Method for purifying separated ethanol product and method for producing 1,3-butadiene
Patent Information
- Application Number
- PCT/JP2025/006113
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Filing Date
- 2025-02-21
- Publication Date
- 2026-08-27
Smart Images
Figure JP2025006113_27082026_PF_FP_ABST
Abstract
Description
Method for purifying ethanol isolate and method for producing 1,3-butadiene
[0001] The present invention relates to a technique for separating ethanol from a distillation separatory obtained in the production of 1,3-butadiene.
[0002] 1,3-butadiene (hereinafter sometimes simply referred to as "butadiene"), which is used as a raw material for synthetic rubber, is primarily produced by naphtha cracking, a by-product of ethylene produced by the thermal decomposition of naphtha. Other known methods for producing butadiene include monoproduct processes such as the oxidative dehydrogenation process of butene and the dimerization process of ethanol or acetaldehyde.
[0003] In addition, various development efforts are underway to produce 1,3-butadiene using ethanol, which can be manufactured from biomass-derived raw materials through methods such as fermentation, as a mono-production process with a low environmental impact.
[0004] For example, Patent Document 1 describes a technique for converting ethanol to acetaldehyde in the presence of a catalyst, and then converting the resulting ethanol / acetaldehyde effluent to butadiene in the presence of a catalyst. Butadiene is extracted from the effluent obtained from the reaction. Ethanol and acetaldehyde are then recovered from the remaining fluid after extraction and recycled back into the reaction with the catalyst.
[0005] Patent Document 2 also describes a technique for producing butadiene by converting ethanol to acetaldehyde in a first reactor, separating the inorganic gas produced as a by-product in the first reactor, and then converting ethanol and acetaldehyde to butadiene in a second reactor. In Patent Document 2 as well, butadiene is purified from the fluid obtained by these reactions by distillation and extraction. Furthermore, acetaldehyde and ethanol are separated from the remaining liquid after butadiene has been separated by distillation and supplied to a mixer upstream of the second reactor.
[0006] Japanese Patent Publication No. 6594416, Japanese Unexamined Patent Publication No. 2023-31384
[0007] As described in Patent Documents 1 and 2, there is a known technique for separating butadiene from a reaction product obtained by reacting ethanol and acetaldehyde, and then recovering acetaldehyde and ethanol from the remaining fluid and supplying them to the reaction system. On the other hand, biomass-derived ethanol, for example, contains various impurities, and these impurities may accumulate in the system, hindering improvements in butadiene production efficiency or adversely affecting the equipment. However, Patent Documents 1 and 2 do not describe any technique for reducing the effects of such impurities.
[0008] This invention was made against this background and provides a technology for reducing impurities contained in ethanol recovered from the distillation separatory product after 1,3-butadiene has been separated by distillation, when the recovered ethanol is reused as an ethanol-containing raw material.
[0009] The present invention provides a method for purifying an ethanol isolate, wherein the ethanol isolate is obtained by distilling and separating a butadiene reaction product containing 1,3-butadiene from a 1,3-butadiene-containing product obtained by contacting an ethanol-containing raw material containing ethanol and acetaldehyde with a 1,3-butadiene production catalyst, and is a distillation isolate containing acetaldehyde, acetone, an azeotropic organic compound which is an organic compound in an azeotropic relationship with acetone, and ethanol, and further comprises a purification step of distilling and separating the azeotrope of acetone and the azeotropic organic compound from the ethanol isolate to separate the azeotrope and obtain an ethanol recovery product containing ethanol, wherein the ethanol recovery product is used as the ethanol-containing raw material.
[0010] The method for purifying the ethanol isolate may include the following: (a) The azeotropic organic compound is at least one of cyclohexane and methanol. (b) The purification step includes an ethanol recovery step of distilling the ethanol isolate to obtain a low-boiling-point isolate containing acetaldehyde and the azeotrope, and the ethanol recovery product; and an acetaldehyde recovery step of distilling the low-boiling-point isolate to obtain an acetaldehyde recovery product containing acetaldehyde, and a by-product containing the azeotrope, wherein the acetaldehyde recovery product is used as acetaldehyde to be contacted with the 1,3-butadiene production catalyst. (c) The purification step includes an acetaldehyde recovery step of distilling the ethanol separator to obtain an acetaldehyde recovery product containing acetaldehyde and a high-boiling point separator containing the azeotrope and ethanol, and an ethanol recovery step of distilling the high-boiling point separator to obtain a by-product containing the azeotrope and the ethanol recovery product, wherein the acetaldehyde recovery product is used as acetaldehyde to be contacted with the 1,3-butadiene production catalyst. (d) In (b) or (c), the ethanol recovery step is carried out using a rectification column, and the temperature at the top of the rectification column is adjusted to be below the boiling point of other azeotropes formed between ethanol and the azeotropic organic compound cyclohexane. The acetaldehyde recovery step is also carried out using a rectification column, and the temperature at the top of the purification column is adjusted to be above the boiling point of other azeotropes formed between acetaldehyde and diethyl ether, and below the boiling point of diethyl ether. (e) The amount of acetone in the ethanol separation product is equal to or greater than the required number of moles of acetone necessary for the acetone and the azeotropic organic compound to form an azeotrope, relative to the number of moles of the azeotropic organic compound contained in the ethanol separation product, and the purification step is carried out using a rectification column, and the entire amount of the azeotropic organic compound in the ethanol separation product is separated as an azeotrope by performing continuous distillation in the rectification column to converge the molar ratio of the acetone to the azeotropic organic compound to the molar ratio of the azeotrope.In this case, if the amount of acetone in the ethanol separated product is less than the required number of moles, the process further includes an acetone addition step, in which acetone is added to the ethanol separated product to adjust the number of moles of acetone in the ethanol separated product to be equal to or greater than the required number of moles. (f) The molar ratio of acetone to the azeotropic organic compound contained in the ethanol separated product (acetone / azeotropic organic compound) is within the range of 0.1 or more and 10 or less.
[0011] Furthermore, the present invention provides a method for producing 1,3-butadiene, comprising a reaction step of supplying the ethanol-containing raw material and acetaldehyde to a reactor containing a 1,3-butadiene production catalyst and contacting the 1,3-butadiene production catalyst to convert a portion of the ethanol and acetaldehyde into 1,3-butadiene, thereby obtaining a butadiene-containing product comprising acetaldehyde, acetone, the azeotropic organic compound, ethanol, and 1,3-butadiene, and an acetaldehyde recycling step of supplying the acetaldehyde recovery product described in (b) or (c) to the reactor.
[0012] The method for producing 1,3-butadiene may include the following: (g) The reaction step includes a first reaction step of supplying the ethanol-containing raw material to a first reactor containing an acetaldehyde production catalyst that produces acetaldehyde from ethanol, and contacting it with the acetaldehyde production catalyst to obtain a mixed raw material containing the ethanol-containing raw material and acetaldehyde; and a second reaction step of supplying the mixed raw material to a second reactor, which is the reactor containing the 1,3-butadiene production catalyst, to obtain the butadiene-containing product, wherein the acetaldehyde recycling step is to supply the recovered acetaldehyde to the second reactor. (h) The method in (g) includes an ethanol recycling step of supplying the recovered ethanol as the ethanol-containing raw material to the first reactor.
[0013] (i)(h) includes an ethanol bypass supply step in which a portion of the ethanol recovered material before it is supplied to the first reactor in the ethanol recycling step is supplied to the inlet side of the second reactor, and the acetaldehyde recovered material supplied in the acetaldehyde recycling step and the ethanol recovered material supplied in the ethanol bypass step are supplied via a connecting pipe connecting the outlet side of the first reactor and the inlet side of the second reactor, and the downstream side of the supply position of one side of the recycled recovered material, which is the acetaldehyde recovered material or the ethanol recovered material supplied to the connecting pipe, The method includes: an analysis step of analyzing the ethanol and acetaldehyde content of the mixed fluid of the mixed raw material and one side of the recycled material, which flows upstream of the supply position of the other side of the recycled material, and the other side of the recycled material; and a flow rate adjustment step of adjusting the supply flow rate of at least one side of the recycled material so that, based on the results of the analysis step, the molar ratio (ethanol / acetaldehyde) of the two components, ethanol and acetaldehyde, in the mixed fluid of the mixed raw material and both sides of the recycled material supplied to the second reactor falls within a predetermined range.(j)(h) includes an ethanol bypass supply step in which a portion of the ethanol recovered before being supplied to the first reactor in the ethanol recycling step is supplied to the inlet side of the second reactor, and the acetaldehyde recovered supplied in the acetaldehyde recycling step and the ethanol recovered supplied in the ethanol bypass step are supplied via a connecting pipe connecting the outlet side of the first reactor and the inlet side of the second reactor, the mixed raw materials flowing upstream of either the supply position of the acetaldehyde recovered or the ethanol recovered supplied to the connecting pipe, the acetaldehyde supplied in the acetaldehyde recycling step (k) The process includes an analysis step of analyzing the ethanol and acetaldehyde content of the recovered material and the ethanol recovered material supplied in the ethanol bypass step, and a flow rate adjustment step of adjusting the supply flow rate of at least one of the acetaldehyde recovered material supplied in the acetaldehyde recycling step and the ethanol recovered material supplied in the ethanol bypass step, so that the molar ratio (ethanol / acetaldehyde) of ethanol and acetaldehyde in the mixed fluid of the mixed raw material, the acetaldehyde recovered material, and the ethanol recovered material supplied to the second reactor is within a predetermined range. (k) The process includes an ethanol separation step of distilling and separating the butadiene reaction product from the 1,3-butadiene-containing material obtained in the reaction step to obtain the ethanol separation product.
[0014] According to the present invention, ethanol recovery is obtained by distilling acetone and azeotropic organic compounds (organic compounds in an azeotropic relationship with acetone) from the ethanol separation product, which is the distillation separation product after 1,3-butadiene has been separated by distillation. Therefore, by reusing the ethanol recovery as an ethanol-containing raw material, the accumulation of impurities in the system can be suppressed. As a result, the impact on the reaction and equipment for producing 1,3-butadiene from ethanol can be reduced.
[0015] This is a configuration diagram showing an example of a butadiene production plant according to an embodiment. This is a configuration diagram showing a first embodiment of a recovery section provided in the butadiene production plant. This is a configuration diagram showing a second embodiment of the recovery section. This is a configuration diagram showing an example of the arrangement of an analyzer to the second reactor to which recycled ethanol is supplied. This is a configuration diagram showing another example of the arrangement of the analyzer.
[0016] First, with reference to Figure 1, an example configuration of a butadiene production plant 1 that produces 1,3-butadiene (butadiene) from ethanol will be described. The butadiene production plant 1 includes an ethanol evaporation tower 2 for pre-treating the raw material ethanol, reactors (first reactor 31, second reactors 32A, 32B) that produce butadiene from ethanol by catalytic reaction, and an ethanol separation tower 4 that separates butadiene from unreacted ethanol by distillation. In Figure 1, the flow of the fluid containing ethanol supplied as a raw material and the butadiene produced from this ethanol is shown by thick lines.
[0017] The ethanol evaporation tower 2 evaporates ethanol from an ethanol-containing raw material supplied from an external source, separating it from water. An example of an ethanol-containing raw material supplied to the ethanol evaporation tower 2 in this example is one containing biomass-derived ethanol produced by fermentation. Because this type of ethanol-containing raw material contains a large amount of water, a pretreatment is performed using the ethanol evaporation tower 2 to separate the ethanol from the water.
[0018] Furthermore, the ethanol evaporation tower 2 is supplied with the ethanol recovery material recovered in the recovery section 6, which will be described later. In other words, the butadiene production plant 1 also utilizes the ethanol recovery material as an ethanol-containing raw material. The ethanol recovery material contains unreacted ethanol that has passed through the reactor and water that is produced as a by-product during the butadiene production reaction. Therefore, in order to use the ethanol recovery material as an ethanol-containing raw material, it is supplied to the ethanol evaporation tower 2 for water separation. At this time, other heavy by-products contained in the ethanol recovery material are also separated.
[0019] Ethanol-containing raw material (including ethanol recovered product) from which water has been separated in the ethanol evaporation column 2 is supplied to the reactor (ethanol recycling step). The butadiene production plant 1 shown in FIG. 1 employs a two-stage method including a first reactor 31 that converts a part of ethanol into acetaldehyde and a second reactor 32 that synthesizes butadiene by reacting ethanol and acetaldehyde.
[0020] For example, the first reactor 31 is configured as a reactor containing an acetaldehyde production catalyst that generates acetaldehyde from ethanol. The acetaldehyde production catalyst causes the reaction of the following formula (1) to proceed for a part of the supplied ethanol to generate acetaldehyde. CH ３ CH ２ OH → CH ３ CHO + H ２ …(1)
[0021] The acetaldehyde production catalyst used in the first reactor 31 is not particularly limited as long as it has the activity to cause the reaction of formula (1) to proceed. Specific configuration examples of the acetaldehyde production catalyst can include a mixture of chromium oxide - copper oxide and a mixture of copper oxide and silicon oxide. In the first reactor 31, for example, the ethanol-containing raw material is brought into contact with the acetaldehyde production catalyst under reaction conditions within a range of pressure of 0.2 to 1.5 MPaG and temperature of 150 to 350 °C to obtain a mixed raw material containing the ethanol-containing raw material and acetaldehyde (first reaction step). The mixed raw material obtained in the first reactor 31 is supplied to the second reactor 32.
[0022] For example, the second reactor 32 is configured as a reactor containing a 1,3-butadiene production catalyst (hereinafter may be simply referred to as "butadiene production catalyst") that reacts a part of ethanol and acetaldehyde contained in the mixed fluid to generate butadiene. The butadiene production catalyst causes the reaction of the following formula (2) to proceed for ethanol and acetaldehyde to generate butadiene. CH ３ CH ２ OH + CH ３ CHO → CH ２ =CH-CH=CH ２+2H ２ O ... (2)
[0023] The butadiene production catalyst used in the second reactor 32 is not particularly limited as long as it has the activity to carry out the reaction of equation (2). Specific examples of the butadiene production catalyst include catalysts in which metal oxides such as tantalum pentoxide, zirconium dioxide, or hafnium oxide are supported on a silicon oxide support. In the second reactor 32, for example, a mixed raw material (ethanol-containing raw material and acetaldehyde) is brought into contact with the butadiene production catalyst under reaction conditions within the range of a pressure of 0.1 to 1.0 MPaG and a temperature of 250 to 400°C to obtain a butadiene-containing product (second reaction step). The butadiene-containing product obtained in the second reactor 32 is supplied to the ethanol separation column 4.
[0024] The first and second reaction steps described above, as a whole, correspond to a reaction process in which an ethanol-containing raw material and acetaldehyde are brought into contact with a butadiene production catalyst, and a portion of the ethanol and acetaldehyde are converted to 1,3-butadiene, thereby obtaining a butadiene-containing product that includes butadiene.
[0025] In the example shown in Figure 1, multiple (for example, two) second reactors 32 (32A, 32B) are provided. This is because, when the butadiene production catalyst is used, deposits such as carbon accumulate on the catalyst surface, reducing its catalytic activity. In this case, a regeneration operation is performed to remove the deposits by supplying regeneration gas. In these second reactors 32A and 32B, the process of obtaining a butadiene-containing product from the mixed raw materials and the regeneration process of the butadiene production catalyst are repeated alternately.
[0026] Furthermore, as shown in Figure 1 and in Figures 4 and 5 described later, acetaldehyde recovered in the recovery section 6 described later may be supplied to the connecting pipe on the inlet side of the second reactor 32 to which the mixed raw materials are supplied from the first reactor 31 (acetaldehyde recycling process). Furthermore, a portion of the ethanol recovered before it is supplied to the first reactor 31 (after water is separated in the ethanol evaporation tower 2) may be supplied to the connecting pipe on the inlet side of the second reactor 32 (ethanol bypass supply process). Note that in the example shown in Figure 1, only the configuration for supplying acetaldehyde recovered is described.
[0027] By supplying at least one of the recovered acetaldehyde and recovered ethanol to the mixed raw materials, the supply ratio (e.g., based on the molar ratio) of ethanol to acetaldehyde supplied to the second reactor 32 can be adjusted to an optimal value for the progress of the reaction of equation (2) by the butadiene production catalyst. Specific examples of methods for adjusting the supply ratio of ethanol to acetaldehyde will be explained later with reference to Figures 4 and 5.
[0028] Furthermore, it is not a mandatory requirement to use a two-step process in the second reactor 32. A one-step process, in which butadiene is synthesized directly from two molecules of ethanol, may also be employed. In this case, for example, the reactor contains a butadiene production catalyst that directly produces butadiene from ethanol. The butadiene production catalyst proceeds with the reaction of equation (3) below on a portion of the supplied ethanol to produce butadiene. 2CH ３ CH ２ OH→CH ２ =CH - CH = CH ２ +2H ２ O+H ２ …(3) The butadiene production catalyst used in the reactor is not particularly limited as long as it has the activity to carry out the reaction of equation (3). The pressure and reaction temperature in the reactor are set according to the activity of the butadiene production catalyst.
[0029] The ethanol separation column 4 is a distillation column for performing a process (ethanol separation step) in which the butadiene reaction product, including the butadiene produced by the reaction, is separated by distillation from the butadiene-containing material to obtain the ethanol separator, which is a distillation separator containing unreacted ethanol and acetaldehyde. The butadiene reaction product flows out as a gas from the top of the ethanol separation column 4. On the other hand, the ethanol separator flows out as a liquid from the bottom of the ethanol separation column 4.
[0030] A brief explanation is given regarding the treatment of the butadiene reaction product that flows out from the top of the ethanol separation column 4. The butadiene reaction product separated from the ethanol separation product in the ethanol separation column 4 is absorbed in the absorption column 51 by alternating contact with ethanol supplied from an external source, thereby absorbing the heavy components, including butadiene. The light gas that is not absorbed by the ethanol is discharged from the top of the absorption column 51.
[0031] The ethanol that has absorbed the heavy components in the absorption column 51 is heated in the decontamination column 52 to release any remaining light gases, and then sent to the butadiene separation column 53, which is a distillation column. In the butadiene separation column 53, the ethanol that has absorbed the heavy components is separated into butadiene and ethanol. The separated ethanol is combined with the ethanol separation product that has flowed out from the bottom of the ethanol separation column 4 and processed in the recovery section 6 described later.
[0032] The butadiene separated in the butadiene separation tower 53 is brought into contact with water in the washing tower 54 to remove water-soluble by-products, and then the water is adsorbed and removed in the dryer 55. The butadiene from which the water has been removed is stored in a tank, for example, and then shipped as a product.
[0033] Next, the treatment of the ethanol separation product flowing out from the bottom of the ethanol separation column 4 will be described. In the butadiene production plant 1 of the present embodiment, as described above, the ethanol separation product merges with the ethanol separated from butadiene in the butadiene separation column 53 in the top system (hereinafter, the fluid after merging is also referred to as "ethanol separation product"). Thereafter, the ethanol separation product is treated in the recovery section 6. The recovery section 6 performs a distillation operation to separate the ethanol and acetaldehyde contained in the ethanol separation product into ethanol recovery product and acetaldehyde recovery product in order to use them for the production of butadiene respectively.
[0034] FIG. 2 shows an enlarged view of the recovery section 6 (6A) illustrated in FIG. 1. FIG. 3 shows another configuration example of the recovery section 6 (6B). These recovery sections 6A and 6B have a function of removing predetermined impurities in addition to the function of separating the ethanol recovery product and the acetaldehyde recovery product.
[0035] Here, the biomass-derived ethanol supplied as an ethanol-containing raw material to the butadiene production plant 1 contains various impurities. The inventors have recognized that some of these impurities may prevent the improvement of the production efficiency of butadiene or may have an adverse effect on the equipment. For example, cyclohexane is a cyclic hydrocarbon composed of single bonds and has low reactivity in this process, so it is less likely to be converted in the first reactor 31 and the second reactor 32, and there is a risk of accumulation in the system by being accompanied by the recycled ethanol.
[0036] On the other hand, cyclohexane has a boiling point of 80.7 ° C (standard boiling point; the same applies hereinafter unless otherwise specified), which is close to the boiling point of ethanol of 78.3 ° C, and it is difficult to separate and remove it as a by-product in the ethanol evaporation column 2. Therefore, if only distillation separation is performed in one distillation column for the ethanol recovery product and the acetaldehyde recovery product, cyclohexane will be contained in one of the recovery products.
[0037] If the supply of cyclohexane and acetone from the outside continues with the supply of the ethanol-containing raw material, cyclohexane will accumulate in the butadiene production plant 1. As described above, cyclohexane has low reactivity and has little possibility of being converted in the first reactor 31 and the second reactor 32. Therefore, when the concentration of cyclohexane in the ethanol recovery product or the acetaldehyde recovery product increases, it affects the reactivity due to the fluctuation of the partial pressures of ethanol and acetaldehyde suitable for the reaction. As a result, there is a possibility that it may cause a factor for reducing the production efficiency of butadiene in the butadiene production plant 1.
[0038] As another example of impurities, methanol has a boiling point of 64.7°C, which is lower than that of ethanol, and it is difficult to separate and remove it as a by-product in the ethanol evaporation column 2. Therefore, similar to the case of cyclohexane, if only distillation separation is performed in one distillation column for methanol, methanol will be contained in either the ethanol recovery product or the acetaldehyde recovery product.
[0039] Here, it is understood that methanol may be converted into formic acid in the first reactor 31 or the second reactor 32. Formic acid is a corrosive substance. If the supply of methanol and acetone from the outside continues with the supply of the ethanol-containing raw material, there is a risk of exposing the metal members constituting the butadiene production plant 1 to a highly corrosive environment.
[0040] To avoid these situations, a measure can be considered to suppress the accumulation of cyclohexane in the butadiene production plant 1 by performing an operation of discharging the ethanol recovery product or the acetaldehyde recovery product containing cyclohexane and methanol to the outside. However, this method will discharge ethanol and acetaldehyde, which are butadiene raw materials, to the outside, so there is a possibility that it may cause a factor for reducing the production efficiency of butadiene.
[0041] Of the substances mentioned above that may accumulate in the butadiene production plant 1, cyclohexane forms an azeotrope with acetone, another impurity contained in the ethanol-containing raw material. The azeotropic point of this cyclohexane-acetone azeotrope is 53.4°C (at atmospheric pressure; the same applies hereafter unless otherwise specified), which is lower than the boiling point of ethanol and higher than the boiling point of acetaldehyde (boiling point 20.2°C). Methanol also forms an azeotrope with acetone. The azeotropic point of this methanol-acetone azeotrope is 54.9°C, which is lower than the boiling point of ethanol and higher than the boiling point of acetaldehyde. Therefore, the recovery section 6 (6A, 6B) of this embodiment utilizes the fact that methanol and cyclohexane form azeotropes with acetone to distill and separate the azeotrope from the ethanol separatory product flowing out of the ethanol separation column 4 and discharge it to the outside (purification process). As a result, it is possible to obtain ethanol recovery product from which the cyclohexane-acetone azeotrope and methanol-acetone azeotrope have been separated.
[0042] In this embodiment, organic compounds that are in an azeotropic relationship with acetone, such as cyclohexane and methanol as described above, are also called "azeotropic organic compounds." It is preferable that the boiling point of the azeotrope with acetone is lower than that of ethanol and higher than that of acetaldehyde. Azeotropic organic compounds are not limited to cyclohexane and methanol. Other organic compounds may also be used, as long as they are impurities contained in the ethanol-containing raw material, are in an azeotropic relationship with acetone by distillation separation from the ethanol separation product, and the azeotrope can be separated by distillation from the recovered ethanol product or recovered acetaldehyde product. First, the configuration and operation of the recovery section 6A according to the first embodiment will be described with reference to Figure 2.
[0043] As shown in Figure 2, the recovery section 6A according to the first embodiment comprises an ethanol recovery column 61 and an impurity separation column 62. The ethanol recovery column 61 distills and separates the ethanol separator supplied from the ethanol separation column 4 into a low-boiling-point separator and an ethanol recovery product (ethanol recovery step). The ethanol separator contains at least acetaldehyde, acetone, cyclohexane, methanol, ethanol, and water (contained components). For acetone and azeotropic organic compounds (cyclohexane and methanol in this example) contained in the ethanol separator, it is preferable that the molar ratio (acetone / azeotropic organic compound) is in the range of 0.1 or more and 10 or less. Furthermore, from the viewpoint of reducing the loss of acetaldehyde and ethanol, distillation of the ethanol separator is also performed with attention to diethyl ether (boiling point 34.5°C) and ethyl acetate, which form azeotropes with acetaldehyde and ethanol (focused components).
[0044] Figure 2 shows the above-mentioned components and components of interest contained in the ethanol separation product supplied to the ethanol recovery tower 61, along with other azeotropes formed with acetaldehyde and ethanol. These other azeotropes are acetaldehyde-diethyl ether azeotrope (azeotropic point: 19°C), ethanol-cyclohexane azeotrope (azeotropic point: 64.8°C), and ethanol-ethyl acetate azeotrope (azeotropic point: 71.8°C). In the listed entries, the acetaldehyde-diethyl ether azeotrope at the top has the lowest boiling point or azeotropic point, and the boiling points or azeotropic points increase as you move down the list. The boiling point of water at the bottom is the highest (100°C).
[0045] The ethanol recovery column 61 is configured as a rectification column and includes a reboiler 612 that heats a portion of the bottom liquid obtained from the bottom of the column and returns it to the column, and a cooler 611 that cools a portion of the top gas obtained from the top of the column and returns it to the column. The temperature distribution in the vertical direction within the ethanol recovery column 61 is adjusted by adjusting the supply flow rate and supply temperature of the ethanol separation product to the ethanol recovery column 61, the heating temperature and return flow rate of the bottom liquid in the reboiler 612, and the cooling temperature and return flow rate of the top gas in the cooler 611.
[0046] The ethanol recovery column 61, having the configuration described above, performs distillation of the ethanol separatory so that the low-boiling point separatory that flows out as the top gas contains cyclohexane-acetone azeotrope and methanol-acetone azeotrope. In this regard, the top temperature of the ethanol recovery column 61 is adjusted to be above the azeotrope point of cyclohexane-acetone azeotrope under the operating pressure conditions within the ethanol recovery column 61. For example, in the pressure range of atmospheric pressure (0 MPaG) to 0.5 MPaG, the azeotrope point of cyclohexane-acetone azeotrope is 53.4°C to 130°C. Furthermore, the top temperature of the ethanol recovery column 61 is adjusted to be above the azeotrope point of methanol-acetone azeotrope under its operating pressure conditions. For example, in the pressure range of atmospheric pressure (0 MPaG) to 0.5 MPaG, the azeotrope point of cyclohexane-acetone azeotrope is 54.9°C to 113.2°C.
[0047] On the other hand, since the ethanol recovered from the bottom of the ethanol recovery column 61 mainly contains ethanol, the top temperature of the ethanol recovery column 61 is adjusted to a temperature lower than the boiling point of ethanol under operating pressure. Furthermore, as can be seen from the order in which the components listed together with the ethanol separated product in Figure 2, there are other azeotropes, such as the ethanol-cyclohexane azeotrope and the ethanol-ethyl acetate azeotrope, between the azeotrope of the methanol-acetone azeotrope and the boiling point of ethanol. Therefore, if the top temperature of the ethanol recovery column 61 under operating pressure becomes higher than the azeotropes of these other azeotropes, the ethanol that constitutes these other azeotropes will be discharged to the outside as a by-product in the subsequent impurity separation column 62. In this case as well, there is a risk that the production efficiency of butadiene will decrease from the perspective of raw material loss.
[0048] Therefore, in the recovery section 6A of this embodiment, the top temperature of the ethanol recovery column 61 is adjusted so that, under operating pressure, it is below the azeotropic point of the other azeotropes mentioned above. Specifically, the top temperature of the ethanol recovery column 61 should be adjusted so that it is below the azeotropic point of the lighter ethanol-cyclohexane azeotrope. In the pressure range of atmospheric pressure (0 MPaG) to 0.5 MPaG, the azeotropic point of the ethanol-cyclohexane azeotrope is 64.8°C to 120°C.
[0049] In this case, the recovered ethanol will contain cyclohexane that forms an azeotrope with ethanol. Regarding this point, when cyclohexane, acetone, and ethanol coexist in the ethanol separation product, the cyclohexane-acetone azeotrope is preferentially formed. As previously mentioned, the molar ratio (acetone / azeotropic organic compound) of azeotropic organic compounds containing acetone, cyclohexane, and methanol is controlled to be between 0.1 and 10.
[0050] The molar ratio of acetone to azeotropic organic compounds in azeotropes changes depending on the pressure conditions, and the way in which the molar ratio changes with pressure changes differs between cyclohexane-acetone azeotropes and methanol-acetone azeotropes. For this reason, it is preferable to understand the molar ratio of acetone to each azeotropic organic compound that constitutes the azeotrope under operating pressure conditions and then manage the molar ratio. For example, if there is an excess of acetone compared to the number of moles required for each azeotropic organic compound to form an azeotrope, most cyclohexane and methanol can be converted into cyclohexane-acetone azeotropes and methanol-acetone azeotropes. Since the cyclohexane-acetone azeotropes and methanol-acetone azeotropes can be continuously discharged to the outside in this recovery section 6A, the accumulation of cyclohexane and methanol in the butadiene production plant 1 can be suppressed. However, it is not a necessary requirement that acetone always be in excess. Even if acetone is insufficient in the molar ratio required to form an azeotrope with an azeotropic organic compound, the rate at which cyclohexane and methanol accumulate in the butadiene production plant 1 can be reduced by controlling the molar ratio to, for example, 0.1 or higher, preferably 0.5 or higher, and more preferably 1 or higher.
[0051] In the ethanol recovery column 61, where the top temperature is controlled as described above, evaporation and condensation of acetone and the azeotropic organic compounds cyclohexane and methanol are repeated in each distillation stage within the rectification column. As the vapor rises (as the vapor temperature approaches the top temperature), the relative abundance (molar ratio) of cyclohexane-acetone and methanol-acetone in vapor-liquid equilibrium converges to the molar ratio of the azeotropes. However, it is possible that the amount of acetone in the ethanol separation product is less than the amount corresponding to the above-mentioned molar ratio relative to the number of moles of azeotropic organic compounds (cyclohexane and methanol) also contained in the ethanol separation product. In this case, the excess cyclohexane will be included in the ethanol recovery product, for example, as an ethanol-cyclohexane azeotrope, and the excess methanol will be included as a single molecule.
[0052] Therefore, in the recovery section 6A of this embodiment, the acetone content in the ethanol separation product may be controlled to be equal to or greater than the required number of moles of acetone necessary to form the cyclohexane-acetone azeotrope and methanol-acetone azeotrope, relative to the number of moles of azeotropic organic compounds (cyclohexane and methanol) also contained in the ethanol separation product. In this case, all of the cyclohexane and methanol in the ethanol recovery column 61 form azeotropes with acetone and are separated from the ethanol recovery product.
[0053] Here, an example of a method for controlling the acetone content in the ethanol separation product to be equal to or greater than the required number of moles mentioned above is to perform a compositional analysis of the ethanol separation product periodically, such as once a day. If the acetone content in the ethanol separation product is less than the required number of moles, additional acetone is supplied to the ethanol separation product to adjust the number of moles of acetone in the ethanol separation product to equal or greater than the required number of moles (additional step). The additional supply of acetone to the ethanol separation product is carried out, for example, by providing an additional acetone supply line (not shown) that joins the supply line of the ethanol separation product to the ethanol recovery tower 61, and supplying it through this additional supply line.
[0054] In the ethanol recovery column 61 having the configuration described above, ethanol recovery material containing ethanol and water flows out from the bottom of the column. As shown in Figure 2, the ethanol recovery material may contain ethanol-cyclohexane azeotropes or ethanol-ethyl acetate azeotropes. The presence of ethanol-cyclohexane azeotropes occurs, for example, when the acetone content in the ethanol separation is less than the required number of moles described above. On the other hand, due to distillation separation in the ethanol recovery column 61, the ethanol recovery material contains almost no cyclohexane-acetone azeotropes or methanol-acetone azeotropes. This ethanol recovery material is supplied to the ethanol evaporation column 2 as an ethanol-containing raw material (Figure 1).
[0055] On the other hand, low-boiling-point separatory material containing acetaldehyde and cyclohexane-acetone azeotropes, and methanol-acetone azeotropes flows out from the top of the ethanol recovery column 61. As shown in Figure 2, the low-boiling-point separatory material may contain acetaldehyde-diethyl ether azeotropes. However, due to distillation separation in the ethanol recovery column 61, the low-boiling-point separatory material contains almost no ethanol. This low-boiling-point separatory material is supplied to the impurity separation column 62.
[0056] Next, the configuration and operation of the impurity separation column 62 will be explained. The impurity separation column 62 distills the low-boiling point separatory supplied from the ethanol recovery column 61 into acetaldehyde recovery and by-products including cyclohexane-acetone azeotrope and methanol-acetone azeotrope (acetaldehyde recovery step).
[0057] The impurity separation column 62 is configured as a rectification column and includes a reboiler 622 that heats a portion of the bottom liquid obtained from the bottom of the column and returns it to the column, and a cooler 621 that cools a portion of the top gas obtained from the top of the column and returns it to the column. The temperature distribution within the impurity separation column 62 is also controlled by operating variables such as the supply flow rate and supply temperature of the low-boiling point separatory to the impurity separation column 62, and the temperature and return flow rate of the bottom liquid and top gas in the reboiler 632 and cooler 631.
[0058] The impurity separation column 62, having the configuration described above, performs distillation of low-boiling point separators such that acetaldehyde is included in the acetaldehyde recovered product that flows out as the top gas of the column. In this respect, the top temperature of the impurity separation column 62 is adjusted to be above the boiling point of acetaldehyde under the operating pressure conditions inside the impurity separation column 62.
[0059] On the other hand, the by-products flowing out from the bottom of the impurity separation column 62 must include cyclohexane-acetone azeotropes and methanol-acetone azeotropes to be discharged to the outside. Therefore, under the operating pressure of the impurity separation column 62, the top temperature of the column is adjusted to a temperature lower than the azeotropic point of cyclohexane-acetone azeotropes (53.4°C to 130°C in the pressure range of 0 to 0.5 MPaG) and the azeotropic point of methanol-acetone azeotropes (54.9°C to 113.2°C in the same pressure range).
[0060] The boiling point of acetaldehyde is approximately the same as that of the acetaldehyde-diethyl ether azeotrope. Therefore, when the entire amount of acetaldehyde is recovered, the azeotropic diethyl ether is also contained in the recycled acetaldehyde gas.
[0061] In the pressure range of atmospheric pressure (0 MPaG) to 0.5 MPaG, the azeotrope of the acetaldehyde-diethyl ether azeotrope is 19°C to 76°C. However, elemental diethyl ether (boiling point 34.5°C) does not contribute to the production of butadiene, so it is preferable to discharge it as a by-product. In this regard, the top temperature of the impurity separation column 62 is adjusted to be below the boiling point of diethyl ether under operating pressure.
[0062] In the impurity separation column 62 having the configuration described above, by-products containing cyclohexane-acetone azeotrope and methanol-acetone azeotrope flow out from the bottom of the column. On the other hand, acetaldehyde recovery containing acetaldehyde flows out from the top of the impurity separation column 62. As shown in Figure 2, the acetaldehyde recovery may contain acetaldehyde-diethyl ether azeotrope. However, due to distillation separation in the impurity separation column 62, the acetaldehyde recovery contains almost no cyclohexane-acetone azeotrope or methanol-acetone azeotrope. This acetaldehyde recovery is supplied to the second reactor 32 (Figure 1).
[0063] According to the recovery section 6A of the first embodiment described with reference to Figure 2, cyclohexane-acetone azeotrope and methanol-acetone azeotrope are separated by distillation from the ethanol separator, which is the distillation separator after butadiene has been separated by distillation, to obtain ethanol recovery. Then, the ethanol recovery, which contains almost no cyclohexane-acetone azeotrope or methanol-acetone azeotrope, is reused as an ethanol-containing raw material. Therefore, by reusing the ethanol recovery, it is possible to suppress the accumulation of cyclohexane, an impurity that does not contribute to the production of butadiene, and methanol, which may generate formic acid, a corrosive substance, in the butadiene production plant 1. As a result, it is possible to suppress the accumulation of cyclohexane that inhibits the reaction to produce butadiene from ethanol, and the adverse effects of formic acid generated from methanol on the equipment of the butadiene production plant 1.
[0064] Next, the configuration and operation of the recovery section 6B according to the second embodiment will be described with reference to Figure 3. In the recovery section 6B, components common to the recovery section 6A according to the first embodiment described using Figure 2 are denoted by the same reference numerals as those used in Figure 2.
[0065] As shown in Figure 2, the recovery section 6B according to the second embodiment includes an ethanol recovery column 61 and an impurity separation column 63. The ethanol recovery column 61 is configured as a rectification column, similar to the case of recovery section 6A described using Figure 2. On the other hand, the ethanol recovery column 61 distills and separates the ethanol separator supplied from the ethanol separation column 4 into acetaldehyde recovery and high-boiling point separators containing cyclohexane-acetone azeotrope, methanol-acetone azeotrope, and ethanol (acetaldehyde recovery step).
[0066] In the second embodiment, the ethanol recovery column 61 performs distillation of the ethanol separatory so that the high-boiling-point separatory that flows out as the bottom liquid contains cyclohexane-acetone azeotrope and methanol-acetone azeotrope. In this regard, the top temperature of the ethanol recovery column 61 is adjusted so that, under the operating pressure conditions within the ethanol recovery column 61, it is below the azeotrope point of cyclohexane-acetone azeotrope (53.4°C to 130°C in the pressure range of 0 to 0.5 MPaG) and below the azeotrope point of methanol-acetone azeotrope (54.9°C to 113.2°C in the same pressure range).
[0067] On the other hand, since the acetaldehyde recovered from the top of the ethanol recovery column 61 mainly contains acetaldehyde, the top temperature of the ethanol recovery column 61 is adjusted to a temperature higher than the boiling point of acetaldehyde under operating pressure. Furthermore, the ethanol separation product may contain the acetaldehyde-diethyl ether azeotrope described above. Therefore, under operating pressure, the top temperature of the ethanol recovery column 61 is adjusted to be above the azeotrope point of the acetaldehyde-diethyl ether azeotrope (19°C to 76°C in a pressure range of 0 to 0.5 MPaG). However, similar to the case of the impurity separation column 62 in the recovery section 6A of the first embodiment, it is preferable that elemental diethyl ether (boiling point 34.5°C), which does not contribute to the production of butadiene, is discharged as a by-product in the subsequent impurity separation column 63. From this viewpoint, the top temperature of the ethanol recovery column 61 is adjusted to be below the boiling point of diethyl ether under operating pressure.
[0068] In the ethanol recovery column 61 of the recovery section 6B, where the above-mentioned operational adjustments are performed, acetaldehyde-containing acetaldehyde-recovered material flows out from the top of the column. As previously described, the acetaldehyde-recovered material may contain acetaldehyde-diethyl ether azeotropes. On the other hand, due to distillation separation in the ethanol recovery column 61, the acetaldehyde-recovered material contains almost no cyclohexane-acetone azeotropes or methanol-acetone azeotropes. This acetaldehyde-recovered material is supplied to the second reactor 32 (Figure 1).
[0069] Furthermore, high-boiling-point separatory products containing cyclohexane-acetone azeotrope, methanol-acetone azeotrope, ethanol, and water flow out from the bottom of the ethanol recovery column 61. As shown in Figure 3, the high-boiling-point separatory products may contain ethanol-cyclohexane azeotrope, methanol-acetone azeotrope, and ethanol-ethyl acetate azeotrope. On the other hand, due to the distillation separation in the ethanol recovery column 61, the high-boiling-point separatory products contain almost no acetaldehyde. These high-boiling-point separatory products are supplied to the impurity separation column 63.
[0070] The impurity separation column 63 distills and separates the high-boiling point separator supplied from the ethanol recovery column 61 into by-products including cyclohexane-acetone azeotrope and methanol-acetone azeotrope, and ethanol recovery (ethanol recovery step). The impurity separation column 63 is configured as a rectification column and includes a reboiler 632 that heats a portion of the bottom liquid obtained from the bottom of the column and returns it to the column, and a cooler 631 that cools a portion of the top gas obtained from the top of the column and returns it to the column. The temperature distribution within the impurity separation column 63 is also controlled by operating variables such as the supply flow rate and supply temperature of the high-boiling point separator to the impurity separation column 63, and the temperatures and return flow rates of the bottom liquid and top gas in the reboiler 622 and cooler 621.
[0071] The impurity separation column 63, having the configuration described above, performs distillation of high-boiling-point separators so that ethanol is included in the ethanol recovered product that flows out as the bottom liquid. In this regard, the top temperature of the impurity separation column 63 is adjusted to be below the boiling point of ethanol under the operating pressure conditions within the impurity separation column 63.
[0072] On the other hand, the by-products flowing out from the top of the impurity separation column 63 must include cyclohexane-acetone azeotropes to be discharged to the outside. Therefore, under the operating pressure of the impurity separation column 63, the top temperature of the column is adjusted to be above the azeotropic point of cyclohexane-acetone azeotropes (53.4°C to 130°C in the pressure range of 0 to 0.5 MPaG) and above the azeotropic point of methanol-acetone azeotropes (54.9°C to 113.2°C in the same pressure range).
[0073] However, as can be seen from the order in which the components are listed alongside the high-boiling-point separated product in Figure 3, the azeotropic points of other azeotropes, such as ethanol-cyclohexane azeotrope and ethanol-ethyl acetate azeotrope, lie between the azeotropic point of cyclohexane-acetone azeotrope and the boiling point of ethanol. Therefore, if the top temperature of the impurity separation column 63 becomes higher than the azeotropic points of these other azeotropes under operating pressure, ethanol, which constitutes the other azeotropes, will be discharged to the outside as a by-product. In this case as well, there is a risk that the production efficiency of butadiene will decrease from the standpoint of raw material loss.
[0074] Therefore, in the impurity separation column 63, the top temperature of the column is adjusted to be below the azeotropic point of the other azeotropes mentioned above, under operating pressure. Note that if the top temperature of the impurity separation column 63 is adjusted to be below the azeotropic point of the ethanol-cyclohexane azeotrope, the state below the azeotropic point of the ethanol-ethyl acetate azeotrope will also be maintained. This is the same as the ethanol recovery column 61 of the first embodiment described with reference to Figure 2.
[0075] Furthermore, within the impurity separation column 63, the relative abundance (molar ratio) of cyclohexane-acetone and methanol-acetone in the vapor-liquid equilibrium state converges to the molar ratio of the azeotrope due to distillation in the rectification column. At this time, the acetone content in the ethanol separation product may be controlled to be equal to or greater than the number of moles required to form the cyclohexane-acetone azeotrope and methanol-acetone azeotrope, relative to the number of moles of azeotropic organic compounds (cyclohexane and methanol) also contained in the ethanol separation product. This point is the same as in the case of the ethanol recovery column 61 of the first embodiment.
[0076] For example, if the acetone content is less than the required number of moles based on the results of periodic compositional analysis of the ethanol separator or high-boiling point separator, an example can be given of adding acetone to the ethanol separator or high-boiling point separator. As a result, the number of moles of acetone in the ethanol separator or high-boiling point separator is adjusted to be equal to or greater than the required number of moles (additional step). Note that the additional supply of acetone to the ethanol separator may be carried out by providing an additional acetone supply line (not shown) that merges with the ethanol separator supply line, similar to the case of the ethanol recovery tower 61 in the first embodiment. Similarly, the additional supply of acetone to the high-boiling point separator may be carried out by providing an additional acetone supply line (not shown) that merges with the high-boiling point separator supply line to the impurity separation tower 63, and carrying out the additional acetone supply line.
[0077] In the impurity separation column 63 having the configuration described above, by-products containing cyclohexane-acetone azeotropes and methanol-acetone azeotropes flow out from the top of the column. On the other hand, ethanol-containing ethanol recovery material flows out from the bottom of the impurity separation column 63. As shown in Figure 3, the ethanol recovery material may contain ethanol-cyclohexane azeotropes and ethanol-ethyl acetate azeotropes. The presence of ethanol-cyclohexane azeotropes occurs, for example, when the acetone content in the ethanol separation material is less than the required number of moles described above. On the other hand, due to distillation separation in the impurity separation column 63, the ethanol recovery material contains almost no cyclohexane-acetone azeotropes or methanol-acetone azeotropes. This ethanol recovery material is supplied to the ethanol evaporation column 2 as an ethanol-containing raw material (Figure 1).
[0078] In the recovery section 6B of the second embodiment described with reference to Figure 3, cyclohexane-acetone azeotrope and methanol-acetone azeotrope are separated by distillation from the ethanol separator, which is the distillation separator after butadiene has been separated by distillation, to obtain ethanol recovery. Then, the ethanol recovery, which contains almost no cyclohexane-acetone azeotrope and methanol-acetone azeotrope, is reused as an ethanol-containing raw material. Therefore, by reusing the ethanol recovery, it is possible to suppress the accumulation of cyclohexane, an impurity that does not contribute to the production of butadiene, in the butadiene production plant 1. As a result, it is possible to suppress the accumulation of cyclohexane from inhibiting the reaction to produce butadiene from ethanol, and the adverse effects of formic acid produced from methanol on the equipment of the butadiene production plant 1.
[0079] In describing the second reactor 32 shown in Figure 1, it was stated that acetaldehyde recovery (acetaldehyde recycling process) and a portion of the ethanol recovery before it is supplied to the first reactor 31 (ethanol bypass supply process) may be performed on the connecting pipe on the inlet side of the second reactor 32, to which the mixed raw materials are supplied from the first reactor 31. Figures 4(a) and 4(b), and 5(a) and 5(b) show examples of configurations for adjusting the supply ratio of ethanol to acetaldehyde when supplying these acetaldehyde recovery and ethanol recovery materials to the second reactor 32.
[0080] As shown in Figures 4(a) and 4(b), the recovered acetaldehyde and ethanol are supplied via a connecting pipe that links the outlet side of the first reactor 31 and the inlet side of the second reactor 32. In the example shown in Figure 4(a), the recovered acetaldehyde and ethanol are supplied to the connecting pipe in this order from the upstream side. Similarly, in the example shown in Figure 4(b), the recovered ethanol and acetaldehyde are supplied to the connecting pipe in this order from the upstream side.
[0081] In these cases, the analyzer 332 is provided downstream of the supply location of one side of the recycled recovered material, which is either acetaldehyde recovered material or ethanol recovered material supplied to the connecting pipe, and upstream of the supply location of the other side of the recycled recovered material. The analyzer 332 analyzes the ethanol and acetaldehyde content of the mixed fluid of the mixed raw material flowing out of the first reactor 31 and one side of the recycled recovered material (acetaldehyde recovered material in the case of Figure 4(a), and ethanol recovered material in the case of Figure 4(b)) (analysis step).
[0082] In the example shown in Figure 4(a), analyzer 331A is provided in the supply path for the recovered ethanol. In the example shown in Figure 4(b), analyzer 331B is provided in the supply path for the recovered acetaldehyde. Using these analyzers 331A and 331B, the ethanol and acetaldehyde content of the other side of the recycled recovered material (ethanol recovered material in the case of Figure 4(a), and acetaldehyde recovered material in the case of Figure 4(b)) is analyzed (analysis step).
[0083] Based on these analysis results, the molar ratio (ethanol / acetaldehyde) of ethanol and acetaldehyde in the mixed fluid of the mixed raw materials supplied to the second reactor 32 and the recycled recovered materials (acetaldehyde recovered material, ethanol recovered material) is calculated. Then, the supply flow rate of at least one of the recycled recovered materials (acetaldehyde recovered material, ethanol recovered material) is adjusted so that this molar ratio falls within a predetermined range (flow rate adjustment step).
[0084] Figures 5(a) and 5(b) are similar to the examples in Figures 4(a) and 4(b) described above in that acetaldehyde recovered material and ethanol recovered material are supplied in that order from the upstream side to the connecting pipe that connects the outlet side of the first reactor 31 and the inlet side of the second reactor 32, or ethanol recovered material and acetaldehyde recovered material are supplied in that order from the upstream side. On the other hand, a difference is that an analyzer 333 for analyzing the content of ethanol and acetaldehyde is provided at a position upstream of either the supply position of the acetaldehyde recovered material or the ethanol recovered material supplied to the connecting pipe. Also, a difference from the examples shown in Figures 4(a) and 4(b) is that analyzers 331A and 331B for analyzing the content of ethanol and acetaldehyde are provided for both the acetaldehyde recovered material and the ethanol recovered material.
[0085] By using these analyzers 333, 331A, and 331B, it is possible to calculate the molar ratio (ethanol / acetaldehyde) of ethanol and acetaldehyde in the mixed fluid of the mixed raw materials supplied to the second reactor 32, the recovered acetaldehyde, and the recovered ethanol, focusing on the two components. The process of adjusting the supply flow rate of at least one of the recovered acetaldehyde and recovered ethanol so that this molar ratio falls within a predetermined range is the same as in the example described using Figures 4(a) and 4(b).
[0086] The ethanol contained in the ethanol-containing raw material processed in the butadiene production plant 1 according to each embodiment described above is not limited to biomass-derived ethanol. For example, it may be ethanol produced using microorganisms with hydrogen or carbon monoxide obtained by gasifying plastic waste as raw materials.
[0087] 1 Butadiene Production Plant 2 Ethanol Evaporation Tower 31 First Reactor 32, 32A, 32B Second Reactor 331A, 331B, 332, 333 Analyzer 4 Ethanol Separation Tower 51 Absorption Tower 52 Desorption Tower 53 Butadiene Separation Tower 54 Washing Tower 55 Dryer 6, 6A, 6B Recovery Section 61 Ethanol Recovery Tower 611 Cooler 612 Reboiler 62 Impurity Separation Tower 621 Cooler 622 Reboiler 63 Impurity Separation Tower 631 Cooler 632 Reboiler
Claims
1. A method for purifying an ethanol isolate, wherein the ethanol isolate is obtained by distilling and separating a butadiene reaction product containing 1,3-butadiene from a 1,3-butadiene-containing product obtained by contacting an ethanol-containing raw material and acetaldehyde with a 1,3-butadiene production catalyst, and is a distillation isolate containing acetaldehyde, acetone, an azeotropic organic compound which is an organic compound in an azeotropic relationship with acetone, and ethanol, and comprises a purification step of distilling and separating the azeotrope of acetone and the azeotropic organic compound from the ethanol isolate to separate the azeotrope and obtain an ethanol recovery product containing ethanol, wherein the ethanol recovery product is used as the ethanol-containing raw material.
2. The method for purifying an ethanol isolate according to claim 1, wherein the azeotropic organic compound is at least one of cyclohexane and methanol.
3. The method for purifying an ethanol isolate according to claim 1, wherein the purification step comprises: an ethanol recovery step of distilling the ethanol isolate to obtain a low-boiling-point isolate containing acetaldehyde and the azeotrope, and the ethanol recovery product; and an acetaldehyde recovery step of distilling the low-boiling-point isolate to obtain an acetaldehyde recovery product containing acetaldehyde, and a by-product containing the azeotrope, wherein the acetaldehyde recovery product is used as acetaldehyde to be contacted with the 1,3-butadiene production catalyst.
4. The method for purifying an ethanol isolate according to claim 1, wherein the purification step comprises: an acetaldehyde recovery step of distilling the ethanol isolate to obtain an acetaldehyde recovery product containing acetaldehyde and a high-boiling point isolate containing the azeotrope and ethanol; and an ethanol recovery step of distilling the high-boiling point isolate to obtain a by-product containing the azeotrope and the ethanol recovery product, wherein the acetaldehyde recovery product is used as acetaldehyde to be contacted with the 1,3-butadiene production catalyst.
5. The method for purifying an ethanol isolate according to claim 3 or 4, wherein the ethanol recovery step is carried out using a rectification column, and the temperature at the top of the rectification column is adjusted to be below the boiling point of any other azeotrope formed between ethanol and the azeotropic organic compound, cyclohexane.
6. The method for purifying an ethanol separatory product according to claim 3 or 4, wherein the acetaldehyde recovery step is carried out using a rectification column, and the temperature at the top of the purification column is adjusted to be above the boiling point of another azeotrope formed between acetaldehyde and diethyl ether, and below the boiling point of diethyl ether.
7. The method for purifying an ethanol isolate according to claim 1, wherein the amount of acetone in the ethanol isolate is equal to or greater than the required number of moles of acetone necessary for the acetone and the azeotropic organic compound to form an azeotrope, and the purification step is carried out using a rectification column, and the entire amount of the azeotropic organic compound in the ethanol isolate is separated as an azeotrope by performing continuous distillation in the rectification column to converge the molar ratio of the acetone to the azeotropic organic compound to the molar ratio of the azeotrope.
8. The method for purifying an ethanol isolate according to claim 7, further comprising an acetone addition step, in which, if the acetone content in the ethanol isolate is less than the required number of moles, acetone is added to the ethanol isolate to adjust the number of moles of acetone in the ethanol isolate to be equal to or greater than the required number of moles.
9. The method for purifying an ethanol isolate according to claim 1, wherein the molar ratio (acetone / azeotropic organic compound) of acetone to the azeotropic organic compound contained in the ethanol isolate is within the range of 0.1 or more and 10 or less.
10. A method for producing 1,3-butadiene, comprising a reaction step of supplying the ethanol-containing raw material and acetaldehyde to a reactor containing a 1,3-butadiene production catalyst and contacting the ethanol-containing raw material and acetaldehyde with the 1,3-butadiene production catalyst to convert a portion of the ethanol and acetaldehyde into 1,3-butadiene to obtain a butadiene-containing product comprising acetaldehyde, acetone, the azeotropic organic compound, ethanol and 1,3-butadiene, and comprising an ethanol recycling step of supplying the ethanol recovery product described in claim 1 to the reactor as the ethanol-containing raw material.
11. A method for producing 1,3-butadiene, comprising a reaction step of supplying the ethanol-containing raw material and acetaldehyde to a reactor containing a 1,3-butadiene production catalyst and contacting the 1,3-butadiene production catalyst to convert a portion of the ethanol and acetaldehyde into 1,3-butadiene to obtain a butadiene-containing product comprising acetaldehyde, acetone, the azeotropic organic compound, ethanol and 1,3-butadiene, and further comprising an acetaldehyde recycling step of supplying the acetaldehyde recovery product according to claim 3 or 4 to the reactor.
12. The method for producing 1,3-butadiene according to claim 11, comprising: a first reaction step of supplying the ethanol-containing raw material to a first reactor containing an acetaldehyde-producing catalyst for producing acetaldehyde from ethanol, and contacting it with the acetaldehyde-producing catalyst to obtain a mixed raw material containing the ethanol-containing raw material and acetaldehyde; and a second reaction step of supplying the mixed raw material to a second reactor, which is the reactor containing the 1,3-butadiene-producing catalyst, to obtain the butadiene-containing product, wherein in the acetaldehyde recycling step, the recovered acetaldehyde is supplied to the second reactor.
13. A method for producing 1,3-butadiene according to claim 12, comprising an ethanol recycling step of supplying the ethanol recovered material to the first reactor as the ethanol-containing raw material.
14. The process includes an ethanol bypass supply step in which a portion of the ethanol recovered material before it is supplied to the first reactor in the ethanol recycling step is supplied to the inlet side of the second reactor, and the acetaldehyde recovered material supplied in the acetaldehyde recycling step and the ethanol recovered material supplied in the ethanol bypass step are supplied via a connecting pipe connecting the outlet side of the first reactor and the inlet side of the second reactor, and includes an analysis step in which the ethanol and acetaldehyde content of the mixed fluid of the mixed raw material and one side of the recycled recovered material, and the other side of the recycled recovered material, flowing downstream of the supply position of one side of the recycled recovered material, which is the acetaldehyde recovered material or the ethanol recovered material supplied to the connecting pipe, and upstream of the supply position of the other side of the recycled recovered material, A method for producing 1,3-butadiene according to claim 13, comprising: a flow rate adjustment step, based on the results of the analysis step, adjusting the supply flow rate of at least one of the recycled materials so that the molar ratio (ethanol / acetaldehyde) of ethanol and acetaldehyde in the mixed fluid of the mixed raw material and the recycled materials of both supplied to the second reactor falls within a predetermined range.
15. The process includes an ethanol bypass supply process in which a portion of the ethanol recovered material before it is supplied to the first reactor in the ethanol recycling process is supplied to the inlet side of the second reactor, and when the acetaldehyde recovered material supplied in the acetaldehyde recycling process and the ethanol recovered material supplied in the ethanol bypass process are supplied via a connecting pipe connecting the outlet side of the first reactor and the inlet side of the second reactor, the process includes an analysis process to analyze the ethanol and acetaldehyde content of the mixed raw material, the acetaldehyde recovered material supplied in the acetaldehyde recycling process and the ethanol recovered material supplied in the ethanol bypass process, which flow upstream of either the supply position of the acetaldehyde recovered material and the ethanol recovered material supplied to the connecting pipe. A method for producing 1,3-butadiene according to claim 13, comprising: a flow rate adjustment step, which adjusts the supply flow rate of at least one of the acetaldehyde recovered material supplied in the acetaldehyde recycling step and the ethanol recovered material supplied in the ethanol bypass step, so that, based on the results of the analysis step, the molar ratio (ethanol / acetaldehyde) of ethanol and acetaldehyde in the mixed fluid of the mixed raw material, the acetaldehyde recovered material, and the ethanol recovered material supplied to the second reactor is within a predetermined range.
16. A method for producing 1,3-butadiene according to claim 10, comprising an ethanol separation step of distilling and separating the butadiene reaction product from the 1,3-butadiene-containing product obtained in the reaction step to obtain the ethanol separation product.