Process for the production of hydrogen peroxide

Abstract

This invention provides a method for removing inactive substances from a working solution containing trioctyl phosphate (TOP) to obtain a high-quality regenerated working solution. A method for producing hydrogen peroxide includes: a hydrogen peroxide manufacturing step, in which a working solution containing aromatic hydrocarbons, TOP, and anthraquinones is hydrogenated and then oxidized to generate hydrogen peroxide, which is extracted from the working solution, and the working solution after hydrogen peroxide extraction is returned to the hydrogenation step for recycling; a working solution regeneration step, in which inactive substances byproducts of hydrogen peroxide generation are removed from the working solution to prepare a crude regenerated working solution; and a step of alkaline washing of the crude regenerated working solution to prepare a regenerated working solution for recycling. The working solution regeneration step includes: i) a first distillation step to recover aromatic hydrocarbons by distillation at atmospheric pressure or below; ii) a second distillation step to recover anthraquinones and TOP by distillation at an even lower pressure and above 160°C.

Description

[0001] This case is filed on the date of application. September 6, 2018 Application number is 201811036580.4 A divisional application of the patent application entitled "Method for manufacturing hydrogen peroxide". Technical Field

[0002] This invention relates to a method for manufacturing hydrogen peroxide using anthraquinones, and particularly to a method for manufacturing hydrogen peroxide including a regeneration step of a working solution. Background Technology

[0003] Hydrogen peroxide possesses oxidizing power and strong bleaching and bactericidal properties, thus it is used as a bleaching agent and bactericide for paper, pulp, and fibers. Since the decomposition products of hydrogen peroxide are water and oxygen, it is also given important significance from a green chemistry perspective, particularly as a promising alternative to chlorine-based bleaching agents. Furthermore, the use of hydrogen peroxide is gradually increasing in the semiconductor industry, including surface cleaning of semiconductor substrates, chemical polishing of copper, tin, and other copper alloy surfaces, and etching of electronic circuits. Moreover, it is widely used in oxidation reactions, such as epoxidation and hydroxylation, making hydrogen peroxide an important industrial product.

[0004] The anthraquinone process is a known industrial method for producing hydrogen peroxide. In this method, anthraquinones are dissolved in an organic solvent to obtain a working solution. In a hydrogenation step, the anthraquinones are hydrogenated in the presence of a hydrogenation catalyst to produce anthraquinones. Then, in an oxidation step, the anthraquinones are converted back to anthraquinones, simultaneously generating hydrogen peroxide. The hydrogen peroxide in the working solution is separated using methods such as water extraction. The working solution after hydrogen peroxide extraction is returned to the hydrogenation step, forming a recycling process.

[0005] In the process of repeatedly hydrogenating anthraquinones in the working solution to anthraquinones and then oxidizing them back to anthraquinones to produce hydrogen peroxide, monomeric byproducts of anthraquinones such as tetrahydroanthraquinone epoxides, tetrahydroxyanthraquinones, hydroxyanthraquinones, and anthrones, as well as anthraquinone solvadruple compounds and polymers, which do not contribute to the production of hydrogen peroxide, are generated. Deterioration of the solvent components is also generated. Such components, unrelated to the production of hydrogen peroxide, are classified as "inactive substances." The increase of these inactive substances contributes to the decrease in the concentration of the active substance anthraquinones, thus reducing the capacity of each step in the cyclic process. Therefore, a working solution with a low concentration of inactive substances and capable of maintaining a sufficiently high concentration of active substances is required (Patent Document 1).

[0006] Existing technical documents

[0007] Patent documents

[0008] Patent Document 1: WO2007 / 129769 Summary of the Invention

[0009] The technical problem that the invention aims to solve

[0010] The composition of the working solution varies depending on the hydrogen peroxide production equipment, but most commonly use working solutions containing aromatic hydrocarbons as nonpolar solvents, tri(2-ethylhexyl) phosphate (CAS No.: 78-42-2, sometimes referred to as "trioctyl phosphate" or "TOP") as polar solvents, and alkyl anthraquinones and alkyl tetrahydroanthraquinones as anthraquinones. However, in working solutions containing trioctyl phosphate as a polar solvent, no method has been reported to date for suppressing the concentration of inactive substances and maintaining the concentration of active substances at a sufficiently high level. Therefore, one object of the present invention is to provide a method for removing inactive substances from a working solution containing trioctyl phosphate used in the production of hydrogen peroxide using the anthraquinone process, and for maintaining or improving the physical properties and / or activity of the working solution.

[0011] Technical solutions for solving technical problems

[0012] To address the aforementioned issues, the inventors of this invention conducted in-depth research and discovered a method for removing byproducts from a working solution containing aromatic hydrocarbons, trioctyl phosphate, and anthraquinones. In this method, aromatic hydrocarbons are recovered by distillation at atmospheric pressure or below, followed by distillation at even lower pressure and above 160°C to recover anthraquinones and trioctyl phosphate. All recovered distillate is then reused as a working solution. Furthermore, the inventors of this invention continued their research and discovered that alkaline washing of the regenerated working solution improves hydrogenation activity.

[0013] One aspect of the present invention is as follows.

[0014] [1] A method for producing hydrogen peroxide, characterized in that it comprises:

[0015] In the hydrogen peroxide manufacturing process, a working solution containing aromatic hydrocarbons, trioctyl phosphate, and anthraquinones is hydrogenated and then oxidized to generate hydrogen peroxide. The hydrogen peroxide is then extracted from the working solution and returned to the hydrogenation process for recycling.

[0016] In the working solution regeneration process, inactive substances generated as byproducts accompanying the formation of hydrogen peroxide are removed from the working solution to prepare a crude regeneration working solution after the inactive substances have been removed; and

[0017] The process for preparing the regenerated working solution for recycling involves alkali washing of the crude regenerated working solution to prepare the regenerated working solution for recycling.

[0018] The above-mentioned working solution regeneration process includes:

[0019] i) A first distillation process that recovers aromatic hydrocarbons by distillation at or below atmospheric pressure; and

[0020] ii) Next, a second distillation process is used to recover anthraquinones and trioctyl phosphate by distillation at a lower pressure and above 160°C.

[0021] [2] The method for producing hydrogen peroxide as described in [1], wherein the pressure in the first distillation step is in the range of 1 kPa to 100 kPa.

[0022] [3] The method for producing hydrogen peroxide as described in [1] or [2], wherein the pressure in the second distillation step is below 1 kPa.

[0023] [4] The method for producing hydrogen peroxide as described in any one of [1] to [3], wherein the temperature in the second distillation step is in the range of 160°C to 300°C.

[0024] [5] The method for producing hydrogen peroxide as described in any one of [1] to [4], wherein the anthraquinones include alkyl anthraquinones and alkyl tetrahydroanthraquinones.

[0025] [6] A method for manufacturing hydrogen peroxide as described in any one of [1] to [5], wherein the method includes a step of returning the above-mentioned recycled working solution to the hydrogen peroxide manufacturing process.

[0026] [7] The method for manufacturing hydrogen peroxide as described in [6], wherein the solvent composition ratio of the crude regeneration working solution is within ±20 percentage points relative to the solvent composition ratio of the working solution circulated in the hydrogen peroxide manufacturing process.

[0027] [8] The method for manufacturing hydrogen peroxide as described in [6] or [7], wherein the concentration of anthraquinones in the crude regeneration working solution is in the range of above the concentration of anthraquinones in the working solution circulated in the hydrogen peroxide manufacturing process and below the saturation concentration of anthraquinones.

[0028] [9] The method for producing hydrogen peroxide as described in any one of [6] to [8], wherein, in the above-mentioned process for preparing the regenerated working solution for recycling, the regenerated working solution is adjusted to 20% to 160% of the saturated water content.

[0029]

[10] The method for manufacturing hydrogen peroxide as described in any one of [6] to [9], wherein the above-mentioned process for preparing the regenerated working solution for recycling further includes a process for washing the regenerated working solution after alkali cleaning with water.

[0030]

[11] A method for producing hydrogen peroxide as described in any one of [1] to

[10] , wherein the method further includes a step of separating anthraquinones and trioctyl phosphate from the distillate of the second distillation step described above.

[0031]

[12] The method for producing hydrogen peroxide as described in

[11] , wherein the above-mentioned process for separating anthraquinones and trioctyl phosphate is carried out by recrystallization.

[0032]

[13] A hydrogen peroxide manufacturing system comprising a distillation tower, a preparation tank, a cleaning tank, a hydrogenation tower, an oxidation tower, and an extraction tower, wherein,

[0033] The distillation tower has an unidentified component discharge pipeline. The distillation tower and the preparation tank are connected by a front-end distillate supply pipeline and a rear-end distillate supply pipeline. The preparation tank and the washing tank are connected by a coarse regeneration working solution supply pipeline. The washing tank is connected to an alkaline solution supply pipeline and a water supply pipeline. The washing tank has a waste liquid pipeline. The washing tank and the hydrogenation tower are connected by a circulating regeneration working solution supply pipeline. The hydrogenation tower is connected by a hydrogenating agent supply pipeline. The hydrogenation tower and the oxidation tower are connected by a hydrogenation working solution supply pipeline. The oxidation tower is connected by an oxidant supply pipeline. The oxidation tower and the extraction tower are connected by an oxidation working solution supply pipeline. The extraction tower has a hydrogen peroxide delivery pipeline. The distillation tower and the extraction tower are connected by a working solution supply pipeline after hydrogen peroxide extraction.

[0034]

[14] The system as described in

[13] further includes a front-end distillate tank, the distillation column and the front-end distillate tank are connected by a front-end distillate delivery pipeline, and the front-end distillate tank and the preparation tank are connected by a front-end distillate supply pipeline.

[0035]

[15] The system as described in

[13] further includes a downstream distillate tank, the distillation column and the downstream distillate tank are connected by a downstream distillate delivery pipeline, and the downstream distillate tank and the preparation tank are connected by a downstream distillate supply pipeline.

[0036]

[16] The system as described in

[13] further includes a recrystallization tank, which has a filter and a waste liquid line, and is connected to a recrystallization solvent supply line. The recrystallization tank and the distillation tower are connected through a downstream distillate supply line, and the recrystallization tank and the preparation tank are connected through an anthraquinone supply line.

[0037] Invention Effects

[0038] The present invention can achieve one or more of the following effects.

[0039] (1) It can remove the inactive substance from a working solution containing trioctyl phosphate as a polar solvent that has accumulated inactive substances.

[0040] (2) It can efficiently recover anthraquinones, which are active substances, from working solutions containing trioctyl phosphate as a polar solvent and reuse them.

[0041] (3) By reducing inactive substances in the circulating working solution, the efficiency of each process in the production of hydrogen peroxide can be maintained at a high level.

[0042] (4) It can maintain the viscosity of the circulating working solution at a low level.

[0043] (5) It can maintain the hydrogenation activity of the circulating working solution at a high level.

[0044] (6) It can be applied to working solutions containing trioctyl phosphate that are frequently used, thus having a wide range of applications and is expected to make a significant contribution to improving the efficiency of hydrogen peroxide production. Attached Figure Description

[0045] Figure 1 This is a schematic diagram of one embodiment of the hydrogen peroxide manufacturing system of the present invention.

[0046] Figure 2 This is a schematic diagram of one embodiment of the hydrogen peroxide manufacturing system of the present invention, which includes a recrystallization tank.

[0047] Symbol Explanation

[0048] 1: Distillation column; 2: Preparation tank; 3: Washing tank; 4: Hydrogenation column; 5: Oxidation column; 6: Extraction column; 7: Distillate conveying line; 7a: Front-end distillate conveying line; 7b: Back-end distillate conveying line; 7c: Top distillate conveying line; 7d: Recrystallization solvent conveying line; 8: Unidentified component discharge line; 9: Front-end distillate tank; 10: Back-end distillate tank; 11: Front-end distillate supply line; 12: Back-end distillate supply line; 13: Crude regeneration working solution supply line; 14: Alkali solution supply line; 15: Water supply line; 16: Regeneration working solution supply line for circulation; 17: Waste liquid line; 18: Hydrogenating agent circulation line; 19: Hydrogenation 20: Hydrogenation working solution supply line; 21: Oxidant supply line; 22: Exhaust line; 23: Oxidation working solution supply line; 24: Water supply line; 25: Hydrogen peroxide delivery line; 26: Working solution supply line after hydrogen peroxide extraction; 27: Circulation line for working solution after hydrogen peroxide extraction; 28: Unknown component; 29: Alkaline solution; 30: Water; 31: Waste liquid; 32: Hydrogenating agent; 33: Oxidant; 34: Unreacted oxidant; 35: Water; 36: Hydrogen peroxide water; 37: Recrystallization tank; 38: Recrystallization solvent tank; 39: Recrystallization solvent supply line; 40: Anthraquinone supply line; 41: Waste liquid line; 42: Filtrate delivery line; V: Valve. Detailed Implementation

[0049] One aspect of the present invention relates to a method for producing hydrogen peroxide (hereinafter sometimes referred to as "the method for producing hydrogen peroxide of the present invention"), characterized in that it comprises:

[0050] The hydrogen peroxide manufacturing process involves hydrogenating (reducing) a working solution containing aromatic hydrocarbons, trioctyl phosphate, and anthraquinones, followed by oxidation to generate hydrogen peroxide. The hydrogen peroxide is then extracted from the working solution and returned to the hydrogenation process for recycling.

[0051] In the working solution regeneration process, inactive substances generated as byproducts accompanying the formation of hydrogen peroxide are removed from the working solution to prepare a crude regeneration working solution after the inactive substances have been removed; and

[0052] The process for preparing the regenerated working solution for recycling involves alkali washing of the crude regenerated working solution to prepare the regenerated working solution for recycling.

[0053] The above-mentioned working solution regeneration process includes:

[0054] i) A first distillation process that recovers aromatic hydrocarbons by distillation at or below atmospheric pressure; and

[0055] ii) Next, a second distillation process is used to recover anthraquinones and trioctyl phosphate by distillation at a lower pressure and above 160°C.

[0056] The aromatic hydrocarbon contained in the working solution is not limited, and examples include aromatic hydrocarbons with at least one alkyl substituted, particularly alkylbenzenes containing 8, 9, 10, 11, or 12 carbon atoms (e.g., trimethylbenzene containing 9 carbon atoms), or mixtures thereof, etc., preferably compounds capable of dissolving anthraquinone. In a particular manner, the aromatic hydrocarbon is selected from a mixture of solvents having 10 carbon atoms and a mixture of solvents having 9 carbon atoms (e.g., a mixture of isopropylbenzene isomers). Trioctyl phosphate, as a polar solvent, is a compound having the following structure.

[0057]

[0058] The working solution contains at least one of the following anthraquinones capable of producing hydrogen peroxide via the anthraquinone process: 9,10-anthraquinone, tetrahydroanthraquinone, and their derivatives. The derivatives of anthraquinones capable of producing hydrogen peroxide are not limited; for example, alkylanthraquinones can be listed. Alkylanthraquinones refer to anthraquinones with at least one alkyl group substituted. In a particular embodiment, alkylanthraquinones include anthraquinones in which at least one of the 1, 2, or 3 positions is substituted by a straight-chain or branched aliphatic substituent containing at least one carbon atom. The alkyl substituents in alkylanthraquinones preferably contain 1 to 9, more preferably 1 to 6 carbon atoms. Specific examples of alkylanthraquinones are not limited, but can include methylanthraquinones (such as 2-methylanthraquinone), dimethylanthraquinones (such as 1,3-dimethylanthraquinone, 2,3-dimethylanthraquinone, 1,4-dimethylanthraquinone, 2,7-dimethylanthraquinone), ethylanthraquinones (such as 2-ethylanthraquinone), propylanthraquinones (such as 2-n-propylanthraquinone, 2-isopropylanthraquinone), butylanthraquinones (such as 2-sec-butylanthraquinone, 2-tert-butylanthraquinone), and pentylanthraquinones (such as 2-sec-pentylanthraquinone, 2-tert-pentylanthraquinone). Preferred alkylanthraquinones include ethylanthraquinone, pentylanthraquinone, or mixtures thereof. The concentration of alkylanthraquinones in the working solution can be controlled according to the process conditions, for example, within a concentration range of 0.4 to 1.0 mol / L.

[0059] The term "tetrahydroanthraquinone" is not limited to a derivative capable of generating hydrogen peroxide; examples include alkyltetrahydroanthraquinones. Alkyltetrahydroanthraquinones refer to tetrahydroanthraquinones having at least one alkyl group substituted. In certain embodiments, alkyltetrahydroanthraquinones include tetrahydroanthraquinones in which at least one of the 1, 2, or 3 positions is substituted by a straight-chain or branched aliphatic substituent containing at least one carbon atom. The alkyl substituent in alkyltetrahydroanthraquinones preferably contains 1 to 9, more preferably 1 to 6 carbon atoms. Specific examples of alkyltetrahydroanthraquinones are not limited, and examples include methyltetrahydroanthraquinone (such as 2-methyltetrahydroanthraquinone), dimethyltetrahydroanthraquinone (such as 1,3-dimethyltetrahydroanthraquinone, 2,3-dimethyltetrahydroanthraquinone, 1,4-dimethyltetrahydroanthraquinone, 2,7-dimethyltetrahydroanthraquinone), ethyltetrahydroanthraquinone (such as 2-ethyltetrahydroanthraquinone), propyltetrahydroanthraquinone (such as 2-n-propyltetrahydroanthraquinone, 2-isopropyltetrahydroanthraquinone), butyltetrahydroanthraquinone (such as 2-sec-butyltetrahydroanthraquinone, 2-tert-butyltetrahydroanthraquinone), and pentyltetrahydroanthraquinone (such as 2-sec-pentyltetrahydroanthraquinone, 2-tert-pentyltetrahydroanthraquinone). Preferred alkyltetrahydroanthraquinones include ethyltetrahydroanthraquinone, pentyltetrahydroanthraquinone, or mixtures thereof.

[0060] In one embodiment, the working solution contains a combination of alkylanthraquinone and alkyltetrahydroanthraquinone. The molar ratio of alkylanthraquinone to alkyltetrahydroanthraquinone in this combination is not particularly limited, and is expressed as alkylanthraquinone:alkyltetrahydroanthraquinone, preferably 0.05:1 to 100:1, more preferably 0.1:1 to 75:1, and even more preferably 0.2:1 to 50:1. Furthermore, the weight ratio of alkylanthraquinone to alkyltetrahydroanthraquinone is not particularly limited, and is expressed as alkylanthraquinone:alkyltetrahydroanthraquinone, preferably 0.05:1 to 100:1, more preferably 0.1:1 to 75:1, and even more preferably 0.2:1 to 50:1. A particularly preferred combination of alkylanthraquinone and alkyltetrahydroanthraquinone is a combination of ethylanthraquinone and ethyltetrahydroanthraquinone.

[0061] The hydrogen peroxide manufacturing process can be carried out according to known methods using the anthraquinone process. The hydrogen peroxide manufacturing process typically includes a step of hydrogenating the working solution, a step of oxidizing the hydrogenated working solution, and a step of extracting the hydrogen peroxide generated by oxidation into the aqueous phase. Hydrogenation of the working solution can be performed, for example, by bubbling the working solution with a hydrogen-containing gas such as hydrogen or a mixture of hydrogen and an inert gas (such as nitrogen) in the presence of a hydrogenation catalyst. Oxidation of the hydrogenated working solution can be performed, for example, by bubbling the working solution with an oxygen-containing gas such as air or oxygen. Extraction of hydrogen peroxide into the aqueous phase can be performed, for example, by mixing the oxidized working solution with water and then separating the aqueous phase. The extracted hydrogen peroxide can then be purified, concentrated, or otherwise processed.

[0062] The removal of inactive substances from the working solution in the working solution regeneration process is carried out through a distillation process, which includes:

[0063] i) A first distillation process (also sometimes referred to as the pre-distillation process) that recovers aromatic hydrocarbons by distillation at or below atmospheric pressure; and

[0064] ii) Next, an anthraquinones and trioctyl phosphate are recovered by a second distillation process (also sometimes referred to as the post-distillation process) at a lower pressure and above 160°C.

[0065] In the first distillation step, the working solution is distilled at a pressure below atmospheric pressure to recover aromatic hydrocarbons contained in the working solution as distillate. The distillation pressure is not particularly limited as long as it allows for the recovery of aromatic hydrocarbons; for example, it can be 0.5 kPa–100 kPa, 0.8 kPa–100 kPa, 1 kPa–100 kPa, 1 kPa–50 kPa, etc. A distillation pressure that allows for the distillation of aromatic hydrocarbons but not trioctyl phosphate and anthraquinones is preferred. The distillation temperature is also not particularly limited as long as it allows for the recovery of aromatic hydrocarbons; for example, it can be 110°C–240°C, 120°C–220°C, 130°C–200°C, 140°C–190°C, 150°C–185°C, etc. A distillation temperature that allows for the distillation of aromatic hydrocarbons but not trioctyl phosphate and anthraquinones is preferred. From the viewpoint of aromatic hydrocarbon recovery rate, distillation in the first distillation step preferably continues until no more distillate is produced. The aromatic hydrocarbons distilled in the first distillation process are reused as components of the regeneration working solution.

[0066] The working solution supplied to the first distillation step is typically the working solution circulated in the hydrogen peroxide production step, containing inactive substances generated as byproducts accompanying the formation of hydrogen peroxide. This working solution can be collected at any stage of the hydrogen peroxide production step, but from a safety perspective, it is preferable to use a working solution from the extraction step that does not contain hydrogen peroxide, or even if it does, in very small amounts (e.g., less than 0.35 g / L). Examples of inactive substances include byproducts (oxides, decomposition products, etc.) from anthraquinones or solvents (aromatic hydrocarbons and trioctyl phosphate). Examples of anthraquinone byproducts include tetrahydroanthraquinone epoxides, tetrahydroxyanthraquinones, hydroxyanthraquinones, anthrone monomers, anthraquinone solvent adducts, anthraquinone polymers, etc. Examples of solvent byproducts include carboxylic acids, polyols, phenols, etc.

[0067] In the second distillation step, the residue obtained in the first distillation step is distilled at a lower pressure and above 160°C than in the first distillation step, recovering anthraquinones and trioctyl phosphate as distillates. This removes byproducts (high-boiling components) with boiling points higher than anthraquinones and trioctyl phosphate. The distillation pressure is not particularly limited, as long as it allows for the recovery of anthraquinones and trioctyl phosphate; for example, it can be 0.001 kPa to 1 kPa, 0.002 kPa to 0.5 kPa, 0.005 kPa to 0.2 kPa, 0.008 kPa to 0.1 kPa, 0.1 kPa to 0.3 kPa, etc. A distillation pressure that distills anthraquinones and trioctyl phosphate but minimizes the distillation of byproducts is preferred. The distillation temperature can be any temperature that allows for the recovery of anthraquinones and trioctyl phosphate, and there are no particular limitations. For example, it can be 160℃~300℃, 165℃~280℃, 170℃~270℃, 175℃~260℃, 220℃~260℃, etc. In some methods, the upper limit of the distillation temperature in the second distillation step can be lower than 200℃. Therefore, the distillation temperature range for the second distillation step in this method can be, for example, 160℃~199℃, 160℃~198℃, 160℃~197℃, 160℃~196℃, 160℃~195℃, 160℃~194℃, 160℃~193℃, 160℃~192℃, 160℃~191℃, 160℃~190℃, 160℃~189℃, 160℃~188℃, 160℃~187℃, 160℃~186℃, 160℃~185℃, 160℃~184℃, 160℃~183℃, 160℃~182℃, 160℃~181℃, 160℃~180℃, etc. A preferred distillation temperature is one that distills anthraquinones and trioctyl phosphate, but with minimal byproduct distillation.

[0068] From the perspective of anthraquinone recovery, the distillation in the second distillation step is preferably continued until no more distillate is produced. Furthermore, the average residence time in the second distillation step is not particularly limited; for example, it can be more than one hour. "Residence time" refers to the time from the start to the end of the distillation process, and "average residence time" refers to the simple arithmetic average of the residence times when the same distillation step is performed two or more times. The average residence time in the second distillation step can be, for example, in the range of 1 to 10 hours, or 6 to 10 hours, etc. By making the average residence time more than one hour, the following advantages are achieved: the recovery rate of anthraquinones is increased, and the conversion of byproducts from anthraquinones into anthraquinones capable of generating hydrogen peroxide occurs, increasing the amount of anthraquinones capable of generating hydrogen peroxide. For example, tetrahydroanthraquinone epoxides, as a byproduct, can be converted into tetrahydroanthraquinones capable of generating hydrogen peroxide.

[0069] Anthraquinones and trioctyl phosphate distilled in the second distillation process are reused as components of the regeneration working solution.

[0070] The apparatus used in the distillation process is not particularly limited as long as it can perform distillation at the specified temperature and pressure. Examples include batch distillation apparatus, continuous distillation apparatus, and thin-film distillation apparatus. From a cost perspective, distillation apparatus that can be used in both the first and second distillation processes is preferred.

[0071] In one embodiment, the hydrogen peroxide production method of the present invention further includes a step of separating anthraquinones and trioctyl phosphate from the distillate of the second distillation step described above. The separation of anthraquinones and trioctyl phosphate can be performed by recrystallizing the anthraquinones. Recrystallization of the anthraquinones can be performed by heating and dissolving the anthraquinones in a recrystallization solvent followed by cooling. After recrystallization, the recrystallized anthraquinones can be recovered and reused. The trioctyl phosphate separated from the anthraquinones can be separated from the recrystallization solvent by distillation or the like and reused. As a recrystallization solvent, a solvent with a large difference between the solubility of anthraquinones during heating and cooling is preferred. Non-limiting examples of recrystallization solvents include alcohol solvents (e.g., lower alcohols such as methanol, ethanol, propanol, isopropanol, butanol, tert-butanol, 2-ethylhexanol, etc.), non-polar solvents (aromatic hydrocarbons, etc.) used as components of the working solution, or polar solvents (TOP, diisobutylmethanol, tetrabutylurea, methylcyclohexyl acetate, etc.). The recrystallization solvent can consist of a single solvent or a mixture of multiple solvents. The amount of recrystallization solvent relative to the working solution is preferably an amount that allows for good recrystallization of anthraquinones; for example, it can be 1–20 times, 2–15 times, 3–10 times, or 4–8 times the volume of solvent per unit weight of the working solution (e.g., g / mL). By including a step that separates the anthraquinones from trioctyl phosphate, the anthraquinones can be recovered in a form with higher purity. Therefore, the concentration of byproducts contained in the regenerated working solution can be further reduced.

[0072] The preparation of the crude regeneration working solution in the working solution regeneration process can be carried out by mixing the aromatic hydrocarbons recovered in the first distillation process with the anthraquinones and trioctyl phosphate recovered in the second distillation process. In a process that includes separating the anthraquinones and trioctyl phosphate from the distillate of the second distillation process, the preparation of the crude regeneration working solution can be carried out by mixing the aromatic hydrocarbons recovered in the first distillation process with the anthraquinones and trioctyl phosphate recovered separately after the second distillation process. In this specification, crude regeneration working solution refers to the regeneration working solution containing the aromatic hydrocarbons, trioctyl phosphate, and anthraquinones recovered in the distillation process before alkaline washing.

[0073] When the solvent composition ratio in the working solution changes, the density, viscosity, and distribution coefficient of the working solution also change. When these parameters change, the operating conditions and equipment of each process also need to be modified, which is not preferable from the viewpoint of stable hydrogen peroxide production. Therefore, the solvent composition ratio of the regenerated working solution is preferably adjusted to a value close to that of the working solution in the circulating process. For example, the solvent composition ratio (%) of the regenerated working solution is preferably adjusted to within ±20 percentage points, preferably within ±10 percentage points, and more preferably within ±5 percentage points relative to the working solution in the circulating process (but the total adjusted solvent composition ratio does not exceed 100%). That is, the solvent of the working solution is composed of aromatic hydrocarbons and trioctyl phosphate. When the solvent composition ratio (volume ratio) of aromatic hydrocarbons:trioctyl phosphate in the recycling process is 70%:30%, it is desirable to adjust the solvent composition ratio of the regenerated working solution to 90%:10% to 50%:50%, preferably 80%:20% to 60%:40%, and more preferably 75%:25% to 65%:35%.

[0074] In practical equipment, the concentration of anthraquinones in the working solution of the circulating process decreases over the years, and operation is carried out while appropriately replenishing new anthraquinones. To prevent a decrease in the concentration of anthraquinones in the circulating process, it is preferable to prepare the solution in a manner where the concentration of anthraquinones in the regenerated working solution is the same as that in the circulating process, or higher than the concentration of anthraquinones in the circulating process but lower than the saturation concentration of anthraquinones. For example, in a working solution containing aromatic hydrocarbons, trioctyl phosphate, ethyl anthraquinone, and ethyl tetrahydroanthraquinone, it is preferable to prepare the solution in a manner where the total concentration of ethyl anthraquinone and ethyl tetrahydroanthraquinone in the regenerated working solution is 0.1–1.4 mol / L, more preferably 0.3–1.2 mol / L, and even more preferably 0.5–1.0 mol / L.

[0075] In preparing the crude regeneration working solution, in addition to the components recovered during the distillation process, one or more aromatic hydrocarbons, trioctyl phosphate, and anthraquinones from other supply sources may be mixed in. In certain embodiments, the aromatic hydrocarbons, trioctyl phosphate, and / or anthraquinones from other supply sources include commercially available or newly synthesized substances.

[0076] In the preparation process of the regenerated working solution for recycling, the crude regenerated working solution obtained in the working solution regeneration process is subjected to alkali washing to prepare the regenerated working solution for recycling. The regenerated working solution for recycling refers to the alkali-washed regenerated working solution that is particularly suitable for use in a recycling process.

[0077] Alkaline cleaning can be performed by cleaning the crude regeneration working solution with an alkaline aqueous solution. The alkali contained in the alkaline aqueous solution is preferably an alkaline metal. The alkaline metal used in the cleaning can be an alkali metal from Group IA of the periodic table, preferably lithium, sodium, or potassium. The reagents containing these metals are not particularly limited, and examples include lithium hydroxide, sodium hydroxide, sodium carbonate, sodium bicarbonate, sodium borate, sodium pyrophosphate, sodium metaborate, sodium nitrite, sodium perborate, sodium hydrogen phosphate, sodium silicate, sodium disilicate, sodium trisilicate, sodium stannate, sodium sulfide, sodium thiosulfate, sodium tungstate, potassium hydroxide, potassium borohydride, potassium carbonate, potassium cyanide, potassium nitrite, potassium phenolate, potassium hydrogen phosphate, potassium pyrophosphate, potassium stannate, etc. The components contained in the alkaline aqueous solution are preferably lithium hydroxide, sodium hydroxide, sodium carbonate, sodium bicarbonate, and potassium hydroxide; more preferably sodium hydroxide, sodium carbonate, sodium bicarbonate, and potassium hydroxide; and particularly preferably sodium hydroxide, sodium carbonate, and sodium bicarbonate. The pH of the alkaline aqueous solution containing alkali metal is preferably 8 or higher, more preferably 10 or higher, and particularly preferably 12 or higher.

[0078] Contact between the crude regeneration working solution and the alkaline aqueous solution can be achieved, for example, by contacting the solution with an alkaline aqueous solution in a volume of 0.2 times or more than 1 volume of the crude regeneration working solution. Preferably, the crude regeneration working solution is contacted with an alkaline aqueous solution in a volume of 0.3 times or more. Commonly known mixing methods can be used as the contact method. Examples include stirring, vibration, bubbling using inert gases, co-current contact, and counter-current contact, but these are not limited to any of these methods; any method that can effectively contact the crude regeneration working solution with the alkaline aqueous solution is acceptable. Furthermore, there is no strict upper limit to the volume of the alkaline aqueous solution being contacted; it can be appropriately selected based on the apparatus and operating conditions.

[0079] The contact time between the crude regeneration working solution and the alkaline aqueous solution is, for example, 1 minute or more, more preferably 3 minutes or more, and particularly preferably 5 minutes or more, and can be appropriately selected according to the apparatus and operating conditions. The contact temperature between the crude regeneration working solution and the alkaline aqueous solution is, for example, in the range of 0°C to 70°C, preferably in the range of 10°C to 60°C, and particularly preferably in the range of 20°C to 50°C. The pressure during the contact treatment between the crude regeneration working solution and the alkaline aqueous solution is not particularly limited, and it is generally suitable to maintain it at atmospheric pressure. After the contact is completed, the alkaline aqueous solution is separated from the crude regeneration working solution and discharged. Alkaline washing can be performed more than once, for example, once, twice, or three times or more.

[0080] Alkaline washing of the regeneration working solution improves its hydrogenation activity compared to washing with water alone. Furthermore, alkaline washing effectively removes acidic impurities from the crude regeneration working solution.

[0081] In one embodiment, during the preparation of the regenerated working solution for recycling, the water content of the crude regenerated working solution is adjusted to 20% to 160% of its saturated water content. During the hydrogenation step in the hydrogen peroxide production process, the water content of the working solution is preferably about 50% to about 95% of its saturated concentration at the hydrogenation temperature. The crude regenerated working solution prepared from the distillate recovered in the distillation process has a low water content, tending to result in a slow hydrogenation reaction rate. Therefore, it is preferable that the water content of the recycled regenerated working solution in the return recycling process is higher than that of the crude regenerated working solution. By washing the crude regenerated working solution with an alkaline aqueous solution, the water content of the regenerated working solution can be increased to near its saturated water content. When alkaline washing fails to achieve the desired water content range, the water content can be adjusted through dehydration treatment, water replenishment, or washing with water.

[0082] In the preparation process of the regeneration working solution for recycling, in addition to alkaline cleaning, water can also be used for cleaning. The water used for cleaning is preferably distilled water, ion-exchange water, or water purified by reverse osmosis, and water purified by methods other than those mentioned above is also preferred. Pure water is particularly preferred as the water used for cleaning. Cleaning with water can be performed in the same way as alkaline cleaning, except that water is used as the cleaning medium. Therefore, the volume of water relative to the crude regeneration working solution, the contact method with the crude regeneration working solution, the contact time, the contact temperature, and the contact pressure are the same as those described for alkaline cleaning. Cleaning with water can be performed before, after, or both of the alkaline cleaning process. Cleaning with water can be performed more than once, for example, once, twice, or three times or more.

[0083] In the process of preparing the regenerated working solution for circulation, in addition to alkaline washing, treatment can be performed using a regenerating catalyst derived from anthraquinone byproducts. This treatment using the regenerating catalyst can be carried out by passing the regenerated working solution before or after alkaline washing into a fixed bed or fluidized bed containing the regenerating catalyst. Since single-pass circulation is insufficient, circulation is preferred. Activated alumina or silica alumina is preferred as the regenerating catalyst, with activated alumina being more preferred. The surface area and particle size of the regenerating catalyst can be appropriately selected based on the reaction conditions and apparatus, without particular limitations. The reaction temperature is preferably in the range of 0°C to 200°C, more preferably 50°C to 150°C. Furthermore, due to the accumulation of hydroquinones during the reaction, the regeneration reaction is partially delayed; therefore, it is preferable to contact the hydroquinones with oxygen or air during circulation to oxidize them. This process can also be carried out while gradually removing the hydrogen peroxide generated at this time.

[0084] In one embodiment, the hydrogen peroxide manufacturing method of the present invention includes a step of returning the aforementioned recycled regenerated working solution to the hydrogen peroxide manufacturing process. The recycled regenerated working solution may be returned to any one or more of the hydrogenation, oxidation, and extraction steps included in the hydrogen peroxide manufacturing process. Here, returning to a certain step means returning to any stage from the end of a step preceding that step to the end of that step. For example, returning the recycled regenerated working solution to the hydrogenation step means returning the recycled regenerated working solution to any stage from the end of the extraction step to the end of the hydrogenation step (e.g., the outlet of the extraction unit or the inlet of the hydrogenation unit). In a particular embodiment, the recycled regenerated working solution is returned to the hydrogenation step. This embodiment is advantageous because it effectively utilizes the high hydrogenation activity of the recycled regenerated working solution. As a specific example of this embodiment, it can be illustrated by mixing the recycled regenerated working solution with the circulating working solution near the hydrogenation unit (hydrogenation tower) and introducing the resulting mixture into the hydrogenation unit. In another specific manner, the recycled regenerated working solution is returned to the oxidation and / or extraction processes. This method is advantageous when the water content of the recycled regenerated working solution is low.

[0085] Another aspect of the present invention relates to a method for manufacturing a regenerating working solution for recycling (hereinafter sometimes referred to as "the method for manufacturing a regenerating working solution for recycling of the present invention"), characterized in that it comprises:

[0086] The working solution regeneration process removes the aforementioned inactive substances from a working solution used for hydrogen peroxide production, which contains aromatic hydrocarbons, trioctyl phosphate, anthraquinones, and inactive substances generated as byproducts accompanying hydrogen peroxide production, to prepare a crude regenerated working solution after the removal of these inactive substances; and

[0087] The process for preparing the regenerated working solution for recycling involves alkali washing of the crude regenerated working solution to prepare the regenerated working solution for recycling.

[0088] The above-mentioned working solution regeneration process includes:

[0089] i) A first distillation process that recovers aromatic hydrocarbons by distillation at or below atmospheric pressure; and

[0090] ii) Next, a second distillation process is used to recover anthraquinones and trioctyl phosphate by distillation at a lower pressure and above 160°C.

[0091] The characteristics of each step in the method for manufacturing a regenerated working solution for recycling of the present invention are the same as the corresponding steps in the method for manufacturing hydrogen peroxide of the present invention.

[0092] Another aspect of the present invention relates to a method for producing hydrogen peroxide (hereinafter sometimes referred to as "hydrogen peroxide production method A of the present invention"), characterized in that it comprises:

[0093] In the hydrogen peroxide manufacturing process, a working solution containing aromatic hydrocarbons, trioctyl phosphate, and anthraquinones is hydrogenated and then oxidized to generate hydrogen peroxide. The hydrogen peroxide is then extracted from the working solution and returned to the hydrogenation process for recycling.

[0094] In the working solution regeneration process, inactive substances generated as byproducts accompanying the formation of hydrogen peroxide are removed from the working solution to prepare a regenerated working solution; and

[0095] The process for preparing the regenerated working solution for recycling involves washing the crude regenerated working solution with water or alkali to prepare the regenerated working solution for recycling.

[0096] The above-mentioned working solution regeneration process includes:

[0097] i) A first distillation process that recovers aromatic hydrocarbons by distillation at or below atmospheric pressure; and

[0098] ii) Next, a second distillation process is used to recover anthraquinones and trioctyl phosphate by distillation at a lower pressure and above 160°C.

[0099] This method is identical to the hydrogen peroxide manufacturing method of the present invention in that it does not require alkaline washing of the crude regeneration working solution, but can be replaced by water washing. As shown in Example 4, even when the crude regeneration working solution is washed only with water, the hydrogenation activity of the regeneration working solution containing trioctyl phosphate can be improved compared with the working solution in the circulation. The above description relating to the hydrogen peroxide manufacturing method of the present invention also applies to the hydrogen peroxide manufacturing method A of the present invention, provided that alkaline washing is not necessary.

[0100] Another aspect of the present invention relates to a method for manufacturing a regenerating working solution for recycling (hereinafter sometimes referred to as "method A for manufacturing a regenerating working solution for recycling of the present invention"), characterized in that it comprises:

[0101] The working solution regeneration process removes the aforementioned inactive substances from a working solution used for hydrogen peroxide production, which contains aromatic hydrocarbons, trioctyl phosphate, anthraquinones, and inactive substances generated as byproducts accompanying hydrogen peroxide production, to prepare a crude regenerated working solution after the removal of these inactive substances; and

[0102] The process for preparing the regenerated working solution for recycling involves washing the crude regenerated working solution with water or alkali to prepare the regenerated working solution for recycling.

[0103] The above-mentioned working solution regeneration process includes:

[0104] i) A first distillation process that recovers aromatic hydrocarbons by distillation at or below atmospheric pressure; and

[0105] ii) Next, a second distillation process is used to recover anthraquinones and trioctyl phosphate by distillation at a lower pressure and above 160°C.

[0106] The characteristics of each step in the method A for manufacturing a regenerated working solution for recycling of the present invention are the same as the characteristics of the corresponding steps in the method A for manufacturing hydrogen peroxide of the present invention.

[0107] Other aspects of the present invention relate to a method for producing hydrogen peroxide (hereinafter sometimes referred to as "hydrogen peroxide production method B of the present invention"), characterized by comprising:

[0108] The hydrogen peroxide manufacturing process involves hydrogenating a working solution containing aromatic hydrocarbons, polar solvents, and anthraquinones, followed by oxidation to generate hydrogen peroxide. The hydrogen peroxide is then extracted from the working solution and returned to the hydrogenation process for recycling.

[0109] In the working solution regeneration process, inactive substances generated as byproducts accompanying the formation of hydrogen peroxide are removed from the working solution to prepare a regenerated working solution; and

[0110] The process for preparing the regenerated working solution for recycling involves alkali washing of the crude regenerated working solution to prepare the regenerated working solution for recycling.

[0111] The above-mentioned working solution regeneration process includes:

[0112] i) A first distillation process that recovers aromatic hydrocarbons by distillation at or below atmospheric pressure; and

[0113] ii) Next, a second distillation process is used to recover anthraquinones by distillation at a lower pressure and above 160°C.

[0114] The polar solvent is recovered in the first or second distillation process.

[0115] This method is the same as the hydrogen peroxide manufacturing method of the present invention, except that the polar solvent contained in the working solution is not specifically trioctyl phosphate, and the polar solvent is recovered in either the first or second distillation step. As shown in Example 4, by alkali washing the crude regenerated working solution, the hydrogenation activity of the resulting regenerated working solution can be improved compared to washing with water. This can be considered to also apply to working solutions containing polar solvents other than trioctyl phosphate. The above description relating to the hydrogen peroxide manufacturing method of the present invention also applies to the hydrogen peroxide manufacturing method B of the present invention, provided that the polar solvent is not specifically trioctyl phosphate and the polar solvent is recovered in either the first or second distillation step.

[0116] In the hydrogen peroxide production method B of the present invention, the polar solvent is not particularly limited as long as it can dissolve anthraquinones, and includes, for example, alcohols (e.g., diisobutylmethanol (DIBC), 2-octanol), tetrasubstituted ureas (e.g., tetrabutylurea (TBU)), phosphate esters (e.g., trioctyl phosphate), 2-pyrrolidone, or alkylcyclohexyl acetate (e.g., methylcyclohexyl acetate (MCHA)). The distillation step for recovering the polar solvent can be appropriately determined according to the type of polar solvent. For example, DIBC or 2-octanol can be recovered in the first distillation step, and TOP or TBU can be recovered in the second distillation step.

[0117] Another aspect of the present invention relates to a method for manufacturing a regenerating working solution for recycling (hereinafter sometimes referred to as "method B for manufacturing a regenerating working solution for recycling of the present invention"), characterized in that it comprises:

[0118] The working solution regeneration process removes the aforementioned inactive substances from a working solution used for hydrogen peroxide production, which contains aromatic hydrocarbons, polar solvents, anthraquinones, and inactive substances generated as byproducts accompanying hydrogen peroxide production, to prepare a crude regenerated working solution after the removal of these inactive substances; and

[0119] The process for preparing the regenerated working solution for recycling involves alkali washing of the crude regenerated working solution to prepare the regenerated working solution for recycling.

[0120] The above-mentioned working solution regeneration process includes:

[0121] i) A first distillation process that recovers aromatic hydrocarbons by distillation at or below atmospheric pressure; and

[0122] ii) Next, a second distillation process is used to recover anthraquinones by distillation at a lower pressure and above 160°C.

[0123] The polar solvent is recovered in the first or second distillation process.

[0124] The characteristics of each step in the method B for manufacturing a regenerated working solution for recycling of the present invention are the same as the characteristics of the corresponding steps in the method B for manufacturing hydrogen peroxide of the present invention.

[0125] Another aspect of the present invention relates to a hydrogen peroxide manufacturing system (hereinafter sometimes referred to as "the hydrogen peroxide manufacturing system of the present invention") having a distillation column, a preparation tank, a washing tank, a hydrogenation column, an oxidation column, and an extraction column. In addition to the above, the hydrogen peroxide manufacturing system of the present invention may also have a pre-distillation distillate tank and / or a post-distillation distillate tank. One embodiment of the hydrogen peroxide manufacturing system of the present invention will now be described with reference to the accompanying drawings.

[0126] Figure 1 The present invention describes a hydrogen peroxide manufacturing system A, comprising a distillation tower 1, a preparation tank 2, a cleaning tank 3, a hydrogenation tower 4, an oxidation tower 5, an extraction tower 6, a front-end distillate tank 9, and a rear-end distillate tank 10. Distillation column 1 has an unidentified component discharge pipeline 8 and a distillate conveying pipeline 7. The distillate conveying pipeline 7 is connected to the first-stage distillate tank 9 via the first-stage distillate conveying pipeline 7a. The distillate conveying pipeline 7 is connected to the second-stage distillate tank 10 via the second-stage distillate conveying pipeline 7b. The first-stage distillate tank 9 and the preparation tank 2 are connected via the first-stage distillate supply pipeline 11. The second-stage distillate tank 10 and the preparation tank 2 are connected via the second-stage distillate supply pipeline 12. The preparation tank 2 and the washing tank 3 are connected via the coarse regeneration working solution supply pipeline 13. The washing tank 3 is connected to an alkaline solution supply pipeline 14 and a water supply pipeline 15. The washing tank 3 has a waste liquid pipeline 17. The washing tank 3 and the hydrogenation tower 4 are also connected. The hydrogenation tower 4 is connected to the regenerated working solution supply line 16. The hydrogenation tower 4 has a hydrogenating agent supply line 19 and a hydrogenating agent circulation line 18. The hydrogenation tower 4 and the oxidation tower 5 are connected through the hydrogenation working solution supply line 20. The oxidation tower 5 has an oxidant supply line 21 and an exhaust line 22. The oxidation tower 5 and the extraction tower 6 are connected through the oxidation working solution supply line 23. The extraction tower 6 has a water supply line 24 and a hydrogen peroxide delivery line 25. The distillation tower 1 and the extraction tower 6 are connected through the hydrogen peroxide extraction working solution supply line 26. The regenerated working solution supply line 16 and the hydrogen peroxide extraction working solution supply line 26 are connected through the hydrogen peroxide extraction working solution circulation line 27. In addition, the following pipelines are equipped with valves: the front-end distillate delivery line 7a, the rear-end distillate delivery line 7b, the unknown component discharge line 8, the front-end distillate supply line 11, the rear-end distillate supply line 12, the crude regeneration working solution supply line 13, the alkaline solution supply line 14, the water supply line 15, the circulating regeneration working solution supply line 16, and the waste liquid line 17. The distillation column 1 is capable of vacuum distillation (e.g., 0.1 kPa to 15 kPa) at various temperatures (e.g., 120°C to 260°C).

[0127] In hydrogenation tower 4, the working solution reacts with a hydrogen-containing hydrogenating agent 32 (e.g., a mixture of hydrogen, inert gas (nitrogen, etc.) and hydrogen from hydrogenating agent supply line 19) to generate anthraquinones from anthraquinones. Unreacted hydrogenating agent is repeatedly supplied to hydrogenation tower 4 via hydrogenating agent circulation line 18. The hydrogenated working solution enters oxidation tower 5 through hydrogenated working solution supply line 20, where anthraquinones are oxidized by an oxygen-containing oxidant 33 (e.g., air, oxygen, etc.) supplied from oxidant supply line 21 to generate anthraquinones and hydrogen peroxide. Unreacted oxidant 34 is discharged from exhaust line 22. The oxidized working solution containing hydrogen peroxide enters extraction tower 6 through oxidation working solution supply line 23, where the generated hydrogen peroxide is converted into hydrogen peroxide water 36 by water 35 supplied from water supply line 24, and is recovered from hydrogen peroxide delivery line 25. A portion of the working solution after hydrogen peroxide extraction enters the distillation column 1 through the hydrogen peroxide extraction working solution supply line 26, while the remainder is merged with the circulating working solution supply line 16 through the hydrogen peroxide extraction working solution circulation line 27 and returned to the hydrogenation column 4.

[0128] The working solution after hydrogen peroxide extraction entering distillation column 1 is supplied for pre-distillation at atmospheric pressure or below. The pre-distillate containing aromatic hydrocarbons, obtained through pre-distillation, is collected in pre-distillate tank 9 via distillate delivery lines 7 and 7a. The residue remaining in distillation column 1 is supplied for post-distillation at a lower pressure than pre-distillation and above 160°C. The post-distillate containing anthraquinones and trioctyl phosphate, obtained through post-distillation, is collected in post-distillate tank 10 via distillate delivery lines 7 and 7b. An unidentified component 28, as a residue after post-distillation, is discharged from unidentified component discharge line 8. The distillate from the first stage of distillation, collected in the first stage distillate tank 9, and the distillate from the second stage distillate tank 10, collected in the second stage distillate tank 10, enter the preparation tank 2 through the first stage distillate supply line 11 and the second stage distillate supply line 12, respectively, for mixing to prepare a crude regeneration working solution. The obtained crude regeneration working solution enters the cleaning tank 3 through the crude regeneration working solution supply line 13. The crude regeneration working solution is cleaned with alkaline solution 29 supplied from the alkaline solution supply line 14, and then, as needed, with water 30 supplied from the water supply line 15, to obtain a regenerated working solution for recycling. The alkaline solution or water used for cleaning is discharged as waste liquid 31 from the waste liquid line 17. The regenerated working solution for recycling enters the hydrogenation tower 4 through the regenerated working solution for recycling line 16, where it merges with the working solution from the recycling line 27 of the working solution after hydrogen peroxide extraction.

[0129] The hydrogen peroxide manufacturing system of the present invention may further include a recrystallization tank. A summary of the hydrogen peroxide manufacturing system B of the present invention, including a recrystallization tank, is provided below. Figure 2 This will be explained. Specifically, in hydrogen peroxide production system B, regarding... Figure 1 The components of the hydrogen peroxide manufacturing system A shown are marked with the same symbols, and their descriptions are omitted.

[0130] In this configuration, the downstream distillate supply line 12, connected to the downstream distillate tank 10, is connected to the recrystallization tank 37. The anthraquinone supply line 40, connected to the recrystallization tank 37, is connected to the preparation tank 2. The recrystallization tank 37 is further connected to a recrystallization solvent supply line 39, a waste liquid line 41, and a filtrate delivery line 42. The recrystallization solvent supply line 39 connects the recrystallization solvent tank 38 to the recrystallization tank 37, and the filtrate delivery line 42 connects the recrystallization tank 37 to the distillation column 1. The recrystallization solvent tank 38 is connected to the distillate delivery line 7 via the distillate recrystallization solvent delivery line 7d, and the preparation tank 2 is connected to the distillate delivery line 7 via the distillate top delivery line 7c. The recrystallization tank 37 has a temperature control device, enabling the heating and dissolution of anthraquinones in the recrystallization solvent, and subsequent recrystallization of anthraquinones using cooling. The recrystallization tank 37 also has a filter, capable of filtering and separating the recrystallized anthraquinones.

[0131] In this method, the downstream distillate stored in the downstream distillate tank 10 enters the recrystallization tank 37 via the downstream distillate supply line 12. Recrystallization solvent is supplied to the recrystallization tank 37 from the recrystallization solvent supply line 39. The anthraquinones contained in the downstream distillate recrystallize by heating and dissolving them, followed by cooling. The recrystallized anthraquinones are recovered by a filter in the recrystallization tank 37 and sent to the preparation tank 2 via the anthraquinone supply line 40. The filtrate containing trioctyl phosphate and the recrystallization solvent, having passed through the filter, is sent to the distillation column 1 via the filtrate delivery line 42, or is discarded via the waste liquid line 41. By distillation, recrystallization solvent and trioctyl phosphate are distilled off from the filtrate fed into distillation column 1. The distilled recrystallization solvent is collected in recrystallization solvent tank 38 through distillate conveying line 7 and distillate recrystallization solvent conveying line 7d. The distilled trioctyl phosphate is sent to preparation tank 2 through distillate conveying line 7 and distillate TOP conveying line 7c.

[0132] The hydrogen peroxide production system of the present invention is not particularly limited to the manner described above, and various modifications can be made within the scope of the key points of the invention. For example, in Figure 1In the hydrogen peroxide manufacturing system A shown, it can be implemented in the following ways: (A1) without the front-end distillate tank 9 and the front-end distillate delivery pipeline 7a connected to it, the distillate delivery pipeline 7 and the preparation tank 2 are connected by the front-end distillate supply pipeline 11; (A2) without the rear-end distillate tank 10 and the rear-end distillate delivery pipeline 7b connected to it, the distillate delivery pipeline 7 and the preparation tank 2 are connected by the rear-end distillate supply pipeline 12; (A3) without the front-end distillate tank 9 and the front-end distillate delivery pipeline 7a connected to it, (A4) The distillation column 1 and the preparation tank 2 are connected by the following: the distillation column 7 and the preparation tank 2 are connected by the following: the distillation column 7, the distillation column 9 and the distillation column 7a connected to it, the distillation column 1 and the preparation tank 2 are not provided; the distillation column 1 and the preparation tank 2 are connected by the following: the distillation column 1 is connected by the following: the distillation column 7, the distillation column 9 and the distillation column 7a connected to it, the distillation column 10 and the distillation column 7b connected to it, the distillation column 1 and the preparation tank 2 are not provided by the following: the distillation column 1 and the preparation tank 2 are connected ... not provided by the following: the distillation column 9 and the distillation column 7a connected to it, the distillation column 10 and the distillation column 7b connected to it, the distillation column 11 and the distillation column 12 are connected to it.

[0133] In addition, Figure 2 In the hydrogen peroxide manufacturing system B shown, in addition to the above-mentioned modifications (A1) to (A4) of the hydrogen peroxide manufacturing system A, it can also be implemented in the following ways: (B1) without the filtrate delivery line 42 and the distillate recrystallization solvent delivery line 7d; (B2) with a distillate TOP tank, the distillate delivery line 7 and the distillate TOP tank are connected by the distillate TOP delivery line 7c, and the distillate TOP tank and the preparation tank 2 are connected by the distillate TOP supply line; (B3) without a filter in the recrystallization tank 37, but instead placing it in the middle of the anthraquinone supply line 40.

[0134] Furthermore, in either of the hydrogen peroxide production systems A and B, a pump or additional valve, a branch line, or a valve can be removed from a line with a valve, as needed, in at least one pipeline.

[0135] The present invention will be described in more detail below with reference to embodiments, but the present invention is not limited to these embodiments.

[0136]

Example

[0137] <Analytical Methods>

[0138] Aromatic hydrocarbons, trioctyl phosphate, 2-ethylanthraquinone, and 2-ethyltetrahydroanthraquinone were quantified in the working solution and samples obtained during each operation using a gas chromatography system. The gas chromatography system used was a Shimadzu GC-2014 gas chromatograph. The column used was an Agilent DB-5MS capillary column. All substances other than those listed above were designated as "unknown components." It is presumed that most of the "unknown components" are inactive substances.

[0139] The densities of the initial working solution and the regenerated working solution for circulation were measured using a DA-640 hydrometer manufactured by Kyoto Electronics Co., Ltd., and the viscosities were measured using a Type B viscometer manufactured by Tokyo Keiki Co., Ltd.

[0140] The hydrogenation activity of the initial working solution and the recycled working solution was evaluated as follows: The hydrogenation catalyst and working solution were added to a 100 mL two-necked flask. A stirrer was connected to one neck of the flask, and the other neck was connected to the hydrogen supply unit. The flask was then sealed. The hydrogen supply unit included a hydrogen metering tube, a U-tube manometer, and a water reservoir. During the hydrogenation reaction, the height of the water reservoir was adjusted according to the change in the liquid level in the U-tube manometer, thereby maintaining the internal pressure of the flask equal to atmospheric pressure. The hydrogen absorption was measured by the difference in liquid level in the hydrogen metering tube. The flask was immersed in a 30°C water bath and allowed to stand for 10 minutes. After repeating the purging and hydrogen introduction of the flask three times, the stirrer was activated. The hydrogen absorption was measured from the start of hydrogen absorption to 30 minutes later. The hydrogen absorption was converted to a value at 0°C and 1 atm. The activity value of the hydrogenation catalyst was expressed as the standard state hydrogen absorption rate per unit weight of hydrogenation catalyst [NmL / (min×g)]. The hydrogenation catalyst used was 0.05 g of 2% Pd / silica dried at 120 °C or 0.1 g of 1% Pd / silica alumina dried at 120 °C.

[0141] Example 1

[0142] The first and second distillation processes of the present invention are implemented on a small scale, and the initial working solution and the recycled regenerated working solution are compared.

[0143] <First Distillation Process>

[0144] Add 400g of the working solution to a 500mL flask in the distillation apparatus. Distill under reduced pressure, maintaining a vacuum of 1.3kPa throughout. Raise the temperature inside the flask from room temperature to 182℃. Continue distillation until no further distillate is produced at 182℃ and 1.3kPa.

[0145] <Second Distillation Process>

[0146] The residue obtained in the first distillation step was distilled at a lower pressure than that of the first distillation step. The vacuum level fluctuated between 0.03 kPa and 0.15 kPa for a period of time after the start of distillation, eventually stabilizing at 0.08 kPa. The temperature inside the flask was raised from room temperature to 202 °C. Distillation was continued until no further distillate was obtained at 0.08 kPa and 202 °C.

[0147] <Distillation Results>

[0148] The composition of the initial working solution and the distillates and residues recovered through each distillation process is shown in Table 1. High-boiling aromatic naphtha (Swasol 1500, produced by Maruzen Petrochemical Co., Ltd., CAS No. 64742-94-5) was used as the aromatic hydrocarbon (as in Examples 2-4). During distillation, various reactions occur, exemplified by the conversion of tetrahydroanthraquinone to anthraquinone; therefore, depending on the composition, the weight may sometimes increase compared to the initial working solution. Furthermore, "loss amount" indicates the amount lost during the experiment (the reason can be attributed to losses in the cold trap or pump, etc.).

[0149] Table 1

[0150] Table 1. Composition of initial working solution, distillate, and residue (material balance)

[0151]

[0152] Evaluation of Regenerated Working Solution for Recycling

[0153] A regeneration working solution is prepared from the distillates recovered in each distillation step. A fraction from the first distillation step is added to the fraction from the second distillation step to achieve a solvent composition ratio close to that of the initial working solution, thus preparing a crude regeneration working solution. The compositions of the initial working solution and the crude regeneration working solution are shown below.

[0154] Table 2

[0155] Table 2. Composition of initial working solution and crude regeneration working solution

[0156]

[0157] The crude regeneration working solution was sequentially washed with two volumes of 30wt% sodium hydroxide aqueous solution and two volumes of pure water to obtain a regenerated working solution for recycling. The following shows the results comparing the density, viscosity, and hydrogenation activity of the initial working solution and the regenerated working solution for recycling. Specifically, when evaluating the hydrogenation activity, 0.05 g of 2 wt% Pd / silica dried at 120 °C was used as the hydrogenation catalyst.

[0158] Table 3

[0159] Table 3. Comparison of initial working solution and regenerated working solution for circulation

[0160]

[0161] <Isolation of Anthraquinones>

[0162] Approximately 200 mL of ethanol was added to 32 g of the distillate from the second distillation step, and the mixture was heated to dissolve it, then cooled to room temperature (recrystallization). The crystals were filtered and dried. The following shows the composition of the distillate from the second distillation step and the crystals recovered by recrystallization. Anthraquinones were separated from trioctyl phosphate and unidentified components with a recovery rate of 64%. Using this method, the recovered anthraquinones can be reused as a component of the working solution.

[0163] Table 4

[0164] Table 4. Composition of distillate from the second distillation process and crystals recovered by recrystallization

[0165]

[0166] Example 2

[0167] The first and second distillation processes of the present invention were carried out under conditions different from those in Example 1, and the initial working solution and the recycled regenerated working solution were compared.

[0168] <First Distillation Process>

[0169] Add 351 g of the working solution to a 500 mL flask in the distillation apparatus. Distill under reduced pressure, maintaining a vacuum of 1.3 kPa throughout. Raise the temperature inside the flask from room temperature to 157 °C. Continue distillation until no further distillate is produced at 157 °C and 1.3 kPa.

[0170] <Second Distillation Process>

[0171] The residue obtained in the first distillation step is distilled at a lower pressure than that of the first distillation step. The vacuum level fluctuates between 10 Pa and 150 Pa for a period of time after the start of distillation, eventually stabilizing at 0.01 kPa to 0.04 kPa. The temperature inside the flask is raised from room temperature to 181 °C. Distillation continues until no further distillate is produced at 0.01 kPa and 181 °C.

[0172] <Distillation Results>

[0173] The composition of the initial working solution and the distillates and residues recovered through each distillation process is shown in Table 5.

[0174] Table 5

[0175] Table 5. Composition of initial working solution, distillate, and residue (material balance)

[0176]

[0177] The crude regeneration working solution was prepared using the same method as in Example 1. Table 6 shows the composition of the initial working solution and the crude regeneration working solution.

[0178] Table 6

[0179] Table 6. Composition of initial working solution and coarse regeneration working solution

[0180]

[0181] A regenerated working solution for recycling was prepared using the same cleaning process as in Example 1. Table 7 shows a comparison of the density, viscosity, and hydrogenation activity of the initial working solution and the regenerated working solution for recycling. In evaluating the hydrogenation activity, 0.1 g of 1 wt% Pd / silica alumina dried at 120 °C was used as the hydrogenation catalyst.

[0182] Table 7

[0183] Table 7. Comparison of initial working solution and regenerated working solution for circulation

[0184]

[0185] Example 3

[0186] The first and second distillation processes of the present invention were carried out under conditions different from those in Examples 1 and 2, and the initial working solution and the recycled working solution were compared.

[0187] <First Distillation Process>

[0188] Add 351 g of the same working solution as in Example 2 to a 500 mL flask in the distillation apparatus. Distillation is carried out under reduced pressure, with the vacuum level maintained at 1.3 kPa throughout. The temperature inside the flask is raised from room temperature to 180 °C. Distillation continues until no more distillate is produced at 1.3 kPa and 180 °C.

[0189] <Second Distillation Process>

[0190] The residue obtained in the first distillation step is distilled at a lower pressure than that of the first distillation step. The vacuum level is maintained at 0.13 kPa throughout. The temperature inside the flask is raised from room temperature to 250 °C. Distillation continues until no further distillate is produced at 0.13 kPa and 250 °C.

[0191] <Distillation Results>

[0192] The composition of the initial working solution and the distillates and residues recovered through each distillation process is shown in Table 8.

[0193] Table 8

[0194] Table 8. Composition of initial working solution, distillate, and residue (material balance)

[0195]

[0196] The crude regeneration working solution was prepared using the same method as in Example 1. Table 9 shows the composition of the initial working solution and the crude regeneration working solution.

[0197] Table 9

[0198] Table 9. Composition of initial working solution and coarse regeneration working solution

[0199]

[0200] A regenerated working solution for recycling was prepared using the same cleaning process as in Example 1. Table 10 shows a comparison of density, viscosity, and hydrogenation activity. In evaluating hydrogenation activity, 0.1 g of 1 wt% Pd / silica alumina dried at 120 °C was used as the hydrogenation catalyst.

[0201] Table 10

[0202] Table 10. Evaluation of initial working solution and regenerated working solution for circulation

[0203]

[0204] Example 4

[0205] The crude regeneration working solution obtained in Example 2 was washed twice with twice the volume of pure water to obtain a regeneration working solution for recycling (washed with pure water). Hydrogenation activity tests were performed using the same method as in Example 2. 0.1 g of 1 wt% Pd / silica alumina dried at 120 °C was used as the hydrogenation catalyst. Table 11 shows the results of the hydrogenation activity tests. The regeneration working solution for recycling, washed only with pure water, showed higher hydrogenation activity than the initial working solution, but the regeneration working solution for recycling, washed with alkali (Example 2), showed even higher hydrogenation activity.

[0206] Table 11

[0207] Table 11. Hydrogenation Activity

[0208]

Claims

1. A method for producing hydrogen peroxide, characterized in that, include: In the hydrogen peroxide manufacturing process, a working solution containing aromatic hydrocarbons, trioctyl phosphate, and anthraquinones is hydrogenated and then oxidized to generate hydrogen peroxide. The hydrogen peroxide is then extracted from the working solution and returned to the hydrogenation process for recycling. In the working solution regeneration process, inactive substances generated as byproducts accompanying the generation of hydrogen peroxide are removed from the working solution to prepare a crude regeneration working solution after the inactive substances have been removed. and The process for preparing the regenerated working solution for recycling involves alkali washing of the crude regenerated working solution to prepare the regenerated working solution for recycling. The working solution regeneration process includes: i) A first distillation process for recovering aromatic hydrocarbons by distillation at or below atmospheric pressure and at 140°C to 190°C; and ii) Next, a second distillation process is used to recover anthraquinones and trioctyl phosphate by distillation at a lower pressure and above 160°C and below 200°C.

2. The method for producing hydrogen peroxide as described in claim 1, characterized in that: The pressure in the first distillation process is in the range of 1 kPa to 100 kPa.

3. The method for producing hydrogen peroxide as described in claim 1, characterized in that: The pressure in the second distillation process is below 1 kPa.

4. The method for producing hydrogen peroxide as described in claim 1, characterized in that: The temperature in the second distillation process is in the range of 160℃ to 189℃.

5. The method for producing hydrogen peroxide as described in claim 1, characterized in that: The anthraquinones include alkyl anthraquinones and alkyl tetrahydroanthraquinones.

6. The method for producing hydrogen peroxide according to any one of claims 1 to 5, characterized in that: This includes the process of returning the recycled working solution to the hydrogen peroxide manufacturing process.

7. The method for producing hydrogen peroxide as described in claim 6, characterized in that: The solvent composition ratio of the crude regeneration working solution is within ±20 percentage points relative to the solvent composition ratio of the working solution circulated in the hydrogen peroxide manufacturing process.

8. The method for producing hydrogen peroxide as described in claim 6, characterized in that: The concentration of anthraquinones in the crude regeneration working solution is within the range of above the concentration of anthraquinones in the working solution circulated in the hydrogen peroxide manufacturing process and below the saturation concentration of anthraquinones.

9. The method for producing hydrogen peroxide as described in claim 6, characterized in that: In the process of preparing the regenerated working solution for circulation, the water content of the regenerated working solution is adjusted to 20% to 160% of the saturated water content.

10. The method for producing hydrogen peroxide as described in claim 6, characterized in that: The process for preparing the regenerated working solution for recycling also includes a process of washing the regenerated working solution with water after alkali cleaning.

11. The method for producing hydrogen peroxide according to any one of claims 1 to 5, characterized in that: It also includes a step of separating anthraquinones and trioctyl phosphate from the distillate of the second distillation step.

12. The method for producing hydrogen peroxide as described in claim 11, characterized in that: The process of separating anthraquinones and trioctyl phosphate is carried out by recrystallization.

13. A hydrogen peroxide manufacturing system comprising a distillation column, a preparation tank, a washing tank, a hydrogenation column, an oxidation column, and an extraction column, characterized in that: The distillation column has an unidentified component discharge pipeline. The distillation column and the preparation tank are connected by a front-end distillate supply pipeline and a back-end distillate supply pipeline. The preparation tank and the washing tank are connected by a coarse regeneration working solution supply pipeline. The washing tank is connected to an alkaline solution supply pipeline and a water supply pipeline. The washing tank has a waste liquid pipeline. The washing tank and the hydrogenation column are connected by a circulating regeneration working solution supply pipeline. The hydrogenation column is connected by a hydrogenating agent supply pipeline. The hydrogenation column and the oxidation column are connected by a hydrogenation working solution supply pipeline. The oxidation column is connected by an oxidizing agent supply pipeline. The oxidation column and the extraction column are connected by an oxidation working solution supply pipeline. The extraction column has a hydrogen peroxide delivery pipeline. The distillation column and the extraction column are connected by a working solution supply pipeline after hydrogen peroxide extraction. The distillation column is configured to perform a front-end distillation to recover aromatic hydrocarbons at atmospheric pressure or below and at 140°C to 190°C, and a back-end distillation to recover anthraquinones and trioctyl phosphate at a lower pressure and at a temperature above 160°C and below 200°C.

14. The system as described in claim 13, characterized in that: It also has a front-end distillate tank, the distillation column and the front-end distillate tank are connected by a front-end distillate delivery pipeline, and the front-end distillate tank and the preparation tank are connected by a front-end distillate supply pipeline.

15. The system as described in claim 13, characterized in that: It also has a downstream distillate tank, and the distillation column and the downstream distillate tank are connected by a downstream distillate delivery pipeline. The downstream distillate tank and the preparation tank are connected by a downstream distillate supply pipeline.

16. The system as described in claim 13, characterized in that: It also has a recrystallization tank, which has a filter and a waste liquid pipeline. The recrystallization tank is connected to a recrystallization solvent supply pipeline. The recrystallization tank and the distillation tower are connected through a downstream distillate supply pipeline. The recrystallization tank and the preparation tank are connected through an anthraquinone supply pipeline.

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