JP7771765B2 - Phenol production method and phenol composition - Google Patents

Description

The present invention relates to a method for producing phenol and a phenol composition.

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

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 can act as a catalyst for producing heavy products when heated in the subsequent recovery process. Therefore, in a neutralization and washing process prior to the recovery process, the acid decomposition product is brought into contact with wash water containing added alkali such as sodium carbonate, and the acid is extracted and removed into the wash water. At the same time, the neutralization and washing process also extracts and removes organic acids that are produced as impurities in the oxidation process for producing CHP.

The wash water that comes into contact with this acid decomposition product contains the extracted acid and salts, and if this is carried over to the recovery process, it will 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 hinders the plant's continuous operation. For this reason, the wash water after extraction must be separated from the acid decomposition product.

The separation of the acid decomposition products and the wash water is carried out using oil-water separation methods. Specific examples of oil-water separation methods include static separation, coagulation separation using a filter, and centrifugation.

If the oil-water separation process described above is insufficient, some of the aqueous phase liquid containing salts will be mixed into the oil phase liquid, and the salts that should be removed will be carried over to the phenol recovery process that follows the washing process. In this case, the carried-over salts will precipitate as sodium salts and other substances in the distillation column, clogging the column.

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.

Japanese Patent Application Publication No. 7-24211

The objective of the present invention is to provide a method for producing phenol that enables better oil-water separation in the oil-water separation process during phenol production.

The inventors noticed that in the washing process 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 discovered that by intentionally 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 specified concentration range, oil-water separability can be improved, enabling more stable oil-water separation processing over a long period of time in the washing process.

That is, a first gist of the present invention relates to a method for producing phenol, which includes 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 mixed liquid 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 mixed liquid.
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.

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.

FIG. 1 is a schematic diagram of an oil-water separation device. 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. 1 is a graph showing 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 in Examples 1 to 4 and Comparative Examples 1 to 4. 1 is a graph showing the relationship between the water concentration and the sodium concentration of the oil phase liquid after oil-water separation in the washing process in Experimental Examples 1 to 3.

The present invention is described in detail below, but the present invention is not limited to the following description and can be modified and implemented as desired without departing from the spirit of the present invention.

Unless otherwise specified, the numerical ranges expressed using "to" in this specification are "to
" means a range including the numerical values written before and after as the lower and upper limits, and "A to B" means a range including the numerical values written before and after as the lower and upper limits,
It means that it is greater than or equal to A and less than or equal to B.
In this specification, "ppm by mass" refers to "ppm" calculated with the unit being mass, and 1 ppm by mass = 1 x 10 ^-4 mass%.

[Production method of phenol]
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.

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.

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 may include a CHP concentration step described below between the oxidation step and the acid decomposition step.

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

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

[Cumene oxidation process]
The method for producing phenol 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.

The oxidation reaction of cumene is carried out by blowing a mixed gas containing oxygen and an inert gas into the reactor at 40°C to 130°C under atmospheric pressure or under 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, 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% by weight of CHP.

[CHP concentration process]
The phenol production method of the present invention may include a CHP concentration step of concentrating the cumene solution containing CHP obtained in the oxidation step, which is performed after the cumene oxidation step described above and before the neutralization step described below, or before the CHP acid decomposition step described below which is performed 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. CHP undergoes a violent cleavage reaction at high temperatures or in the presence of a catalyst, so a CHP 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. By concentrating under reduced pressure, it is also possible to degas the air blown in during the oxidation reaction. The concentrated CHP solution is diluted with acetone and subjected to the subsequent acid decomposition step.

[CHP acid decomposition process]
The phenol production method of the present invention may 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, and the above-mentioned α-methylstyrene resulting from dimethylbenzyl alcohol, as well as other by-products.
The acid catalyst includes sulfuric acid.

The acid decomposition reaction of CHP is usually carried out at 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 obtained include phenol dimers, heavy oils (HE (heavy ends)) such as cumylphenol, and acid decomposition products comprising 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 contains α-methylstyrene and other by-products, as well as acid decomposition products including HE, organic acids, etc.

[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.

Neutralizing agents used in neutralization with an alkaline aqueous solution include aqueous ammonia solutions, aqueous solutions of basic compounds containing alkali metals or alkaline earth metals, and anion exchange resins. Among these, aqueous solutions of sodium-containing basic compounds such as sodium phenolate, sodium hydroxide, and sodium carbonate are preferred. The sodium-containing basic compound in this aqueous solution is preferably added in an amount that results in a pH of the aqueous phase after neutralization of around 6.

[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 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 with an alkali metal-containing basic compound, a portion of the phenol becomes a salt with the alkali metal (sodium phenate, etc.) and migrates to the aqueous phase, resulting in a decrease in the 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.

[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, a liquid containing oil and an aqueous phase liquid containing salts extracted from the oil phase 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.

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

In the present invention, the wash water is used so that the mixture of the oil phase liquid and the wash water contains 14.5% by mass or more of water relative to the total mass of the mixture. In other words, in the present invention, water, which was previously considered to be something that should be separated, is intentionally included in the mixture at a predetermined concentration or more, thereby improving oil-water separability as described above.

In the oil phase liquid washing process, the higher the water content, the more likely the wash water droplets dispersed in the oil phase liquid will aggregate, resulting in larger particle sizes. 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. Meanwhile, 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 discharged 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.

The above upper and lower limits can be combined in any combination. For example, in the mixture of the oil phase liquid and wash water, the water content 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, relative to the total mass of the mixture.

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.

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

Specific examples of coalescers include a condenser that has 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.

A coalescer is primarily a condenser that contains one or more elements fitted inside a casing, each element having a perforated cylindrical outer cylinder made of metal, synthetic resin, etc., fitted with a filter material (filter) made of carbon fiber, glass fiber, etc. with a roughly uniform density and thickness, attached to the outer surface of the filter material. These elements have a perforated cylindrical outer cylinder formed from a metal punch plate, etc.

An embodiment of an oil-water separator (coalescer) that can be used for oil-water separation in the cleaning process 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.

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, settle from the surface of the outer cylinder of element 5 to the lower side of coalescer 4, and 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 .

The wash water used to wash the oil phase liquid is not particularly limited, but ion-exchanged water or distilled water can be used. The oil phase liquid washing process is carried out for the purpose of removing salts from the oil phase liquid, and the wash water used in the oil phase liquid washing process must contain less salts such as sodium sulfate than the wash water used in the neutralization process.

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.

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.

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 1 to 50 μm, and particularly preferably 5 to 15 μm.

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, relative to the total mass of the oil phase liquid, and that the water content is 11.5% by mass or less and the alkali metal content is 2.0 ppm by mass or less.

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

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.

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, the lower limit of the alkali metal content is not particularly limited, 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.

If the water content in the oil phase liquid separated in the washing step is 11.5% by mass or less, the alkali metal content in the oil phase liquid can be reduced to 3.0 ppm by mass 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% by mass or less, and even more preferably 11.0% by mass or less. On the other hand, the lower limit of the water content is not particularly limited, 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.

From the 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, preferably 35% by mass or more and 45% by mass or less, water 11.5% by mass or less, preferably 11.2% by mass or less, more preferably 11.0% by mass or less, alkali metals 3.0 ppm by mass or less, preferably 2.5 ppm by mass or less, more preferably 2.0% by mass or less, and most preferably no alkali metals, and can be suitably used as a composition for distillation in a phenol production process using the cumene process.

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 liquid 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 achieving good oil-water separability after washing the oil phase liquid in the oil phase liquid washing step, it is preferably 0.1 ppm by mass or more, more preferably 0.2 ppm by mass or more, and even more preferably 0.5 ppm by mass or more, relative to the total mass of the mixed liquid. On the other hand, the upper limit of the content of metal elements, excluding alkali metals belonging to Group 1, in the mixed liquid is not particularly limited, but from the viewpoint of preventing clogging due to precipitation of metal salts after the oil phase liquid washing step, it is preferably 25 ppm by mass or less, more preferably 3 ppm by mass or less, and even more preferably 2 ppm by mass or less, relative to the total mass of the mixed liquid.

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

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

One method for controlling the content of metal elements excluding alkali metals belonging to Group 1 is to prepare wash water containing metal elements excluding alkali metals belonging to Group 1 in advance, and then mix the wash water with the oil phase liquid in the washing step so that the content of the metal elements in the mixture of the oil phase liquid and wash water is within the range of 0.1 ppm by mass or more and 25 ppm by mass or less.

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

Alkali metals belonging to Group 1 include, but are not limited to, lithium, sodium, potassium, rubidium, etc. Of these, sodium and potassium are preferred.

Metal elements excluding alkali metals belonging to Group 1 include, but are not limited to, typical metals belonging to the fourth and fifth periods of the periodic table. From the viewpoint of ease of handling, iron, copper, and zinc are preferred. Of these, iron is preferred.

If alkali metals belonging to Group 1, such as sodium, and organic acids coexist in the oil phase liquid washing process, the oil-water separability after oil phase liquid washing will deteriorate. Therefore, in the present invention, it is preferable to set the concentration of at least one of alkali metals belonging to Group 1, such as sodium, and organic acids in the mixed liquid at the inlet of the oil phase liquid washing process, which is made up of the oil phase liquid discharged from the outlet of the neutralization process and the washing water used to wash the oil phase liquid, to a predetermined value or less.

The concentration of alkali metals 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.

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.

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 cleaning 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.

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

[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 step, the mixture containing phenol, acetone, α-methylstyrene, and heavy ends (HE) on the oil phase liquid side is separated into each component by distillation.

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

The number of distillations and which components are extracted in which distillation rounds can be set at will, but typically, the first distillation targets light components, particularly acetone, and removes water and unreacted cumene. The second distillation removes phenol and α-methylstyrene, leaving behind heavy ends (HE). This can then be 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. Of course, the acetone and α-methylstyrene obtained in the first distillation can also be separated separately. In either case, more distillations than the number of target products are required, and the number of distillations can be increased to further improve purity. Extractive distillation, in which an appropriate solvent is added to the distillation as needed, can also be performed.

After distillation, phenol of the desired purity is produced as the product.

The present invention will be explained in more detail below using examples, but the present invention is not limited to these examples. In these examples, the conditions in the washing process of the phenol production method were changed to infer the effects of the method of the present invention.

The liquid obtained by neutralizing and separating oil and water from acid decomposition liquid from the phenol production process (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.

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
Cumen 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

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

The water concentration was determined by the Karl Fischer reagent volumetric titration method using a moisture meter (product name: CA-200 model, manufactured by Nitto Seiko Analytech Co., Ltd.). As the Karl Fischer moisture measurement reagent, Aquamicron (registered trademark) titrant SS-Z 3 mg (manufactured by Mitsubishi Chemical Corporation) and Aquamicron (registered trademark) dehydrating solvent KTX (for ketones, non-pyridine/chloroform) (manufactured by Mitsubishi Chemical Corporation) were used.
The same was carried out in the following experimental examples.

The sodium content was measured by repeating twice the same volume of 0.06 mol/L nitric acid aqueous solution mixed with the sample oil phase liquid and stirring, followed by oil-water separation, 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 (manufactured by Metrohm)
Eluent: 1.7 mmol/L nitric acid, 1.7 mmol/L dipicolinic acid mixed aqueous solution Detection method: Electrical conductivity

The sulfuric acid content was measured by repeating twice the process of 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, thereby extracting sulfuric acid into the aqueous sodium hydroxide solution, and then measuring the content of sulfuric acid in the aqueous sodium hydroxide 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: TSKgel Super IC-AZ (manufactured by Tosoh Corporation)
Eluent: 1.9 mmol/L sodium bicarbonate, 3.2 mmol/L sodium carbonate mixed aqueous solution Detection method: electrical conductivity, suppressor method

The content ratios of formic acid and acetic acid were measured by repeating twice a process in which the same volume of 0.1 mol/L aqueous sodium hydroxide solution was mixed and stirred with the oil phase liquid of the sample, followed by oil-water separation, to extract 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 procedure was followed in the following experimental examples.
<Measurement conditions>
Column: Shim-pack SCR-102H (Shimadzu Corporation) x 2 Eluent: 5 mmol/L p-toluenesulfonic acid aqueous solution Buffer: 5 mmol/L p-toluenesulfonic acid, 20 mmol/L Bis-Tris, 0.1 mmol/L 4H (EDTA-free acid) mixed aqueous solution Detection method: Electrical conductivity

[Oil-water separation conditions]
The oil-water separator shown in Figure 1 was used in the examples and comparative examples. This oil-water separator comprises a coalescer 4 with an internal volume of 44.77 ^m3 and 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 Figure 1, the coalescer 4 of this example has 235 elements 5.

[Example 1]
Using the oil-water separator shown in FIG. 1, oil-water separation was carried out according to the following procedure, and the water concentrations of the process liquid before and after oil-water separation were measured.
First, wash water was injected from a wash water supply line 2 provided midway through 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 sampled near the inlet of the coalescer 4 (hereinafter referred to as the "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 the "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-aqueous 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 %.

When the mixed liquid was supplied to the coalescer 4, the flow rate (unit: ^m3 /hr) of the mixed liquid near the inlet of the coalescer 4 was measured, and the linear velocity of the mixed liquid passing through the element 5, calculated by dividing the flow rate by the surface area of the element 5, was controlled to be as shown in Table 1.

[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.

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

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-aqueous separation in the washing step and the difference in water concentration between the oil phase liquid after oil-aqueous separation and the mixed liquid before oil-aqueous separation, obtained from Examples 1 to 4 and Comparative Examples 1 to 4.

[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 the 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.

[Experimental Example 2]
Oil-water separation was carried out in the same manner as in Example 1, except that the line for the mixed liquid of the oil phase liquid and wash water in Experimental Example 1 was branched, and a coalescer with an internal volume of 0.013 m ³ , an inner diameter of 0.20 m, and one element was used, and the linear speed 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.

[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 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.

[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.

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, from FIG. 4, it can be seen that there is a correlation between the water and sodium contents in the oil phase liquid separated in the washing step, 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.

From the above results, it is expected that 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, 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, for example, at a rate of 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.

1 Neutralization process outlet oil phase line 2 Washing water supply line 3 Static mixer 4 Coalescer 5 Element 6 Oil phase liquid withdrawal line after oil-water separation 7 Water phase liquid withdrawal line after oil-water separation

Claims (8)

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. The method for producing phenol according to claim 1, wherein the washing step includes 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. 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. The method for producing phenol described in claim 3, wherein the droplets have an average particle diameter of 5 μm or more. The method for producing phenol according to any one of claims 2 to 4, wherein the coalescer has a filter with an effective filtration diameter of 1 μm or more and 30 μm or less in the flow path of the mixed liquid. 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. 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. 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.