Method for concentrating a homogeneous catalyst system in an organic phase

Abstract

The present invention relates to a method for depleting a homogeneous catalyst system from an aqueous reaction phase and concentrating it into an organic phase, wherein the catalyst system is employed in the oxidation of an ethylenically unsaturated organic compound in a biphasic reaction mixture. Moreover, the present invention relates to a method for the oxidation of an ethylenically unsaturated organic compound, and biphasic mixtures as well as aqueous and organic phases obtained in such methods.

Description

[0001] 202400119 Foreign Filing

[0002] 1

[0003] METHOD FOR CONCENTRATING A HOMOGENEOUS CATALYST SYSTEM IN AN ORGANIC PHASE

[0004] The present invention relates to a method for depleting a homogeneous catalyst system from an aqueous reaction phase and concentrating it into an organic phase, wherein the catalyst system is employed in the oxidation of an ethylenically unsaturated organic compound in a biphasic reaction mixture. Moreover, the present invention relates to a method for the oxidation of an ethylenically unsaturated organic compound, and biphasic mixtures as well as aqueous and organic phases obtained in such methods.

[0005] Metal peroxo-complexes and in particular polyoxometalates play a crucial role in the homogeneous catalysis of various oxidation reactions of organic compounds. For instance, C. Venturello et al. describe a process for the epoxidation of olefins, such as 1 -octene and cyclohexene, using hydrogen peroxide in the presence of a polytungstophosphate catalyst and a tetraalkylammonium phase transfer catalyst, such as methyltrioctylammonium chloride, in a biphasic solvent mixture (J. Org. Chem. 1983, 48, 3831 -3833). Technical applications include the usage of such complexes for the epoxidation of cyclododecene (CDEN) with hydrogen peroxide as oxidant in a biphasic reaction mixture as has been shown in WO 2018 / 002114 A1 , EP 2 946 831 A2 and WO2021 / 085978A1 , or in the synthesis of 1 ,2-propanediol in WO 2023 / 152083 A1.

[0006] Especially when such homogeneous catalyst systems are used in industrial processes, the recovery of the catalyst system is of fundamental importance for economic and ecological reasons. However, recovery of a homogeneous catalyst system presents special challenges, since in homogeneous catalysis the catalyst and the reactants are in the same phase and simple physical separation methods like conventional filtration or centrifugation are often impractical or even fail.

[0007] One option to recover a homogeneous catalyst system from a reaction mixture is by using nanofiltration as disclosed in DE 10 2014 209 421 A1 for the recovery of a catalyst system used in the epoxidation of an unsaturated organic compound.

[0008] Moreover, WO 2018 / 002114 A1 describes a process for reactivating homogeneous catalyst systems from organic reaction mixtures, wherein after completion of the oxidation reaction the catalyst systems are first treated with an aqueous base, followed by acidification of the resulting mixture comprising the catalyst systems to a pH of at most 4 before the mixture can be recycled into the same oxidation reaction.

[0009] However, in particular when the homogeneous catalysis is carried out in a biphasic reaction system, the catalyst or inactive species thereof are normally present in both phases, so that the catalyst has to be recovered not only from one reaction phase but from both phases, the aqueous and the organic phase.

[0010] Consequently, there remains a need for providing an improved method for recovering a homogeneous catalyst system from a reaction mixture of an oxidation reaction. 202400119 Foreign Filing

[0011] 2

[0012] It has now surprisingly been found that in a reaction mixture of an oxidation of an ethylenically unsaturated organic compound the homogeneous catalyst system can be converted into a hydrophobic species after the reaction is substantially complete. It can be depleted from the aqueous phase and concentrated in the organic phase when the concentration of the oxidant is adjusted to less than 0.05 wt.%, based on the total weight of the aqueous phase, at a pH of less than 3.0. Due to its hydrophobic nature, the catalyst species formed can be easily separated from the aqueous phase which aqueous phase can then be discarded. The hydrophobic species is catalytically inactive, but can be reactivated and recycled into the oxidation process as described below.

[0013] This method provides the benefit that the aqueous phase does not comprise the catalyst system anymore and can be discarded after separation without the need for further reducing or removing environmentally harmful substances. Thus, no extensive recovery of the catalyst system from the aqueous phase is required.

[0014] The catalyst system can be recovered from the organic phase using, for example, the method described in WO 2018 / 002114 A1. Moreover, it has been found that reactivation can be improved when the organic phase comprising the concentrated catalyst system is combined with a basic aqueous phase and reused in an oxidation reaction without acidifying.

[0015] Accordingly, the present invention relates to a method for depleting a homogeneous catalyst system from an aqueous reaction phase and concentrating it into an organic phase, the catalyst system being employed in the oxidation of an ethylenically unsaturated organic compound with a peroxide as oxidant in a reaction mixture comprising the aqueous phase and the organic phase, the method comprising the steps of

[0016] (i) converting the catalyst into a more hydrophobic species by mixing the aqueous phase with the organic phase at a level of less than 0.05 wt.% of the oxidant, based on the total weight of the aqueous phase, and a pH of less than 3.0; and

[0017] (ii) separating the aqueous phase from the organic phase.

[0018] Moreover, the present invention relates to a method for the oxidation of an ethylenically unsaturated organic compound comprising: oxidizing an ethylenically unsaturated organic compound with a peroxide as oxidant in a mixture comprising a homogeneous catalyst system, an organic phase comprising the ethylenically unsaturated organic compound, an acidic aqueous medium and a phase transfer reagent, wherein the homogeneous catalyst system comprises at least one derivative of a transition metal of Group IVb, Vb and Vlb in its highest oxidation state, to obtain a reaction mixture comprising an organic phase comprising the oxidation product of the ethylenically unsaturated organic compound and residual ethylenically unsaturated organic compound, an aqueous reaction phase, the catalyst system, the phase transfer reagent and residual peroxide; and 202400119 Foreign Filing

[0019] 3 depleting the homogeneous catalyst system from the aqueous reaction phase and concentrating it into the organic phase according to the method described herein.

[0020] As used herein, the term "comprising" and variations thereof are used synonymously with the terms "including", "containing" and variations thereof and are understood to be open and non-limiting terms which do not exclude the presence of additional undescribed or unrecited elements, compounds, ingredients or process steps. As used herein, the term "consisting of is understood to exclude the presence of unspecified elements, compounds, ingredients or process steps. When the non-limiting terms “comprising”, “including” or “containing” are used in the present specification, the case of ’’consisting of is included therein. For example, a process described as “comprising” or “including” certain steps can consist of the explicitly recited steps or can further comprise one or more unrecited steps. Same applies, for example, to compositions and their corresponding explicitly described or non-recited ingredients.

[0021] In this application, the indefinite article "a" means one or more of what it denotes.

[0022] As stated above, the present invention relates to a method for depleting a homogeneous catalyst system from an aqueous reaction phase and concentrating it into an organic phase, the catalyst system being employed in the oxidation of an ethylenically unsaturated organic compound with a peroxide as oxidant in a reaction mixture comprising the aqueous phase and the organic phase, the method comprising the steps of (i) converting the catalyst into a more hydrophobic species by mixing the aqueous phase with the organic phase at a level of less than 0.05 wt.% of the oxidant, based on the total weight of the aqueous phase, and a pH of less than 3.0; and (ii) separating the aqueous phase from the organic phase.

[0023] The method thus allows a homogeneous catalyst system used in an oxidation in a biphasic mixture to be concentrated in the organic phase of this mixture to facilitate further purification or reuse of the catalyst system.

[0024] According to the present invention, the oxidation of an ethylenically unsaturated organic compound can be an epoxidation of an ethylenically unsaturated organic compound. In the oxidation according to the present invention a peroxide is used as an oxidant. Suitable peroxides are known to those skilled in the art and include 3-chloroperoxybenzoic acid, peroxybenzoic acid, peroxyacetic acid, peroxybenzimidic acid, tert-butylhydroperoxide, dimethyldioxirane, potassium hydrogen peroxo mo nosulfate and hydrogen peroxide, wherein hydrogen peroxide is the preferred peroxide.

[0025] The oxidation may be carried out in an organic solvent or can be carried out in the absence of an additional solvent, if the ethylenically unsaturated organic compound itself functions as solvent. Suitable organic solvents include, but are not limited to, dichloromethane, chloroform, tert-butanol, cyclohexane, benzene and acetonitrile.

[0026] As used herein, the term “ethylenically unsaturated organic compound” refers to an organic compound having at least one carbon-carbon double bond and / or at least one carbon-carbon triple bond, preferably 202400119 Foreign Filing

[0027] 4 at least one carbon-carbon double bond. Preference is given to olefins having a solubility in water at 20 °C of no more than 1 wt.%, preferably of no more than 0.5 wt.%. A solubility in water at 20 °C of 1 wt.%, as used herein, means that at a temperature of 20 °C no more than 10 g of the respective compound dissolves in 1000 g of distilled water. The ethylenically unsaturated organic compound preferably may be an organic compound having a total of at least six carbon atoms, such as from six to twenty carbon atoms, wherein such compounds more preferably may be cyclic compounds. Particularly preferred are cyclic unsaturated C12 compounds, especially cyclododecene (CDEN).

[0028] As used herein, the term "homogeneous catalyst system" is to be understood in the way it is generally understood by a skilled person in the field of organic synthesis, namely as a catalyst system used in homogeneous catalysis, wherein the catalyst is in the same phase as the reactants such as in case of a soluble catalyst in a solution. The homogeneous catalyst system catalyzes the oxidation of the ethylenically unsaturated organic compound in the biphasic reaction mixture. The homogeneous catalyst system according to the present invention can comprise at least one derivative of a transition metal of Group IVb, Vb and VI b in its highest oxidation state.

[0029] As used herein, the term “transition metal of Group IVb” refers to an element that is in Group IVb of the CAS version of the Periodic Table of the Elements as is shown, for example, in the Handbook of Chemistry and Physics, 63rdedition (1983), corresponding to Group 4 in the actual IUPAC numbering. Likewise, the terms “transition metal of Group Vb” and “transition metal of Group Vlb” refer to an element that is in Group Vb and Vlb, respectively, of the CAS version of the Periodic Table of the Elements as is shown, for example, in the Handbook of Chemistry and Physics, 63rdedition (1983), corresponding to Group 5 and 6, respectively, in the actual IUPAC numbering.

[0030] The at least one derivative of the transition metal of Group IVb, Vb and Vlb preferably may be selected from a derivative of tungsten (oxidation state 6), molybdenum (oxidation state 6) and vanadium (oxidation state 5).

[0031] Suitable derivatives include, for example, oxides, mixed oxides, oxygen-containing acids, salts of oxygencontaining acids, carbonyl derivatives, sulfides, chlorides, oxychlorides and alkanoates of tungsten, molybdenum and / or vanadium.

[0032] Preference is given to derivatives selected from salts of tungstic acid (H2WO4) or molybdic acid (H2MOO4) , or homo- or heteropolyoxometalates formed therefrom. Special preference is given to derivatives selected from alkali or alkaline earth metal salts of H2WO4 or H2MOO4, or homo- or heteropolyoxometalates formed therefrom, in particular to Na2WO4 or a homo- or heteropolyoxometalate formed therefrom.

[0033] A polyoxometalate is a polyatomic ion, usually an anion, comprising three or more transition metal oxyanions linked together by shared oxygen atoms to form closed 3-dimensional frameworks. Homopolyoxometalates are composed of only one kind of metal and oxygen, while 202400119 Foreign Filing

[0034] 5 heteropolyoxometalates are composed of one or more metals, oxygen and eventually a main group oxyanion, such as a phosphate or a silicate.

[0035] These derivatives can be formed or converted into the catalytically active species in situ. For instance, the catalyst system can further comprise phosphoric acid, a salt of phosphoric acid or a combination of both. For example, sodium tungstate can be used in combination with phosphoric acid to form a catalytically active polyoxometalate in situ. Phosphoric acid or salts thereof can, for instance, be used as a stabilizer for hydrogen peroxide and thus, if hydrogen peroxide is used as the oxidant, be added to the reaction mixture in this form in combination with the hydrogen peroxide.

[0036] The reaction mixture can further comprise a phase transfer reagent. A phase transfer reagent as used herein refers to a compound that facilitates the transition of another compound, e.g., a catalyst or a reactant, from one phase of a reaction mixture into another phase in which a reaction occurs. The phase transfer reagent according to the present invention can comprise a nitrogen atom, which is either permanently ionized, such as a quaternary ammonium compound, or can be reversibly protonated, such as a tertiary amine compound, and which contains more than 10 carbon atoms, preferably more than 15 carbon atoms. Suitable quaternary ammonium compounds can have the general formula [NR1R2R3R4]+X_wherein R1, R2, R3, and R4,each independently, may be a linear Ci to C20 alkyl group, a branched or cyclic C3 to C20 alkyl or an aryl group having from 6 to 10 carbon atoms, provided that the total number of carbon atoms in R1, R2, R3, and R4is at least 10, preferably at least 15, and X is the counterion for the ammonium group and may be, for instance, fluoride, chloride, bromide, iodide, bisulfate, formate, acetate, or propionate. Suitable tertiary amine compounds can have the general formula NR1R2R3wherein R1, R2, and R3, each independently, may be a linear Ci to C20 alkyl group, a branched or cyclic C3 to C20 alkyl or an aryl group having from 6 to 10 carbon atoms, provided that the total number of carbon atoms in R1, R2, and R3, is at least 10, preferably at least 15.

[0037] Suitable phase transfer reagents can be selected dependent on the ethy lenically unsaturated organic compound. For example, suitable phase transfer reagents are methyltrioctylammonium sulfate, Adogen® 464, which is a tri-(C8-Cio)-alkylammonium methyl salt available, for instance, from Merck KGaA (Darmstadt, Germany), trioctylamine, tridecylamine or a tri-(C8-Cio)-amine.

[0038] The term "biphasic mixture" as used herein refers to a mixture comprising two liquid phases being immiscible at ambient temperature, namely an aqueous phase and an organic phase. Unless stated otherwise, "ambient temperature" or "room temperature" as used herein refers to a temperature of 23 °C.

[0039] In the first step (step (i)) of the present method for depleting a homogeneous catalyst system from an aqueous phase and concentrating it into an organic phase the catalyst is converted into a more hydrophobic species by mixing the aqueous phase with the organic phase at a level of less than 0.05 wt.% of the oxidant, based on the total weight of the aqueous phase and at a pH of less than 3.0. The mixing in step (i) preferably is carried out at a pH in the range of from more than 1 .5 to less than 3.0, more preferably at a pH of from 1 .6 to 2.5. 202400119 Foreign Filing

[0040] 6

[0041] As used herein the term "pH" or "pH value" refers to the "apparent pH", which refers to a value determined by measurement with a glass electrode employing a commercial pH meter calibrated with aqueous buffer solutions of known pH for measuring dilute aqueous solutions. This apparent pH differs from the notional pH, i.e. , the negative logarithm of the hydrogen ion activity, by a constant value because the normal potential of the glass electrode in the aqueous phase of the reaction mixture, which comprises hydrogen peroxide and alcohols, is different than the normal potential in pure water.

[0042] In step (i) of the method according to the present invention, the organic phase and the aqueous phase of the biphasic reaction mixture in which the oxidation of the ethylenically unsaturated organic compound with the peroxide and the homogeneous catalyst system was carried out are mixed at a level of less than 0.05 wt.% of the oxidant, based on the total weight of the aqueous phase, and at a pH of less than 3.0.

[0043] By mixing the phases at an oxidant concentration of less than 0.05% by weight, based on the total weight of the aqueous phase, and a pH of less than 3.0, the catalyst is converted into a more hydrophobic species, increasing the concentration of the catalyst in the organic phase and decreasing it in the aqueous phase. Thus, the catalyst system is depleted from the aqueous phase and concentrated into the organic phase.

[0044] The term “more hydrophobic species” as used herein refers to a species of the catalyst which has a less tendency to be solvated by water than the species of the catalyst being present in the reaction mixture prior to lowering the concentration of the oxidant to less than 0.05 wt.%, based on the total weight of the aqueous phase, and adjusting the pH to less than 3.0.

[0045] The mass ratio of the organic phase to the aqueous phase in the method according to the present invention can be from 1 :2 to 6:1 , preferably from 3:1 to 6:1 and even more preferably from 4:1 to 5:1 .

[0046] After carrying out step (i) the aqueous phase can comprise less than 10 wt.% of the transition metal, preferably less than 5 wt.%, more preferably less than 2.5 wt.% and even more preferably less than 2.0 wt.%, and the organic phase can comprise more than 90 wt.% of the transition metal, preferably more than 95 wt.%, more preferably more than 97.5 wt.% and even more preferably more than 98.0 wt.%, based on the total weight of the transition metal in the reaction mixture.

[0047] In the second step (ii) the aqueous phase is separated from the organic phase. Said separation can preferably be carried out by using a phase separation vessel.

[0048] The organic phase of the reaction mixture comprises at least the ethylenically unsaturated organic compound, the oxidized product thereof and at least a part of the catalyst system. The organic phase can further comprise at least a part of the phase transfer reagent, if used, and, in case an organic solvent is used, the organic solvent. 202400119 Foreign Filing

[0049] 7

[0050] The organic phase according to the present invention can comprise the ethylenically unsaturated organic compound and the oxidized product thereof in a weight ratio of lower than 20:80, preferably lower than 10:90, more preferably lower than 5:95, and even more preferably lower than 3:97. The organic phase can comprise the ethylenically unsaturated organic compound and the oxidized product thereof in a weight ratio of equal to or greater than 1 :99. The weight ratio of the ethylenically unsaturated organic compound to the oxidized product thereof in the organic phase may range from lower than 20:80 to 1 :99, preferably from lower than 10:90 to 1 :99, more preferably from lower than 5:95 to 1 :99. Stated otherwise, the conversion of the ethylenically unsaturated organic compound in the preceding oxidation reaction can range from more than 80% to 99.0%, preferably from more than 90% to 99.0%, more preferably from more than 95% to 99.0%, or even more preferably from more than 97% to 99.0%. The organic phase can comprise a combined amount of more than 80 wt.% of the ethylenically unsaturated organic compound to be oxidized and the oxidation product thereof, based on total weight of the organic phase.

[0051] After separating the aqueous phase from the organic phase in step (ii) the method may further comprise separating an oxidation product of the ethylenically unsaturated organic compound from the organic phase comprising the catalyst system by membrane filtration, thus further concentrating the catalyst system. Suitable membranes and process parameters for membrane filtration are described, for instance, in EP 2 946 831 A2. The membrane used for filtering the organic phase preferably comprises a membrane material based on silicone acrylate, polydimethylsiloxane (PDMS), polyimide or combinations thereof. Suitable commercially available membranes for concentrating the catalyst system in the organic phase are, for example, PuraMem® S600 from Evonik Operations GmbH (Marl, Germany) and oNF-2 from BORSIG Membrane Technology GmbH (Rheinfelden, Germany). When using membrane filtration for concentrating the catalyst system, the catalyst system is concentrated in the retentate. The term "retentate", as used herein, refers to the effluent from the membrane withdrawn upstream of the membrane. The material which passes through the membrane is known as "permeate" and is withdrawn downstream of the membrane. In the method according to the present invention, the permeate mainly comprises a mixture of the oxidized ethylenically unsaturated organic compound and the ethylenically unsaturated compound, i.e., the product of the oxidation reaction, meaning that the permeate comprises the mixture in an amount of at least 50 wt.-%, based on the total weight of the permeate. The amount of catalyst system retained in the remaining organic phase, i.e., the retentate, can be determined based on the amount of retained transition metal. In particular, the method allows retention of more than 50 wt.-% of the transition metal in the retentate, preferably more than 70 wt.-% and more preferably more than 90 wt.-%, based on the total amount of transition metal in the organic phase prior to filtration. The amount of retained transition metal may be detected using ICP-MS (inductively coupled plasma mass spectrometry) or XRF (X-ray fluorescence analysis).

[0052] As stated above, the present invention further relates to a method for the oxidation of an ethylenically unsaturated organic compound. In the method according to the present invention, an ethylenically unsaturated organic compound is oxidized with a peroxide as oxidant in a mixture comprising a homogeneous catalyst system, an organic phase comprising the ethylenically unsaturated organic compound, an acidic aqueous medium and a phase transfer reagent, wherein the homogeneous catalyst 202400119 Foreign Filing

[0053] 8 system comprises at least one derivative of a transition metal of Group IVb, Vb and Vlb in its highest oxidation state. Thereby a reaction mixture comprising an organic phase comprising the oxidation product of the ethylenically unsaturated organic compound and residual ethylenically unsaturated organic compound, an aqueous reaction phase, at least a part of the catalyst system, the phase transfer reagent and residual peroxide is obtained. After oxidizing the ethylenically unsaturated organic compound, the homogeneous catalyst system is depleted from the aqueous reaction phase and concentrated into the organic phase according to the method described herein above.

[0054] The ethylenically unsaturated organic compound oxidized in the method for oxidation according to the present invention refers to an ethylenically unsaturated organic compound as described above. Likewise, the peroxide, the phase transfer reagent, the homogeneous catalyst system and the derivative of a transition metal of Group IVb, Vb and Vlb refer to the compounds as described above.

[0055] The oxidation of the ethylenically unsaturated organic compound according to the present invention can be carried out in one or more stirred tank reactors either in a continuous process or in a batch process.

[0056] Consequently, the reaction mixture used in the method for depleting the homogeneous catalyst system from an aqueous phase or obtained in the method for the oxidation of an ethylenically unsaturated organic compound according to the present invention can be obtained in a process carried out in one or more stirred tank reactors.

[0057] The reaction mixture obtained in a process carried out in one or more stirred tank reactors can be obtained in a continuous process using at least two reactors, more preferably three to five reactors, wherein the oxidant is only dosed into some of the reactors, wherein at least in the last reactor essentially no oxidation takes place. It may be preferred that the oxidant is dosed in all reactors except for the last one. For instance, if a series of three stirred tank reactors is used, the oxidant may be dosed into both, the first and second stirred tank reactor, but not the third one. As used herein the wording "essentially no oxidation" means that less than 1 wt.% of any potentially remaining ethylenically unsaturated organic compound is oxidized in this reactor.

[0058] Alternatively, the reaction mixture can be obtained in a batch process, wherein in the final phase no oxidant is added and essentially no oxidation takes place. As used herein the wording "essentially no oxidation" means that less than 1 wt.% of any potentially remaining ethylenically unsaturated organic compound is oxidized in this phase.

[0059] By controlling the dosage and presence of the oxidant as described above, an oxidant concentration of less than 0.05 wt.% in step (i) in the method for depleting a homogeneous catalyst system can be achieved. Thus, when not using the oxidant in such an excess to have productivity in all reactors, , as it is the usual practice in many oxidation reactions due to the rather low cost of oxidants such as hydrogen peroxide, despite a slightly lower total conversion of the ethylenically unsaturated organic compound, using the method of the present invention, the overall oxidation process may in fact be more cost effective 202400119 Foreign Filing

[0060] 9 than these prior art processes. This is due to the fact that, firstly, the catalyst can be separated easily and effectively from the aqueous phase which can then be discarded without the need for further purifying it. Further, the hydrophobic inactive catalyst species separated from the aqueous phase can effectively be reactivated and recycled into the oxidation process. As used herein, productivity of a reactor means a conversion of at least 50% of the CDEN introduced into the respective reactor.

[0061] Alternatively, a reducing agent such as sodium sulfite can be added after the oxidation reaction has taken place in the first reactor or in the subsequent reactors to cause the peroxide oxidant to decompose and to reach the concentration of less than 0.05 wt.% of the oxidant.

[0062] Furthermore, a base can be added after the oxidation reaction has taken place in the first reactor or in the subsequent reactors to stabilize the epoxide while the catalyst is converted into a more hydrophobic species.

[0063] Preference is given to a continuous process in which a series of at least three stirred tank reactors is used and the concentration of peroxide in the aqueous phase decreases in the series of reactors. The concentration of peroxide preferably is in the range of from 0.7 to 2.0 wt.% in the first reactor and less than 0.05 wt.% in the last reactor, each based on the total weight of the aqueous phase. The concentration of the peroxide in any reactor between the first and last reactor is between the concentration of the peroxide in the first reactor and the last reactor.

[0064] In case the reaction mixture is obtained in a batch process as described above, the concentration of peroxide in the aqueous phase decreases in the course of the oxidation reaction and is preferably in the range of from 0.7 to 2.0 wt.%, during the first phase of the oxidation reaction, less than 0.1 wt.% upon completing the oxidation reaction, and less than 0.05 wt.% after separating the aqueous phase from the organic phase in step (ii), each based on the total weight of the aqueous phase.

[0065] During the method for depleting a catalyst system from an aqueous phase and concentrating it into an organic phase according to the present invention, the concentration of the transition metal in the organic phase increases and the concentration of the transition metal in the aqueous phase decreases in the course of the reaction. When the method is carried out in a series of at least three stirred tanks in a continuous process as described above, the reaction mixture can have a weight ratio of about 4:1 to 5:1 of organic to aqueous phase and the amount of transition metal preferably is in the range of from 1400 to 1600 ppm in the organic phase in the first reactor, based on the total weight of the organic phase in said reactor, and in the range of from 3000 to 4000 ppm in the aqueous phase in the first reactor, based on the total weight of the aqueous phase in said reactor. The amount of transition metal in the organic phase in both the last reactor and the phase separation vessel can be in the range of from 2000 to 2500 ppm, based on the total weight of the organic phase in said reactor or vessel, respectively, and less than 200 ppm in the aqueous phase in both the last reactor and the phase separation vessel, based on the total weight of the aqueous phase in said reactor or vessel, respectively. 202400119 Foreign Filing

[0066] 10

[0067] When the method is carried out in a series of at least three stirred tanks in a continuous process as described above, the molar ratio of unreacted unsaturated organic compound to unreacted peroxide increases in the last reactor and preferably is about 4:1 in the first and second reactor, and more than 10:1 in the third reactor.

[0068] Both, the method for depleting a homogeneous catalyst system and the method for the oxidation of an ethylenically unsaturated organic compound can further comprise the reactivation of the homogeneous catalyst system from the organic phase comprising the additional step (iii) of reactivating the catalyst system by adding at least one aqueous base to the organic phase comprising the catalyst system obtained in step (ii) to form a biphasic mixture having a pH of at least 7.0. The biphasic mixture obtained in step (iii) can in a subsequent step (iva) be fed to a mixture comprising an ethylenically unsaturated organic compound, a peroxide and an acidic aqueous medium without separating the aqueous phase from the organic phase and without acidifying said mixture before feeding it to the mixture. Alternatively, either the biphasic mixture obtained in step (iii) or, after phase separation, the aqueous phase thereof can be treated with an acid in step (ivb) in the presence of a peroxide before feeding the treated biphasic mixture or both, the treated aqueous phase and the organic phase obtained from separating the biphasic mixture, respectively, to a mixture comprising an ethylenically unsaturated organic compound and an acidic aqueous medium.

[0069] The biphasic mixture in step (iii) preferably has a pH of 7.0 to 11 .0, more preferably of from 8.0 to 10.0 and most preferably of from 8.0 to 9.0.

[0070] The aqueous base added in step (iii) of the method of the present invention can comprise ammonia, at least one alkali metal hydroxide or mixtures thereof, wherein the alkali metal hydroxide preferably is selected from sodium hydroxide and potassium hydroxide.

[0071] In a further optional step of the method according to the present invention the aqueous phase obtained in step (ii) of the method can be discarded without the need for further reducing or removing environmentally harmful substances.

[0072] The present invention further relates to an organic phase comprising an olefin and an oxidation product thereof in a weight ratio of lower than 5:95 and either 2000 to 2500 ppm (option 1) or 15000 to 30000 ppm (option 2) of a transition metal of Group IVb, Vb and Vlb in its highest oxidation state from a homogeneous catalyst system for the oxidation of the olefin, based on the total weight of the organic phase.

[0073] Such organic phases can be obtained from the methods according to the present invention after separating the aqueous phase from the organic phase. The organic phase of option 1 as described above can be obtained from the method according to the present invention after separating the aqueous phase from the organic phase in step (ii). The organic phase of option 2 can be obtained from the method according to the present invention after separating the aqueous phase from the organic phase in step (ii) 202400119 Foreign Filing

[0074] 11 and further separating the oxidation product of the ethylenically unsaturated organic compound from the resulting organic phase comprising the catalyst system by membrane filtration.

[0075] The present invention further relates to a biphasic mixture comprising the organic phase of option 1 as described above, i.e., an organic phase comprising an olefin and an oxidation product thereof in a weight ratio of lower than 5:95 and 2000 to 2500 ppm of a transition metal of Group IVb, Vb and Vlb in its highest oxidation state from a homogeneous catalyst system for the oxidation of the olefin, based on the total weight of the organic phase, and an acidic aqueous phase having a pH of less than 3.0, an amount of peroxide of less than 0.05 wt.% and less than 200 ppm of the transition metal, based on the total weight of the aqueous phase.

[0076] Such a biphasic mixture can be obtained from the methods according to the present invention before separating the aqueous phase from the organic phase in step (ii).

[0077] Moreover, the present invention relates to a biphasic mixture comprising the organic phase of option 2 as described above, i.e., an organic phase comprising an olefin and an oxidation product thereof in a weight ratio of lower than 3:97 and 15000 to 30000 ppm of a transition metal of Group IVb, Vb and Vlb in its highest oxidation state from a homogeneous catalyst system for the oxidation of the olefin, based on the total weight of the organic phase, and an aqueous phase being essentially free of the transition metal and peroxide, wherein "essentially free" means that the aqueous phase comprises less than 200 ppm of the transition metal and less than 0.05 wt.% of the peroxide, based on the total weight of the aqueous phase.

[0078] Such a biphasic mixture can be obtained from the methods according to the present invention before separating the aqueous phase from the organic phase in step (ii).

[0079] Furthermore, the present invention relates to an aqueous phase obtained by separating the aqueous phase of the biphasic mixture described herein before from the organic phase, wherein the aqueous phase comprises 5 ppm or more and less than 200 ppm of the transition metal, based on the total weight of the aqueous phase. The aqueous phase can be discarded without the need for further reducing or removing environmentally harmful substance.

[0080] Such an aqueous phase can be obtained from the methods according to the present invention, after the separation of the phases in step (ii).

[0081] The following clauses summarizes some aspects of the present invention:

[0082] In a first aspect the present invention relates to a method for depleting a homogeneous catalyst system from an aqueous reaction phase and concentrating it into an organic phase, the catalyst system being employed in the oxidation of an ethylenically unsaturated organic compound with a peroxide as oxidant in a reaction mixture comprising the aqueous phase and the organic phase, the method comprising the steps of (i) converting the catalyst into a more hydrophobic species by mixing the aqueous phase with the 202400119 Foreign Filing

[0083] 12 organic phase at a level of less than 0.05 wt.% of the oxidant, based on the total weight of the aqueous phase, and a pH of less than 3.0; and separating the aqueous phase from the organic phase.

[0084] In a second aspect the present invention relates to the method of the first aspect, wherein the reaction mixture further comprises a phase transfer reagent.

[0085] In a third aspect the present invention relates to the method of the first or second aspect, wherein the catalyst system comprises at least one derivative of a transition metal of Group IVb, Vb and Vlb in its highest oxidation state.

[0086] In a fourth aspect the present invention relates to the method of any one of the preceding aspects, wherein in step (i) the pH is in the range of from more than 1 .5 to less than 3.0, preferably of from 1 .6 to 2.5.

[0087] In a fifth aspect the present invention relates to the method of any one of the preceding aspects, wherein the mass ratio of the organic phase to the aqueous phase in the reaction mixture is from 1 :2 to 6:1 , preferably from 3:1 to 6:1 and even more preferably from 4:1 to 5:1 .

[0088] In a sixth aspect the present invention relates to the method of any one of the preceding aspects, wherein after carrying out step (i) the aqueous phase comprises less than 10 wt.% of the transition metal, preferably less than 5 wt.%, more preferably less than 2.5 wt.% and even more preferably less than 2.0 wt.%, and the organic phase comprises more than 90 wt.% of the transition metal, preferably more than 95 wt.%, more preferably more than 97.5 wt.% and even more preferably more than 98.0 wt.%, based on the total weight of the transition metal in the reaction mixture.

[0089] In a seventh aspect the present invention relates to the method of any one of the preceding aspects, wherein the organic phase comprises the ethy lenically unsaturated organic compound and the oxidized product thereof in a weight ratio of lower than 20:80, preferably lower than 10:90, more preferably lower than 5:95, and even more preferably lower than 3:97.

[0090] In an eighth aspect the present invention relates to the method of any one of the preceding aspects, wherein the organic phase comprises the ethy lenically unsaturated organic compound and the oxidized product thereof in a weight ratio of greater than 1 :99.

[0091] In a ninth aspect the present invention relates to the method of any one of the preceding aspects, wherein the conversion of the ethylenically unsaturated organic compound in the oxidation reaction ranges from more than 80% to 99.0%, preferably from more than 90% to 99.0%, more preferably from more than 95% to 99.0%, or even more preferably from more than 97% to 99.0%.

[0092] In a tenth aspect the present invention relates to the method according to any one of the preceding aspects, further comprising further concentrating the catalyst system in the organic phase after step (ii) by 202400119 Foreign Filing

[0093] 13 separating an oxidation product of the ethylenically unsaturated organic compound from the organic phase comprising the catalyst system by membrane filtration.

[0094] In an eleventh aspect the present invention relates to a method for the oxidation of an ethylenically unsaturated organic compound comprising: oxidizing an ethylenically unsaturated organic compound with a peroxide as oxidant in a mixture comprising a homogeneous catalyst system, an organic phase comprising the ethylenically unsaturated organic compound, an acidic aqueous medium and a phase transfer reagent, wherein the homogeneous catalyst system comprises at least one derivative of a transition metal of Group IVb, Vb and Vlb in its highest oxidation state, to obtain a reaction mixture comprising an organic phase comprising the oxidation product of the ethylenically unsaturated organic compound and residual ethylenically unsaturated organic compound, an aqueous reaction phase, the catalyst system, the phase transfer reagent and residual peroxide; and depleting the homogeneous catalyst system from the aqueous reaction phase and concentrating it into the organic phase according to the method of any of the preceding claims.

[0095] In a twelfth aspect the present invention relates to the method of any one of the preceding aspects, wherein the catalyst system further comprises phosphoric acid and / or a salt thereof.

[0096] In a thirteenth aspect the present invention relates to the method of any one of the preceding aspects, wherein the at least one derivative of the transition metal of Group IVb, Vb and Vlb is selected from a derivative of tungsten, molybdenum and vanadium, wherein the derivative preferably is selected from salts of H2WO4 or H2MOO4, or homo- or heteropolyoxometalates formed therefrom, more preferably from alkali or alkaline earth metal salts of H2WO4 or H2MOO4, or homo- or heteropolyoxometalates formed therefrom, and most preferably is Na2WO4 or a homo- or heteropolyoxometalate formed therefrom.

[0097] In a fourteenth aspect the present invention relates to the method according to any one of the preceding aspects, wherein the oxidant is hydrogen peroxide.

[0098] In a fifteenth aspect the present invention relates to the method according to any one of aspects 2 to 13, wherein the phase transfer reagent comprises a nitrogen atom, which is either permanently ionized or can be reversibly protonated and which contains more than 10 carbon atoms, preferably more than 15 carbon atoms.

[0099] In a sixteenth aspect the present invention relates to the method according to any one of the preceding aspects, wherein the oxidation comprises an epoxidation of an olefin and the olefin has a solubility in water at 20 °C of no more than 1 wt.%, preferably of no more than 0.5 wt.%.

[0100] In a seventeenth aspect the present invention relates to the method according to any one of the preceding aspects, wherein the organic phase comprises a combined amount of more than 80 wt.% of the ethylenically unsaturated organic compound to be oxidized and the oxidation product thereof, based on total weight of the organic phase. 202400119 Foreign Filing

[0101] 14

[0102] In an eighteenth aspect the present invention relates to the method according to any one of the preceding aspects, wherein the reaction mixture is obtained in a process carried out in one or more stirred tank reactors.

[0103] In a nineteenth aspect the present invention relates to the method according to aspect eighteen, wherein the reaction mixture is obtained in a continuous process using at least two reactors, more preferably three to five reactors, wherein the oxidant is only dosed into some of the reactors, wherein in the last reactor essentially no oxidation takes place.

[0104] In a twentieth aspect the present invention relates to the method according to aspect eighteen, wherein the reaction mixture is obtained in a batch process, wherein in the final phase of the reaction no oxidant is added and essentially no oxidation takes place.

[0105] In a twenty-first aspect the present invention relates to the method of aspect nineteen, wherein in the continuous process a series of at least three stirred tank reactors is used and the concentration of peroxide in the aqueous phase decreases in the series of reactors and preferably is in the range of from 0.7 to 2.0 wt.% in the first reactor and less than 0.05 wt.% in the last reactor, each based on the total weight of the aqueous phase.

[0106] In a twenty-second aspect the present invention relates to the method of aspect twenty, wherein in the batch process the concentration of peroxide in the aqueous phase decreases in the course of the oxidation reaction and is preferably in the range of from 0.7 to 2.0 wt.%, during the first phase of the oxidation reaction, less than 0.1 wt.% upon completing the oxidation reaction, and less than 0.05 wt.% after separating the aqueous phase from the organic phase in step (ii), each based on the total weight of the aqueous phase.

[0107] In a twenty-third aspect the present invention relates to the method according to any one of aspects eighteen to twenty-two, wherein the concentration of the transition metal in the organic phase increases and the concentration of the transition metal in the aqueous phase decreases in the course of the reaction, and in a reaction mixture of a continuous process having a weight ratio of about 4:1 to 5:1 of organic to aqueous phase preferably is in the range of from 1400 to 1600 ppm in the organic phase in the first reactor, based on the total weight of the organic phase in said reactor, and in the range of from 3000 to 4000 ppm in the aqueous phase in the first reactor, based on the total weight of the aqueous phase in said reactor; in the range of from 2000 to 2500 ppm in the organic phase in both the last reactor and the phase separation vessel, based on the total weight of the organic phase in said reactor or vessel, respectively, and less than 200 ppm in the aqueous phase in both the last reactor and the phase separation vessel, based on the total weight of the aqueous phase in said reactor or vessel, respectively.

[0108] In a twenty-fourth aspect the present invention relates to the method according to any one of aspects eighteen to twenty-three, wherein the weight ratio of unreacted unsaturated organic compound to 202400119 Foreign Filing

[0109] 15 unreacted peroxide increases in the last reactor in the continuous process being preferably about 4:1 in the first reactors and more than 10:1 in the last reactor.

[0110] In a twenty-fifth aspect the present invention relates to the method according to any one of the preceding aspects, wherein in a continuous process the organic phase is separated from the aqueous phase using a phase separation vessel.

[0111] In a twenty-sixth aspect the present invention relates to the method according to any one of the preceding aspects, further comprising reactivating the homogeneous catalyst system from the organic phase comprising the additional steps of: (iii) reactivating the catalyst system by adding at least one aqueous base to the organic phase comprising the catalyst system obtained in step (ii) to form a biphasic mixture having a pH of at least 7.0; and optionally (iva) feeding the biphasic mixture obtained in step (iii) to a mixture comprising an ethylenically unsaturated organic compound, a peroxide and an acidic aqueous medium without separating the aqueous phase from the organic phase and without acidifying said mixture before feeding it to the mixture; or (ivb) treating either the biphasic mixture obtained in step (iii) or, after phase separation, the aqueous phase thereof, with an acid in the presence of a peroxide before feeding the treated biphasic mixture or both, the treated aqueous phase and the organic phase obtained from separating the biphasic mixture, respectively, to a mixture comprising an ethylenically unsaturated organic compound and an acidic aqueous medium.

[0112] In a twenty-seventh aspect the present invention relates to the method according to aspect twenty-six, wherein in step (iii) the biphasic mixture has a pH of 7.0 to 11.0, preferably of from 8.0 to 10.0, more preferably of from 8.0 to 9.0.

[0113] In a twenty-eighth aspect the present invention relates to the method according to any one of aspects twenty-six or twenty-seven, wherein the aqueous base added in step (iii) comprises ammonia, at least one alkali metal hydroxide or mixtures thereof, wherein the alkali metal hydroxide preferably is selected from sodium hydroxide and potassium hydroxide.

[0114] In a twenty-ninth aspect the present invention relates to the method according to any one of the preceding aspects, further comprising the step of discarding the aqueous phase obtained in step (ii) without the need for further reducing or removing environmentally harmful substances.

[0115] In a thirtieth aspect the present invention relates to an organic phase comprising an olefin and an oxidation product thereof in a weight ratio of lower than 3:97 and equal to or greater than 1 :99 and either 2000 to 2500 ppm (option 1) or 15000 to 30000 ppm (option 2) of a transition metal of Group IVb, Vb and Vlb in its highest oxidation state from a homogeneous catalyst system for the oxidation of the olefin, based on the total weight of the organic phase.

[0116] In a thirty-first aspect the present invention relates to a biphasic mixture comprising the organic phase according to the first option of aspect thirty and an acidic aqueous phase having a pH of less than 3.0, an 202400119 Foreign Filing

[0117] 16 amount of peroxide of less than 0.05 wt.% and less than 200 ppm of the transition metal, based on the total weight of the aqueous phase.

[0118] In a thirty-second aspect the present invention relates to a biphasic mixture comprising the organic phase according to the second option of aspect thirty and an aqueous base being essentially free of the transition metal and peroxide.

[0119] In a thirty-third aspect the present invention relates to an aqueous phase obtained by separating the aqueous phase of the biphasic mixture according to aspect thirty-one from the organic phase, wherein the aqueous phase comprises 5 ppm or more and less than 200 ppm of the transition metal, based on the total weight of the aqueous phase. Said aqueous phase can be discarded without the need for further reducing or removing environmentally harmful substance.

[0120] Figures

[0121] FIG. 1 shows the dependence of the concentration of tungsten in the aqueous phase on the concentration of peroxide. The x-axis of the diagram indicates the concentration of hydrogen peroxide in the aqueous phase after phase separation. The y-axis of the diagram indicates the ratio of the concentration of tungsten in the aqueous phase after phase separation to the concentration of tungsten in the aqueous phase of the first reactor.

[0122] FIG 2 shows the dependence of the concentration of tungsten in the aqueous phase on the pH of the aqueous phase. The x-axis of the diagram indicates the pH value of the aqueous phase after phase separation. The y-axis of the diagram indicates the ratio of the concentration of tungsten in the aqueous phase after phase separation to the concentration of tungsten in the aqueous phase of the first reactor.

[0123] Examples

[0124] Example 1

[0125] An epoxidation of cyclic unsaturated C12 compounds was carried out in a continuous process in a cascade of three stirred tank reactors. The cascade comprised two reactors each having a 5 liter nominal capacity and, as a final stage, a third stirred tank having a 25 liter nominal capacity. The content of the first two reactors was heated in an oil bath to 90 °C and that of the final reactor was heated in an oil bath to 80 °C.

[0126] To the first reactor 1.5 kg / h of cyclic unsaturated C12 compound (94 wt.% CDEN and 6 wt.% of CDAN), Adogen® 464 methyl sulfate (PTC), sodium tungstate, phosphoric acid, sulfuric acid and a 60% H2O2 solution was fed. The pH value of the reaction mixture was adjusted to a pH of 1 .60 by adding sulfuric acid. 202400119 Foreign Filing

[0127] 17

[0128] The reaction mixture was passed into a second reactor. In addition, a further quantity of H2O2 was metered into the second reactor. In total, a ratio of 1 .01 to 1 .06 mol H2O2 per mol of CDEN was added to the first and second reactor. The biphasic reaction mixture was passed from the second reactor into the third reactor, where additionally 10 g / l 1 N NaOH was added.

[0129] From the third reactor the reaction mixture was fed into a phase separation vessel to let the organic phase separate from the aqueous phase. The organic phase was supplied to a continuous membrane system using a pump and the aqueous phase was discarded.

[0130] The residence time in each of the first and second reactor was approximately 2.5 h, while in the third reactor it was approximately 12.5 h. Residence time, as used herein, is the total average amount of time a discrete quantity of reagent spends inside the reactor. For an ideal continuously stirred-tank reactor, the theoretical residence time is equal to the reactor volume divided by the fluid flow rate.

[0131] The organic phase was fed to a membrane unit employing a oNF-2® from Borsig Membrane Technology GmbH (Gladbeck, Germany) operating at 60 °C and a transmembrane-pressure of 40 bar. The organic phase was separated into permeate and retentate in a way such that 10 wt.% of the feed was obtained as retentate and 90 wt.% as permeate. The membrane was used as 2,5"x20" spiral-wound element to provide a sufficient permeate flow to process the feedflow of the organic phase and to provide an excess permeate-flow at the same time. The excess permeate-flow not needed for the permeate access was recycled backwards to the feed.

[0132] The retentate was fed into a further stirred tank with a nominal capacity of 5 liter.

[0133] A TO M aqueous sodium hydroxide solution was added and the biphasic mixture was adjusted to a pH of 8.5. The pH value was monitored in the stirred biphasic mixture using an online pH electrode and controlled with manual measurements using a Knick MEMO SES SE55X / 1-NMSN sensor and a Knick Portavo 940X Multi 84461 / 205892 pH meter both from Knick Elektronische Messgerate GmbH & Co. KH (Berlin, Germany).

[0134] The biphasic mixture having a pH of 8.5 was transferred into a stirred vessel with a nominal capacity of 5 liter. Subsequently, the reaction mixture was recycled into the first reactor of the cascade.

[0135] The epoxide in the biphasic mixture obtained from an epoxidation process is preferably formed in an oxidation of an ethylenically unsaturated organic compound as defined above, wherein the peroxide more preferably is monoepoxycyclododecane. The amount of epoxide can for example be determined by gas chromatography with a flame ionization detector (GC-FID) using, for instance, a GC-2014 gas chromatograph from Shimadzu Deutschland GmbH (Duisburg, Germany). The determination can be carried out as follows: a sample of the biphasic mixture is centrifuged at room temperature (23 °C) for 1 min at 4000 rpm for obtaining a complete phase separation. 100 mg of the organic phase is weighed into a GC vial and diluted with standard solution by a factor of 10. The standard solution comprises 1 wt.-% of 202400119 Foreign Filing

[0136] 18 tetradecane and is further filled up with acetone. The measurement is performed using a Shimadzu GC- 2014 gas chromatograph with a Supelcowax-10 column (length of 60 m, diameter of 0.32 mm and film thickness of 0.25 pm) with a flame ionization detector and a SPL-10 Split Injector. The sample is injected at 150 °C with a split of 1 :10. The initial column temperature is 180 °C, which is hold for 10 min, then increased with a temperature ramp of 5 K / min to 200 °C and kept at this temperature for 35 min. Quantification of the products is determined by comparing the area of the products with the area of tetradecane as internal standard in correlation with the initial weight and a response factor, which is determined beforehand by recovery of the pure substances in a concentration series.

[0137] The amount of the transition metal in the biphasic mixture can be determined by X-ray fluorescence spectroscopy using, for instance, a SPECTRO XEPOS spectrometer of type 16004851 from SPECTRO Analytical Instruments GmbH (Kleve, Germany). For doing so, a sample is centrifuged at room temperature (23 °C) for 1 min at 4000 rpm for complete phase separation. The phases are separated by pipetting and 5 g of each phase is transferred into a single usage cuvette having a diameter of 32 mm from SPECTRO Analytical Instruments GmbH (Kleve, Germany). The concentration is determined via X- ray fluorescence analysis using a SPECTRO XEPOS spectrometer, type 16004851 from SPECTRO Analytical Instruments GmbH (Kleve, Germany). The sample chamber is inertized with helium. The amount of the transition metal is determined using a method calibrated with the pure substances, for instance sodium tungstate and phosphoric acid (75%).

[0138] Using these absolute methods as references the concentration of epoxide and ethylenically unsaturated organic compound can also be quantified online during the reaction using a Kaiser Optical Systems Rxn2 Raman analyzer from Endress+Hauser Group Services AG (Reinach, Switzerland) with a 785 nm laser, and immersion short focus probes and indirect hard modeling to quantify CDEN and CDAN-epoxide concentration and a partial least-square model for tungstate and hydrogen peroxide employing the Peaxact Software from S-PACT (Aachen, Germany). An online measurement as used herein refers to a method taking place continuously but not, as for inline measurements, directly in the process but, for example, in a bypass, through which the reactor content is continuously passed.

[0139] The following table (Table 1) provides an overview of the total conversion of CDEN in the course of the reaction, the partial conversion of CDEN in the individual reactors and the distribution of tungstate in the organic and aqueous phases during the course of the reaction.

[0140] The conversion of CDEN was determined using the following formula with n being the molecular flow of CDEN and determining the concentration using the Raman method described above.

[0141] The amount of tungsten in the respective organic and aqueous phases was determined using X-ray fluorescence spectroscopy as described above. 202400119 Foreign Filing

[0142] 19

[0143] Table 1 : Conversion of CDEN and distribution of tungstate

[0144] * partial conversion in the respective reactor

[0145] As can be seen from Table 1 , the method according to the present invention enables the catalyst to be depleted from the aqueous phase and concentrated in the organic phase. During the course of the oxidation reaction, the concentration of H2O2 in the aqueous phase decreases. Simultaneously, the amount of tungstate in the aqueous phase decreases and increases in the organic phase.

[0146] Dependence of the tungsten concentration on the concentration of H2O2

[0147] The amount of tungsten in the aqueous phase was studied in relation to the concentration of hydrogen peroxide in the aqueous phase. The results are shown in the diagram in Figure 1 , wherein the x-axis indicates the concentration of hydrogen peroxide in the aqueous phase after phase separation and the y- axis indicates the ratio of the concentration of tungsten in the aqueous phase after phase separation to the concentration of tungsten in the aqueous phase of the first reactor. It can be seen from the results that the ratio of the concentration of tungsten in the aqueous phase after phase separation to the concentration of tungsten in the aqueous phase of the first reactor is generally less than 0.1 for a hydrogen peroxide concentration of less than 0.05 wt.-% and decreases further when the hydrogen peroxide concentration is even lower. This means that the amount of tungsten in the aqueous phase decreases significantly in the course of the reaction, allowing a concentration of the catalyst system in the organic phase from which it can be recycled. 202400119 Foreign Filing

[0148] 20 ce of the n concentration on the

[0149] The amount of tungsten in the aqueous phase after step (ii) was studied in relation to the pH in the aqueous phase. The results are shown in the diagram in Figure 2, wherein the x-axis indicates the pH in the aqueous phase after phase separation and the y-axis indicates the ratio of the concentration of tungsten in the aqueous phase after phase separation to the concentration of tungsten in the aqueous phase of the first reactor. It can be seen from the results that the ratio of the concentration of tungsten in the aqueous phase after phase separation to the concentration of tungsten in the aqueous phase of the first reactor is generally less than 0.2 for a pH of 3.0 or less and decreases further when the pH value decreases. This means that the amount of tungsten in the aqueous phase of the first reactor is significantly higher than in the aqueous phase after phase separation, thus, when using the described method, tungsten is depleted from the aqueous phase.

[0150] Depending on the ethylenically unsaturated organic compound, the decomposition of the resulting product, e.g., the corresponding epoxide may be accelerated at a very acidic pH. Thus, adjustment of the pH within the described ranges might be advisable to combine a good depletion of tungsten from the aqueous phase with a minimal decomposition of the product. ce of the reactivation of the in step (iii) on the pH of the

[0151] The efficiency of the reactivation of the catalyst system in step (iii) was studied in relation to the pH of the aqueous phase in step (i). The results are shown in Table 2 below. The amount of inactive catalyst corresponds to the amount of tungsten in the organic phase after step (iii).

[0152] The amount of reactivated catalyst in step (iii), i.e., the efficiency of reactivation is determined by analyzing the tungsten concentration of the retentate after membrane filtration and the organic phase of step (iii) after hydrolysis using the following formula: reactivation [ with W (org. phase) being the amount of tungsten in the organic phase after the reactivation in step (iii) and W (retentate) being the amount of tungsten in the retentate after membrane filtration after step (ii) and before step (iii).

[0153] The lower the amount of tungsten in the organic phase after reactivation, the more effective was the reactivation of the catalyst. 202400119 Foreign Filing

[0154] 21

[0155] Table 2

[0156] It can be seen from the results that the pH in step (i) has an effect on the catalyst reactivation in step (iii). It is assumed that during the conversion in step (i) tungsten species are formed that are more difficult to reactivate if the pH is lower.

[0157] As can be seen from the results presented above, with the methods according to the present invention three aspects of the oxidation reaction can be controlled simultaneously, i.e., the concentration of the catalyst in the organic phase, the subsequent reactivation of the catalyst and the rate of the oxidation reaction. Therefore, the pH in step (i) may be adjusted so that it is low enough for depleting the catalyst system from the aqueous phase, but at the same time high enough to reactivate the catalyst system later in step (iii). Likewise, the peroxide concentration in step (i) may be adjusted so that it is at the end of the reaction (in the last reactor) low enough for depleting the catalyst system from the aqueous phase, but during the reaction (in the first reactors) high enough to achieve sufficient conversion from the ethy lenically unsaturated organic compound to the corresponding oxidation product. The exact adjustment of the pH value and the peroxide concentration within the described ranges according to the present method depends on the organic compound to be oxidized as well as the exact reaction conditions. Therefore, to achieve both sufficient depletion of the catalyst in step (i) and good reactivation of the catalyst in step (iii), the pH in step (i) may be adjusted within the range described herein above and may not necessarily correspond to the pH range of condition 1 (pH of 2.4 to 2.8) which resulted in the best reactivation of the catalyst in step (iii) as shown in Table 2 above, but may be lower (Conditions 2 and 3).

[0158] Comparative Example 1

[0159] The oxidation of the cyclic unsaturated C12 compound was carried out essentially as described above in Example 1 except that the amount of catalyst and hydrogen peroxide dosed into each reactor was varied to have productivity (conversion of CDEN introduced into the respective reactor > 50%) in each reactor, as it is described in the art, and the catalyst was not recycled into the first reactor. Table 3 shows the total conversion of CDEN in the course of the reaction, the partial conversion of CDEN in the individual reactors and the distribution of tungstate in the organic and aqueous phases during the course of the reaction. 202400119 Foreign Filing

[0160] 22

[0161] Table 3: Conversion of CDEN and distribution of tungstate

[0162] * partial conversion in the respective reactor

[0163] It can be seen that when carrying out the oxidation reaction in such a way that a significant conversion of the CDEN takes place in all three reactors(> 50% of the actual amount of CDEN introduced into the respective reactor), i.e. , each reactor has productivity, as it usually is the case in processes described in the art, the majority of the catalyst remains in the aqueous phase of the biphasic mixture present in the phase separation vessel. In contrast, when the last reactor has no significant productivity due to the lower amount of oxidant being present, as shown in Example 1 above, the catalyst is converted into a more hydrophobic catalytically inactive species which can be easily separated from the aqueous phase. Moreover, said separated inactive catalyst species can be reactivated and recycled into the oxidation reaction, as also shown in Example 1 above.

Claims

202400119 Foreign Filing23CLAIMS1 . A method for depleting a homogeneous catalyst system from an aqueous reaction phase and concentrating it into an organic phase, the catalyst system being employed in the oxidation of an ethy lenically unsaturated organic compound with a peroxide as oxidant in a reaction mixture comprising the aqueous phase and the organic phase, the method comprising the steps of(i) converting the catalyst into a more hydrophobic species by mixing the aqueous phase with the organic phase at a level of less than 0.05 wt.% of the oxidant, based on the total weight of the aqueous phase, and a pH of less than 3.0; and(ii) separating the aqueous phase from the organic phase.

2. The method according to claim 1 , wherein the reaction mixture further comprises a phase transfer reagent.

3. The method according to claim 1 or 2, wherein the catalyst system comprises at least one derivative of a transition metal of Group IVb, Vb and Vlb in its highest oxidation state.

4. The method according to any of the preceding claims, wherein in step (i) the pH is in the range of from more than 1 .5 to less than 3.0, preferably of from 1 .6 to 2.5.

5. The method according to any of the preceding claims, wherein after carrying out step (i) the aqueous phase comprises less than 10 wt.% of the transition metal, preferably less than 5 wt.%, more preferably less than 2.5 wt.% and even more preferably less than 2.0 wt.%, and the organic phase comprises more than 90 wt.% of the transition metal, preferably more than 95 wt.%, more preferably more than 97.5 wt.% and even more preferably more than 98.0 wt.%, based on the total weight of the transition metal in the reaction mixture.

6. A method for the oxidation of an ethylenically unsaturated organic compound comprising: oxidizing an ethylenically unsaturated organic compound with a peroxide as oxidant in a mixture comprising a homogeneous catalyst system, an organic phase comprising the ethylenically unsaturated organic compound, an acidic aqueous medium and a phase transfer reagent, wherein the homogeneous catalyst system comprises at least one derivative of a transition metal of Group IVb, Vb and Vlb in its highest oxidation state, to obtain a reaction mixture comprising an organic phase comprising the oxidation product of the ethylenically unsaturated organic compound and residual ethylenically unsaturated organic compound, an aqueous reaction phase, the catalyst system, the phase transfer reagent and residual peroxide; and depleting the homogeneous catalyst system from the aqueous reaction phase and concentrating it into the organic phase according to the method of any of the preceding claims.202400119 Foreign Filing247. The method according to any of the preceding claims, wherein the catalyst system further comprises phosphoric acid and / or a salt thereof.

8. The method according to any of the preceding claims, wherein the at least one derivative of the transition metal of Group IVb, Vb and Vlb is selected from a derivative of tungsten, molybdenum and vanadium, wherein the derivative preferably is selected from salts of H2WO4 or H2MOO4, or homo- or heteropolyoxometalates formed therefrom, more preferably from alkali or alkaline earth metal salts of H2WO4 or H2MOO4, or homo- or heteropolyoxometalates formed therefrom, and most preferably is Na2WO4 or a homo- or heteropolyoxometalate formed therefrom.

9. The method according to any of the preceding claims, wherein the oxidant is hydrogen peroxide.

10. The method according to any of claims 2 to 9, wherein the phase transfer reagent comprises a nitrogen atom, which is either permanently ionized or can be reversibly protonated and which contains more than 10 carbon atoms, preferably more than 15 carbon atoms.1 1 . The method according to any of the preceding claims, wherein the oxidation comprises an epoxidation of an olefin and the olefin has a solubility in water at 20 °C of no more than 1 wt.%, preferably of no more than 0.5 wt.%.

12. The method according to any of the preceding claims, wherein the reaction mixture is obtained in a process carried out in one or more stirred tank reactors, and preferably is obtained either in a continuous process using at least two reactors, more preferably three to five reactors, wherein the oxidant is only dosed into some of the reactors, wherein in the last reactor essentially no oxidation takes place; or in a batch process, wherein in the final phase no oxidant is added and essentially no oxidation takes place.

13. The method according claim 12, wherein in the continuous process a series of at least three stirred tank reactors is used and the concentration of peroxide in the aqueous phase decreases in the series of reactors and preferably is in the range of from 0.7 to 2.0 wt.% in the first reactor and less than 0.05 wt.% in the last reactor, each based on the total weight of the aqueous phase; or in the batch process the concentration of peroxide in the aqueous phase decreases in the course of the oxidation reaction and is preferably in the range of from 0.7 to 2.0 wt.% during the first phase of the oxidation reaction, less than 0.1 wt.% upon completing the oxidation reaction, and less than 0.05 wt.% after separating the aqueous phase from the organic phase in step (ii), each based on the total weight of the aqueous phase.202400119 Foreign Filing2514. An organic phase comprising an olefin and an oxidation product thereof in a weight ratio of lower than 3:97 and either 2000 to 2500 ppm (option 1) or 15000 to 30000 ppm (option 2) of a transition metal of Group IVb, Vb and Vlb in its highest oxidation state from a homogeneous catalyst system for the oxidation of the olefin, based on the total weight of the organic phase.

15. A biphasic mixture comprising either the organic phase of option 1 of claim 14 and an acidic aqueous phase having a pH of less than 3.0, an amount of peroxide of less than 0.05 wt.% and less than 200 ppm of the transition metal, based on the total weight of the aqueous phase; or - the organic phase of option 2 of claim 14 and an aqueous base being essentially free of the transition metal and peroxide.

16. An aqueous phase obtained by separating the aqueous phase of the biphasic mixture according to claim 15 from the organic phase of option 1 , wherein the aqueous phase comprises 5 ppm or more and less than 200 ppm of the transition metal, based on the total weight of the aqueous phase.

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