Method for producing phenol

Abstract

To provide a production method for phenol, enabling oil and water to be successfully separated from each other in an oil-water separation step in the production method for phenol.SOLUTION: A production method for phenol is provided, including the steps of : oxidizing cumene to produce cumene hydroperoxide; decomposing the cumene hydroperoxide in the presence of an acid to produce a solution containing phenol and acetone; neutralizing the solution containing phenol and acetone with an alkali aqueous solution and then performing oil-water separation; and washing an oil-phase solution after oil-water separation with washing water using an oil phase washing apparatus. In the oil phase washing step, a mixed solution of the oil-phase solution and the washing water satisfies at least one of following (1) and (2) at the inlet of the oil phase washing apparatus. (1) The sodium concentration is 250 ppm or less. (2) The organic acid concentration is 520 ppm or less.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a method for producing phenol.

Background Art

[0002] Industrially, phenol is generally produced by the cumene process. The production of phenol by the cumene process includes an oxidation step of oxidizing cumene to produce a reaction solution containing cumene hydroperoxide (hereinafter referred to as CHP), an acid decomposition step of acid-decomposing CHP to produce phenol and acetone, a neutralization and washing step of neutralizing the decomposition product solution and removing salts by washing, and a purification step of separating components other than phenol in the washing solution.

[0003] In the acid decomposition step of the phenol production method by the cumene process, an acid such as sulfuric acid is added to efficiently decompose CHP. If an acid remains in this acid decomposition product, it becomes a catalyst for generating heavy substances by heating in the subsequent purification step. Therefore, washing water containing an alkali such as sodium carbonate is brought into contact with the acid decomposition product in the neutralization and washing step before the purification step, and the acid is extracted and removed into the washing water. Also, in the neutralization and washing step, organic acids generated as impurities in the oxidation step for producing CHP are also extracted and removed at the same time.

[0004] The washing water brought into contact with this acid decomposition product contains the extracted acid and salts. When this is introduced into the purification step, it precipitates as a sodium salt in the distillation column, blocking the column (Patent Document 1). Column blockage makes the operation of the distillation column unstable, and ultimately it is necessary to stop the plant and wash it, which becomes an obstacle to continuous plant operation. For this reason, it is necessary to separate the washing water after extraction from the acid decomposition product.

[0005] The separation of the acid decomposition product and the washing water is oil-water separation, and methods for this oil-water separation include methods such as static separation, coagulation separation by a filter, and centrifugal separation.

[0006] The oil-water separation rate is affected by physical properties such as the difference in liquid composition, the presence or absence of surfactants, the oil-water density difference, interfacial tension, and dispersed droplet diameter caused by differences in mixing and stirring speed. However, the effects of various impurities generated in the various processes of the phenol manufacturing process on oil-water separation have not been fully elucidated.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0008] An object of the present invention is to provide a method for producing phenol that can perform good oil-water separation in the oil-water separation step of the phenol production method.

Means for Solving the Problems

[0009] The present inventor has discovered that when an organic acid and sodium coexist in the oil-water separation step in the phenol production method, the oil-water separation deteriorates, and by setting at least one of the concentrations of the organic acid and sodium below a predetermined value, it has been found that the oil-water separation can be improved. The present invention has been made based on such findings and has the following gist.

[0010] [1] A step of oxidizing cumene to produce cumene hydroperoxide, A step of decomposing cumene hydroperoxide in the presence of an acid to produce a solution containing phenol and acetone, A step of neutralizing the solution containing phenol and acetone with an aqueous alkali solution and then performing oil-water separation, and An oil phase water washing step of washing the oil phase liquid after oil-water separation with washing water using an oil phase water washing device, A method for producing phenol having In the oil phase water washing step, a method for producing phenol, characterized in that the mixed liquid of the oil phase liquid and washing water at the inlet of the oil phase water washing device satisfies at least one of the following (1) and (2). (1) The sodium concentration is 250 ppm or less (2) The organic acid concentration is 520 ppm or less

[0011] [2] The method for producing phenol according to [1], wherein in the oil phase water washing step, the sulfuric acid concentration in the mixed liquid of the oil phase liquid and washing water at the inlet of the oil phase water washing device is 50 ppm or less.

[0012] [3] The method for producing phenol according to [1] or [2], wherein after the oil phase water washing step, the oil phase water is distilled to obtain phenol.

Effect of the Invention

[0013] According to the present invention, oil-water separation in the oil-water separation step of the phenol production method can be performed well. Thereby, blockage due to the introduction of organic acid salts and the like contained in the neutralization washing water into the distillation column can be suppressed, and the equipment can be continuously and stably operated.

Brief Description of the Drawings

[0014]

Figure 1

Embodiments for Carrying Out the Invention

[0015] The description of the constituent elements described below is an example (representative example) of an embodiment of the present invention, and is not limited to these contents.

[0016] The present invention relates to a method for producing phenol based on the cumene process. Each step thereof will be described in order below.

[0017] Regarding the method for producing phenol, known methods such as the conditions described in JP-A-2017-178826 can be used.

[0018] [Oxidation process of cumene] The cumene used for the oxidation of cumene is usually preferably one that is purified to 99.5% by weight or more by reacting benzene and propylene and distillation. To this, cumene recovered from the CHP concentration step described later, or a product obtained by hydrogenating α-methylstyrene separated by a distillation column from a mixture of phenol, acetone, etc. after phenol synthesis to cumene may be mixed.

[0019] The oxidation of cumene is carried out at 40°C to 130°C under normal pressure or under pressure by blowing a mixed gas containing oxygen and an inert gas. Examples of this mixed gas include air and air with an increased or decreased oxygen concentration, among which air with an increased oxygen concentration is preferred. The oxidation reactor may be one that performs the reaction in one stage or one that performs it in two or more multi-stages. In the latter case, usually, a mixed gas containing oxygen and an inert gas is additionally supplied for each stage. When α-methylstyrene is one of the target products, suitable conditions for the plant may be selected so that a desired amount of dimethylbenzyl alcohol is generated during this oxidation reaction.

[0020] [CHP concentration step] By the above-mentioned oxidation reaction of cumene, a cumene solution usually containing 10 to 40% by weight of CHP is obtained. This cumene solution is concentrated so that the CHP concentration is preferably 65% by weight or more, more preferably 80% by weight or more, and more preferably 80% by weight or more and 90% by weight or less. Since CHP undergoes a violent cleavage reaction at a high temperature or in the presence of a catalyst, it is preferably 90% by weight or less from the viewpoint of safety. The concentration method is not particularly limited, but concentration under reduced pressure is preferred. By concentrating under reduced pressure, it is also possible to degas air, etc. blown in during the oxidation reaction. The concentrated CHP solution is diluted with acetone and subjected to the next acid decomposition step.

[0021] [Acid decomposition step of CHP] After the above concentration step, the acid decomposition of CHP is carried out using a catalyst. Specifically, the cleavage reaction of CHP is caused to obtain a mixture of phenol, acetone, and α-methylstyrene and other by-products resulting from the aforementioned dimethylbenzyl alcohol. The catalyst used here is preferably an acid catalyst, and most preferably sulfuric acid.

[0022] The reaction temperature is usually carried out at 60°C to 90°C. The cleavage reaction of CHP is intense and the heat generation during the reaction is intense, so heat removal is carried out. Almost all of the CHP is cleaved into phenol and acetone, but an acid decomposition product consisting of a mixture containing heavy oil components (HE (heavy end)) such as phenol dimers and cumylphenol and organic acids as by-products is obtained.

[0023] [Neutralization washing and oil-water separation step] The acid decomposition products such as phenol, acetone, α-methylstyrene, and HE obtained in the acid decomposition step are neutralized and washed, and then the oil and water are separated. This neutralization washing and oil-water separation can be carried out using a mixing device such as a line mixer and an oil-water separation device such as a static separation tank.

[0024] [Neutralization washing step] In the neutralization washing step, the acid decomposition product and the washing water are brought into contact and separated a plurality of times. Thereby, after neutralizing the acid catalyst such as sulfuric acid used during acid decomposition, the neutral salt and the organic acid by-produced in the oxidation step and the acid decomposition step are transferred (extracted) into the washing water. The contact between the acid decomposition product and the washing water is preferably carried out in a countercurrent and multi-stage manner.

[0025] It is preferable to use an alkaline aqueous solution as the washing water during neutralization washing. As the neutralizing agent used for neutralization with the alkaline aqueous solution, an aqueous solution of ammonia, an aqueous solution of a basic compound containing an alkali metal or an alkaline earth metal, an anion exchange resin, etc. can be used. Among these, an aqueous solution of a sodium-containing basic compound such as sodium phenolate, sodium hydroxide, and 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 becomes about 6.

[0026] <Oil-water separation process> The mixture of the acid decomposition product after neutralization washing and the neutralization washing water is separated into an aqueous phase and an organic phase (oil phase liquid) by an oil-water separator, and the organic phase is obtained by removing the aqueous phase. When neutralized with an alkali metal-containing basic compound, a part of phenol becomes a salt with an alkali metal (such as sodium phenate) and migrates to the aqueous phase side, resulting in a decrease in the phenol yield. Therefore, it is preferable to add salts such as sodium sulfate to the aqueous phase so that the phenol in the organic phase does not migrate to the aqueous phase side.

[0027] [Washing process of organic phase (oil phase liquid)] The above-mentioned acid decomposition process of CHP is preferably carried out using sulfuric acid as described above, and the sulfuric acid used is converted into mirabilite (sodium sulfate decahydrate) by the neutralization washing process. Since the organic phase (oil phase liquid) separated by oil-water separation contains neutral salts such as this mirabilite, the organic phase (oil phase liquid) is further washed with water to remove it.

[0028] The washing of the organic phase may be carried out using a mixing device such as a line mixer and an oil-water separator such as a settling tank in the same manner as the device used for neutralization, or using an extraction separation device such as a coalescer. The aqueous phase after washing the organic phase with water may be used as the washing water in the above-mentioned neutralization washing process, and thereby, the phenol migrated to the aqueous phase side can be recovered.

[0029] The washing water used for washing the organic phase is preferably ion-exchanged water or distilled water. The organic phase washing process is carried out for the purpose of removing salts in the organic phase, and it is necessary to reduce the salts such as sodium sulfate contained in the washing water used compared with the neutralization washing process. The sulfuric acid concentration in the mixed liquid of the oil phase liquid at the outlet of the neutralization washing process and the washing water for washing the organic phase at the inlet of the organic phase washing process is preferably 50 ppm or less, and more preferably 20 ppm or less.

[0030] When sodium and an organic acid coexist in the organic phase water washing process, the oil-water separation after washing the organic phase deteriorates. Therefore, in the present invention, the concentration of at least one of sodium and the organic acid is set to be equal to or lower than a predetermined value.

[0031] Examples of methods for reducing the sodium concentration include lowering the pH by adding an acid (preferably sulfuric acid) to the washing water in the neutralization washing process, and increasing the washing efficiency by multi-staging the oil-water separation equipment. The concentration of sodium in the mixed liquid of the oil phase liquid at the outlet of the neutralization process and the washing water at the inlet of the organic phase water washing process is preferably 250 ppm or less, and more preferably 100 ppm or less.

[0032] Examples of methods for reducing the organic acid concentration include increasing the pH by adding alkalis to the washing water in the neutralization washing process, and increasing the washing efficiency by multi-staging the washing oil-water separation equipment. As the alkalis to be added, those contained in the alkali washing water in the above-described neutralization washing process are preferred. The concentration of the organic acid in the mixed liquid of the oil phase liquid at the outlet of the neutralization process and the washing water at the inlet of the water washing process is preferably 520 ppm or less, and more preferably 100 ppm or less.

[0033] [Distillation process] The mixture containing phenol, acetone, α-methylstyrene, and HE on the organic phase side is separated into respective components by distillation.

[0034] Regarding distillation, known methods can be used, such as the conditions described in JP-A-2015-178476 and JP-A-2015-182986.

[0035] Regarding the number of distillations and which components to extract at which distillation, they can be set arbitrarily. Usually, in the first distillation, light components, especially acetone, are targeted to distill off water and unreacted cumene, etc. In the second distillation, phenol and α-methylstyrene are distilled off, and the remaining is taken as the heavy end (HE). The distillate can be subjected to a third distillation to separate phenol and α-methylstyrene, or in the first distillation, acetone and α-methylstyrene are targeted to distill off water and unreacted cumene, etc., and in the second distillation, phenol and HE are separated. And of course, separately, the acetone and α-methylstyrene obtained in the first distillation can be separated. In any case, more distillations than the number of target substances are required, and to further improve the purity, the number of distillations is also increased. Also, extractive distillation can be performed while adding an appropriate solvent as needed during distillation.

[0036] After distillation, phenol reaching the desired purity is used as the product.

Example

[0037] An experiment simulating the oil-water separation process of the phenol production method was conducted to infer the effect of the method of the present invention.

[0038] [Example 1] Ion-exchanged water, acetone, cumene, α-methylstyrene, and phenol were mixed to obtain the mixed composition liquid of Example 1 in Table 1. For acetone, cumene, α-methylstyrene, and phenol, reagent grade products manufactured by Fujifilm Wako Pure Chemical Industries, Ltd. were used. In addition, formic acid and sodium hydroxide in Examples 2 to 6 and Comparative Example 1 described later are also reagent grade products manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.

[0039] Regarding the obtained mixed composition liquid, oil-water separation was performed using the experimental apparatus shown in Fig. 1, and the water concentration in the obtained oil-phase sample was measured. The results are shown in Table 1.

[0040] The oil-water separation device is composed of a raw material tank 2 with an internal volume of 1.8 L equipped with a stirrer 1, a liquid delivery pump 4, a coalescer tank 6 with an internal volume of 0.7 L, and a filter element 5 made of carbon fiber with a capacity of 100 mL and a filtration accuracy of 15 μm.

[0041] The oil-water separation procedure is as follows. After charging 1 kg of the raw material liquid into the raw material tank 2, it is mixed and stirred with the stirrer 1 so that the liquid becomes uniform, and the liquid temperature is set to 40 °C with the heater 3. Then, the liquid is fed at a flow rate of 150 mL / min with the liquid delivery pump 4, passed through the filter element to separate the oil and water, the water phase after separation is sedimented in the coalescer tank 6, and the oil phase after separation is obtained from the outlet nozzle 7.

[0042] The water concentration in the separated oil phase was determined by the Karl Fischer reagent volumetric titration method using a moisture meter CA-200 type manufactured by Nitto Seiko Analytic and Aquamicron titrant SS-Z3mg and Aquamicron dehydrating solvent KTX.

[0043] [Example 2] In Example 1, formic acid was further mixed as a raw material to obtain the mixed composition liquid of Example 2 in Table 1. Experiments were carried out in the same procedure as in Example 1, and the water concentration in the obtained oil phase sample was measured. The results are shown in Table 1.

[0044] [Example 3] In Example 1, sodium hydroxide was further mixed as a raw material to obtain the mixed composition liquid of Example 3 in Table 1. Experiments were carried out in the same procedure as in Example 1, and the water concentration in the obtained oil phase sample was measured. The results are shown in Table 1.

[0045] [Examples 4, 5, Comparative Example 1] In Example 1, formic acid and sodium hydroxide were further mixed as raw materials to obtain the mixed composition liquids of Examples 4, 5 and Comparative Example 1 in Table 1. Experiments were carried out in the same procedure as in Example 1, and the water concentration in the obtained oil phase sample was measured. The results are shown in Table 1.

[0046]

Table 1

[0047] [Examination] In Examples 1 to 5, no change was observed in the water concentration in the separated oil phase. However, in Comparative Example 1 where the concentrations of formic acid and sodium were high, the water concentration in the oil phase was high. That is, formic acid and sodium alone do not affect oil-water separation, but when formic acid and sodium coexist, it has an adverse effect on oil-water separation, and it was confirmed that the water concentration in the oil phase after oil-water separation increases.

Explanation of Symbols

[0048] 1 Raw material stirrer 2 Raw material tank 3 Raw material tank heater 4 Liquid delivery pump 5 Filter element 6 Coalescer tank 7 Oil phase side outlet nozzle 8 Aqueous phase side outlet nozzle

Claims

1. A step of oxidizing cumene to produce cumene hydroperoxide (an organic acid is by-produced in this step), A step of decomposing cumene hydroperoxide in the presence of an acid to produce a solution containing phenol and acetone, A step of neutralizing the solution containing phenol and acetone with an aqueous solution of a sodium-containing basic compound and then separating the oil and water, and An oil phase water washing step of washing the oil phase liquid after oil-water separation with washing water using an oil phase water washing device, A method for producing phenol having: In the oil phase water washing step, a method for producing phenol, characterized in that the mixed liquid of the oil phase liquid and the washing water at the inlet of the oil phase water washing device satisfies at least one of the following (1) and (2). (1) The sodium concentration is 250 ppm or less (2) The organic acid concentration is 520 ppm or less

2. The method for producing phenol according to claim 1, wherein in the oil phase water washing step, the sulfuric acid concentration in the mixed liquid of the oil phase liquid and the washing water at the inlet of the oil phase water washing device is 50 ppm or less.

3. The method for producing phenol according to claim 1 or 2, wherein after the oil phase water washing step, the oil phase water is distilled to obtain phenol.

4. In the oil phase water washing step, the method for producing phenol according to any one of claims 1 to 3, characterized in that the mixed liquid of the oil phase liquid and the washing water at the inlet of the oil phase water washing device satisfies at least one of the following (3) and (4). (3) The sodium concentration is 50 ppm or less (4) The organic acid concentration is 100 ppm or less

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