Method for producing hydrogen peroxide

Abstract

The present invention relates to a method for producing hydrogen peroxide by means of the AO process, the method comprising the two alternating steps of: hydrogenating a working solution in the presence of a catalyst, the working solution containing at least one quinone dissolved in at least one organic solvent, to obtain at least one corresponding hydroquinone; and oxidizing the at least one hydroquinone; wherein the solvent has the following formula (I): [Chem 6] in which n is an integer greater than or equal to 8.

Description

[0001] DESCRIPTION

[0002] TITLE: Process for producing hydrogen peroxide

[0003] The present invention relates to a process for producing hydrogen peroxide from a quinone using, as organic solvent, a lactone as described below.

[0004] The invention also relates to the use of at least one organic solvent, as defined below, for dissolving a quinone, for the production of hydrogen peroxide.

[0005] The most common process for the production of hydrogen peroxide is the anthraquinone process. In such a process, also called a cyclic autoxidation (AO) process, a quinone is dissolved in a suitable organic solvent mixture, a so-called working solution, and is hydrogenated to form the corresponding hydroquinone. The hydroquinone is then reoxidized to quinone with oxygen (usually air) with the simultaneous formation of hydrogen peroxide, which can then be extracted with water while the quinone is returned with the working solution to the hydrogenation step.

[0006] The anthraquinone process is widely described in the literature, for example in Kirk-Othmer, "Encyclopedia of Chemical Technology", 49 Ed., 1993, Vol. 13, pp. 961-995.

[0007] For the process to work properly, it is necessary to use a solvent mixture for the working solution in which both quinones and hydroquinones are soluble. Therefore, the solvent mixture in the working solution usually includes one or more solvents for quinones and one or more solvents for hydroquinones. Quinones dissolve easily in non-polar aromatic solvents, while hydroquinones dissolve well in polar solvents.

[0008] For quinones, various aromatic solvents are proposed in the literature such as benzene, xylene (US 2,158,525), trimethylbenzene (GB 747,190), tetramethylbenzene (WO 2001 / 098204) and mixtures of polyalkylated benzenes (US 3,328,128, EP 3,342750, FR 1,406,409).

[0009] In addition, some nitrogen compounds are also known as solvents for hydroquinones. The uses of carboxylic acid amides (US 4,046,868), substituted ureas (US 3,767,778), alkyl-substituted pyrrolidones (US 4,394,369) and alkyl-substituted caprolactams (EP 0 286 610) are described in the literature.

[0010] However, aromatic solvents already proposed in the literature are mostly flammable and produce explosive vapors when mixed with oxygen or air (implying serious fire and explosion risks in a large-scale commercial plant).

[0011] Furthermore, such organic solvents also have the disadvantage of being synthesized from raw materials that are often expensive and / or not environmentally friendly.

[0012] In view of the above, there is therefore a real need to implement an appropriate solvent, in particular a bio-sourced and renewable solvent, for the production of hydrogen peroxide, in order to reduce the costs of the process and improve its performance in terms of safety and productivity.

[0013] In other words, one of the aims of the present invention is in particular to improve the performance of a process for producing hydrogen peroxide.

[0014] The present invention therefore relates in particular to a process for producing hydrogen peroxide comprising at least the two alternating stages of: hydrogenation of a working solution in the presence of one or more catalysts, said working solution comprising at least one quinone dissolved in at least one organic solvent, to obtain at least one corresponding hydroquinone; and oxidation of at least said hydroquinone; said organic solvent being a lactone corresponding to the following formula (I):

[0015] [Chem 1]

[0016] GB O (I) in which n is an integer greater than or equal to 8.

[0017] The present invention thus makes it possible to achieve the objectives as described above thanks to the use of a solvent of formula (I) having the advantage of being biosourced and renewable and the implementation of which in a hydrogen production process leads to an improvement in its performance, in particular in terms of safety and yield, while effectively reducing its costs. Thus the organic solvent of formula (I) makes it possible to improve the safety and productivity of a hydrogen peroxide production unit.

[0018] The organic solvent also has the advantage of separating easily from water during the step of extracting hydrogen peroxide from the working solution.

[0019] The process according to the invention can advantageously lead to a hydrogen peroxide solution having a high purity.

[0020] In particular, hydroquinones exhibit increased solubility in such a solvent, which allows the process to be carried out at a lower temperature, thus reducing the costs associated with the production of hydrogen peroxide and the risks associated with the flammability of the solvent.

[0021] Additionally, at increased solubility, reaction rates can increase which allows for increased process productivity.

[0022] The present invention further relates to the use of at least one organic solvent for dissolving a quinone in a working solution for the production of hydrogen peroxide, wherein the organic solvent is a lactone of formula (I) as described above.

[0023] In particular, the invention relates to the use of at least one organic solvent of formula (I) for improving the solubility of a hydroquinone.

[0024] Other objects, characteristics, aspects and advantages of the invention will appear even more clearly on reading the description and the example which follows.

[0025] In what follows, and unless otherwise indicated, the limits of a domain of values ​​are included in this domain, in particular in the expressions "between" and "ranging from ... to ...".

[0026] Furthermore, the expression "at least one" used in this description is equivalent to the expression "one or more".

[0027] Further, the term "at least" as used in this description is equivalent to the term "greater than or equal to."

[0028] Finally, in a manner known per se, we designate by compound or group in C n or in Cn a compound or group containing in its chemical structure n carbon atoms.

[0029] Working solution As indicated above, the working solution comprises at least one organic solvent corresponding to a lactone of formula (I):

[0030] [Chem 2]

[0031] C n H(^-2)O (I) in which n is an integer greater than or equal to 8

[0032] According to the present invention, by "lactone" is meant a class of compounds having at least one ester function in a cycle.

[0033] According to a preferred general characteristic of the invention, in formula (I), n varies from 8 to 14, preferably from 9 to 13, even more preferably from 10 to 13, in particular from 10 to 12.

[0034] According to a further preferred general characteristic of the invention, the organic solvent is a lactone with a 5-membered ring, substituted or not (γ-lactone), or 6-membered ring, substituted or not (δ-lactone), or 7-membered ring, substituted or not (β-lactone).

[0035] Preferably, the organic solvent is a 5-membered ring lactone, substituted or unsubstituted, or a 6-membered ring lactone, substituted or unsubstituted.

[0036] As substituents, mention may in particular be made of substituents chosen from the group consisting of a linear or branched alkyl group comprising from 1 to 10 carbon atoms, preferably from 1 to 8 carbon atoms, in particular methyl, ethyl, butyl and heptyl, a hydroxy group, an amine, a halogen atom such as a fluorine, chlorine, bromine and iodine atom, or combinations thereof.

[0037] Preferably, when the organic solvent is a substituted lactone then the substituent(s) may be one or more alkyl groups, linear or branched, comprising from 1 to 10 carbon atoms, preferably 1 to 8 carbon atoms, for example methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl or decyl, and combinations thereof.

[0038] Preferably, the organic solvent has a flash point greater than or equal to 60°C, which advantageously limits the risks of fire linked to the flammability of the solvent.

[0039] More preferably, the organic solvent has a flash point greater than or equal to 62.5°C and even more preferably greater than or equal to 65°C. The flash point can be determined by a closed cup apparatus according to standard ASTM-D3278.

[0040] Preferably, n varies from 8 to 14, preferably from 10 to 12, and the organic solvent has a flash point greater than or equal to 60°C.

[0041] More preferably, n varies from 10 to 12 and the organic solvent has a flash point greater than or equal to 65°C.

[0042] Preferably, the organic solvent has a vapor pressure less than or equal to 450 Pa measured at a temperature of 20°C, which makes it possible to keep the vapors in the reactors below the explosive limits at all times even when the reaction is carried out at high temperatures.

[0043] More preferably, the organic solvent has a vapor pressure of less than or equal to 400 Pa, even more preferably less than or equal to 350 Pa measured at a temperature of 20°C. For example, the solvent of formula (I) may have a vapor pressure of less than or equal to 450 Pa, or less than or equal to 400 Pa, or less than or equal to 350 Pa, or less than or equal to 300 Pa, or less than or equal to 250 Pa, or less than or equal to 200 Pa, or less than or equal to 250 Pa, or less than or equal to 200 Pa, or less than or equal to 150 Pa, or less than or equal to 100 Pa, at 20°C.

[0044] Vapor pressure can be determined by ebulliometry according to ASTM-E1719.

[0045] Preferably, n varies from 8 to 14, preferably from 10 to 14, and the organic solvent has a vapor pressure less than or equal to 450 Pa measured at a temperature of 20°C.

[0046] Advantageously, the organic solvent has a solubility in water of less than or equal to 2000 mg / kg at a temperature of 25°C.

[0047] Such reduced water solubility for the organic solvent helps to reduce solvent loss especially during the extraction step of the process (in which the oxidized working solution is treated with water to extract hydrogen peroxide). In addition, such reduced water solubility for the organic solvent helps to provide a crude hydrogen peroxide solution of higher purity.

[0048] Preferably, the organic solvent is insoluble (or essentially insoluble) in water, and preferably has a solubility of less than or equal to 1500 mg / kg, preferably less than or equal to 1200 mg / kg, measured at a temperature of 25°C. The solubility in water can be determined by coulometric Karl Fischer titration according to ASTM-D6304.

[0049] Preferably, n ranges from 8 to 14, preferably from 10 to 14, and the organic solvent has a solubility of less than or equal to 1500 mg / kg, preferably less than or equal to 1200 mg / kg, measured at 25°C.

[0050] Advantageously, the organic solvent has a specific density strictly less than 1, which facilitates the separation of the solvent from the water during the step of extracting hydrogen peroxide from the working solution.

[0051] Preferably, the organic solvent has a specific gravity less than or equal to 0.97, preferably varying from 0.89 to 0.97.

[0052] Specific gravity can be determined using a hydrometer in accordance with ASTMD891.

[0053] Preferably, n varies from 8 to 14, preferably from 10 to 14, and the organic solvent has a specific density strictly less than 1, preferably a specific density less than or equal to 0.97.

[0054] The organic solvent is preferably selected from the group consisting of γ-octalactone, δ-octalactone, γ-nonalactone, δ-nonalactone, 3-methyl-γ-octalactone, γ-decalactone, δ-decalactone, β-decalactone, 4-methyl-γ-nonalactone, 4-ethyl-γ-octalactone, 4-methyl-7-isopropyl-β-heptalactone, γ-undecalactone, δ-undecalactone, 3-methyl-γ-decalactone, γ-dodecalactone, δ-dodecalactone, γ-tridecalactone, γ-tetradecalactone, and mixtures thereof.

[0055] Preferably, the organic solvent is γ-octalactone, δ-dodecalactone, and mixtures thereof.

[0056] More preferably, the organic solvent is δ-dodecalactone.

[0057] The organic solvent of formula (I) may be present in the working solution in an amount of 70 to 99.9% by weight, and preferably 80 to 99% by weight, relative to the total weight of the working solution.

[0058] For example, the organic solvent of formula (I) may be present in the working solution in an amount of 70 to 75% by weight; or 75 to 80% by weight; or 80 to 85% by weight; or 85 to 90% by weight; or 90 to 95% by weight; or 95 to 99.9% by weight, relative to the total weight of the working solution.

[0059] The working solution may comprise a single organic solvent of formula (I). Alternatively, the working solution may comprise a mixture of organic solvents of formula (I), for example two or three or four organic solvents of formula (I).

[0060] The working solution used in the process according to the invention further comprises a quinone which is preferably an anthraquinone and more preferably chosen from an alkylanthraquinone or a tetrahydroalkylanthraquinone which is solubilized in the organic solvent of formula (I).

[0061] By "quinone" or "quinone derivatives" is meant a class of organic compounds having a benzene ring on which two hydrogen atoms are replaced by two oxygen atoms forming two carbonyl bonds.

[0062] For simplicity, the term "alkylanthraquinone" used in the description below will include both alkylanthraquinones and tetrahydroalkylanthraquinones.

[0063] Preferred alkyl substituents for alkylanthraquinones include amyl groups such as 2-tert-amyl or 2-iso-sec-amyl, ethyl, isopropyl, n-butyl, sec-butyl, tert-butyl and 2-hexenyl, and it is particularly preferred to include at least ethyl-substituted anthraquinones and / or tetrahydroanthraquinones. Thus, preferred alkylanthraquinones include 2-ethylanthraquinone, 2-isopropylanthraquinone, 2-n-butylanthraquinone, 2-sec-butylanthraquinone, 2-tert-butylanthraquinone, 2-amylanthraquinone, 2-sec-amylanthraquinone, 2-tert-amylanthraquinone or mixtures thereof, as well as 2-alkyl-5,6,7,8-tetrahydroanthraquinones and mixtures thereof with the corresponding 2-alkylanthraquinones.

[0064] According to a preferred embodiment, F alkylanthraquinone may be 2-ethylanthraquinone.

[0065] The quinone may be present in the working solution in an amount of 0.1 to 30% by weight, and preferably 1 to 20% by weight, relative to the total weight of the working solution.

[0066] For example, the quinone may be present in the working solution in an amount of 0.1 to 1 wt%; or 1 to 5 wt%; or 5 to 10 wt%; or 10 to 15 wt%; or 15 to 20 wt%; or 20 to 25 wt%; or 25 to 30 wt%. In some embodiments, the working solution comprises a single quinone.

[0067] Alternatively, the working solution includes a mixture of quinones, for example two or three or four quinones.

[0068] The working solution according to the invention may further comprise an additional solvent different from the organic solvent of formula (I).

[0069] The additional solvent may be a solvent for solubilizing quinone or a solvent for solubilizing hydroquinone (formed after hydrogenation of quinone). One or more additional solvents may be present in the working solution. For example, a first additional solvent for solubilizing quinone and a second additional solvent for solubilizing hydroquinone may be present in the working solution.

[0070] The additional solvent may be present in the working solution in a mass ratio relative to the organic solvent of formula (I) in the range from 0:1 to 3:1, preferably in the range from 0:1 to 2:1 and more preferably in the range from 0:1 to 1:1.

[0071] In the case where the additional solvent is intended for the solubilization of quinone (quinone solvent), this solvent may be a non-polar hydrocarbon preferably selected from aromatic, aliphatic or naphthenic hydrocarbons, among which aromatic hydrocarbons are most preferred. Preferred solvents of this type include benzene, alkylated or polyalkylated benzenes such as tert-butylbenzene or trimethylbenzene, alkylated toluenes or naphthalenes such as tert-butyltoluene or methylnaphthalene. The use of a commercial mixture of aromatic compounds marketed under the name Aromatic Solvent 150 (also known as CIO solvent) is possible. Aromatic Solvent 150 has the CAS number 64742-94-5 and is manufactured by distillation of aromatic streams derived from petroleum products.It is also known by other brand names such as Solvent Naphtha 150, Solvesso 150, Caromax 150, Shellsol A150 and Heavy Aromatic Solvent Naphtha 150.

[0072] In the case where the additional solvent is intended for the solubilization of hydroquinone (solvent for hydroquinone), this solvent may be a polar organic solvent preferably not soluble in water. Such a solvent may be selected from alcohols, ureas, amides, caprolactams, esters, phosphorus-containing substances and pyrrolidones, and may include alkyl phosphates (e.g. trioctyl phosphate), alkyl phosphonates, alkylcyclohexanol esters (e.g. 2-methyl-cyclohexyl acetate), N,N-dialkylcarbonamides, tetraalkylureas (e.g. tetrabutylurea), N-alkyl-2-pyrrolidones and high-boiling alcohols, preferably with 8 to 9 carbon atoms (e.g. diisobutylcarbinol). Preferred solvents for hydroquinones are selected from alkyl phosphates, tetraalkylureas, alkylcyclohexanol esters and high boiling alcohols.

[0073] Alternatively, the working solution according to the invention is free of any additional solvent.

[0074] Preferably, the working solution may consist of (or consist essentially of) the organic solvent of formula (I) and the quinone.

[0075] Process for producing hydrogen peroxide

[0076] As indicated above, the invention relates to a process for producing hydrogen peroxide, in particular by the AO process. Such a process comprises alternating steps of hydrogenation and oxidation of the working solution described above.

[0077] In other words, preferably, the invention relates to a process for producing hydrogen peroxide by the AO process comprising at least the two alternating steps of: hydrogenation of a working solution in the presence of one or more catalysts, said working solution comprising at least one quinone dissolved in at least one organic solvent, to obtain at least one corresponding hydroquinone; and oxidation of said at least one hydroquinone; the organic solvent being a lactone corresponding to the following formula (I): [Chem 3] working solution in contact with hydrogen gas. During this step, the quinone is hydrogenated to form a corresponding hydroquinone. This step is carried out in the presence of a catalyst. Such a catalyst may, for example, be a metal selected from nickel, palladium, platinum, rhodium, ruthenium, gold, silver or mixtures thereof. Preferred metals are palladium, platinum and gold, of which palladium or mixtures comprising at least 50% by weight of palladium are particularly preferred.

[0078] According to a preferred embodiment, the catalyst may be either in a free form, for example palladium black suspended in the working solution, or deposited on a solid support such as particles used in the form of a suspension or a fixed bed.

[0079] According to another preferred embodiment, the catalyst may be in the form of an active metal on a monolithic support, for example, as described in US Patents 4,552,748 and 5,063,043.

[0080] Preferred support materials may be selected from alumina, silica, aluminosilicates (silica-alumina), activated magnesia, titanium dioxide, carbon black, activated carbon, zeolites, ion exchange resins, polymeric substrates, metal substrates, an alkaline earth metal carbonate or the like or combinations thereof. The percentage concentration of the metal in the supported catalysts may be in the range of 0.1 to 50% by weight but is preferably in the range of 0.2 to 5% by weight.

[0081] The hydrogenation step can be carried out at a temperature of 20 to 120°C, and preferably 30 to 90°C.

[0082] Furthermore, such a step can be carried out at an absolute pressure of 100 to 1200 kPa, and preferably of 150 to about 600 kPa.

[0083] Preferably, the hydrogenation step can be carried out either in a suspension reactor or in a fixed bed reactor.

[0084] After the hydrogenation step, the working solution (now comprising F hydroquinone) is subjected to an oxidation step. During this step, hydroquinone is converted into quinone while hydrogen peroxide is produced. Such a step is carried out in the presence of oxygen. As an oxygen source, molecular oxygen, an oxygen-enriched gas, air, or any other suitable oxygen-containing compound capable of producing hydrogen peroxide and oxidizing hydroquinone can be used.

[0085] This step can be carried out, for example, in a bubble reactor, in which the oxygen source and the working solution can pass co-currently or counter-currently. The bubble reactor can be free of internal devices or preferably contain internal devices in the form of packing plates or sieves.

[0086] The oxidation step can be carried out at a temperature of 20 to 100°C, and preferably 40 to 75°C.

[0087] Furthermore, such a step can be carried out at an absolute pressure of 50 to 1500 kPa, and preferably of 100 to about 700 kPa.

[0088] The oxidation step is preferably carried out with an excess of oxygen, so that preferably more than 90%, in particular more than 95%, of the hydroquinone contained in the working solution is converted into the quinone form.

[0089] At the end of this step, the working solution may have a hydrogen peroxide concentration of 0.5 to 2.5% by weight and preferably 0.8 to 1.9% by weight. For example, the working solution may have a hydrogen peroxide concentration of 0.5 to 1% by weight; or 1 to 1.5% by weight; or 1.5 to 2% by weight; or 2 to 2.5% by weight.

[0090] After this step, the process according to the present invention may comprise a step of recovering hydrogen peroxide from a crude hydrogen peroxide solution. This step may be carried out by extracting the working solution resulting from the oxidation step with water. This step may be carried out in perforated tray extraction columns, packed columns, pulsed packed columns and liquid-liquid centrifugal extractors.

[0091] Extraction efficiency is strongly influenced by the distribution coefficient, which depends on the composition of the working solution (e.g., the type and concentration of solvents and the accumulation of degraded compounds). Efficient extraction can remove more than 95% of the hydrogen peroxide from the working solution.

[0092] At the end of this step, the crude hydrogen peroxide solution may have a hydrogen peroxide concentration of 25 to 55% by weight and preferably 30 to 50% by weight.

[0093] The solution resulting from the recovery of hydrogen peroxide (and comprising the organic solvent of formula (I) and quinone) can then be reused in the hydrogenation step. However, it is preferable, before reusing said solution in the hydrogenation step, to adjust its water content. Since the solubility of water in the working solution is temperature dependent, its moisture content can be adjusted by carrying out the extraction step at temperatures compatible with the extraction performance, separating the dispersed water, and then increasing the temperature of the working solution before it reaches the hydrogenation step. The working solution can also be dried using the exhaust gas (vented gas) from the oxidation step.Alternatively, the working solution leaving the extraction column may be initially stripped of entrained water in a water separator and then passed through an aqueous solution of potassium carbonate for drying.

[0094] The fact that the organic solvent according to the invention preferably has a water solubility equal to or less than 2000 mg / kg makes it possible to reduce the loss of organic solvent during extraction. In addition, such reduced water solubility for the organic solvent makes it possible to provide a crude hydrogen peroxide solution of higher purity.

[0095] On the one hand, after the extraction step, the crude hydrogen peroxide solution can be treated (washed) to remove impurities such as entrained droplets of working solution and dissolved organic matter. This treatment can include, for example, coalescence, liquid-liquid extraction, treatment with resins or any other treatment well known in the chemical industry. The purified crude product can then be fed into a distillation unit, where it can be further purified and concentrated to the usual commercial concentration (e.g. 50-70% by weight of hydrogen peroxide).

[0096] On the other hand, the working solution after the extraction step can be recycled to the hydrogenation step to continue the hydrogen peroxide production cycle. As degradation products are formed (from quinone / hydroquinone compounds and solvents), the working solution should preferably be treated / regenerated to avoid deterioration of process performance. Many methods have been suggested to purify the working solution and regenerate active quinone from quinone degradation products. For example, treatment with alkaline substances (aqueous sodium hydroxide or potassium hydroxide solution, calcium hydroxide, ammonia, or amines), treatment with sodium aluminum silicates, and extraction with active aluminum oxide.

[0097] The working solution should also preferably be washed (usually with slightly acidic water) before being returned to the process. Preferably, the process according to the invention is a process for producing hydrogen peroxide by the (AO) process comprising at least the two alternating steps of: hydrogenation of a working solution in the presence of one or more catalysts, said working solution comprising at least 2-ethylanthraquinone dissolved in at least one organic solvent, to obtain at least one corresponding hydroquinone; and oxidation of at least said hydroquinone; said organic solvent being a substituted or unsubstituted 5-membered ring lactone or a substituted or unsubstituted 6-membered ring lactone, preferably a lactone selected from the group consisting of γ-octalactone, δ-dodecalactone, and mixtures thereof.

[0098] Uses

[0099] The present invention further relates to the use of at least one organic solvent for dissolving a quinone in a working solution for the production of hydrogen peroxide, wherein the organic solvent is a lactone of formula (I) as described above.

[0100] In other words, the organic solvent as described above is used to dissolve a quinone in a working solution for the production of hydrogen peroxide.

[0101] Preferably, the present invention relates to the use of an organic solvent for dissolving a quinone in a working solution for the production of hydrogen peroxide, wherein the organic solvent is a lactone of formula (I) as described above.

[0102] In particular, the invention relates to the use of at least one organic solvent as described above to improve the solubility of a hydroquinone, preferably 2-ethyltetrahydroanthrahydroquinone.

[0103] Hydroquinone is notably formed after hydrogenation of the corresponding quinone.

[0104] The invention is illustrated in more detail in the following non-limiting examples. Examples

[0105] The following examples illustrate the invention without limiting it.

[0106] Solubility tests of quinones and hydroquinones in different solvents

[0107] In the following examples, the solubilities of 2-ethyltetrahydroanthrahydroquinone (2-THEAHQ) were tested in different solvents according to the protocols detailed below.

[0108] Solubility protocol of 2-ethyltetrahvdroanthrahvdroquinone

[0109] For 2-ethyltetrahydroanthrahydroquinone, solubilities were determined by dissolving a weighed amount of the parent quinone in the test solvent. After adding a Pd-based catalyst to the solution, the mixture was hydrogenated until hydrogen absorption ceased and then cooled until precipitation occurred.

[0110] Sample analysis was performed by liquid chromatography. Reference mixtures were prepared for calibration.

[0111] The solubility of 2-ethyltetrahydroanthrahydroquinone (2-THEAHQ) was measured in two lactones of formula (I) according to the invention, in two lactones outside the invention corresponding to the formula (C) C n H(2n-2)O, in which n represents an integer strictly less than 8, and in different solvents of the prior art.

[0112] In the solvents of the prior art, the solubility of 2-ethyl-tetrahydroanthrahydroquinone was measured, on the one hand, in accordance with the protocol indicated above and, on the other hand, as indicated in the Canadian patent CA573780 (07.04.1959).

[0113] [Table 1] [Table 2]

[0114] As a result, the solubilities of 2-ethyltetrahydroanthrahydroquinone (2-THEAHQ) are greater in a working solution comprising at least one organic solvent according to the invention (belonging to formula (I) according to the invention) than in a working solution comprising at least one organic solvent, belonging to the same class of compounds but not corresponding to formula (I) according to the invention, under the same conditions. In the same way, the solubilities of 2-ethyltetrahydroanthrahydroquinone (2-THEAHQ) are greater in a working solution comprising at least one organic solvent according to the invention (belonging to formula (I) according to the invention) than in a working solution comprising at least one organic solvent of different structure commonly used in the literature.

[0115] Table 3 below compares the different properties of an organic solvent according to the invention and lactones of formula (C) of which n is strictly less than 8 and solvents commonly used in the literature.

[0116] Flash point can be determined by a closed cup apparatus according to ASTM-D3278.

[0117] Vapor pressure can be determined by ebulliometry according to ASTM-E1719.

[0118] Specific gravity can be determined using a hydrometer in accordance with ASTM-D891.

[0119] Water solubility can be determined by Karl Eischer coulometric titration according to ASTM-D6304.

[0120] A low specific gravity (as low as possible) facilitates the separation of the solvent from the water. This is useful during the step of extracting hydrogen peroxide from the working solution.

[0121] Low water solubility of the solvent is considered a very important property in this application. It helps reduce solvent loss, especially during the extraction stage of the process (in which the oxidized working solution is treated with water to extract hydrogen peroxide). In addition, this decrease in the water solubility of the organic solvent allows for a crude hydrogen peroxide solution of higher purity.

[0122] [Table 3]

[0123] (*) outside the invention As shown in Table 3, the compounds according to the invention also have a number of other favorable properties making it possible to improve the optimization of the hydrogen peroxide production process.

Claims

CLAIMS 1. A process for producing hydrogen peroxide comprising at least the two alternating steps of: hydrogenation of a working solution in the presence of one or more catalysts, said working solution comprising at least one quinone dissolved in at least one organic solvent, to obtain at least one corresponding hydroquinone; and oxidation of said at least one hydroquinone; characterized in that the organic solvent is a lactone corresponding to the following formula (I): [Chem 4] CaH(2s!-2)O (I) in which n is an integer greater than or equal to 8.

2. Method according to claim 1, characterized in that n varies from 8 to 14, preferably from 9 to 13.

3. Method according to claim 1 or 2, characterized in that the organic solvent is a lactone with a 5-membered ring, substituted or not, or 6-membered ring, substituted or not, or 7-membered ring, substituted or not.

4. Method according to any one of the preceding claims, characterized in that the organic solvent has a flash point greater than or equal to 60°C, preferably greater than or equal to 62.5°C and even more preferably greater than or equal to 65°C.

5. Method according to any one of the preceding claims, characterized in that the organic solvent has a vapor pressure less than or equal to 450 Pa, more preferably less than or equal to 400 Pa, and even more preferably less than or equal to 350 Pa, measured at a temperature of 20°C.

6. Method according to any one of the preceding claims, characterized in that the organic solvent has a solubility in water less than or equal to 2000 mg / kg, preferably less than or equal to 1500 mg / kg, measured at a temperature of 25°C.

7. Method according to any one of the preceding claims, characterized in that the organic solvent has a specific density strictly less than 1, preferably less than or equal to 0.

97.

8. Method according to any one of the preceding claims, characterized in that the organic solvent is chosen from the group consisting of y-octalactone, 6-octalactone, y-nonalactone, 6-nonalactone, 3-methyl-y-octalactone, y-decalactone, 6-decalactone, s-decalactone, 4-methyl-y-nonalactone, 4-ethyl-y-octalactone, 4-methyl-7-isopropyl-s-heptalactone, y-undecalactone, 6-undecalactone, 3-methyl-y-decalactone, y-dodecalactone, 6-dodecalactone, s-dodecalactone, y-tridecalactone, 6-tridecalactone, y-tetradecalactone, 6-tetradecalactone, and their mixtures, preferably with y-octalactone and δ-dodecalactone and their mixtures.

9. Method according to any one of the preceding claims, characterized in that the organic solvent is δ-dodecalactone.

10. Method according to any one of the preceding claims, characterized in that the quinone is an anthraquinone, preferably an alkylanthraquinone and / or a tetrahydroalkylanthraquinone, preferably chosen from the group consisting of 2-ethylanthraquinone, 2-isoproylanthraquinone, 2-isopropylanthraquinone, 2-n-butylanthraquinone, 2-sec-butylanthraquinone, 2-tert-butylanthraquinone, 2-amylanthraquinine, 2-sec-amylanthraquinone, 2-tert-amylanthraquinone, and mixtures thereof.

11. Method according to any one of the preceding claims, characterized in that the working solution further comprises an additional solvent different from the organic solvent of formula (I), preferably chosen from the group consisting of polar organic solvents, non-polar hydrocarbon solvents, and mixtures thereof.

12. Method according to any one of the preceding claims, characterized in that the working solution consists of the organic solvent of formula (I) and quinone.

13. Use of at least one organic solvent for dissolving a quinone in a working solution for the production of hydrogen peroxide, in which the organic solvent is a lactone corresponding to the following formula (I): [Chem 5] CnHfSfl-S)^) (I) in which n is an integer greater than or equal to 8.

14. Use according to claim 13, characterized in that n varies from 8 to 14 and / or the organic solvent has a flash point greater than or equal to 60°C.

15. Use of at least one organic solvent of formula (I), as described according to any one of claims 1 to 9, to improve the solubility of a hydroquinone.

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