intermediate gas or the mixed gas supplied to the second reactor 110 is analyzed by the analyzer 35 . Based on the result, the flow rate of nitrogen gas (diluent gas) from the pipe 37 is adjusted by the flow indicator controller 27, and the hydrogen concentration in the intermediate gas or mixed gas supplied to the second reactor 110 is 15% by volume. Control to less than (step B4-2). In other words, the diluting gas storage section 106, the pipe 37, the flow indicator controller 27, the pipe 29, and the analyzer 35 constitute the dilution apparatus of this embodiment.

An intermediate gas or mixed gas is supplied to two or more parallel second reactors 110 . In each second reactor 110, for example, the intermediate gas or the mixed gas is brought into contact with the second catalyst under conditions of a pressure of 0 to 1.0 MPaG and a temperature of 50 ° C. to 500 ° C., and the intermediate gas or Ethanol and acetaldehyde in the mixed gas are converted to 1,3-butadiene (step B3). A 1,3-butadiene-containing gas is delivered from each second reactor 110 to the connecting pipe 40 .

The 1,3-butadiene-containing gas is cooled by heat exchanger 44 and supplied to gas-liquid separator 112 . In the gas-liquid separator 112, a hydrogen-containing gas is separated from the 1,3-butadiene-containing gas by gas-liquid separation. Specifically, by gas-liquid separation, the 1,3-butadiene-containing gas is separated into hydrogen gas and nitrogen gas (diluent gas) and a 1,3-butadiene-containing liquid (step C2). The pump 48 is driven to supply the 1,3-butadiene-containing liquid from the gas-liquid separator 112 through the pipe 46 to the first distillation column 114, where the 1,3-butadiene-containing liquid is distilled. An ethylene-containing gas is extracted from the top of the first distillation column 114 to the pipe 52, an acetaldehyde-containing liquid is extracted from the bottom of the column to the pipe 60, and a 1,3-butadiene-containing effluent is extracted from the intermediate part to the pipe 56. Separate (step C3). The ethylene-containing gas drawn out to the pipe 52 is combined with the hydrogen gas and nitrogen gas (dilution gas) drawn out from the gas phase part of the gas-liquid separator 112 to the pipe 54 and treated as waste gas.

The 1,3-butadiene-containing effluent discharged through the pipe 56 is supplied to the third reactor 116, where the 1,3-butadiene-containing effluent is dehydrogenated in the presence of the third catalyst to produce 1,3- The butenes (1-butene, 2-butene, isobutene) in the butadiene-containing effluent are converted to 1,3-butadiene (step C1). Purified 1,3-butadiene is sent from the third reactor 116 to the recovery unit 120 through the pipe 58 and recovered.

The acetaldehyde-containing liquid extracted from the bottom of the first distillation column 114 to the pipe 60 is supplied to the second distillation column 118 and distilled. A residual liquid containing water is withdrawn from the bottom of the second distillation column 118 to the pipe 64, and an acetaldehyde-containing gas is withdrawn from the top of the column (step C4).

In addition, in the manufacturing apparatus 100 having the above configuration, the first catalyst is prevented from being mixed into the second reactor 110 in the route of the pipe 28 and the pipe 29 connecting the first reactor 108 and the second reactor 110. It is preferable to install a dust collector (not shown) to prevent this.
By installing such a dust collector, the conversion reaction from ethanol to acetaldehyde in the second reactor 110 can be suppressed, and the conversion to 1,3-butadiene by the second catalyst that requires ethanol is stabilized. can be effectively maintained.
Examples of the dust collector as described above include, but are not particularly limited to, a cyclone, a bag filter, or a packed bed filter.

Furthermore, in the production apparatus 100, in order to prevent the first catalyst or the second catalyst from flowing out to the rear stage side of the first reactor 108 or the second reactor 110, the rear stage side of each reactor, specifically, Preferably, a catalyst holding unit (not shown) is installed in the pipe 28, the pipe 29 and the connecting pipe 40.
By installing such a catalyst holding unit, the first catalyst and the second catalyst flowing out from the first reactor 108 or the second reactor 110 are prevented from accumulating in pipes other than these reactors. can. As a result, the conversion reaction of ethanol or ethanol and acetaldehyde to 1,3-butadiene occurs at a location other than each reactor, resulting in the production of carbon-containing substances and a decrease in the yield of 1,3-butadiene. can be suppressed.
Examples of the catalyst holding unit as described above include, but are not limited to, grid supports, perforated plates, and alumina balls.

As described above, in this embodiment, processes A to C are performed. In particular, by performing step B4-1 or step 4-2, the hydrogen concentration in the intermediate gas or mixed gas supplied to the second reactor 110 is less than 15% by volume, the activity of the second catalyst is reduced, and side reactions occur. can be suppressed, and the yield of 1,3-butadiene is improved.

The method for producing 1,3-butadiene of the present invention is not limited to the above-described embodiments, and the configurations described in each step can be appropriately combined. It is possible to appropriately replace the constituent elements in the above-described embodiments with well-known constituent elements without departing from the scope of the present invention.

EXAMPLES The present invention will be described in more detail below with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples.

1. Production of Catalyst First, 1.0 g of hafnium chloride (HfCl ₄ : manufactured by Kojundo Chemical Laboratory Co., Ltd.) was dissolved in 100 mL of water to prepare a solution.
Next, this solution was added to 1.0 g of a porous carrier (silica porous particles manufactured by Fuji Silysia Chemical Co., Ltd., average particle size: 1.77 mm, average pore diameter: 10 nm, total pore volume: 1.01 mL /g, specific surface area: 283 m ² /g).
Next, the solution in which the porous carrier was immersed was stirred under atmospheric pressure with an ultrasonic cleaner for 1 hour, and the solution was separated by filtration.
The recovered porous material was dried at 110° C. for 4 hours and then calcined at 400° C. for 4.5 hours to produce a catalyst.

2. Evaluation of catalyst (production of 1,3-butadiene)
Ethanol and acetaldehyde were converted to 1,3-butadiene (hereinafter also referred to as "BD") using the catalysts produced in each example and each comparative example, and the yield of 1,3-butadiene was determined. rice field.
Specifically, 1.0 g of the catalyst was first packed into a 1/2 inch (1.27 cm) diameter, 15.7 inch (40 cm) long stainless steel cylindrical reactor to form a reaction bed. .
Next, the reaction temperature (temperature of the reaction bed) was set to 325° C., and the reaction pressure (pressure of the reaction bed) was set to 0.1 MPa.
In this state, the raw material was supplied to the reactor at a gas hourly space velocity (GHSV) of 1200 h ⁻¹ against the catalyst to obtain a product gas containing 1,3-butadiene.
One hour after starting the supply of the raw material, the produced gas was recovered.
Then, each of the collected generated gases is analyzed by gas chromatography, and the selectivity of BD, the conversion rate of ethanol and acetaldehyde, and the yield of BD ([conversion rate of ethanol and acetaldehyde] × [selectivity of BD]) are obtained. rice field.
The "selectivity of BD" is the percentage of the number of moles of ethanol and acetaldehyde converted to BD among the number of moles of ethanol and acetaldehyde contained in the raw materials consumed in the reaction using the catalyst.
Further, the "conversion rate of ethanol and acetaldehyde" is the percentage of the number of moles of ethanol and acetaldehyde consumed in the number of moles of ethanol and acetaldehyde contained in the raw material.

[Comparative Example 1]
A mixed gas of 35% by volume ethanol, 35% by volume acetaldehyde, and 30% by volume hydrogen was used as a raw material. In addition, volume % is gaseous conversion, and is the same as below.

[Comparative Example 2]
A mixed gas of 35% by volume ethanol, 35% by volume acetaldehyde, 15% by volume nitrogen, and 15% by volume hydrogen was used as a raw material.

[Example 1]
A mixed gas of 35% by volume ethanol, 35% by volume acetaldehyde, 20% by volume nitrogen, and 10% by volume hydrogen was used as a raw material.

[Example 2]
A mixed gas of 35% by volume ethanol, 35% by volume acetaldehyde, 25% by volume nitrogen, and 5% by volume hydrogen was used as a raw material.

[Example 3]
A mixed gas of 35% by volume ethanol, 35% by volume acetaldehyde, and 30% by volume nitrogen was used as a raw material.

As shown in Table 1, in Comparative Examples 1 and 2 in which the hydrogen concentration in the raw material in the second conversion step is 15% by volume or more, the BD yield is higher than in Examples 1 to 3 in which the hydrogen concentration is less than 15% by volume. It was found that the rate decreased. That is, as described above, by controlling the hydrogen concentration in the intermediate gas or the mixed gas supplied to the second conversion step to less than 15% by volume, 1,3-butadiene is continuously produced at a high yield. It is possible.

DESCRIPTION OF SYMBOLS 1... Gas preparation means, 2... Conversion means, 3... Purification means, 10... Piping, 11... Flow indicator, 12... Piping, 14... Pressure indicator controller, 16... Mixer, 18... Heat exchanger, 20... Temperature Indicator controller 22 Valve 24 Piping 26 Flow indicator controller 27 Flow indicator controller 28 Piping 29 Piping 30 Valve 32 Valve 34 Analyzer 33 Mixer , 35... Analyzer, 36... Piping, 37... Piping, 38... Flow rate indicator regulator, 40... Connection pipe, 41... Bypass, 42... Valve 43... Valve, 44... Heat exchanger, 45... Valve, 46... Piping , 48... Pump, 50... Level indicating controller, 52... Piping, 54... Piping, 56... Piping, 58... Piping, 60... Piping, 64... Piping, 100... 1,3-butadiene manufacturing apparatus, 102... Raw material storage Part 104... Vaporizer 106... Diluent gas storage part 108... First reactor 109 (109-1)... Hydrogen concentration reducing device 110... Second reactor 112... Gas-liquid separator 114... First distillation column 116 Third reactor 118 Second distillation column 120 Recovery unit 130 Heat exchanger 132 Gas-liquid separator 134 Piping 136 Piping 138 Vaporizer

Claims (12)

A method for producing 1,3-butadiene, which continuously produces 1,3-butadiene from an ethanol-containing gas,
a first conversion step of contacting the ethanol-containing gas with a first catalyst to convert part of the ethanol in the ethanol-containing gas into acetaldehyde to obtain an intermediate gas containing ethanol and acetaldehyde;
contacting the intermediate gas or a mixed gas obtained by mixing the intermediate gas and a gas containing ethanol with a second catalyst to remove ethanol and acetaldehyde from the intermediate gas or the mixed gas; - a second conversion step of converting to butadiene to obtain a 1,3-butadiene-containing gas;
A method for producing 1,3-butadiene, wherein the hydrogen concentration in the intermediate gas or the mixed gas is controlled to less than 15% by volume. 2. Production of 1,3-butadiene according to claim 1, comprising a hydrogen concentration reducing step of reducing hydrogen concentration in said intermediate gas or said mixed gas between said first conversion step and said second conversion step. Method. 3. 1 and 3 according to claim 2, wherein the hydrogen concentration reducing step includes a step of gas-liquid separation of the intermediate gas or the mixed gas to reduce the hydrogen concentration in the intermediate gas or the mixed gas. - A process for the production of butadiene. 4. 1 and 3 according to claim 2 or 3, wherein the hydrogen concentration reducing step includes a step of diluting the intermediate gas or the mixed gas to reduce the hydrogen concentration in the intermediate gas or the mixed gas. - A process for the production of butadiene. The production of 1,3-butadiene according to any one of claims 1 to 4, wherein the ethanol conversion in the first conversion step is 25 to 80% and the aldehyde selectivity is 80 to 100%. Method. The method for producing 1,3-butadiene according to any one of claims 1 to 5, wherein the conversion rate of ethanol and acetaldehyde in the second conversion step is over 50%. A 1,3-butadiene production apparatus for continuously producing 1,3-butadiene from an ethanol-containing gas,
provided with conversion means,
a first reactor in which the conversion means contacts the ethanol-containing gas with a first catalyst to convert a part of the ethanol in the ethanol-containing gas into acetaldehyde to obtain an intermediate gas containing ethanol and acetaldehyde; contacting the intermediate gas or a mixed gas obtained by mixing the intermediate gas and a gas containing ethanol with a second catalyst to remove ethanol and acetaldehyde from the intermediate gas or the mixed gas; - a second reactor to convert to butadiene to form a 1,3-butadiene-containing gas, and hydrogen between the first reactor and the second reactor to reduce the hydrogen concentration in the intermediate gas or the mixed gas. and a concentration reducing device. 8. The apparatus for producing 1,3-butadiene according to claim 7, further comprising a dilution device for diluting the intermediate gas or the mixed gas with an inert gas between the first reactor and the second reactor. . and a connecting pipe connecting the conversion means and the purification means, wherein the purification means is means for purifying the 1,3-butadiene-containing gas obtained by the conversion means, and the connection 9. The apparatus for producing 1,3-butadiene according to claim 7 or 8, wherein the pipe has at least one bend, and the bend has a radius of curvature of 20 mm or more. 10. The apparatus for producing 1,3-butadiene according to claim 9, wherein the inner surface of the connecting pipe has an arithmetic average roughness of 1.02 μm or less. 11. The apparatus for producing 1,3-butadiene according to claim 9 or 10, wherein the inner surface of said connecting pipe is coated with an organic compound having 6 to 12 carbon atoms. 12. The apparatus for producing 1,3-butadiene according to any one of claims 9 to 11, wherein said connecting pipe has at least one bypass, and said bypass is removable.

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