WO2024110260A1 - Novel synthesis for a nitrile solvent - Google Patents

Abstract

The present invention relates to a novel synthesis for a cyclohexane carbonitrile solvent, in particular for 1-cyano-1,3,3-trimethyl-cyclohexane, and its use as polar solvent in a hydrogen peroxide production process using alkylanthraquinones and/or their tetrahydro form.

Description

Novel Synthesis for a Nitrile Solvent

This application claims priority filed on November 25, 2022 in Europe with Nr 22209680.2.

TECHNICAL FIELD

The present invention relates to a novel synthesis for a cyclohexane carbonitrile solvent, in particular for l-cyano-l,3,3-trimethyl-cyclohexane, and its use as polar solvent in a hydrogen peroxide production process using alkylanthraquinones and/or their tetrahydro form.

TECHNICAL BACKGROUND

Hydrogen peroxide is one of the most important inorganic chemicals to be produced worldwide. Its industrial applications include textile, pulp and paper bleaching, organic synthesis (propylene oxide), the manufacture of inorganic chemicals and detergents, environmental and other applications.

Synthesis of hydrogen peroxide is predominantly achieved by using the Riedl-Pfleiderer process (originally disclosed in U.S. Pat. Nos. 2,158,525 and 2,215,883), also called anthraquinone loop process or AO (auto-oxidation) process.

This well-known cyclic process makes use typically of the auto-oxidation of at least one alkylanthrahydroquinone and/or of at least one tetrahydroalkylanthrahydroquinone, most often 2-alkylanthrahydroquinone, to the corresponding alkylanthraquinone and/or tetrahydroalkylanthraquinone, which results in the production of hydrogen peroxide.

The first step of the AO process is the reduction in an organic solvent (generally a mixture of solvents) of the chosen quinone (alkylanthraquinone or tetrahydroalkylanthraquinone) into the corresponding hydroquinone (alkylanthrahydroquinone or tetrahydroalkylanthrahydroquinone) using hydrogen gas from any source and a catalyst. The mixture of organic solvents, hydroquinone and quinone species (working solution, WS) is then separated from the catalyst and the hydroquinone is oxidized using oxygen, air or a mixture of oxygen with other gases thus regenerating the quinone with simultaneous formation of hydrogen peroxide. The organic solvent of choice is typically a mixture of two types of solvents, one being a good solvent of the quinone derivative (generally a non-polar solvent for instance a mixture of aromatic compounds) and the other being a good solvent of the hydroquinone derivative (generally a polar solvent for instance a long chain alcohol or an ester or a tetraalkylurea or a trialkylphosphate). Hydrogen peroxide is then typically extracted with water and recovered in the form of a crude aqueous hydrogen peroxide solution, and the working solution with quinone species is returned to the hydrogenator to complete the loop.

The use of for example di-isobutylcarbinol (DBC) as polar solvent is namely described in Patent applications EP 529723, EP 965562 and EP 3052439 in the name of the Applicant. The use of a commercial mixture of aromatics sold under the brand Solvesso®-150 (CAS no. 64742-94-5) as non-polar solvent is also described in said patent applications. This mixture of aromatics is also known as Caromax, Shellsol, Al 50, Hydrosol, Indusol, Solvantar, Solvarex and others, depending on the supplier. It can advantageously be used in combination with sextate (methyl cyclohexyl acetate) as polar solvent (see namely US Patent 3617219).

Most of the AO processes use either 2-amylanthraquinone (AQ), 2- butylanthraquinone (BQ) or 2-ethylanthraquinone (EQ). Especially in the case of EQ, the productivity of the working solution is limited by the lack of solubility of the reduced form of ETQ (ETQH). It is namely so that EQ is largely and relatively quickly transformed in ETQ (the corresponding tetrahydroalkylanthraquinone) in the process. Practically, that ETQ is hydrogenated in ETQH to provide H2O2 after oxidation. The quantity of EQH produced is marginal in regards of ETQH. It means that the productivity of the process is directly proportional to the amount of ETQH produced. The reasoning is the same for a process working with AQ or BQ instead of EQ.

The hydrogenated quinone solubility issue is known from prior art and some attempts were made to solve it. In WO 2019/179973 the Applicant of the present invention discloses the use of non-aromatic cyclic nitrile type solvents as polar solvents in an AO process, more specifically the use of cyclohexane carbonitriles substituted with 3 methyl groups, in which the nitrile function is protected from chemical degradation. In such a nitrile solvent the hydrogenated quinone shows an improved solubility. Although some molecules of this kind are known, their market availability is currently only very limited and anyway too small to satisfy the needs of an industrial AO process. One reason is that the known production methods for such nitrile solvents are mostly complex and energy intensive. Besides, they are often synthesized starting from expensive and/or non-environmentally friendly raw materials. For example, one of suitable cyclohexane carbonitriles solvent as described in WO 2019/179973 is 1-cyano- 1,3,3-trimethyl-cyclohexane (C10B), also called l-cyano-l,5,5-trimethyl- cyclohexane or 1,3,3-trimethyl-cyclohexane-carbonitrile. A synthesis for this solvent is inter aha described in the scientific publication of Dischino et al. (J. Labelled Cpd. Radiopharm. 42, 965-974, 1999). This production method includes the following steps:

-reacting di ethylaluminum cyanide with isophorone to yield isophorone nitrile (IPN);

-reducing the ketone group of IPN with sodium borohydride to give a mixture of diasteromers of 3-cyano-3,5,5-trimethylcyclohexanol;

-reacting this mixture with methanesulfonyl chloride;

-eliminating methanesulfonic acid to afford a mixture of the cyano-olefins; -hydrogenating the resulting olefins over 10% Pd/C in methanol to obtain Cl OB.

Hence, this method requires 5 method steps, and thus, in view of industrial applicability, it is too complex and energy intensive due to the need of several purification steps, the wide range of operating temperatures and the high amount of effluents during the production of the nitrile solvent. Moreover, the starting material di ethyl aluminum cyanide is highly flammable.

Another problem of AO-processes known in the prior art is the formation of the undesired epoxide 2-ethyl-5,6,7,8-tetrahydro-8a,10a-epoxy-9,10- anthraquinone (ETEQ) during the oxidation of ETQH to obtain hydrogen peroxide. ETEQ does not participate significantly in the formation of hydrogen peroxide and reduces the amount of active ETQ, and thus the yield of hydrogen peroxide. The reasoning is the same for a process working with ATQ or BTQ instead of ETQ.

Consequently, there was still the need to provide a polar nitrile solvent, and especially a production method therefore, which overcomes the disadvantages of the prior art, and through its use the productivity of the AO process can be improved. In particular, the aim of the invention was to provide a production method for l-cyano-l,3,3-trimethyl-cyclohexane (Cl OB), which is less complex and energy intensive, has a sufficient, or even improved yield of Cl OB from IPN, and thus provides a sufficient amount of Cl OB.

Furthermore, it is desired that by using the nitrile solvent as polar solvent in an AO process, the hydrogenated quinone of the working solution should show an improved solubility in comparison to polar solvents usually used in AO processes. Additionally, the nitrile solvent of the invention should facilitate the extraction of the produced hydrogen peroxide from the organic phase to the aqueous phase, and/or should minimize the formation rate of the epoxide 2- ethyl-5,6,7,8-tetrahydro-8a,10a-epoxy-9,10-anthraquinone (ETEQ), in order to produce a hydrogen peroxide solution in sufficient quantity and which has an improved purity level, e.g. having a low total organic carbon (TOC) content.

SUMMARY OF THE INVENTION

The present invention relates to a method for the preparation of 1-cyano- 1,3,3-trimethyl-cyclohexane (C10B) comprising the following steps: a) reduction of isophorone nitrile (IPN) with zinc in the presence of hydrogen chloride and at least one organic solvent to obtain a mixture of C10B, l-cyano-l,3,3-trimethyl-cyclohex-4-ene (also called l,5,5-trimethylcyclohex-3-ene-l-carbonitrile) and 1-cyano- l,3,3-trimethyl-cyclohex-5-ene (also called 1,5,5- trimethylcyclohex-2-ene-l -carbonitrile); and b) hydrogenation of the mixture obtained in method step (a) to convert at least a part of l-cyano-l,3,3-trimethyl-cyclohex-4-ene and l-cyano-l,3,3-trimethyl-cyclohex-5-ene present in the mixture into Cl OB.

Furthermore, the invention relates to the nitrile solvent Cl OB produced according to said method, and to the nitrile solvent Cl OB containing a low amount of l-cyano-l,3,3-trimethyl-cyclohex-4-ene and l-cyano-l,3,3-trimethyl- cyclohex-5-ene. It also relates to the use of these nitriles as polar solvent in a process for the production of hydrogen peroxide using alkylanthraquinones and/or tetrahydoalkylanthaquinone (AO process). The AO process for manufacturing an aqueous hydrogen peroxide solution according to the invention comprises the following steps:

- hydrogenating a working solution which comprises an alkylanthraquinone and/or a tetrahydroalkylantraquinone and a mixture of a non-polar organic solvent and a polar solvent

- oxidizing the hydrogenated working solution to produce hydrogen peroxide, and

- isolating the hydrogen peroxide, wherein the polar organic solvent is l-cyano-l,3,3-trimethyl-cyclohexane (Cl OB) produced by the method of the invention.

DETAILED DESCRIPTION OF THE INVENTION

Before the process of the invention and the use of the polar solvents, which are obtained by the process of the invention, in an AO process will be described in detail, it is to be understood that this invention is not limited to specific process conditions described herein, since such conditions may, of course, vary.

It is also to be understood that the terminology used herein is not intended to be limiting, since the scope of the present invention will be limited only by the appended claims.

As used herein, the singular forms "a", "an", and "the" include both singular and plural referents unless the context clearly dictates otherwise. By way of example, "a compound" means one compound or more than one compound.

The terms "containing", "contains" and "contained of as used herein are synonymous with "including", "includes" or " comprising", "comprises", and are inclusive or open-ended and do not exclude additional, non-recited members, elements or process steps. It will be appreciated that the terms “containing”, “contains”, "comprising", "comprises" and "comprised of' as used herein comprise the terms "consisting of', "consists" and "consists of.

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

As used herein, the term “average” refers to number average unless indicated otherwise.

As used herein, the terms “% by weight”, “wt.- %”, “weight percentage”, or “percentage by weight” are used interchangeably. The same applies to the terms “% by volume”, “vol.- %”, “vol. percentage”, or “percentage by volume”, or “% by mol”, “mol- %”, “mol percentage”, or “percentage by mol”.

The recitation of numerical ranges by endpoints includes all integer numbers and, where appropriate, fractions subsumed within that range (e.g. 1 to 5 can include 1, 2, 3, 4 when referring to, for example, a number of elements, and can also include 1.5, 2, 2.75 and 3.80, when referring to, for example, measurements). The recitation of end points also includes the end point values themselves (e.g. from 1.0 to 5.0 includes both 1.0 and 5.0). Any numerical range recited herein is intended to include all sub-ranges subsumed therein.

All references cited in the present specification are hereby incorporated by reference in their entirety. In particular, the teachings of all references herein specifically referred to are incorporated by reference.

Unless otherwise defined, all terms used in disclosing the invention, including technical and scientific terms, have the meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. By means of further guidance, term definitions are included to better appreciate the teaching of the present invention.

In the following passages, different alternatives, embodiments and variants of the invention are defined in more detail. Each alternative and embodiment so defined may be combined with any other alternative and embodiment, and this for each variant unless clearly indicated to the contrary or clearly incompatible when the value range of a same parameter is disjoined. In particular, any feature indicated as being preferred or advantageous may be combined with any other feature or features indicated as being preferred or advantageous.

Furthermore, the particular features, structures or characteristics described in present description may be combined in any suitable manner, as would be apparent to a person skilled in the art from this disclosure, in one or more embodiments. Furthermore, while some embodiments described herein include some but not other features included in other embodiments, combinations of features of different embodiments are meant to be within the scope of the invention, and from different embodiments, as would be understood by those in the art.

The invention relates to the nitrile solvent l-cyano-l,3,3-trimethyl- cyclohexane (C10B), also called l-cyano-l,5,5-trimethyl-cyclohexane or 1,3,3- trimethyl-cyclohexane-carbonitrile, which is a polar solvent and thus interesting for using it in an AO process. In particular, the invention provides a production method for Cl OB comprising two main method steps.

In a first step, method step (a), a reduction of isophorone nitrile (IPN) with zinc in the presence of hydrogen chloride and at least one organic solvent is carried out, known as Modified Clemmensen Reduction, to obtain a mixture of C10B, l-cyano-l,3,3-trimethyl-cyclohex-4-ene (C 10- Alkene- 1) and 1-cyano- l,3,3-trimethyl-cyclohex-5-ene (C10-Alkene-2) (see reaction scheme 1):

Afterwards, the second method step, method step (b), is conducted, wherein the two cyclo-alkenes, C 10- Alkene- 1 and C10-Alkene-2, obtained in method step (a) are hydrogenated to convert at least a part of C 10- Alkene- 1 and

C10-Alkene-2 present in the mixture into Cl OB (see reaction scheme 2):

Method steps (a) and (b) of the invention can be carried out in one and the same reactor or in different reactors. Preferably the method steps are carried out in different reactors.

The method of the invention is less complex and less energy intensive in comparison to production methods known in the prior art. Moreover, by using the method of the invention the transformation of IPN to Cl OB can be carried out at short reaction times, with a higher overall yield of Cl OB. Consequently, the method of invention is interesting for industrial processes.

In a preferred embodiment of the invention, the IPN used in method step (a) is produced in a previous method step by conjugate hydrocyanation of isophorone according to known methods. Suitable methods to conduct industrial conjugate hydrocyanation of isophorone to obtain IPN are described for example in EP 0502 707 Al or EP 0 554 786 Al. Every conjugate hydrocyanation method as known in the prior art and described for example by Wataru Nagata in Organic Reactions (1977, 255-476) can be used in this method step. However, it is preferred that the conjugate hydrocyanation is conducted by reacting isophorone with hydrogen cyanide in presence of a basic catalyst (in a solution, a dispersion or a solid) and in particular case, an ammonium or phosphonium salt or isophorone with alkali or alkaline earth metal cyanide alone or in combination with a phase transfer catalyst or an organic acid or an inorganic acid in one or a mixture of solvent suitable to solve at least partially the reactants. According to the invention, the Modified Clemmensen Reduction of method step (a) is carried out such that the conversion of IPN to the mixture of C10B, C10-Alkene-l and C10-Alkene-2 is preferably of at least 90 mol%, more preferably of at least 94 mol%, most preferably of at least 96 mol%.

The selectivity of the Modified Clemmensen Reduction of the invention to obtain Cl OB is at least 60 mol%, preferably at least 65 mol%, more preferably at least 68 mol%.

Method step (a) according to the invention may be carried out at a temperature between -15 and 30 °C, however, it is preferred to carry out method step (a) at a temperature between 0 and 30 °C, more preferably between 5 and 25 °C.

A particular advantage of the invention is that the Modified Clemmensen Reduction of method step (a) can be carried out at room temperature, i.e. at temperature between about 20 to 26 °C, more preferably between about 21 and 25 °C. Hence, it is not necessary to cool the reaction mixture and thus the energy consumption of method step (a) can be minimized.

In order to further improve the conversion and/or selectivity of method step (a) of the invention, it is preferred that zinc is used in an amount of from 1.5 to 8 eq., more preferred of from 2.0 to 7.0 eq., even more preferred of from 3.0 to 5.0 eq., related to 1 eq. IPN.

Furthermore, even though, according to the invention, zinc can be used in any physically form known in the art, it is preferred to use zinc in form of zinc powder, preferably having a mean particle size below 45 micrometers.

Furthermore, in method step (a), the zinc may be used in an activated or non-activated form; preferably the zinc used in method step (a) of the invention is an activated zinc. The activated zinc can be obtained by any method known in the prior art. Usually, the zinc activation is done by mixing zinc metal with an additive in a solvent. The additive may be for example 1,2-di bromomethane, trimethyl silyl chloride, bromine or iodine or a combination thereof, and the solvent may be an ether solvent, like tetrahydrofuran, cyclopentyl methyl ether, 2-methyltetrahydrofuran, tetrahydropyran, 4-methyltetrahydropyran, 1,4-di oxane or combinations thereof, or the additive in a solvent may be an aqueous hydrochloric acid solution. In another embodiment, the activation of zinc may be done firstly with aqueous solution of hydrogen chloride and secondly after post treatment (such as water washing and drying) with one of above method. Additionally, in order to carry out the Modified Clemmensen Reduction zinc has to be used in combination with hydrogen chloride. According to the invention, the hydrogen chloride is preferably used in an amount of from 5.0 to 15.0 eq., more preferably of from 8.0 to 12.5 eq., related to 1 eq. IPN.

It is further preferred that in method step (a) of the invention, an IPN concentration is used, which is below 60 g per liter, more preferably below 55 g per liter of the organic solvent including hydrogen chloride as used in method step (a); in particular IPN should be used in a concentration of between 35 to 50 g per liter of the organic solvent including hydrogen chloride as used in method step (a).

Moreover, method step (a) is carried out in the presence of at least an organic solvent, preferably in the presence of one or more inert solvents, which are suitable to solve the reactants. Preferably the solvent is selected from the group consisting of diethylether, tetrahydrofuran, cyclopentyl methyl ether (CPME), 2-methyltetrahydrofuran, tetrahydropyran, 4-methyltetrahydropyran, 1,4-di oxane, or combinations thereof.

By carrying out the Modified Clemmensen Reduction according to the invention, the conversion of IPN to the mixture of Cl 0B, C 10- Alkene- 1 and C10-Alkene-2 is nearly completed within 3 h, preferably within 2.5 h, more preferably within 2 h after addition of the total amount of zinc.

Afterwards, the obtained mixture can be filtered to separate the solid from the liquid phases. The reactor and the filter with the solid are preferably washed with organic solvent that is combined with the liquid organic phase. The combined organic phase is advantageously washed with water and/or acid or basic aqueous solution to remove interfering impurities. Any washing and/or extraction steps used in the method of the invention are intended to denote any treatment which is well known in the chemical industry and for example may be done in a mixer-settler or in a counter-current column. Subsequently, the aqueous phases may be further extracted with organic solvent and then purified. The entire organic phase may be further washed with water.

In a preferred embodiment of the invention, the Modified Clemmensen Reduction is conducted at room temperature with an IPN concentration of between 40g/L and 60 g/L in the presence of 3 to 5 eq. of zinc powder and 5.0 eq. to 8.5 eq. HC1, related to 1 eq. IPN. The solvent used in this embodiment is CPME. After carrying out step (a) and possible washing, drying and concentrating steps, resulting in an organic phase including Cl OB, C10-Alkene-l and C10- Alkene-2, method step (b) of the invention is conducted.

In method step (b) the cycloalkenes (C10-Alkene-l and C10-Alkene-2) obtained in method step (a) of the invention as undesired side products are hydrogenated to convert them at least partially to Cl OB. It is preferred that in method step (b) of the invention at least 90%, more preferred at least 95 %, even more preferred at least 99 %, most preferred at least 99.5% of the cycloalkenes (C 10- Alkene- 1 and C10-Alkene-2) present in the mixture obtained in method step (a) is converted to Cl OB. Even though it is preferred that all cycloalkenes present in the mixture obtained in method step (a) of the invention are converted into Cl OB, the mixture obtained in method step (b) of the invention may include C 10- Alkene- 1 and CIO Alkene-2 in a total amount of not more than 10 wt.-%, of not more than 5 wt.-%, of not more than 1 wt.-%, or of not more than 0.1 ppm based on the total weight of the mixture obtained in method step (b). Preferably, the mixture obtained in method step (b) may contain no more than 1 ppm, 5 ppm, 10 ppm or 50 ppm of the C10-Alkene-l and C10-Alkene-2, based on the total weight of Cl 0B. According to the invention, the mixture obtained in method step (b) may contain the C10-Alkene-l and C10-Alkene-2 in a total amount of at least 0.1 ppm and at most 10 wt.-%, based on the total weight of the mixture obtained in method step (b).

The invention is thus also related to a product containing mainly Cl 0B and a low amount of C 10- Alkene- 1 and CIO- Alkene-2. Usually, the total content of C 10- Alkene- 1 and CIO- Alkene-2 in this product is at least 0,1 ppm, at least 5 ppm, at least 10 ppm or at least 50 ppm. The content of C10-Alkene-l and C10- Alkene-2 is most often at most 10 wt.-%. Generally, the total content of C10- Alkene-1 and C10-Alkene-2 is at least 0,1 ppm and at most 10 wt.-%.

The hydrogenation can be carried out by any method known in the prior art. Preferably, the hydrogenation is carried out in the presence of a hydrogenation catalyst usually used in the prior art.

However, it is preferred that the catalyst is a heterogeneous catalyst comprising at least one element. Preferably, the catalyst comprises at least one element selected from the group consisting of elements of families 8, 9, 10, 11 and 12 of the IUPAC Periodic Table of The Elements. More preferably, the at least one element is selected from the group consisting of nickel, palladium, platinum, ruthenium and rhodium; even more preferred the at least one element is Pt The at least one element of catalyst may be supported or not on at least one carrier. Examples of non-supported catalyst are metal blacks like for example platinum black and palladium black, oxide catalysts as for example palladium oxide, platinum oxide, and ruthenium oxide and skeletal metals, like Raney® metals as Nickel Raney®.

If a supported catalyst is used, the carrier is usually selected from the group consisting of inorganic materials, organic materials and any combination thereof. Suitable inorganic materials are preferably selected form the group consisting of inorganic oxides, inorganic sulfates, inorganic hydrogenosulfates, inorganic carbonates, inorganic hydrogenocarbonates, and mixture thereof. Examples of inorganic oxides are kieselguhr, silica, aluminum oxides (aluminas), alkali metal and alkaline earth metal silicates, aluminum silicates (silica-aluminas), clays like montmorillonite and kaolin, zeolites like ZSM-5, spinels, magnesium silicates, magnesium oxide, zirconium oxide, sulfated or not, titanium oxide, tungsten oxide, zinc oxide, asbestos and mixed oxides like zirconia-silica or zirconia- tungsten oxide. Examples of inorganic carbonates are dolomite, barium carbonate and calcium carbonate. Barium sulfate is an example of inorganic sulfate. Suitable organic materials are preferably selected from the group consisting of active carbon, organic materials naturally occurring or organic synthetic compounds having high molecular weights, such as silk, polyamides, polystyrenes, cellulose or polyurethanes. Inorganic oxides, inorganic sulfates, inorganic carbonates, active carbons, and mixture thereof are preferred carriers. Active carbon is also convenient.

According to the invention, it is preferred to use a supported or nonsupported Pd or Pt-catalyst, in particular it is preferred to use an non-supported catalyst, preferably a Pt-catalyst, more preferably platinum(IV) oxide.

The hydrogenation is carried out under conditions usually used in the prior art. For example, the hydrogenation is conducted at a temperature of between 10 and 50 °C, more preferably between 20 and 30°C. Furthermore, the hydrogenation may be conducted at a pressure of from 1 to 10 bar, more preferably at Ito 5 bar. Hydrogen is typically fed into the reactor with a constant pressure, preferably during a period between 3.0 and 5.0 hours, more preferably between 3.5 and 4.5 hours, whereby the reaction period depends on the amount of the catalyst used therein, i.e. the lower the amount the longer the reaction period. Furthermore, it is preferred to carry out the hydrogenation in the presence of a solvent, more preferably in the presence of a solvent usually used in the prior art, for example selected preferably from the group consisting of an alcohol, an aliphatic hydrocarbon, a cyclic hydrocarbon, an aromatic hydrocarbon, an ether, a carboxylic acid, an linear or cyclic ester, a linear or cyclic amide, an alkyl phosphate, aN,N-dialkyl carbonamide, aN-alkyl carbonamide, aN-aryl carbonamide, aN,N-dialkyl carbamate, a tetraalkyl urea, a cycloalkyl urea, a phenylalkyl urea, a nitrile solvent, and a combination thereof. More preferably the solvent is selected from the group consisting of alcohols from 1 to 12 carbon atoms, ethylene glycol, propylene glycol, glycerol, alkanes from 5 to 12 carbons atoms, benzene, monoalkyl-benzene e.g. toluene, polyalkyl-benzene e.g. as one of isomers of xylene, trimethylbenzene, tetramethylbenzene, aromatic hydrocarbon solvent of type 150 from the Solvesso® series (or equivalent from other supplier), cyclopentyl methylether, tetrahydrofuran, 2-methyltetrahydrofuran, tetrahydropyran, 4- methyltetrahydropyran, 1,4-di oxane, acetic acid, alkylacetate with alkyl chain from 1 to 12 carbon atoms, alkylcyclohexanol esters, dimethylformamide, dimethylacetamide, N-methyl-2-pyrrolidone, alkyl phosphate, tetraalkyl urea, acetonitrile, propionitrile.

In particular, it is preferred to carry out the hydrogenation in the presence of acetic acid.

In step b) of the invention, the reaction mixture is preferably maintained under constant pressure of hydrogen and under stirring, for example during a period from 2 to 8 hours, more preferably from 3 to 5 hours.

Subsequently, the hydrogenation catalyst is commonly separated from the reaction mixture by filtration. The filter with the solid and the reactor may be washed, preferably with acetic acid that is combined with the filtrate.

The filtrate obtained by separating the hydrogenation catalyst from the reaction mixtures may be further diluted with an organic solvent and then washed with water and subsequently concentrated under reduced pressure to obtain Cl OB, preferably in a yield of between 80 and 98%, more preferably in a yield of between 87 and 97 %, even more preferably in a yield of between 89 and 95%.

The method of the invention may be carried out in a batch mode, as described above, or in a continuous mode.

Furthermore, the present invention relates to a process for manufacturing an aqueous hydrogen peroxide solution by using l-cyano-l,3,3-trimethyl- cyclohexane (Cl OB) obtained by the method of the invention. This process comprises the following steps: hydrogenating a working solution which comprises an alkylanthraquinone and/or a tetrahydroalkylanthraquinone and a mixture of a non-polar organic solvent and a polar organic solvent; oxidizing the hydrogenated working solution to produce hydrogen peroxide; and isolating the hydrogen peroxide, wherein the polar organic solvent is Cl OB obtained by the method of the invention as described above, or Cl OB containing C10-Alkene-l and C10- Alkene-2 in a total amount of at least 0,1 ppm and at most 10 wt.-%.

Hence, the production process for hydrogen peroxide according to the invention is an AO process. In the AO process of the invention, which preferably is a continuous process operated in loop, a working solution is used which is hence preferably circulated in a loop through the hydrogenation, oxidation and extraction steps.

The term "alkylanthraquinone" is intended to denote a 9,10-anthraquinone substituted in position 1, 2 or 3 with at least one alkyl side chain of linear or branched aliphatic type comprising at least one carbon atom. Usually, these alkyl chains comprise less than 9 carbon atoms and, preferably, less than 6 carbon atoms. Examples of such alkylanthraquinones are ethylanthraquinones like 2- ethylanthraquinone (EQ), 2-isopropylanthraquinone, 2-sec- and 2-tert- butylanthraquinone (BQ), 1,3-, 2,3-, 1,4- and 2,7-dimethylanthraquinone, amylanthraquinones (AQ) like 2-sec-iso- and 2-tert-amylanthraquinone and mixtures of these quinones.

The term "tetrahydroalkylanthraquinone" is intended to denote the tetrahydro-9, 10-anthraquinones corresponding to the 9, 10-alkylanthraquinones specified above. Hence, for EQ and AQ, they are respectively designated by ETQ and ATQ, their reduced forms (tetrahydroalkylanthrahydroquinones) being respectively ETQH and ATQH.

Preferably, an AQ or EQ or a mixture of both is used.

In order to be able to also solubilize the quinone, the polarity of the solvent mixture is preferably not too high. Hence, there is preferably at least 30wt% of non-polar solvent in the organic solvent mixture, and more preferably at least 40 wt. -%. Generally, there is not more than 80 wt.-% of this non-polar solvent, in the organic solvent mixture. The non-polar solvent preferably is an aromatic solvent or a mixture of aromatic solvents. Aromatic solvents are for instance selected from benzene, toluene, xylene, tert-butylbenzene, trimethylbenzene, tetramethylbenzene, naphthalene, methylnaphthalene mixtures of polyalkylated benzenes, and mixtures thereof. The commercially available aromatic hydrocarbon solvent of type 150 from the Solvesso® series (or equivalent from other supplier) gives good results. S-150 (Solvesso®-! 50; CAS no. 64742-94-5) is known as an aromatic solvent of high aromatics which offer high solvency and controlled evaporation characteristics that make them excellent for use in many industrial applications and in particular as process fluids. The Solvesso® aromatic hydrocarbons are available in three boiling ranges with varying volatility, e.g. with a distillation range of 165-181 °C, of 182-207 °C or 232-295 °C. They may be obtained also naphthalene reduced or as ultra-low naphthalene grades. Solvesso® 150 (S-150) is characterized as follows: distillation range of 182-207 °C; flash point of 64 °C; aromatic content of greater than 99 % by wt; aniline point of 15 °C; density of 0.900 at 15 °C; and an evaporation rate (n-butyl acetate = 100) of 5.3.

The hydrogenation reaction takes place in the presence of a catalyst (like for instance the one object of WO 2015/049327 in the name of the Applicant) and as for instance described in WO 2010/139728 also in the name of the applicant (the content of both references being incorporated by reference in the present application). Typically, the hydrogenation is conducted at a temperature of at least 45 °C and preferably up to 120 °C, more preferably up to 95 °C or even up to 80 °C only. Also typically, the hydrogenation is conducted at a pressure of from 0.2 to 5 bar. Hydrogen is typically fed into the vessel at a rate of from 650 to 750 normal m³ per ton of hydrogen peroxide to be produced.

The oxidation step may take place in a conventional manner as known for the AO process. Typical oxidation reactors known for the anthraquinone cyclic process can be used for the oxidation. Bubble reactors, through which the oxy gen-containing gas and the working solution are passed co-currently or counter-currently, are frequently used. The bubble reactors can be free from internal devices or preferably contain internal devices in the form of packing or sieve plates. Oxidation can be performed at a temperature in the range from 30 to 70 °C, particularly at 40 to 60 °C. Oxidation is normally performed with an excess of oxygen, so that preferably over 90%, particularly over 95%, of the alkyl anthrahydroquinones contained in the working solution in hydroquinone form are converted to the quinone form.

After the oxidation, during the purification step, the hydrogen peroxide formed is separated from the working solution generally by means of an extraction step, for example using water, the hydrogen peroxide being recovered in the form of a crude aqueous hydrogen peroxide solution. The working solution leaving the extraction step is then recycled into the hydrogenation step in order to recommence the hydrogen peroxide production cycle, eventually after having been treated/regenerated.

In a preferred embodiment, after its extraction, the crude aqueous hydrogen peroxide solution is washed several times i.e. at least two times consecutively or even more times as required to reduce the content of impurities at a desired level, for example, the crude aqueous hydrogen peroxide solution is washed with an organic solvent, which is intended to reduce the content of impurities in the aqueous hydrogen peroxide solution as disclosed for example in GB 841323 A. This washing can consist, for example, in extracting impurities in the crude aqueous hydrogen peroxide solution by means of an organic solvent in apparatuses such as centrifugal extractors or liquid/liquid extraction columns, for example, operating counter-current wise. Liquid/liquid extraction columns are preferred. Among the liquid/liquid extraction columns, columns with random or structured packing (like Pall rings for instance) or perforated plates are preferred. The formers are especially preferred.

In a preferred embodiment, a chelating agent can be added to the washing solvent in order to reduce the content of given metals. For instance, an organophosphorus chelating agent can be added to the organic solvent as described in the above captioned patent application EP 3052439 in the name of the Applicant, the content of which is incorporated by reference in the present application.

The expression "crude aqueous hydrogen peroxide solution" is intended to denote the solutions obtained directly from a hydrogen peroxide synthesis step or from a hydrogen peroxide extraction step or from a storage unit. The crude aqueous hydrogen peroxide solution can have undergone one or more treatments to separate out impurities prior to the washing operation according to the process of the invention. It typically has a H2O2 concentration within the range of 30- 50% by weight. By using Cl OB produced according to the invention, it is possible to achieve a higher solubility of the hydrogenated quinone of the working solution, in particular in comparison to sextate and di-isobutylcarbinol (DBC), which are usually used as polar solvents in an AO process. The maximum solubility of a hydrogenated quinone (QH) in a solvent mixture is directly correlated with the productivity of the working solution. The higher is QH solubility, the higher will be theoretically quantity of hydrogen peroxide achievable per kg of WS (productivity).

The degree of QH solubility can be indicated as test level (TL), which refers to the produced amount of H2O2 per kg working solution (g H2O2/kg of WS) at a specific temperature for a specific concentration of the polar solvent. According to the invention, it is preferred that at 70 °C and a polar solvent concentration in the working solution of 15 wt.-% the test level (TL) is above 5.9, preferably above 6.0 g H2O2/kg WS. Additionally, it is preferred that at 70 °C and a polar solvent concentration in the working solution of 25 wt.-% the test level (TL) is 9.0 or higher, more preferably 9.5 or higher. This is fulfilled by using Cl 0B produced by the method of invention as polar solvent in the AO process.

Due to the higher solubility obtained by using Cl 0B produced according to the invention, less amounts of the polar solvent is needed to achieve a higher partition coefficient, called kb ratio, at same QH solubility. With this higher partition coefficient, called kb ratio, it is possible to reduce the capex (capital expenditure) required for the extraction sector.

The use of Cl 0B according to the invention as polar solvent in the AO process results into a better extraction of hydrogen peroxide from the organic phase to the aqueous phase in comparison to an AO process, wherein as polar solvent for example sextate or DBC is used. Indeed, hydrogen peroxide concentration in organic phase is lower when using Cl 0B instead of the two other solvents. This effect can be indicated for example by the kb ratio of the solvent. The determination of the kb ratio according to the invention is described below in the examples. The kb ratio of the Cl 0B produced according to the invention is higher than of sextate or DBC. In particular, it is preferred that at a concentration of 30 wt.-% of the polar solvent in the mixture of non-polar solvent and polar solvent, the kb ratio of Cl 0B according to the invention is at least 300, at least 450, or at least 500. Furthermore, as mentioned above, it is state of the art that the epoxide 2- ethyl-5,6,7,8-tetrahydro-8a,10a-epoxy-9,10-anthraquinone (ETEQ) is an undesired by-product in the AO process obtained during the oxidation of 2-ethyl- 5,6,7, 8-tetrahydro-9,10-anthrahydroquinone. Consequently, it is desired to minimize its formation rate. As demonstrated in the examples, by using Cl OB of the invention instead of for example DBC the ETEQ formation rate can be minimized. According to the invention it is preferred that the epoxide formation rate (g ETEQ/kg of total H2O2 produced) is less than 4.0, more preferably less than 3.8 or lower.

It has been further found out that due to the use of the Cl OB produced according to the invention, the TOC content in aqueous hydrogen peroxide is lower than the TOC content of an aqueous hydrogen peroxide by using sextate or DBC as polar solvents. In particular the TOC content of the aqueous hydrogen peroxide solution by using the Cl OB of the invention as polar solvent is lower than 400 ppm, in particular lower than 350 ppm, or even lower than 300 ppm, for instance lower than 280 ppm, lower than 250 ppm, or lower than 230 ppm measured in a test mimicking the final stage of the water extraction of hydrogen peroxide from oxidized working solution of an AO process and described in the examples below.

Hence, a higher purity level of the hydrogen peroxide solution can be obtained.

The Cl 0B according to the invention is suitable for the manufacture of hydrogen peroxide by the AO process wherein said process has a production capacity of hydrogen peroxide of up to 300 or 100 kilo tons per year (ktpa), i.e. the solvents are suitable for large scale AO-processes. Furthermore, the solvents are also suitable for small to medium scale AO-processes operating with a production capacity of hydrogen peroxide of up to 50 kilo tons per year (ktpa), and more preferably with a production capacity of hydrogen peroxide of up to 35 kilo tons per year (ktpa), and in particular with a production capacity of hydrogen peroxide of up to 20 kilo tons per year (ktpa). The dimension ktpa (kilo tons per annum) relates to metric tons.

A particular advantage of such scales AO process is that the hydrogen peroxide can be manufactured in a plant that may be located at any, even remote, industrial end user site and the solvents of the invention are therefore especially suitable. It is namely so that since the QH solubility and the partition coefficient , called kb ratio, is more favourable with less amount of polar solvent, less emulsion is observed in the process and a purer H2O2 solution can be obtained (namely containing less TOC) and this for a longer period of time compared to when solvents known from prior art are used.

In a preferred sub-embodiment of the invention, the working solution is regenerated either continuously or intermittently, based on the results of a quality control, regeneration meaning conversion of certain degradants, like epoxy or anthrone derivatives, back into useful quinones. Here also, the Cl OB according to the invention is favourable because the amount of epoxide to be regenerated is reduced, the quality of the H2O2 solution can be maintained within the specifications namely in terms of TOC as mentioned above for a longer period of time.

The present invention is further illustrated by the following examples. It should be understood that the following examples are for illustration purposes only, and are not used to limit the present invention thereto.

EXAMPLES

Abbreviations

AO: autooxidation

DBC: di-isobutylcarbinol

C 1 OB : 1 -cyano- 1 ,3, 3-trimethy 1-cy clohexane

IP: Isophorone

IPN : Isophorone nitrile

DCM: Dichloromethane

MTBE: tert. -butyl methyl ether

ETQ: 2-ethyl-5,6,7,8-tetrahydro-9,10-anthraquinone

ETEQ: 2-ethyl-5,6,7,8-tetrahydro-8a,10a-epoxy-9,10-anthraquinone

CPME: Cyclopentyl methyl ether

GC: Gas chromatography

NMR: Nuclear magnetic resonance

OP: organic phase r.t: room temperature

TOC: total organic carbon

WS: working solution Production of C10B (according to the invention)

First Method Step (a)

In a 10L double jacketed reactor equipped with mechanical stirring, a nitrogen inlet, a temperature probe and a condenser connected to a scrubber flask filled with an aqueous NaOH solution (5L, 2N), was dissolved IPN (197.3 g, 1.2 mol, 1.0 equiv.) in a solution of hydrogen chloride in Diethyl Ether (4800 mL, 2N, 9.6 mol, 8.0 eq) set at 20°C. The IPN was produced by hydro-cyanation of IP as known in the art. Non-activated zinc powder (392.8 g, 6.0 mol, 5.0 equiv.) was added to this solution portionwise to control the exothermic of the addition and remain as close as possible to the set temperature. The mixture was then allowed to come back to room temperature under stirring for 2 hours. The crude mixture was filtered through a plug of Celite and the reactor was washed twice with 4L of methyl tert. -butyl ether (MTBE). The filter containing the wet solid was washed with organic phase from reactor rinsing. The organic phases were combined and washed successively with 5L of HC1 (5%), twice with 5L of demineralized water and once with 5L of saturated NaCl solution (26% w/w). The aqueous phases were combined and extracted with 4L MTBE. All the organic phases were combined, evaporated until obtaining 10% of the initial volume and dried over magnesium sulfate and concentrated under vacuum to yield 174.9 g of a pale orange-reddish translucent oil that was analysed by gas chromatography (GC) with a flame ionisation detector (FID) to quantify IPN and Cl 0B. The performance of reaction calculated as described in the next section “Optimization of reaction between IPN and zinc (method step (a))” was: conversion IPN = 96 mol.-%, selectivity C10B = 73 mol.-%, yield C10B = 70 %. The distillation (92°C, 100 mbar) of crude mixture affords a translucent oil containing a mixture of C10B, l-cyano-l,3,3-trimethyl-cyclohex-4-ene and 1- cyano-l,3,3-trimethyl-cyclohex-5-ene.

Second Method Step (b)

In a 1.2L double jacketed reactor equipped with mechanical stirring, a nitrogen inlet, a temperature probe and a hydrogen tank, were dissolved a mixture containing l-cyano-l,3,3-trimethyl-cyclohex-4-ene (3.9 g, 0.0262 mol), l-cyano-l,3,3-trimethyl-cyclohex-5-ene (35.1 g, 0.236 mol) and C10B (205.0 g, 1.36 mol) in acetic acid (1000 mL). To this solution flushed with nitrogen for 5 minutes and without stirring was added platinum (IV) oxide (1.0 g, 0.0045 mol, 0.02 equiv. vs 1.0 eq. of total alkene, i.e. the sum of l-cyano-1,3,3 - trimethyl- cyclohex-4-ene and l-cyano-l,3,3-trimethyl-cyclohex-5-ene (altogether 39.0 g, 0.262 mol, 1.00 equiv.)). The reactor was then flushed four times with about 1.1 bar of hydrogen flowing close to the surface of the solvent to replace the lighter nitrogen. Afterwards, the reactor was put under a constant pressure of about 1.1 bar of hydrogen under vigorous stirring (1200 rpm) at room temperature. After 4h the required volume of hydrogen (0.53 g, 5.9 L, 262 mmol, 1.0 equiv.) was consumed. The catalyst was filtered off using a membrane and quenched directly by soaking it into water, the membrane and the reactor were rinsed with 100 mL and 500 mL AcOH respectively. The acid organic phase was poured into 2.5L of demineralized water and the aqueous phase was extracted four times with 500 mL of DCM. Then the organic phase was washed four times with 500 mL of demineralized water, once with 500 mL of IN NaOH aqueous solution and finally once with 500 mL of NaCl solution (20% w/w). Consequently, the organic phase was then dried over magnesium sulfate and concentrated under vacuum to yield a brownish translucent oil (C10B content: 225.3 g, 1.5 mol, 92%). Crude distillation yields C10B as a translucent oil (208.8 g, 1.4 mol, isolated yield 86%).

Optimization of reaction between IPN and zinc (method step (a))

Except IPN, all reactants were commercially available. This optimization study was performed as described in previous procedure of method step (a) with a smaller reactor, non-activated or activated zinc powder, which depends on the test, IPN and solution of hydrogen chloride in diethyl ether (2N) or in cyclopentylmethylether (3N or 4N). When the mixture was allowed to come back to room temperature under stirring for 2 hours, a similar work-up was applied to afford after final concentration with a rotary evaporator under vacuum the crude mixture that was analysed by gas chromatography (GC) with a flame ionization detector (FID) to quantify IPN and Cl 0B.

The conversion of IPN, the selectivity and the yield of Cl 0B obtained in this study were calculated as follows:

• Conversion:

100 X (number of mole of IPN introduced — number of mole of IPN recovered at the end of reaction) number of mole of IPN introduced

Selectivity: 100 X (number of mole of C10B recovered at the end of reaction) number of mole of IPN introduced — number of mole of IPN recovered at the end of reaction

• Yield'.

(selectivity of C10B) X (conversion of IPN) 100

The effect of temperature! °zinc amount, reaction time, physical form of zinc, zinc activation and IPN concentration on conversion, selectivity and yield of method step (a) was determined in the following manner:

• Determination of the effect of temperature:

A diethylether solution containing HC1 and IPN was regulated at several temperatures (T). Non-activated zinc powder was added portionwise to that solution to control the exotherm and avoid an increase of temperature of maximum 10°C. After zinc addition, the mixture was let to come back at room temperature for 2h.

The conditions used therein are: 1) IPN (1 eq, 40 g/L), Zn powder (7.9 eq, non-activated), HC1 (8.2 eq), Et20, T; 2) T till r.t, 2h.

• Determination of the effect of zinc amount:

A diethylether solution containing HC1 and IPN was regulated at 25°C and treated with several total amount of non-activated zinc powder. In each case, zinc was added portionwise to that solution to control the exotherm and avoid an increase of temperature of maximum 10°C. After zinc addition, the mixture was let to come back at room temperature for 2h.

The conditions used therein are: IPN (1 eq, 40 g/L), Zn powder (x eq, nonactivated), HC1 (8.2 eq), Et20, 25°C, 2h (after Zn addition).

• Determination of the effect of time after zinc addition:

A diethylether solution containing HC1 and IPN was regulated at 25°C. Non-activated zinc powder was added portionwise to that solution to control the exotherm and avoid an increase of temperature of maximum 10°C. After zinc addition, the mixture was let to come back at room temperature for 2h. In that particular study, this temperature was then maintained for several hours. During the course of that period, liquid samples was taken periodically and analysed by GC-FID to evaluate the conversion with time progress. The conditions used therein are: IPN (1 eq, 40 g/L), Zn powder (5 eq, nonactivated), HC1 (8.2 eq), Et20, 25°C, time (after the 2h)

• Determination of the effect of zinc physical form:

A diethylether solution containing HC1 and IPN was regulated at 25°C and treated with two forms of non-activated zinc. In each case, zinc was added portionwise to that solution to control the exotherm and avoid an increase of temperature of maximum 10°C. After zinc addition, the mixture was let to come back at room temperature for 2h.

The conditions used therein are: IPN (1 eq, 40 g/L), Zn form (5 eq, nonactivated), HC1 (8.2 eq), Et20, 25°C, 2h (after Zn addition).

• Determination of the effect of zinc activation:

A diethylether solution containing HC1 and IPN was regulated at 25°C and treated with a non-activated zinc powder or an activated one. In each case, zinc was added portionwise to that solution to control the exotherm and avoid an increase of temperature of maximum 10°C. After zinc addition, the mixture was let to come back at room temperature for 2h.

The zinc activation was done by mixing metal with aqueous hydrochloric acid solution (2 wt.-%) under vigorous stirring. The subsequent steps were realized as described in Organic Synthesis, coll. vol. 6, p. 289; vol. 53, p. 86 (1973).

The conditions used therein are: IPN (1 eq, 40 g/L), Zn powder (x eq, Activated or not), HC1 (8.2 eq), Et20, 25°C, 2h (after Zn addition).

• Determination of the effect of IPN concentration:

Ether solutions containing HC1 and several IPN concentrations were regulated at 25 °C and treated with a non-activated zinc powder. Zinc was added portionwise to that solution to control the exotherm and avoid an increase of temperature of maximum 10°C. After zinc addition, the mixtures were let to come back at room temperature for 2h.

The conditions 1 used therein are: IPN (1 eq., x g/L), Zn powder (5 eq., not activated), HC1 (8,2 eq.), Et20, 25°C, 2h (after Zn addition)

The conditions 2 used therein are: IPN (1 eq., x g/L), Zn powder (5 eq., not activated), HC1 (12,4 eq.), CPME, 25°C, 2h (after Zn addition)

Determination of the effect of type of solvent used in method step (b) The hydrogenation according to method step (b) was done with hydrogen (atmospheric pressure) in presence of PtCh at room temperature by using ethyl acetate or acetic acid as solvent.

AO Process

AO Process

The AO process was carried out in a lab pilot. Therefore, the pilot was composed of a hydrogenation reactor with a slurry of palladium catalyst, an oxidation column and an extraction column. It was run with a closed loop of organic working solution composed initially by a mixture of alkylated anthraquinone (ethyl anthraquinone and ethyltetrahydroanthraquinone), Solvesso™ 150 and as polar solvent C10B, sextate or DBC. It was monitored periodically to evaluate the formation of the epoxide ETEQ with the total production of hydrogen peroxide.

Determination of QH solubility in working solutions

The determination of the QH solubility was performed on synthetic

EQ/ETQ working solutions. These quinones mixed in the tested solvents have been hydrogenated to a fixed level and cooled down successively to 4 different temperatures before the measurements (min 3 hours to stabilize the system between each measurement). The conditions applied for these tests were

EQ concentration 100g/kg

ETQ concentration 140 g/kg

Polar solvent variable (*)

Level of hydrogenation 10.8 NI H₂/kg WS (~ 116g of QH/kg of WS or a TL (Test Level) of 16.3g of H2O2/kg WS (= maximum theoretical value of TL if all QH is dissolved)

Temperature of hydrogenation 75 °C

The temperature of precipitation is indicated as temperature at which QH was measured. The QH solubility have been determined at 70 °C, 65, 60 and 55 °C. The theoretical values designated by the term “Test Level g LhC /kg WS) ” were calculated as follows:

1 mole (240g) ETQH (which actually is QH in the examples) per kg of WS will produce 1 mole (34g) of H2O2 per kg of WS. Hence, the level in the examples equals: 34*QH/240.

Estimation of kb ratio from equilibration between aqueous hydrogen peroxide and organic solutions

An aqueous hydrogen peroxide solution (25 ml, 35 wt-%) and an organic solution (25 ml) prepared from Solvesso™ 150 and polar solvent were stirred together in a flask for 30 minutes. After decantation and separation of phases by centrifugation, the hydrogen peroxide content was determined in organic phase using suitable analytical method and expressed in g per kg of phase. The hydrogen peroxide concentration in aqueous phase is equal before and after equilibration.

The water concentration in aqueous phase (AP) and the total solvent concentration in organic phase (OP) both expressed in g per kg of phase were calculated by following formulas:

|H₂O|^A1> = 1000

[Total solvent] ^op = 1000 - [H2O2]^op

The kb ratio was calculated as: kb = { [H₂O₂]^AP / [H₂O]^AP J / { [H₂O₂]^OP / [Total solvent]^op }

Formation rate of ETEQ

The epoxide formation rate observed in AO process lab pilot was determined by measuring periodically (minimum 5 consecutive measurements spaced out in time at regular intervals) the concentration of ETEQ and hydrogen peroxide in the working solution after oxidation. The concentration of ETEQ and H2O2 were measured respectively by high performance liquid chromatography and spectrophotometry using potassium titanium (IV) oxalate. The concentrations of these species were expressed in g of species per kg of working solution.

The total amount of H2O2 produced after one specified time (M^l) was obtained by following formula and expressed in kg :

M^t= F * ([H202]/1000) * At + M^t where F is the flow of working solution in kg per hour, [H2O2] is the concentration of H2O2 in working solution in g per kg, At is the elapsed time (expressed in hour) between time t and the time t-1 of the previous measurement and M^t-1 is the total amount of H2O2 expressed in kg and produced at previous measurement at time t-1.

The total amount of H2O2 produced per kg of working solution after one specified time (M) is calculated by following formula and expressed in kg of total H2O2 produced per kg of working solution :

M = M^t/ m^ws where m^ws is the mass of working solution expressed in kg.

It was observed that the relationship between the ETEQ concentrations ([ETEQ]) and the total amounts of H2O2 (M) was linear with a slope corresponding to the epoxide formation rate expressed in g of ETEQ per kg of total H2O2 produced.

Determination of TOC content

The TOC content was measured in a test by mimicking the final stage of the water extraction of hydrogen peroxide from oxidized working solution of the AO process.

Therefore, a 50 ml penicillin flask equipped with a magnetic stir bar was charged with 20 g of aqueous hydrogen peroxide solution (45 wt.-%), 5 g of Solvesso™ 150 and 5 g of polar solvent. The resulting mixture was stirred for 10 minutes at 650 rpm and 60°C in the closed flask. The mixture was decanted at room temperature for 30 minutes. The tubing of the total organic carbon (TOC) analyser was introduced in the aqueous phase. The total carbon (TC) measurement was repeated three times and is equal to the TOC.

Results

1. Optimization of reaction between IPN and zinc

• Effect of temperature:

Table 1

As can be seen from Table 1, the optimum in terms of conversion and selectivity is between 5 and 25°C.

• Effect of zinc amount:

Table 2

Based on the results of Table 2, it can be seen that optimum amount of Zn is above 3 eq.

• Effect of time after zinc addition:

Table 3

The conversion is already reached after 2h (see Table 3).

• Effect of zinc physical form:

Table 4

Based on the results of Table 4, it can be observed that performance is better with zinc powder due to higher conversion without deterioration of selectivity.

• Effect of catalyst activation'.

Table 5

Based on the results of Table 5, it can been observed a selectivity gain with activation.

• Effect of IPN concentration:

Table 6

Based on the results of Table 6, it can be observed that yield is better below 60 g/L. Best result is obtained in CPME but not comparative with Et20. 2. Effect of type of solvent used in method step (b)

Table 7

As can be seen from the results of Table 7, acetic acid instead of ethylacetate should be used in the hydrogenation reaction (method step (b).

3. QH solubility

In Figures 1-4 the QH solubilities by using Cl OB, sextate or DBC as polar solvent in the AO process at a temperature of 70 °C, 65 °C, 60 °C and 55 °C are depicted.

Based on curve it can be observed that at 70°C, the test level is higher with Cl 0B than DBC and sextate, in particular, at a polar solvent concentration of 25 wt.-% the TL of C10B is above 9.0 g H2O2 / kg WS.

At temperatures below 70 °C the test level is higher with Cl 0B than DBC and sextate above a polar solvent concentration of 30 wt.-%. 4. Kb ratio

In Table 8 and in Figure 5 the kb ratio by using C10B, sextate or DBC as polar solvent in the AO process are depicted.

As can be seen from the graph, the kb ratio is higher when using Cl OB instead of sextate and DBC. It means that the extraction of hydrogen peroxide from organic phase to aqueous phase is better with Cl OB. Indeed, hydrogen peroxide concentration in organic phase is lower when using Cl OB instead of the two other solvents.

Table 8

5. Formation rate of ETEO

Table 9

As can be seen from Table 9, C10B is better than DBC and slightly less good than sextate. 6. TOC measurement

Table 10

Based on the results of Table 10, it can be observed that the TOC value in aqueous hydrogen peroxide is lower with the nitrile solvent Cl OB than with the sextate or DBC which means that Cl OB is less soluble in aqueous hydrogen peroxide and hence allows reaching a higher purity level of hydrogen peroxide solution.

Claims

C L A I M S

1. A method for the preparation of 1 -cyano-1.3.3-trimethy I -cyclohexane (Cl OB) comprising the following steps: a) reduction of isophorone nitrile (IPN) with zinc in the presence of hydrogen chloride and at least one organic solvent to obtain a mixture of C10B, 1 -cyano-1, 3, 3-trimethyl-cyclohex-4-ene and 1- cyano-l,3,3-trimethyl-cyclohex-5-ene; and b) hydrogenation of the mixture obtained in method step (a) to convert at least a part of l-cyano-l,3,3-trimethyl-cyclohex-4-ene and l-cyano-l,3,3-trimethyl-cyclohex-5-ene present in the mixture into Cl OB.

2. The method according to claim 1, wherein in a previous method step the IPN used in method step (a) is produced by a conjugate hydrocyanation of isophorone.

3. The method according to claim 1 or 2, wherein in method step (a) at least 90 mol% of IPN is converted into the mixture of C10B, 1 -cyano-1, 3, 3-trimethyl- cyclohex-4-ene and l-cyano-l,3,3-trimethyl-cyclohex-5-ene, and the selectivity to obtain Cl OB in said method step is preferably at least 60 mol%.

4. The method according to any one of the preceding claims, wherein method step (a) is carried out at a temperature between 0 and 30 °C.

5. The method according to any one of the preceding claims, wherein zinc is used in an amount of from 1.5 to 8 eq. related to 1 eq. IPN.

6. The method according to any one of the preceding claims, wherein zinc is used in form of zinc powder.

7. The method according to any one of the preceding claims, wherein zinc is activated or not.

8. The method according to any one of the preceding claims, wherein IPN is used in a concentration of equal to or lower than 60 g per liter of the organic solvent including hydrogen chloride as used in method step (a).

9. The method according to any one of the preceding claims, wherein the organic solvent used in method step (a) is selected from the group consisting of diethylether, tetrahydrofuran, cyclopentyl methyl ether (CPME), 2-methyl- tetrahydrofuran, tetrahydropyran, 4-methyltetrahydropyran, 1,4-di oxane, or combinations thereof.

10. The method according to any one of the preceding claims, wherein the hydrogenation of method step (b) is carried out in the presence of a hydrogenation catalyst.

11. l-cyano-l,3,3-trimethyl-cyclohexane (C10B) produced by the method as defined in any one of claims 1 to 10, or l-cyano-l,3,3-trimethyl-cyclohexane (C10B) containing l-cyano-l,3,3-trimethyl-cyclohex-4-ene and l-cyano-1,3,3- trimethyl-cyclohex-5-ene in a total amount of at least 0.1 ppm and at most 10 wt. -%.

12. Use of C10B according to claim 11 as polar solvent in a process for the production of hydrogen peroxide using alkylanthraquinones and/or tetrahydroalkylanthraquinones.

13. Use according to claim 12, wherein the hydrogen peroxide is produced in the form of an aqueous hydrogen peroxide solution having a total carbon organic (TOC) content of lower than 400 ppm, measured in the aqueous phase obtained in a test mimicking the final stage of the water extraction of hydrogen peroxide from oxidized working solution of the AO-process.

14. A process for manufacturing an aqueous hydrogen peroxide solution comprising the following steps:

- hydrogenating a working solution which comprises an alkylanthraquinone and/or a tetrahydroalkylantraquinone and a mixture of a non-polar organic solvent and a polar solvent - oxidizing the hydrogenated working solution to produce hydrogen peroxide, and

- isolating the hydrogen peroxide, wherein the polar organic solvent is the l-cyano-l,3,3-trimethyl-cyclohexane (C 1 OB) of claim 11.

15. The process according to claim 14, wherein the working solution comprises the Cl OB in an amount of 15 wt.-% or higher, based on the total weight of the working solution.