Method for producing phenol

Abstract

To provide a method for producing phenol that enables efficient production of high-purity phenol.SOLUTION: A method for producing phenol of the present invention comprises: a preparation step of introducing a raw material containing 4-hydroxybenzoic acid and a non-solid acid into a reaction vessel; and a reactive distillation step including heating treatment in which the interior of the reaction vessel is heated to induce decarboxylation of 4-hydroxybenzoic acid to yield phenol, and distillation treatment in which a first fraction containing phenol is extracted to the outside of the reaction vessel.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a process for producing phenol. [Background technology]

[0002] As a method for producing phenol, Patent Document 1 discloses a method for producing phenol by gas-phase oxidation of toluene in the presence of a catalyst. The method described in Patent Document 1 is a method in which a mixed gas containing toluene vapor, oxygen, and water vapor is contacted with a catalyst to produce benzoic acid by gas-phase catalytic oxidation of toluene in the mixed gas, and then oxygen is added to the benzoic acid-containing gas, which is then contacted with a catalyst to produce phenol by gas-phase catalytic oxidation of benzoic acid in the gas.

[0003] In this method, it is necessary to efficiently contact the benzoic acid-containing gas with the catalyst. However, in the gas-solid catalytic reaction, it is difficult to increase the reaction rate. When the reaction rate is low, it is necessary to secure a long reaction time or to increase the temperature of the catalyst in order to increase the contact opportunity with the catalyst. In this case, there is a problem that the production efficiency of phenol is reduced in terms of the required time and input energy. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 7-017886 Summary of the Invention [Problem to be solved by the invention]

[0005] An object of the present invention is to provide a method for producing phenol, which can efficiently produce high-purity phenol. [Means for solving the problem]

[0006] Such an object can be achieved by the present invention described in (1) to (5) below. (1) a preparation step of placing a raw material containing 4-hydroxybenzoic acid and a non-solid acid in a reaction vessel; a reactive distillation step of heating the inside of the reaction vessel to cause a decarboxylation reaction of the 4-hydroxybenzoic acid to obtain phenol, and a distillation step of extracting a first fraction containing phenol to the outside of the reaction vessel; phenol production method comprising the steps of:

[0007] (2) The method for producing phenol according to (1) above, further comprising a continuous distillation step of conducting a continuous distillation process in which the first fraction is introduced into a continuous distillation column, and components are separated based on a vapor pressure difference to thereby extract a second fraction containing phenol from the continuous distillation column.

[0008] (3) The method for producing phenol according to the above (2), wherein the first fraction is a total fraction resulting from the distillation treatment.

[0009] (4) The method for producing phenol according to the above (1), wherein the distillation treatment includes a vacuum separation operation for separating phenol from other components based on a vapor pressure difference.

[0010] (5) The method for producing phenol described in (1) above, further comprising a simple distillation step of conducting a simple distillation process in which the first fraction is introduced into a simple still and components are separated based on a vapor pressure difference to thereby extract a second fraction containing phenol to the outside of the simple still. Effect of the Invention

[0011] According to the present invention, high-purity phenol can be efficiently produced. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 is a process diagram illustrating a method for producing phenol according to a first embodiment. [Diagram 2] FIG. 2 is a schematic diagram showing an example of a production apparatus used in the phenol production method of FIG. 1. [Diagram 3]FIG. 1 is a process diagram illustrating a phenol production method according to a second embodiment. [Figure 4] FIG. 4 is a schematic diagram showing an example of a production apparatus used in the phenol production method of FIG. 3. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, the process for producing phenol of the present invention will be described in detail based on preferred embodiments shown in the accompanying drawings.

[0014] 1. First embodiment First, a method for producing phenol according to the first embodiment will be described.

[0015] Fig. 1 is a process diagram for explaining the phenol production method according to the first embodiment. Fig. 2 is a schematic diagram showing an example of a production apparatus 1 used in the phenol production method of Fig. 1.

[0016] The method for producing phenol shown in FIG. 1 includes a preparation step S102, a reactive distillation step S104, and a continuous distillation step S106. In the preparation step S102, as shown in FIG. 2, a raw material 22 containing 4-hydroxybenzoic acid and a non-solid acid 24 are placed in a reaction vessel 20. In the reactive distillation step S104, the inside of the reaction vessel 20 is heated to cause a decarboxylation reaction in 4-hydroxybenzoic acid to obtain phenol, and a distillation process is performed to extract a first fraction 26 containing phenol to the outside of the reaction vessel 20. In the continuous distillation step S106, the first fraction 26 is introduced into a continuous distillation column 30, and a continuous distillation process is performed to extract a second fraction 32 containing phenol to the outside of the continuous distillation column 30.

[0017] According to this configuration, the non-solid acid 24 serving as the catalyst can be efficiently contacted with the raw material 22, and the heating process for causing the decarboxylation reaction and the distillation process of the phenol can be simultaneously carried out, thereby making it possible to efficiently produce high-purity phenol.

[0018] 1.1. Manufacturing equipment First, the manufacturing apparatus 1 shown in FIG. 2 will be described. The production apparatus 1 shown in FIG.

[0019] The reaction vessel 20 is a vessel for performing a heating process and a distillation process. The reaction vessel 20 is not particularly limited as long as it is a vessel having a function of heating the inside. The reaction vessel 20 may also have a function of adjusting the internal pressure, a function of stirring the contents, and the like.

[0020] Examples of materials that can be used to form the reaction vessel 20 include metal materials such as stainless steel, glass materials such as quartz glass, and carbon materials. By the distillation process, a first fraction 26 containing phenol is distilled from the top, while a bottoms liquid 28 containing reaction residue is discharged from the bottom. The configuration of the reaction vessel 20 is not limited to this as long as it has the above functions.

[0021] The continuous distillation column 30 is a multi-stage distillation column that performs a continuous distillation process. The first fraction 26 described above is fed to the continuous distillation column 30. The continuous distillation column 30 has a function of generating steam at the bottom of the column, and separating each component in the first fraction 26 based on the vapor pressure difference by contacting the liquid flowing down from the top with the vapor. Examples of the continuous distillation column 30 include a plate column and a packed column. Among these, the plate column has multiple trays (not shown) inside, and has a function of separating components based on the vapor pressure difference at each tray. The packed column has packing arranged inside, and has a function of separating components based on the vapor pressure difference on the surface of the packing. The continuous distillation column 30 may also be equipped with a reboiler, a condenser, etc. (not shown).

[0022] The actual number of stages in the continuous distillation column 30 is set taking into consideration the balance between the target purity of phenol, the introduction cost, the running cost, etc., but as an example, it is preferably 3 stages or more, and more preferably 4 stages or more and 20 stages or less.

[0023] Examples of materials constituting the continuous distillation column 30 include metal materials such as stainless steel, and glass materials such as quartz glass.

[0024] The continuous distillation process efficiently purifies the target product, phenol. The second fraction 32 containing the purified phenol is taken out of the continuous distillation column 30 at a side cut position according to the physical properties of phenol. In addition, carbon dioxide CO 2 The gas components including are discharged from the top of the continuous distillation column 30. Furthermore, among the by-products, substances having a boiling point lower than that of phenol (low boiling point impurities 34) are discharged, for example, from a side cut position above the second fraction 32 of the continuous distillation column 30. Furthermore, among the by-products, substances having a boiling point higher than that of phenol (high boiling point impurities 36) are discharged, for example, from the bottom of the continuous distillation column 30.

[0025] The configuration of the continuous distillation column 30 is not limited to this as long as it has the above-mentioned functions. The continuous distillation column 30 may be provided as needed, and may be omitted from the production apparatus 1 when high-purity phenol is obtained in the first fraction 26, for example.

[0026] 1.2. Method for producing phenol Next, the process for producing phenol shown in FIG. 1 will be described.

[0027] 1.2.1. Preparation process In the preparation step S102, a raw material 22 containing 4-hydroxybenzoic acid and a non-solid acid 24 are placed in a reaction vessel 20. Hereinafter, 4-hydroxybenzoic acid is also referred to as "4HBA."

[0028] 4HBA may be a compound derived from fossil resources or a compound derived from biomass. By using a compound derived from biomass as the raw material 22, it is possible to contribute to carbon neutrality in the production of phenol. For example, a fermentation production process using microorganisms is preferably used for the production of biomass-derived 4HBA. For example, sugar is used as the starting material to be fermented. Sugar, especially monosaccharides, are abundant in nature and therefore easy to obtain. Biomass refers to organic resources derived from plants. Specifically, examples include those that are converted and stored in the form of sugars such as starch, glucose, and cellulose, the bodies of animals that grow by eating plants, and products made by processing plants and animals.

[0029] The non-solid acid 24 may be an inorganic acid or an organic acid. Examples of inorganic acids include hydrochloric acid, nitric acid, sulfuric acid, phosphoric acid, and perchloric acid. Examples of organic acids include formic acid and acetic acid. The non-solid acid 24 may be a mixture of two or more of these. Of these, hydrochloric acid or sulfuric acid is preferably used as the non-solid acid 24 from the viewpoints of ease of handling, cost, and strength of the acid site, and sulfuric acid is more preferably used.

[0030] The raw material 22 may be liquid or solid. The former may be an aqueous solution of an alkali metal salt of 4HBA. Examples of the alkali metal contained in the alkali metal salt include sodium and potassium. The latter may be crude crystals of 4HBA or crystals obtained by purifying 4HBA from the former liquid. Since the solid raw material 22 does not contain a solvent, the amount of heat required for the heating process in the reactive distillation step S104 described later can be reduced. Incidentally, "not containing a solvent" means that the content of the solvent in the raw material 22 is 1% by mass or less.

[0031] Compounds (biomass-derived compounds) obtained by the fermentation production process may contain various organic acids and inorganic acids other than 4HBA as by-products of fermentation. These acids can be reused as the non-solid acid 24. Therefore, by using a biomass-derived compound, an intermediate containing 4HBA, which is the raw material 22, and an acid that can be used as the non-solid acid 24 can be produced. In this case, in the preparation step S102, the intermediate may be charged into the reaction vessel 20. This can reduce the number of steps and improve the efficiency of the production method.

[0032] The above intermediates can be produced, for example, as follows. In biomass-derived compounds, crude crystals (crude crystals) of 4HBA often exist in the form of an alkali metal salt. Examples of alkali metals contained in alkali metal salts include sodium and potassium. When this alkali metal salt of 4HBA is placed in an acid precipitation vessel (not shown) and an organic acid or inorganic acid as described above is added, crude crystals of 4HBA are precipitated and an alkali metal acid salt is generated as a by-product. The alkali metal acid salt is generated in a state dissolved in the acid.

[0033] The pH inside the acid precipitation vessel is preferably 1.5 to 4.0, more preferably 2.0 to 3.5, and even more preferably 2.5 to 3.0. This allows 4HBA crystals to be sufficiently precipitated and increases the solubility of by-products. If the pH is below the lower limit, the solubility of by-products may decrease and the chemical resistance of the acid precipitation vessel may be adversely affected. On the other hand, if the pH is above the upper limit, the precipitation efficiency of 4HBA crystals may decrease.

[0034] The temperature inside the acid precipitation vessel is not particularly limited, but is preferably 10° C. to 60° C., and more preferably 20° C. to 50° C. This can increase the efficiency of precipitation of 4HBA crystals. In addition, the solubility of by-products can be appropriately ensured.

[0035] Then, the crude crystals of 4HBA to which the acid has been added are recovered by solid-liquid separation, thereby obtaining an intermediate containing the raw material 22 and the non-solid acid 24.

[0036] The amount of the non-solid acid 24 added is not particularly limited, but is preferably 0.1 to 10.0 [mol%], more preferably 0.4 to 7.0 [mol%], and even more preferably 0.7 to 5.0 [mol%] relative to the total amount of the 4HBA and the non-solid acid 24. This allows a necessary and sufficient amount of the non-solid acid to act on the 4HBA. As a result, the yield of phenol is sufficiently increased, and adverse effects associated with an excess amount of the non-solid acid 24, such as an increase in the procurement cost of the non-solid acid 24 and the cost of treating the waste liquid, can be suppressed.

[0037] 1.2.2. Reactive distillation process In the reactive distillation step S104, the inside of the reaction vessel 20 is heated to cause a decarbonation reaction of 4HBA to obtain phenol, and a distillation process is performed to extract the first fraction 26 containing phenol from the reaction vessel. In other words, the heating process and the distillation process are performed inside the same reaction vessel 20.

[0038] 1.2.2.1. Heat treatment In the heat treatment, the inside of the reaction vessel 20 is heated. By carrying out the heat treatment, the non-solid acid 24 acts on the 4HBA contained inside the reaction vessel 20. This breaks the strong carbon-carbon bond of the 4HBA. In other words, the non-solid acid 24 acts as a catalyst that promotes the decarboxylation reaction. As a result, phenol is obtained from the 4HBA. The temperature of the generated phenol drops to about 200° C. or less, and it exists in a gas-liquid mixed state.

[0039] Under heating, 4HBA contained in the raw material 22 is liquefied or vaporized, and can efficiently come into contact with the non-solid acid 24. Therefore, the efficiency of the decarboxylation reaction accompanying the heat treatment can be increased more than when the catalyst is a solid.

[0040] The temperature in the heat treatment is preferably 200 to 270° C., more preferably 210 to 260° C., and further preferably 220 to 240° C. By carrying out the heat treatment at this temperature, the decarboxylation reaction is further promoted, and the energy efficiency in the heat treatment can be improved.

[0041] If the heating temperature is less than the lower limit, the effect of promoting the decarboxylation reaction by the non-solid acid 24 may decrease, resulting in a decrease in the yield of phenol. On the other hand, if the heating temperature is more than the upper limit, the yield may not increase much, while the energy consumption may increase, resulting in an increase in production cost.

[0042] The heating time at such a heating temperature is appropriately set in consideration of the reaction rate of the decarboxylation reaction and other reaction conditions, and is, for example, preferably from 5 minutes to 12 hours, more preferably from 10 minutes to 6 hours, and even more preferably from 15 minutes to 4 hours, which can sufficiently increase the production efficiency of phenol.

[0043] The pressure inside the reaction vessel 20 during the heat treatment is not particularly limited, and may be normal pressure, less than normal pressure, or greater than normal pressure. Normal pressure refers to 86 kPa or more and 106 kPa or less. If the pressure is normal pressure or less than normal pressure, the pressure resistance of the reaction vessel 20 can be reduced, so that the reaction vessel 20 can be easily enlarged.

[0044] The atmosphere inside the reaction vessel 20 during the heat treatment is not particularly limited, and may be, for example, an air atmosphere, an inert gas atmosphere, etc. Among these, an inert gas atmosphere may be selected when suppressing a side reaction such as the oxidation of phenol. Examples of the inert gas include nitrogen, carbon dioxide, and argon.

[0045] 1.2.2.2. Distillation process In the distillation process, the difference in boiling points is utilized to distill off the first fraction 26 containing phenol in the reaction vessel 20 after the heat treatment. The first fraction 26 may be a part of the fraction from the distillation process, but in this embodiment, it is the entire fraction from the distillation process. That is, in this embodiment, in the above-mentioned atmospheric pressure separation operation or reduced pressure separation operation, instead of feeding each component based on the vapor pressure difference, the entire fraction is fed to the continuous distillation column 30 as the first fraction 26. This allows the distilled phenol to be supplied to the continuous distillation step S106 without leakage. As a result, it becomes easier to increase the yield of phenol.

[0046] Furthermore, by continuously carrying out the heating treatment and the distillation treatment in the same reaction vessel 20, the phenol generated by the decarboxylation reaction can be distilled in a short time. This makes it possible to suppress the denaturation of phenol, and therefore to efficiently produce high-purity phenol.

[0047] The distillation process may include an atmospheric pressure separation operation, but preferably includes a reduced pressure separation operation. The atmospheric pressure separation operation is an operation in which phenol and other components are separated based on a vapor pressure difference under atmospheric pressure. In contrast, the reduced pressure separation operation is an operation in which phenol and other components are separated based on a vapor pressure difference under reduced pressure. The reduced pressure separation operation has the advantages of being easy to operate and easily adjusting the distillate amount, since the components can be separated by controlling the degree of reduced pressure.

[0048] The pressure inside the reaction vessel 20 during the distillation process is preferably 0.01 atm (0.001 MPa) or more and less than normal pressure (0.1 MPa), and more preferably 0.1 atm (0.01 MPa) or more and 0.9 atm (0.09 MPa) or less. This makes it possible to efficiently distill the first fraction 26 while suppressing bumping.

[0049] If the pressure in the distillation process is less than the lower limit, impurities having a boiling point higher than that of phenol are likely to be mixed into the first fraction 26, which may ultimately result in a decrease in the purity of phenol. On the other hand, if the pressure in the distillation process exceeds the upper limit, the amount of phenol distilled decreases, which may result in a decrease in the production efficiency of phenol.

[0050] On the other hand, in the distillation process, a bottoms liquid 28 containing components (reaction residues) not contained in the first fraction 26 is discharged. Depending on the boiling point of the non-solid acid 24, the bottoms liquid 28 may contain the non-solid acid 24. In this case, the non-solid acid 24 can be recovered, and the non-solid acid 24 after purification can be reused. This can reduce the manufacturing cost (procurement cost of the non-solid acid 24). When the catalyst is a solid acid such as zeolite, the acid sites are deactivated relatively quickly. This is thought to be because the pores of zeolite have a diameter only large enough for low molecular weight organic molecules to pass through, and are quickly closed when a substance enters. For this reason, even if the solid acid itself is recovered, it is difficult to reuse it.

[0051] In addition, when the non-solid acid 24 is used, the non-solid acid 24 can remain in the reaction vessel 20 even after the distillation process unless the bottoms 28 are discharged. In this case, by adding new raw material 22 to the reaction vessel 20, the decarboxylation reaction can be caused without adding additional non-solid acid 24. That is, the non-solid acid 24 is slow to deactivate the acid sites and acts as a catalyst for a long time. This allows a large amount of phenol to be produced using a unit amount of non-solid acid 24, which can further reduce costs. On the other hand, since the solid acid is fast in deactivating the acid sites as described above, it is difficult to continue the decarboxylation reaction even if the raw material 22 is added in this way.

[0052] Furthermore, the non-solid acid 24 has high work efficiency when introduced into the reaction vessel 20. In addition, since the non-solid acid 24 is a homogeneous catalyst, the efficiency of the heating treatment and the stirring treatment is relatively high. On the other hand, since the solid acid is in a solid state such as a powder, the difficulty of introducing the solid acid into the reaction vessel 20 is high. In addition, since the solid acid is a so-called heterogeneous catalyst, the efficiency of the heating treatment and the stirring treatment is relatively low.

[0053] 1.2.3. Continuous distillation process In the continuous distillation step S106, a continuous distillation process is performed in which the first fraction 26 shown in Fig. 2 is introduced into a continuous distillation column 30, and a second fraction 32 containing phenol is taken out of the continuous distillation column 30. As a result, the second fraction 32 is recovered as a phenol product.

[0054] In the continuous distillation column 30, a distillate liquid obtained by condensing the generated steam and a bottom liquid remaining without evaporation are generated at each stage. The distillate liquid is supplied to the next higher stage. The bottom liquid is refluxed to the next lower stage. By refluxing in each stage, it is possible to separate phenol from impurities while reducing the amount of phenol loss. This allows the purity and yield of phenol in the second fraction 32 to be sufficiently increased. In addition, the continuous distillation process allows the separation of low-boiling-point impurities 34, which have a boiling point lower than that of phenol, with high accuracy. The low-boiling-point impurities 34 are highly volatile, and if they are mixed into the phenol product, they will cause poor quality such as bad odors. Therefore, the continuous distillation process allows the quality of the phenol produced to be further improved. Examples of the low boiling point impurities 34 include ammonia, methyl mercaptan, hydrogen sulfide, methyl sulfide, methyl disulfide, trimethylamine, aldehydes, isobutanol, ethyl acetate, methyl isobutyl ketone, toluene, styrene, propionic acid, and isovaleric acid.

[0055] Furthermore, in the continuous distillation step S106, it is preferable that the first fraction 26 is fed to the continuous distillation column 30 in a sufficiently heated state (at least in a state in which phenol is vaporized). For example, in the production apparatus 1 shown in FIG. 2, by connecting the reaction vessel 20 and the continuous distillation column 30 with a pipe, it is possible to feed the first fraction 26 to the continuous distillation column 30 while maintaining the temperature of the first fraction 26. In this way, the efficiency of component separation in the continuous distillation column 30 is increased compared to when the first fraction is fed without being heated. As a result, phenol of higher purity can be produced more efficiently.

[0056] On the other hand, in the continuous distillation process, carbon dioxide CO is discharged from the top of the continuous distillation column 30. 2 is discharged, low boiling point impurities 34 are discharged from the side cut position, and high boiling point impurities 36 are discharged from the bottom of the column.

[0057] In the continuous distillation column 30, each component can be separated with high accuracy based on the vapor pressure difference, so that the amount of low boiling point impurities 34 and high boiling point impurities 36 mixed in the second fraction 32 can be sufficiently reduced. This allows the purity of phenol in the second fraction 32 to be sufficiently increased.

[0058] By recovering the second fraction 32 obtained as described above, high-purity phenol can be obtained efficiently.

[0059] The continuous distillation step S106 may be provided as necessary, and may be omitted, for example, when high-purity phenol is obtained in the first fraction 26. In this case, the first fraction 26 is recovered as a phenol product.

[0060] 2. Second embodiment Next, a method for producing phenol according to the second embodiment will be described.

[0061] Fig. 3 is a process diagram for explaining the phenol production method according to the second embodiment. Fig. 4 is a schematic diagram showing an example of a production apparatus 1 used in the phenol production method of Fig. 3.

[0062] The second embodiment will be described below, focusing on the differences from the first embodiment and omitting the description of the similarities. Note that in Figures 3 and 4, the same reference numerals are used for the same configurations as in Figures 1 and 2.

[0063] The phenol production method shown in FIG. 3 is similar to the phenol production method shown in FIG. 1, except that in the reactive distillation step S104, each component is fed, and a simple distillation step S206 is provided instead of the continuous distillation step S106.

[0064] 2.1. Manufacturing equipment First, the manufacturing apparatus 1 shown in FIG. 4 will be described. The production apparatus 1 shown in FIG. 4 includes a reaction vessel 20 and a simple distiller 40.

[0065] A branch pipe 21 for separating fractions is connected to the reaction vessel 20 shown in Fig. 4. The branch pipe 21 is used to individually circulate and recover the components separated based on the vapor pressure difference in the vacuum separation operation. The branch pipe 21 shown in Fig. 4 is, for example, a pipe for carbon dioxide CO 2 The branch pipe 21 is configured to separate and recover the low boiling point impurities 27 and the first fraction 26 from each other. Therefore, the branch pipe 21 may be provided with an opening / closing valve (not shown). Also, instead of the branch pipe 21, a pipe that is exclusively connected to the reaction vessel 20 and that individually circulates the components separated based on the vapor pressure difference may be used.

[0066] The simple distillation apparatus 40 is a vessel that performs a simple distillation process. The above-mentioned first fraction 26 is fed to the simple distillation apparatus 40. The simple distillation apparatus 40 performs a simple distillation process on the fed first fraction 26, and has a function of separating each component in the first fraction 26 based on the vapor pressure difference. Compared to the continuous distillation column 30, the simple distillation apparatus 40 is easier to miniaturize, and the introduction cost and running cost are relatively low.

[0067] A branch pipe 41 for separating fractions is connected to the simple distillation apparatus 40 shown in FIG. 4. The branch pipe 41 is used for individually circulating and recovering the components separated based on the vapor pressure difference in the reduced pressure separation operation. The branch pipe 41 shown in FIG. 4 is configured, as an example, for separating and recovering the low boiling point impurities 44 and the second fraction 42 from each other. Therefore, the branch pipe 41 may be provided with an opening and closing valve (not shown). Also, instead of the branch pipe 41, a pipe that is exclusively connected to the simple distillation apparatus 40 and individually circulates the components separated based on the vapor pressure difference may be used.

[0068] Examples of materials that can be used to form the simple still 40 include metal materials such as stainless steel, and glass materials such as quartz glass.

[0069] The configuration of the simple distiller 40 is not limited to this as long as it has the above-mentioned functions. Also, the production apparatus 1 shown in FIG.

[0070] 2.2. Method for producing phenol Next, the process for producing phenol shown in FIG. 3 will be described.

[0071] 2.2.1. Preparation process The preparation step S102 shown in FIG. 3 is similar to the preparation step S102 shown in FIG.

[0072] 2.2.2. Reactive distillation process In the reactive distillation step S104 shown in FIG. 3, first, as in the first embodiment, the inside of the reaction vessel 20 is heated to perform a heat treatment for causing a decarboxylation reaction of 4HBA to obtain phenol.

[0073] Next, the phenol and by-products produced are separated by a vacuum separation operation. Specifically, carbon dioxide CO 2 In this embodiment, the low boiling point impurities 27 and the first fraction 26 are discharged separately. This makes it possible to increase the purity of phenol in the first fraction 26 compared to the first embodiment.

[0074] When the low boiling point impurities 27 are distilled off, the pressure inside the reaction vessel 20 may be within the above-mentioned range, but is preferably set to 0.4 atmospheres (0.04 MPa) or more and less than normal pressure (0.1 MPa). This makes it possible to more selectively separate and distill off impurities (low boiling point impurities 27) having a higher vapor pressure than phenol. As a result, a high-quality phenol product with a low concentration of low boiling point impurities 27 is finally obtained.

[0075] When the first fraction 26 is distilled after the low boiling point impurities 27 are distilled, the pressure inside the reaction vessel 20 is preferably lower than that when the low boiling point impurities 27 are distilled, specifically, it is preferably 0.1 atm (0.01 MPa) or more and less than 0.4 atm (0.04 MPa). This makes it possible to separate phenol more selectively and recover the first fraction 26 containing high-purity phenol.

[0076] 2.2.3.Simple distillation process In the simple distillation step S206 shown in Fig. 3, a simple distillation process is performed in which the first fraction 26 shown in Fig. 4 is introduced into a simple distiller 40, and a second fraction 42 containing phenol is taken out of the simple distiller 40. As a result, the second fraction 42 is recovered as a phenol product. In the simple distillation process, energy consumption is reduced compared to the continuous distillation process. Therefore, in the simple distillation process, the purity of phenol in the recovered phenol product can be further increased while reducing the introduction cost and running cost of the apparatus.

[0077] In the simple distillation process, the inside of the simple distiller 40 is heated in the same manner as in the above-mentioned heating process. The temperature in the simple distillation process is preferably 180 to 200°C, and more preferably 185 to 195°C. By carrying out the simple distillation process at this temperature, it is possible to distill phenol while suppressing energy consumption. In addition, it is possible to suppress the distillation of high boiling point impurities.

[0078] After heating the inside of the simple distillation still 40, a normal pressure separation operation or a reduced pressure separation operation is performed, but a reduced pressure separation operation is preferably used. A reduced pressure separation operation allows components to be separated by adjusting the degree of vacuum, which has the advantages of being easy to operate and of being able to easily adjust the amount of distillate. Specifically, low boiling point impurities 44 and the second fraction 42 are sequentially recovered while being separated according to the degree of vacuum.

[0079] When the low boiling point impurities 44 are distilled off, the pressure inside the simple distiller 40 may be within the range described above, but is preferably set to 0.4 atmospheres (0.04 MPa) or more and less than normal pressure (0.1 MPa). This makes it possible to more selectively separate and distill off impurities (low boiling point impurities 44) that have a higher vapor pressure than phenol. As a result, a high-quality phenol product with a low concentration of low boiling point impurities 44 is finally obtained.

[0080] When the second fraction 42 is distilled after the low boiling point impurities 44 are distilled, the pressure inside the simple still 40 is preferably lower than that when the low boiling point impurities 44 are distilled, specifically, it is preferably 0.1 atm (0.01 MPa) or higher and lower than 0.4 atm (0.04 MPa). This makes it possible to separate phenol more selectively and recover the second fraction 42 containing high-purity phenol.

[0081] On the other hand, in the simple distillation process, a bottoms liquid 48 containing components (reaction residues) not contained in the second fraction 42 is discharged.

[0082] In the second embodiment as described above, the same effects as in the first embodiment can be obtained. In addition, in this embodiment, phenol and low boiling point impurities can be separated in both the reactive distillation step S104 and the simple distillation step S206. This makes it possible to produce a phenol product with a low concentration of low boiling point impurities while keeping running costs low.

[0083] 3. Purity and yield of phenol The purity of phenol in the produced phenol product is preferably 95% or more, more preferably 97% or more, and even more preferably 98% or more. Such a phenol product has a sufficiently high purity of phenol and is therefore particularly useful as a raw material for various purposes.

[0084] The content of phenol in the phenol product is measured using a high performance liquid chromatograph (LaChrom Elite manufactured by Hitachi High-Technologies Corporation, analytical column: Inertsil ODS-4 manufactured by GL Sciences Inc.) The purity of phenol in the phenol product is calculated as the ratio of the mass of phenol in the phenol product to the total mass of the phenol product.

[0085] Moreover, the phenol yield in the phenol production method is preferably 70% or more, more preferably 80% or more, and even more preferably 85% or more. With such a yield, the production cost of phenol can be sufficiently reduced.

[0086] The yield of phenol is calculated by the following formula: The molar amount of phenol in the following formula is calculated from the content of phenol measured by the above-mentioned high performance chromatography.

[0087] Phenol yield (%) = moles of phenol produced / moles of 4HBA charged × 100

[0088] 4. Advantages of the above embodiment As described above, the method for producing phenol according to the embodiment includes a preparation step S102 and a reactive distillation step S104. In the preparation step S102, a raw material 22 containing 4-hydroxybenzoic acid (4HBA) and a non-solid acid 24 are placed in a reaction vessel 20. In the reactive distillation step S104, a heat treatment is performed in which the inside of the reaction vessel 20 is heated to cause a decarboxylation reaction of 4-hydroxybenzoic acid to obtain phenol, and a distillation treatment is performed in which a first fraction 26 containing phenol is taken out of the reaction vessel 20.

[0089] According to this configuration, high-purity phenol can be efficiently produced. In particular, unlike solid acids, the non-solid acid 24 acts as a catalyst for a long time when new raw material 22 is added. Therefore, a large amount of phenol can be produced using a unit amount of non-solid acid 24, and from this viewpoint as well, phenol can be efficiently produced. In addition, the non-solid acid 24 has the effect of being more efficient in the operation of adding the non-solid acid 24 to the reaction vessel 20 than solid acids, and being a homogeneous catalyst, the efficiency of the heating process and the stirring process is relatively high.

[0090] The phenol production method according to the embodiment may further include a continuous distillation step S106. In the continuous distillation step S106, the first fraction 26 is introduced into a continuous distillation column 30, and components are separated based on a vapor pressure difference, thereby extracting a second fraction 32 containing phenol from the continuous distillation column 30.

[0091] According to this configuration, it is possible to sufficiently increase the purity while suppressing the amount of phenol loss in the continuous distillation column 30. As a result, it is possible to more efficiently produce phenol of particularly high purity.

[0092] In the phenol production method according to the embodiment, the first fraction 26 may be the entire fraction resulting from the distillation process.

[0093] According to this configuration, the distilled phenol can be supplied to the continuous distillation step S106 without leakage, which makes it easier to increase the yield of phenol.

[0094] In the method for producing phenol according to the embodiment, the distillation process may include a vacuum separation operation. The vacuum separation operation is an operation for separating phenol from other components based on a vapor pressure difference.

[0095] According to such a configuration, the components can be separated by adjusting the degree of vacuum, which provides the advantages of easy operation and easy adjustment of the amount of distillate.

[0096] The method for producing phenol according to the embodiment may further include a simple distillation step S206. In the simple distillation step S206, the first fraction 26 is introduced into a simple distiller 40, and components are separated based on a vapor pressure difference to perform a simple distillation process in which a second fraction 42 containing phenol is taken out of the simple distiller 40.

[0097] According to this configuration, it is possible to further increase the purity of phenol in the recovered phenol product while reducing the introduction cost and running cost of the apparatus.

[0098] Although the method for producing phenol of the present invention has been described based on the above embodiment, the present invention is not limited to the above embodiment. For example, the method for producing phenol of the present invention may be the method for producing phenol of the present invention in which any step is added to the above embodiment. EXAMPLES

[0099] Next, specific examples of the present invention will be described. 5. Phenol production 5.1. Example 1 Among the steps shown in Fig. 1, the preparation step and the reactive distillation step were carried out in order to recover the phenol product. The details are explained below.

[0100] First, a fermentation liquid containing 4HBA was prepared as a raw material liquid. Next, sulfuric acid was added to this raw material liquid. After the addition of sulfuric acid, the pH of the raw material liquid was 2.8, and the temperature of the raw material liquid was 25°C. Then, crude crystals (intermediate) of 4HBA to which sulfuric acid had been added were collected by solid-liquid separation.

[0101] Next, the recovered intermediate was charged into a reaction vessel (preparation step). As a result, the raw material containing 4HBA and sulfuric acid, which is a non-solid acid, were contained inside the reaction vessel.

[0102] Next, the contents of the reaction vessel were subjected to a heat treatment. This caused a decarboxylation reaction of 4HBA to produce phenol. Then, a distillation treatment was performed (reactive distillation step). As a result, a first fraction containing phenol was recovered as a phenol product. The conditions for producing phenol are as shown in Table 1.

[0103] 5.2. Example 2 A phenol product was recovered in the same manner as in Example 1, except that the non-solid acid was changed to hydrochloric acid.

[0104] 5.3. Example 3 In the method for producing phenol, a phenol product was recovered in the same manner as in Example 1, except that the raw material 4HBA and the non-solid acid sulfuric acid were each placed inside a reaction vessel.

[0105] 5.4. Example 4 A phenol product was recovered in the same manner as in Example 3, except that the non-solid acid was changed to hydrochloric acid.

[0106] 5.5. Comparative Example 1 The phenol product was recovered in the same manner as in Example 2, except that a solid acid (Na-X zeolite) was used instead of the non-solid acid.

[0107] 5.6. Comparative Example 2 The phenol product was recovered in the same manner as in Example 2, except that a solid acid (ZSM-5(H+) zeolite) was used instead of the non-solid acid.

[0108] 5.7. Comparative Example 3 A phenol product was recovered in the same manner as in Comparative Example 1, except that a solid acid (Na-X zeolite) was used instead of the non-solid acid, and the following treatment was carried out instead of the reactive distillation treatment.

[0109] First, 4HBA was placed in a heating tank and heated to vaporize the 4HBA. Next, the vaporized 4HBA was passed through a tank filled with solid acid. This caused a decarboxylation reaction between 4HBA and the solid acid through a gas-solid reaction, producing phenol. The conditions for the heat treatment of 4HBA during the decarboxylation reaction were the temperatures shown in Table 1.

[0110] 6. Evaluation of phenol production methods The phenol production methods in the respective Examples and Comparative Examples were evaluated as follows.

[0111] 6.1. Purity of phenol The purity of phenol was calculated for the phenol products recovered in each Example and Comparative Example. The calculation results are shown in Table 1.

[0112] 6.2. Phenol yield (yield at first charge) The phenol yield (yield at the time of initial addition) was calculated for the phenol products recovered in each Example and Comparative Example. The calculation results are shown in Table 1.

[0113] 6.3. Change in yield when additional raw materials are added (ratio to the yield when first added) In each Example and Comparative Example, after the phenol product was recovered, 4HBA was added as a raw material without discharging the bottoms from the reaction vessel. Next, the added raw material was again subjected to heating, distillation and continuous distillation to recover the phenol product. The phenol yield was calculated for the recovered phenol product, and the ratio was calculated when the phenol yield calculated in 6.2 (the yield at the time of the initial charge) was taken as 100%. The calculation results are shown in Table 1.

[0114] [Table 1]

[0115] As is clear from Table 1, in the phenol production method of each Example, a phenol product containing phenol at a high purity (purity of 95% or more) could be recovered by performing a heating treatment and a distillation treatment in the same reaction vessel. In addition, in each Example, the yield of high-purity phenol was ensured to be 70% or more, and the phenol product was recovered at a high yield. In addition, in the phenol production method of each Example, the yield when only the raw material was additionally added without additionally adding the acid as a catalyst was comparable to the yield when the initial addition was made. The above evaluation results support the fact that according to the present invention, high-purity phenol can be produced efficiently and at low cost.

[0116] 7. Comparison of travel time The purity and yield of the recovered phenol product, as well as the time required for production, were compared for the phenol production methods in Example 5 and Comparative Example 4 described below. The phenol production conditions and the comparison results in Example 5 and Comparative Example 4 are shown in Table 2. Note that the phenol production method in Comparative Example 4 is a method in which a phenol product is recovered by employing a phenol extraction process using IPE (isopropyl ether) instead of a distillation process.

[0117] [Table 2]

[0118] As shown in Table 2, it was found that the phenol production method in Example 5 not only had high purity and high yield of the recovered phenol product, but also required a short time. In contrast, it was found that the phenol production method in Comparative Example 4 (method using extraction treatment) had a slightly low purity of the recovered phenol product and required a long time.

[0119] 8. Evaluation of the case where a simple distillation process and a continuous distillation process are added 8.1. Example 6 In Example 6, a phenol product was recovered in the same manner as in Example 1. That is, using the production apparatus 1 shown in FIG. 2, the first fraction 26 distilled from the reaction vessel 20 was recovered as a phenol product. The purity and impurity concentration of the recovered phenol product were then measured. The measurement results are shown in Table 3. The impurity concentration was calculated by the following formula.

[0120] Impurity concentration (%) = area of ​​each impurity peak / area of ​​all peaks detected in the chromatogram × 100

[0121] Further, a gas chromatograph mass spectrometer was used to measure the impurity concentration, and the following GCMS (gas chromatograph mass spectrometry) conditions and HS (headspace) analysis conditions were adopted as the measurement conditions.

[0122] ·GCMS conditions Gas chromatograph mass spectrometer: Shimadzu GCMS-QP2020 Column: Rtx-5ms (length 60 m, inner diameter 0.32 mm, liquid phase film thickness 1.0 μm) Carrier gas: He Carrier gas control: constant linear velocity (40 cm / sec) Carrier gas inlet temperature: 230℃ Sample injection method: Split method Split ratio: 10:1 Ion source temperature: 200℃ Interface temperature: 230℃ Measurement mode: Scan Sample: 0.1g of each sample sealed in a 20mL headspace vial

[0123] ·HS analysis conditions Headspace device: Shimadzu HS-20Trap Headspace Condition: Loop Mode Oven temperature: 150℃ Sample warming time: 30 minutes

[0124] 8.2. Example 7 In Example 7, the production apparatus 1 shown in FIG. 4 was used, and the first fraction 26 distilled from the reaction vessel 20 was recovered as a phenol product. The purity and impurity concentration of the recovered phenol product were then measured. The measurement results are shown in Table 3.

[0125] 8.3. Example 8 In Example 8, a phenol product was recovered in the same manner as in Example 7, except that a simple distillation step shown in FIG. 3 was added. That is, using the production apparatus 1 shown in FIG. 4, the second fraction 42 distilled from the simple still 40 was recovered as a phenol product. The purity and impurity concentration of the recovered phenol product were then measured. The measurement results are shown in Table 3.

[0126] 8.4. Example 9 In Example 9, a phenol product was recovered in the same manner as in Example 6, except that the continuous distillation step shown in Figure 1 was added. That is, using the production apparatus 1 shown in Figure 2, the second fraction 32 distilled from the continuous distillation column 30 was recovered as a phenol product. The purity and impurity concentration of the recovered phenol product were then measured. The measurement results are shown in Table 3.

[0127] 8.5.Reference example The impurity concentrations of the raw materials fed into the production apparatus 1 in Examples 6 to 9 are shown in Table 3 as reference examples.

[0128] [Table 3]

[0129] As shown in Table 3, by adding a simple distillation step or a continuous distillation step to the preparation step and the reactive distillation step, it was possible to achieve high purity of phenol in the recovered phenol product (Examples 8 and 9). In addition, in these Examples, it was also possible to achieve low concentrations of impurities such as aldehydes, propionic acid, and isovaleric acid. These impurities are known to cause bad odors. Therefore, it was also confirmed that according to the present invention, it is possible to produce phenol with reduced quality defects such as bad odors. [Explanation of symbols]

[0130] 1 Manufacturing equipment 20 Reaction vessel 21 Branch piping 22 Raw materials 24 Non-solid acids 26 First fraction 27 Low boiling point impurities 28 Canned liquid 30 Continuous distillation column 32 Second fraction 34 Low boiling point impurities 36 High boiling point impurities 40 Simple still 41 Branch piping 42 Second fraction 44 Low boiling point impurities 48 Canned liquid CO 2 carbon dioxide S102 Preparation process S104 Reactive distillation process S106 Continuous distillation process S206 Simple distillation process

Claims

1. A preparation step of placing a raw material containing 4-hydroxybenzoic acid and a non-solid acid in a reaction vessel; a reactive distillation step of heating the inside of the reaction vessel to cause a decarboxylation reaction of the 4-hydroxybenzoic acid to obtain phenol, and a distillation step of extracting a first fraction containing phenol to the outside of the reaction vessel; phenol production method comprising the steps of:

2. 2. The method for producing phenol according to claim 1, further comprising a continuous distillation step of conducting a continuous distillation process in which the first fraction is introduced into a continuous distillation column, and components are separated based on a vapor pressure difference to thereby extract a second fraction containing phenol outside the continuous distillation column.

3. 3. The method for producing phenol according to claim 2, wherein the first fraction is a total fraction resulting from the distillation treatment.

4. 2. The method for producing phenol according to claim 1, wherein the distillation treatment includes a vacuum separation operation for separating phenol from other components based on a vapor pressure difference.

5. 2. The method for producing phenol according to claim 1, further comprising a simple distillation step of conducting a simple distillation process in which the first fraction is introduced into a simple distillation vessel and components are separated based on a vapor pressure difference, thereby extracting a second fraction containing phenol to the outside of the simple distillation vessel.

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