Phenol production method and phenol composition

Abstract

To provide a method for producing phenol in which oil-water separation in the oil-water separation step of the phenol production method can be performed satisfactorily.SOLUTION: A method for producing phenol includes: a neutralization step of neutralizing an acid decomposition reaction liquid of cumene hydroperoxide with alkali; an oil-water separation step of separating the neutralized reaction liquid into an oil-phase liquid and a water-phase liquid; and a cleaning step of mixing a water-washing water into and clean the oil-phase liquid, and then, separating the mixed liquid into oil-phase liquid and water-phase liquid. Therein, the mixed liquid of the oil-phase liquid and the water-washing water in the cleaning step contains a water by 14.5 mass% or more with respect to a total mass of the mixed liquid.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for producing phenol and a phenol composition. [Background technology]

[0002] Phenol is generally produced industrially by the cumene process, which includes an oxidation step in which cumene is oxidized to produce a reaction liquid containing cumene hydroperoxide (hereinafter referred to as CHP), an acid decomposition step in which CHP is acid-decomposed to produce phenol and acetone, a neutralization washing step in which the decomposition product liquid is neutralized and washed to remove salts, and a recovery step in which components other than phenol are separated from the washing liquid to recover phenol.

[0003] In the acid decomposition process of the cumene process for producing phenol, an acid such as sulfuric acid is added to efficiently decompose CHP. If any acid remains in the acid decomposition product, it will act as a catalyst for generating heavy products when heated in the subsequent recovery process. Therefore, in the neutralization washing process prior to the recovery process, the acid decomposition product is contacted with wash water containing an alkali such as sodium carbonate, and the acid is extracted and removed into the wash water. At the same time, the neutralization washing process also extracts and removes organic acids that are generated as impurities in the oxidation process for producing CHP.

[0004] The wash water that comes into contact with the acid decomposition product contains the extracted acid and salts, which, when carried into the recovery process, precipitate as sodium salts in the distillation column, causing the column to clog (Patent Document 1). Tower clogging makes the operation of the distillation column unstable, ultimately requiring the plant to be shut down for cleaning, which impedes the plant's continuous operation. Therefore, the wash water after extraction must be separated from the acid decomposition product.

[0005] The separation of the acid decomposition product from the wash water is carried out by an oil-water separation method, specifically, methods such as static separation, coagulation separation using a filter, and centrifugation.

[0006] In the above-mentioned oil-water separation process, if the oil-water separation ability is insufficient, a portion of the aqueous phase liquid containing salts will be mixed into the oil phase liquid, and the salts to be removed will be carried into the phenol recovery process provided after the washing process. In this case, the carried-in salts will precipitate as sodium salts, etc. in the distillation column, causing blockage of the distillation column.

[0007] The speed of oil-water separation is affected by physical properties such as differences in oil-water density, interfacial tension, and dispersed droplet size, which arise from differences in liquid composition, the presence or absence of surfactants, and mixing and stirring speed, but it has not been fully elucidated how the various impurities and metals generated and mixed in during the various steps of the phenol production process affect oil-water separation. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Publication No. 7-24211 Summary of the Invention [Problem to be solved by the invention]

[0009] An object of the present invention is to provide a method for producing phenol that can achieve better oil-water separation in the oil-water separation step in the production of phenol. [Means for solving the problem]

[0010] The present inventors have noticed that in the washing step of producing phenol, in which wash water is mixed with the oil phase liquid after oil-water separation for washing, oil-water separability deteriorates when the particle size of the water particles dispersed in the mixture of oil phase liquid and wash water is small. They have found that by deliberately allowing water, which was previously thought to be something that should be separated, to be present in the mixture so that it is within a predetermined concentration range, oil-water separability can be improved and oil-water separation processing can be performed more stably over a long period of time in the washing step.

[0011] That is, a first gist of the present invention relates to a method for producing phenol, comprising: a neutralization step of neutralizing an acid decomposition reaction solution of cumene hydroperoxide with an alkali; an oil-aqueous separation step of separating the neutralized reaction solution into an oil phase liquid and an aqueous phase liquid; and a washing step of mixing wash water with the oil phase liquid for washing, and then separating the oil phase liquid and the aqueous phase liquid, wherein the mixture of the oil phase liquid and the wash water in the washing step contains 14.5 mass % or more of water relative to the total mass of the mixture. A second aspect of the present invention relates to a phenol composition for distillation in a cumene process for producing phenol, the phenol composition containing 30% by mass or more and 50% by mass or less of phenol, 11.5% by mass or less of water, and 3.0 ppm by mass or less of an alkali metal. [Effects of the Invention]

[0012] According to the present invention, there is provided a method for producing phenol, which can perform good oil-water separation in the oil-water separation step in the production of phenol. As a result, it is possible to prevent salts, organic acids, etc. contained in the neutralization wash water from being carried over to the oil-water separator and further to downstream purification equipment such as a distillation column, thereby preventing the pipes from clogging, and it is possible to operate the oil-water separator and downstream recovery equipment stably for a long period of time. The present invention also provides a phenol composition for distillation in a cumene process for producing phenol, in which salts, organic acids, and the like are sufficiently reduced, allowing for stable, continuous operation of a distillation column for a long period of time. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is a schematic diagram of an oil-water separation device. [Figure 2] 1 is a graph showing the relationship between the water concentration of the mixed liquid before oil-water separation in the washing step and the water concentration of the oil phase liquid after oil-water separation in Examples 1 to 4 and Comparative Examples 1 to 4. [Figure 3] 1 is a graph showing the relationship between the water concentration of the mixed liquid before oil-water separation in the washing step and the difference in water concentration between the oil phase liquid after oil-water separation and the mixed liquid before oil-water separation in Examples 1 to 4 and Comparative Examples 1 to 4. [Figure 4] 1 is a graph showing the relationship between the water concentration and the sodium concentration in the oil phase liquid after oil-water separation in the washing step in Experimental Examples 1 to 3. DETAILED DESCRIPTION OF THE INVENTION

[0014] The present invention will be described in detail below, but the present invention is not limited to the following description and can be practiced in any modified form without departing from the gist of the present invention.

[0015] Unless otherwise specified, the numerical ranges expressed using "to" in this specification are "to " means a range including the numbers written before and after as the lower and upper limits, and "A to B" means a range including the numbers written before and after as the lower and upper limits, It means greater than or equal to A and less than or equal to B. In this specification, "ppm by mass" refers to "ppm" calculated using mass as the unit, and 1 ppm by mass = 1 × 10 -4 The percentages represent mass %.

[0016] [Phenol manufacturing method] The present invention relates to a process for producing phenol based on the cumene process. The method for producing phenol of the present invention is a method for producing phenol comprising a neutralization step, an oil-water separation step, and a washing step, which will be described later.

[0017] In the method for producing phenol of the present invention, the neutralization step, the oil-water separation step, and the washing step can be repeated in this order any number of times. Furthermore, the method for producing phenol of the present invention may have a recovery step described below after the washing step.

[0018] Furthermore, the phenol production method of the present invention may include, before the neutralization step, a cumene oxidation step described below and a CHP acid decomposition step described below. Furthermore, the phenol production method of the present invention can include a CHP concentration step described below between the oxidation step and the acid decomposition step.

[0019] As a general embodiment of the method for producing phenol, a known method such as the conditions described in JP-A-2017-178826 can be used.

[0020] Each of the above steps will be explained in order below.

[0021] [Cumene oxidation process] The phenol production method of the present invention may include a step of oxidizing cumene to produce CHP before the neutralization step described below. The cumene used in the oxidation of cumene is preferably one that has been purified to 99.5% by weight or more by distillation after reacting benzene with propylene. This may be mixed with cumene recovered from the CHP concentration step described below, or cumene obtained by hydrogenating α-methylstyrene separated in a distillation column from a mixture of phenol, acetone, etc. after phenol synthesis.

[0022] The oxidation reaction of cumene is carried out by blowing a mixed gas containing oxygen and an inert gas at 40°C to 130°C under normal or increased pressure. Examples of the mixed gas include air and air with an increased or decreased oxygen concentration, with air with an increased oxygen concentration being preferred. The oxidation reactor may be one in which the reaction is carried out in a single stage or in multiple stages of two or more stages. In the latter case, an additional mixed gas containing oxygen and an inert gas is usually supplied at each stage. When α-methylstyrene is one of the desired products, conditions suitable for the plant can be selected so that the desired amount of dimethylbenzyl alcohol is produced during the oxidation reaction. The above-mentioned oxidation reaction of cumene yields a cumene solution containing 10 to 40 wt % of CHP.

[0023] [CHP concentration process] The phenol production method of the present invention may include a CHP concentration step in which the cumene solution containing CHP obtained in the oxidation step is concentrated after the above-mentioned cumene oxidation step and before the neutralization step described below, or before the CHP acid decomposition step described below which is carried out before the neutralization step described below. The cumene solution obtained in the above-described cumene oxidation step is concentrated to a CHP concentration of preferably 65% ​​by weight or more, more preferably 80% by weight or more, and more preferably 80% by weight to 90% by weight. Because CHP undergoes a violent cleavage reaction at high temperatures or in the presence of a catalyst, a concentration of 90% by weight or less is preferable from a safety standpoint. The method for concentrating the cumene solution is not particularly limited, but it is preferably concentrated under reduced pressure. This vacuum concentration also allows for the degassing of air introduced during the oxidation reaction. The concentrated CHP solution is diluted with acetone and then subjected to the subsequent acid decomposition step.

[0024] [CHP acid decomposition process] The phenol production method of the present invention can include, after the above-mentioned cumene oxidation step or the CHP concentration step and before the neutralization step described below, a CHP acid decomposition step in which the CHP-containing cumene solution obtained in the oxidation step or the concentration step is decomposed in the presence of an acid catalyst to produce a solution containing phenol and acetone. Specifically, in the cumene solution containing CHP obtained in the concentration step, a cleavage reaction of CHP is caused in the presence of an acid catalyst to obtain a mixture containing phenol, acetone, α-methylstyrene resulting from the aforementioned dimethylbenzyl alcohol, and other by-products. The acid catalyst includes sulfuric acid.

[0025] The acid decomposition reaction of CHP is usually carried out under conditions of a reaction temperature of 60° C. to 90° C. The acid decomposition reaction of CHP is an exothermic reaction, and heat is removed. Almost all of the CHP is cleaved to produce phenol and acetone, and by-products include phenol dimers, heavy ends (HE) such as cumylphenol, and acid decomposition products consisting of a mixture of organic acids. That is, the acid decomposition reaction liquid obtained by decomposing CHP using an acid catalyst is a solution containing phenol and acetone, and the solution also contains α-methylstyrene and other by-products, as well as acid decomposition products including HE, organic acids, etc.

[0026] [Neutralization process] The method for producing phenol of the present invention includes a neutralization step of neutralizing the acid decomposition reaction solution of CHP with an alkali. One embodiment of the neutralization step in the present invention includes a step of neutralizing with an alkali the acid decomposition reaction solution obtained by decomposing CHP in the presence of an acid catalyst in the above-mentioned CHP acid decomposition step, and washing the solution (hereinafter simply referred to as "neutralizing with an alkali"). The neutralization wash water used in neutralizing with an alkali may be an aqueous alkali solution. In the neutralization step, a solution containing phenol and acetone is contacted multiple times with neutralization wash water such as an alkaline aqueous solution. This neutralizes the acid catalyst, such as sulfuric acid, used in the acid decomposition of CHP to obtain a neutralization salt. The neutralization salt, along with organic acids and other by-products from the cumene oxidation step and the CHP acid decomposition step, are then transferred to the neutralization wash water and extracted. The contact between the solution containing phenol and acetone and the neutralization wash water is preferably carried out countercurrently and in multiple stages. These treatments in the neutralization step can be carried out using a known mixing device, such as a line mixer.

[0027] The neutralizing agent used in the neutralization with an alkaline aqueous solution may be an aqueous solution of ammonia, an aqueous solution of a basic compound containing an alkali metal or alkaline earth metal, or an anion exchange resin. Among these, an aqueous solution of a sodium-containing basic compound such as sodium phenolate, sodium hydroxide, or sodium carbonate is preferably used. The sodium-containing basic compound in this aqueous solution is preferably added in an amount such that the pH of the aqueous phase after neutralization is about 6.

[0028] [Oil / water separation process] The method for producing phenol of the present invention includes an oil-aqueous separation step of separating the reaction liquid neutralized in the neutralization step into an oil phase liquid and an aqueous phase liquid. The mixture of the acid decomposition product after neutralization and washing and the neutralization washing water obtained in the neutralization step is separated into an aqueous phase and an oil phase liquid (organic phase) using an oil-water separator, and the oil phase liquid is obtained by removing the aqueous phase. Note that when neutralization is performed using an alkali metal-containing basic compound, some of the phenol becomes a salt with the alkali metal (sodium phenate, etc.) and migrates to the aqueous phase, resulting in a decrease in phenol yield. Therefore, it is preferable to add a salt such as sodium sulfate to the aqueous phase to prevent the phenol in the oil phase liquid from migrating to the aqueous phase. Furthermore, these treatments in the oil-water separation step can be carried out using a known oil-water separation device such as a static separation tank.

[0029] [Cleaning process] The washing step in the present invention involves mixing wash water (hereinafter also referred to as "wash water") with the oil phase liquid obtained in the oil-aqueous separation step to wash the oil, and then separating the oil phase liquid and the aqueous phase liquid (hereinafter referred to as "oil-aqueous separation in the washing step"). More specifically, by mixing wash water under predetermined conditions with the oil phase liquid containing salts obtained in the oil-aqueous separation step to wash the oil, the oil can be efficiently separated into the oil phase liquid and the aqueous phase liquid containing salts extracted from the oil phase, and the salts contained in the oil phase can be efficiently reduced or removed.

[0030] The acid decomposition step of CHP is preferably carried out using sulfuric acid as described above, and the sulfuric acid used is converted to Glauber's salt (sodium sulfate decahydrate) in the neutralization step. The oil phase liquid separated in the oil-water separation step contains neutralized salts such as Glauber's salt, so the oil phase liquid is further washed to remove them.

[0031] In the present invention, the wash water is used so that the mixed liquid of the oil phase liquid and the wash water contains 14.5 mass % or more of water relative to the total mass of the mixed liquid. That is, in the present invention, water, which has previously been considered to be something that should be separated, is intentionally contained in the mixed liquid at a predetermined concentration or more, thereby making it possible to improve oil-water separability as described above.

[0032] In the oil phase liquid washing step, the greater the water content, the more the wash water droplets dispersed in the oil phase liquid tend to aggregate and the larger the particle size, and as a result, from the viewpoint of improving oil-water separability after oil phase liquid washing, the lower limit of the water content in the mixed liquid is 14.5 mass% or more, preferably 15.0 mass% or more, more preferably 15.5 mass% or more, and even more preferably 16.0 mass% or more, relative to the total mass of the mixed liquid. On the other hand, the upper limit of the water content in the mixed liquid is not particularly limited, but from the viewpoint of reducing the amount of wastewater after washing, it is preferably 30.0 mass% or less, more preferably 25.0 mass% or less, and even more preferably 20.0 mass% or less, relative to the total mass of the mixed liquid.

[0033] The upper and lower limits can be combined in any desired manner. For example, the water content in the mixture of the oil phase liquid and the wash water is 14.5% by mass or more and 30.0% by mass or less, preferably 15.0% by mass or more and 25.0% by mass or less, and more preferably 15.5% by mass or more and 20.0% by mass or less, based on the total mass of the mixture.

[0034] The oil phase liquid may be washed using a mixer such as a line mixer and an oil-water separator such as a static separator tank, similar to the apparatus used for neutralization, or may be washed using an extraction separator such as a coalescer. The aqueous phase obtained after washing with the oil phase liquid may be used as wash water in the neutralization washing step described above. This allows the recovery of phenol that has migrated to the aqueous phase. Among the above-mentioned extraction and separation devices, a coalescer is preferred because of its excellent productivity and economy.

[0035] In the phenol production method of the present invention, by using a coalescer equipped with a filter through which the mixed liquid passes, the mixed liquid can be separated more efficiently into an oil phase liquid and an aqueous phase liquid.

[0036] A specific example of the coalescer is a condenser having the function of condensing water containing hydrophilic impurities and separating it from the oil liquid, as disclosed in Japanese Patent Laid-Open Publication No. 7-24211.

[0037] A coalescer is formed as a condenser that has a filter material (filter) made of carbon fiber, glass fiber, or the like with a roughly uniform density and thickness attached to the outer surface of a perforated cylindrical retaining tube made of metal, synthetic resin, or the like, and one or more elements that have a perforated cylindrical outer tube formed by a metal punch plate or the like attached to the outer surface of this filter material, housed within a casing.

[0038] An embodiment of an oil-water separator (coalescer) that can be used for oil-water separation in the washing step will be described with reference to FIG. Wash water is injected from a wash water supply line 2 provided midway through the oil phase line 1 into the oil phase liquid sent through the neutralization step outlet oil phase line 1, and the oil phase liquid and the wash water are mixed by a known mixing means such as a static mixer 3 provided downstream of the injection port. The mixture of the oil phase liquid and wash water is supplied from the bottom of the coalescer 4 and passes through a plurality of elements 5 arranged inside the coalescer 4. The elements 5 have the function of separating the mixture into an oil phase and an aqueous phase, and are provided with a filter (filtering medium) and an inner cylinder and an outer cylinder for supporting the filter so that the mixture can pass through. More specific aspects of the coalescer 4 and elements 5 are as described above.

[0039] As the mixed liquid passes through the inner cylinder, filter medium, and outer cylinder of element 5 in this order, the aqueous phase components in the mixed liquid are coagulated, precipitate from the surface of the outer cylinder of element 5 to the lower side of coalescer 4, where they are collected and withdrawn from line 7 for withdrawing the aqueous phase liquid after oil-water separation, which is provided at the bottom of coalescer 4. On the other hand, the oil phase liquid from which the aqueous phase components have been removed is withdrawn from a post-oil-water-separation oil phase liquid withdrawal line 6 provided above the coalescer 4 .

[0040] The washing water used for washing the oil phase liquid is not particularly limited, but ion-exchanged water or distilled water can be used. The step of washing the oil phase liquid is carried out for the purpose of removing salts from the oil phase liquid, and the washing water used in the step of washing the oil phase liquid needs to have a lower content of salts such as sodium sulfate than the washing water used in the neutralization step.

[0041] Furthermore, in the method for producing phenol of the present invention, it is preferable that the average particle diameter of the droplets of the wash water dispersed in the oil phase liquid in the mixed liquid is larger than the effective filtration diameter of the filter. By setting the average particle diameter of the droplets to be larger than the effective filtration diameter of the filter, oil-water separation after washing with the oil phase liquid can be improved. The average particle diameter of water droplets can be controlled to be larger than the effective filtration diameter of the filter by adjusting the content of water in the mixed liquid and, optionally, the content of metal atoms such as iron and surfactants.

[0042] Furthermore, in the method for producing phenol of the present invention, the lower limit of the average particle diameter of the droplets of wash water dispersed in the oil phase liquid in the mixed liquid is preferably 5 μm or more, more preferably 10 μm or more, and even more preferably 20 μm or more, because this can further improve oil-water separability after oil phase liquid washing. On the other hand, the upper limit of the average particle diameter of the droplets is not particularly limited, but is usually 1 mm or less, preferably 500 μm or less, and more preferably 200 μm or less. The average particle diameter of the water droplets can be controlled by adjusting the content of water in the mixed liquid, the conditions of the line mixer, and optionally the content of metal atoms such as iron and surfactant. The average particle diameter of the wash water droplets dispersed in the oil phase liquid can be measured by taking an enlarged photograph of the liquid collected on a hole slide glass using a microscope, measuring the diameter of each droplet, and then dividing the total droplet diameter by the number of droplets measured.

[0043] When the average particle diameter of the wash water droplets dispersed in the oil phase liquid in the mixed liquid is within the above-mentioned preferred range, the effective filtration diameter of the filter is preferably about 1 to 50 μm, particularly about 5 to 15 μm.

[0044] Furthermore, in the phenol production method of the present invention, it is preferable that the oil phase liquid separated and recovered in the washing step contains 30% by mass or more and 50% by mass or less of phenol, and has a water content of 11.5% by mass or less and an alkali metal content of 2.0 ppm by mass or less, relative to the total mass of the oil phase liquid.

[0045] Here, the term "alkali metal" refers to an alkali metal belonging to Group 1 of the periodic table, as described below, and specific examples include sodium and potassium, with sodium being preferred.

[0046] If the phenol content in the oil phase liquid separated in the washing step is 30% by mass or more, the amount of energy consumed when distilling the washed oil phase liquid to recover the phenol in the recovery step described below can be reduced. The phenol content in the oil phase liquid separated in the washing step is preferably 35% by mass or more. On the other hand, if the phenol content is 50% by mass or less, the amount of energy consumed in the oil-aqueous separation step or the washing step can be reduced. The phenol content in the oil phase liquid separated in the washing step is preferably 45% by mass or less. The content of phenol in the oil phase liquid separated in the washing step can be controlled by appropriately adjusting known production conditions in the oil-aqueous separation step, washing step or acid decomposition step. The content of phenol in the oil phase liquid separated in the washing step is measured by the method described in the Examples section below.

[0047] If the alkali metal content in the oil phase liquid separated in the washing step is 3.0 ppm by mass or less, when the washed oil phase liquid is distilled to recover phenol in the recovery step described below, the alkali metal can be prevented from precipitating as an alkali metal salt in the distillation column and clogging the column. The alkali metal content is more preferably 2.5 ppm by mass or less, and even more preferably 2.0 ppm by mass or less. On the other hand, there is no particular limitation on the lower limit of the alkali metal content, and it is preferable that the alkali metal is substantially free of alkali metal. The alkali metal content in the oil phase liquid separated in the washing step can be controlled by appropriately adjusting known production conditions in the oil-aqueous separation step or the washing step, or the water content in the oil phase liquid described below. The content of alkali metal in the oil phase liquid separated in the washing step is measured by the method described in the Examples section below.

[0048] If the water content in the oil phase liquid separated in the washing step is 11.5 mass% or less, the alkali metal content in the oil phase liquid can be reduced to 3.0 mass ppm or less. This prevents the alkali metal from precipitating as an alkali metal salt in the distillation column and clogging the column when the washed oil phase liquid is distilled to recover phenol in the recovery step described below. The water content is more preferably 11.2 mass% or less, and even more preferably 11.0 mass% or less. On the other hand, there is no particular lower limit for the water content, and it is preferable that the oil phase liquid is substantially free of water. The water content in the oil phase liquid separated in the washing step can be controlled by appropriately adjusting known production conditions in the oil-water separation step or washing step. The water content in the oil phase liquid separated in the washing step is measured by the method described in the Examples section below.

[0049] As described above, the phenol composition obtained by the phenol production method of the present invention contains 30% by mass or more and 50% by mass or less, and preferably 35% by mass or more and 45% by mass or less of phenol, 11.5% by mass or less, preferably 11.2% by mass or less, and more preferably 11.0% by mass or less of water, and 3.0 ppm by mass or less, preferably 2.5 ppm by mass or less, more preferably 2.0% by mass or less of alkali metal, and most preferably contains no alkali metal, and can be suitably used as a composition for distillation in a phenol production process using the cumene method.

[0050] In the phenol production method of the present invention, the lower limit of the content of metal elements, excluding alkali metals belonging to Group 1 of the periodic table (hereinafter simply referred to as "alkali metals belonging to Group 1"), contained in the mixed solution at the inlet of the oil phase liquid washing step, consisting of the oil phase liquid discharged from the outlet of the neutralization step and the wash water used to wash the oil phase liquid, is not particularly limited, but from the viewpoint of improving oil-water separability after washing the oil phase liquid in the oil phase liquid washing step, it is preferably 0.1 mass ppm or more, more preferably 0.2 mass ppm or more, and even more preferably 0.5 mass ppm or more, relative to the total mass of the mixed solution. On the other hand, the upper limit of the content of metal elements, excluding alkali metals belonging to Group 1, in the mixed solution is not particularly limited, but from the viewpoint of preventing clogging due to precipitation of metal salts in the oil phase liquid washing step and subsequent steps, it is preferably 25 mass ppm or less, more preferably 3 mass ppm or less, and even more preferably 2 mass ppm or less, relative to the total mass of the mixed solution.

[0051] The upper and lower limits can be combined in any desired manner. For example, the content of metal elements excluding alkali metals belonging to Group 1 in the mixed solution is 0.1 mass ppm to 25 mass ppm, preferably 0.2 mass ppm to 3 mass ppm, and more preferably 0.5 mass ppm to 2 mass ppm, relative to the total mass of the mixed solution.

[0052] The reason for excluding the content of alkali metals belonging to Group 1 from the content of metal elements is that when alkali metals belonging to Group 1, such as sodium, are present, oil-water separability deteriorates, and therefore the content of metal elements excluding alkali metals belonging to Group 1 is important for improving oil-water separability.

[0053] A method for controlling the content of metal elements excluding alkali metals belonging to Group 1 includes a method in which washing water containing metal elements excluding alkali metals belonging to Group 1 is prepared in advance, and in the washing step, the washing water is mixed with the oil phase liquid so that the content of the metal elements in the mixture of the oil phase liquid and the washing water is within the range of 0.1 ppm by mass or more and 25 ppm by mass or less.

[0054] Alternatively, methods for controlling the content of metal elements excluding alkali metals belonging to Group 1 include known methods such as adding eluted metal by placing a sacrificial metal material in an intermediate tank or the like installed between processes.

[0055] The alkali metals belonging to Group 1 are not particularly limited, but examples include lithium, sodium, potassium, rubidium, etc. Among these, sodium and potassium are preferred.

[0056] Metal elements other than alkali metals belonging to Group 1 are not particularly limited, but include typical metals belonging to Periods 4 and 5 of the periodic table. From the viewpoint of ease of handling, iron, copper, and zinc can be mentioned. Among them, iron is preferred.

[0057] If an alkali metal belonging to Group 1, such as sodium, and an organic acid coexist in the oil phase liquid washing step, the oil-water separability after oil phase liquid washing deteriorates. Therefore, in the present invention, it is preferable to set the concentration of at least one of an alkali metal belonging to Group 1, such as sodium, and an organic acid in a mixed liquid at the inlet of the oil phase liquid washing step, which is made of the oil phase liquid discharged from the outlet of the neutralization step and the washing water used to wash the oil phase liquid, to a predetermined value or less.

[0058] The concentration of the alkali metal belonging to Group 1, such as sodium, in the mixed solution is not particularly limited, but is preferably 250 ppm by mass or less, and more preferably 100 ppm by mass or less, relative to the total mass of the mixed solution.

[0059] Methods for reducing the concentration of alkali metals belonging to Group 1, such as sodium, include lowering the pH by adding acid (preferably sulfuric acid) to the wash water in the neutralization wash process, and increasing the washing efficiency by using multiple stages of oil-water separation equipment.

[0060] The concentration of the organic acid in the mixed solution is not particularly limited, but is preferably 520 ppm by mass or less, more preferably 100 ppm by mass or less, relative to the total mass of the mixed solution. The organic acid referred to here includes acids such as formic acid, acetic acid, and oxalic acid, which are by-produced in the cumene oxidation reaction. The sulfuric acid concentration in the mixed solution is not particularly limited, but from the viewpoint of reducing the concentration of sodium sulfate contained in the washing water, it is preferably 50 ppm by mass or less, and more preferably 20 ppm by mass or less, relative to the total mass of the mixed solution.

[0061] Methods for reducing the organic acid concentration include increasing the pH by adding alkalis to the wash water in the neutralization step, increasing the washing efficiency by using multi-stage wash oil-water separation equipment, etc. The alkalis to be added can be the same as those used in the alkaline wash water in the neutralization step described above.

[0062] [Recovery process] The method for producing phenol of the present invention may include, after the above-mentioned washing step, a recovery step of distilling the oil phase liquid after washing to recover phenol. In the recovery process, the mixture containing phenol, acetone, α-methylstyrene, and heavy ends (HE) on the oil phase liquid side is separated into each component by distillation.

[0063] Regarding distillation, known methods can be used, such as the conditions described in JP-A-2015-178476 and JP-A-2015-182986.

[0064] The number of distillations and the number of distillations to extract each component can be determined arbitrarily. Typically, the first distillation targets light components, particularly acetone, and removes water and unreacted cumene. The second distillation removes phenol and α-methylstyrene. The remaining product is called heavy ends (HE), and the distillate is then subjected to a third distillation to separate phenol and α-methylstyrene. Alternatively, the first distillation targets acetone and α-methylstyrene, and removes water and unreacted cumene. The second distillation separates phenol and HE. Separating the acetone and α-methylstyrene from the first distillation is also possible. In either case, more distillations than the number of target products are required, and the number of distillations is increased to further improve purity. Extractive distillation, in which an appropriate solvent is added to the distillate as needed, can also be performed.

[0065] After distillation, phenol of the desired purity is obtained as the product. [Example]

[0066] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. In these examples, the conditions in the washing step of the phenol production method were changed to confirm the effects of the method of the present invention.

[0067] The liquid obtained by neutralizing the acid decomposition liquid from the phenol production process and separating the oil and water (hereinafter referred to as the "neutralization process outlet liquid") was used as the raw material, and the neutralization process outlet liquid was washed using the washing and oil-water separation device shown in Figure 1.

[0068] The composition of the outlet liquid from the neutralization step was analyzed and found to be as follows: (Composition of oil phase liquid before oil-water separation) Phenol 40% by mass Acetone 32% by mass Cumene 10% by mass α-methylstyrene 5% by mass Water 11% by mass Sodium 10 ppm by mass Sulfuric acid 1 mass ppm Formic acid 150 ppm by mass Acetic acid 100 ppm by mass Other ingredients: 2% by mass

[0069] The contents of phenol, acetone, cumene, and α-methylstyrene were measured by gas chromatography (apparatus name: Agilent 7890A, manufactured by Agilent). The same procedure was followed in the following experimental examples. <Measurement conditions> Column: TC-FFAP, length 60 m, diameter 0.25 mm, film thickness 0.25 μm (Agilent) Carrier gas: Helium 40cm / sec Detector: Hydrogen flame ionization type

[0070] The water concentration was determined by the Karl Fischer reagent volumetric titration method using a moisture meter (product name: CA-200, manufactured by Nitto Seiko Analytech Co., Ltd.). The Karl Fischer moisture measurement reagents used were Aquamicron® Titrant SS-Z 3 mg (manufactured by Mitsubishi Chemical Corporation) and Aquamicron® Dehydrating Solvent KTX (for ketones, non-pyridine / chloroform) (manufactured by Mitsubishi Chemical Corporation). The same was carried out in the following experimental examples.

[0071] The sodium content was measured by mixing the same volume of 0.06 mol / L nitric acid aqueous solution with the sample oil phase liquid, stirring, and separating the oil and water twice to extract sodium into the nitric acid aqueous solution, and then measuring this nitric acid aqueous solution using an ion chromatography measuring device (Device name: Basic 883 IC plus, manufactured by Metrohm) under the conditions described below. The same procedure was followed in the following experimental examples. <Measurement conditions> Column: Metrosep C6-150 / 4.0 (Metrohm) Eluent: 1.7mmol / L nitric acid, 1.7mmol / L dipicolinic acid mixed aqueous solution Detection method: Electrical conductivity

[0072] The sulfuric acid content was measured by mixing and stirring the same volume of 0.1 mol / L aqueous sodium hydroxide solution with the sample oil phase liquid, and separating the oil and water, twice to extract the sulfuric acid into the aqueous sodium hydroxide solution. This aqueous sodium hydroxide solution was then measured using an ion chromatography measuring device (Device name: Basic 883 IC plus, manufactured by Metrohm) under the conditions described below. The same was carried out in the following experimental examples. <Measurement conditions> Column: TSKgel super IC-AZ (Tosoh Corporation) Eluent: 1.9mmol / L sodium bicarbonate, 3.2mmol / L sodium carbonate mixed aqueous solution Detection method: Electrical conductivity, suppressor method

[0073] The content ratios of formic acid and acetic acid were measured by mixing and stirring the same volume of 0.1 mol / L aqueous sodium hydroxide solution with the sample oil phase liquid, and separating the oil and water, twice to extract the formic acid and acetic acid into the aqueous sodium hydroxide solution. This aqueous sodium hydroxide solution was then measured using an ion chromatography measuring device (device name: IC-2010, manufactured by Tosoh Corporation) with a post-column pH buffering ion exclusion method under the conditions described below. The same was carried out in the following experimental examples. <Measurement conditions> Column: Shim-pack SCR-102H (Shimadzu Corporation) x 2 Eluent: 5mmol / L p-toluenesulfonic acid aqueous solution Buffer: 5mmol / L p-toluenesulfonic acid, 20mmol / L Bis-Tris, 0.1mmol / L 4H (EDTA·free acid) mixed aqueous solution Detection method: Electrical conductivity

[0074] [Oil-water separation conditions] In the examples and comparative examples, an oil-water separator shown in Figure 1 was used. This oil-water separator had an internal volume of 44.77 m 3The system is composed of a coalescer 4 with an inner diameter of 3.8 m, a static mixer 3, and a liquid feed pump (not shown). The coalescer 4 has elements 5 equipped with carbon fiber filters with an effective filtration diameter of 15 μm. Although not shown in FIG. 1, the coalescer 4 of this example has 235 elements 5.

[0075] [Example 1] Using the oil-water separator shown in Figure 1, oil-water separation was carried out according to the following procedure, and the water concentration of the process liquid before and after oil-water separation was measured. First, wash water was injected from a wash water supply line 2 provided in the middle of the neutralization step outlet oil phase line 1 into the neutralization step outlet liquid of the above composition, and a mixed liquid of the oil phase liquid and wash water was obtained by a static mixer 3. The resulting mixed liquid was supplied to a coalescer 4 and passed through an element 5 to cause oil-water separation, and the oil phase liquid after oil-water separation was obtained from a post-oil-water separation aqueous phase liquid withdrawal line 7. The post-oil-water separation aqueous phase liquid that had settled in the coalescer 4 was appropriately withdrawn from a post-oil-water separation aqueous phase liquid withdrawal line 7 within a range in which the oil-water interface did not exceed 40% of the height from the bottom to the top of the coalescer. The water concentration of the mixed liquid collected near the inlet of the coalescer 4 (hereinafter referred to as "water concentration before oil phase separation") and the water concentration of the oil phase liquid in the oil phase liquid withdrawal line 6 after oil-aqueous separation (hereinafter referred to as "water concentration of the oil phase liquid after oil phase separation") were measured. In this Example 1, the amount of oil phase liquid fed before oil-water separation and the amount of cleaning water injected from the cleaning water supply line 2 were controlled so that the water concentration before oil phase separation was 15.0 mass %.

[0076] When the mixed liquid is supplied to the coalescer 4, the flow rate of the mixed liquid near the inlet of the coalescer 4 (unit: m 3 The linear velocity of the mixed liquid passing through the element, calculated by dividing the flow rate by the surface area of ​​the element 5, was controlled to be as shown in Table 1.

[0077] [Examples 2 to 4, Comparative Examples 1 to 4] An oil-water separation experiment was carried out under the same conditions as in Example 1, except that the amount of oil phase liquid fed before oil-water separation and the amount of wash water injected from the wash water supply line 2 were controlled so that the water concentration before oil-water separation would be as shown in Table 1. The evaluation results are shown in Table 1.

[0078] In Example 3 and Comparative Example 2, the average particle diameters of the water droplets dispersed in the mixed liquid before oil-water separation, measured using the above-mentioned method, were 34.2 μm and 20.8 μm, respectively, 1 minute after sample collection. Example 3, which had a higher water concentration than Comparative Example 2, had a larger average particle diameter.

[0079] FIG. 2 shows the relationship between the water concentration of the mixed liquid before oil-water separation in the washing step and the water concentration of the oil phase liquid after oil-water separation, obtained from Examples 1 to 4 and Comparative Examples 1 to 4. FIG. 3 shows the relationship between the water concentration of the mixed liquid before oil-water separation in the washing process and the difference in water concentration between the oil phase liquid after oil-water separation and the mixed liquid before oil-water separation, obtained from Examples 1 to 4 and Comparative Examples 1 to 4.

[0080] [Table 1]

[0081] [Experimental Example 1] Oil-water separation was carried out under the same conditions as in Example 1, except that the water concentration in the mixture of the oil phase liquid and wash water in the washing step was set to the value shown in Table 2, and the water and sodium contents in the oil phase liquid separated in the washing step were measured. The measurement results are shown in Table 2. The phenol content in the oil phase liquid was measured and found to be 38.5 to 40.3 mass%. The relationship between the water and sodium contents in the oil phase liquid is shown in Figure 4.

[0082] [Experimental Example 2] The line for the mixture of oil phase liquid and washing water in Experimental Example 1 was branched off, and a 0.013 m 3Oil-water separation was carried out in the same manner as in Example 1, except that a coalescer having a single element, an inner diameter of 0.20 m, and a linear velocity through the element was controlled as shown in Table 2. The water and sodium contents in the separated oil phase liquid were measured. The measurement results are shown in Table 2. The relationship between the water and sodium contents in the oil phase liquid is also shown in Figure 4.

[0083] [Experimental Example 3] Oil-water separation was carried out under the same conditions as in Experimental Example 2, except that the line for the mixed liquid of oil phase liquid and wash water was branched off and the element was changed to one made of a mixture of carbon fiber and glass fiber with an effective filtration diameter of 5 μm. The water and sodium contents in the separated oil phase liquid were measured. The measurement results are shown in Table 2. The relationship between the water and sodium contents in the oil phase liquid is also shown in Figure 4.

[0084] [Table 2]

[0085] [Consideration] In Examples 1 to 4, the water concentration in the oil phase after oil-water separation was low. On the other hand, in Comparative Examples 1 to 4, the water concentration in the mixed liquid was low, and therefore the water concentration in the oil phase after oil-water separation was high. 2 and 3, it can be seen that the higher the water concentration in the mixed liquid, the lower the water concentration in the oil phase after oil-water separation tends to be.

[0086] From Experimental Examples 1 to 3, it is clear that the water and sodium content in the oil phase liquid separated in the washing step can be controlled by controlling the water concentration in the mixed liquid in the washing step. Furthermore, Figure 4 shows that there is a correlation between the water and sodium contents in the oil phase liquid separated in the washing process, and that by controlling the water content to 11.5 mass% or less, the sodium content can be controlled to 3.0 mass ppm or less. A phenol composition having such a composition can be suitably used as a composition for distillation in a phenol production process using the cumene process, since it can prevent sodium salts from precipitating in a distillation column and clogging the column.

[0087] From the above results, in the production of phenol having a neutralization step, an oil-aqueous separation step, and an oil phase liquid washing step as defined in claim 1, it is expected that good oil-aqueous separability can be achieved when the water concentration in the mixture of the oil phase liquid and wash water at the inlet of the washing step is 14.5 mass% or more. Phenol is consumed in large quantities as a raw material for, for example, epoxy resins, polycarbonate resins, phenolic resins, and polyester resins, and is therefore produced in large quantities on an industrial scale of, for example, 100,000 tons per year or more. Therefore, in the production of phenol, improving oil-water separability even slightly, for example, reducing the water concentration in the oil phase brought into the distillation column by even 1%, is industrially important from the viewpoint of reducing production costs by reducing the energy required for heating in the distillation column and suppressing the precipitation of salts dissolved in the free water in the oil phase. [Explanation of symbols]

[0088] 1. Neutralization process outlet oil phase line 2 Cleaning water supply line 3. Static Mixer 4. Coalescer 5 Elements 6 Oil phase liquid extraction line after oil / water separation 7 Aqueous phase liquid extraction line after oil / water separation

Claims

1. a neutralization step of neutralizing the acid decomposition reaction solution of cumene hydroperoxide with an alkali; an oil-water separation step of separating the neutralized reaction liquid into an oil phase liquid and an aqueous phase liquid; a washing step of mixing wash water with the oil phase liquid for washing, and then separating the oil phase liquid and the aqueous phase liquid; In a method for producing phenol, The method for producing phenol, wherein the mixture of the oil phase liquid and the wash water in the washing step contains 14.5 mass % or more and 30 mass % or less of water based on the total mass of the mixture.

2. 2. The method for producing phenol according to claim 1, wherein the washing step comprises separating the mixed liquid into an oil phase liquid and an aqueous phase liquid using a coalescer equipped with a filter through which the mixed liquid passes.

3. 3. The method for producing phenol according to claim 2, wherein in the mixed liquid, the average particle diameter of the wash water droplets dispersed in the oil phase liquid is larger than the effective filtration diameter of the filter.

4. 4. The method for producing phenol according to claim 3, wherein the droplets have an average particle diameter of 5 μm or more.

5. The method for producing phenol according to any one of claims 2 to 4, wherein the coalescer has a filter having an effective filtration diameter of 1 µm or more and 30 µm or less in a flow path for the mixed liquid.

6. The method for producing phenol according to any one of claims 1 to 5, further comprising an oxidation step of oxidizing cumene to produce cumene hydroperoxide before the neutralization step.

7. The method for producing phenol according to any one of claims 1 to 6, further comprising, after the washing step, a recovery step of distilling the oil phase liquid after washing to recover phenol.

8. The method for producing phenol according to any one of claims 1 to 7, wherein the oil phase liquid separated in the washing step contains 11.5 mass% or less of water and 3.0 mass ppm or less of alkali metals, relative to the total mass of the oil phase liquid.

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