Method for producing 1, 3-butadiene

Abstract

To provide a method for producing 1, 3-butadiene, by which the 1, 3-butadiene can continuously be produced in a high yield, and to provide an apparatus for producing the butadiene.SOLUTION: A first conversion step of bringing an ethanol-containing gas into contact with a first catalyst to convert a part of ethanol in the ethanol-containing gas into acetaldehyde to obtain an intermediate gas, and a second conversion step of bringing the intermediate gas or a mixed gas obtained by mixing the intermediate gas with a gas containing ethanol into contact with a second catalyst to convert the intermediate gas or the mixed gas into 1,3-butadiene to obtain a 1,3-butadiene-containing gas, wherein a hydrogen concentration in the intermediate gas or the mixed gas is controlled to be less than 15% by volume. To provide a method for producing 1, 3-butadiene.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for producing 1,3-butadiene. [Background technology]

[0002] Butadienes such as 1,3-butadiene are used as raw materials for styrene-butadiene rubber (SBR), etc. Known methods for producing 1,3-butadiene include, for example, a first step in which ethanol is brought into contact with a first catalyst to convert the ethanol into acetaldehyde, and a second step in which the ethanol and acetaldehyde are further brought into contact with a second catalyst to convert them into 1,3-butadiene (Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Special Publication No. 2017-532318 Summary of the Invention [Problem to be solved by the invention]

[0004] In the reaction of the first step, hydrogen is produced in an amount equimolar to acetaldehyde. The inventors of the present application have studied the method for producing 1,3-butadiene comprising the first and second steps described in Patent Document 1, and have found that the hydrogen produced in the first step reduces the yield of 1,3-butadiene in the second step.

[0005] Furthermore, heated hydrogen is known to corrode metal equipment and piping used in the butadiene production process, especially at bent sections of the piping where the hydrogen comes into contact with the flowing gas more frequently, which makes the piping more susceptible to deterioration.

[0006] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method for producing 1,3-butadiene and an apparatus for producing butadiene, which are capable of continuously producing 1,3-butadiene at a high yield. [Means for solving the problem]

[0007] The present invention has the following aspects. [1] A method for producing 1,3-butadiene continuously from an ethanol-containing gas, comprising: a first conversion step in which the ethanol-containing gas is brought into contact with a first catalyst to convert a portion of the ethanol in the ethanol-containing gas into acetaldehyde, thereby obtaining an intermediate gas containing ethanol and acetaldehyde; and a second conversion step in which the intermediate gas, or a mixed gas obtained by mixing the intermediate gas with a gas containing ethanol, is brought into contact with a second catalyst to convert the ethanol and acetaldehyde in the intermediate gas or the mixed gas into 1,3-butadiene, thereby obtaining a 1,3-butadiene-containing gas, wherein the hydrogen concentration in the intermediate gas or the mixed gas is controlled to less than 15% by volume. [2] The method for producing 1,3-butadiene according to [1], further comprising 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. [3] The method for producing 1,3-butadiene according to [2], wherein the hydrogen concentration reduction step includes a step of subjecting the intermediate gas or the mixed gas to gas-liquid separation to reduce the hydrogen concentration in the intermediate gas or the mixed gas. [4] The method for producing 1,3-butadiene according to [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. [5] The method for producing 1,3-butadiene according to any one of [1] to [4], wherein the conversion rate of ethanol in the first conversion step is 25 to 80%, and the selectivity for aldehyde is 80 to 100%. [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 more than 50%. [7] An apparatus for producing 1,3-butadiene continuously from an ethanol-containing gas, the apparatus comprising: a conversion means; a first reactor for bringing the ethanol-containing gas into contact with a first catalyst to convert a portion of the ethanol in the ethanol-containing gas into acetaldehyde and produce an intermediate gas containing ethanol and acetaldehyde; a second reactor for bringing the intermediate gas or a mixed gas obtained by mixing the intermediate gas with a gas containing ethanol into contact with a second catalyst to convert the ethanol and acetaldehyde in the intermediate gas or the mixed gas into 1,3-butadiene and produce a 1,3-butadiene-containing gas; and a hydrogen concentration reduction device between the first reactor and the second reactor that reduces the hydrogen concentration in the intermediate gas or the mixed gas. [8] The apparatus for producing 1,3-butadiene according to [7], further comprising a dilution device between the first reactor and the second reactor that dilutes the intermediate gas or the mixed gas with an inert gas. [9] The apparatus for producing 1,3-butadiene according to [7] or [8], further comprising a purifying means and a connecting pipe connecting the converting means and the purifying means, wherein the purifying means is a means for purifying the 1,3-butadiene-containing gas obtained by the converting means, and the connecting pipe has at least one bent portion, and the bent portion has a curvature radius of 20 mm or more.

[10] The apparatus for producing 1,3-butadiene according to [9], wherein the arithmetic mean roughness of the inner surface of the connecting pipe is 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. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a method for producing 1,3-butadiene and an apparatus for producing butadiene, which are capable of continuously producing 1,3-butadiene at a high yield. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a schematic diagram of a butadiene production apparatus according to one embodiment of the present invention. [Figure 2] 1 is a schematic diagram of a hydrogen concentration reducing device according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0010] The following describes in detail the embodiments of the present invention. However, the following description is an example of an embodiment of the present invention, and the present invention is not limited to these contents and can be modified and implemented within the scope of its gist.

[0011] [Method of producing 1,3-butadiene] The method for producing 1,3-butadiene of this embodiment is a method for continuously producing 1,3-butadiene from an ethanol-containing gas, and includes the following steps B1 and B3: In the method for producing 1,3-butadiene of this 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 in which an ethanol-containing gas is brought into contact with a first catalyst to convert a portion of the ethanol in the ethanol-containing gas into acetaldehyde, thereby obtaining an intermediate gas containing ethanol and acetaldehyde. Step B3: A second conversion step in which the intermediate gas or a mixed gas obtained by mixing the intermediate gas with a gas containing ethanol is contacted with a second catalyst to convert the ethanol and acetaldehyde in the intermediate gas or the mixed gas into 1,3-butadiene, thereby obtaining a 1,3-butadiene-containing gas.

[0012] When step B3 is a second conversion step in which the mixed gas is contacted with a second catalyst to convert ethanol and acetaldehyde in the mixed gas into 1,3-butadiene and obtain a 1,3-butadiene-containing gas, step B2 is included between step B1 and step B3. Step B2: A mixed gas preparation step of mixing the intermediate gas obtained in the first conversion step with a gas containing ethanol to obtain a mixed gas.

[0013] The ethanol-containing gas used in step B1 is not particularly limited, but for example, an ethanol-containing gas prepared by the following step A may be used. Step A: A gas preparation step for preparing an ethanol-containing gas from an ethanol feedstock.

[0014] The 1,3-butadiene-containing gas produced in step B3 may be purified, for example, by the following step C to obtain purified 1,3-butadiene. Step C: A purification step of purifying the 1,3-butadiene-containing gas to obtain purified 1,3-butadiene.

[0015] (Process A) Step A includes step A1 of vaporizing an ethanol feedstock under conditions of a pressure of -1.0 to 3.0 MPaG and a temperature of -100 to 400°C to produce an ethanol-containing gas. In this specification, a numerical range expressed by "to" indicates a numerical range that includes the numbers before and after "to" as the lower and upper limits.

[0016] 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 proportion of ethanol in the ethanol feedstock is preferably 80 mass% or more, more preferably 90 mass% or more, and even more preferably 93 mass% or more, based on the total mass of the ethanol feedstock. Theoretically, the upper limit of the proportion of ethanol is 100 mass%.

[0017] The ethanol feedstock is not particularly limited and may be, for example, ethanol derived from fossil fuels such as shale gas and petroleum, or bioethanol derived from biomass such as plants, animals, garbage, etc. Among these, bioethanol is preferred because it contains fewer impurities such as nitrogen compounds and sulfur compounds and is less susceptible to catalyst degradation.

[0018] 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, and more preferably -0.3 to 1.0 MPaG. If the pressure during vaporization is equal to or higher than the lower limit of the range, the volume of the vaporized material will not be excessive, and the size of the machinery and equipment can be reduced. If the pressure during vaporization is equal to or lower than the upper limit of the range, the vaporization will be efficient.

[0019] The temperature during vaporization of the ethanol feedstock in step A1 may be set within the range of -100 to 400°C, preferably 0 to 200°C, and more preferably 25 to 100°C. When the temperature during vaporization is equal to or higher than the lower limit of the range, the ethanol is vaporized efficiently. When the temperature during vaporization is equal to or lower than the upper limit of the range, excessive heating is not required.

[0020] Step A may further include step A2, as necessary, of mixing one or more gases with the ethanol-containing gas obtained in step A1 to adjust the ethanol concentration in the ethanol-containing gas to within the range of 0.1 to 100% by volume.

[0021] The ethanol concentration of the ethanol-containing gas may be adjusted within a range of 0.1 to 100% by volume, preferably 10 to 100% by volume, and more preferably 20 to 100% by volume. If the ethanol concentration is equal to or higher than the lower limit of the range, the yield of 1,3-butadiene is improved. In 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.

[0022] The gas (dilution gas) to be mixed with the ethanol-containing gas can be an inert gas that does not adversely affect the conversion reaction from ethanol to 1,3-butadiene, and examples thereof include rare gases such as nitrogen gas and argon gas, and carbon dioxide. Of these, nitrogen gas and argon gas are preferred in terms of cost and availability. The gas to be mixed with the ethanol-containing gas can be used alone or in combination of two or more.

[0023] (Process B1) In step B1, for example, the ethanol-containing gas obtained in step A is contacted with a first catalyst packed in a first reactor described below to convert a portion of the ethanol in the ethanol-containing gas into acetaldehyde, thereby obtaining an intermediate gas containing ethanol and acetaldehyde. The reaction in step B1 is represented by the following formula (1): CH3CH2OH → CH3CHO + H2 (1)

[0024] The first reactor may be any type that can bring the ethanol-containing gas into contact with the first catalyst at a predetermined pressure and temperature. For example, a reactor in which a heat transfer medium is circulated in the side wall is filled with the first catalyst to form a reaction bed, and the supplied ethanol-containing gas is brought into contact with the first catalyst in the reaction bed. The reaction bed is not particularly limited, and examples thereof include a fixed bed, a moving bed, and a fluidized bed.

[0025] In step B1, two or more reactors arranged in parallel may be used. The number of reactors arranged in parallel in step B1 can be set appropriately, and can be, for example, 2 to 5.

[0026] The first catalyst may be any catalyst that 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 these, a mixture of copper oxide and silicon oxide is preferred in terms of the conversion rate to acetaldehyde. One type of first catalyst may be used alone, or two or more types may be used in combination.

[0027] The pressure of the total gas 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, and more preferably 0 to 0.3 MPaG. When the pressure in step B1 is equal to or higher than the lower limit of the above range, the conversion rate of ethanol is improved. When the pressure in step B1 is equal to or lower than the upper limit of the above range, liquefaction during the reaction can be suppressed.

[0028] 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, and 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 rate of ethanol is improved. When the temperature in step B1 is equal to or lower than the upper limit of the above range, excessive energy consumption can be suppressed.

[0029] In the present invention, the gas hourly space velocity (GHSV) is the gas volumetric flow rate converted into standard condition divided by the volume of the catalyst. The gas hourly space velocity of the ethanol-containing gas relative to the first catalyst is 1000 to 20000 h , converted into standard condition. -1 is preferable, and 2000 to 15,000 h -1 is more preferable, and 3000 to 10,000 h -1 When the GHSV is equal to or greater than the lower limit, the treating capacity of the ethanol-containing gas is increased, and when the GHSV is equal to or less than the upper limit, the conversion rate of ethanol is improved.

[0030] The GHSV of ethanol in the ethanol-containing gas for the first catalyst is 500 to 20,000 h (standard condition equivalent). -1 is preferable, and 1000 to 15000h -1 is more preferable, and 1500 to 10,000 h -1 When the GHSV is equal to or greater than the lower limit, the treating capacity of the ethanol-containing gas is increased, and when the GHSV is equal to or less than the upper limit, the conversion rate of ethanol is improved.

[0031] The weight hourly space velocity (WHSV) of ethanol in the ethanol-containing gas relative to the metal species of the first catalyst is 20,000 to 500,000 h -1 is preferable, and 50,000 to 450,000 h -1 is more preferable, and 100,000 to 400,000 h -1 When the WHSV is equal to or greater than the lower limit, the treating capacity of the ethanol-containing gas is increased, and when the WHSV is equal to or less than the upper limit, the conversion rate of ethanol is improved. The WHSV can be calculated as follows. The content of metal species contained in the first catalyst is measured using an inductively coupled plasma optical emission spectrometer or the like, and calculated in terms of oxide. For example, the above-mentioned chromium oxide is converted to Cr2O3, copper oxide to CuO, zinc oxide to ZnO, and silicon oxide to SiO2. The WHSV can be calculated by dividing the flow rate of ethanol in the ethanol-containing gas (unit: kg / h, for example) by the mass of the metal species contained in the first catalyst in terms of oxide (unit: kg, for example).

[0032] The conversion rate of ethanol in step B1 is preferably from 25 to 80%, more preferably from 30 to 60%, and even more preferably from 40 to 50%. The "ethanol conversion rate" in step B1 refers to the ratio (percentage) of the number of moles of ethanol consumed per unit time in the reactor to the number of moles of ethanol per unit time in the ethanol-containing gas supplied to the reactor in step B1. The number of moles of ethanol consumed per unit time in the reactor in step B1 is calculated by subtracting the number of moles of ethanol per unit time in the intermediate gas discharged from the reactor in step B1 from the number of moles of ethanol per unit time in the ethanol-containing gas supplied to the reactor in step B1.

[0033] The selectivity of acetaldehyde in the conversion reaction of step B1 is preferably 80 to 100%, more preferably 90 to 100%. The "selectivity of acetaldehyde" in step B1 refers to the ratio (percentage) of the number of moles of ethanol converted to acetaldehyde per unit time to the number of moles of ethanol consumed per unit time in the reactor of step B1. Examples of by-products that may be contained in the intermediate gas obtained in step B1 include crotonaldehyde, butyraldehyde, ethyl acetate, and acetic acid.

[0034] The yield of acetaldehyde in the conversion reaction in step B1 is preferably 25 to 80%, more preferably 30 to 70%. Note that the "yield of acetaldehyde" in step B1 means "ethanol conversion rate" x "acetaldehyde selectivity." If the yield of acetaldehyde is equal to or less than the upper limit, the amount of hydrogen produced decreases, and the hydrogen concentration in the intermediate gas or mixed gas described below decreases, resulting in an improvement in the yield of 1,3-butadiene.

[0035] (Process B2) In step B2, the intermediate gas obtained in step B1 is mixed with a gas containing ethanol to obtain a mixed gas. Step B2 is performed between steps B1 and B3.

[0036] The molar ratio of ethanol to acetaldehyde in the mixed gas (ethanol / acetaldehyde) is preferably from 1 to 100, more preferably from 1 to 50, even more preferably from 1 to 20, even more preferably from 1 to 10, and particularly preferably from 1 to 5. When the molar ratio is within the above range, the yield of 1,3-butadiene is improved.

[0037] In step B2, based on the results of monitoring the molar ratio (ethanol / acetaldehyde) in the intermediate gas obtained in the first conversion step using an analyzer, an ethanol-containing gas is mixed into the intermediate gas to increase the ethanol deficiency and achieve an optimal reaction ratio. Examples of the ethanol-containing gas include 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 easy to control the molar ratio (ethanol / acetaldehyde) within the above range. The analyzer is installed between the location where step B2 is performed and the inlet of the second reactor in step B3 described below, and analyzes the molar ratio (ethanol / aldehyde) of the gas supplied to the second reactor over time. This makes it possible to constantly observe changes in the flow rate of each gas, such as changes in the flow rate of each gas throughout the butadiene production process and changes in the flow rate of each gas due to deterioration of the catalyst and / or equipment over time. Examples of the analyzer include a process mass analyzer and a gas analyzer.

[0038] (Process B3) In step B3, the intermediate gas obtained in step B1 or the mixed gas obtained in step B2 is brought into contact with a second catalyst packed in a second reactor described below to convert ethanol and acetaldehyde in the intermediate gas or the mixed gas into 1,3-butadiene, thereby obtaining a 1,3-butadiene-containing gas. The reaction in step B3 is represented by the following formula (2): CH3CH2OH+CH3CHO→CH2=CH-CH=CH2+2H2O ···(2)

[0039] The second reactor in step B3 may be exemplified by the same embodiments as those exemplified for the first reactor. In step B3, two or more parallel reactors may be used, as in step B1. The number of reactors installed in parallel in step B3 can be appropriately set and may be, for example, 2 to 5.

[0040] The second catalyst may be any catalyst that promotes the conversion reaction from ethanol and acetaldehyde to 1,3-butadiene, and examples thereof include tantalum, zirconium, niobium, hafnium, magnesium, zinc, and silicon. Among these, hafnium is preferred from the viewpoint of the yield of 1,3-butadiene. The second catalyst may be used alone or in combination of two or more. Examples of the second catalyst include a metal, an oxide, and a chloride, and examples of the second catalyst include a catalyst supported on a carrier and a catalyst used as a mixture of two or more types.

[0041] The pressure of the total gas 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, and more preferably 0 to 0.3 MPaG. When the pressure in step B3 is equal to or higher than the lower limit of the above range, the yield of 1,3-butadiene is improved. When the pressure in step B3 is equal to or lower than the upper limit of the above range, a decrease in the yield of 1,3-butadiene due to excessive reaction can be suppressed.

[0042] 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, and more preferably 320 to 370°C. When the temperature in step B3 is equal to or higher than the lower limit of the above range, the yield of 1,3-butadiene is improved. When the temperature in step B3 is equal to or lower than the upper limit of the above range, a decrease in the yield of 1,3-butadiene due to excessive reaction can be suppressed.

[0043] The GHSV of the intermediate gas or the mixed gas relative to the second catalyst is 100 to 5000 h on a standard condition basis. -1 is preferable, and 200 to 4000 h -1 is more preferable, 400 to 3000h -1 When the GHSV is equal to or greater than the lower limit, the processing capacity of the intermediate gas or the mixed gas is increased. When the GHSV is equal to or less than the upper limit, the conversion of ethanol and acetaldehyde is improved.

[0044] The GHSV of the total of ethanol and acetaldehyde in the intermediate gas or the mixed gas relative to the second catalyst is 100 to 3000 h on a standard condition basis. -1 is preferable, and 200 to 2500 h -1 is more preferable, 400 to 2000 hours -1 When the GHSV is equal to or greater than the lower limit, the processing capacity of the intermediate gas or the mixed gas is increased. When the GHSV is equal to or less than the upper limit, the conversion of ethanol and acetaldehyde is improved.

[0045] The conversion of ethanol and acetaldehyde in step B3 is preferably greater than 50%, more preferably greater than 60%, and even more preferably greater than 70%. The "ethanol and acetaldehyde conversion rate" in step B3 refers to the molar ratio of the number of moles of ethanol and acetaldehyde consumed per unit time in the reactor to the number of moles of ethanol and acetaldehyde in the intermediate gas or the mixed gas supplied to the reactor in step B3. The number of moles of ethanol and acetaldehyde consumed per unit time in the reactor in step B3 is calculated by subtracting the number of moles of ethanol and acetaldehyde in the 1,3-butadiene-containing gas discharged from the reactor in step B3 per unit time from the number of moles of ethanol and acetaldehyde in the intermediate gas or the mixed gas supplied to the reactor in step B3 per unit time.

[0046] The selectivity of 1,3-butadiene in the conversion reaction of step B3 is preferably more than 60%, more preferably more than 70%, and even more preferably more than 80%. Note that the "selectivity of 1,3-butadiene" in step B3 means the ratio (percentage) of the number of moles of ethanol and acetaldehyde converted into 1,3-butadiene per unit time to the number of moles of ethanol and acetaldehyde consumed per unit time in the reactor of step B3.

[0047] The yield of 1,3-butadiene in the conversion reaction in step B3 is preferably 40 to 90%, more preferably 50 to 90%, and even more preferably 60 to 90%. Note that the "yield of 1,3-butadiene" in step B3 means "the conversion rate of ethanol and acetaldehyde" x "the selectivity of 1,3-butadiene."

[0048] In step B3, it is preferable that 65 to 100% of the acetaldehyde is converted into 1,3-butadiene. Examples of by-products that may 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, hexene, and hexadiene.

[0049] Under the above-described reaction conditions, the reaction results, such as the conversion rates of ethanol and acetaldehyde, indicate that the activity of the second catalyst is very high. When such a highly active second catalyst is used, if the second catalyst contains a metal oxide, the reactivity of the metal oxide toward not only ethanol and acetaldehyde but also hydrogen increases. The inventors of the present application have found that when a highly active second catalyst containing a metal oxide is used, the reactivity of the metal oxide toward hydrogen becomes too high, resulting in the reduction of the metal oxide to a less active metal, thereby reducing the activity of the second catalyst. Furthermore, they have found that hydrogen activated by the metal oxide adds to the double bond of 1,3-butadiene produced in step B3, resulting in increased production of by-products such as butene. Specifically, the inventors of the present application have newly discovered that the yield of butadiene decreases when a highly active second catalyst containing a metal oxide is used and the hydrogen concentration in the intermediate gas or the mixed gas is high.

[0050] In the method for producing 1,3-butadiene of this 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, and 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.

[0051] The hydrogen concentration can be controlled, for example, by adjusting the yield of aldehyde in step B1 to the upper limit or less. Alternatively, the hydrogen concentration can be controlled by adjusting the dilution ratio in step A2. In this embodiment, it is preferable to provide a hydrogen concentration reduction step between step B1 and step B3 to control the hydrogen concentration in the intermediate gas or the mixed gas. The hydrogen concentration reduction step is not particularly limited, but examples thereof include 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 it into gas and liquid, thereby reducing 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 separating the intermediate gas or the mixed gas using a gas separator to reduce the hydrogen concentration in the intermediate gas or the mixed gas. Step B4-4: A hydrogen concentration reduction step of subjecting the intermediate gas or the mixed gas to gas-liquid separation using a scrubber to reduce the hydrogen concentration in the intermediate gas or the mixed gas.

[0052] (Process B4-1) In step B4-1, a portion of the intermediate gas obtained in step B1 or the mixed gas obtained in step B2 is condensed to separate it into gas and liquid, thereby reducing the hydrogen concentration in the intermediate gas or the mixed gas.

[0053] Gas-liquid separation can separate the mixture into a liquid containing ethanol and acetaldehyde and a gas containing hydrogen. In this case, the liquid containing ethanol and acetaldehyde is heated and re-vaporized and supplied to the second reactor as an intermediate gas or a mixed gas. The separated gas containing hydrogen may be used as is for another purpose, or trace amounts of ethanol, acetaldehyde, and butadiene may be recovered by distillation or the like. The gas-liquid separation conditions for separating hydrogen-containing gas from the intermediate gas or mixed gas are preferably a pressure of 0 to 1.0 MPaG and a temperature of 0 to 100°C.

[0054] (Process 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.

[0055] In step B4-2, the intermediate gas obtained in step B1 or the mixed gas obtained in step B2 is diluted with a diluent gas so that the hydrogen concentration is less than 15% by volume, based on the results of monitoring the hydrogen concentration in the intermediate gas obtained in step B1 or the mixed gas obtained in step B2 using a hydrogen analyzer. Examples of the diluent gas include the diluent gases exemplified in step A2.

[0056] (Process B4-3) In step B4-3, the intermediate gas obtained in step B1 or the mixed gas obtained in step B2 is separated into gases using a gas separator to reduce the hydrogen concentration in the intermediate gas or the mixed gas.

[0057] The gas separator can be constructed using one or more of the following: a low-temperature separation (cryogenic) separator, a pressure swing adsorption (PSA) separator, a membrane separation separator, a temperature swing adsorption (TSA) separator, a separator using a porous coordination polymer (PCP) that combines metal ions (e.g., copper ions) with organic ligands (e.g., 5-azidoisophthalic acid), and a separator that uses amine absorption.

[0058] (Process B4-4) In step B4-4, the intermediate gas obtained in step B1 or the mixed gas obtained in step B2 is subjected to gas-liquid separation using a scrubber to reduce the hydrogen concentration in the intermediate gas or the mixed gas.

[0059] In the separation using a scrubber, the intermediate gas obtained in step B1 or the mixed gas obtained in step B2 can be separated into a liquid containing ethanol and acetaldehyde and a gas containing hydrogen by scrubbing the intermediate gas obtained in step B1 or the mixed gas obtained in step B2 with a solvent such as ethanol or acetaldehyde. In this case, the liquid containing ethanol, acetaldehyde, and the solvent is heated and vaporized again, and then supplied to the second reactor as an intermediate gas or a mixed gas.

[0060] 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 analyzes the hydrogen concentration in the intermediate gas or the mixed gas supplied to the second reactor over time. When it is desired to analyze the hydrogen concentration in the mixed gas, the hydrogen analyzer is installed between the location where step B2 is performed and the inlet of the second reactor in step B3. Examples of hydrogen analyzers include an in-line hydrogen analyzer, a thermal conductivity hydrogen analyzer, a process mass spectrometer, and a gas analyzer. When both step B4-1 and step B4-2 are performed, step B4-2 is preferably performed after step B4-1. When both step B4-2 and step B4-4 are performed, step B4-2 is preferably performed after step B4-4. When all of steps B4-1 to B4-4 are performed, they are preferably performed in the following order: step B4-4, step B4-1, step B4-3, step B4-2. That is, step B4-2 is preferably performed last.

[0061] (Process C) Step C includes at least one step selected from the group consisting of the following steps C1 to C4. Step C1: Butenes (1-butene, 2-butene, isobutene) in the 1,3-butadiene-containing gas are converted into 1,3-butadiene by a dehydrogenation reaction. Step C2: A gas containing hydrogen is separated from the 1,3-butadiene-containing gas by gas-liquid separation to obtain a 1,3-butadiene-containing liquid. Step C3: The liquefied 1,3-butadiene-containing gas or the 1,3-butadiene-containing liquid is distilled to separate it into an ethylene-containing gas, a 1,3-butadiene-containing effluent, and an acetaldehyde-containing liquid. Step C4: The acetaldehyde-containing liquid is distilled to separate it into an acetaldehyde-containing gas and a residual liquid containing water.

[0062] In general, it is difficult to separate 1-butene, 2-butene, and isobutene from 1,3-butadiene by distillation or the like. In step C1, 1-butene, 2-butene, and isobutene are converted into 1,3-butadiene by a dehydrogenation reaction, thereby increasing the proportion of 1,3-butadiene. In the method for producing 1,3-butadiene of this embodiment, the hydrogen concentration in the intermediate gas or the mixed gas is controlled to less than 15% by volume, thereby suppressing the production of 1-butene, 2-butene, and isobutene.

[0063] When both step C1 and step C3 are performed in step C, step C1 may be performed before step C3, or step C1 may be performed after step 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 supplied to a third reactor, and 1-butene, 2-butene, and isobutene are dehydrogenated in the presence of a third catalyst under conditions of a pressure of −1.0 to 1.0 MPaG and a temperature of 200 to 550° C. to convert them to 1,3-butadiene. The third reactor in step C1 may be exemplified by the same embodiments as those exemplified for the first reactor.

[0064] The third catalyst may be any catalyst that promotes the dehydrogenation reaction of 1-butene, 2-butene, and isobutene, and examples thereof include molybdenum, tungsten, bismuth, tin, iron, and nickel. Among these, molybdenum is preferred from the viewpoint of the yield of 1,3-butadiene. The third catalyst may be used alone or in combination of two or more.

[0065] 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, and more preferably -0.3 to 0.3 MPaG. When the pressure in step C1 is at least the lower limit of the above range, the yield of 1,3-butadiene is improved. When the pressure in step C1 is at most the upper limit of the above range, a decrease in the yield of 1,3-butadiene due to excessive reaction can be suppressed.

[0066] 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, and more preferably 300 to 450°C. When the temperature in step C1 is at least the lower limit of the above range, the yield of 1,3-butadiene is improved. When the temperature in step C1 is at most the upper limit of the above range, a decrease in the yield of 1,3-butadiene due to excessive reaction can be suppressed.

[0067] 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 and obtain a 1,3-butadiene-containing liquid. When the ethanol-containing gas, the intermediate gas, or the mixed gas is diluted with a dilution gas such as nitrogen gas in step A2 or step B4-2, the dilution gas is also separated together with the hydrogen gas in step C2. The conditions for 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.

[0068] 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 a distillation column and distilled. This separates the ethylene-containing gas, 1,3-butadiene-containing effluent, and acetaldehyde-containing liquid. More specifically, for example, a tray-type distillation column or a packed distillation column is used, and the ethylene-containing gas is extracted from the top of the column, the acetaldehyde-containing liquid is extracted from the bottom, and the 1,3-butadiene-containing effluent is extracted from the middle. In step C3, two distillation columns may be used, with the ethylene-containing gas separated in the first distillation column and the 1,3-butadiene-containing effluent and acetaldehyde-containing liquid separated in the second distillation column.

[0069] The ethylene-containing gas contains, in addition to ethylene, propylene, methane, ethane, etc. When the liquefied 1,3-butadiene-containing gas obtained in step B3 is distilled without carrying out step C1, diluent gases such as hydrogen gas and nitrogen gas are separated together with the ethylene-containing gas in step C3. The acetaldehyde-containing liquid contains ethanol, water, and the like in addition to acetaldehyde.

[0070] When step C3 is performed without performing step C2, a gas containing hydrogen is separated together with the ethylene-containing gas in step C3. In addition, when the ethanol-containing gas, the intermediate gas, or the mixed gas is diluted with a dilution gas such as nitrogen gas in step A2 or step B4-2, the dilution gas is also separated together with the ethylene-containing gas in step C3.

[0071] 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 steps C3 and C4 are carried out in step C, the present invention is not limited to a mode in which steps C3 and C4 are carried out separately, and steps C3 and C4 may be carried out at the same time in one distillation column.

[0072] The acetaldehyde content 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 acetaldehyde content is equal to or more than the lower limit, the amount of by-products contained is small, which makes it easy to recover acetaldehyde and reuse the acetaldehyde-containing gas, thereby improving economic efficiency. The purity of the purified 1,3-butadiene obtained in step C is preferably 95.0% by mass or more, more preferably 99.0% by mass or more, and even more preferably 99.5% by mass or more. In this embodiment, the purification steps of steps C3 and C4 make it possible to obtain a 1,3-butadiene- and acetaldehyde-containing gas with higher purity.

[0073] [1,3-butadiene manufacturing equipment] The 1,3-butadiene production apparatus of this embodiment is a production apparatus that continuously produces 1,3-butadiene from an ethanol-containing gas. By using the 1,3-butadiene production apparatus of this embodiment, the above-mentioned 1,3-butadiene production method can be carried out. The 1,3-butadiene production apparatus of the present invention is equipped with a conversion means. The 1,3-butadiene production apparatus of the present invention may further be equipped with a gas preparation means and a purification means. Furthermore, the 1,3-butadiene production apparatus of the present invention may be equipped with a connecting pipe connecting the conversion means and the purification means.

[0074] The gas preparation means is a means for step A, and includes a vaporizer that vaporizes the ethanol feedstock to produce an ethanol-containing gas. The vaporizer may be any vaporizer that can vaporize the ethanol feedstock, and any known vaporizer can be used.

[0075] The conversion means is a means for steps B1 to B4-3 and steps B4-1 to B4-4, and includes a first reactor for carrying out step B1, a second reactor for carrying out step B3, and a hydrogen concentration reducer and / or diluter for carrying out steps B4-1 to B4-4 between the first and second reactors. The reactor may be any reactor capable of contacting a gas with a catalyst at a predetermined pressure and temperature. For example, a reactor having a sidewall through which a heat transfer medium is circulated may be filled with a catalyst to form a reaction bed, and the supplied gas may be contacted with the catalyst in the reaction bed. The reaction bed is not particularly limited, and examples thereof include a fixed bed, a moving bed, and a fluidized bed. Examples of the hydrogen concentration reducer include a gas-liquid separator, a gas separator, and a scrubber.

[0076] The conversion means may comprise two or more first reactors in parallel. The conversion means may comprise two or more second reactors in parallel.

[0077] The purification means is a means for step C, and includes, for example, equipment capable of purifying the 1,3-butadiene-containing gas, such as a gas-liquid separator, a distillation column, or a reactor. The purification means can be equipped with a reactor to carry out step C1. The purification means can be equipped with a gas-liquid separator to carry out step C2. The purification means can be equipped with a distillation column to carry out steps C3 and C4. The purification means may be equipped with one of the above-mentioned devices alone, or may be a combination of two or more of the devices.

[0078] [Embodiment] Hereinafter, an example of the method and apparatus for producing 1,3-butadiene according to this embodiment will be specifically described. FIG. 1 is a schematic diagram of an apparatus 100 for producing 1,3-butadiene according to this embodiment (hereinafter also referred to as "production apparatus 100"). Note that the dimensions of the drawings shown in the following description are merely examples, and the present invention is not necessarily limited thereto. Appropriate changes can be made within the scope of the present invention.

[0079] (manufacturing equipment) The production apparatus 100 comprises a gas preparation means 1, a conversion means 2, and a purification means 3. The gas preparation means 1 comprises a raw material storage section 102, a vaporizer 104, and a dilution gas storage section 106. The conversion means 2 comprises a first reactor 108, a hydrogen concentration reduction device 109, and a second reactor 110. The purification means 3 comprises a gas-liquid separator 112, a first distillation column 114, a third reactor 116, a second distillation column 118, and a recovery section 120.

[0080] Raw material storage section 102 and vaporizer 104 are connected by piping 10. Pipe 10 is provided with flow rate indicating controller 11. Vaporizer 104 and first reactor 108 are connected by piping 12. Pipe 12 is provided with, in this order from the vaporizer 104 side, a pressure indicating controller 14 that adjusts the flow rate based on the pressure inside vaporizer 104, a mixer 16, a heat exchanger 18, a temperature indicating controller 20, and a valve 22. Dilution gas storage section 106 is connected by piping 24 to a position in piping 12 between pressure indicating controller 14 and mixer 16. Pipe 24 is provided with a flow rate indicating controller 26.

[0081] The two or more parallel first reactors 108 and the hydrogen concentration reducer 109 are connected by a pipe 28 that branches off on the first reactor 108 side. A valve 30 is provided at each branch of the pipe 28 on the first reactor 108 side. The hydrogen concentration reducer 109 and two or more parallel second reactors 110 are connected by a pipe 29 that branches off on the second reactor 110 side. A valve 32 is provided at each branch of the pipe 29 on the second reactor 110 side. An analyzer 34 is provided in the pipe 28. In addition, a pipe 36 is provided that branches off from the pipe 12 between the vaporizer 104 and the pressure indicating regulator 14 and is connected between the branch of the pipe 28 on the first reactor 108 side and the analyzer 34. A flow rate indicating regulator 38 is provided in the pipe 36, so that the flow rate of the pipe 36 can be adjusted based on the analysis results of the analyzer 34. A mixer 33 and an analyzer 35 are provided in the pipe 29, in this order. In addition, a pipe 37 is provided that branches off from the pipe 24 between the dilution gas storage section 106 and the flow rate indicating regulator 26 and is connected to the pipe 29 between the hydrogen concentration reducer 109 and the analyzer 35. The flow rate indicating regulator 27 is provided on the pipe 37 so that the flow rate of the pipe 37 can be adjusted based on the analysis results of the analyzer 35. When performing step B4-1, the hydrogen concentration reducer 109 is a hydrogen concentration reducer 109-1 in which a heat exchanger 130, a gas-liquid separator 132, and a vaporizer 138 are installed in this order ( 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 to the pipe 134. The gas-liquid separator 132 and the vaporizer 138 are connected by the pipe 136. The vaporizer 138 is connected to the pipe 29. When step B4-3 is performed, a hydrogen concentration reducer 109-2 (not shown) is installed, which is equipped with a gas separator and a pipe for discharging a gas containing hydrogen, and when step B4-4 is performed, a hydrogen concentration reducer 109-3 (not shown) is installed, which is equipped with a scrubber and a vaporizer in this order. Note that it is sufficient to have at least one of the hydrogen concentration reducers 109-1 to 109-3.

[0082] Two or more parallel second reactors 110 and gas-liquid separators 112 are connected by a connecting pipe 40. In this embodiment, the connecting pipe 40 is a connecting 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 second reactor 110 side, and a heat exchanger 44 is provided at a position closer to the gas-liquid separator 112. Three bends R1, R2, and R3 are provided between the valve 42 and the heat exchanger 44 of the connecting pipe 40. Although there are three bends in this embodiment, the number of bends is not particularly limited. For example, the number of bends may be 0 to 20, or may be 1 to 10. A bypass 41 is provided in parallel to the connecting pipe 40, and a valve 45 is provided at each branch portion of the bypass 41. A valve 43 is provided at a portion of the connecting pipe 40 parallel to the bypass 41. The portion of the bypass 41 sandwiched by the valve 45 is removable. The portion of the connecting pipe 40 sandwiched by the valve 43 is removable. The gas-liquid separator 112 and the first distillation column 114 are connected by a pipe 46. A pump 48 and a level indicating regulator 50 that adjusts the flow rate based on the liquid level in the gas-liquid separator 112 are provided in this order on the pipe 46 from the gas-liquid separator 112 side.

[0083] A pipe 52 is connected to the top of the first distillation column 114. In addition, a pipe 54 is provided which is connected to the gas phase part of the gas-liquid separator 112 and joins the pipe 52. The middle part of the first distillation column 114 and the third reactor 116 are connected by a pipe 56. The third reactor 116 and the recovery section 120 are connected by a pipe 58.

[0084] The bottom of the first distillation column 114 and the second distillation column 118 are connected by a pipe 60 .

[0085] The connection pipe 40 may be a corrosion-resistant, heat-resistant stainless steel pipe, etc. The bypass 41 may be a steel pipe similar to the connection pipe 40, etc.

[0086] The 1,3-butadiene-containing gas discharged from the reactor 110 flows through the connecting pipe 40. For this reason, by-products generated in the conversion reaction may adhere to the inner surface (flow path) of the connecting pipe 40. If by-products adhere to the inner surface of the connecting pipe 40, clogging of the connecting pipe 40 or pressure loss may occur. For this reason, the connecting pipe 40 preferably has the following configuration.

[0087] By-products produced in the conversion step include impurities (heavy matters) contained in the brown oil and impurities (light matters) 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, and 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.

[0088] 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, and hexadiene.

[0089] A specific example of a bent portion in the connecting pipe is the bent portion Rm in the connecting 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-mentioned lower limit, by-products, particularly brown oil, are less likely to accumulate. The upper limit of the radius of curvature of the bent portion Rm is not particularly limited, and is, for example, 100 mm. The radius of curvature of the bent portion Rm is given by the radius of a circle when the curved inner surface of each bent portion Rm is considered as an arc. Here, m is the number of bent portions and is a natural number. m is, for example, preferably 1 to 20, more preferably 1 to 10, and even more preferably 1 to 5. In the present embodiment, m is 1 to 3. Note that, as shown in FIG. 1, m increases with increasing distance from the second reactor 110. For example, as shown in FIG. 1, in the case where there are three bent portions, the bent portion closest to the second reactor 110 is R1, and the bent portion furthest from the second reactor 110 is R3. In addition, when two straight pipes are connected with a joint or the like to form a bent portion, the radius of curvature of the joint or the like is regarded as the radius of curvature of the bent portion of the connecting pipe 40.

[0090] The radius of curvature of the bent part Rm (r Rm (mm)) is the temperature T Rm (K) divided by (r Rm / T Rm ) is preferably 0.03 to 100 mm / K, more preferably 0.05 to 80 mm / K, and even more preferably 0.07 to 60 mm / K. Rm / T Rm is equal to or greater than the lower limit, the temperature T Rm The high viscosity of the oil increases the fluidity of the brown oil, making it difficult for the brown oil to accumulate on the inner surface of the bent part Rm. Rm / T Rm If is less than the upper limit, the radius of curvature (r Rm ) is large, brown oil is less likely to accumulate on the inner surface of the bent part Rm.

[0091] The radius of curvature of the bent part Rm (r Rm (mm)) is the radius of the piping at the bend Rm (r' Rm (mm)) divided by (r Rm / r' Rm ) is preferably 0.02 to 1.00, more preferably 0.03 to 0.80, and even more preferably 0.05 to 0.60. Rm / r' Rm If the radius of the pipe at the bent portion Rm (r' Rm (mm)) is small, which improves the dispersibility of brown oil, making it difficult for brown oil to accumulate on the inner surface of the bent portion Rm.Rm / r' Rm When the radius of curvature (r Rm Since the radius (r' (mm)) of the piping at the bend Rm is large, brown oil is less likely to accumulate on the inner surface of the bend Rm. Rm (mm)) means the length obtained by dividing the inner diameter of the pipe at the bend Rm by 2.

[0092] The radius of curvature of the bent part Rm (r Rm (mm)) of the by-products adhering to the inner surface of the bent part Rm (μ Rm (mPa·s)) divided by (r Rm / μ Rm ) is preferably 0.04 mm / mPa·s or more, more preferably 0.05 mm / mPa·s or more, and even more preferably 0.06 mm / mPa·s or more. Rm / μ Rm is equal to or greater than the lower limit, the radius of curvature (r Rm (mm)) is large, so brown oil is less likely to accumulate on the inner surface of the bent part Rm. Rm / μ Rm The upper limit of the viscosity (μ Rm The viscosity (mPa·s) is the value measured at 190°C using a Brookfield viscometer after sampling 10 mL of the by-product adhering to the inner surface of the bent portion Rm.

[0093] The connection pipe 40 has an arithmetic mean roughness (Ra 40 (μm)) is preferably 1.02 μm or less, more preferably 1.00 μm or less, even 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, 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, for example, 0.01 μm. The arithmetic mean roughness of the inner surface of the connection pipe 40 is the arithmetic mean roughness measured using a Handysurf E-35B manufactured by Tokyo Seimitsu Co., Ltd. using a cutoff value of 2.5 according to the roughness curve described in JIS B0601:2013. The arithmetic mean 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.

[0094] The temperature of the inner surface of the connecting pipe 40 is T 40 (K), the arithmetic mean roughness (Ra 40 (μm)) and T 40 The product of (Ra 40 T 40 ) is preferably 0.1 to 750 μm·K, more preferably 0.5 to 550 μm·K, and even more preferably 1.0 to 480 μm·K. 40 T 40 is equal to or greater than the lower limit, the temperature T 40 Since the flowability of the brown oil is increased, the brown oil is less likely to accumulate on the inner surface of the connecting pipe 40. 40 T 40 When is equal to or less than the upper limit, Ra 40 Since the diameter is small, brown oil is less likely to accumulate on the inner surface of the connecting pipe 40. In addition, T 40 (K) is the temperature of the inner surface of the connecting pipe 40 at the position having the arithmetic mean roughness.

[0095] The pipe radius of the connecting pipe 40 is r 40 (mm), the arithmetic mean roughness (Ra 40 (μm)) and r 40 The product of (Ra 40 ·r 40 ) is 0.002 to 1 mm 2 is preferable, and 0.005 to 0.8 mm 2 is more preferable, and 0.01 to 0.5 mm 2 is more preferable. 40 ·r 40 If is equal to or greater than the lower limit, Ra 40 Since the diameter is small, brown oil is less likely to accumulate on the inner surface of the connecting pipe 40. 40 ·r 40 If is less than the upper limit, the pipe radius r 40Since the diameter is wide and the dispersibility of the brown oil is improved, the brown oil is less likely to accumulate on the inner surface of the connecting pipe 40. In addition, r 40 (mm) is the radius of the pipe (1 / 2 the inner diameter of the pipe) at the position where the arithmetic mean roughness is found in the connecting pipe 40.

[0096] The viscosity of the by-product in the connecting pipe 40 is μ 40 (mPa·s), the arithmetic mean roughness (Ra 40 (μm) to μ 40 The value divided by (Ra 40 / μ 40 ) is preferably 0.0001 μm / mPa·s or more, more preferably 0.0002 μm / mPa·s or more, and even more preferably 0.0005 μm / mPa·s or more. 40 / μ 40 If is equal to or greater than the lower limit, Ra 40 Since the diameter is small, brown oil is less likely to accumulate on the inner surface of the connecting pipe 40. 40 / μ 40 The upper limit is not particularly limited, but is set to, for example, 0.01 μm / mPa·s. In addition, μ 40 (mPa·s) is the viscosity of the by-product at 190°C at the position in the connecting pipe 40 where the arithmetic mean roughness is located.

[0097] The inner surface of the connection pipe 40 is preferably coated with an organic compound having 6 to 12 carbon atoms. By coating the inner surface of the connection pipe 40 with an organic compound having 6 to 12 carbon atoms, adhesion of brown oil to the inner surface of the connection pipe 40 can be suppressed. Examples of organic compounds having 6 to 12 carbon atoms include hydrocarbons, alcohols, aldehydes, ketones, ethers, esters, carboxylic acids, and phenols having 7 to 10 carbon atoms. More specific examples include δ-hexanolactone, 2,6-diisopropylphenol, and 1-adamantyl methyl ketone.

[0098] As used herein, "coated" refers to a coating layer having a thickness of 100 mm or less formed on the inner surface of the connecting pipe 40. The thickness of the coating layer is preferably 0.001 to 100 mm, more preferably 0.01 to 10 mm. When the thickness of the coating layer is equal to or greater than the above-mentioned lower limit, 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-mentioned upper limit, clogging and pressure loss of the pipe can be suppressed. The thickness of the coating layer can be measured by observing, with a microscope or the like, a cross section of the connecting pipe 40 cut in the thickness direction at the bent portion of the connecting pipe 40 closest to the reactor 110. In this case, the thickness of the coating layer is measured at 10 locations randomly selected from the flow path at the bent portion of the connecting pipe 40 closest to the reactor 110, and the arithmetic mean value of the measured values ​​is defined as the "coating layer thickness." The "bend portion of the connecting pipe 40 closest to the reactor 110" refers to the portion of the connecting pipe 40 having a curvature radius of 100 mm or less and closest to the reactor 110. In this embodiment, the bend portion R1 is the bend portion of the connecting pipe 40 closest to the reactor 110.

[0099] The temperature of the inner surface of the bent part of the connecting pipe 40 closest to the reactor 110 (T R1 (K)) is the temperature of the inner surface of the reactor 110 (T 110 The temperature is preferably -250°C or higher, more preferably -200°C or higher, and even more preferably -150°C or higher relative to (K, the temperature at the central part of the catalyst layer). When the temperature of the inner surface of the bent part of the connecting pipe 40 closest to the reactor 110 is equal to or higher than the above lower limit, it is possible to prevent brown oil from adhering to the inner surface of the connecting pipe 40. The upper limit of the temperature of the inner surface of the bent part of the connecting pipe 40 closest to the reactor 110 is not particularly limited, but is set to ±0°C relative to the temperature of the inner surface of the reactor 110, for example.

[0100] The temperature drop (hereinafter simply referred to as "temperature drop") on the inner surface of the bent portion of the connecting pipe 40 closest to the reactor 110 is calculated by the temperature (T 110(K)), it is preferably 70% or less, more preferably 60% or less, and even more preferably 50% or less. If the temperature drop is equal to or less than the above upper limit, it is possible to prevent brown oil from adhering to the inner surface of the connecting pipe 40. The lower limit of the temperature drop is not particularly limited, but is, for example, 0%. The temperature drop is calculated using the following formula (3). Temperature drop (%)=(T 110 (K)-T R1 (K)) / T 110 (K) × 100 (3)

[0101] The pipe radius (r') of the connecting pipe 40 at the bend closest to the reactor 110 R1 The pipe radius (r' (mm)) is preferably 50 to 1000 mm, more preferably 80 to 800 mm, and even more preferably 100 to 500 mm. R1 When the radius of the pipe (r' (mm)) is equal to or greater than the lower limit, adhesion of brown oil to the inner surface of the connecting pipe 40 can be suppressed. R1 When the radius of the pipe (r' (mm)) is equal to or less than the upper limit, maintenance of the connection pipe 40 is easy. R1 (mm)) is the radius of the pipe at the bend R1 (1 / 2 of the inner diameter of the pipe).

[0102] The reduction ratio of the pipe radius at the bent portion of the connecting pipe 40 closest to the reactor 110 is the pipe radius before bending (r' 前 The reduction ratio of the pipe radius is preferably 70% or less, more preferably 60% or less, and even more preferably 50% or less, of the inner diameter (mm) of the pipe upstream of the bend (half the inner diameter of the pipe upstream of the bend). When the reduction ratio of the pipe radius is equal to or less than the above upper limit, adhesion of brown oil to the inner surface of the connecting pipe 40 can be suppressed. The lower limit of the reduction ratio of the pipe radius is not particularly limited, but is set to 0%, for example. The reduction ratio of the pipe radius can be calculated using the following formula (4): Pipe radius reduction rate (%) = (r' 前 (mm)-r' 後 (mm)) / r' 前 (mm) × 100 (4) In formula (4), r' 後(mm) is the radius of the pipe after bending (1 / 2 of the inner diameter of the pipe after the bend).

[0103] The main components of the by-products that may adhere to the inner surface of the bent portion of the connecting pipe 40 closest to the reactor 110 include compounds with four or more carbon atoms that are produced by polymerization of acetaldehyde. Examples of these compounds include δ-hexanolactone, 2,6-diisopropylphenol, and 1-adamantyl methyl ketone. These compounds can be detected by analyzing the by-products captured in the bypass 41 of the production apparatus 100A by gas chromatography (GC). The viscosity (μ R1 The viscosity of the by-product (μ R1 The viscosity (μ (mPa·s)) of the by-product is preferably 100 to 800 mPa·s. R1 (mPa·s)) is the viscosity measured at 20°C using a coaxial double cylindrical rotational viscometer (constant inner cylinder speed method) as specified in JIS Z8803:2011.

[0104] A bypass 41 is provided in parallel to the connecting pipe 40. By closing the valve 43 and opening the valve 45, the 1,3-butadiene-containing gas can be passed through the bypass 41. The arithmetic mean roughness (Ra 41 ) to Ra 40 and the temperature T 41 T 40 By making the temperature lower than 100°C, it becomes easier for by-products, especially brown oil, to accumulate on the inner surface of the bypass 41. In other words, the bypass 41 can be used as a trap for by-products. The function as a trap can be further improved by providing a bent section with a small radius of curvature in the bypass 41 or by installing a filter with an appropriate lattice size.

[0105] The portion of the bypass 41 that is sandwiched by the valve 45 is removable. By making the bypass 41 removable, if by-products adhere to the inner surface, the bypass can be replaced with a new one or the inner surface can be cleaned, allowing for maintenance without stopping the continuous operation of the manufacturing apparatus 100. When performing maintenance on the bypass 41, the valve 45 is closed and the bypass 41 is removed. Furthermore, in addition to the trap using the bypass piping, the manufacturing apparatus can also be maintained by installing a removable filter of an appropriate lattice size on the connecting piping and / or the bypass piping and appropriately removing adhered and accumulated by-products.

[0106] When by-products adhere to the inner surface of the connecting 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. The portion of the connecting pipe 40 that is sandwiched by the valve 43 is removable, so that this portion can be subjected to maintenance.

[0107] The connecting pipe 40 may be provided with a bypass other than the bypass 41. By providing a bypass other than the bypass 41, a larger amount of by-products can be recovered. The number of bypasses may be one or may be two or more.

[0108] Hereinafter, the method for producing 1,3-butadiene according to the first embodiment using the production apparatus 100 will be described. An ethanol feedstock is supplied from raw material storage section 102 to vaporizer 104 through pipe 10, and the ethanol feedstock is vaporized under conditions of a pressure of -1.0 MPaG to 1.0 MPaG and a temperature of -100°C to 200°C to produce an ethanol-containing gas (step A1). The ethanol-containing gas is sent from vaporizer 104 to pipe 12, and nitrogen gas (dilution gas) is joined via pipe 24 from dilution gas storage section 106, and the two are mixed in mixer 16. The ethanol concentration of the ethanol-containing gas is then adjusted to within a range of 0.1% to 100% by volume (step A2).

[0109] The ethanol-containing gas with the adjusted ethanol concentration is heated in a heat exchanger 18 and supplied to two or more parallel first reactors 108. In each of the first reactors 108, the ethanol-containing gas is brought into contact with a first catalyst under conditions of, for example, a pressure of 0 to 1.0 MPaG and a temperature of 50 to 500°C, thereby converting a portion of the ethanol in the ethanol-containing gas to acetaldehyde (step B1). An intermediate gas containing ethanol and acetaldehyde is sent from each of the first reactors 108 to a pipe 28.

[0110] A portion 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 results, the flow rate of the ethanol-containing gas from the pipe 36 is adjusted by the flow rate indicator / adjuster 38, and the molar ratio (ethanol / aldehyde) of the mixed gas supplied to the second reactor 110 is adjusted within the range of 1 to 100 (step B2). Specifically, if the molar ratio (ethanol / aldehyde) decreases during operation of the production process, the molar ratio (ethanol / aldehyde) can be increased by increasing the flow rate of the ethanol-containing gas supplied from the pipe 36. Conversely, if the molar ratio (ethanol / aldehyde) increases, the molar ratio (ethanol / aldehyde) can be decreased by decreasing the flow rate of the ethanol-containing gas supplied from the pipe 36.

[0111] The intermediate gas or the mixed gas is sent to the hydrogen concentration reducer 109. The intermediate gas or the mixed gas is separated into ethanol and acetaldehyde, and a gas containing hydrogen. In one embodiment, when the hydrogen concentration reducer 109 is the above-described hydrogen concentration reducer 109-1, the intermediate gas or the mixed gas is cooled by a heat exchanger 130 and supplied to a gas-liquid separator 132. The gas containing hydrogen is separated from the intermediate gas or the mixed gas in the gas-liquid separator 132. Specifically, the gas-liquid separation can separate the intermediate gas or the mixed gas 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 a vaporizer 138 and vaporized again, and then supplied to the second reactor 110 via a pipe 29 as the intermediate gas or the mixed gas. The hydrogen-containing gas separated in the gas-liquid separator 132 is treated externally via a pipe 134. In another embodiment, when the hydrogen concentration reducer 109 is the above-described hydrogen concentration reducer 109-2, the intermediate gas or the mixed gas is supplied to a gas separator and separated into a gas containing ethanol and acetaldehyde and a gas containing hydrogen (step B4-3). The gas containing hydrogen may be discharged from a pipe (not shown) for discharging a gas containing hydrogen. The 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 reducer 109 is the above-described hydrogen concentration reducer 109-3, the intermediate gas or the mixed gas is subjected to gas-liquid separation using a scrubber and separated into a liquid containing ethanol and acetaldehyde and a gas containing hydrogen (step B4-4). In this case, the liquid containing ethanol and acetaldehyde is heated by a vaporizer and vaporized again, and then supplied to the second reactor 110 as the intermediate gas or mixed gas. The gas containing hydrogen may be discharged from a pipe (not shown) for discharging a gas containing hydrogen.

[0112] The analyzer 35 analyzes the hydrogen concentration in the intermediate gas or the mixed gas supplied to the second reactor 110. Based on the results, the flow rate of nitrogen gas (dilution gas) from the pipe 37 is adjusted by the flow rate indicating controller 27 to control the hydrogen concentration in the intermediate gas or mixed gas supplied to the second reactor 110 to less than 15% by volume (step B4-2). That is, the dilution gas storage unit 106, the pipe 37, the flow rate indicating controller 27, the pipe 29, and the analyzer 35 constitute the dilution device of this embodiment.

[0113] The intermediate gas or the mixed gas is supplied to two or more second reactors 110 arranged in parallel. In each second reactor 110, the intermediate gas or the mixed gas is brought into contact with a second catalyst under conditions of, for example, a pressure of 0 to 1.0 MPaG and a temperature of 50 to 500°C, thereby converting the ethanol and acetaldehyde in the intermediate gas or the mixed gas into 1,3-butadiene (step B3). The 1,3-butadiene-containing gas is sent from each second reactor 110 to a connecting pipe 40.

[0114] The 1,3-butadiene-containing gas is cooled by a heat exchanger 44 and supplied to a gas-liquid separator 112. In the gas-liquid separator 112, a gas containing hydrogen is separated from the 1,3-butadiene-containing gas by gas-liquid separation. Specifically, the 1,3-butadiene-containing gas is separated into hydrogen gas, nitrogen gas (dilution gas), and a 1,3-butadiene-containing liquid by gas-liquid separation (step C2). Pump 48 is driven to supply the 1,3-butadiene-containing liquid from the gas-liquid separator 112 through pipe 46 to a 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 through pipe 52, an acetaldehyde-containing liquid is extracted from the bottom through pipe 60, and a 1,3-butadiene-containing effluent is extracted from the middle through pipe 56, and each is separated (step C3). The ethylene-containing gas extracted into the pipe 52 is combined with hydrogen gas and nitrogen gas (dilution gas) extracted into the pipe 54 from the gas phase of the gas-liquid separator 112, and treated as waste gas.

[0115] The 1,3-butadiene-containing effluent withdrawn through pipe 56 is supplied to a third reactor 116, where the 1,3-butadiene-containing effluent is dehydrogenated in the presence of a third catalyst to convert butenes (1-butene, 2-butene, isobutene) in the 1,3-butadiene-containing effluent to 1,3-butadiene (step C1). Purified 1,3-butadiene is sent from the third reactor 116 through pipe 58 to a recovery section 120 for recovery.

[0116] The acetaldehyde-containing liquid extracted from the bottom of the first distillation column 114 into pipe 60 is supplied to the second distillation column 118 and distilled. A residual liquid containing water is extracted from the bottom of the second distillation column 118 into pipe 64, and an acetaldehyde-containing gas is extracted from the top of the column (step C4).

[0117] In the manufacturing apparatus 100 having the above configuration, it is preferable to install a dust collector (not shown) in the paths of the pipes 28 and 29 connecting the first reactor 108 and the second reactor 110 to prevent the first catalyst from being mixed into the second reactor 110. By installing such a dust collector, the conversion reaction from ethanol to acetaldehyde in the second reactor 110 can be suppressed, and the conversion of ethanol to 1,3-butadiene by the second catalyst, which requires ethanol, can be stably maintained. The dust collector is not particularly limited, but examples thereof include a cyclone, a bag filter, and a packed bed filter.

[0118] Furthermore, in the production apparatus 100, in order to prevent the first catalyst or the second catalyst from flowing out to the downstream side of the first reactor 108 or the second reactor 110, it is preferable to install a catalyst holding unit (not shown) on the downstream side of each of these reactors, specifically, on the pipes 28, 29 and connecting pipe 40. By installing such a catalyst retention unit, it is possible to prevent the first catalyst and the second catalyst that have flowed out from the first reactor 108 or the second reactor 110 from accumulating in piping or the like outside of these reactors. This makes it possible to suppress the generation of carbon-containing substances and a decrease in the yield of 1,3-butadiene, which would otherwise occur if the conversion reaction from ethanol, or ethanol and acetaldehyde, to 1,3-butadiene occurs outside of the reactors. The catalyst retention unit as described above is not particularly limited, and examples thereof include a grid support, a perforated plate, and an alumina ball.

[0119] As described above, this embodiment carries out steps A to C. In particular, by carrying out step B4-1 or step B4-2, the hydrogen concentration in the intermediate gas or mixed gas supplied to the second reactor 110 becomes less than 15% by volume, which makes it possible to suppress a decrease in the activity of the second catalyst and side reactions, and improves the yield of 1,3-butadiene.

[0120] The method for producing 1,3-butadiene of the present invention is not limited to the above-described embodiment, and the configurations described in each step can be appropriately combined. The components in the above-described embodiment can be appropriately replaced with well-known components within the scope of the present invention. [Example]

[0121] EXAMPLES The present invention will be explained in more detail below with reference to examples and comparative examples, but the present invention is not limited to these examples.

[0122] 1. Catalyst Preparation First, 1.0 g of hafnium chloride (HfCl4: 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 support (silica porous particles manufactured by Fuji Silysia Chemical 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 for 1 hour under atmospheric pressure in an ultrasonic washer, and then the solution was separated by filtration. The recovered porous body was dried at 110°C for 4 hours and then calcined at 400°C for 4.5 hours to produce a catalyst.

[0123] 2. Catalyst evaluation (production of 1,3-butadiene) Using the catalysts produced in each of the Examples and Comparative Examples, ethanol and acetaldehyde were converted into 1,3-butadiene (hereinafter also referred to as "BD"), and the yield of 1,3-butadiene was determined. Specifically, first, 1.0 g of the catalyst was packed into a stainless steel cylindrical reactor having a diameter of 1 / 2 inch (1.27 cm) and a length of 15.7 inches (40 cm) 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 gas hourly space velocity (GHSV) for the catalyst was 1200 h -1 The raw materials were fed to the reactor, and a product gas containing 1,3-butadiene was obtained. One hour after the start of the feedstock supply, the produced gas was collected. The recovered product gases were then analyzed by gas chromatography to determine the selectivity for BD, the conversion rates of ethanol and acetaldehyde, and the yield of BD ([conversion rate of ethanol and acetaldehyde] × [selectivity for BD]). The "selectivity for BD" refers to the percentage of the number of moles of ethanol and acetaldehyde converted to BD out of the number of moles of ethanol and acetaldehyde contained in the raw material consumed in the reaction using the catalyst. Furthermore, the "conversion rate of ethanol and acetaldehyde" refers to the percentage of the number of moles of ethanol and acetaldehyde consumed out of the number of moles of ethanol and acetaldehyde contained in the raw material.

[0124] [Comparative Example 1] The raw material used was a mixed gas of 35% by volume of ethanol, 35% by volume of acetaldehyde, and 30% by volume of hydrogen. Note that the volume percentages are calculated on a gas basis, and the same applies below.

[0125] Comparative Example 2 As a raw material, a mixed gas of 35% by volume of ethanol, 35% by volume of acetaldehyde, 15% by volume of nitrogen, and 15% by volume of hydrogen was used.

[0126] [Example 1] The raw material used was a mixed gas of 35% by volume of ethanol, 35% by volume of acetaldehyde, 20% by volume of nitrogen, and 10% by volume of hydrogen.

[0127] [Example 2] As a raw material, a mixed gas of 35% by volume of ethanol, 35% by volume of acetaldehyde, 25% by volume of nitrogen, and 5% by volume of hydrogen was used.

[0128] [Example 3] As a raw material, a mixed gas of 35% by volume of ethanol, 35% by volume of acetaldehyde, and 30% by volume of nitrogen was used.

[0129] [Table 1]

[0130] As shown in Table 1, it was found that in Comparative Examples 1 and 2, in which the hydrogen concentration in the raw material for the second conversion step was 15% by volume or more, the BD yield was lower than in Examples 1 to 3, in which the hydrogen concentration was less than 15% by volume. That is, as described above, it is believed that 1,3-butadiene can be continuously produced at a high yield 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. [Explanation of symbols]

[0131] 1...gas preparation means, 2...conversion means, 3...purification means, 10...piping, 11...flow rate indicator, 12...piping, 14...pressure indicating controller, 16...mixer, 18...heat exchanger, 20...temperature indicating controller, 22...valve, 24...piping, 26...flow rate indicator controller, 27...flow rate indicator controller, 28...piping, 29...piping, 30...valve, 32...valve, 34...analyzer, 33...mixer, 35...analyzer, 36...piping, 37...piping, 38...flow rate indicator controller, 40...connecting piping, 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 production apparatus, 102...raw material storage section, 104...vaporizer, 106...dilution gas storage section, 108...first reactor, 109 (109-1)...hydrogen concentration reduction device, 110...second reactor, 112...gas-liquid separator, 114...first distillation column, 116...third reactor, 118...second distillation column, 120...recovery section, 130...heat exchanger, 132...gas-liquid separator, 134...piping, 136...piping, 138...vaporizer

Claims

[Claim 1] A method for producing 1,3-butadiene by continuously producing 1,3-butadiene from an ethanol-containing gas, comprising: a first conversion step in which the ethanol-containing gas is brought into contact with a first catalyst to convert a portion of the ethanol in the ethanol-containing gas into acetaldehyde, thereby obtaining an intermediate gas containing ethanol and acetaldehyde; a second conversion step of contacting the intermediate gas or a mixed gas obtained by mixing the intermediate gas with a gas containing ethanol with a second catalyst to convert ethanol and acetaldehyde in the intermediate gas or the mixed gas into 1,3-butadiene and obtain a 1,3-butadiene-containing gas; The 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.

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