JP2019048739A - Method for preparing working solution for hydrogen peroxide production - Google Patents

Abstract

To provide for efficiently removing trioctyl phosphate in a working solution for hydrogen peroxide production.SOLUTION: A method for preparing a working solution for hydrogen peroxide production by an anthraquinone method includes: a step of collecting an aromatic solvent and anthraquinones from a working solution for hydrogen peroxide production by an anthraquinone method containing an aromatic solvent, trioctyl phosphate and anthraquinones; and a step of mixing the collected aromatic solvent and the collected anthraquinones with a polar solvent capable of dissolving anthraquinones other than trioctyl phosphate to prepare a trioctyl phosphate-non-containing working solution that does not substantially contain trioctyl phosphate.SELECTED DRAWING: None

Description

  The present invention relates to a method for preparing a working solution for hydrogen peroxide production substantially free of trioctyl phosphate, a method for removing trioctyl phosphate from a working solution for hydrogen peroxide production containing trioctyl phosphate, and the like.

  Hydrogen peroxide is used as a bleaching agent for paper, pulp, fibers and the like, a sterilizing agent and the like because it has an oxidizing power and a strong bleaching and sterilizing action. Since the decomposition products of hydrogen peroxide are water and oxygen, they are also regarded as important from the viewpoint of green chemistry, and are particularly noted as substitutes for chlorine bleach. Furthermore, the amount of hydrogen peroxide used is also increasing in the semiconductor industry such as cleaning of surfaces such as semiconductor substrates, chemical polishing of copper, tin and other copper alloy surfaces, and etching of electronic circuits. In addition, hydrogen peroxide is widely used in oxidation reactions such as epoxidation and hydroxylation, and hydrogen peroxide is an important industrial product.

  At present, the anthraquinone method is known as an industrial production method of hydrogen peroxide. In this method, anthraquinones are dissolved in an organic solvent to obtain a working solution, and in the hydrogenation step, anthraquinones are hydrogenated in the presence of a hydrogenation catalyst to form anthrahydroquinones. The anthrahydroquinones are then converted back to anthraquinones in the oxidation step, and at the same time hydrogen peroxide is generated. Hydrogen peroxide in the working solution is separated from the working solution by methods such as water extraction. The working solution from which hydrogen peroxide has been extracted is again returned to the hydrogenation step to form a circulating process. As a solvent for a working solution, a mixed solution mixed solvent of a nonpolar solvent dissolving anthraquinones and a polar solvent dissolving anthrahydroquinones is generally used. Although the solvent used for the working solution differs depending on the manufacturer of hydrogen peroxide, many plants use phosphoric acid ester (more specifically, tris (2-ethylhexyl) phosphate) as a polar solvent (patent document 1).

Chinese Patent Application No. 106044720

The properties required of the solvent used for the working solution include high solubility of anthraquinone and anthrahydroquinone, high distribution coefficient of hydrogen peroxide, chemical stability, low density, low viscosity, low toxicity and the like. It is also believed that it is the polar solvent that is more important than the nonpolar solvent that greatly affects the properties of the working solution. As a polar solvent used for working solution, alcohol (for example, diisobutyl carbinol, 2-2-ethylhexanol), tetra-substituted urea, phosphoric ester (for example, tris (2-ethylhexyl) phosphate), 2-pyrrolidone or alkyl Although cyclohexyl acetate etc. are mentioned, there exist merits and demerits in these polar solvents.
In the case of tris (2-ethylhexyl) phosphate (CAS number: 78-42-2, hereinafter sometimes referred to as trioctyl phosphate or TOP), the merit is that the solubility in water is low, etc. It is easy to obtain hydrogen peroxide with low TOC (Total Organic Carbon, total organic carbon), and the disadvantage is that acid impurities generated by decomposition become catalyst poisons, liquid-liquid separation in extraction process of working solution The tendency of poor performance, as a result of which stable operation may be difficult, the point where phosphorus-containing waste liquid is generated, the distribution coefficient of working solution is low and the concentration of extractable hydrogen peroxide is low etc. It can be mentioned.

  In recent years, in plants using trioctyl phosphate, the effects of the above disadvantages are more concerned, and in order to improve the properties of the working solution, (1) ternary solvents or multicomponent solvents of four or more components Efforts are being made such as changes to (2) development of new solvents.

Examples of the method of changing the solvent of the working solution include (i) a method of gradually replacing the solvent, (ii) a method of replacing the working solution, and (iii) a method of performing a separation operation. Regarding (i), in the actual plant, since the solvent in the working solution gradually decreases due to the entrainment to the exhaust gas in the oxidation process, etc., the operation is performed while appropriately replenishing a new solvent. The solvent composition can be gradually changed by replenishing the solvent different from the working solution in the circulation process. However, this method takes a long time to completely replace the solvent. In addition, since trioctyl phosphate is a solvent having a relatively high boiling point, substitution with a low boiling point solvent such as alcohol is difficult. As for (ii), there is a disadvantage that the cost is increased because it is necessary to prepare a new working solution. There is also the disadvantage that the useful working solution components such as nonpolar solvents and anthraquinones can not be reused. Examples of (iii) include separation by distillation, but the difference in boiling point between anthraquinones and trioctyl phosphate is small, and complete distillation is difficult.
For this reason, it is considered useful to provide a technique for efficiently removing trioctyl phosphate which is part of the composition of the working solution.
One object of the present invention is to provide a method for efficiently removing trioctyl phosphate in a working solution for producing hydrogen peroxide.

  As a result of intensive studies to solve the above problems, the present inventors have found that the hydrolysis of trioctyl phosphate in a working solution for producing hydrogen peroxide or the recrystallization of anthraquinones in a working solution for producing hydrogen peroxide from the working solution It has been found that trioctyl phosphate can be removed, leading to the present invention.

One aspect of the present invention is as follows.
[1] A method for preparing a working solution for producing hydrogen peroxide by the anthraquinone method,
Recovering the aromatic solvent and the anthraquinone from the working solution for producing hydrogen peroxide according to the anthraquinone method, which contains an aromatic solvent, trioctyl phosphate and anthraquinone;
A mixed solution of the recovered aromatic solvent, the recovered anthraquinones, and a polar solvent other than trioctyl phosphate capable of dissolving the anthrahydroquinones, and containing a trioctyl phosphate-free working solution substantially free of trioctyl phosphate And a step of preparing.
[2] A process of recovering an aromatic solvent and anthraquinones from a working solution for hydrogen peroxide production according to the anthraquinone method containing an aromatic solvent, trioctyl phosphate and anthraquinones,
(I) recovering an aromatic solvent from the working solution for producing hydrogen peroxide, removing trioctyl phosphate from the working solution after recovering the aromatic solvent by hydrolysis or recrystallization, and recovering anthraquinones;
(Ii) hydrolyzing trioctyl phosphate in the working solution for producing hydrogen peroxide, and recovering an aromatic solvent and anthraquinones from the working solution to which trioctyl phosphate is hydrolyzed;
Or
(Iii) The method according to [1], including the steps of recovering anthraquinones from the working solution for producing hydrogen peroxide by recrystallization and recovering an aromatic solvent from the working solution after recovering the anthraquinones.

[3] In the hydrogen peroxide production process according to the anthraquinone method, trioctyl phosphate in a working solution containing an aromatic solvent, trioctyl phosphate and anthraquinones is a polar solvent other than trioctyl phosphate which can dissolve anthrahydroquinones. A method to replace
Recovering at least a portion of the working solution from the hydrogen peroxide production process;
Recovering an aromatic solvent and anthraquinones from the recovered working solution;
The recovered aromatic solvent, the recovered anthraquinones, and a polar solvent other than trioctyl phosphate which can dissolve the anthrahydroquinones are mixed to prepare a trioctyl phosphate-free working solution substantially free of trioctyl phosphate. The process to
Adding the obtained trioctyl phosphate-free working solution to the hydrogen peroxide production process;
Method, including.
[4] The process of recovering an aromatic solvent and anthraquinones from the recovered working solution,
(I) recovering an aromatic solvent from the working solution, removing trioctyl phosphate from the working solution after aromatic solvent recovery by hydrolysis or recrystallization, and recovering anthraquinones;
(Ii) hydrolyzing trioctyl phosphate in the working solution and recovering an aromatic solvent and anthraquinones from the working solution in which the trioctyl phosphate is hydrolyzed, or (iii) re-reducing anthraquinones from the working solution The method according to [3], comprising the step of recovering by crystallization and recovering the aromatic solvent from the working solution after recovering the anthraquinones.

[5] [3] or [4], wherein substitution of the trioctyl phosphate with a polar solvent capable of dissolving anthrahydroquinones other than the trioctyl phosphate is performed during the continuation of the hydrogen peroxide production process Method described.
[6] The step of preparing a trioctyl phosphate-free working solution is a mixture of the recovered aromatic solvent, the recovered anthraquinones, and a polar solvent other than trioctyl phosphate which can dissolve the anthrahydroquinones, water The method according to any one of [1] to [5], which comprises the step of washing with an alkali and / or alkali.
[7] In the step of preparing a trioctyl phosphate-free working solution, the trioctyl phosphate-free working solution is adjusted to contain water at 20% to 160% of the saturated water content, from [1] to [1] The method according to any one of 6).

[8] A process of recovering an aromatic solvent by distillation from a working solution for producing hydrogen peroxide according to the anthraquinone method, which contains an aromatic solvent, trioctyl phosphate and anthraquinones,
Treating the working solution after recovery of the aromatic solvent with alkali, acid or enzyme to hydrolyze trioctyl phosphate;
Extracting anthraquinones into an organic phase from a working solution in which trioctyl phosphate is hydrolyzed;
Recovering anthraquinones by distillation;
Mixing the recovered aromatic solvent, the recovered anthraquinones, and a polar solvent other than trioctyl phosphate capable of dissolving the anthrahydroquinones to obtain a trioctyl phosphate-free working solution;
The method according to any one of [1] to [7], comprising

[9] The method according to any one of [1] to [8], wherein the hydrolysis is carried out with an aqueous inorganic base solution.
[10] The method according to [9], wherein the aqueous inorganic base solution is an aqueous sodium hydroxide solution.
[11] The method according to any one of [1] to [10], wherein the recovery of the aromatic solvent is performed by a first distillation under atmospheric pressure or lower pressure.
[12] The method according to [11], wherein the step of recovering anthraquinones by distillation is performed by distillation at 160 ° C. or higher under a pressure lower than that of the first distillation.
[13] The method according to any one of [1] to [12], wherein the removal rate of trioctyl phosphate in the step of removing trioctyl phosphate by hydrolysis or recrystallization is 1% to 100%.

[14] A working solution production system comprising a distillation column, a reaction tank and a preparation tank, wherein the distillation column comprises a distillate transport line, and the preparation tank comprises a polar solvent supply line and a trioctyl phosphate-free working solution transport line And the distillation column and the reaction vessel are in communication by the distillation raw material supply line, the distillation column and the preparation tank are in communication by the distillation aromatic solvent supply line, and (i) the distillation column is operated with trioctyl phosphate The reaction vessel further comprises a solution feed line, the reaction vessel is provided with a hydrolyzing agent feed line, and the distillation column and the reaction vessel are further communicated by a bottom residue transport line, and the distillate transport line and the preparation vessel are fed with anthraquinone Connected by a line or (ii) the reaction vessel comprises a trioctyl phosphate containing working solution feed line and a hydrolyzing agent feed line, the distillate transport line and the preparation The vessel is further in communication with a distillation anthraquinones feed line, or (iii) the distillation column further comprises a working solution feed line containing trioctyl phosphate, and the reaction vessel comprises a recrystallization solvent feed line and a waste line, The distillation column and the reaction vessel are further communicated by the bottom transportation line, and the reaction vessel and the preparation vessel are communicated by the recrystallization anthraquinones supply line, or (iv) the reaction vessel is fed with the working solution containing trioctyl phosphate. A working solution production system comprising a line, a recrystallization solvent supply line, and a waste liquid line, wherein the reaction tank and the preparation tank are in communication by the recrystallization anthraquinones supply line.
[15] The system according to [14], which is in communication with the hydrogen peroxide production apparatus by a trioctyl phosphate-containing working solution supply line and a trioctyl phosphate-free working solution transfer line.
[16] The washing tank further includes a cleaning agent supply line, a waste liquid line, and a cleaned working solution transfer line, and the preparation tank and the washing tank are in communication by a trioctyl phosphate-free working solution transfer line, 14] or the system as described in [15].

The present invention exhibits one or more of the following effects.
(1) Trioctyl phosphate can be removed from the working solution containing trioctyl phosphate by a simple method.
(2) Trioctyl phosphate can be efficiently removed from a working solution containing trioctyl phosphate.
(3) Since the trioctyl phosphate in the working solution can be replaced with another polar solvent while the hydrogen peroxide production process is in operation, the adverse effect due to the interruption of the hydrogen peroxide process does not occur.
(4) Loss of the working solution can be minimized since components other than trioctyl phosphate of the working solution in use can be reused.
(5) Inactive substances in the working solution can also be removed simultaneously.

FIG. 1 is a schematic view of an embodiment of the working solution production system of the present invention. FIG. 2 is a schematic view of another embodiment of the working solution production system of the present invention. FIG. 3 is a schematic view of another embodiment of the working solution production system of the present invention. FIG. 4 is a schematic view of another embodiment of the working solution production system of the present invention. FIG. 5 is a schematic view of another embodiment of the working solution production system of the present invention. FIG. 6 shows the total amount of 2-ethylhexanol (2-EHOH), 2-ethyl anthraquinone (EAQ) and trioctyl phosphate (TOP) after hydrolysis of a working solution containing or not containing an aromatic solvent for a predetermined time It is the graph which showed the ratio of the quantity of trioctyl phosphate (TOP) with respect to (2-EHOH + EAQ + TOP, the sum of peak areas). The diamond-shaped plot represents a working solution containing an aromatic solvent, and the square plot represents a working solution containing no aromatic solvent. FIG. 7 shows the amount of trioctyl phosphate (TOP) relative to the total amount (Total, total peak area) of substances contained in the working solution after hydrolysis of the working solution containing or not containing an aromatic solvent for a predetermined time It is the graph which showed the ratio. The diamond-shaped plot represents a working solution containing an aromatic solvent, and the square plot represents a working solution containing no aromatic solvent.

One aspect of the present invention is
Recovering the aromatic solvent and the anthraquinone from the working solution for producing hydrogen peroxide according to the anthraquinone method, which contains an aromatic solvent, trioctyl phosphate and anthraquinone;
A mixed solution of the recovered aromatic solvent, the recovered anthraquinones, and a polar solvent other than trioctyl phosphate capable of dissolving the anthrahydroquinones, and containing a trioctyl phosphate-free working solution substantially free of trioctyl phosphate And a step of preparing a working solution for hydrogen peroxide production by the anthraquinone method (hereinafter sometimes referred to as the working solution preparation method of the present invention).

The aromatic solvent contained in the working solution is not limited, for example, an aromatic hydrocarbon substituted with at least one alkyl group, in particular an alkylbenzene containing 8, 9, 10, 11 or 12 carbon atoms ( For example, trimethylbenzene containing 9 carbon atoms or the like) or a mixture thereof can be mentioned.
The anthraquinones contained in the working solution are not particularly limited as long as they can produce hydrogen peroxide by the anthraquinone method, and include anthraquinone (9,10-anthracenedione), tetrahydroanthraquinone and derivatives thereof. Derivatives of anthraquinones include, but are not limited to, for example, alkyl anthraquinones. Alkyl anthraquinone means anthraquinone substituted by at least one alkyl group. In certain embodiments, the alkyl anthraquinones include anthraquinones which are at least monosubstituted at one, two or three positions by a linear or branched aliphatic substituent containing at least one carbon atom. The alkyl substituent in the alkyl anthraquinone preferably contains 1 to 9, more preferably 1 to 6 carbon atoms. As a specific example of the alkyl anthraquinone, it is not limited, for example, methyl anthraquinone (2-methyl anthraquinone etc.), dimethyl anthraquinone (1, 3-, 2,3-, 1,4-, 2, 7-dimethyl anthraquinone etc. ), Ethyl anthraquinone (2-ethyl anthraquinone etc.), propyl anthraquinone (2- normal propyl anthraquinone, 2-isopropyl anthraquinone etc.), butyl anthraquinone (2-sec-, 2-tert-butyl anthraquinone etc.), amyl anthraquinone (2- sec-, 2-tert- amyl anthraquinone etc. etc. are mentioned. The working solution may comprise one or more anthraquinones.

  The working solution may or may not be used in the cyclic process of hydrogen peroxide production by the anthraquinone method. The process of producing hydrogen peroxide by the anthraquinone method comprises the steps of hydrogenating the working solution, oxidizing the hydrogenated working solution and extracting hydrogen peroxide from the oxidized working solution. The working solution used in the working solution preparation method does not contain hydrogen peroxide after the extraction step, or its content is extremely low even if it is contained (for example, the content is 0.35 g / L or less) Working solutions are preferred from the viewpoint of safety. The working solution used for the production of hydrogen peroxide contains an inactive substance which is by-produced along with the production of hydrogen peroxide, but such inactive substance can be removed by the working solution preparation method of the present invention.

  Polar solvents other than trioctyl phosphate which can dissolve anthrahydroquinones include, but are not limited to, alcohols (eg, diisobutyl carbinol (DIBC), 2--2-ethylhexanol), tetrasubstituted ureas (eg, tetrabutyl) Urea (TBU), 2-pyrrolidone or alkyl cyclohexyl acetate (e.g. methyl cyclohexyl acetate (MCHA)) and the like can be mentioned.

  By trioctyl phosphate-free working solution is meant a working solution which comprises polar solvents other than aromatic solvents, anthraquinones and trioctyl phosphate, which can dissolve anthrahydroquinones but is substantially free of trioctyl phosphate. If the composition is substantially free of trioctyl phosphate, is it free from trioctyl phosphate, or is it an amount that inevitably contaminates in the process of recovering the aromatic solvent and the anthraquinones? And / or demerit due to trioctyl phosphate, for example, it means that the operation of the plant, the catalyst, the adverse effect on the environment is not a problem. In a particular embodiment, the amount of trioctyl phosphate present in the trioctyl phosphate-free working solution is less than or equal to 1% by weight of the working solution, such as less than or equal to 0.75% by weight, less than or equal to 0.5% by weight. It may be 25 wt% or less, 0.1 wt% or less, 0.05 wt% or less, 0.01 wt% or less, and the like. The trioctyl phosphate-free working solution may comprise one or more anthraquinones. The trioctyl phosphate-free working solution may also comprise one or more polar solvents other than trioctyl phosphate which can dissolve the anthrahydroquinones.

  The working solution for hydrogen peroxide production according to the anthraquinone method, which comprises an aromatic solvent, trioctyl phosphate and anthraquinones, may be a working solution recycled in the hydrogen peroxide production process. By using such a working solution as a raw material, a trioctyl phosphate-free working solution can be prepared without discarding the anthraquinones and the aromatic solvent contained in the working solution.

In the working solution preparation method of the present invention, the step of recovering the aromatic solvent and the anthraquinone from the working solution for producing hydrogen peroxide by the anthraquinone method containing an aromatic solvent, trioctyl phosphate and anthraquinone,
(I) recovering an aromatic solvent from the working solution for producing hydrogen peroxide, removing trioctyl phosphate from the working solution after recovering the aromatic solvent by hydrolysis or recrystallization, and recovering anthraquinones;
(Ii) hydrolyzing trioctyl phosphate in the working solution for producing hydrogen peroxide, and recovering an aromatic solvent and anthraquinone from the working solution to which trioctyl phosphate is hydrolyzed;
Or
(Iii) The process may include the steps of recovering anthraquinones from the working solution for producing hydrogen peroxide by recrystallization and recovering an aromatic solvent from the working solution after recovering the anthraquinones.

  The recovery of the aromatic solvent in the method of preparing a working solution according to the present invention includes a working solution for producing hydrogen peroxide by the anthraquinone method containing an aromatic solvent, trioctyl phosphate and anthraquinones, a working solution in which trioctyl phosphate is hydrolyzed. Alternatively, as long as the aromatic solvent can be recovered from the working solution after recovery of the anthraquinones by recrystallization, any technique may be used, but typically, it is recovered by distillation. In certain embodiments, distillation for aromatic solvent recovery is performed at subatmospheric pressure. The distillation pressure is not particularly limited as long as the aromatic solvent can be recovered, and may be, for example, 0.5 kPa to 100 kPa, 0.8 kPa to 80 kPa, 1 kPa to 60 kPa, 2 kPa to 50 kPa, and the like. Preference is given to distillation pressures which distill off aromatic solvents but not trioctyl phosphate and anthraquinones. The distillation temperature is also not particularly limited as long as the aromatic solvent can be recovered. For example, 110 ° C. to 240 ° C., 120 ° C. to 220 ° C., 130 ° C. to 200 ° C., 140 ° C. to 190 ° C., 150 ° C. to 185 ° C. And so on. It is preferred to use a distillation temperature at which the aromatic solvent is distilled off, but trioctyl phosphate and anthraquinones are not distilled. The distillation is preferably continued until the distillation is stopped from the viewpoint of the recovery rate of the aromatic solvent and the like.

  In the step of hydrolyzing trioctyl phosphate in the working solution preparation method of the present invention, trioctyl phosphate is decomposed into dioctyl phosphate, monooctyl phosphate, phosphoric acid, 2-ethylhexanol and the like. As a method of hydrolyzing trioctyl phosphate, hydrolysis with a hydrolyzing agent such as an alkali, an acid or an enzyme can be used. The hydrolysis with an alkali can be carried out, for example, with an aqueous solution of an inorganic base. Examples of the inorganic base aqueous solution include, without limitation, aqueous solutions of sodium hydroxide, potassium hydroxide, calcium hydroxide, sodium carbonate, calcium carbonate and the like. In one aspect, the aqueous inorganic base solution comprises one or more equivalents of inorganic base per equivalent of trioctyl phosphate. The equivalent of inorganic base per equivalent of trioctyl phosphate may be, for example, 1 to 20 equivalents, 2 to 15 equivalents, 3 to 10 equivalents, 4 to 8 equivalents, etc. As the equivalent of the inorganic base per equivalent of trioctyl phosphate is higher, the hydrolysis reaction tends to be promoted. The concentration of the inorganic base aqueous solution may vary depending on the solubility of the inorganic base in water, and may be, for example, 10 to 50% by weight, 15 to 45% by weight, 20 to 40% by weight, and the like. As the concentration of the inorganic base aqueous solution is higher, the hydrolysis reaction tends to be promoted.

  The reaction temperature for hydrolysis is preferably a temperature at which the aromatic solvent or the anthraquinone does not denature, and a temperature at which the hydrolysis is performed at an appropriate rate is preferable. The reaction temperature may vary depending on the type of anthraquinone, the concentration of the reaction solution, and the like, and may be, for example, room temperature to 130 ° C., 30 ° C. to 40 ° C., 50 ° C. to 110 ° C., 60 ° C. to 100 ° C., and the like. The reaction time may vary depending on the reaction temperature, the composition of the reaction solution, the desired removal rate of trioctyl phosphate and the like, but may be 6 hours to 48 hours, 12 hours to 36 hours, 15 hours to 30 hours, and the like. The predetermined reaction temperature and the optimum reaction time in the case of using the reaction solution can be determined by periodically measuring the residual rate or the residual amount of trioctyl phosphate in the reaction liquid. Moreover, the removal rate of trioctyl phosphate can be adjusted by adjusting the reaction conditions and time of hydrolysis.

  In order to uniformly mix the inorganic base aqueous solution and the organic substance in the working solution, amphiphilic substances such as alcohol and phosphoric acid diester can be added to the reaction system. The amphiphilic substance to be added is preferably one that can be easily separated by an operation such as distillation. For example, ethyl alcohol has a large difference in boiling point with anthraquinones and 2-ethylhexanol, and can be easily distilled off by distillation after the reaction, so it can be said to be a preferable additive.

  After the hydrolysis of trioctyl phosphate, an extraction step and / or a washing step may be provided to remove impurities such as phosphates, phosphate ester decomposition products, base salts and the like remaining in the reaction system. In the subsequent steps, in order to recover the anthraquinones (anthraquinones and aromatic solvents when the reaction system contains an aromatic solvent) contained in the reaction system after hydrolysis, the anthraquinones are extracted in the extraction step and the washing step. Or, preferably, the anthraquinones and the aromatic solvent are not lost. In one embodiment, the extraction step includes adding an organic solvent and, if necessary, water to the reaction system to separate it, extracting anthraquinones into an organic phase, and recovering an organic phase containing anthraquinones. As the organic solvent, those which can easily separate from anthraquinones (or anthraquinones and an aromatic solvent) (for example, those having greatly different boiling points) are preferable. Such organic solvents include, but are not limited to, aromatic solvents such as benzene, toluene, dimethylbenzene (xylene), trimethylbenzene and the like. Liquid separation can be performed once or twice or more.

  The washing step includes washing with water, an aqueous alkali solution, an aqueous acid solution and the like. Water used for washing is preferably distilled water, ion-exchanged water, water purified by reverse osmosis or the like, but water purified by methods other than the above is also preferably used. Particularly preferred is pure water as water used for washing. As an alkali used for washing | cleaning, an alkali metal is preferable. The alkali metal used in the washing may be an alkali metal of Group Ia of the periodic table, preferably lithium, sodium or potassium. Although there is no limitation in particular in the reagent containing these, lithium hydroxide, sodium hydroxide, sodium carbonate, sodium hydrogencarbonate, sodium hydrogencarbonate, sodium borate, sodium diphosphate, sodium boron dioxide, sodium nitrite, sodium triborate, sodium phosphate 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, Examples thereof include potassium phenoxide, potassium hydrogen phosphate, potassium diphosphate and potassium stannate. The components contained in the alkaline aqueous solution are preferably lithium hydroxide, sodium hydroxide, sodium carbonate, sodium hydrogencarbonate and potassium hydroxide, and more preferably sodium hydroxide, sodium carbonate, sodium hydrogencarbonate and potassium hydroxide. Particularly preferred are sodium hydroxide, sodium carbonate and sodium hydrogen carbonate. The pH of the aqueous alkali solution containing an alkali metal is preferably 8 or more, more preferably 10 or more, and particularly preferably 12 or more. The washing can be carried out once, twice, three times or more.

In the working solution preparation method of the present invention, the reaction system after hydrolyzing trioctyl phosphate is subjected to both the extraction process and the washing process, regardless of whether the extraction process or the washing process is performed. It is also good.
In addition, after the reaction system after hydrolyzing trioctyl phosphate passes through the above-mentioned extraction step and / or washing step as necessary, anthraquinones (if the reaction system contains an aromatic solvent, anthraquinones and It may be subjected to a drying (dehydration) step to remove water before recovering the aromatic solvent). Drying can be performed by any known method, for example, dehydration with a dehydrating agent such as magnesium sulfate, sodium sulfate, calcium sulfate and the like. When a dehydrating agent is used, it is preferable to remove the dehydrating agent after the dehydration reaction. For removal of the dehydrating agent, methods such as filtration, precipitation, centrifugation and the like can be used, for example.

  A distillation step may be provided to recover anthraquinones (anthraquinones and an aromatic solvent when the reaction system contains an aromatic solvent) from the reaction system after hydrolysis of trioctyl phosphate. It is possible not only to remove decomposition products such as 2-ethylhexanol, dioctyl phosphate and monooctyl phosphate produced by hydrolysis of trioctyl phosphate by distillation, but also polymers of anthraquinone accumulated over time in working solution It is also possible to remove by-products simultaneously. The distillation step may comprise one, two or more stages of distillation. In one aspect, the distillation step comprises a one-step distillation to recover the anthraquinones. Distillation to recover the anthraquinones can be performed under distillation conditions suitable for recovery of the anthraquinones. Such distillation conditions include, for example, distillation at a temperature of 160 ° C. or higher under a pressure of 100 kpa or less, distillation at a temperature of 160 ° C. to 300 ° C. under a pressure of 0.001 kpa to 10 kpa, 0.005 kpa to 1 kpa At a temperature of 165 ° C. to 290 ° C., at a pressure of 0.008 kpa to 0.5 kpa, at a temperature of 170 ° C. to 280 ° C., at a pressure of 0.01 to 0.2 kpa And distillation at a temperature of 180 ° C. to 250 ° C., and the like. In one embodiment, which includes the step of adding an organic solvent to the reaction system after hydrolysis of trioctyl phosphate and separating the solution, the distillation step comprises a first distillation for removing the organic solvent and a recovery of the anthraquinones. And a second distillation of In another aspect, the distillation step comprises a first distillation to recover the anthraquinones and a second distillation to recover the aromatic solvent. The first distillation to recover the anthraquinones can be performed under distillation conditions suitable for recovery of the anthraquinones, non-limiting examples of such distillation conditions are as described above. Also, the second distillation to recover the aromatic solvent can be performed in the same manner as the above-described distillation for aromatic solvent recovery. Distillation can be carried out until the desired result is obtained, for example, until no distillation under given conditions, or until a predetermined amount of distillate is obtained.

  The step of removing trioctyl phosphate by recrystallization in the working solution preparation method of the present invention comprises re-reacting the working solution for hydrogen peroxide production by the anthraquinone method containing trioctyl phosphate and anthraquinones to recrystallize anthraquinones. It is heated and dissolved in a crystallization solvent and then cooled to recover recrystallized anthraquinones, while discarding non-recrystallized trioctyl phosphate. As the recrystallization solvent, a solvent having a large difference between the solubility of the anthraquinone at heating and the solubility at cooling is preferable. Non-limiting examples of recrystallization solvents include alcohol solvents (eg, lower alcohols such as methanol, ethanol, propanol, isopropanol, butanol, tert-butanol, 2-ethylhexanol, etc.), nonpolar solvents used as components of working solution (Aromatic hydrocarbons and the like) and polar solvents (TOP, diisobutylcarbinol, tetrabutyl urea, methyl cyclohexyl acetate and the like) and the like. The amount of recrystallization solvent relative to the working solution is preferably such that recrystallization of anthraquinones is performed well, for example, 1 to 20 times the volume of solvent per unit weight of working solution (eg, g / ml), It may be 2 to 15 times, 3 to 10 times, 4 to 8 times, etc. After recovering the anthraquinones by recrystallization, the recrystallization solvent may be recovered by distillation or the like and reused.

The working solution preparation method of the present invention includes the following four aspects depending on the timing of recovering the aromatic solvent and the trioctyl phosphate removal procedure.
(I) Working solution preparation method A
After recovering the aromatic solvent from the working solution, the trioctyl phosphate is removed by hydrolysis to recover the anthraquinones.
(Ii) Working solution preparation method B
After recovering the aromatic solvent from the working solution, it is recovered by recrystallizing the anthraquinones to remove trioctyl phosphate.
(Iii) Working solution preparation method C
After trioctyl phosphate in the working solution is removed by hydrolysis, the aromatic solvent and the anthraquinones are recovered.
(Iv) Working solution preparation method D
After recovery by recrystallization of the anthraquinones in the working solution, the aromatic solvent is recovered and the trioctyl phosphate is removed.

One embodiment of the working solution preparation method A comprises the steps of recovering the aromatic solvent from the working solution by distillation, and treating the working solution after recovering the aromatic solvent with alkali, acid or enzyme to hydrolyze trioctyl phosphate A step of extracting anthraquinones into an organic phase from a working solution in which trioctyl phosphate is hydrolyzed, a step of recovering the anthraquinones by distillation, a recovered aromatic solvent, a recovered anthraquinones, and trioctylate Mixing polar solvents capable of dissolving anthrahydroquinones, other than phosphate, to obtain a trioctyl phosphate-free working solution.
One embodiment of the working solution preparation method B comprises a step of recovering an aromatic solvent from the working solution by distillation, a step of adding a recrystallization solvent to the working solution after recovering the aromatic solvent, and recrystallizing and recovering anthraquinones. Mixing the recovered aromatic solvent, the recovered anthraquinones, and a polar solvent other than trioctyl phosphate capable of dissolving the anthrahydroquinones to obtain a trioctyl phosphate-free working solution.

Working Solution Preparation One embodiment of the method C comprises treating the working solution with alkali, acid or enzyme and hydrolyzing trioctyl phosphate, and from the working solution in which trioctyl phosphate is hydrolyzed, aromatic solvent and anthraquinones. Extracting the organic solvent into an organic phase, collecting and fractionating the aromatic solvent and the anthraquinone by distillation, and recovering the aromatic solvent, the recovered anthraquinone, and anthrahydroquinone other than trioctyl phosphate. Mixing a polar solvent capable of dissolving the species to obtain a trioctyl phosphate-free working solution.
One embodiment of the working solution preparation method D comprises adding a recrystallization solvent to the working solution and recrystallizing and recovering anthraquinones, and recovering the aromatic solvent by distillation from the working solution after recovery of the anthraquinones, Mixing the recovered aromatic solvent, the recovered anthraquinones, and a polar solvent other than trioctyl phosphate capable of dissolving the anthrahydroquinones to obtain a trioctyl phosphate-free working solution.
The details of each step in each of the above aspects are as described above.

The removal rate of trioctyl phosphate in the step of removing trioctyl phosphate by hydrolysis or recrystallization in the working solution preparation method of the present invention is typically 1% to 100%, preferably, for example, 10% to 100%, 20. % To 100%, 30% to 100%, 40% to 100%, 50% to 100%, 60% to 100%, 70% to 100%, 80% to 100%, 90% to 100%, 95% to It may be 100% or the like. Here, the removal rate of trioctyl phosphate can be calculated by the following equation.
Removal rate (%) = 100-(residual volume / initial volume x 100)
In the above formula, the remaining amount is the amount of trioctyl phosphate remaining in the trioctyl phosphate-free working solution obtained by the working solution preparation method of the present invention, and the initial amount is the amount before being subjected to the working solution preparation method of the present invention Each represents the amount of trioctyl phosphate contained in the working solution. The amount of trioctyl phosphate may be, for example, weight, number of moles, peak area of chromatogram, etc.

  The step of preparing the trioctyl phosphate-free working solution is a polar solvent capable of dissolving anthrahydroquinones other than the aromatic solvent, anthraquinones and trioctyl phosphate recovered as described above from the trioctyl phosphate-containing working solution. By mixing. The prepared trioctyl phosphate-free working solution can also be returned to the circulation process as a working solution of fresh composition. In the preparation of a working solution of a new composition, the concentration of anthraquinone in the working solution and the solvent composition ratio can be adjusted to any value. Here, the solvent composition ratio represents the volume ratio of the nonpolar solvent to the polar solvent. Moreover, when preparing the working solution of a new composition, you may mix and use new anthraquinones and a solvent.

  Generally, in the hydrogenation step of hydrogen peroxide production, the water content of the working solution is preferably about 50% to about 95% of the saturation concentration at the hydrogenation temperature. The regenerated working solution prepared from the distillate recovered in the distillation step may have a low water content and a low rate of hydrogenation reaction. There is also a possibility that it contains acidic impurities generated from the high boiling residue. For this reason, (i) adding water to the trioctyl phosphate-free working solution to be 20% to 160% of the saturated water content, (ii) processes other than the trioctyl phosphate-free working solution step (Iii) washing the trioctyl phosphate-free working solution with water and then returning it to the circulation process, and / or (iv) alkaline cleaning the trioctyl phosphate-free working solution with it and returning it to the circulation process Is preferred. The technique of (iv) is particularly preferable because it can remove acidic impurities in addition to the ability to prepare a trioctyl phosphate-free working solution near the saturated water content.

In one embodiment, the step of preparing a trioctyl phosphate-free working solution comprises a mixture of a recovered aromatic solvent, a recovered anthraquinone, and a polar solvent other than trioctyl phosphate capable of dissolving the anthrahydroquinones. Including washing with water and / or alkali.
The washing with alkali can be carried out by washing the mixture with an aqueous alkaline solution or the like. An alkali metal is preferable as the alkali contained in the aqueous alkali solution. The alkali metal used in the washing may be an alkali metal of Group Ia of the periodic table, preferably lithium, sodium or potassium. Although there is no limitation in particular in the reagent containing these, lithium hydroxide, sodium hydroxide, sodium carbonate, sodium hydrogencarbonate, sodium hydrogencarbonate, sodium borate, sodium diphosphate, sodium boron dioxide, sodium nitrite, sodium triborate, sodium phosphate 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, Examples thereof include potassium phenoxide, potassium hydrogen phosphate, potassium diphosphate and potassium stannate. Preferred are lithium hydroxide, sodium hydroxide, sodium carbonate, sodium hydrogencarbonate and potassium hydroxide, more preferably sodium hydroxide, sodium carbonate, sodium hydrogencarbonate and potassium hydroxide, and particularly preferably sodium hydroxide. , Sodium carbonate, sodium bicarbonate. The pH of the aqueous alkali solution containing an alkali metal is preferably 8 or more, more preferably 10 or more, and particularly preferably 12 or more.

The contact of the mixture with the aqueous alkaline solution can be carried out by bringing the aqueous alkaline solution into contact with 0.2 volume part or more of 1 volume part of the mixture. Preferably, the mixture is contacted with at least 0.3 volumes of an aqueous alkaline solution. As a method of contacting, generally known mixing means can be used. For example, there are stirring, shaking and bubbling with an inert gas, cocurrent flow and alternating current contact method, but it is not limited thereto, as long as the mixture and the aqueous alkali solution can be efficiently contacted. Moreover, there is no important upper limit in the capacity | capacitance of alkaline aqueous solution made to contact, and it can select it suitably on account of the apparatus made to contact or operation | use.
The contact time of the mixture and the aqueous alkali solution is, for example, 1 minute or more, more preferably 3 minutes or more, and particularly preferably 5 minutes or more. There is no important upper limit preferable here, and it can select suitably on the convenience of the apparatus made to contact or operation | work. The contact temperature of the mixture and the aqueous alkali solution is, for example, in the range of 0 ° C. to 70 ° C., preferably 10 ° C. to 60 ° C., particularly preferably 20 ° C. to 50 ° C. The pressure during the contact treatment of the mixture and the aqueous alkali solution is not particularly limited, but it is usually convenient to keep the pressure at normal pressure. The aqueous alkaline solution after contact is separated from the mixture and discharged. The alkaline cleaning can be performed once or more, for example, once, twice or three times or more.

Washing with water is preferably carried out with distilled water, ion-exchanged water, water purified by reverse osmosis or the like, but water purified by methods other than the above is also preferably used. In particular, pure water is preferable as water used for cleaning. The washing with water can be carried out in the same manner as the alkaline washing except that water is used as the washing medium. Therefore, the volume of water to the mixture, the method of contacting with the mixture, the contact time, the contact temperature, the contact pressure and the like are similar to those described above for the alkaline cleaning. The washing with water can be carried out one or more times, for example, once, twice or three times or more.
The washing may be performed with only water or only with alkali, or both of the water washing and the alkali washing may be performed. When washing with water and washing with alkali are both carried out, washing with water may be carried out before or after alkali washing or both before and after.

  In some embodiments, in the step of preparing the trioctyl phosphate-free working solution, the trioctyl phosphate-free working solution is adjusted to contain water at 20% to 160% of the saturated water content. The adjustment of the saturated water content can be performed by dehydration treatment, addition of water, washing with water or an aqueous alkali solution, or the like. By adjusting the water content as described above, the rate of the hydrogenation reaction of the resulting working solution can be increased.

Another aspect of the present invention is a process for hydrogen peroxide production according to the anthraquinone method, comprising dissolving trioctyl phosphate in a working solution containing an aromatic solvent, trioctyl phosphate and anthraquinones and anthrahydroquinones other than trioctyl phosphate A method of substitution with a polar solvent that can
Recovering at least a portion of the working solution from the hydrogen peroxide production process;
Recovering an aromatic solvent and anthraquinones from the recovered working solution;
The recovered aromatic solvent, the recovered anthraquinones, and a polar solvent other than trioctyl phosphate which can dissolve the anthrahydroquinones are mixed to prepare a trioctyl phosphate-free working solution substantially free of trioctyl phosphate. The process to
Adding the obtained trioctyl phosphate-free working solution to the hydrogen peroxide production process;
A method, which may hereinafter be referred to as the polar solvent displacement method of the present invention.

The step of recovering the aromatic solvent and the anthraquinone from the recovered working solution in the polar solvent displacement method of the present invention comprises the steps of
(I) recovering an aromatic solvent from the working solution, removing trioctyl phosphate from the working solution after aromatic solvent recovery by hydrolysis or recrystallization, and recovering anthraquinones;
(Ii) hydrolyzing trioctyl phosphate in the working solution and recovering an aromatic solvent and anthraquinones from the working solution in which the trioctyl phosphate is hydrolyzed, or (iii) re-reducing anthraquinones from the working solution The method may include the step of recovering by crystallization and recovering the aromatic solvent from the working solution after recovering the anthraquinones.

Recovery of aromatic solvents and anthraquinones, removal of trioctyl phosphate, and preparation of a trioctyl phosphate-free working solution in the polar solvent displacement method of the invention are as described above for the working solution preparation method of the invention.
The hydrogen peroxide production process by the anthraquinone method is well known in the art, and typically includes a step of hydrogenating the working solution, a step of oxidizing the working solution after the hydrogenation, hydrogen peroxide generated by the oxidation It includes the step of extraction into the aqueous phase. The hydrogenation of the working solution is carried out, for example, by bubbling the working solution with a hydrogen-containing gas such as hydrogen gas or a mixture of an inert gas (such as nitrogen gas) and hydrogen gas in the presence of a hydrogenation catalyst. be able to. Oxidation of the working solution after hydrogenation can be performed, for example, by bubbling the working solution with a gas containing oxygen such as air or oxygen gas. The extraction of hydrogen peroxide into the aqueous phase can be carried out, for example, by mixing the working solution after oxidation with water and separating the aqueous phase. The extracted hydrogen peroxide may then be subjected to treatments such as purification and concentration.

  Recovery of the working solution from the hydrogen peroxide production process is preferably performed at a stage after the extraction step. The working solution at this stage does not contain hydrogen peroxide, or contains very little hydrogen peroxide, and is highly safe in distillation operation and the like. Recovery of the working solution is not limited, for example, a branch is provided in a pipe for circulating the working solution from the extraction step to the hydrogenation step, and part or all of the working solution circulated therefrom is subjected to the polar solvent substitution of the present invention It can be done by introducing it into an apparatus for performing the method.

  The trioctyl phosphate-free working solution can be added to any one or more of the hydrogenation, oxidation and extraction steps involved in the hydrogen peroxide production process. Here, adding to a certain process means adding to any stage from the stage where the process before the process is completed to the stage before the process is completed. For example, adding the working solution to the hydrogenation step means adding the working solution to any stage from the stage where the extraction stage is finished to the stage before the hydrogenation stage is finished (for example, the outlet of the extractor or the hydrogenation Means to add at the entrance of the device. In a particular embodiment, the trioctyl phosphate free working solution is added to the hydrogenation step. This embodiment is advantageous in that it can take advantage of the high hydrogenation activity of the trioctyl phosphate-free working solution. As a specific example of this embodiment, the trioctyl phosphate-free working solution and the working solution in circulation are mixed before the hydrogenation apparatus (hydrogenation column), and the obtained mixed solution is introduced into the hydrogenation apparatus. To be mentioned. In another particular embodiment, the trioctyl phosphate-free working solution is returned to the oxidation step and / or the extraction step. This embodiment is advantageous when the water content of the trioctyl phosphate free working solution is low.

  In one aspect, the replacement of trioctyl phosphate with a polar solvent capable of dissolving anthrahydroquinones other than trioctyl phosphate is carried out during the continuation of the hydrogen peroxide production process. In this embodiment, a portion of the working solution is recovered from the hydrogen peroxide production process, and a trioctyl phosphate-free working solution is prepared therefrom and added to the hydrogen peroxide production process. By doing this, it is possible to replace the polar solvent in the working solution while continuing the hydrogen peroxide production process, thereby avoiding the adverse effect of the interruption of the hydrogen peroxide production process.

Another aspect of the present invention is
Recovering the aromatic solvent and the anthraquinone from the working solution for producing hydrogen peroxide according to the anthraquinone method containing an aromatic solvent, trioctyl phosphate and anthraquinone, and removing at least a part of the trioctyl phosphate;
Recovering the remaining trioctyl phosphate;
Low trioctyl phosphate with reduced trioctyl phosphate by mixing recovered trioctyl phosphate, recovered aromatic solvent, recovered anthraquinones, and polar solvents other than trioctyl phosphate capable of dissolving anthrahydroquinones And a step of preparing a phosphate working solution, and a method of preparing a working solution for hydrogen peroxide production by the anthraquinone method (hereinafter sometimes referred to as the low TOP working solution preparation method of the present invention).

The low TOP working solution preparation method of the present invention
(I) recovering an aromatic solvent from a working solution for hydrogen peroxide production according to the anthraquinone method, which contains an aromatic solvent, trioctyl phosphate and anthraquinones;
Removing a portion of trioctyl phosphate from the working solution after aromatic solvent recovery by hydrolysis or recrystallization to recover anthraquinones and remaining trioctyl phosphate;
Mixing the recovered aromatic solvent, the recovered anthraquinones, the recovered trioctyl phosphate, and a polar solvent other than trioctyl phosphate capable of dissolving the anthrahydroquinones to prepare a low trioctyl phosphate working solution;
Or or
(Ii) hydrolyzing a part of trioctyl phosphate in a working solution for producing hydrogen peroxide according to the anthraquinone method, which contains an aromatic solvent, trioctyl phosphate and anthraquinones;
Recovering the aromatic solvent, the anthraquinones and the remaining trioctyl phosphate from the working solution in which a part of the trioctyl phosphate is hydrolyzed;
Mixing the recovered aromatic solvent, the recovered anthraquinones, the recovered trioctyl phosphate, and a polar solvent other than trioctyl phosphate capable of dissolving the anthrahydroquinones to prepare a low trioctyl phosphate working solution;
Or or
(Iii) recovering anthraquinones by recrystallization from a working solution for producing hydrogen peroxide according to the anthraquinone method, which contains an aromatic solvent, trioctyl phosphate and anthraquinones;
Recovering an aromatic solvent and trioctyl phosphate from the working solution after recovery of the anthraquinones;
Mixing the recovered aromatic solvent, the recovered anthraquinones, the recovered trioctyl phosphate, and a polar solvent other than trioctyl phosphate capable of dissolving the anthrahydroquinones to prepare a low trioctyl phosphate working solution;
May be included.

  The low TOP working solution preparation method of the present invention is characterized in that the working solution preparation method of the present invention includes the step of recovering trioctyl phosphate, the working solution to be prepared is “low trioctyl phosphate working solution”, operation The steps of preparing the solution are the same except that the recovered trioctyl phosphate is mixed. Therefore, the above description of the working solution preparation method of the present invention also applies to the low TOP working solution preparation method of the present invention under the condition that these points are different.

  In the low TOP working solution preparation method of the present invention, the “low trioctyl phosphate working solution” is a working solution for hydrogen peroxide production according to the anthraquinone method, which comprises an aromatic solvent, trioctyl phosphate and anthraquinones before being subjected to the present method. It means a working solution containing a polar solvent other than trioctyl phosphate and capable of dissolving anthrahydroquinones, which has a lower concentration of trioctyl phosphate compared to (sometimes referred to as "original working solution" hereinafter) . The concentration of trioctyl phosphate in the low trioctyl phosphate working solution is, for example, 50% or less, 40% or less, 30% or less, 25% or less, 20% or less, 15% or less, 10% or less of the original working solution. % Or less. The low trioctyl phosphate working solution may also comprise one or more polar solvents other than trioctyl phosphate which can dissolve the anthrahydroquinones.

The step of recovering trioctyl phosphate in the low TOP working solution preparation method of the present invention can be performed in any manner and stage where trioctyl phosphate can be suitably recovered. The low TOP working solution preparation method of the present invention includes the following four aspects according to the timing of recovering the aromatic solvent and the trioctyl phosphate removal procedure as in the working solution preparation method of the present invention.
(I) Low TOP Working Solution Preparation Method A
After recovering the aromatic solvent from the working solution, part of the trioctyl phosphate is removed by hydrolysis to recover the anthraquinones.
(Ii) Low TOP Working Solution Preparation Method B
After recovering the aromatic solvent from the working solution, it is recovered by recrystallizing the anthraquinones to remove part of the trioctyl phosphate.
(Iii) Low TOP Working Solution Preparation Method C
A portion of the trioctyl phosphate in the working solution is removed by hydrolysis before the aromatic solvent and the anthraquinones are recovered.
(Iv) Low TOP Working Solution Preparation Method D
After recovery by recrystallizing the anthraquinones in the working solution, the aromatic solvent is recovered and some of the trioctyl phosphate is removed.

  Low TOP Working Solution Preparation Methods A and C, for example, are carried out under conditions where hydrolysis of trioctyl phosphate is not completely carried out and a desired proportion of trioctyl phosphate remains, and the remaining trioctyl phosphate is mixed with anthraquinones. It can be recovered together by distillation. Trioctyl phosphate can be distilled under the same conditions as the distillation conditions for anthraquinones, and this distillation condition is a distillation of 2-ethylhexanol or phosphate which is a hydrolyzate of trioctyl phosphate. As it differs from the output conditions, separation with these hydrolyzates is possible. The degree of hydrolysis of trioctyl phosphate can be controlled, for example, by adjusting the amount of hydrolyzing agent (eg, equivalent amount per equivalent of trioctyl phosphate), reaction temperature, reaction time, and other conditions.

In the low TOP working solution preparation method B, for example, trioctyl phosphate can be recovered by distillation or the like from a reaction solution after recovering anthraquinones by recrystallization.
In the low TOP working solution preparation method D, for example, trioctyl phosphate can be recovered by distillation or the like from a reaction solution after recovering anthraquinones by recrystallization. Although this reaction liquid contains an aromatic solvent, since the distillation conditions of trioctyl phosphate and the distillation conditions of an aromatic solvent are different, both can be recovered separately.
In the low TOP working solution preparation methods B and D, a low trioctyl phosphate working solution having a desired trioctyl phosphate content can be prepared by adjusting the mixing amount of the recovered trioctyl phosphate.

Another aspect of the present invention is that, in the hydrogen peroxide production process according to the anthraquinone method, a working solution containing an aromatic solvent, trioctyl phosphate and anthraquinones has a trioctyl phosphate concentration lower than that of the working solution, and A method of substituting a low trioctyl phosphate working solution containing a polar solvent capable of dissolving anthrahydroquinones other than octyl phosphate, wherein
Recovering at least a portion of the working solution from the hydrogen peroxide production process;
Recovering an aromatic solvent and anthraquinones from the recovered working solution to remove at least a portion of trioctyl phosphate;
Recovering the remaining trioctyl phosphate;
Low trioctyl phosphate activity reduced trioctyl phosphate by mixing recovered aromatic solvent, recovered anthraquinones, recovered trioctyl phosphate, and polar solvents other than trioctyl phosphate capable of dissolving anthrahydroquinones Preparing a solution;
Adding the resulting low trioctyl phosphate working solution to the hydrogen peroxide production process;
(Hereinafter, may be referred to as a working solution replacement method of the present invention).

In the working solution replacement method of the present invention, the steps of recovering the aromatic solvent and the anthraquinone from the recovered working solution, removing at least a part of the trioctyl phosphate, and recovering the remaining trioctyl phosphate,
(I) An aromatic solvent is recovered from the recovered working solution, and a portion of trioctyl phosphate is removed from the working solution after the aromatic solvent recovery by hydrolysis or recrystallization, and anthraquinones and remaining trioctyl phosphate are removed. Process of recovery,
(Ii) a step of hydrolyzing a part of trioctyl phosphate in the recovered working solution, and recovering an aromatic solvent, anthraquinones and remaining trioctyl phosphate from the working solution in which a part of trioctyl phosphate is hydrolyzed Or (iii) recovering the anthraquinones from the recovered working solution by recrystallization, and recovering the aromatic solvent and trioctyl phosphate from the working solution after recovering the anthraquinones.

  Recovery of aromatic solvents and anthraquinones, removal of trioctyl phosphate, and preparation of low trioctyl phosphate working solution in the working solution replacement method of the invention are as described above for the low TOP working solution preparation method of the invention. Also, recovery of the working solution from the hydrogen peroxide production process and hydrogen peroxide production process according to the anthraquinone method is achieved by the working solution replacement method according to the present invention in the trioctyl phosphate-free working solution in the polar solvent replacement method according to the present invention. Except for the low trioctyl phosphate working solution, as described above for the polar solvent displacement method of the invention.

  Another aspect of the present invention relates to a working solution production system comprising a distillation column, a reaction vessel and a preparation vessel (hereinafter sometimes referred to as "the working solution production system of the present invention"). The working solution production system of the present invention may further comprise a washing tank and / or one or more distillate tanks, in addition to the above. One aspect of the working solution production system of the present invention will be described below with reference to the drawings.

<Working solution production system A>
In FIG. 1, one aspect (working solution production system A1) of a working solution production system provided with a distillation column 101, a reaction vessel 102 and a preparation vessel 103 is described. The distillation column 101 comprises a working solution feed line 104a for containing trioctyl phosphate for distillation, a distillate transfer line 105, and a bottom discharge line 118, and the reaction vessel 102 has a working solution feed line 104b containing trioctyl phosphate for reaction , The hydrolyzing agent feed line 106, the recrystallization solvent feed line 107, and the waste liquid line 108, the preparation tank 103 comprises the polar solvent feed line 109 and the trioctyl phosphate-free working solution transport line 110, and the distillation column 101 and the reaction tank 102 are connected by the distillation raw material supply line 111 and the residue transport line 112, and the distillate transport line 105 and the preparation tank 103 are the distillation aromatic solvent supply line 113 and the distillation anthraquinones. The reaction vessel 102 and the preparation vessel 103 communicate with each other through the supply line 114, and the recrystallization anthracene It communicates by non such transport line 115. The distillation trioctyl phosphate-containing working solution supply line 104 a and the reaction trioctyl phosphate-containing working solution supply line 104 b are branched from the trioctyl phosphate-containing working solution supply line 104. Each line is also provided with a valve V. For the sake of simplicity, in FIGS. 1 to 5, the symbol “V” of the valve is attached only to the one provided in the working solution supply line 104a for distillation with trioctyl phosphate. The distillation column 101 is capable of vacuum distillation (eg, 0.1 to 15 kPa) at various temperatures (eg, 120 ° C. to 260 ° C.). The reaction vessel 102 is provided with a temperature control device, and heat dissolution of anthraquinones in a recrystallization solvent and subsequent recrystallization of anthraquinones by cooling are possible. The reaction vessel 102 is also equipped with a filter, which makes it possible to filter off the recrystallized anthraquinones.

  In the embodiment where the trioctyl phosphate is removed by hydrolysis after removing the aromatic solvent, the trioctyl phosphate-containing working solution 116 enters the distillation column 101 through the trioctyl phosphate-containing working solution feed line 104a for distillation, and the atmospheric pressure or It is subjected to a pre-distillation step under a pressure lower than that. The distilled aromatic solvent is sent to the preparation tank 103 through the distillation aromatic solvent feed line 113. The residue containing trioctyl phosphate and anthraquinones remaining in the distillation column 101 enters the reaction vessel 102 through the bottom residue transport line 112. In the reaction tank 102, trioctyl phosphate contained in the residue is hydrolyzed into 2-ethylhexanol and phosphate by the hydrolyzing agent 117 supplied from the hydrolyzing agent supply line 106. The hydrolyzate of the said residue is sent to the distillation column 101 through the distillation raw material supply line 111, and is provided to a latter stage distillation process. In the second-stage distillation step, 2-ethylhexanol is distilled by the first distillation step under atmospheric pressure or lower pressure, and then by the second distillation step under the pressure lower than the first distillation step. Distill The distilled anthraquinones are sent to the preparation tank 103 through the distillation anthraquinones supply line 114. The distillate 123 other than the anthraquinones is recovered or discharged from the distillate transport line 105, and the residue 124 is discharged from the residue discharge line 118. In the preparation tank 103, the aromatic solvent supplied from the distillation aromatic solvent supply line 113, the anthraquinones supplied from the distillation anthraquinones supply line 114, and the trioctyl phosphate supplied from the polar solvent supply line 109. A polar solvent 119 capable of dissolving other anthrahydroquinones is mixed to prepare a trioctyl phosphate-free working solution. The obtained trioctyl phosphate-free working solution 120 is sent to a trioctyl phosphate-free working solution transport line 110.

  In the above embodiment, when a part of trioctyl phosphate is removed by hydrolysis to prepare a low trioctyl phosphate working solution, the remaining dioctyl phosphate is distilled together with anthraquinones in the second distillation step. Directly to the preparation tank 103 via the distillation anthraquinones feed line 114, and the aromatic solvent fed from the distillation aromatic solvent feed line 113 and anthrales other than trioctyl phosphate fed from the polar solvent feed line 109. A low trioctyl phosphate working solution can be prepared by mixing the hydroquinones with a polar solvent 119 capable of dissolving it. The resulting low trioctyl phosphate working solution can be sent to a trioctyl phosphate free working solution transport line 110.

  In the embodiment where the trioctyl phosphate is removed by recrystallization after removing the aromatic solvent, the trioctyl phosphate-containing working solution 116 enters the distillation column 101 through the trioctyl phosphate-containing working solution feed line 104a for distillation, and It is subjected to a pre-distillation step under a pressure lower than that. The distilled aromatic solvent is sent to the preparation tank 103 through the distillation aromatic solvent feed line 113. The residue containing trioctyl phosphate and anthraquinones remaining in the distillation column 101 enters the reaction vessel 102 through the bottom residue transport line 112. In the reaction tank 102, the anthraquinones contained in the residue are recrystallized by the recrystallization solvent 121 supplied from the recrystallization solvent supply line 107, and the recrystallized anthraquinones are recovered and pass through the recrystallizing anthraquinones supply line 115. It is sent to the preparation tank 103. The components that have not been recrystallized are recovered or discharged as waste liquid 122 from the waste liquid line 108. In the preparation tank 103, the aromatic solvent supplied from the distillate aromatic solvent supply line 113, the anthraquinones supplied from the recrystallized anthraquinones supply line 115, and the trioctyl phosphate supplied from the polar solvent supply line 109. A polar solvent 119 capable of dissolving other anthrahydroquinones is mixed to prepare a trioctyl phosphate-free working solution 120. The obtained trioctyl phosphate-free working solution 120 is sent to a trioctyl phosphate-free working solution transport line 110.

  When preparing a low trioctyl phosphate working solution in the above embodiment, the above non-recrystallized component is sent to the distillation column 101 through the distillation raw material feed line 111, and trioctyl phosphate is distilled under the same distillation conditions as the anthraquinones. The solvent is distilled and sent to the preparation tank 103 via the distillation anthraquinones feed line 114, and the aromatic solvent fed from the distillation aromatic solvent feed line 113 and the anthraquinones fed from the recrystallized anthraquinones feed line 115 And a polar solvent 119 capable of dissolving anthrahydroquinones other than trioctyl phosphate supplied from the polar solvent supply line 109 can be mixed to prepare a low trioctyl phosphate working solution. The resulting low trioctyl phosphate working solution can be sent to a trioctyl phosphate free working solution transport line 110.

  In the embodiment where the trioctyl phosphate is removed by hydrolysis without removing the aromatic solvent, the trioctyl phosphate-containing working solution 116 enters the reaction vessel 102 through the reaction trioctyl phosphate-containing working solution feed line 104b. In the reaction tank 102, trioctyl phosphate contained in the working solution is hydrolyzed to 2-ethylhexanol, phosphate and the like by the hydrolyzing agent 117 supplied from the hydrolyzing agent supply line 106. The hydrolyzate of the working solution is sent to the distillation column 101 through the distillation raw material feed line 111 and subjected to a distillation process. In the distillation step, the aromatic solvent is distilled by the first distillation step under atmospheric pressure or lower pressure, and 2-ethylhexanol is removed by the second distillation step under a pressure lower than the first distillation step. The distillation is carried out and the anthraquinones are distilled out in a third distillation step under lower pressure than the second distillation step. The distilled aromatic solvent and anthraquinones are sent to the preparation tank 103 through the distillation aromatic solvent feed line 113 and the distillation anthraquinones feed line 114, respectively. In the preparation tank 103, the aromatic solvent supplied from the distillation aromatic solvent supply line 113, the anthraquinones supplied from the distillation anthraquinones supply line 114, and the trioctyl phosphate supplied from the polar solvent supply line 109. A polar solvent 19 capable of dissolving other anthrahydroquinones is mixed to prepare a trioctyl phosphate-free working solution 120. The obtained trioctyl phosphate-free working solution 120 is sent to a trioctyl phosphate-free working solution transport line 110.

  In the above embodiment, when the trioctyl phosphate is partially removed by hydrolysis to prepare a low trioctyl phosphate working solution, the third distillation step distills out the remaining trioctyl phosphate together with the anthraquinones. Directly to the preparation tank 103 via the distillation anthraquinones feed line 114, and the aromatic solvent fed from the distillation aromatic solvent feed line 113 and anthrales other than trioctyl phosphate fed from the polar solvent feed line 109. A low trioctyl phosphate working solution can be prepared by mixing the hydroquinones with a polar solvent 119 capable of dissolving it. The resulting low trioctyl phosphate working solution can be sent to a trioctyl phosphate free working solution transport line 110.

  In the embodiment where the trioctyl phosphate is removed by recrystallization without removing the aromatic solvent, the trioctyl phosphate-containing working solution 116 enters the reaction vessel 102 through the reaction trioctyl phosphate-containing working solution feed line 104b. In the reaction tank 102, the anthraquinones contained in the working solution 116 are recrystallized by the recrystallization solvent 121 supplied from the recrystallization solvent supply line 107, and the recrystallized anthraquinones are recovered, and the recrystallized anthraquinones supply line 115 , And is sent to the preparation tank 103. The components which have not been recrystallized are sent to the distillation column 101 through the distillation raw material feed line 111 and subjected to the distillation step. In the distillation step, the aromatic solvent is distilled off in a first distillation step at atmospheric pressure or lower pressure. The distilled aromatic solvent is sent to the preparation tank 103 through the distillation aromatic solvent feed line 113. In the preparation tank 103, the aromatic solvent supplied from the distillate aromatic solvent supply line 113, the anthraquinones supplied from the recrystallized anthraquinones supply line 115, and the trioctyl phosphate supplied from the polar solvent supply line 109. A polar solvent 119 capable of dissolving other anthrahydroquinones is mixed to prepare a trioctyl phosphate-free working solution 120. The obtained trioctyl phosphate-free working solution 120 is sent to a trioctyl phosphate-free working solution transport line 110.

  When preparing a low trioctyl phosphate working solution in the above embodiment, after the above first distillation step, trioctyl phosphate is distilled and distilled in the second distillation step under lower pressure than the first distillation step The aromatic solvent is fed to the preparation tank 103 via the outgoing anthraquinones feed line 114, and the aromatic solvent fed from the distillation aromatic solvent feed line 113, the anthraquinones fed from the recrystallized anthraquinones feed line 115, and the polar solvent feed The low trioctyl phosphate working solution can be prepared by mixing it with a polar solvent 119 capable of dissolving anthrahydroquinones other than trioctyl phosphate supplied from line 109. The resulting low trioctyl phosphate working solution can be sent to a trioctyl phosphate free working solution transport line 110.

<Working solution production system B>
FIG. 2 shows a working solution production system B2 further including a washing tank 201, a distillation aromatic solvent tank 202 and a distillation anthraquinones tank 203 in the working solution production system A. In the working solution production system B2, the same components as those of the working solution production system A shown in FIG. The same applies to the following working solution production systems CE.
The cleaning tank 201 includes a detergent supply line 204, a water supply line 205, a cleaned working solution transport line 206, and a waste line 207. A further structural difference between the working solution production system A and the working solution production system B2 is that in the working solution production system B, the preparation tank 103 and the washing tank 201 communicate with each other by the trioctyl phosphate-free working solution transfer line 110. Point, the distillate transport line 105 and the distillate aromatic solvent tank 202 communicate with each other by the distillate aromatic solvent transport line 208, and the distillate transport line 105 and the distillate anthraquinones tank 203 Are connected by the distillation anthraquinones transport line 209, the preparation tank 103 and the distillation aromatic solvent tank 202 are connected by the distillation aromatic solvent supply line 113, and the preparation tank 103. And the distillation anthraquinones tank 203 are connected by the distillation anthraquinones supply line 114 A.

  The difference between the operation modes of the working solution production system A and the working solution production system B2 is that in the working solution production system B2, the distillate aromatic solvent from the distillation column 101 is separated from the distillate transport line 105 and then the distillate aromatic solvent The anthraquinones distilled from the distillation column 101 are distilled from the point that they are accommodated in the distillation aromatic solvent tank 202 through the transport line 208 and then enter the preparation tank 103 through the distillation aromatic solvent feed line 113. Prepared in the preparation tank 103, being stored in the distillation anthraquinones tank 203 through the product transportation line 105 and then the distillation anthraquinones transportation line 209 and then entering the preparation tank 103 through the distillation anthraquinones supply line 114 The trioctyl phosphate-free working solution passes through the trioctyl phosphate-free working solution transport line 110. The cleaning working solution obtained by washing with the cleaning agent 210 supplied from the cleaning agent supply line 204 and / or the water 211 supplied from the water supply line 205 in the cleaning tank 201 At the point where 212 is recovered through the cleaned working solution transport line 206. The waste liquid 213 resulting from the washing is discharged from the waste liquid line 207.

In the working solution production system B2, the composition of the trioctyl phosphate-free working solution in the preparation tank 103 can be freely adjusted, and the trioctyl phosphate-free working solution from the preparation tank 103 is washed with the cleaning tank 201. By doing this, it is possible to obtain a working solution with less impurities (cleaned working solution 212).
Also in the working solution production system B2, the low trioctyl phosphate working solution can be prepared in the same manner as the working solution production system A.

<Working solution production system C>
In FIG. 3, in the working solution production system B, the working solution production system C3 in which the trioctyl phosphate-containing working solution supply line 104 and the cleaned working solution transport line 206 are in communication with the hydrogen peroxide producing device 301 is described. ing. The hydrogen peroxide production apparatus 301 includes a hydrogenation column 302, an oxidation column 303, and an extraction column 304. The washing tank 201 and the hydrogenation column 302 are in communication with each other through the cleaned working solution supply line 206, and the hydrogenation column 302 includes a hydrogenation agent supply line 305 and a hydrogenation agent circulation line 306. The hydrogenation column 302 and the oxidation column 303 are in communication with each other by a hydrogenation working solution supply line 307, and the oxidation column 303 communicates with the oxidant supply line 308. The oxidation tower 303 and the extraction tower 304 communicate with each other by the oxidation working solution supply line 310, and the extraction tower 304 comprises a water supply line 311 and a hydrogen peroxide transport line 312, and is connected to the distillation tower 101. The working solution supply line 104a for distillation containing trioctyl phosphate for distillation and the extraction column 304 are the working solution supply line containing trioctyl phosphate. It communicates by 104. The trioctyl phosphate-containing working solution supply line 104 and the cleaned working solution supply line 206 are in communication via the working solution circulation line 313 after hydrogen peroxide extraction.

  The mode of action of the working solution production system C3 is operated in that the trioctyl phosphate-containing working solution is supplied from the hydrogen peroxide producing apparatus 301 and the cleaned working solution from the cleaning tank 201 is supplied to the hydrogen peroxide producing apparatus 301 It differs from solution production system B. Further, the operation mode of the hydrogen peroxide production device 301 is as follows. The washed working solution from the washing tank 201 passes through the washed working solution transport line 206 and merges with the working solution from the working solution circulation line 313 after extraction of hydrogen peroxide and enters the hydrogenation tower 302 there, The hydrogenating agent 314 containing hydrogen from the hydrogenating agent feed line 305 is reacted to form anthrahydroquinones from anthraquinones. The unreacted hydrogenating agent 314 is repeatedly supplied to the hydrogenation tower 302 via the hydrogenating agent circulation line 306. The hydrogenated working solution enters the oxidation tower 303 through the hydrogenation working solution feed line 307, and the anthrahydroquinones are oxidized by the oxidizing agent 315 containing oxygen fed from the oxidizing agent feed line 308, and the anthraquinones and excess are mixed. This produces hydrogen oxide. Unreacted oxidant 316 is exhausted from exhaust line 309. The working solution which is oxidized and contains hydrogen peroxide enters the extraction column 304 through the oxidation working solution supply line 310, and the generated hydrogen peroxide is a hydrogen peroxide solution by the water 317 supplied from the water supply line 311. As 318, it collects from the hydrogen peroxide transport line 312. Part of the trioctyl phosphate-containing working solution after hydrogen peroxide extraction enters the distillation column 101 through the trioctyl phosphate-containing working solution feed line 104 and then the trioctyl phosphate-containing working solution feed line 104a for distillation, It passes through the trioctyl phosphate-containing working solution feed line 104 and then the hydrogen peroxide extraction working solution circulation line 313 and returns to the hydrogenation tower 302 via the washed working solution feed line 206.

Since the working solution production system C can replace trioctyl phosphate in the working solution with another polar solvent while operating the hydrogen peroxide production process, the adverse effect due to the interruption of the hydrogen peroxide process may occur. Also, since the components other than the trioctyl phosphate of the working solution in use can be reused, the loss of the working solution can be minimized. Furthermore, the working solution production system C can also be used as a hydrogen peroxide production system.
Also in the working solution production system C, the low trioctyl phosphate working solution can be prepared in the same manner as the working solution production system A.

<Working solution production system D>
FIG. 4 describes a working solution production system D4 which is particularly suitable for the removal of trioctyl phosphate by hydrolysis. The working solution production system D4 includes a distillation column 101, a reaction tank 102, a preparation tank 103, a washing tank 201, a distillation aromatic solvent tank 202, a distillation anthraquinones tank 203, a distillation additive tank 401, a distillation organic solvent tank 402 and a distillation 2-ethylhexanol tank 403 are provided. The distillation column 101 comprises a working solution feed line 104a for containing trioctyl phosphate for distillation, a distillate transport line 105 and a bottom discharge line 118, and the reaction vessel 102 contains a working solution feed line 104b for reaction trioctyl phosphate for reaction The decomposing agent supply line 106, the water supply line 405, the organic solvent supply line 406, the additive supply line 407, the detergent supply line 408, and the waste liquid line 108, and the preparation tank 103 is a polar solvent supply line 109. The cleaning tank 201 includes a detergent supply line 204, a water supply line 205, a cleaned working solution transport line 206, and a waste liquid line 207, and the distillation column 101 and the reaction tank 102 are supplied with distillation raw materials. The preparation tank 103 and the cleaning tank 201 communicate with each other by the line 111 and the bottom residue transport line 112. The distillate transport line 105 communicates with the distillate aromatic solvent tank 202 by the distillate aromatic solvent transport line 208 and communicates with the distillate transport line 105. The anthraquinones tank 203 communicates with the distillate anthraquinones transport line 209, and the distillate transport line 105 and the distillate additive tank 401 communicate with the distillate additive transport line 409, and the distillate transport line 105 communicates with the distillate transport line 105. The distillation organic solvent tank 402 is in communication with the distillation organic solvent transport line 410, and the distillate transport line 105 and the distillation 2-ethylhexanol tank 403 are in communication with the distillation 2-ethylhexanol transport line 411. The additive additive tank 401 and the additive supply line 407 are communicated by the distillate additive supply line 412 The distillation organic solvent tank 402 and the organic solvent supply line 406 are connected by a distillation organic solvent supply line 413, and the preparation tank 103 and the distillation aromatic solvent tank 202 are connected by a distillation aromatic solvent supply line 113. The preparation tank 103 and the distillation anthraquinones tank 203 communicate with each other through the distillation anthraquinones supply line 114. The distillation trioctyl phosphate-containing working solution supply line 104 a and the reaction trioctyl phosphate-containing working solution supply line 104 b are branched from the trioctyl phosphate-containing working solution supply line 104.

  In the embodiment where the trioctyl phosphate is removed by hydrolysis after removing the aromatic solvent, the trioctyl phosphate-containing working solution 116 comprises the trioctyl phosphate-containing working solution feed line 104 and then the trioctyl phosphate-containing working solution feed line 104a. It passes through to the distillation column 101 and is subjected to a pre-distillation step under atmospheric pressure or lower pressure. The distilled aromatic solvent is stored in the distillate aromatic solvent tank 202 through the distillate transport line 105 and then through the distillate aromatic solvent transport line 208. The residue containing trioctyl phosphate and anthraquinones remaining in the distillation column 101 enters the reaction vessel 102 through the bottom residue transport line 112. The hydrolyzing agent 117 is supplied to the reaction tank 102 from the hydrolyzing agent supply line 106, the additive 414 is supplied from the additive supply line 407, and trioctyl phosphate contained in the residue is 2-ethylhexanol and phosphate. And hydrolysed. The hydrolyzate obtained in the reaction tank 102 is sent to the distillation column 101 through the distillation raw material supply line 111, and the additive is distilled by atmospheric distillation. The distillated additive passes through the distillate transport line 105 and then the distillate additive transport line 409 and is stored in the distillate additive tank 401. The distillate additive contained in the distillate additive tank 401 is sent to the reaction tank 102 through the distillate additive supply line 412 and then the additive supply line 407 as necessary, and is used for the hydrolysis reaction . The residue containing the anthraquinones, 2-ethylhexanol and phosphate is returned to the reaction vessel 102 through the bottoms transportation line 112. The organic solvent 415 is supplied to the reaction tank 102 from the organic solvent supply line 406, the water 416 is supplied from the water supply line 405, the anthraquinones are extracted to the organic phase, and the aqueous phase is discharged or recovered from the waste line 108 as waste liquid 122. Be done. The organic phase remaining in the reaction tank 102 is washed by the detergent 404 supplied from the detergent supply line 408 and then dewatered, and the obtained organic phase passes through the distillation raw material supply line 111 and enters the distillation column 101, It is provided to the latter stage distillation step. In the second stage distillation step, the organic solvent is distilled by the first distillation step under atmospheric pressure or lower pressure, and then the second distillation step at a pressure lower than that of the first distillation step is used for 2-ethylhexanol. The anthraquinones are distilled off in a third distillation step under a lower pressure than the second distillation step.

  The distilled anthraquinones are stored in the distillate anthraquinones tank 203 through the distillate transportation line 105 and then the distillation anthraquinone transportation line 209. The accommodated anthraquinones are sent to the preparation tank 103 through the distillation anthraquinones supply line 114. The distilled organic solvent is stored in the distillation organic solvent tank 402 through the distillate transportation line 105 and then the distillation organic solvent transportation line 410. The stored distillate organic solvent is supplied to the reaction tank 102 through the distillate organic solvent supply line 413 and then the organic solvent supply line 406 as needed, and is used for the extraction of the hydrolyzate. The distilled 2-ethylhexanol passes through the distillate transport line 105 and then the distillation 2-ethylhexanol transport line 411 and is stored in the distillation 2-ethylhexanol tank 403. In the preparation tank 103, the aromatic solvent supplied from the distillation aromatic solvent supply line 113, the anthraquinones supplied from the distillation anthraquinones supply line 114, and the trioctyl phosphate supplied from the polar solvent supply line 109. A polar solvent 119 capable of dissolving other anthrahydroquinones is mixed to prepare a trioctyl phosphate-free working solution. The prepared trioctyl phosphate-free working solution enters the washing tank 201 through the trioctyl phosphate-free working solution transfer line 110, and the washing agent 210 supplied from the washing agent supply line 204 in the washing tank 201, and Alternatively, the washed working solution 212 washed with water 211 supplied from the water supply line 205 is recovered through the washed working solution transport line 206. The waste liquid 213 resulting from the washing is discharged from the waste liquid line 207.

  In the above embodiment, when a part of trioctyl phosphate is removed by hydrolysis to prepare a low trioctyl phosphate working solution, the remaining trioctyl phosphate is distilled together with anthraquinones in the third distillation step. It is sent to the preparation tank 103 via the distillate transport line 105, the distillate anthraquinones transport line 209, the distillate anthraquinones tank 203 and the distillate anthraquinones feed line 114 as it is, and is fed from the distillate aromatic solvent feed line 113. The low trioctyl phosphate working solution can be prepared by mixing an aromatic solvent with a polar solvent 119 capable of dissolving anthrahydroquinones other than trioctyl phosphate supplied from the polar solvent feed line 109. The obtained low trioctyl phosphate working solution can be sent to the washing tank 201 via the trioctyl phosphate-free working solution transfer line 110 and can be subjected to the washing step.

  In the embodiment where the trioctyl phosphate is removed by hydrolysis without removing the aromatic solvent, the trioctyl phosphate-containing working solution 116 is a trioctyl phosphate-containing working solution supply line 104, and then a reaction trioctyl phosphate-containing working solution supply line It enters the reaction vessel 102 through 104 b. The hydrolyzing agent 117 is supplied to the reaction tank 102 from the hydrolyzing agent supply line 106, the additive 414 is supplied from the additive supply line 407, and trioctyl phosphate contained in the residue is 2-ethylhexanol and phosphate. And hydrolysed. The hydrolyzate obtained in the reaction tank 102 is sent to the distillation column 101 through the distillation raw material supply line 111, and the additive is distilled by atmospheric distillation. The distillated additive passes through the distillate transport line 105 and then the distillate additive transport line 409 and is stored in the distillate additive tank 401. The distillate additive contained in the distillate additive tank 401 is sent to the reaction tank 102 through the distillate additive supply line 412 and then the additive supply line 407 as necessary, and is used for the hydrolysis reaction . The residue containing anthraquinones, an aromatic solvent, 2-ethylhexanol and phosphate is returned to the reaction vessel 102 through the bottoms transportation line 112. The organic solvent 415 is supplied to the reaction tank 102 from the organic solvent supply line 406, and the water 416 is supplied from the water supply line 405, the residue is dissolved, and the anthraquinones are extracted into the organic phase. It is discharged or recovered from line 108. The organic phase remaining in the reaction tank 102 is washed by the detergent 404 supplied from the detergent supply line 408 and then dewatered, and the obtained organic phase passes through the distillation raw material supply line 111 and enters the distillation column 101, It is provided to the latter stage distillation step. In the second-stage distillation step, the organic solvent, the aromatic solvent, 2-ethylhexanol and anthraquinones are fractionated. For example, when toluene is used as the organic solvent, the organic solvent is distilled by the first distillation step under atmospheric pressure or lower pressure, and then the aromatic solvent is subjected to pressure lower than the first distillation step. Distilling in a second distillation step, then 2-ethylhexanol is distilled in a third distillation step at a lower pressure than the second distillation step, and then at a lower pressure than the third distillation step Anthraquinones are distilled off in the fourth distillation step. The distilled aromatic solvent is stored in the distillate aromatic solvent tank 202 through the distillate transport line 105 and then through the distillate aromatic solvent transport line 208. The accommodated distillate aromatic solvent is sent to the preparation tank 103 through the distillate aromatic solvent feed line 113.

  The distilled anthraquinones are stored in the distillate anthraquinones tank 203 through the distillate transportation line 105 and then the distillation anthraquinone transportation line 209. The accommodated anthraquinones are sent to the preparation tank 103 through the distillation anthraquinones supply line 114. The distilled organic solvent is stored in the distillation organic solvent tank 402 through the distillate transportation line 105 and then the distillation organic solvent transportation line 410. The stored distillate organic solvent is supplied to the reaction tank 102 through the distillate organic solvent supply line 413 and then the organic solvent supply line 406 as needed, and is used for the extraction of the hydrolyzate. The distilled 2-ethylhexanol passes through the distillate transport line 105 and then the distillation 2-ethylhexanol transport line 411 and is stored in the distillation 2-ethylhexanol tank 403. In the preparation tank 103, the aromatic solvent supplied from the distillation aromatic solvent supply line 113, the anthraquinones supplied from the distillation anthraquinones supply line 114, and the trioctyl phosphate supplied from the polar solvent supply line 109. A polar solvent 119 capable of dissolving other anthrahydroquinones is mixed to prepare a trioctyl phosphate-free working solution. The prepared trioctyl phosphate-free working solution enters the washing tank 201 through the trioctyl phosphate-free working solution transfer line 110, and the washing agent 210 supplied from the washing agent supply line 204 in the washing tank 201, and Alternatively, the washed working solution 212 washed with water 211 supplied from the water supply line 205 is recovered through the washed working solution transport line 206. The waste liquid 213 resulting from the washing is discharged from the waste liquid line 207.

  In the above embodiment, when a part of trioctyl phosphate is removed by hydrolysis to prepare a low trioctyl phosphate working solution, the remaining trioctyl phosphate is distilled together with anthraquinones in the fourth distillation step. It is sent to the preparation tank 103 via the distillate transport line 105, the distillate anthraquinones transport line 209, the distillate anthraquinones tank 203 and the distillate anthraquinones feed line 114 as it is, and is fed from the distillate aromatic solvent feed line 113. The low trioctyl phosphate working solution can be prepared by mixing an aromatic solvent with a polar solvent 119 capable of dissolving anthrahydroquinones other than trioctyl phosphate supplied from the polar solvent feed line 109. The obtained low trioctyl phosphate working solution can be sent to the washing tank 201 via the trioctyl phosphate-free working solution transfer line 110 and can be subjected to the washing step.

<Working solution production system E>
FIG. 5 describes a working solution production system E5 which is particularly suitable for the removal of trioctyl phosphate by recrystallization. The working solution production system E5 has a similar structure to the working solution production system B, and comprises a distillation recrystallization solvent tank 501, a distillation recrystallization solvent transport line 502 and a distillation recrystallization solvent supply line 503. However, the distillation anthraquinones tank, the distillation anthraquinones supply line, the distillation anthraquinones transport line and the hydrolyzing agent supply line are not provided. The distillate recrystallization solvent tank 501 and the distillate transport line 105 communicate with each other by a distillate recrystallization solvent transport line 502, and the distillation recrystallization solvent tank 501 and the recrystallization solvent supply line 107 are distillated. It is connected by the recrystallization solvent supply line 503.

  In embodiments where the trioctyl phosphate is removed by recrystallization after removal of the aromatic solvent, the trioctyl phosphate containing working solution 116 comprises a trioctyl phosphate containing working solution feed line 104 followed by a trioctyl phosphate containing working solution feed line 104a. It passes through to the distillation column 101 and is subjected to a pre-distillation step under atmospheric pressure or lower pressure. The distilled aromatic solvent is accommodated in the distillation aromatic solvent tank 202 through the distillation aromatic solvent transport line 208 and then sent to the preparation tank 103 through the distillation aromatic solvent feed line 113. The residue containing trioctyl phosphate and anthraquinones remaining in the distillation column 101 enters the reaction vessel 102 through the bottom residue transport line 112. In the reaction tank 102, the anthraquinones contained in the residue are recrystallized by the recrystallization solvent 121 supplied from the recrystallization solvent supply line 107, and the recrystallized anthraquinones are recovered and pass through the recrystallizing anthraquinones supply line 115. It is sent to the preparation tank 103. The components not recrystallized are recovered or discharged as waste liquid 122 from the waste liquid line 108 or are sent to the distillation column 101 through the distillation raw material supply line 111 and subjected to a distillation process to recover the recrystallization solvent . The distilled recrystallization solvent passes through the distillate transfer line 105 and then the distillation recrystallization solvent transfer line 502, and is stored in the distillation recrystallization solvent tank 501. The distilled recrystallization solvent contained in the distillation recrystallization solvent tank 501 is sent to the reaction vessel 102 through the distillation recrystallization solvent supply line 503 and then the recrystallization solvent supply line 107 as necessary. Used for Bottom residue 124 can be discharged from bottom residue discharge line 118 or can be subjected to a distillation step to recover trioctyl phosphate. In the preparation tank 103, the aromatic solvent supplied from the distillate aromatic solvent supply line 113, the anthraquinones supplied from the recrystallized anthraquinones supply line 115, and the trioctyl phosphate supplied from the polar solvent supply line 109. A polar solvent 119 capable of dissolving other anthrahydroquinones is mixed to prepare a trioctyl phosphate-free working solution. The prepared trioctyl phosphate-free working solution enters the washing tank 201 through the trioctyl phosphate-free working solution transfer line 110, and the washing agent 210 supplied from the washing agent supply line 204 in the washing tank 201, and Alternatively, the washed working solution 212 washed with water 211 supplied from the water supply line 205 is recovered through the washed working solution transport line 206. The waste liquid 213 resulting from the washing is discharged from the waste liquid line 207.

  When preparing a low trioctyl phosphate working solution in the above embodiment, the residue remaining in the distillation column 101 after the distillation step for recovering the above recrystallization solvent is distilled under the same distillation conditions as the anthraquinones to obtain tri The octyl phosphate is distilled and sent to the preparation tank 103 via the distillation anthraquinones feed line 114, and the aromatic solvent fed from the distillation aromatic solvent feed line 113 and the recrystallized anthraquinones feed line 115 The low trioctyl phosphate working solution can be prepared by mixing the anthraquinones with a polar solvent 119 capable of dissolving anthrahydroquinones other than trioctyl phosphate supplied from the polar solvent feed line 109. The resulting low trioctyl phosphate working solution can be sent to the wash tank 201 via the trioctyl phosphate free working solution transport line 110.

  In the embodiment in which trioctyl phosphate is removed by recrystallization without removing the aromatic solvent, the trioctyl phosphate-containing working solution 116 is a trioctyl phosphate-containing working solution supply line 104 and then a reaction trioctyl phosphate-containing working solution supply line It enters the reaction vessel 102 through 104 b. In the reaction tank 102, the anthraquinones contained in the working solution 116 are recrystallized by the recrystallization solvent 121 supplied from the recrystallization solvent supply line 107, and the recrystallized anthraquinones are recovered, and the recrystallized anthraquinones supply line 115 , And is sent to the preparation tank 103. The components which have not been recrystallized are sent to the distillation column 101 through the distillation raw material feed line 111 and subjected to the distillation step. In the distillation step, the aromatic solvent is distilled off by distillation at atmospheric pressure or lower, and the recrystallization solvent is distilled off by distillation under conditions different from the aromatic solvent. The distilled recrystallization solvent passes through the distillate transfer line 105 and then the distillation recrystallization solvent transfer line 502, and is stored in the distillation recrystallization solvent tank 501. The distilled recrystallization solvent contained in the distillation recrystallization solvent tank 501 is sent to the reaction vessel 102 through the distillation recrystallization solvent supply line 503 and then the recrystallization solvent supply line 107 as necessary. Used for The distilled aromatic solvent is accommodated in the distillation aromatic solvent tank 202 through the distillation aromatic solvent transport line 208 and then sent to the preparation tank 103 through the distillation aromatic solvent feed line 113. Bottom residue 124 can be discharged from bottom residue discharge line 118 or can be subjected to a distillation step to recover trioctyl phosphate. In the preparation tank 103, the aromatic solvent supplied from the distillate aromatic solvent supply line 113, the anthraquinones supplied from the recrystallized anthraquinones supply line 115, and the trioctyl phosphate supplied from the polar solvent supply line 109. A polar solvent 119 capable of dissolving other anthrahydroquinones is mixed to prepare a trioctyl phosphate-free working solution. The prepared trioctyl phosphate-free working solution enters the washing tank 201 through the trioctyl phosphate-free working solution transfer line 110, and the washing agent 210 supplied from the washing agent supply line 204 in the washing tank 201, and Alternatively, the washed working solution 212 washed with water 211 supplied from the water supply line 205 is recovered through the washed working solution transport line 206. The waste liquid 213 resulting from the washing is discharged from the waste liquid line 207.

  When preparing the low trioctyl phosphate working solution in the above embodiment, the residue 124 remaining in the distillation column 101 after the distillation step for recovering the above aromatic solvent and recrystallization solvent is the same distillation conditions as the anthraquinones. To distill off trioctyl phosphate, which is sent to the preparation tank 103 via the distillate anthraquinones feed line 114, and the aromatic solvent fed from the distillate aromatic solvent feed line 113, and the recrystallized anthraquinones feed A low trioctyl phosphate working solution can be prepared by mixing the anthraquinones supplied from line 115 and the polar solvent 119 capable of dissolving anthrahydroquinones other than trioctyl phosphate supplied from the polar solvent supply line 109. . The resulting low trioctyl phosphate working solution can be sent to the wash tank 201 via the trioctyl phosphate free working solution transport line 110.

  The working solution production system of the present invention is not limited to the embodiment described above, and various modifications are possible within the scope of the present invention. For example, in the hydrogen peroxide production system A shown in FIG. 1, when trioctyl phosphate is exclusively removed by hydrolysis, the recrystallization solvent supply line 107 and the recrystallization anthraquinones transport line 115 are not provided, and a filter is provided. It is possible to use a non-reacted reaction vessel 102, while it is possible to dispense with the hydrolyzing agent feed line 106 and the distillate anthraquinones feed line 114 if the trioctyl phosphate is exclusively removed by recrystallization. It is. Similar modifications are possible for the hydrogen peroxide production systems B and C. In addition, the trioctyl phosphate-containing working solution supply line 104 of the working solution manufacturing system A, B, D or E and the cleaned working solution transport line 206 are connected to the hydrogen peroxide manufacturing apparatus 301 similar to the working solution manufacturing system C. It is also possible. Furthermore, in any of the working fluid production systems A to E, at least one of the lines can be provided with a pump, an additional valve, a branch line, or the valve can be removed from the line equipped with a valve, as needed. is there.

  Hereinafter, the present invention will be specifically described by way of examples, but the present invention is not limited thereto.

Example 1
<Removal of trioctyl phosphate by hydrolysis>
It was examined whether trioctyl phosphate can be removed by hydrolysis from a working solution containing anthraquinones and trioctyl phosphate.

<Analytical method>
Using gas chromatography, (A) 2-ethylanthraquinone, (B) trioctyl phosphate, and (C) 2-ethylhexanol in the working solution and the samples obtained in each operation were quantified. The analysis conditions are shown below.
・ Analyzer: Gas chromatograph GC-2014 made by Shimadzu Corporation
-Column: Agilent capillary column DB-5MS (liquid phase film thickness 1.00 μm, 0.25 mm ID x 30 m)
・ Carrier gas: He
・ Detector: FID
In addition, in the result shown below, all substances other than said (A)-(C) were described as "unknown part."

(1) Hydrolysis of working solution containing aromatic solvent In a 500 mL four-necked flask, working solution consisting of 57.1 g of pseudocumene, 12.8 g of 2-ethylanthraquinone and 25.1 g of trioctyl phosphate, and 30 wt% sodium hydroxide 46.6 g of an aqueous solution and 100.3 g of ethanol were charged. The flask was fitted with a reflux condenser, and the hydrolysis reaction was carried out while stirring at a kettle temperature of 78 ° C. During the reaction, the reaction solution was appropriately analyzed by gas chromatography. It was confirmed by gas chromatography analysis that the residual amount of trioctyl phosphate was 1 area% or less, and the reaction was completed. The residual amount of trioctyl phosphate being 1 area% or less means that the peak area of trioctyl phosphate in the chromatogram is 1% or less with respect to the total peak area.

(2) Hydrolysis of working solution containing no aromatic solvent In a 500 mL four-necked flask, a working solution consisting of 12.8 g of 2-ethylanthraquinone and 25.1 g of trioctyl phosphate, and 46.6 g of a 30 wt% aqueous sodium hydroxide solution And 100.3 g of ethanol were charged. The flask was fitted with a reflux condenser, and the hydrolysis reaction was carried out while stirring at a kettle temperature of 78 ° C. During the reaction, the reaction solution was appropriately analyzed by gas chromatography. It was confirmed by gas chromatography analysis that the residual amount of trioctyl phosphate was 1 area% or less, and the reaction was completed.

  The results of the above experiments (1) and (2) are shown in FIGS. From both figures, in both the working solution containing an aromatic solvent and the working solution without an aromatic solvent, the residual amount of trioctyl phosphate decreases with the passage of time, and in the case of a solution containing an aromatic solvent, It can be seen that the reduction rate of the remaining amount (area%) of trioctyl phosphate is smaller than the solution containing no aromatic solvent.

(3) Removal of ethanol and extraction and washing of anthraquinones The reaction liquid obtained after completion of the reaction obtained in the above (2) was subjected to distillation at 80 ° C. under normal pressure to distill off ethanol and water. Toluene and water were added to the residue to dissolve it, and after separation, the organic phase was washed three times with a 10 wt% aqueous sodium hydroxide solution. The organic phase was dried over anhydrous magnesium sulfate. After dehydration, the magnesium sulfate was removed by filtration.

(4) Recovery of Anthraquinones The filtrate obtained in the above (3) was added to an evaporator and distillation under reduced pressure (final conditions 1 kPa, 45 ° C.) was performed to distill off toluene. The composition of the residue was 12.4 g of 2-ethyl anthraquinone, 0.1 g of trioctyl phosphate, 4.1 g of 2-ethylhexanol, and 10.1 g of an unknown component. Next, vacuum distillation (final conditions: 0.67 kPa · 200 ° C.) was performed at a lower pressure and a higher temperature in a distillation apparatus to distill off 3.5 g of 2-ethylhexanol. The residue was subsequently subjected to vacuum distillation (final conditions: 80 Pa · 220 ° C.). The composition of the distillate was 10.0 g of 2-ethylanthraquinone, 0.1 g of trioctyl phosphate, 0.2 g of 2-ethylhexanol, and 0.1 g of an unknown component. The recovery rate of the 2-ethylanthraquinone (recovered amount (10.0 g) / initial amount (12.8 g) × 100) was 78%. In addition, the removal rate of trioctyl phosphate (100-(remaining amount (0.1 g) / initial amount (25.1 g) x 100)) was 99.6%.
From the above results, it became clear that trioctyl phosphate can be efficiently removed from the working solution containing anthraquinones and trioctyl phosphate.

Example 2
<Removal of trioctyl phosphate by recrystallization>
In a 500 mL flask, 200 g of aromatic hydrocarbon, 89 g of trioctyl phosphate, 28 g of 2-ethylanthraquinone, 24 g of 2-ethyltetrahydroanthraquinone and unknown components (distillate residue (by-product obtained from working solution regenerator in operation) 400 g of a working solution consisting of 59 g). The degree of vacuum was controlled to 13 kPa throughout. The temperature was raised from the room temperature to 182 ° C. in the flask. The distillation was continued until no distillation was finally obtained at 13 kPa and 182 ° C. (first distillation).
The residue obtained from the first distillation was distilled at a lower pressure than the first distillation. The degree of vacuum fluctuated between 30 Pa and 150 Pa for a while after the start of distillation, but finally stabilized at 80 Pa. The temperature was raised from the room temperature to 202 ° C. in the flask. The distillation was continued until the distillation did not finally occur at 80 Pa and 202 ° C. (second distillation).

After 32 g of the distillate obtained by the second distillation was dissolved by heating in ethanol, the mixture was naturally cooled to room temperature and crystals were precipitated. After filtration, the crystals were dried. The composition of the distillate obtained by the second distillation and the crystals recovered by recrystallization is shown below.
Recovery rate of anthraquinones by recrystallization process is 64% (total amount of recrystallized 2-ethylanthraquinone and 2-ethyltetrahydroanthraquinone (3 g + 4 g)) 2-ethylanthraquinone distilled by second distillation and 2-ethyltetrahydrofuran Total amount of anthraquinone (6 g + 5 g) x 100), removal rate of trioctyl phosphate was 100% (100-(amount of recrystallized trioctyl phosphate (0 g) / trioctyl phosphate distilled by second distillation) Amount of (18g) x 100)).

1: Working solution production system A
101: distillation column 102: reaction tank 103: preparation tank 104: working solution supply line for trioctyl phosphate 104a: working solution supply line for trioctyl phosphate for distillation 104b: working solution supply line for trioctyl phosphate for reaction 105: distillation Transport line 106: Hydrolyzing agent feed line 107: Recrystallization solvent feed line 108: Waste line 109: Polar solvent feed line 110: Trioctyl phosphate-free working solution transport line 111: Distilled raw material feed line 112: Koma residue transport line 113: Distilled aromatic solvent feed line 114: Distilled anthraquinones feed line 115: Recrystallized anthraquinones transport line 116: Working solution containing trioctyl phosphate 117: Hydrolysing agent 118: Backage discharge line 119: Polar solution Medium 120: Trioctyl phosphate-free working solution 121: Recrystallization solvent 122: Waste liquid 123: Distillate 124: Residue 2: Working solution production system B
201: Washing tank 202: Distilled aromatic solvent tank 203: Distilled anthraquinones tank 204: Detergent supply line 205: Water supply line 206: Washed working solution transport line 207: Waste line 208: Distilled aromatic solvent transport Line 209: Distilled anthraquinones transport line 210: Cleaning agent 211: Water 212: Washed working solution 213: Waste liquid 3: Working solution production system C
301: hydrogen peroxide production apparatus 302: hydrogenation tower 303: oxidation tower 304: extraction tower 305: hydrogenation agent feed line 306: hydrogenation agent circulation line 307: hydrogenation working solution feed line 308: oxidant feed line 309: Exhaust line 310: oxidation working solution supply line 311: water supply line 312: hydrogen peroxide transport line 313: working solution circulation line after hydrogen peroxide extraction 314: hydrogenating agent 315: oxidizing agent 316: unreacted oxidizing agent 317: water 318: hydrogen peroxide solution 4: working solution production system D
401: Distillation additive tank 402: Distillation organic solvent tank 403: Distillation 2-ethylhexanol tank 404: Cleaning agent 405: Water supply line 406: Organic solvent supply line 407: Additive supply line 408: Cleaning agent supply line 409: Distillation additive transport line 410: Distillation organic solvent transport line 411: Distillation 2-ethylhexanol transport line 412: Distillation additive feed line 413: Distillation organic solvent feed line 414: Additive 415: Organic solvent 416: Water 5: Working solution production system E
501: Distilled recrystallization solvent tank 502: Distilled recrystallization solvent transport line 503: Distilled recrystallization solvent supply line V: Valve

Claims (16)

A method of preparing a working solution for hydrogen peroxide production by the anthraquinone method, comprising:
Recovering the aromatic solvent and the anthraquinone from the working solution for producing hydrogen peroxide according to the anthraquinone method, which contains an aromatic solvent, trioctyl phosphate and anthraquinone;
A mixed solution of the recovered aromatic solvent, the recovered anthraquinones, and a polar solvent other than trioctyl phosphate capable of dissolving the anthrahydroquinones, and containing a trioctyl phosphate-free working solution substantially free of trioctyl phosphate And a step of preparing. The process of recovering an aromatic solvent and anthraquinones from a working solution for hydrogen peroxide production according to the anthraquinone method containing an aromatic solvent, trioctyl phosphate and anthraquinones,
(I) recovering an aromatic solvent from the working solution for producing hydrogen peroxide, removing trioctyl phosphate from the working solution after recovering the aromatic solvent by hydrolysis or recrystallization, and recovering anthraquinones;
(Ii) hydrolyzing trioctyl phosphate in the working solution for producing hydrogen peroxide, and recovering an aromatic solvent and anthraquinones from the working solution to which trioctyl phosphate is hydrolyzed;
Or
(Iii) The method according to claim 1, comprising the steps of: recovering anthraquinones from the working solution for producing hydrogen peroxide by recrystallization; and recovering an aromatic solvent from the working solution after recovering the anthraquinones. Method of replacing trioctyl phosphate in a working solution containing an aromatic solvent, trioctyl phosphate and anthraquinone in a polar solvent capable of dissolving anthrahydroquinone other than trioctyl phosphate in a hydrogen peroxide production process by anthraquinone method And
Recovering at least a portion of the working solution from the hydrogen peroxide production process;
Recovering an aromatic solvent and anthraquinones from the recovered working solution;
The recovered aromatic solvent, the recovered anthraquinones, and a polar solvent other than trioctyl phosphate which can dissolve the anthrahydroquinones are mixed to prepare a trioctyl phosphate-free working solution substantially free of trioctyl phosphate. The process to
Adding the obtained trioctyl phosphate-free working solution to the hydrogen peroxide production process. The process of recovering an aromatic solvent and anthraquinones from the recovered working solution is
(I) recovering an aromatic solvent from the working solution, removing trioctyl phosphate from the working solution after aromatic solvent recovery by hydrolysis or recrystallization, and recovering anthraquinones;
(Ii) hydrolyzing trioctyl phosphate in the working solution and recovering an aromatic solvent and anthraquinones from the working solution in which the trioctyl phosphate is hydrolyzed, or (iii) re-reducing anthraquinones from the working solution The method according to claim 3, comprising the step of recovering by crystallization and recovering the aromatic solvent from the working solution after recovering the anthraquinones.   The method according to claim 3 or 4, wherein the substitution of the trioctyl phosphate with a polar solvent capable of dissolving anthrahydroquinones other than the trioctyl phosphate is carried out during the continuation of the hydrogen peroxide production process.   The step of preparing the trioctyl phosphate-free working solution is a mixture of the recovered aromatic solvent, the recovered anthraquinones and a polar solvent other than trioctyl phosphate which can dissolve the anthrahydroquinones, water and / or water. The method according to any one of claims 1 to 5, comprising the step of washing with alkali.   The process for preparing a trioctyl phosphate-free working solution, wherein the trioctyl phosphate-free working solution is adjusted to contain water at 20% to 160% of the saturated water content. The method according to one item. Recovering the aromatic solvent by distillation from a working solution for producing hydrogen peroxide according to the anthraquinone method, which contains an aromatic solvent, trioctyl phosphate and anthraquinones;
Treating the working solution after recovery of the aromatic solvent with alkali, acid or enzyme to hydrolyze trioctyl phosphate;
Extracting anthraquinones into an organic phase from a working solution in which trioctyl phosphate is hydrolyzed;
Recovering anthraquinones by distillation;
Mixing the recovered aromatic solvent, the recovered anthraquinones, and a polar solvent other than trioctyl phosphate capable of dissolving the anthrahydroquinones to obtain a trioctyl phosphate-free working solution;
The method according to any one of claims 1 to 7, comprising   9. The method according to any one of the preceding claims, wherein the hydrolysis is carried out with an aqueous inorganic base solution.   The method according to claim 9, wherein the aqueous inorganic base solution is an aqueous sodium hydroxide solution.   11. A method according to any one of the preceding claims, wherein the recovery of the aromatic solvent is carried out by a first distillation under atmospheric pressure or lower pressure.   The method according to claim 11, wherein the step of recovering the anthraquinones by distillation is performed by distillation at 160 ° C or higher under a pressure lower than the first distillation.   The method according to any one of claims 1 to 12, wherein the removal rate of trioctyl phosphate in the step of removing trioctyl phosphate by hydrolysis or recrystallization is 1% to 100%.   A working solution production system comprising a distillation column, a reaction tank and a preparation tank, wherein the distillation column comprises a distillate transport line, and the preparation tank comprises a polar solvent feed line and a trioctyl phosphate-free working solution transport line The distillation column and the reaction vessel are in communication with each other by a distillation raw material supply line, the distillation column and the preparation tank are in communication with each other by a distillation aromatic solvent supply line, and (i) the distillation column is a working solution supply line with trioctyl phosphate. The reaction vessel is further provided with a hydrolyzing agent feed line, and the distillation column and the reaction vessel are further communicated by a bottom residue transport line, and the distillate delivery line and the preparation vessel are communicated by a distillate anthraquinones feed line Or (ii) the reaction vessel is provided with a trioctyl phosphate-containing working solution supply line and a hydrolyzing agent supply line, and the distillate transport line and the preparation vessel are (Iii) The distillation column further comprises a trioctyl phosphate-containing working solution supply line, the reaction vessel comprises a recrystallization solvent supply line and a waste line, and the distillation column and the reaction vessel And the reaction vessel and the preparation vessel are in communication with the recrystallizing anthraquinones supply line, or (iv) the reaction vessel is in recrystallization with the working solution supply line containing trioctyl phosphate. A working solution production system comprising a solvent supply line and a waste liquid line, wherein the reaction vessel and the preparation vessel are in communication via a recrystallization anthraquinones supply line.   15. The system according to claim 14, wherein the system is in communication with the hydrogen peroxide production unit by a trioctyl phosphate containing working solution supply line and a trioctyl phosphate free working solution transfer line.   15. The washing vessel according to claim 14, further comprising a washing vessel provided with a detergent supply line, a waste line and a washed working solution delivery line, wherein the preparation vessel and the washing vessel are in communication via a trioctyl phosphate-free working solution delivery line. The system according to 15.