Method for producing 1,3-butadiene

Abstract

Provided is a method for producing 1,3-butadiene from an ethanol-containing raw material, the method comprising, in this order: a conversion step in which the ethanol-containing raw material is supplied to a reactor in which a catalyst is held to obtain an intermediate gas that includes at least 1,3-butadiene, ethanol, and impurities that are organic substances with boiling points higher than that of the ethanol; a separation step in which the intermediate gas is cooled to a temperature above the boiling point of the ethanol and below the exit temperature of the reactor to cause at least part of the impurities to condense, and thereafter, the intermediate gas is supplied to a separation means equipped with a filter for gas-liquid separation of the agglomerated impurities from the intermediate gas to obtain a mixed gas; and a distillation step in which the ethanol is separated from the mixed gas.　

Description

Process for producing 1,3-butadiene

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

[0002] In the ETB (Ethanol to Butadiene) process for producing 1,3-butadiene from a raw material containing ethanol, there are a one-step method in which ethanol is converted to butadiene in one step and a two-step method in which ethanol is dehydrogenated to synthesize acetaldehyde and butadiene is synthesized from ethanol and acetaldehyde, as disclosed in Patent Documents 1 and 2.

[0003] It is known that a large amount of by-products are generated in the ETB process. These by-products include high molecular compounds that are soluble in ethanol but insoluble in water. If these high molecular compounds are not diluted with a large excess of ethanol, there is a recognized problem of clogging the apparatus (see Patent Document 2).

[0004] For example, these high molecular compounds become a problem in a distillation column for separating water generated by the reaction and unreacted ethanol. After separating ethanol, a residue composed of water is obtained. If the high molecular compound insoluble in water precipitates alone and adheres to the apparatus, it becomes difficult to remove.

[0005] In response to these problems, Patent Document 2 discloses a method of using liquid phase extraction, extracting, distilling, and further separating from the extract. Further, Patent Document 3 discloses a method of extracting diolefins such as butadiene contained in a hydrocarbon raw material by liquid phase extraction.

[0006] Patent Document 4 discloses a method of removing generated impurities by liquid-liquid extraction in a method for producing butadiene from ethanol in order to improve production efficiency and safety.

[0007] Japanese Patent Application Laid-Open No. 2017-532318, International Publication No. 2016 / 042096, International Publication No. 2015 / 079041, International Publication No. 2019 / 162586

[0008] The above method requires the use of a large amount of solvent for extraction or back-extraction, making solvent disposal a challenge. Furthermore, introducing such a system involves combining multiple devices, resulting in a large-scale facility. The present invention aims to provide a method for producing 1,3-butadiene that does not require the use of a new solvent, does not require the combination of complex devices, and avoids blockages in tubing, heat exchangers, compressors, distillation columns, etc., enabling stable continuous operation.

[0009] To solve the above problems, one aspect of the present invention includes the following aspects: [1] A method for producing 1,3-butadiene from an ethanol-containing raw material, comprising in this order: a conversion step of supplying the ethanol-containing raw material to a reactor holding a catalyst to obtain an intermediate gas containing at least 1,3-butadiene, ethanol, and impurities which are organic substances having a higher boiling point than ethanol; a separation step of cooling the intermediate gas to a temperature above the boiling point of ethanol and below the outlet temperature of the reactor to condense at least a portion of the impurities, then supplying the intermediate gas to a separation means equipped with a filter, and separating the condensed impurities from the intermediate gas by gas-liquid separation to obtain a mixed gas; and a distillation step of separating ethanol from the mixed gas. [2] The method for producing 1,3-butadiene according to [1], wherein the ethanol obtained by the distillation step is used as part of the ethanol-containing raw material. [3] The method for producing 1,3-butadiene according to [1] or [2], wherein the separation means is a coalescer. [4] The method for producing 1,3-butadiene according to any one of [1] to [3], wherein the separation means further comprises a gravity separator. [5] The method for producing 1,3-butadiene according to any one of [1] to [4], wherein the boiling point of the impurities is 80°C or more and less than 600°C at atmospheric pressure. [6] The method for producing 1,3-butadiene according to any one of [1] to [5], wherein the separation step comprises at least a first separation step and a second separation step carried out at a lower temperature than the first separation step, and the mixed gas obtained in the first separation step is supplied to the second separation step. [7] The method for producing 1,3-butadiene according to [3], further comprising a washing step with an organic solvent.

[0010] According to the present invention, it is possible to provide a method for producing 1,3-butadiene that does not require the use of a new solvent, does not require a complex combination of equipment, and furthermore, avoids blockages in tubing, heat exchangers, compressors, distillation columns, etc., enabling stable continuous operation. The above effects can be achieved by using a physical method that is not subject to equilibrium thermodynamic constraints.

[0011] This is an explanatory diagram illustrating a method for producing 1,3-butadiene according to the first embodiment. This is a diagram illustrating a reactor used in a method in which the conversion step is carried out by a one-stage method. This is a diagram illustrating a reactor used in a method in which the conversion step is carried out by a two-stage method. This is an explanatory diagram illustrating one aspect of the separation step. This is an explanatory diagram illustrating a method for producing 1,3-butadiene according to the second embodiment.

[0012] Figure 1 is an explanatory diagram illustrating a method for producing 1,3-butadiene according to the first embodiment. This method is a method for producing 1,3-butadiene from an ethanol-containing raw material and comprises the following steps (1) to (3).

[0013] (1) A conversion step in which an ethanol-containing raw material is supplied to a reactor holding a catalyst to obtain an intermediate gas containing at least 1,3-butadiene, ethanol, and impurities which are organic substances with a higher boiling point than ethanol. (2) A separation step in which the intermediate gas is cooled to a temperature above the boiling point of ethanol and below the outlet temperature of the reactor to condense at least a portion of the impurities, and then the intermediate gas is supplied to a separation means equipped with a filter to separate the condensed impurities from the intermediate gas into a gas-liquid mixture. (3) A distillation step to separate ethanol from the mixture.

[0014] The following describes each process with reference to the diagrams.

[0015] (1) Conversion process The conversion process involves supplying ethanol-containing raw material 20 to a reactor 10 that holds a catalyst. In one embodiment of the present invention, the conversion process may be a one-step method (Lebedev method) in which ethanol is converted to butadiene in one step, or it may be a two-step method (Ostromislensky method) in which ethanol is first dehydrogenated to synthesize acetaldehyde, and then butadiene is synthesized from ethanol and acetaldehyde.

[0016] In an embodiment in which the conversion process is carried out by a one-stage method, the reactor 10 is preferably the reactor 11 shown in Figure 2. When the ethanol-containing raw material 20 is brought into contact with the catalyst 11c packed in the reactor 11, the ethanol is decomposed into acetaldehyde, and further, the ethanol and acetaldehyde are converted to 1,3-butadiene in the presence of the catalyst 11c. This process yields an intermediate gas 22 containing at least 1,3-butadiene, ethanol, and impurities which are organic substances with a higher boiling point than ethanol.

[0017] In this specification, "impurities" refer to by-products obtained during the synthesis of butadiene from ethanol, and these are mainly due to the polymerization of conjugated dienes and the high molecular weight conversion reaction of alkenes by the Diels-Alder reaction of conjugated dienes with by-products such as ethylene. The polymerization of conjugated dienes and the Diels-Alder reaction proceed by catalytic reactions as well as by uncatalyzed reactions.

[0018] For the catalyst 11c used in the one-stage process, aluminum oxide, iron oxide, silicon oxide, etc., can be used. The reactor 11 is not particularly limited as long as it can bring the ethanol-containing raw material 20 and the catalyst into contact at the desired pressure and temperature, and known configurations can be adopted.

[0019] In an embodiment in which the conversion process is carried out by a two-stage method, the reactor 10 preferably comprises a first reactor 12a holding the first catalyst 12x shown in Figure 3, and a second reactor 12b holding the second catalyst 12y. When the conversion process is carried out by a two-stage method, the ethanol-containing raw material 20 is supplied to the first reactor 12a holding the first catalyst 12x. The ethanol-containing raw material 20 is brought into contact with the first catalyst 12x packed in the first reactor 12a, and a portion of the ethanol contained in the ethanol-containing raw material 20 is dehydrogenated and converted to acetaldehyde, thereby obtaining a first intermediate gas 21 containing ethanol and acetaldehyde.

[0020] The first reactor 12a is not particularly limited as long as it can bring the ethanol-containing raw material 20 and the first catalyst 12x into contact at a desired pressure and temperature, and a known configuration can be adopted. Furthermore, two or more reactors may be installed in parallel as the first reactor 12a. The number of reactors to be installed can be set as appropriate, for example, 2 to 5.

[0021] The first catalyst 12x can be any catalyst that converts ethanol to acetaldehyde, such as a mixture of chromium oxide and copper oxide, zinc oxide, or a mixture of copper oxide and silicon oxide.

[0022] Next, the obtained first intermediate gas 21 is supplied to the second reactor 12b, which holds the second catalyst 12y. The first intermediate gas 21 is brought into contact with the second catalyst 12y packed in the second reactor 12b, converting the ethanol and acetaldehyde contained in the first intermediate gas 21 to 1,3-butadiene. This step yields an intermediate gas 22 containing at least 1,3-butadiene, ethanol, and impurities which are organic substances with a higher boiling point than ethanol.

[0023] The second reactor 12b is not particularly limited as long as it can bring the first intermediate gas 21 and the second catalyst 12y into contact at a desired pressure and temperature, and a known configuration can be adopted. Furthermore, two or more reactors may be installed in parallel as the second reactor 12b. The number of reactors to be installed can be set as appropriate, for example, 2 to 20.

[0024] The second catalyst 12y can be any catalyst that converts ethanol and acetaldehyde to 1,3-butadiene, such as tantalum, zirconium, niobium, hafnium, magnesium, zinc, or silicon.

[0025] From the intermediate gas 22, which is a reaction product obtained by the ETB reaction, 1,3-butadiene is separated by known separation means such as distillation or extraction to obtain 1,3-butadiene.

[0026] The intermediate gas 22 contains at least 1,3-butadiene, a reaction product obtained by the ETB reaction, ethanol, which is an unreacted raw material, and impurities, which are organic substances with a higher boiling point than ethanol.

[0027] The impurities are hydrophobic polymers produced during catalytic and thermal reactions in the conversion process. These impurities are organic substances with higher boiling points than ethanol, more specifically, organic substances with boiling points between 80°C and 600°C at atmospheric pressure. Because the conversion process involves high reaction temperatures, the intermediate gas 22 obtained from the conversion process is a high-temperature gas exceeding the boiling point of the impurities. Therefore, the impurities are vaporized in the intermediate gas 22.

[0028] In a later process, the temperature of the intermediate gas 22 decreases, falling below the boiling point of the impurities. If the impurities precipitate as individual particles, this can cause blockages in the piping, heat exchangers, compressors, and distillation columns. Therefore, in this embodiment, the impurities are separated and removed from the intermediate gas 22 in the subsequent separation process.

[0029] (2) Separation process The separation process is a process of separating impurities contained in the intermediate gas 22 into gas and liquid. The intermediate gas 22 is cooled to a temperature above the boiling point of ethanol and below the outlet temperature of the reactor 10 by a cooling means installed between the outlet of the reactor 10 (i.e., the outlet of reactor 11 or the second reactor 12b) and the separation means 14. When the intermediate gas 22 is cooled, at least a portion of the impurities condense.

[0030] Cooling methods include, for example, cooling by a heat exchanger, or extending the piping between the outlet of the reactor 10 and the separation means 14 to ensure sufficient cooling time. In Figure 1, a heat exchanger 13a is shown as a cooling method.

[0031] Subsequently, the intermediate gas 22 is supplied to a separation means 14 equipped with a filter, and the condensed impurities from the intermediate gas 22 are separated into gas and liquid to obtain a mixed gas 23. In Figure 1, the impurities are indicated by the symbol BO. The gas and liquid separated impurities are removed from the system.

[0032] The separation means 14 is a separation means equipped with a filter, and examples include a method of gas-liquid separation using a coalescer or a cyclone filter, with a coalescer being preferred. In this embodiment, the separation means 14 is preferably a coalescer equipped with a filter 14A that coarses the liquid droplets to separate them from the gas phase.

[0033] Furthermore, the filter may be used in combination with the gravity separator 14B. The gravity separator 14B can remove millimeter-sized impurities that have formed as droplet particles. In one embodiment of the present invention, by first supplying the intermediate gas 22 supplied to the separation means 14 to the gravity separator 14B, coarse impurities can be removed in advance, thereby reducing the load on the filter 14A.

[0034] In one embodiment of the present invention, a two-stage separation process is preferred, comprising at least a first separation process and a second separation process performed at a lower temperature than the first separation process. As shown in Figure 4, the two-stage separation process supplies the intermediate gas 22 cooled to temperature T1 by a heat exchanger 13a to the first separation means 14a for gas-liquid separation. The two-stage separation process cools the mixed gas 23a separated by the first separation means 14a to a temperature T2, which is lower than T1, by a heat exchanger 13b and supplies it to the second separation means 14b. The mixed gas 23b separated by the second separation means 14b is preferably further cooled by a heat exchanger 13c for use in a distillation process.

[0035] By providing a multi-stage separation process that includes at least a first separation step and a second separation step, the efficiency of removing impurities is improved.

[0036] Furthermore, it is preferable to periodically clean the separation means 14 to avoid blockage by foreign matter. If the separation means 14 becomes blocked by foreign matter, continuous operation can be enabled by cleaning it with an organic solvent.

[0037] The type of organic solvent is not limited as long as the blockage can be improved by washing. In this embodiment, alcohol-based solvents, aldehyde-based solvents, ketone-based solvents, carboxylic acid-based solvents, ether-based solvents, olefin-based solvents, ester-based solvents, aromatic solvents, and nonpolar solvents can also be used as organic solvents for washing. More specifically, methanol, ethanol, acetaldehyde, acetone, acetic acid, diethyl ether, kerosene, hexene, acetate ester, toluene, hexane, etc. can be used as organic solvents for washing.

[0038] (3) Distillation process Ethanol is distilled from the mixed gas 23 obtained in the separation process. The reaction product after the ETB reaction contains 1,3-butadiene as well as unreacted ethanol, water, acetaldehyde, and other components. Organic substances such as ethanol contained in the reaction product can be separated and purified for use.

[0039] In one embodiment of the present invention, the mixed gas 23 obtained in the separation step is cooled by a heat exchanger 13c and supplied to a first distillation column 15. In the first distillation column 15, 1,3-butadiene is recovered from the mixed gas 23 and the ethanol-containing gas 24 is supplied to a second distillation column 16. The 1,3-butadiene (indicated as "BD" in Figure 1) extracted from the top of the first distillation column 15 is further purified in a subsequent distillation column (not shown).

[0040] Between the first distillation column 15 and the second distillation column 16, there may be an additional distillation column for distilling other useful components such as acetaldehyde.

[0041] In the second distillation column 16, ethanol is extracted from the top of the column and water is extracted from the bottom of the column. At this time, if the ethanol-containing gas 24 supplied to the second distillation column 16 contains impurities, these impurities will precipitate individually at the bottom of the second distillation column 16, causing blockage of the reaction tubes and piping.

[0042] In this embodiment, the intermediate gas 22 is physically removed by gas-liquid separation in the separation step (2) prior to the distillation step (3). As a result, the ethanol-containing gas 24 does not contain impurities, or if it does, the amount is small, so the precipitation of impurities as individual particles at the bottom of the second distillation column 16 is unlikely to be a problem. Therefore, a method for producing 1,3-butadiene can be provided that avoids blockage of reaction tubes and piping and enables stable continuous operation.

[0043] Figure 5 is an explanatory diagram illustrating a method for producing 1,3-butadiene according to a second embodiment. This method is a method for producing 1,3-butadiene from an ethanol-containing raw material, and in addition to the above steps (1) to (3), it comprises the following step (4).

[0044] (4) Ethanol recycling process in which ethanol obtained by a distillation process is used as part of an ethanol-containing raw material.

[0045] (4) Ethanol recycling process The ethanol-containing gas 24 recovered in the (3) distillation process is supplied to the reactor 10 as part of the ethanol-containing raw material. Since the ethanol-containing gas 24 does not contain impurities or contains a small amount of impurities, even if it is supplied again to reaction pipes and piping such as reactors and distillation towers by recycling, blockage can be avoided and stable continuous operation becomes possible.

[0046] The origin of the ethanol used in the ethanol-containing raw material is not particularly limited, and examples thereof include biomass-derived such as sugarcane, corn, and waste pulp, and petroleum, coal, or natural gas-derived. Examples of biomass-derived ethanol include ethanol produced by fermenting biomass. The use of biomass-derived ethanol can contribute to reducing greenhouse gas emissions. Examples of ethanol derived from waste such as petroleum products include ethanol produced from syngas by gasifying plastics and tires.

[0047] Hereinafter, the present invention will be described by way of examples, but the present invention is not limited to these examples. In this example, based on the configuration and process flow of the manufacturing apparatus shown in FIG. 5, process simulation was performed using software manufactured by Aspen Technology, Inc.

[0048] <Example 1> In Example 1, the separation step was simulated as a manufacturing apparatus and process flow shown in FIG. 5 for a process of continuously producing 1,3-butadiene. The process used Aspen Plus simulation software, which is commercially available from Aspen Technologies, Inc. In Example 1, the intermediate gas 22 at 330 °C was cooled to 160 °C by the heat exchanger 13a, supplied to the first separation means 14a, the mixed gas 23a separated by the first separation means 14a was cooled to 110 °C by the heat exchanger 13b, supplied to the second separation means 14b, the mixed gas 23b separated by the second separation means 14b was cooled to 40 °C by the heat exchanger 13c, and then subjected to a distillation process. Through this process simulation, it was confirmed that 1,3-butadiene could be continuously produced without blocking the reaction tubes and pipes.

[0049] When using a coalescer equipped with a filter as the separation means 14, if a filter with a high filtration accuracy is used, impurities can be removed more precisely.

[0050] <Comparative Example 1> A process simulation was performed with the same process flow as in Example 1, except that the separation step (2) was not carried out. As a result, it was confirmed that impurities precipitated as a single substance at the bottom of the second distillation column 16, blocking the reaction tubes and pipes.

[0051] <Reference Example> The impurities obtained by bench tests were added to a predetermined solvent, and it was confirmed whether the impurities dissolved in the solvent.

[0052] <<Test Example 1>> An ethanol-containing raw material was supplied to a reactor holding an arbitrary catalyst, and at least 1,3-butadiene, ethanol, and impurities, which are organic substances with a higher boiling point than ethanol, were obtained. For 1 part by mass of the obtained impurities, 100 parts by mass of ethanol (an alcohol-based solvent) was added, and the mixture was stirred with a vortex mixer under room temperature and normal pressure conditions. As a result, the impurities dissolved in ethanol.

[0053] <<Test Example 2>> When tested in the same manner as in Test Example 1, except that the solvent was changed to acetaldehyde, which is an aldehyde-based solvent, the impurities dissolved in acetaldehyde.

[0054] <<Test Example 3>> The test was conducted in the same manner as in Test Example 1, except that the solvent was changed to acetone, a ketone solvent. The impurities dissolved in the acetone.

[0055] <Test Example 4> The test was conducted in the same manner as in Test Example 1, except that the solvent was changed to acetic acid, a carboxylic acid-based solvent. The impurities dissolved in the acetic acid.

[0056] <Test Example 5> The test was conducted in the same manner as in Test Example 1, except that the solvent was changed to diethyl ether, an ether-based solvent. The impurities dissolved in the diethyl ether.

[0057] <<Test Example 6>> The test was conducted in the same manner as in Test Example 1, except that the solvent was changed to hexene, an olefin-based solvent. The impurities dissolved in the hexene.

[0058] <<Test Example 7>> The test was conducted in the same manner as in Test Example 1, except that the solvent was changed to ethyl acetate, an ester-based solvent. The impurities dissolved in the ethyl acetate.

[0059] <Test Example 8> The test was conducted in the same manner as in Test Example 1, except that the solvent was changed to toluene, an aromatic solvent. The impurities dissolved in toluene.

[0060] <Test Example 9> The test was conducted in the same manner as in Test Example 1, except that the solvent was changed to hexane, a nonpolar solvent. The impurities dissolved in the hexane.

[0061] From the results of the above test examples 1 to 9, it was confirmed that the contaminants were readily soluble in any of the organic solvents, including alcohol-based solvents, aldehyde-based solvents, ketone-based solvents, carboxylic acid-based solvents, ether-based solvents, olefin-based solvents, ester-based solvents, aromatic solvents, and nonpolar solvents. It was found that clogging due to contaminants could be avoided by periodically washing the separation means 14 with these organic solvents. Furthermore, it was found that if the separation means 14 became clogged with contaminants, continuous operation could be enabled by washing it with these organic solvents.

[0062] 10, 11: Reactors, 11c: Catalyst, 12a: First reactor, 12b: Second reactor, 12x: First catalyst, 12y: Second catalyst, 13a, 13b, 13c: Heat exchangers, 14: Separation means, 14a: First separation means, 14b: Second separation means, 15: First distillation column, 16: Second distillation column, 20: Ethanol-containing raw material, 22: Intermediate gas, 23: Mixed gas, 24: Ethanol-containing gas

Claims

1. A method for producing 1,3-butadiene from an ethanol-containing raw material, comprising: a conversion step of supplying the ethanol-containing raw material to a reactor holding a catalyst to obtain an intermediate gas containing at least 1,3-butadiene, ethanol, and impurities which are organic substances having a higher boiling point than ethanol; a separation step of cooling the intermediate gas to a temperature above the boiling point of ethanol and below the outlet temperature of the reactor to condense at least a portion of the impurities, then supplying the intermediate gas to a separation means equipped with a filter, and separating the condensed impurities from the intermediate gas by gas-liquid separation to obtain a mixed gas; and a distillation step of separating ethanol from the mixed gas, in this order.

2. The method for producing 1,3-butadiene according to claim 1, wherein the ethanol obtained by the distillation step is used as part of the ethanol-containing raw material.

3. The method for producing 1,3-butadiene according to claim 1 or 2, wherein the separation means is a coalescer.

4. The method for producing 1,3-butadiene according to claim 1 or 2, wherein the separation means further comprises a gravity separator.

5. The method for producing 1,3-butadiene according to claim 1 or 2, wherein the boiling point of the impurity is 80°C or higher and less than 600°C under atmospheric pressure.

6. The method for producing 1,3-butadiene according to claim 1 or 2, wherein the separation step comprises at least a first separation step and a second separation step carried out at a lower temperature than the first separation step, and the mixed gas obtained in the first separation step is supplied to the second separation step.

7. A method for producing 1,3-butadiene according to claim 3, comprising a washing step with an organic solvent.

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