CN113039154A

CN113039154A - Method for treating working solution

Info

Publication number: CN113039154A
Application number: CN201980075158.6A
Authority: CN
Inventors: 松浦慎一郎; 山本哲也; 栉田泰宏
Original assignee: Mitsubishi Gas Chemical Co Inc
Current assignee: Mitsubishi Gas Chemical Co Inc
Priority date: 2018-11-20
Filing date: 2019-11-12
Publication date: 2021-06-25
Anticipated expiration: 2039-11-12
Also published as: JPWO2020105500A1; TW202028167A; JP7327414B2; WO2020105500A1; CN113039154B; KR20210093846A; TWI828798B

Abstract

The purpose of the present invention is to provide a method for treating a working solution in which by-products, which are derived from anthraquinones and do not have a hydrogen peroxide generation ability and are contained in a working solution that is repeatedly used, are regenerated into anthraquinones, and the amount of the anthraquinones is increased. According to the present invention, there is provided a treatment method for treating a working solution by mixing the working solution with an alkali metal compound, wherein the working solution is used for producing peroxide by an anthraquinone method comprising a hydrogenation step, an oxidation step and an extraction stepThe working solution is continuously used in a hydrogen method, wherein the working solution to be treated before being mixed with the alkali metal compound is a working solution having a concentration of anthraquinones represented by the following general formula (1) or the following general formula (2) of less than 0.20mol/L (in the general formulae (1) and (2), R represents hydrogen or an alkyl group having 1 to 10 carbon atoms).

Description

Method for treating working solution

Technical Field

The present invention relates to a method for treating a working solution used for producing hydrogen peroxide by an anthraquinone method, and a method for producing hydrogen peroxide using the treated working solution. More specifically, the present invention relates to a treatment method for regenerating anthraquinone derivatives having no hydrogen peroxide generation ability into anthraquinones such as alkylanthraquinones and alkyltetrahydroanthraquinones by mixing a repeatedly used working solution with an alkali metal compound, and a method for producing hydrogen peroxide using the treated working solution.

Background

Currently, a major production method of hydrogen peroxide industrially used is an anthraquinone method in which anthraquinone, tetrahydroanthraquinone, alkylanthraquinone, or alkyltetrahydroanthraquinone (hereinafter, sometimes collectively referred to as anthraquinones) is used as a reaction medium. The anthraquinones are usually used in a state of being dissolved in a mixed solvent of 2 kinds of polar organic solvents and nonpolar organic solvents. The solution prepared by dissolving the anthraquinones in the mixed solvent is referred to as a working solution.

The anthraquinone process mainly comprises a hydrogenation process, an oxidation process and an extraction process. The hydrogenation step is a step of performing a hydrogenation treatment of hydrogenating anthraquinones in the working solution in the presence of a catalyst to produce corresponding anthraquinones. In the next oxidation step, the obtained anthrahydroquinones are oxidized with air or an oxygen-containing gas to convert the anthrahydroquinones into anthraquinones, and at this time, hydrogen peroxide is generated and dissolved in the working solution. In the next extraction step, the produced hydrogen peroxide is extracted with water and separated from the working solution. The working solution after the extraction step is returned to the hydrogenation step again and continuously used in the oxidation step and the extraction step ….

In the process of repeating the hydrogen peroxide production process, anthraquinone derivatives such as anthrone, hydroxyanthrone, tetrahydroanthraquinone epoxide, alkylanthrone, alkylhydroxyanthrone and alkyltetrahydroanthraquinone epoxide are produced in the working solution by side reactions. The anthraquinone derivative does not generate hydrogen peroxide even when it is supplied to the hydrogenation step and the oxidation step. The amount of by-produced anthraquinone derivatives is very small in a single cycle, but accumulates in the working solution during repetition of the hydrogen peroxide production process, and causes various problems.

As a technique for regenerating anthraquinones usable in a hydrogen peroxide production process from by-produced anthraquinone derivatives, patent document 1 proposes a technique for converting inactive ingredients (by-produced anthraquinone derivatives) into alkyltetrahydroanthraquinones by treating a working solution with an alkali and an aqueous alkali solution. However, the technique of patent document 1 requires a long reaction time. Further, since the alkyltetrahydroanthraquinones converted from the inactive components are recovered by crystallization, it is necessary to prepare a working solution by dissolving the recovered alkyltetrahydroanthraquinones in a solvent in order to reuse the same for the production of hydrogen peroxide. Therefore, the technique of patent document 1 is a very inefficient technique in view of the complexity of its apparatus and operation. Therefore, it is desired to establish a technique for regenerating a by-produced anthraquinone derivative which requires a short reaction time and does not require a complicated treatment step such as crystallization.

In addition, patent document 2 proposes a method in which a liquid containing alkyl anthrahydroquinone is brought into contact with a solid catalyst represented by alumina in order to convert alkyl tetrahydroanthraquinone epoxide, which is an anthraquinone derivative not involved in the production of hydrogen peroxide, into alkyl tetrahydroanthraquinone useful for the production of hydrogen peroxide. However, in the method of patent document 2, the alkyl anthrahydroquinone is required at a high concentration, and thus the efficiency of hydrogen peroxide production is significantly reduced. The reaction conditions are high temperature exceeding 100 ℃ for a long time of 1 to 20 hours. Therefore, there is still a demand for a technique for regenerating by-produced anthraquinone derivatives, which can be carried out by a reaction at a low reaction temperature in a short time without lowering the efficiency of hydrogen peroxide production.

Documents of the prior art

Patent document

Patent document 1: japanese examined patent publication No. 39-8806

Patent document 2: japanese examined patent publication No. 43-11658

Disclosure of Invention

Technical problem to be solved by the invention

Therefore, it is desired to develop a method for treating a working solution in which by-products derived from anthraquinones and having no hydrogen peroxide generation ability contained in the working solution to be reused are regenerated into anthraquinones, and the amount of the anthraquinones is increased.

Technical solution for solving technical problem

Namely, the present invention is as follows.

< 1 > a treatment method for treating a working solution by mixing the working solution with an alkali metal compound, the working solution being continuously used in a method for producing hydrogen peroxide by an anthraquinone method comprising a hydrogenation step, an oxidation step and an extraction step, the treatment method being characterized in that a working solution having a concentration of anthraquinones represented by the following general formula (1) or the following general formula (2) of less than 0.20mol/L is used as the working solution to be treated before mixing with the alkali metal compound.

(in the general formula (1) and the general formula (2), R represents hydrogen or alkyl with 1-10 carbon atoms.)

< 2 > the treatment method according to the above < 1 >, wherein the working solution to be treated is a part of the working solution withdrawn after the hydrogenation step and before the oxidation step, or a part of the working solution withdrawn after the hydrogenation step and before the oxidation step is diluted by adding the working solution before the hydrogenation step.

< 3 > the method of < 1 > above, wherein the working solution to be treated is a part of the working solution withdrawn after the extraction step and before the hydrogenation step.

< 4 > the treatment method according to any one of the above < 1 > to < 3 >, wherein the concentration of the anthraquinones is 0.05 to 0.10 mol/L.

< 5 > the treatment method according to any one of the above < 1 > to < 4 >, wherein the working solution to be treated further contains at least one anthraquinone derivative selected from the following general formulae (a) to (e).

(in the general formulae (a) to (e), R represents the same meaning as in the general formulae (1) and (2).)

< 6 > the treatment method as defined in any one of the above < 1 > to < 5 >, wherein R is ethyl, butyl or pentyl.

< 7 > the treatment method according to any one of the above < 1 > to < 6 >, wherein the working solution to be treated is mixed with the alkali metal compound at a temperature of 0 to 60 ℃.

< 8 > the treatment method according to any one of the above < 1 > - < 7 >, wherein the working solution to be treated and the aqueous solution of the alkali metal compound are mixed in an amount of at least 1: 1 (by volume) based on the ratio of the working solution to be treated to the aqueous solution of the alkali metal compound.

< 9 > the treatment method according to any one of the above < 1 > to < 8 >, wherein the alkali metal compound is sodium hydroxide or potassium hydroxide.

< 10 > the treatment method according to any one of the above < 1 > to < 9 >, wherein an aqueous sodium hydroxide solution having a sodium hydroxide concentration of 0.5mol/L or more is mixed.

< 11 > the treatment method according to any one of the above < 1 > to < 10 >, wherein the working solution to be treated is mixed with the aqueous solution of the alkali metal compound by means of a line mixer.

< 12 > the treatment method as defined in any of the above < 1 > to < 11 >, wherein the post-treatment is carried out by mixing with an alkali metal compound and then further mixing with an acid.

< 13 > the method of treatment as stated in above < 12 >, wherein the above acid is nitric acid or phosphoric acid.

< 14 > the treatment method as defined in the above < 12 > or < 13 >, wherein after mixing with the alkali metal compound, further mixing with an acidic aqueous solution having a nitric acid or phosphoric acid concentration of 0.20mol/L or more.

< 15 > the treatment method as defined in any one of above < 12 > to < 14 >, wherein the mixing with the acid is performed by a stirring mixer.

< 16 > the treatment method as defined in any one of the above < 12 > to < 15 >, wherein the acid is mixed and then the mixture is further mixed with water to perform post-treatment.

< 17 > the treatment method according to any one of the above < 12 > to < 16 >, wherein the post-treatment is performed such that the pH of the separated aqueous layer becomes 7 or less by stirring the post-treated working solution with pure water and then allowing the solution to stand.

< 18 > A method for producing hydrogen peroxide, characterized by producing hydrogen peroxide by the anthraquinone method using the working solution treated by the method described in any one of the above < 1 > to < 17 >.

ADVANTAGEOUS EFFECTS OF INVENTION

In the treatment method of the present invention, by mixing a working solution containing a specific amount of an anthraquinone with an alkali metal compound, the anthraquinone derivative as a by-product can be regenerated into an anthraquinone, and the amount of the anthraquinone can be increased.

Drawings

Fig. 1 is a view showing an example of the production method of the present invention.

FIG. 2 is a graph showing the relationship between the concentration of pentylanthrahydroquinones and the increase rate of pentylanthrahydroquinones in the working solutions to be treated in examples 1 to 5 and comparative example 1.

FIG. 3 is a graph showing the pH of the aqueous layer obtained in examples 6 to 9.

FIG. 4 is a graph showing the pH of the aqueous layer obtained in examples 13 to 16.

Detailed Description

The present invention will be described in detail below. The following embodiments are illustrative of the present invention, and are not intended to limit the present invention to these embodiments. The present invention can be implemented in various forms without departing from the spirit thereof.

The invention is the following invention: in the method for producing hydrogen peroxide by the anthraquinone method, a working solution in which by-products are accumulated due to continuous use is treated with an alkali.

In the anthraquinone method, a working solution in which anthraquinones are dissolved in an organic solvent is used.

The anthraquinones to be used include anthraquinone, tetrahydroanthraquinone, alkylanthraquinone, and alkyltetrahydroanthraquinone. Hereinafter, anthraquinone and alkylanthraquinone may be collectively referred to as (alkyl) anthraquinone. In addition, tetrahydroanthraquinone and alkyltetrahydroanthraquinone may be collectively referred to as (alkyl) tetrahydroanthraquinone. The (alkyl) anthraquinone and the (alkyl) tetrahydroanthraquinone may each be a mixture of a plurality of (alkyl) anthraquinones and (alkyl) tetrahydroanthraquinones. Examples of the (alkyl) anthraquinone include anthraquinone, ethylanthraquinone, tert-butylanthraquinone, and amylanthraquinone. Examples of the (alkyl) tetrahydroanthraquinone include tetrahydroanthraquinone, ethyltetrahydroanthraquinone, tert-butyltetrahydroanthraquinone, pentyltetrahydroanthraquinone, and the like.

The alkyl group of the anthraquinone is preferably an alkyl group having 1 to 10 carbon atoms, an ethyl group, a butyl group or a pentyl group.

As the organic solvent, any of a nonpolar solvent and a polar solvent can be used, and a mixed solvent of a nonpolar solvent and a polar solvent is preferably used. The nonpolar solvent includes aromatic hydrocarbons, and specifically, benzene or a benzene derivative having an alkyl substituent having 1 to 5 carbon atoms. As the benzene derivative, for example, pseudocumene can be cited. Examples of the polar solvent include higher alcohols such as diisobutylcarbinol, carboxylic acid esters, tetra-substituted urea, cyclic urea, and trioctylphosphonic acid. Preferred organic solvents are a combination of an aromatic hydrocarbon and a higher alcohol, or a combination of an aromatic hydrocarbon and a carboxylic ester of cyclohexanol or alkylcyclohexanol, or a tetra-substituted urea.

When the nonpolar organic solvent is mixed with the polar organic solvent, the mixing ratio (by volume) is preferably from 9: 1 to 1: 9, more preferably from 8: 2 to 2: 8, and particularly preferably from 4: 6 to 6: 4.

A catalyst in which a transition metal is supported on a carrier is usually added to the working solution to be subjected to hydrogenation. The carrier is not particularly limited, and for example, at least one selected from the group consisting of silica, silica-alumina, titania, zirconia, silica-alumina composite oxide, silica-titania composite oxide, alumina-titania composite oxide, and a physical mixture thereof can be used. The carrier preferably has a total pore volume of 0.2 to 2.0 ml/g. Particularly preferred supports are silica, alumina or silica-alumina composite oxides having a total pore volume of 0.2 to 2.0 ml/g. In addition, the total pore volume can be measured by mercury intrusion method.

As the transition metal, an element of palladium, rhodium, ruthenium, or platinum or a compound thereof is preferable, and an element of palladium or a compound thereof is more preferable. The compound is preferably an oxide from the viewpoint of being easily reduced to a metal under reaction conditions.

It is generally preferable that the transition metal is supported in an amount of 0.1 to 10 mass% relative to the support. The transition metal-supported hydrogenation catalyst is preferably used in an amount of 1 to 100g/L based on the catalyst slurry concentration in the working solution.

The specific process of the anthraquinone process is described with reference to FIG. 1. In fig. 1, the movement of the working solution is shown by a solid arrow and a dashed arrow. The solid arrows indicate the main flow of the working solution in the anthraquinone method. The dotted arrows indicate the flows of the following working solutions, which are supplied to the steps of alkali treatment and post-treatment, and then returned to the main flow of the anthraquinone method again:

a part of the working solution withdrawn after the hydrogenation step and before the oxidation step;

a part of the working solution withdrawn in the middle of the hydrogenation step;

a part of the working solution withdrawn after the extraction step and before the hydrogenation step.

In the anthraquinone method, first, a hydrogenation treatment of hydrogenating the working solution is performed. Thereby, the anthraquinones in the working solution are hydrogenated to produce the corresponding anthrahydroquinones (hydrogenation step). Then, the obtained anthrahydroquinones are oxidized with air or an oxygen-containing gas to convert the anthrahydroquinones into anthraquinones, and at this time, hydrogen peroxide is generated and dissolved in the working solution (oxidation step). Then, the generated hydrogen peroxide is extracted with water and separated from the working solution (extraction step). Thereafter, the hydrogen peroxide is supplied to a refining step and a concentrating step according to a conventional method to produce a product. On the other hand, the working solution after the extraction step is supplied to the hydrogenation step, and thereafter, is repeatedly used in the oxidation step and the extraction step ….

(alkali treatment)

The continuously used working solution contains by-products derived from anthraquinones produced by side reactions, for example, at least one anthraquinone derivative selected from the following general formulae (a) to (e).

(in the general formulae (a) to (e), R represents hydrogen or an alkyl group having 1 to 10 carbon atoms, preferably an ethyl group, a butyl group or a pentyl group.)

The above anthraquinone derivatives do not have hydrogen peroxide-generating ability. Therefore, it is significant to improve the production efficiency of hydrogen peroxide production by regenerating these anthraquinones having hydrogen peroxide generating ability. In the present invention, the regeneration of anthraquinones is achieved by mixing a continuously used working solution with an alkali metal compound. In the present specification, the regeneration treatment using the alkali metal compound is referred to as an alkali treatment.

In the present invention, it is important that the concentration of the anthraquinones in the working solution continuously used, that is, the concentration of the anthraquinones represented by the general formula (1) or the general formula (2) is less than 0.20mol/L at the stage before the mixing with the alkali metal compound. This is because it has been experimentally confirmed that when the working solution to be treated (sometimes referred to as a treatment target working solution) satisfies the above conditions, the anthraquinone derivative can be efficiently regenerated into anthraquinones and the amount of anthraquinones increases (see examples and comparative examples described later).

(in the general formulae (1) and (2), R represents hydrogen or an alkyl group having 1 to 10 carbon atoms, preferably an ethyl group, a butyl group or a pentyl group.)

The inventors of the present invention speculate that, since anthrahydroquinones are easily soluble in an aqueous solution of an alkali metal compound, if the number of anthrahydroquinones is too large, more anthrahydroquinones are dissolved in an aqueous solution of an alkali metal compound than anthraquinones produced in the regeneration reaction, and are lost, and thus, regeneration into anthraquinones cannot be achieved.

The concentration of anthrahydroquinones in the working solution to be treated which is supplied to the alkali treatment is preferably 0.02 to 0.10mol/L, and particularly preferably 0.05 to 0.10 mol/L. This is because when the concentration is in these numerical ranges, the increase rate of the anthraquinones represented by the following formula tends to be high.

Increase rate (%) of anthraquinones to the amount (mol/L) of anthraquinones in the treated working solution/total amount (mol/L) of anthraquinones and anthrahydroquinones in the treated working solution x 100

The reason why the increase rate of anthraquinones increases is not necessarily determined, but the inventors of the present invention presume as follows. The reactivity of hydrogen added in the hydrogenation step of anthraquinones is so high that hydrogen peroxide can be generated from oxygen without a catalyst, and the whole solution becomes a reducing atmosphere. It is considered that the anthraquinone derivative (deteriorated product) is efficiently regenerated into the anthraquinone by the reaction of the aqueous alkali solution due to the reducing environment.

The concentration of the anthraquinones can be measured by a gas chromatography analyzer (GC) as described in examples below.

In the present invention, the working solution to be treated to be subjected to alkali treatment is a solution of: in the hydrogen peroxide production process, a part of the working solution is extracted from the working solution at a stage other than after the oxygen removal step and before the extraction step. The working solution after the oxidation step and before the extraction step contains hydrogen peroxide at a higher concentration than the working solution in the other steps, and therefore, the working solution is not a subject of treatment in principle because of a problem of safety. Specifically, the working solution to be treated is a solution of: a part of the working solution withdrawn after the hydrogenation step and before the oxidation step, a part of the working solution withdrawn from the hydrogenation column in the middle of the hydrogenation step, a part of the working solution withdrawn after the extraction step and before the hydrogenation step, and the like.

When the concentration of anthrahydroquinones in the extracted working solution is too high, the solution is diluted. For example, the working solution withdrawn after the extraction step and before the hydrogenation step does not contain anthraquinones or contains a small amount of anthraquinones, and therefore has a low possibility of dilution, but the working solution withdrawn after the hydrogenation step and before the oxidation step has a high possibility of dilution because much anthraquinones are produced by hydrogenation. The working solution after the extraction step and before the hydrogenation step is preferably used for dilution.

The amount of the working solution to be pumped out may be determined as appropriate, and is preferably 0.1 to 20.0%, and more preferably 1.0 to 10.0%, of the total amount of the working solution flowing. When the amount of extraction is too large, the amount of working solution involved in hydrogen peroxide production decreases, and when the amount of extraction is too small, the effect of alkali treatment becomes insufficient.

The alkali metal used for the alkali treatment may be an alkali metal of group 1 (group Ia) of the periodic table, and is preferably lithium, sodium or potassium. Specific examples of the alkali metal compound include lithium hydroxide, sodium carbonate, sodium hydrogencarbonate, sodium borate, sodium diphosphate, sodium boron dioxide, sodium nitrite, sodium trioxide, sodium hydrogen phosphate, sodium silicate, sodium disilicate, sodium trisilicate, sodium stannate, sodium sulfide, sodium thiosulfate, sodium tungstate, potassium hydroxide, potassium borohydride, potassium carbonate, potassium cyanide, potassium nitrite, potassium phenoxide, potassium hydrogenphosphate, potassium diphosphate, potassium stannate, and the like. Preferred alkali metal compounds are sodium hydroxide or potassium hydroxide.

The alkali metal compound is usually used in the form of an aqueous solution. It was confirmed through experiments that the increase rate of anthraquinones increases as the concentration of the alkali metal compound increases (not disclosed in the present specification). Further, if the concentration is too low, the density difference between the 2 kinds of solutions becomes small when separating the alkali metal compound from the working solution after the treatment, and there is a high possibility that a long time is required for the separation. Therefore, the concentration of the alkali metal compound in the aqueous solution is preferably 0.5mol/L or more. The upper limit of the concentration is not particularly limited, but is usually 10.0 mol/L.

The working solution to be treated and the aqueous alkali metal compound solution are usually mixed at a ratio of 1 to 1, preferably 1 to 30: 1, and particularly preferably 1 to 20: 1 (by volume) to each other.

The inventors of the present invention have experimentally studied the temperature conditions during mixing, and as a result, have confirmed that the temperature does not affect the alkali treatment. Therefore, the temperature conditions are not particularly limited, and the mixing may be performed at any temperature. Usually at 0-60 deg.C.

The mixing time may be appropriately determined so that the working solution to be treated and the aqueous solution of the alkali metal compound can be sufficiently mixed. For example, in the case of stirring and mixing, it is sufficient to mix for 3 minutes or more. In addition, when mixing is performed in a pipe using a line mixer, the mixing time is less than several seconds based on the principle, but the effect of the present invention can be obtained without any problem. The inventors of the present invention confirmed through experiments that even if the mixing time is increased, the increase rate of anthraquinones is not affected, and therefore the mixing may be terminated at an appropriate timing.

(post-treatment)

And obtaining a mixed solution of the regeneration working solution and the alkali metal compound aqueous solution through alkali treatment. It is absolutely inevitable that the alkali metal compound and hydrogen peroxide undergo a neutralization reaction to decompose the hydrogen peroxide, and the decomposition reaction of the hydrogen peroxide may cause a sudden increase in pressure in the facility or an accident such as explosion. Therefore, after the post-treatment for removing the alkali metal compound, the regenerated working solution is returned to the hydrogen peroxide production process.

Specifically, after the regeneration working solution and the aqueous solution of the alkali metal compound are separated by a known method such as static separation, at least one of acid treatment and water washing is further performed, preferably, acid treatment or both of acid treatment and water washing are performed, and particularly, both of acid treatment and water washing are preferably performed. When both the acid treatment and the water washing are performed, the acid treatment and the water washing are preferably performed in this order.

The condition for bringing the mixed solution of the regeneration working solution and the aqueous solution of an alkali metal compound into contact with an acid is very important for safe and stable operation of the apparatus.

The acid used for the acid treatment may be an acid such as hydrochloric acid, sulfuric acid, nitric acid, or phosphoric acid, and preferably nitric acid or phosphoric acid. This is because the materials of the main structural bodies of the hydrogen peroxide production apparatus are SUS materials, aluminum materials, and nitric acid and phosphoric acid are not corrosive to these materials. Further, there is no fear of remaining in the working solution and poisoning the hydrogenation catalyst.

The acid treatment is carried out by bringing the regeneration working solution into contact with an acidic aqueous solution in which an acid is dissolved, with stirring by a known apparatus such as a stirring mixer. The concentration of the acidic aqueous solution is usually 0.20mol/L or more, and from the viewpoint of particularly excellent removal effect of the alkali metal compound, it is preferably higher than 0.25mol/L, more preferably 0.30mol/L or more, further preferably 0.35mol/L or more, and particularly preferably 0.50mol/L or more. The upper limit of the concentration of the acidic aqueous solution is usually 5.00mol/L or less, and is less than 3mol/L from the viewpoint of the balance between the removal effect and the cost and safety. Inert gas such as nitrogen may be introduced during the stirring. After completion of the stirring, the working solution is separated from the aqueous solution by a known method such as static separation.

The washing with water is carried out by bringing the regeneration working solution into contact with water with stirring by a known device such as a stirring mixer. The "water" is preferably distilled water, ion-exchanged water, or water purified by a reverse osmosis method or the like. The ratio of water to the regenerated working solution is 0.02 parts by volume or more, preferably 0.10 parts by volume or more, based on 1 part by volume of the working solution. The upper limit is not particularly limited, but is usually 0.50 parts by volume.

The washing time may be determined appropriately in such a manner that the working solution is sufficiently mixed with water. For example, in the case of stirring and mixing, it is sufficient to mix for 1 minute or more. The washing time may be determined appropriately without an upper limit. In addition, mixing in the pipe using a line mixer may be performed.

The temperature of the water for washing is 0-70 ℃, more preferably 10-60 ℃, and particularly preferably 20-50 ℃.

Inert gas such as nitrogen may be introduced during the stirring. After completion of the stirring, the working solution is separated from water by a known technique such as static separation.

The post-treatment is preferably carried out by allowing the working solution after the post-treatment to stand so that the pH of the separated aqueous layer becomes 7 or less, particularly preferably 6 or less.

The regenerated working solution from which the alkali metal compound is removed by the post-treatment is returned to the hydrogen peroxide production process. The stage of return may be decided as appropriate. The regeneration working solution contains anthraquinones in addition to anthraquinones, and the anthraquinones can generate hydrogen peroxide through an oxidation reaction. Therefore, from the viewpoint of efficiently producing hydrogen peroxide by effectively utilizing the anthraquinones produced in the hydrogenation step, it is preferable to return to the stage after the hydrogenation step and before the oxidation step as shown in fig. 1.

The regeneration of the working solution by the alkali treatment has been described so far, but in the present invention, the alkali treatment may be combined with a known regeneration treatment. For example, in addition to the alkali treatment, a regeneration reaction may be performed in which a part of the working solution after the extraction step and before the hydrogenation step is extracted and brought into contact with the particulate alumina.

Examples

The present invention will be described more specifically with reference to the following examples, but the present invention is not limited to the following examples.

< Gas Chromatography (GC) analysis >

The amylanthraquinone, amyltetrahydroanthraquinone and amylanthrahydroquinones (amylanthraquinone and amyltetrahydroanthrahydroquinone) in the working solutions of examples and comparative examples were measured by GC under the following conditions and analyzed.

The device comprises the following steps: GC-2014 manufactured by Shimadzu

A detector: hydrogen Flame Ionization Detector (FID)

Analyzing a chromatographic column: rtx-50 manufactured by Restek corporation

(length 30m, inner diameter 0.25mm, film thickness 0.5 μm)

Carrier gas: he (He)

Temperature of sample introduction part: 250 deg.C

Detector temperature: 310 deg.C

Sample introduction amount: 1 μ L

The split ratio is as follows: 50

Temperature rising procedure: 110 ℃ (hold for 8 minutes) → ramp up at 10 ℃/minute → 310 ℃ (hold for 10 minutes)

< determination of pH >

The residual alkali metal compound in the regenerated working solution after the post-treatment was judged by measuring the pH. Specifically, the working solution after the post-treatment was left to stand, and the pH of the separated aqueous layer was measured by a pH meter.

The device comprises the following steps: horiba manufacture's pH meter D-74

An electrode: pH electrode 9625-10D manufactured by horiba

Reagent for pH correction:

neutral phosphate pH Standard solution (Fuji film, Wako pure chemical industries, Ltd.) has a pH of 6.86

Ph4.01 of phthalate pH Standard solution (Fuji film and Wako pure chemical industries, Ltd.)

Borate pH Standard solution (Fuji film, Wako pure chemical industries, Ltd.) has a pH of 9.18

< example 1 >

(hydrogenation treatment)

A working solution containing amylanthraquinone at a concentration of 0.543mol/L and amyltetrahydroanthraquinone at a concentration of 0.053mol/L and using a mixed organic solvent (pseudocumene: diisobutylcarbinol: 55: 45) was prepared. The working solution is a working solution that is actually reused in the apparatus. Hereinafter, this working solution is referred to as a pre-hydrogenation working solution.

The working solution before hydrogenation was subjected to hydrogenation treatment to prepare a working solution containing 0.020mol/L of pentylanthrahydroquinones. In the hydrogenation treatment, 50mL of the working solution before hydrogenation and 100mg of a hydrogenation catalyst in which palladium was supported on silica-alumina were placed in a flask, and the hydrogen in the gas phase was replaced, followed by reduction with stirring. The amount of reduction (concentration of pentylanthrahydroquinone) was calculated from the amount of hydrogen absorbed. After reaching the specified hydrogen absorption amount, the working solution is filtered out of the catalyst by using a disposable syringe and a filter cartridge to obtain the working solution subjected to the hydrogenation reaction.

(alkali treatment)

The working solution subjected to hydrogenation reaction is used as a working solution to be treated, and is brought into contact with a base. 50mL of the working solution to be treated was contacted with 50mL of a 1mol/L aqueous solution of sodium hydroxide with stirring. While stirring, nitrogen was introduced and the reaction was carried out on a hot water bath at 50 ℃. After 15 minutes, the stirring was stopped, and the working solution was separated from the aqueous sodium hydroxide solution by a separatory funnel to obtain a regenerated working solution a.

(acid treatment)

The regenerated working solution A thus obtained was contacted with 50mL of 1mol/L nitric acid with stirring. While stirring, nitrogen was introduced and the reaction was carried out on a hot water bath at 50 ℃. After 15 minutes, the stirring was stopped, and the working solution was separated from the nitric acid by a separatory funnel to obtain a regenerated working solution B.

(Water washing)

The resulting regenerated working solution B was brought into contact with 50mL of pure water with stirring. While stirring, nitrogen was introduced and the reaction was carried out on a hot water bath at 50 ℃. After 15 minutes, the stirring was stopped, and the working solution was separated from pure water by a separatory funnel to obtain a regenerated working solution C.

< example 2 >

A working solution to be treated containing 0.050mol/L of pentylanthrahydroquinones was obtained, and hydrogenation treatment, alkali treatment, acid treatment, and water washing were performed in the same manner as in example 1 except for using the working solution to be treated, thereby obtaining a regenerated working solution C.

< example 3 >

A working solution to be treated containing 0.100mol/L of pentylanthrahydroquinones was obtained, and hydrogenation treatment, alkali treatment, acid treatment and water washing were carried out in the same manner as in example 1 except for using the working solution to be treated, thereby obtaining a regenerated working solution C.

< example 4 >

A working solution to be treated containing 0.150mol/L of pentylanthrahydroquinones was obtained, and hydrogenation treatment, alkali treatment, acid treatment and water washing were carried out in the same manner as in example 1 except for using the working solution to be treated, thereby obtaining a regenerated working solution C.

< example 5 >

A working solution to be treated having a concentration of pentylanthrahydroquinones of 0.000mol/L was obtained, and hydrogenation treatment, alkali treatment, acid treatment and water washing were carried out in the same manner as in example 1 except for using the working solution to be treated, thereby obtaining a regenerated working solution C. The working solution to be treated having a concentration of 0.000mol/L of pentylanthrahydroquinones refers to a working solution obtained by setting the hydrogen absorption amount to 0 in the hydrogenation treatment described in example 1.

< comparative example 1 >

A working solution to be treated containing 0.200mol/L of pentylanthrahydroquinones was obtained, and hydrogenation treatment, alkali treatment, acid treatment and water washing were carried out in the same manner as in example 1 except for using the working solution to be treated, thereby obtaining a regenerated working solution C.

Table 1 shows the concentrations of amylanthraquinone (Amaq concentration in the table) and amyltetrahydroanthraquinone (AmTHAQ concentration in the table) in the working solution before hydrogenation, the treated working solution and the regenerated working solution C obtained in the above examples and comparative examples. The working solution to be treated also showed the concentration of pentylanthrahydroquinone (shown as AmHQ concentration in the table).

The increase rate of pentylanthraquinones was calculated by the following formula, and the relationship between the increase rate of pentylanthraquinones and the concentration of pentylanthrahydroquinones in the working solution to be treated is shown in FIG. 2.

The increasing rate of the pentylanthraquinones (AmAQ concentration in the regenerating working solution C + AmTHAQ concentration in the regenerating working solution C)/(AmAQ concentration in the working solution to be treated + AmTHAQ concentration in the working solution to be treated + AmHQ concentration in the working solution to be treated) × 100

[ Table 1]

From these results, it was found that the regeneration amount of amylanthraquinone was changed depending on the concentration of amylanthrahydroquinones in the working solution to be treated. In examples 1 to 5, the AmAQ concentration in the regenerated working solution C was higher than that in the working solution before hydrogenation (0.543 mol/l). The regeneration effect of amylanthraquinone by alkali treatment is excellent when the concentration of amylanthrahydroquinone is in the range of 0.02 to 0.10mol/L, particularly 0.05 to 0.10 mol/L. Further, the hydrogenation rate represented by the following formula is 8 to 16% when the concentration of the pentylanthrahydroquinones is 0.05 to 0.10 mol/L.

Hydrogenation ratio (%) (% by mol/L) of pentylanthrahydroquinone type concentration in the working solution to be treated/total (mol/L). times.100 of pentylanthraquinone and pentyltetrahydroanthraquinone in the working solution before hydrogenation

In the alkali treatment without inclusion of amylanthrahydroquinones (no hydrogenation treatment), the concentration of amylanthraquinone was increased to only 0.545mol/L, and it was found that when the concentration of amylanthrahydroquinones was in the above range, a higher effect of regeneration of amylanthraquinone could be obtained than under the conditions without inclusion of amylanthrahydroquinones.

< example 6 >

Experiments were carried out for the mixing with an acid carried out after the contact with the alkali metal compound. As described above, in the process for producing hydrogen peroxide, when the alkali metal compound is brought into contact with hydrogen peroxide, decomposition of hydrogen peroxide is promoted. The decomposition reaction of hydrogen peroxide may cause a sudden increase in pressure in the equipment or an explosion, and is inevitably avoided. That is, the condition of contacting the working solution after contacting with the alkali metal with the acid is very important for safe and stable operation of the apparatus.

(hydrogenation treatment)

A working solution containing amylanthraquinone at a concentration of 0.543mol/L and amyltetrahydroanthraquinone at a concentration of 0.053mol/L and using a mixed organic solvent (pseudocumene: diisobutylcarbinol: 55: 45) was prepared. The working solution is a working solution that is actually reused in the apparatus. The working solution was subjected to hydrogenation treatment to prepare a working solution to be treated containing 0.100mol/L of pentylanthrahydroquinones. In the hydrogenation treatment, 500mL of the working solution before hydrogenation and 1000mg of a hydrogenation catalyst in which palladium was supported on silica-alumina were placed in a flask, and the gas phase portion was replaced with hydrogen, followed by reduction with stirring. The amount of reduction (concentration of pentylanthrahydroquinone) was calculated from the amount of hydrogen absorbed. After the predetermined hydrogen absorption amount is reached, the catalyst is filtered from the working solution by a disposable syringe and a filter cartridge to obtain a treated working solution.

(alkali treatment)

500mL of the working solution to be treated and 25mL of a 2.0mol/L aqueous solution of sodium hydroxide were placed in a 1L measuring cup and stirred for 5 minutes. While stirring, nitrogen was introduced and the reaction was carried out at 25 ℃. After the stirring was stopped, the working solution was separated from the aqueous sodium hydroxide solution by a separatory funnel to obtain a regenerated working solution D.

(acid treatment)

The regenerated working solution D thus obtained was contacted with 50mL of 1mol/L nitric acid with stirring. While stirring, nitrogen was introduced and the reaction was carried out at 25 ℃. After 15 minutes, the stirring was stopped, and the working solution was separated from the nitric acid by a separatory funnel to obtain a regenerated working solution E.

(Water washing)

The resulting regenerated working solution E was brought into contact with 50mL of pure water with stirring. While stirring, nitrogen was introduced and the reaction was carried out at 25 ℃. After 5 minutes, the stirring was stopped and the working solution was separated from the aqueous layer using a separatory funnel.

< example 7 >

The alkali treatment, the acid treatment and the water washing were carried out in the same manner as in example 6 except that nitric acid was used in an amount of 0.5mol/L, and the working solution was separated from the aqueous layer by a separatory funnel.

< example 8 >

The alkali treatment, the acid treatment and the water washing were carried out in the same manner as in example 6 except that 0.35mol/L nitric acid was used for the acid treatment, and the working solution and the aqueous layer were separated by a separatory funnel.

< example 9 >

The alkali treatment, the acid treatment and the water washing were carried out in the same manner as in example 6 except that nitric acid was used in an amount of 0.25mol/L, and the working solution was separated from the aqueous layer by a separatory funnel.

The results of the pH measurements on the water layers obtained in examples 6 to 9 are shown in Table 2 and FIG. 3.

[ Table 2]

In examples 6 to 9, sufficient amounts of pentylanthraquinones were obtained. When the concentration of nitric acid used for the acid treatment is 0.35mol/L or more, the pH of pure water after contact with the regeneration working solution is sufficiently lower than 7, and the alkali metal compound is removed from the regeneration working solution. On the other hand, when the nitric acid concentration is 0.25mol/L, the pH of pure water after contact with the regeneration working solution exceeds 7, and a part of the alkali metal compound remains in the regeneration working solution. This shows that, in order to sufficiently remove the alkali metal compound from the regeneration working solution, it is preferable to perform the acid treatment using nitric acid having a concentration higher than 0.25mol/L, more preferably 0.35mol/L or more. Further, it is considered that the more concentrated the nitric acid is, the more the effect of removing the alkali metal compound is improved, but from the viewpoint of the balance between the removal effect and the cost and safety, it is preferable to perform the acid treatment using nitric acid at a concentration of 0.50mol/L or more and less than 3 mol/L.

The various examples/comparative examples described above demonstrate that anthraquinones can be regenerated by the treatment of the present invention, but in order to directly prove that the regeneration of anthraquinones is from the by-product (anthraquinone derivative) to the regeneration of anthraquinones, the following experiments were carried out.

< example 10 >

Experiments were conducted on regeneration of the alkylhydroxyanthrainones represented by the above general formulae (d) to (e) into anthraquinones useful for production of hydrogen peroxide.

Specifically, a regenerated working solution C was obtained in the same manner as in example 1, except that the solution used was a solution containing amylanthraquinone (AmAQ) at a concentration of 0.509mol/L, amylhydroxyanthracene (AmOX) at a concentration of 0.012mol/L, and a mixed organic solvent (pseudocumene/diisobutylcarbinol: 55/45). As a result, the regenerated working solution C contained amylanthraquinone (AmAQ) at a concentration of 0.527mol/L and amylhydroxyanthrone (AmOX) at a concentration of 0.001 mol/L.

In the regeneration working solution C, the amyl hydroxyl anthrone is greatly reduced, and the sufficient regeneration effect of the amyl hydroxyl anthrone to the amyl anthraquinone is obtained.

< example 11 >

Experiments were conducted on the phenomenon in which the aforementioned alkyl tetrahydroanthraquinone epoxides represented by general formula (a) are regenerated into anthraquinones useful for the production of hydrogen peroxide.

Specifically, a regenerated working solution C was obtained in the same manner as in example 1 except that 50mL of a working solution containing 0.016mol/L of pentyltetrahydroanthraquinone epoxide, 0.092mol/L of pentylanthraquinone, and 0.000mol/L of pentyltetrahydroanthraquinone was used as the working solution before hydrogenation, in which predetermined amounts of pentyltetrahydroanthraquinone epoxide were dissolved in the mixed organic solvent (pseudocumene/diisobutylcarbinol: 60: 40). As a result, the regeneration working solution C contained pentyltetrahydroanthraquinone epoxide (AmTHEP) at a concentration of 0.003mol/L, pentyltetrahydroanthraquinone (AmTHAQ) at a concentration of 0.009mol/L, and pentylanthraquinone (AmAQ) at a concentration of 0.094 mol/L.

In the regeneration working solution C, amyltetrahydroanthraquinone epoxide is greatly reduced, and amyltetrahydroanthraquinone as a regeneration product is increased. Thus, a sufficient effect of regenerating amyltetrahydroanthraquinone epoxide to amyltetrahydroanthraquinone was obtained.

< example 12 >

Experiments were conducted on the phenomenon in which the alkyl anthrones represented by the general formulae (b) and (c) described above are regenerated into anthraquinones useful for the production of hydrogen peroxide.

Specifically, since alkyl anthrone is generally contained in a small amount in a working solution of an actual device, an experiment was performed using (R ═ hydrogen) anthrone having no alkyl group (anthrone, manufactured by fujifilm and wako pure chemical industries, and photoscale). However, anthrone (アンスロン) is described as anthrone (アントロン) by fuji film and wako pure chemical industries, ltd.

A regenerated working solution C was obtained in the same manner as in example 1 except that 50mL of a working solution containing 0.050mol/L of anthrone in which a predetermined amount of anthrone was dissolved in the mixed organic solvent (pseudocumene/diisobutylcarbinol: 60/40) was used as the pre-hydrogenation working solution. The concentration of Anthrone (AN) contained in the working solution C and the regeneration working solution C is 0.032mol/L, and the concentration of Anthraquinone (AQ) is 0.020 mol/L.

The anthrone in the regeneration working solution C decreased and the anthraquinone as a regeneration product increased. Thus, a sufficient effect of regenerating anthraquinones from anthrone is obtained.

From examples 10 to 12 described above, it was confirmed that amyltetrahydroanthraquinone epoxide, amylhydroxyanthrone and anthrone were regenerated into amylanthraquinones. However, it is presumed that the anthraquinone by-products other than these, which have not been identified, are also regenerated into anthraquinones, and the possibility of contributing to increase of the concentration of anthraquinones in the alkali-treated working solution is also sufficiently present.

< example 13 >

The same experiment as in example 6 was carried out using phosphoric acid instead of nitric acid. However, phosphoric acid is a weak acid compared to nitric acid, and thus the number of contacts with acid is increased from 1 to 2. Specifically, the following operation is performed.

(hydrogenation and alkali treatment)

The same working solution as in example 6 was used, and hydrogenation treatment and alkali treatment were carried out in the same manner as in example 6 to obtain a regenerated working solution D.

(first acid treatment)

The resulting regenerated working solution D was contacted with 50mL of 1.0mol/L phosphoric acid with stirring. While stirring, nitrogen was introduced and the reaction was carried out at 25 ℃. After 15 minutes, the stirring was stopped, and the working solution was separated from phosphoric acid by a separatory funnel to obtain a regenerated working solution E1.

(second acid treatment)

The resulting regenerated working solution E1 was contacted with 50mL of 1.00mol/L phosphoric acid with stirring. While stirring, nitrogen was introduced and the reaction was carried out at 25 ℃. After 15 minutes, the stirring was stopped, and the working solution was separated from phosphoric acid by a separatory funnel to obtain a regenerated working solution E2.

(Water washing)

The resulting regenerated working solution E2 was contacted with 50mL of pure water with stirring. While stirring, nitrogen was introduced and the reaction was carried out at 25 ℃. After 5 minutes, the stirring was stopped and the working solution was separated from the aqueous layer using a separatory funnel.

< example 14 >

The same procedures as in example 13 were repeated except that 0.50mol/L phosphoric acid was used in the acid treatment 2 times, and the alkali treatment, the acid treatment and the water washing were carried out, and the working solution and the water layer were separated by a separatory funnel.

< example 15 >

The same procedures as in example 13 were repeated except that 0.25mol/L phosphoric acid was used in the acid treatment 2 times, and the alkali treatment, the acid treatment and the water washing were carried out, and the working solution and the water layer were separated by a separatory funnel.

< example 16 >

The same procedures as in example 13 were repeated except that 0.13mol/L phosphoric acid was used in the acid treatment 2 times, and the alkali treatment, the acid treatment and the water washing were carried out, and the working solution and the water layer were separated by a separatory funnel.

The results of pH measurement of the water layers obtained in examples 13 to 16 are shown in Table 3 and FIG. 4.

[ Table 3]

In examples 13 to 16, sufficient amounts of pentylanthraquinones were obtained. When the concentration of phosphoric acid used for the acid treatment is 0.25mol/L or more, the pH of the aqueous layer after the contact of pure water with the regeneration working solution is sufficiently lowered to 7, and the alkali metal compound is sufficiently removed from the regeneration working solution. On the other hand, when the nitric acid concentration is 0.13mol/L, the pH of the aqueous layer after the contact of pure water with the regeneration working solution exceeds 7, and a part of the alkali metal compound remains in the regeneration working solution. This shows that, in order to sufficiently remove the alkali metal compound from the regeneration working solution, it is preferable to perform the acid treatment using phosphoric acid having a concentration of 0.25mol/L or more. Further, it is considered that the more concentrated the nitric acid is, the more the effect of removing the alkali metal compound is improved, but from the viewpoint of the balance between the removal effect and the cost and safety, it is preferable to perform the acid treatment using phosphoric acid at a concentration of 0.50mol/L or more and less than 3 mol/L.

Claims

1. A treatment method for treating a working solution by mixing the working solution with an alkali metal compound, the working solution being continuously used in a method for producing hydrogen peroxide by an anthraquinone method including a hydrogenation step, an oxidation step, and an extraction step, the treatment method being characterized in that:

as the working solution to be treated before mixing with the alkali metal compound, a working solution in which the concentration of the anthraquinones represented by the following general formula (1) or the following general formula (2) is less than 0.20mol/L is used,

in the general formula (1) and the general formula (2), R represents hydrogen or alkyl with 1-10 carbon atoms.

2. The process of claim 1, wherein:

the working solution to be treated is a part of the working solution withdrawn after the hydrogenation step and before the oxidation step, or a part of the working solution withdrawn after the hydrogenation step and before the oxidation step is diluted by adding the working solution before the hydrogenation step.

3. The process of claim 1, wherein:

the working solution to be treated is a part of the working solution withdrawn after the extraction step and before the hydrogenation step.

4. The treatment method according to any one of claims 1 to 3, wherein:

the concentration of the anthraquinone is 0.05-0.10 mol/L.

5. The process according to any one of claims 1 to 4, characterized in that:

the working solution to be treated further contains at least one anthraquinone derivative selected from the following general formulae (a) to (e),

in the general formulae (a) to (e), R represents the same meaning as in the general formulae (1) and (2).

6. The process according to any one of claims 1 to 5, characterized in that:

and R is ethyl, butyl or pentyl.

7. The process according to any one of claims 1 to 6, characterized in that:

and mixing the treated working solution with an alkali metal compound at the temperature of 0-60 ℃.

8. The process according to any one of claims 1 to 7, characterized in that:

the treatment target solution and the aqueous solution of the alkali metal compound are mixed in an amount of treatment target solution: aqueous alkali metal compound solution: 1 or more: 1 (by volume).

9. The process according to any one of claims 1 to 8, characterized in that:

the alkali metal compound is sodium hydroxide or potassium hydroxide.

10. The process of any one of claims 1 to 9, wherein:

an aqueous sodium hydroxide solution having a sodium hydroxide concentration of 0.5mol/L or more is mixed.

11. The process according to any one of claims 1 to 10, characterized in that:

and mixing the treated working solution with the aqueous solution of the alkali metal compound by using a pipeline mixer.

12. The process according to any one of claims 1 to 11, characterized in that:

after mixing with an alkali metal compound, the mixture is further mixed with an acid to carry out a post-treatment.

13. The process of claim 12, wherein:

the acid is nitric acid or phosphoric acid.

14. The processing method according to claim 12 or 13, characterized by:

mixing the resulting mixture with an alkali metal compound, and further mixing the resulting mixture with an acidic aqueous solution having a nitric acid or phosphoric acid concentration of 0.20mol/L or more.

15. The process of any one of claims 12 to 14, wherein:

the mixing with the acid is carried out by means of a stirring mixer.

16. The process of any one of claims 12 to 15, wherein:

after mixing with the acid, it is further mixed with water for post-treatment.

17. The process of any one of claims 12 to 16, wherein:

the working solution after the post-treatment was stirred with pure water and then left to stand, and the post-treatment was performed so that the pH of the separated water layer was 7 or less.

18. A method for producing hydrogen peroxide, characterized by comprising:

hydrogen peroxide is produced by an anthraquinone process using the working solution treated by the method according to any one of claims 1 to 17.