CN113039154B

CN113039154B - Working solution treatment method

Info

Publication number: CN113039154B
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: 2023-11-03
Anticipated expiration: 2039-11-12
Also published as: JPWO2020105500A1; JP7327414B2; TWI828798B; CN113039154A; KR20210093846A; WO2020105500A1; TW202028167A

Abstract

The purpose of the present invention is to provide a method for treating a working solution, wherein a byproduct which is contained in a reused working solution and is derived from anthraquinones and does not have hydrogen peroxide generating ability is regenerated into anthraquinones, and the amount of 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 a working solution used continuously in a method for producing hydrogen peroxide by an anthraquinone process comprising a hydrogenation step, an oxidation step and an extraction step, and the method is characterized in that a working solution having a concentration of anthrahydroquinones represented by the following general formula (1) or the following general formula (2) of less than 0.20mol/L is used as a working solution to be treated before mixing with the alkali metal compound, wherein R represents hydrogen or an alkyl group having 1 to 10 carbon atoms in the general formulae (1) and (2).

Description

Working solution treatment method

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 generating ability into anthraquinones such as alkylanthraquinone and alkyltetrahydroanthraquinone by mixing a reusable working solution with an alkali metal compound, and a method for producing hydrogen peroxide using the treated working solution.

Background

Currently, the main method for producing hydrogen peroxide industrially used is the anthraquinone method using anthraquinone, tetrahydroanthraquinone, alkylanthraquinone or alkyltetrahydroanthraquinone (hereinafter, may be collectively referred to as "anthraquinones") as a reaction medium. The anthraquinones are generally 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 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 carrying out hydrogenation treatment for hydrogenating anthraquinones in the working solution in the presence of a catalyst to produce corresponding anthrahydroquinones. In the next oxidation step, the obtained anthrahydroquinones are oxidized by air or an oxygen-containing gas to be returned to the anthraquinones, and at this time, hydrogen peroxide is generated and dissolved in the working solution. In the subsequent extraction step, the hydrogen peroxide produced 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 is continuously used in the oxidation step and the extraction step ….

In the course of repeating the hydrogen peroxide production process, anthraquinone derivatives such as anthrone, hydroxyanthrone, tetrahydroanthraquinone epoxide, alkylanthrone, alkylhydroxyanthrone, alkyltetrahydroanthraquinone epoxide and the like are produced in the working solution due to side reactions. The anthraquinone derivative cannot produce hydrogen peroxide even when supplied to the hydrogenation step and the oxidation step. Although the amount of the by-product of the anthraquinone derivative is very small in a single cycle, the by-product accumulates in the working solution during the 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 a byproduct anthraquinone derivative, patent document 1 proposes a technique for converting an inactive component (byproduct anthraquinone derivative) 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, the alkyltetrahydroanthraquinone converted from the inactive ingredient is recovered by crystallization, and thus in order to reuse the recovered alkyltetrahydroanthraquinone for the production of hydrogen peroxide, it is necessary to prepare a working solution again by dissolving it in a solvent. Therefore, the technique of patent document 1 is a very inefficient technique in view of the complexity of its equipment and operation. Therefore, it is desired to establish a technique for regenerating an anthraquinone derivative as a byproduct which has a short reaction time and does not require complicated treatment steps such as crystallization.

Patent document 2 proposes a method of bringing a liquid containing alkylanthrahydroquinone into contact with a solid catalyst typified by alumina in order to convert an alkyltetrahydroanthraquinone epoxide, which is an anthraquinone derivative that does not participate in the production of hydrogen peroxide, into an alkyltetrahydroanthraquinone useful for the production of hydrogen peroxide. However, in the method of patent document 2, a high concentration of alkylanthrahydroquinone is required, and thus the efficiency of hydrogen peroxide production is significantly reduced. The reaction conditions are long-term, such as a reaction time of 1 to 20 hours at a high temperature exceeding 100 ℃. Accordingly, a technique for regenerating an anthraquinone derivative as a by-product, which can be carried out at a low reaction temperature in a short time without reducing the efficiency of hydrogen peroxide production, has been desired.

Prior art literature

Patent literature

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

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

Disclosure of Invention

Technical problem to be solved by the invention

Therefore, it is desired to develop a treatment method for regenerating by-products which are derived from anthraquinones and do not have hydrogen peroxide generating ability and contained in a reusable working solution into anthraquinones, thereby increasing the amount of the anthraquinones.

Technical scheme for solving technical problems

Namely, the present invention is as follows.

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

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

The method according to claim 2, wherein the working solution to be treated is a part of the working solution extracted after the hydrogenation step and before the oxidation step, or a solution obtained by diluting the working solution before the hydrogenation step with the part of the working solution extracted after the hydrogenation step and before the oxidation step.

The method according to claim 1, wherein the working solution to be treated is a part of the working solution extracted after the extraction step and before the hydrogenation step.

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

The method according to any one of < 1 > < 4 > above, 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))

The method according to any one of < 1 > - < 5 > wherein R is ethyl, butyl or pentyl.

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

The 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 such an amount that the ratio of the working solution to be treated to the aqueous solution of the alkali metal compound=1 or more to 1 (volume).

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

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

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

The method according to any one of < 12 > to < 1 > - < 11 > above, wherein the mixture is mixed with an alkali metal compound and then further mixed with an acid to carry out a post-treatment.

The method of treatment according to < 13 > as described above with < 12 >, wherein the acid is nitric acid or phosphoric acid.

The method of treating < 14 > according to the above < 12 > or < 13 >, wherein the mixture is further mixed with an acidic aqueous solution having a nitric acid or phosphoric acid concentration of 0.20mol/L or more after mixing with an alkali metal compound.

The method according to any one of < 15 > and < 12 > - < 14 > above, wherein the mixing with the acid is performed by using a stirring mixer.

The method according to any one of < 16 > and < 12 > - < 15 > above, wherein the acid is mixed with the above-mentioned acid and then further mixed with water to carry out the post-treatment.

The method according to any one of < 17 > and < 12 > - < 16 >, wherein the working solution after the post-treatment is stirred with pure water and allowed to stand, and the post-treatment is performed such that the pH of the separated aqueous layer becomes 7 or less.

A method for producing hydrogen peroxide by the anthraquinone method, wherein the hydrogen peroxide is produced by using the working solution treated by the method described in any one of < 1 > < 17 >.

ADVANTAGEOUS EFFECTS OF INVENTION

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

Drawings

Fig. 1 is a diagram showing an example of a manufacturing method of the present invention.

Fig. 2 is a graph showing the relationship between the concentration of amylanthrahydroquinones and the increase rate of amylanthrahydroquinones 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 examples for explaining the present invention, and are not intended to limit the present invention to the embodiments. The present invention can be implemented in various ways within a scope not departing from the gist thereof.

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

In the anthraquinone method, a working solution obtained by dissolving anthraquinones in an organic solvent is used.

As the anthraquinones to be used, anthraquinones, tetrahydroanthraquinones, alkylanthraquinone, and alkyltetrahydroanthraquinones may be mentioned. In the following, anthraquinone and alkylanthraquinone are sometimes collectively referred to as (alkyl) anthraquinone. In addition, tetrahydroanthraquinones and alkyl tetrahydroanthraquinones are sometimes collectively referred to as (alkyl) tetrahydroanthraquinones. The (alkyl) anthraquinone and the (alkyl) tetrahydroanthraquinone may each be a mixture of a plurality of (alkyl) anthraquinones and (alkyl) tetrahydroanthraquinones. As the (alkyl) anthraquinone, ethylanthraquinone, t-butylanthraquinone, pentynthraquinone, and the like can be exemplified. Examples of the (alkyl) tetrahydroanthraquinone include tetrahydroanthraquinone, ethyl tetrahydroanthraquinone, t-butyl tetrahydroanthraquinone, amyl tetrahydroanthraquinone, and the like.

The alkyl group of the anthraquinone is particularly preferably an alkyl group having 1 to 10 carbon atoms, ethyl group, butyl group or 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. Examples of benzene derivatives include pseudocumene. Examples of the polar solvent include higher alcohols such as diisobutylcarbinol, carboxylic acid esters, tetra-substituted urea, cyclic urea, trioctylphosphoric acid, and the like. The preferred organic solvent is a combination of an aromatic hydrocarbon and a higher alcohol, or a combination of an aromatic hydrocarbon and a carboxylic acid ester of cyclohexanol, alkyl cyclohexanol, or tetra-substituted urea.

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

A catalyst in which a transition metal is supported on a carrier is usually added to a working solution to be used for hydrogenation. The carrier is not particularly limited, and for example, at least one selected from silica, silica-alumina, titania, zirconia, silica-alumina composite oxide, silica-titania composite oxide, alumina-titania composite oxide, and physical mixtures thereof may be used. The support 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 from 0.2 to 2.0 ml/g. The total pore volume can be measured by mercury porosimetry.

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

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

A specific process of the anthraquinone method will be described with reference to fig. 1. In fig. 1, the movement of the working solution is shown by solid arrows and dashed arrows. The solid arrows represent the main flow of working solution in the anthraquinone process. The dashed arrow indicates the flow of the working solution, which is returned to the main flow of the anthraquinone process after being supplied to the steps of the alkali treatment and the post-treatment:

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

a part of the working solution extracted during the hydrogenation step;

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

In the anthraquinone process, first, a hydrogenation treatment is performed to hydrogenate a working solution. This hydrogenates anthraquinones in the working solution to form corresponding anthrahydroquinones (hydrogenation step). Thereafter, the obtained anthrahydroquinones are oxidized by air or an oxygen-containing gas to return them to anthraquinones, and hydrogen peroxide is generated and dissolved in the working solution (oxidation step). Then, the hydrogen peroxide produced is extracted with water, and separated from the working solution (extraction step). Thereafter, the hydrogen peroxide is supplied to a refining process and a concentration process according to conventional methods to produce a product. On the other hand, the working solution after the extraction step is supplied to the hydrogenation step, and is reused in the oxidation step and the extraction step ….

(alkali treatment)

The working solution to be used continuously contains by-products derived from anthraquinones, which are produced by side reactions, and for example, contains one or more anthraquinone derivatives 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 represents ethyl, butyl or pentyl.)

The anthraquinone derivatives described above do not have hydrogen peroxide-generating ability. Therefore, regeneration of these anthraquinones to anthraquinones having hydrogen peroxide generating ability is significant in improving the production efficiency of hydrogen peroxide production. In the present invention, the continuously used working solution is mixed with the alkali metal compound to effect the regeneration of the anthraquinones. In this specification, this regeneration treatment using an alkali metal compound is referred to as an alkali treatment.

In the present invention, it is important that the concentration of anthrahydroquinones in the working solution to be used continuously, that is, the concentration of anthrahydroquinones represented by the following general formula (1) or the following general formula (2), is less than 0.20mol/L at a stage before mixing with the alkali metal compound. This is because it has been proved through experiments that when the working solution to be treated (sometimes referred to as the treated working solution) satisfies the above conditions, the anthraquinone derivative can be efficiently regenerated into the anthraquinones, and the amount of the anthraquinones increases (refer to 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 represents ethyl, butyl or pentyl.)

As a reason why the anthrahydroquinones cannot be efficiently regenerated to the anthraquinones when the anthrahydroquinones are 0.20mol/L or more, the inventors of the present invention speculate that the anthrahydroquinones are easily dissolved in the aqueous solution of the alkali metal compound, and therefore when the anthrahydroquinones are excessive, more anthrahydroquinones are dissolved in the aqueous solution of the alkali metal compound than the anthraquinones generated in the regeneration reaction, and loss is caused, and thus the regeneration to the anthraquinones cannot be achieved.

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

Increase rate (%) of anthraquinones=amount of anthraquinones (mol/L) of working solution after treatment/total amount of anthraquinones and anthrahydroquinones (mol/L) of working solution to be treated ×100

The reason for the increase in the rate of increase of anthraquinones is not clear, but the inventors of the present invention speculate as follows. The reactivity of hydrogen added in the hydrogenation step of anthrahydroquinones is so high that hydrogen peroxide can be generated from oxygen without a catalyst, and the entire solution becomes a reducing environment. It is considered that the anthraquinone derivative (degradation product) is efficiently regenerated into anthraquinones due to the reaction of the reducing environment and the aqueous alkali solution.

The concentration of anthrahydroquinones can be measured by a gas chromatography analyzer (GC) as described in examples described later.

In the present invention, the working solution to be treated, which is the object of alkali treatment, is a solution as follows: in the hydrogen peroxide production process, a part of the working solution is extracted from the working solution at a stage other than the stage after the deoxidation 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 solutions of other steps, and thus has a problem of safety, and is not a treatment target in principle. Specifically, the working solution to be treated is a solution as follows: a part of the working solution extracted after the hydrogenation step and before the oxidation step, a part of the working solution extracted from the hydrogenation column during the hydrogenation step, a part of the working solution extracted after the extraction step and before the hydrogenation step, and the like.

When the concentration of anthrahydroquinone in the extracted working solution is too high, dilution is performed. For example, the working solution extracted after the extraction step and before the hydrogenation step does not contain anthrahydroquinones or even contains a small amount of anthrahydroquinones, and therefore the possibility of dilution is low, but the working solution extracted after the hydrogenation step and before the oxidation step is hydrogenated to produce a large amount of anthrahydroquinones, and therefore the possibility of dilution is high. 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 extracted may be appropriately determined, and is usually preferably 0.1 to 20.0%, particularly preferably 1.0 to 10.0% of the total working solution flowing. When the amount of extraction is too large, the amount of the working solution involved in the production of hydrogen peroxide decreases, and when the amount of extraction is too small, the alkali treatment effect becomes insufficient.

The alkali metal used in 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 borate 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 phenolate, potassium hydrogen phosphate, 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. Experiments have confirmed that the higher the concentration of the alkali metal compound, the higher the increase rate of the anthraquinones (not disclosed in the present specification). In addition, if the concentration is too low, when the alkali metal compound and the working solution are separated after the treatment, the density difference of the 2 solutions becomes small, and the possibility that the separation requires a long time is high. Therefore, the concentration in the aqueous solution of the alkali metal compound is preferably 0.5mol/L or more. The upper limit of the concentration is not particularly limited, and is usually 10.0mol/L.

The working solution to be treated and the aqueous alkali metal compound solution are usually mixed in an amount of the working solution to be treated to be an aqueous alkali metal compound solution=1 or more to 1 (volume), preferably 1 to 30 to 1 (volume), and particularly preferably 1 to 20 to 1 (volume).

The inventors of the present invention studied the temperature conditions at the time of mixing through experiments, and as a result, confirmed that the temperature was not affected for the alkali treatment. Therefore, the temperature conditions are not particularly limited, and the mixing may be performed at any temperature. Usually at 0 to 60 ℃.

The mixing time may be appropriately determined so that the working solution to be treated and the aqueous alkali metal compound solution can be sufficiently mixed. For example, in the case of stirring and mixing, mixing for 3 minutes or more is sufficient. In addition, in the case of mixing in a pipe using a pipe 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 have found through experiments that the mixing time is increased without affecting the increase rate of the anthraquinones, and thus the mixing may be completed at an appropriate timing.

(post-treatment)

The mixed solution of the regenerated working solution and the alkali metal compound aqueous solution is obtained through alkali treatment. The neutralization reaction of the alkali metal compound with hydrogen peroxide causes decomposition of hydrogen peroxide, and the decomposition reaction of hydrogen peroxide is absolutely to be avoided because it may cause an accident such as a severe rise in pressure or explosion in the equipment. Therefore, it is necessary to return the regeneration working solution to the hydrogen peroxide production process after the post-treatment for removing the alkali metal compound.

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

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

Examples of the acid used for the acid treatment include acids such as hydrochloric acid, sulfuric acid, nitric acid, and phosphoric acid, and nitric acid and phosphoric acid are preferable. This is because the materials of the main structural body of the hydrogen peroxide manufacturing apparatus are SUS material, aluminum material, and nitric acid and phosphoric acid are not corrosive to these materials. Further, there is no concern that the hydrogenation catalyst is poisoned by remaining in the working solution.

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

The washing with water is performed by stirring and contacting the regeneration working solution with water by a known device such as a stirrer mixer. As the "water", distilled water, ion-exchanged water, water purified by reverse osmosis or the like is preferable. The proportion of water to the regeneration 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 is appropriately determined 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 perform mixing for 1 minute or more. The washing time is not limited and may be appropriately determined. In addition, mixing in a pipe using a pipe mixer may be performed.

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

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

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

The regenerated working solution after removal of the alkali metal compound by the post-treatment is returned to the hydrogen peroxide production process. The phase of the return can be appropriately determined. The regeneration working solution contains anthrahydroquinones in addition to anthraquinones, and the anthrahydroquinones can produce hydrogen peroxide by oxidation reaction. Therefore, from the viewpoint of efficiently producing hydrogen peroxide by effectively using anthrahydroquinones produced in the hydrogenation step, it is preferable to return to 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 granular 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 working solutions of examples and comparative examples were measured for amylanthraquinone, amyltetrahydroanthraquinone and amylanthrahydroquinones (amylanthraquinone and amyltetrahydroanthrahydroquinone) by GC under the following conditions, and analyzed.

The device comprises: GC-2014 manufactured by Shimadzu corporation

A detector: hydrogen Flame Ionization Detector (FID)

Analytical chromatographic column: rtx-50 manufactured by Restek Co

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

Carrier gas: he (He)

Sample introduction portion temperature: 250 DEG C

Detector temperature: 310 DEG C

Sample introduction amount: 1 mu L

Split ratio: 50

Heating program: 110 ℃ (hold 8 minutes) → heating at 10 ℃/min→310 ℃ (hold 10 minutes)

< pH measurement >)

The alkali metal compound remaining in the post-treated regeneration working solution was determined by measuring the pH. Specifically, the working solution after the post-treatment was allowed to stand, and the pH of the separated aqueous layer was measured by a pH meter.

The device comprises: PH meter D-74 manufactured by horiba manufacturing station

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

pH correction reagent:

neutral phosphate pH Standard solution (Fuji film and Wako pure chemical industries, ltd.) pH6.86

Phthalate pH Standard solution (Fuji film and Wako pure chemical industries, ltd.) pH4.01

Borate pH Standard solution (Fuji film and Wako pure chemical industries, ltd.) pH9.18

Example 1 >

(hydrotreatment)

A working solution containing amylanthraquinone at a concentration of 0.543mol/L, amyltetrahydroanthraquinone at a concentration of 0.053mol/L, and a mixed organic solvent (pseudocumene: diisobutylmethanol=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 working solution before hydrogenation.

The working solution before hydrogenation was subjected to hydrogenation treatment to prepare a working solution containing 0.020mol/L pentylanthanon hydroquinones. In the hydrogenation treatment, 50mL of the working solution before hydrogenation and 100mg of the hydrogenation catalyst having palladium 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 (pentylanthanon concentration) was calculated using the hydrogen absorption amount. After a predetermined hydrogen absorption amount was reached, the catalyst was filtered off from the working solution by a disposable syringe and a filter cartridge to obtain a working solution subjected to hydrogenation reaction.

(alkali treatment)

The hydrogenated working solution is used as a working solution to be treated and contacted with a base. 50mL of the working solution to be treated was brought into stirring contact with 50mL of a 1mol/L aqueous sodium hydroxide solution. Nitrogen was introduced during stirring and the stirring was performed on a hot water bath at 50 ℃. After 15 minutes, stirring was stopped, and the working solution was separated from the aqueous sodium hydroxide solution by a separating funnel to obtain a regenerated working solution a.

(acid treatment)

The regenerated working solution A thus obtained was brought into contact with 50mL of 1mol/L nitric acid under stirring. Nitrogen was introduced during stirring and the stirring was performed on a hot water bath at 50 ℃. After 15 minutes, stirring was stopped, and the working solution was separated from nitric acid by a separating funnel to obtain a regenerated working solution B.

(washing)

The resulting regenerated working solution B was brought into stirring contact with 50mL of pure water. Nitrogen was introduced during stirring and the stirring was performed on a hot water bath at 50 ℃. After 15 minutes, stirring was stopped, and the working solution was separated from pure water by a separating funnel to obtain a regenerated working solution C.

Example 2 >

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

Example 3 >

A working solution to be treated containing 0.100mol/L of pentylanthanon was obtained, and a hydrotreating, alkali treatment, acid treatment and water washing were performed in the same manner as in example 1 except that the working solution to be treated was used to obtain a regenerated working solution C.

Example 4 >

A working solution to be treated containing 0.150mol/L of pentylanthanon was obtained, and hydrogenation treatment, alkali treatment, acid treatment and water washing were performed in the same manner as in example 1 except that the working solution to be treated was used to obtain a regenerated working solution C.

Example 5 >

A working solution to be treated having a concentration of pentylanthanon of 0.000mol/L was obtained, and a hydrotreating, alkali treatment, acid treatment and water washing were performed in the same manner as in example 1 except that the working solution to be treated was used to obtain a regenerated working solution C. The working solution to be treated having a concentration of pentylanthanon of 0.000mol/L was obtained by setting the hydrogen absorption amount to 0 in the hydrotreating described in example 1.

Comparative example 1 >

A working solution to be treated containing 0.200mol/L of pentylanthanon was obtained, and a hydrotreating, alkali treatment, acid treatment and water washing were performed in the same manner as in example 1 except that the working solution to be treated was used to obtain a regenerated working solution C.

Table 1 shows the concentrations of amylanthraquinone (AmAQ concentration in the table) and amyltetrahydroanthraquinone (AmAQ concentration in the table) in the working solution before hydrogenation, the working solution to be treated and the working solution for regeneration C obtained in the above examples and comparative examples. The working solution to be treated also shows a concentration of pentylanthanon hydroquinones (in the table, amHQ concentration).

The relation between the increase rate of amylanthraquinones and the concentration of amylanthrahydroquinones in the working solution to be treated is shown in FIG. 2.

The increase rate of amylanthraquinones = (AmAQ concentration in the regeneration working solution C + AmAQ concentration in the regeneration working solution C)/(AmAQ concentration in the working solution to be treated + AmAQ type 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 amylanthraquinone regeneration effect by the alkali treatment is excellent when the concentration of amylanthrahydroquinones is in the range of 0.02 to 0.10mol/L, particularly 0.05 to 0.10 mol/L. When the concentration of the pentylanthanon is 0.05 to 0.10mol/L, the hydrogenation ratio represented by the following formula is 8 to 16%.

Hydrogenation ratio (%) = concentration of pentylanthanon in treated working solution (mol/L)/total of pentynthraquinone and pentyltetrahydro anthraquinone in working solution before hydrogenation (mol/L) ×100

In the alkali treatment without pentylanthanon (no hydrogenation treatment), the pentylanthanon concentration was increased to only 0.545mol/L, and it was found that by setting the pentylanthanon concentration to the above range, a better pentylanthanon regeneration effect than the condition without pentylanthanon was obtained.

Example 6 >

Experiments were performed on the mixing with acid performed after contact with the alkali metal compound. As described above, in the hydrogen peroxide production process, when the alkali metal compound is brought into contact with hydrogen peroxide, the decomposition of hydrogen peroxide is promoted. The decomposition reaction of hydrogen peroxide may cause an accident such as a severe pressure rise and explosion in the equipment, and must be avoided. That is, the condition of contacting the working solution after contact with the alkali metal with the acid is very important for safe and stable operation of the apparatus.

(hydrotreatment)

A working solution containing amylanthraquinone at a concentration of 0.543mol/L, amyltetrahydroanthraquinone at a concentration of 0.053mol/L, and a mixed organic solvent (pseudocumene: diisobutylmethanol=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 pentylanthanon. In the hydrogenation treatment, 500mL of the working solution before hydrogenation and 1000mg of the hydrogenation catalyst having palladium 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 (pentylanthanon concentration) was calculated using the hydrogen absorption amount. After a predetermined hydrogen absorption amount was reached, the catalyst was filtered through a disposable syringe and a filter cartridge to obtain a working solution to be treated.

(alkali treatment)

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

(acid treatment)

The regenerated working solution D thus obtained was brought into contact with 50mL of 1mol/L nitric acid under stirring. Nitrogen was introduced during stirring and was carried out at 25 ℃. After 15 minutes, stirring was stopped, and the working solution was separated from nitric acid by a separating funnel to obtain a regenerated working solution E.

(washing)

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

Example 7 >

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

Example 8 >

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

Example 9 >

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

The pH measurement results for the aqueous layers obtained in examples 6 to 9 are shown in table 2 and fig. 3.

TABLE 2

In examples 6 to 9, a sufficient amount of amylanthraquinones were obtained. When the concentration of the nitric acid used for the acid treatment is 0.35mol/L or more, the pH of the pure water after the 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 the 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. Thus, in order to sufficiently remove the alkali metal compound from the regeneration working solution, the acid treatment is preferably performed using nitric acid having a concentration of more than 0.25mol/L, more preferably 0.35mol/L or more. Further, although it is considered that the effect of removing the alkali metal compound increases as the nitric acid is concentrated, it is preferable to perform the acid treatment using nitric acid having a concentration of 0.50mol/L or more and less than 3mol/L from the viewpoint of balance between the effect of removing and the cost and safety aspects.

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 demonstrate that the regeneration of anthraquinones is from by-products (anthraquinone derivatives) to anthraquinones, the following experiments were conducted.

Example 10 >

Experiments on regeneration of anthraquinones useful in the production of hydrogen peroxide were performed on alkyl hydroxyanthrone represented by the general formulae (d) to (e).

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

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

Example 11 >

Experiments were conducted on the regeneration of alkyl tetrahydroanthraquinone epoxides of the general formula (a) described above into anthraquinones useful in the production of hydrogen peroxide.

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

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

Example 12 >

Experiments were conducted on the phenomenon that alkylanthrone represented by the general formulae (b) and (c) is regenerated into anthraquinones useful for producing hydrogen peroxide.

Specifically, since alkylanthrone is generally contained in a small amount in a working solution of an actual device, an experiment was performed using (r=hydrogen) anthrone (anthrone, manufactured by fuji film and photoplethysmography, inc.) having no alkyl group. However, anthrone is described as anthrone by fuji film and photo-pure chemical company.

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 a mixed organic solvent (pseudocumene: diisobutylmethanol=60:40) was used as the working solution before hydrogenation. The concentration of Anthrone (AN) contained in the working solution and the regeneration working solution C was 0.032mol/L, and the concentration of Anthraquinone (AQ) was 0.020mol/L.

The anthrone in the regeneration working solution C decreases and the anthraquinone as a regeneration product increases. Thus, a sufficient effect of regenerating from anthrone to anthraquinone is obtained.

From examples 10 to 12 described above, it was confirmed that amyl tetrahydroanthraquinone epoxide, amyl hydroxyanthrone and anthrone were regenerated into amyl anthraquinones. However, it is presumed that the possibility that these undetermined anthraquinone byproducts are also regenerated into anthraquinones and contribute to increasing the concentration of anthraquinones in the working solution after the alkali treatment is also sufficiently present.

Example 13 >

The same experiment as in example 6 was performed 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 operations are performed.

(hydrogenation and alkali treatment)

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

(first acid treatment)

The regenerated working solution D thus obtained was brought into stirring contact with 50mL of 1.0mol/L phosphoric acid. Nitrogen was introduced during stirring and was carried out at 25 ℃. After 15 minutes, stirring was stopped, and the working solution was separated from phosphoric acid by a separating funnel to obtain a regenerated working solution E1.

(second acid treatment)

The regenerated working solution E1 thus obtained was brought into contact with 50mL of 1.00mol/L phosphoric acid under stirring. Nitrogen was introduced during stirring and was carried out at 25 ℃. After 15 minutes, stirring was stopped, and the working solution was separated from phosphoric acid by a separating funnel to obtain a regenerated working solution E2.

(washing)

The obtained regenerated working solution E2 was brought into stirring contact with 50mL of pure water. Nitrogen was introduced during stirring and was carried out at 25 ℃. After 5 minutes, stirring was stopped and the working solution was separated from the aqueous layer using a separating funnel.

Example 14 >

An alkali treatment, an acid treatment and a water washing were carried out in the same manner as in example 13 except that 0.50mol/L of phosphoric acid was used in 2 times of acid treatment, and the working solution was separated from the aqueous layer by a separating funnel.

Example 15 >

An alkali treatment, an acid treatment and a water washing were carried out in the same manner as in example 13 except that 0.25mol/L of phosphoric acid was used in 2 times of acid treatment, and the working solution was separated from the aqueous layer by a separating funnel.

Example 16 >

An alkali treatment, an acid treatment and a water washing were carried out in the same manner as in example 13 except that 0.13mol/L of phosphoric acid was used in 2 times of acid treatment, and the working solution was separated from the aqueous layer by a separating funnel.

The pH measurement results of the aqueous layers obtained in examples 13 to 16 are shown in table 3 and fig. 4.

TABLE 3

In examples 13 to 16, a sufficient amount of amylanthraquinones 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 lower than 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 is made to exceed 7, and a part of the alkali metal compound remains in the regeneration working solution. Thus, it is shown 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, although it is considered that the effect of removing the alkali metal compound increases as the nitric acid is concentrated, it is preferable to perform the acid treatment using phosphoric acid having a concentration of 0.50mol/L or more and less than 3mol/L from the viewpoint of balance between the effect of removing and the cost and safety aspects.

Claims

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

as the working solution to be treated before mixing with the alkali metal compound, a working solution having a concentration of anthrahydroquinones represented by the following general formula (1) or the following general formula (2) of 0.02mol/L or more and less than 0.20mol/L is used,

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

2. The process of claim 1, wherein:

the working solution to be treated is a part of the working solution extracted after the hydrogenation step and before the oxidation step, or a solution obtained by diluting a part of the working solution extracted after the hydrogenation step and before the oxidation step with 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 extracted after the extraction step and before the hydrogenation step.

4. A process according to any one of claims 1 to 3, wherein:

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

5. A process according to any one of claims 1 to 3, 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. A process according to any one of claims 1 to 3, wherein:

and R is ethyl, butyl or amyl.

7. A process according to any one of claims 1 to 3, wherein:

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

8. A process according to any one of claims 1 to 3, wherein:

the working solution to be treated and the aqueous solution of the alkali metal compound are mixed in an amount such that the working solution to be treated is equal to or more than 1 and equal to or more than 1 (by volume) of the aqueous solution of the alkali metal compound.

9. A process according to any one of claims 1 to 3, wherein:

the alkali metal compound is sodium hydroxide or potassium hydroxide.

10. A process according to any one of claims 1 to 3, wherein:

the alkali metal compound is sodium hydroxide,

and mixing sodium hydroxide aqueous solution with concentration of sodium hydroxide above 0.5 mol/L.

11. A process according to any one of claims 1 to 3, wherein:

the treated working solution is mixed with the aqueous solution of the alkali metal compound using a pipe mixer.

12. A process according to any one of claims 1 to 3, wherein:

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

13. The process of claim 12, wherein:

the acid is nitric acid or phosphoric acid.

14. The process of claim 12, wherein:

mixing with alkali metal compound, and further mixing with acidic aqueous solution with nitric acid or phosphoric acid concentration of above 0.20 mol/L.

15. The process of claim 12, wherein:

the mixing with the acid was performed using a stirring mixer.

16. The process of claim 12, wherein:

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

17. The process of claim 12, wherein:

the working solution after the post-treatment was stirred with pure water and allowed to stand so that the pH of the separated aqueous layer became 7 or less.

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

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