Novel process for the production of hydrogen peroxide

Abstract

This invention relates to a novel method for producing hydrogen peroxide via the anthraquinone process. In particular, this invention relates to a novel flow configuration for recycling and removing hydrogen peroxide from the aqueous phase in a hydrogen peroxide production process.

Description

Technical Field

[0001] This invention relates to a novel method for producing hydrogen peroxide via the anthraquinone process. In particular, this invention relates to a novel flow configuration for recycling and removing hydrogen peroxide from the aqueous phase in a hydrogen peroxide production process. Prior Technology

[0002] Hydrogen peroxide is one of the most important inorganic chemicals produced worldwide. Its industrial applications include textiles, pulp and paper bleaching, organic synthesis (propylene oxide), the manufacture of inorganic chemicals and detergents, environmental applications, and others.

[0003] Hydrogen peroxide is mainly synthesized using the large-scale Riedl-Pfleiderer process, also known as the anthraquinone (circular) process or AO (auto-oxidation) process. This method involves dissolving organic anthraquinones in a solvent and circulating this "working solution" (WS) mixture around the equipment.

[0004] The first step of the AO process involves the chemical reduction of anthraquinone derivatives present in the organic working solution using hydrogen and a catalyst. The mixture of organic solvent, hydroquinone, and quinone is then separated from the catalyst and the hydroquinone is oxidized using oxygen, air, or oxygen-enriched air, thereby regenerating one or more quinones and simultaneously forming hydrogen peroxide.

[0005] Hydrogen peroxide is then typically extracted with water in an extraction tower and recovered as a crude hydrogen peroxide aqueous solution, and the working solution is returned to the hydrogenator to complete the loop.

[0006] Therefore, the typical arrangement of a standard hydrogen peroxide plant according to prior art can be summarized as starting with a hydrogenator, followed by an oxidation reactor, and then an extraction column. Hydrogen peroxide is typically extracted from the working solution in a demineralized water stream from the extraction column. The working solution is then returned from the extraction column to the hydrogenator (see Figure 1).

[0007] Further details of the anthraquinone process for producing hydrogen peroxide are revealed in standard textbooks, such as Kirk-Othmer, Encyclopedia of Chemical Technology, August 2001, chapter "Hydrogen Peroxide"; or Ullmann's Encyclopedia of Industrial Chemistry, 5th edition, 1989, Vol. A13, pp. 449-454.

[0008] Although both reduction and oxidation reactions are highly efficient in terms of yield and selectivity, some degenerated anthraquinones may form in the working solution mixture.

[0009] The typical degraded anthraquinone material formed primarily in the oxidation reactor is 6-alkyl-1,2,3,4-tetrahydro-4a,9a-epoxy-anthraquinone-9,10-dione. It is well known in the art that the formation of the unwanted degradation product 6-alkyl-1,2,3,4-tetrahydro-4a,9a-epoxy-anthraquinone-9,10-dione in the oxidation reactor increases with the presence of hydrogen peroxide and tetrahydroanthraquinone material from the hydrogenator (see, for example, Ullmann, F., Gerhartz, W., Yamamoto, YS, Campbell, FT, Pfefferkorn, R., Rounsaville, JF, and Ullmann, F. (1985), Ullmann's encyclopedia of industrial chemistry, Weinheim, Federal Republic of Germany: VCH, and U.S. Patent Application No. 2001 / 0028873). Trace amounts of palladium or other precious metals from the hydrogenator catalyst can act as catalysts in the oxidation reactor and thus promote the formation of this undesirable byproduct.

[0010] Furthermore, epoxide formation is catalyzed in the presence of hydrogen peroxide (see, for example, US 2003 / 0109726), and therefore, in the AO process known in the prior art, it is necessary to minimize the concentration of hydrogen peroxide in the oxidation reactor in order to minimize the formation of epoxide substances such as 6-alkyl-1,2,3,4-tetrahydro-4a,9a-epoxyanthracene-9,10-dione.

[0011] Furthermore, it is known that if the concentration of hydrogen peroxide exceeds a certain level and the ratio of organic solution to hydrogen peroxide is constant, mixing the organic solution with hydrogen peroxide may result in the formation of a mixture capable of propagating detonation. This poses a particular risk for the prior art AO process, as small pockets of high-concentration hydrogen peroxide can easily form in the oxidation reactor. These pockets contain approximately 60 wt.% or higher of hydrogen peroxide, far exceeding operational safety limits. The appearance of these high-concentration aqueous hydrogen peroxide pockets is due to the organic working solution becoming "wet" from prior contact with the aqueous phase (also known as residual water droplets) in the extraction column within the working solution loop.

[0012] Another problem with the AO process known in the art is that, due to the oxidation of hydroquinone back to quinone, the polarity of the working solution decreases slightly in the oxidation reactor, leading to supersaturation of the working solution relative to the aqueous phase. Consequently, a small amount of aqueous phase exits from the organic solution.

[0013] The present invention aims to overcome one or more difficulties or disadvantages identified in prior art documents.

[0014] Specifically, the purpose of this invention is... • Control the concentration of hydrogen peroxide in the oxidation reactor; • Avoid forming hydrogen peroxide concentrations exceeding safety limits; • Improve extraction efficiency and thus increase hydrogen peroxide production; and • Reduce the formation of unwanted degradative anthraquinone substances. Summary of the Invention

[0015] This invention relates to a method for producing hydrogen peroxide via the anthraquinone process, wherein the method comprises the following steps: (1) Hydrogenating an organic working solution containing one or more anthraquinone derivatives in a hydrogenation reactor in the presence of a heterogeneous catalyst to obtain a hydrogenated organic working solution containing one or more hydrogenated anthraquinone derivatives; (2) The hydrogenated organic working solution obtained in step (1) is oxidized in an oxidation reactor, which is divided into an upper region, a middle region and a lower region. The hydrogenated organic working solution obtained in step (1) is introduced into the upper region of the oxidation reactor and oxygen-containing gas is introduced into the lower region of the oxidation reactor to form hydrogen peroxide in a countercurrent process and obtain an oxidized organic working solution containing hydrogen peroxide. (3) The oxidized organic working solution containing hydrogen peroxide obtained in step (2) is sent to a combined degasser / decanter device, or the oxidized organic working solution containing hydrogen peroxide obtained in step (2) is directly decanted in the lower region of the oxidation reactor, and then the oxidized organic working solution containing dissolved hydrogen peroxide is sent to the degasser to expand the entrained gas and degas the oxidized organic working solution containing hydrogen peroxide; (4) The degassed and oxidized organic working solution obtained in step (3) is introduced into the lower part of the extraction tower and combined with the aqueous solution to form an aqueous phase and an organic phase containing hydrogen peroxide; (5) Remove the aqueous phase obtained in step (4) from the lower part of the extraction tower and remove the organic phase from the upper part of the extraction tower and return the organic phase to the hydrogenation reactor; (6) At least a portion of the aqueous phase removed from the extraction tower in step (5) is returned to the central region of the oxidation reactor; and (7) Recover hydrogen peroxide aqueous solution.

[0016] According to the present invention, hydrogen peroxide aqueous solution is preferably recovered in the following two ways: (a) The aqueous hydrogen peroxide solution can be removed directly from the lower region of the oxidation reactor (preferably by decantation, since the aqueous phase forms a denser separated phase at the bottom of the oxidation reactor) or (b) The oxidized working solution containing the aqueous phase returned to the central region of the oxidation reactor in step (6) is sent to a combined degasser / decanter unit, wherein the oxidized organic working solution is decanted to obtain an aqueous phase and an organic phase containing hydrogen peroxide, and then the aqueous phase containing hydrogen peroxide is removed from the unit.

[0017] In addition, according to the present invention, the portion of the aqueous phase obtained in step (5) that is not returned to the central region of the oxidation reactor can be recovered as an aqueous hydrogen peroxide solution in step (7). Simple Explanation of the Diagram

[0018] [Figures 1 to 3] schematically illustrate the flow configuration of the process flow according to the prior art (Figure 1) and the present invention (Figures 2 and 3), wherein device 1 is an oxidation reactor, device 2 is an extraction tower, device 3 is a degasser or a combined degasser / decanter device, WS is an organic working solution and DMW is demineralized water. Implementation

[0019] Before describing the formulations of the present invention, it should be understood that the invention is not limited to the specific embodiments described, as such embodiments can vary (naturally). It should also be understood that the terminology used herein is not intended to be restrictive, as the scope of the invention will be limited only by the appended claims.

[0020] As used herein, the terms "comprising," "comprises," and "consisting of" are synonymous with "including," "includes," "containing," and "contains," and are inclusive or open-ended, not excluding additional, unlisted members, elements, or method steps. It will be understood that the terms "comprising," "comprises," and "consisting of" as used herein include the terms "consisting of," "consists," and "consists of."

[0021] Throughout this application, the term "about" is used to indicate that a value includes the standard deviation of the error of the device or method used to determine that value.

[0022] As used herein, the terms "% by weight", "wt.-%", "weight percentage" or "percentage by weight" are used interchangeably.

[0023] The range of values ​​listed by endpoints includes all integers and (where appropriate) fractions contained within that range (e.g., 1 to 5, which may include 1, 2, 3, 4 when referring to, for example, the number of elements, and 1.5, 2, 2.75, and 3.80 when referring to, for example, measurements). The endpoint list also includes the endpoint values ​​themselves (e.g., from 1.0 to 5.0 includes both 1.0 and 5.0). Any range of values ​​listed here is intended to include all subranges contained therein.

[0024] All references cited in this specification are incorporated herein by reference in their entirety. In particular, the teaching content of all references specifically mentioned herein is incorporated by reference.

[0025] Unless otherwise defined, all terms used in disclosing this invention, including technical and scientific terms, have the meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. In particular, the reactors used in the methods of this invention are those commonly used in the prior art, unless otherwise indicated.

[0026] With further guidance, terminology definitions are included to better understand the teachings of this invention.

[0027] In the following paragraphs, different alternatives, implementations, and variations of the invention are defined in more detail. Each alternative and implementation thus defined may be combined with any other alternative and implementation when the range of values ​​for the same parameter is separated, and this applies to each variation unless explicitly stated otherwise or clearly incompatible. In particular, any feature indicated as preferred or advantageous may be combined with one or more other features indicated as preferred or advantageous.

[0028] Furthermore, in one or more embodiments, the specific features, structures, or characteristics described herein may be combined in any suitable manner as will be apparent to those skilled in the art from the disclosure. Moreover, while some embodiments described herein include certain features (in addition to those included in other embodiments), combinations of features from different embodiments are intended to be within the scope of the invention and to form different embodiments, as will be understood by those in the art.

[0029] This invention relates to a method for producing hydrogen peroxide via the anthraquinone process, wherein the method comprises the following steps: (1) Hydrogenating an organic working solution containing one or more anthraquinone derivatives in a hydrogenation reactor in the presence of a heterogeneous catalyst to obtain a hydrogenated organic working solution containing one or more hydrogenated anthraquinone derivatives; (2) The hydrogenated organic working solution obtained in step (1) is oxidized in an oxidation reactor, which is divided into an upper region, a middle region and a lower region. The hydrogenated organic working solution obtained in step (1) is introduced into the upper region of the oxidation reactor and oxygen-containing gas is introduced into the lower region of the oxidation reactor to form hydrogen peroxide in a countercurrent process and obtain an oxidized organic working solution containing hydrogen peroxide. (3) The oxidized organic working solution containing hydrogen peroxide obtained in step (2) is sent to a combined degasser / decanter device, or the oxidized organic working solution containing hydrogen peroxide obtained in step (2) is directly decanted in the lower region of the oxidation reactor, and then the oxidized organic working solution containing dissolved hydrogen peroxide is sent to the degasser to expand the entrained gas and degas the oxidized organic working solution containing hydrogen peroxide; (4) The degassed and oxidized organic working solution obtained in step (3) is introduced into the lower part of the extraction tower and combined with the aqueous solution to form an aqueous phase and an organic phase containing hydrogen peroxide; (5) Remove the aqueous phase obtained in step (4) from the lower part of the extraction tower and remove the organic phase from the upper part of the extraction tower and return the organic phase to the hydrogenation reactor; (6) At least a portion of the aqueous phase removed from the extraction tower in step (5) is returned to the central region of the oxidation reactor; and (7) Recover hydrogen peroxide aqueous solution.

[0030] The term "alkylanthraquinone derivative" is intended to refer to 9,10-anthraquinones substituted at the 1, 2, or 3 positions with at least one straight-chain or branched aliphatic alkyl side chain containing at least one carbon atom. Typically, such alkyl chains contain fewer than 9 carbon atoms, and preferably fewer than 6 carbon atoms. Examples of such alkylanthraquinone derivatives are ethylanthraquinones such as 2-ethylanthraquinone (EQ), 2-isopropylanthraquinone, 2-secondary and 2-tertiary-butylanthraquinones (BQ), 1,3-, 2,3-, 1,4-, and 2,7-dimethylanthraquinones, pentylanthraquinones (AQ) such as 2-iso- and 2-tertiary-pentylanthraquinones, and mixtures of such quinones.

[0031] The term "tetrahydroalkylanthraquinone derivative" is intended to refer to 9,10-tetrahydroquinone corresponding to the 9,10-alkylanthraquinone specified above. Thus, for EQ and AQ, they are specified by ETQ and ATQ respectively, and their reduced forms (tetrahydroalkylanthraquinone) are ETQH and ATQH respectively.

[0032] Preferably, use AQ or EQ or a mixture of both.

[0033] The term "combined degasser / decanter" is intended to refer to a single container or device that performs both degassing and decantation functions simultaneously. Alternatively, a combined degasser / decanter can be two different and continuous containers or devices that are connected to each other directly or by means of other devices.

[0034] In the first method step of this invention, an organic working solution containing one or more anthraquinone derivatives is hydrogenated in the presence of a heterogeneous catalyst to obtain an organic working solution containing one or more hydrogenated anthraquinones, also referred to as a hydrogenated organic working solution. Working solutions that can be hydrogenated in this method step are known in the art. Suitable working solutions typically comprise an inert solvent that dissolves the anthraquinone derivative and the anthraquinone derivative used, or a mixture of solvents, wherein one solvent dissolves the anthraquinone derivative and another solvent dissolves the anthraquinone derivative used.

[0035] The organic solvent in the working solution is typically a mixture of two solvents: one is a good solvent for dissolving one or more quinones (usually a nonpolar solvent, such as a mixture of aromatic compounds), and the other is a good solvent for dissolving one or more hydroquinones (usually a polar solvent, such as a long-chain alcohol). Several suitable solvents are known in the prior art. Examples of polar solvents commonly used in AO processes are diisobutylmethanol (DIBC), trioctyl phosphate (TOP), tetrabutylurea (TBU), and 2-methylcyclohexyl acetate (Sextate). Examples of nonpolar solvents are S150, and heavy aromatic solvents such as naphtha (C9 / C10), commercially known, but not exclusively, Solvesso 150, Caromax, or Shellsol A150.

[0036] Suitable heterogeneous catalysts that can be used in the methods of the present invention are well known in the prior art. The heterogeneous catalyst may be selected from palladium, platinum, gold, molybdenum, ruthenium, rhodium, nickel, and mixtures thereof, and may include a support. Furthermore, the catalyst may be a fixed-bed or slurry catalyst.

[0037] According to the present invention, the hydrogenated organic working solution is separated from the heterogeneous catalyst before being introduced into the oxidation reactor for oxidation reaction. This can be done by any method known in the prior art.

[0038] In the method of this invention, one or more acidifying compounds and one or more stabilizing compounds may be added, with the aim of reducing the decomposition of the generated hydrogen peroxide and improving the separation of the organic phase and the aqueous phase.

[0039] The acidifying compound can be selected from inorganic acids intended to maintain the pH of the solution within an acidic range (preferably between 0 and 6). The acid used is typically selected from sulfuric acid, nitric acid, and phosphoric acid, or mixtures of two or more of these acids.

[0040] Stabilizing compounds are typically inorganic salts of stannic acid, carboxylic acid such as citric acid, or phosphorus-containing acids, or mixtures of two or more of these stabilizing compounds. Good results can be obtained using stabilizing compounds such as alkali metal stannates, pyrophosphates, metaphosphates, and polyphosphates, and mixtures thereof.

[0041] Inorganic salts are defined as compounds in which all hydrogen atoms of the corresponding acid have been replaced by one or more metal atoms, and compounds in which only a portion of the hydrogen atoms of the acid have been replaced by one or more metal atoms and the acidic nature of the acid is still present.

[0042] In the method of this invention, both an acidifying compound and a stabilizing compound may be added to any liquid stream entering device 1 (oxidation reactor) and / or device 2 (extraction tower) and / or device 3 (degasser or combined degasser / decanter). According to the invention, preferably, the oxidation reactor of the tower is divided into three zones: an upper zone, a middle zone, and a lower zone.

[0043] Preferably, the central region of the oxidation reactor is a region where the level of introducing oxygen-containing gas is higher than the level of introducing the organic working solution into the oxidation reactor.

[0044] Furthermore, preferably, the central region of the oxidation reactor includes internal components that promote the reaction. More preferably, these internal components are selected from the group consisting of trays, packing materials, and combinations thereof, wherein the trays are preferably porous trays. Preferably, the central region of the oxidation reactor includes trays. Additionally, preferably, the upper and / or lower regions of the oxidation reactor do not include trays.

[0045] Furthermore, preferably, the upper region of the oxidation reactor is a gas-liquid separation section, the middle region is an oxidation reaction section, and the lower region is a hydrogen peroxide settling section. More preferably, it is a decantation section for transferring the working solution to the degasser, or a collection section for transferring the collected fluid to the combined degasser / decanter.

[0046] The oxidation reactor used in this invention operates in countercurrent flow, i.e., an oxygen-containing gas, preferably selected from a group consisting of air, a mixture of oxygen and an inert gas, a mixture of air and oxygen, and combinations thereof, enters the lower region of the oxidation reactor, while a hydrogenated organic working solution enters the upper region of the oxidation reactor. Operating in a countercurrent rather than a cocurrent configuration (as described, for example, in CN 106672911, where both the oxygen-containing gas and the hydrogenated organic working solution are introduced into the lower region of the oxidation reactor) provides significant advantages because it makes it easier to separate the exhaust gas from the working solution at the top of the reactor. Furthermore, by operating in a countercurrent configuration, the risk of mist formation is reduced; this mist can be an explosive mixture and can be ignited by a spark, leading to an explosion.

[0047] Preferably, the oxidation reactor of the present invention operates at a temperature between about 50°C and about 68°C, more preferably between about 52°C and about 65°C, and even more preferably between about 57°C and 62°C. To ensure that the oxidation reactor operates at the optimal temperature, the oxidation reactor may include one or more coolers. The number of coolers depends on the operating flow rate and can be readily determined by those skilled in the art.

[0048] The oxidation reactor is preferably operated at a pressure between about 1 and about 10 bar, between about 1.5 and about 9.5 bar, between about 3 and about 9 bar, between about 4 and about 8.5 bar, and more preferably between about 5 and about 8 bar.

[0049] The residence time of the working solution used to carry out the oxidation reaction in a sufficient manner in the oxidation reactor is preferably from about 7 to about 40 minutes, more preferably from about 10 to about 35 minutes, or from about 12 to about 20 minutes.

[0050] The local hydrogen peroxide concentration in the oxidation reactor can be controlled from about 0 to about 70 wt.-%, especially from about 25 to about 55 wt.-%, and more preferably from about 40 to about 52 wt.-%.

[0051] The oxidized organic working solution containing hydrogen peroxide obtained in step (2) of the method of the present invention is preferably fed to a degasser / decanter device via multiple or a single pipe / flue to expand the entrained gas and degas the oxidized organic working solution. The device is operated at an operating pressure slightly above the range of about 0.05 to about 1.50 bar gauge pressure, preferably from about 0.1 to about 1.0 bar gauge pressure.

[0052] In a preferred embodiment of the method of the present invention, the degasser or combined degasser / decanter device is equipped with internal components to aid degassing; and the decanter in the combined degasser / decanter is empty or contains a coalescing medium such as packing material to aid decanting.

[0053] The working solution is held in a combined degasser / decanter unit for a certain period of time to allow degassing and decantation, or the working solution is held in a degasser for a certain period of time to allow degassing.

[0054] According to the invention, after degassing (and decanting as needed) the working solution, the degassed (and decanted as needed) oxidized working solution is introduced into the lower portion of the extraction tower and preferably combined with an aqueous solution in a countercurrent process to form an aqueous phase and an organic phase containing hydrogen peroxide. For the countercurrent process, an aqueous solution of demineralized water (DMW) is preferably added to the upper portion of the extraction tower.

[0055] Due to their density difference, the aqueous phase containing hydrogen peroxide can be removed from the lower part of the extraction tower, while the organic phase can be removed from the upper part of the extraction tower and recycled back to the hydrogenation reactor to continue the AO process.

[0056] Compared to prior art methods where the (crude) hydrogen peroxide aqueous solution is only recovered from the extraction tower, according to the present invention, at least a portion, preferably the entire amount, of the aqueous phase containing hydrogen peroxide removed from the extraction tower is guided back to the oxidation reactor. However, according to the present invention, a portion of the aqueous phase containing hydrogen peroxide removed from the extraction tower and not guided back to the central region of the oxidation reactor can be recovered as an aqueous hydrogen peroxide solution.

[0057] At least a portion of the aqueous phase obtained from the extraction tower is introduced into the central region of the oxidation reactor as defined above. The precise location of the inlet point for the aqueous recirculation stream into the oxidation reactor is determined by balancing the hydrogen peroxide concentration of the aqueous phase recirculated back to the oxidation reactor with the hydrogen peroxide concentration already present in the aqueous phase droplets within the oxidation reactor. Specifically, the aqueous phase should be introduced into the oxidation reactor in a manner that matches the hydrogen peroxide concentration already present in the oxidation reactor; this occurs in the central region of the oxidation reactor.

[0058] When the aqueous phase removed from the extraction column is added back to the central region of the oxidation reactor, a portion of the hydrogen peroxide formed in the organic working solution within the oxidation reactor is extracted into the aqueous phase from the extraction column. By mass balance, the hydrogen peroxide concentration in the formed aqueous phase is inversely proportional to the flow rate of the recirculated aqueous phase from the extraction column. In summary, the hydrogen peroxide concentration in the oxidation reactor is at its highest value when there is no recirculation flow, and at its lowest value when the entire flow rate of the aqueous phase from the extraction column is returned to the oxidation reactor.

[0059] By recirculating at least a portion of the aqueous phase from the extraction tower back to the central region of the oxidation reactor, any hydrogen peroxide concentration within the oxidation reactor can be controlled. In particular, high localized hydrogen peroxide concentrations exceeding safety limits can be avoided within the oxidation reactor. This achieves the goal of keeping the hydrogen peroxide concentration within a safe operating range.

[0060] In addition to the advantage of controlling the hydrogen peroxide concentration within the oxidation reactor, there is also the chemical advantage of recycling at least a portion of the aqueous phase obtained from the extraction tower to the central region of the oxidation reactor. By recycling at least a portion of the aqueous phase containing hydrogen peroxide to the central region of the oxidation reactor, the average concentration of hydrogen peroxide in the oxidation reactor is reduced, thereby reducing the formation of undesirable 6-alkyl-1,2,3,4-tetrahydro-4a,9a-epoxyanthracene-9,10-dione substances.

[0061] According to the present invention, the recovery of hydrogen peroxide aqueous solution can be carried out in the following two ways: (a) The aqueous hydrogen peroxide solution can be removed directly from the lower region of the oxidation reactor (preferably by decantation, since the aqueous phase forms a denser separated phase at the bottom of the oxidation reactor); or (b) The oxidized working solution containing the aqueous phase returned to the central region of the oxidation reactor in step (6) is sent to a degasser / decanter device, wherein the oxidized organic working solution is decanted to obtain an aqueous phase containing hydrogen peroxide and the hydrogen peroxide aqueous solution can then be removed from the device.

[0062] The separation of the aqueous hydrogen peroxide solution from the oxidized organic working solution in the oxidation reactor, i.e., the recovery of the aqueous hydrogen peroxide solution, occurs due to the density difference between the two phases (aqueous and organic phases) generated by decantation. Decantation occurs in the lower region of the oxidation reactor or in the degasser / decanter unit. More preferably, decantation is achieved solely by the residence time and density difference between the two phases in the oxidation reactor or decanter / degasser unit, meaning the decantation section or decanter of the oxidation reactor does not contain coalescing media or any other internal components that facilitate decantation—the decantation section / decanter is empty.

[0063] However, according to the present invention, the oxidation reactor and / or degassing / decanting equipment may include facilities to improve decantation, such as structured packing. The internal components of the decantation unit may be made of stainless steel, polymers (e.g., PTFE, ETFE), ceramics, or mixtures of these materials.

[0064] The recovered hydrogen peroxide solution can be purified and / or concentrated by methods known in the art for further use.

[0065] As demonstrated in the examples, by using the novel process flow of the present invention and considering the composition of the organic working solution, particularly the composition of one or more solvents and anthraquinone derivatives in the organic solvent mixture, the method can be operated with a partition coefficient K of about 85 or higher, preferably about 100 or higher, and more preferably about 140 or higher, which is defined as... .

[0066] Furthermore, the method of the present invention exhibits high productivity, preferably higher than 14 g hydrogen peroxide / kg working solution. In particular, the method can be operated such that the productivity is about 8 to about 20 g hydrogen peroxide / kg working solution, preferably about 14 to 20 g hydrogen peroxide / kg working solution.

[0067] The invention will be further illustrated by the following examples. It should be understood that the following examples are for illustrative purposes only and are not intended to limit the invention thereto. [Example] [] []

[0068] The following equations and calculations demonstrate why and how the target hydrogen peroxide (H₂O₂) concentration can be achieved in an oxidation tower using the method of this invention: [Definition and Balance] [] []WS=Working solution w = water hp=H 2O 2 F = flow rate R = Recirculated flow from the extraction tower to the oxidation tower P = Product flow of aqueous phase leaving the production unit Prod = Productivity (g H₂O₂ / kg working solution) C = Concentration of H₂O₂ in the aqueous phase (% wt / wt) Dp = Residual water droplets M = the mass of H₂O₂ produced in the oxidizer by the reaction. K = (mass of hp in P / mass of w in P) / (mass of hp in WS / mass of WS) Example of traffic name naming: FWShpout - The flow rate of hydrogen peroxide leaving the working solution (leaving the oxidizer). A = the percentage of hp leaving P / the percentage of w leaving P B = the percentage of hp leaving the WS / the total mass of the WS. K = A / B - Distribution coefficient Total H₂O₂ entering = Total H₂O₂ leaving Total H₂O₂ entering = M + FRhpin The total H₂O₂ leaving = FWShpout + FPhpout The total amount of H2O2 leaving is equal to FWSout*A / K + Fwout*A. A = Total HP leaving / (FWSout / K + Fwout) The partition coefficient K can be changed by altering the concentration of the polar solvent and / or by changing the type of polar solvent in the working solution. The value of K can be determined by laboratory experiments by a person experienced in the art. [Example] [1-3] [Utilizing the recirculation of water flow from the extraction tower to the oxidation reactor.]

[0069] These calculation examples apply to Figures 2 and 3. In the case of Figure 2, the aquatic product stream P leaves device 1 (oxidation reactor) directly. When applying this example to Figure 3, it is assumed that the balance applies only to the oxidation tower (device 1), but the aquatic product P flows to device 3 (decanter) before leaving the system. Device 3 does not change the mass balance.

[0070] These instances include three variants: Example 1: By changing the distribution coefficient K, it can be demonstrated how the concentration of hydrogen peroxide in the product stream leaving the process can be kept constant by changing the flow rate and concentration of peroxide in the recirculated stream from the extraction tower to the oxidation tower. • Example 2: By changing the concentration and flow rate of hydrogen peroxide in the recirculated form from the extraction tower, the product concentration can be varied under constant productivity and / or distribution coefficient K. • Example 3: Varying productivity to demonstrate how the concentration of hydrogen peroxide in the product stream leaving the oxidizer or combined degasser / decanter can be kept constant, even with different productivity levels.

[0071] Three variations demonstrate that the concentration of hydrogen peroxide formed in the oxidation tower can be controlled and kept below a level that could form an explosive mixture with the organic matter in the oxidation tower. It is known that when the concentration of hydrogen peroxide in the aqueous solution is high, an explosive mixture can form between the hydrogen peroxide solution and the organic solution. Crucially, there must be a controllable system to regulate the concentration of hydrogen peroxide within the oxidation tower to avoid such explosive mixtures. The following examples illustrate how the concentration of hydrogen peroxide in the aqueous phase can be controlled to avoid such explosive mixtures.

[0072] The examples in Table 1 take into account that the total flow rate of the aqueous phase from the extraction tower is directed to the middle region of the oxidation tower and therefore all products are collected in the lower region of oxidation or in a combined degasser / decanter. [Equation] [] []FWSout=FWSin Mhp=FWSin*Prod / 1000 FPhpout=Mhp FPwout = FPhpout / CP * (100 - CP) FRwin=FPwout B = A / K = CP / (100-CP) / K FWShpout=B*FWSout FRhpin=FWShpout CRhpin=FRhpin / (FRhpin+FRwin)*100 [enter] [] []Prod K FWSin CP [Example] [4-6] [No recirculation from the extraction tower to the oxidation reactor]

[0073] These computational examples apply to Figure 1.

[0074] The instances that do not recycle from the extraction tower to the oxidizer fall into three variants. Example 4: Change the distribution coefficient K and calculate the concentration of hydrogen peroxide in the residual water droplets in the oxidizer. • Example 5: Since there is no recirculation flow, the conditions inside the oxidizer remain unchanged, but the concentration inside the extraction column can vary. Example 6: Modify productivity to demonstrate how to make the concentration of hydrogen peroxide in residual water droplets inside the oxidizer exceed the safety threshold.

[0075] In Table 2, the mass concentration of H₂O₂ (last row) is not calculated in the large aqueous phase because no water is added to Unit 2 due to the absence of a recirculation flow. Instead, the residual water entering the oxidizer is "wet" because the residual DMW and H₂O₂ that were not separated and dissolved in the WS in contact with the catalyst in the extraction tower are converted into water.

[0076] The residual water exists in droplet form and is mixed with the working solution of hydrogenation entering the oxidizer. This results in the formation of a mixture that can propagate detonation if the concentration of hydrogen peroxide exceeds a certain level. [Equation] [] []FWSout=FWSin FRwin-Input Zero FRhpin-Input Zero CRhpin-Input Zero FPwout=FRwin FPhpout=Mhp FWShpout=B*FWSout Mhp=FWSin*Prod / 1000 B=Mhp / FWSout DpRatio=B*K DpConc=DpRatio / (DpRatio+1)*100 [enter] [] []Prod K FWSin FRhpin CRhpin FPwout

[0077] By comparing Table 1 and Table 2, particularly the column on "variation of partition coefficient K", it can be observed that in this invention, regardless of the partition coefficient K (which varies between 115 and 206), the same product concentration of 45% can be obtained in the oxidation reactor when the recirculation flow is applied.

[0078] As can be observed from Table 2, without a recirculation flow from the extraction tower to the oxidation reactor, the concentration of hydrogen peroxide in the residual water droplets within the oxidation reactor can reach >66%. In the example, at a productivity of 17 g H₂O₂ / kg WS, a residual water droplet concentration of 66% to 78% was obtained in the oxidation reactor. Such concentrations are well beyond the safe operating range. According to the present invention, the oxidation reactor can be operated safely when the operating productivity of hydrogen peroxide in the working solution is >14 g / kg, or alternatively referred to as "high productivity".

[0079] It is only possible to operate without aqueous solution recirculation and keep the hydrogen peroxide concentration within safe operating limits when the partition coefficient is approximately below 140 (e.g., 85) and the productivity is 8 g / kg. Very low partition coefficient values ​​lead to poor operation of the extraction column.

[0080] By specifically comparing the "Changes in Recycled Concentration from Extraction" column in Tables 1 and 2, it is demonstrated that the target hydrogen peroxide concentration can be achieved using the method of the present invention. In these examples, considering a productivity of 17 g / kg and a distribution coefficient of 115, the concentration is controlled between 40% and 50%, while the concentration would be 66% without the recycle stream. The table shows that the concentration of hydrogen peroxide formed in the oxidizer can be controlled by controlling the flow rate and concentration of hydrogen peroxide entering the oxidation tower from the extraction tower. In the examples in Table 1, in the present invention, the concentration of hydrogen peroxide formed in the oxidizer varies between 40% and 50%, with a constant productivity and distribution coefficient K. In fact, by changing the flow rate and concentration of the recycle stream entering the oxidation tower from the extraction tower, a target concentration of up to 66% can be achieved (examples in Table 2). By introducing a recycle stream into the oxidation reactor, the exact desired H₂O₂ concentration of hydrogen peroxide can be predicted and achieved. In the absence of a recirculating flow, the H₂O₂ concentration in the residual water droplets is always determined solely by the partition coefficient K and the productivity.

[0081] By comparing Table 1 and Table 2, particularly the column on "Changes in Productivity", it can be observed that in this invention, when the productivity of WS is changed under a constant distribution coefficient K, the same target H2O2 concentration of 45.0% can be obtained in the case of a recirculating flow.

[0082] Without a recirculation flow, the concentration of residual water droplets within the oxidizer reaches 53% to 72%, exceeding the safe operating range. This means that operating at high productivity without a recirculation flow is dangerous. Conversely, this invention allows for operation at high productivity (>14 g H₂O₂ / kg WS) with negligible safety risks.

[0083] In order to maintain safe operating conditions without recirculation, the equipment must operate at low productivity and low allocation coefficient, resulting in low operating efficiency.

[0084] In summary, recycling at least a portion of the aqueous phase removed from the extraction tower back to the central region of the oxidation reactor has the following advantages: · [Improved separation of organic and gas phases at the top of an oxidation reactor:] When it is necessary to separate two phases in the headspace of an oxidation reactor, the formation of hazardous explosive mists in the headspace of the oxidation reactor can be greatly reduced by allowing the organic solution to flow downward along the oxidation reactor and by allowing air to flow upward countercurrently along the oxidation reactor. · [Controlling the concentration of hydrogen peroxide within the oxidation reactor:] The concentration of hydrogen peroxide within the oxidizer is independent of the reaction productivity (g / kg) and the partition coefficient K. The controlled intensity generated from the oxidation column eliminates the need for distillation columns further downstream in the process. · [Avoid developing high intensity] [H, 2, O, 2, ] [:] Combined with working at high productivity, the present invention allows for control of the concentration of the H2O2 aqueous solution formed in the oxidation tower and avoids the concentration from exceeding the safety limit. · [Improve extraction efficiency]: The mixing of aqueous and organic solutions within the oxidizer results in an additional stage of H₂O₂ extraction, which leads to an increase in overall extraction efficiency. · [Low-level] [6-] [alkyl] [-1,2,3,4-] [Tetrahydrogen] [-4a,9a-] [Epoxyanthracene] [-9,10-] [Diketone formation rate]: It is known that the combination of hydroquinone with H₂O₂ increases the formation rate of 6-alkyl-1,2,3,4-tetrahydro-4a,9a-epoxyanthracene-9,10-dione. This is a reversible process. During reversal, there is loss, which leads to higher quinone consumption. By reducing the concentration of H₂O₂ in contact with the WS (when H₂O₂ moves into the aqueous phase), a reduced epoxide formation rate is achieved, which subsequently reduces quinone consumption.

Claims

1. A method for producing hydrogen peroxide via the anthraquinone process, wherein, The method includes the following steps: (1) hydrogenating an organic working solution containing one or more anthraquinone derivatives in a hydrogenation reactor in the presence of a heterogeneous catalyst to obtain a hydrogenated organic working solution containing one or more hydrogenated anthraquinone derivatives; (2) The hydrogenated organic working solution obtained in step (1) is oxidized in an oxidation reactor divided into an upper region, a middle region, and a lower region. The oxidation is achieved by introducing the hydrogenated organic working solution obtained in step (1) into the upper region of the oxidation reactor and introducing oxygen-containing gas into the lower region of the oxidation reactor to form hydrogen peroxide in a countercurrent process and obtain an oxidized organic working solution containing hydrogen peroxide. The middle region of the oxidation reactor is a region higher than the level at which the oxygen-containing gas is introduced and lower than the level at which the organic working solution is introduced into the oxidation reactor. (3) The oxidized organic working solution containing hydrogen peroxide obtained in step (2) is sent to a combined degasser / decanter device, or the oxidized organic working solution containing hydrogen peroxide obtained in step (2) is directly decanted in the lower region of the oxidation reactor, and then the oxidized organic working solution containing dissolved hydrogen peroxide is sent to a degasser to expand the entrained gas and degas the oxidized organic working solution containing hydrogen peroxide. (4) (3) The degassed and oxidized organic working solution obtained in step (3) is introduced into the lower part of the extraction tower and combined with the aqueous solution to form an aqueous phase and an organic phase containing hydrogen peroxide; (5) The aqueous phase obtained in step (4) is removed from the lower part of the extraction tower and the organic phase is removed from the upper part of the extraction tower and returned to the hydrogenation reactor; (6) At least a portion of the aqueous phase removed from the extraction tower in step (5) is returned to the middle region of the oxidation reactor; and (7) The aqueous hydrogen peroxide solution is recovered.

2. The method as described in claim 1, wherein, In step (7), the hydrogen peroxide aqueous solution is recovered by removing it from the lower region of the oxidation reactor.

3. The method as described in claim 1, wherein, In step (7), the oxidized organic working solution containing the aqueous phase returned to the central region of the oxidation reactor in step (6) is sent to the degasser / decanter device to recover the hydrogen peroxide aqueous solution, wherein the oxidized organic working solution is decanted to obtain an aqueous phase and an organic phase containing hydrogen peroxide and the aqueous phase containing hydrogen peroxide is removed from the device.

4. The method as described in claim 1, 2, or 3, wherein, The portion of the aqueous phase containing hydrogen peroxide obtained in step (5) that is not returned to the central region of the oxidation reactor is recovered as an aqueous hydrogen peroxide solution in step (7).

5. The method as described in claim 1, 2, or 3, wherein, The central region of the oxidation reactor includes internal components that facilitate the reaction.

6. The method as described in claim 1, 2, or 3, wherein, The upper region of the oxidation reactor is a gas-liquid separation section, the middle region of the oxidation reactor is an oxidation reaction section, and the lower region of the oxidation reactor is a hydrogen peroxide settling section and / or a collection section.

7. The method as described in claim 1, 2, or 3, wherein, The oxygen-containing gas is selected from the group consisting of air, mixtures of oxygen and inert gases, mixtures of air and oxygen, and combinations thereof.

8. The method as described in claim 1, 2, or 3, wherein, This aqueous solution contains demineralized water.

9. The method as described in claim 1, 2, or 3, wherein, The oxidation reactor includes one or more coolers.

10. The method as described in claim 1, 2, or 3, wherein, The oxidation reactor operates at a pressure between approximately 1 and approximately 10 bar gauge pressure.

11. The method as described in claim 1, 2, or 3, wherein, The local concentration of hydrogen peroxide present in the oxidation reactor was controlled from 0 to approximately 70 wt.%.

12. The method as described in claim 1, 2, or 3, wherein, The degasser or the combined degasser / decanter equipment is equipped with internal components to aid degassing, and the decanter in the combined degasser / decanter is either empty or contains a coalescing medium to aid decanting.

13. The method as described in claim 1, 2, or 3, wherein, The organic working solution obtained in step (3) is combined with the aqueous solution in step (4) in a countercurrent process.

14. The method as described in claim 1, 2, or 3, wherein, One or more solvents of the organic working solution and the anthraquinone derivative are selected such that the method operates with a partition coefficient K of about 85 or higher, which is defined as follows:

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