Method for producing a carboxylic acid

Abstract

The invention relates to a method for producing a carboxylic acid, which comprises following reaction steps: a) providing an alicyclic ketone, an alicyclic alcohol or a mixture of an alicyclic ketone and an alicyclic alcohol, b) reacting the alicyclic alcohol and / or the alicyclic ketone from step a) with a peroxide or peroxide providing reagent in the presence of a catalyst to an oxidation product, c) separating the oxidation product from the catalyst, wherein the catalyst comprises a peroxo-polyoxometalate, wherein the peroxo-polyoxometalate comprising a repeating unit selected from A, A' or B, wherein the units A, A' and B consist of formula (I), wherein M is a metal ion selected from a group of Zr, Hf, Rf, Ce, Th, Nb, Ta, Re and any transition metal ion with a coordination number > 8, wherein the repeating units A, A' and / or B can be fused directly to each other via a common metal atom M or linked via an oxo, hydroxo or hydroperoxo group connecting two metal atoms M of two repeating units A, A' and / or B, wherein the peroxo-polyoxometalate comprises m repeating units A, n repeating units B and o repeating units A', wherein n, m and o are integer numbers selected from 0 to 20, wherein m, n and o cannot simultaneously be equal to 0, wherein M is coordinated to polyoxometalate (POM), wherein the coordination number of each M is at least 8, wherein the peroxo-polyoxometalate comprises a ligand based on mono-, di-, tri- lacunary Keggin or Wells-Dawson ions or wheels and its derivatives, wherein the peroxo-polyoxometalate has a linear, cyclic or spherical structure.

Description

[0001]202300115 1 METHOD FOR PRODUCING A CARBOXYLIC ACID TECHNICAL FIELD OF THE INVENTION The present invention relates to a method for producing a carboxylic acid according to claim 1. BACKGROUND OF THE INVENTION Carboxylic acids are important chemical raw materials, for example adipic acid is mainly used as a raw material for the production of synthetic fibers, polyester foams, synthetic resins and the production of esters. The traditional adipic acid production process mainly uses nitric acid oxidation method to oxidize cyclohexanol and mixtures of cyclohexanol and cyclohexanone - called KA oil - with nitric acid to obtain adipic acid. The production process of carboxylic acids using nitric acid is a multi-stage, cost intensive and polluting process using homogeneous catalysts and environmentally harmful oxidizing agents. In the reaction of alicyclic alcohols or alicyclic ketones with nitric acid, nitrogen oxides are formed as by-products, especially nitrous oxide (N2O), which is a very harmful greenhouse gas. Although it can be removed from the product stream and converted into harmless products, this requires additional and energy-intensive process steps. One of the current research directions is to replace nitric acid with a clean oxidant. Hydrogen peroxide is a powerful oxidant, and the only by-product of its own reaction is water. With hydrogen peroxide as the oxidant, it is necessary to convert alicyclic alcohols or alicyclic ketones to carboxylic acid under the action of a catalyst, and the used catalysts are mostly tungsten- containing compounds such as tungstate and phosphotungstic acid. When tungstate or phosphotungstic acid is used as a catalyst directly, the recycling of the catalyst is very difficult due to the existence of a "pseudo-liquid phase" behavior. This results in a product, which contains more impurities. CN 108262073 A discloses a metal organic skeleton-supported phosphotungstic acid catalyst for the synthesis of adipic acid by oxidation of cyclohexanol and cyclohexanone. However, using the described phosphotungstic acid catalyst only a small conversion rate to adipic acid can be obtained. Also, EP 1544190 B1 describes a method for producing a carboxylic acid using hydrogen peroxide as oxidant in the presence of a catalyst containing a tungsten compound, which forms a tungstic acid anion in water. However, this method and catalyst again only produce small yields of carboxylic acids. Polyoxometalates (POMs) are known in industry for several applications, for example as acids or oxidation catalysts. 202300115 2 Catalysts based on polyoxometalates (POMs) containing peroxo-groups (peroxo-POMs) are of special interest in hydrogen peroxide-assisted oxidation catalysis. POMs are discrete, anionic metal-oxo clusters comprising metal ions in high oxidation states. Wherein the metal ion is selected from the early transition metals. However, the known peroxo-POM-catalysts are not effectively oxidizing alicyclic alkanols, alicyclic alkanones or alicyclic alkenones producing carboxylic acids including dicarboxylic acids. It was therefore an object of the present invention to provide a group of reactive peroxo- polyoxometalates, which can be used as catalysts with high catalytic activity. In addition, these catalysts based on the group of peroxo-polyoxometalates shall enable oxidation of alicyclic organic compounds using hydrogen peroxide. DESCRIPTION OF THE INVENTION After thorough investigation, the inventors of the present invention have surprisingly found a method for producing a carboxylic acid, which comprises following reaction steps: a) providing an alicyclic ketone, an alicyclic alcohol or a mixture of an alicyclic ketone and an alicyclic alcohol, b) reacting the alicyclic alcohol and / or the alicyclic ketone from step a) with a peroxide or peroxide providing reagent in the presence of a catalyst to an oxidation product, c) separating the oxidation product from the catalyst, wherein the catalyst comprises a peroxo-polyoxometalate, wherein the peroxo-polyoxometalate comprising a repeating unit selected from A, A’ or B, wherein the units A, A’ and B consist of the following formula: wherein M is a metal ion selected from a group of Zr, Hf, Rf, Ce, Th, Nb, Ta, Re and any transition metal ion with a coordination number ≥ 8, wherein the repeating units A, A’ and / or B can be fused directly to each other via a common metal atom M or linked via an oxo, hydroxo or hydroperoxo group connecting two metal atoms M of two repeating units A, A’ and / or B, wherein the peroxo-polyoxometalate comprises m repeating units A, n repeating units B and o repeating units A’, wherein n, m and o are integer numbers selected from 0 to 20, wherein m, n and o cannot simultaneously be equal to 0, 202300115 3 wherein M is coordinated to polyoxometalate (POM), wherein the coordination number of each M is at least 8, wherein the peroxo-polyoxometalate comprises a ligand based on mono-, di-, tri- lacunary Keggin or Wells-Dawson ions or wheels, such as Contant-Tézé wheel ions, and its derivatives, wherein the peroxo-polyoxometalate has a linear, cyclic or spherical structure. Especially, M is coordinated to peroxo-polyoxometalate through its lacunary site. The peroxo- polyoxometalate can be mono-, di-, tri- lacunary Keggin or Wells-Dawson ions or cyclic wheels and its derivatives. Keggin ions are based on an anion of the formula [YZ12O40]r-, wherein for example Y is selected from P, As, Ge, Si and mixtures thereof and wherein Z is selected from W, Mo and mixtures thereof. Wells-Dawson ions are based on an anion of the formula [Y2Z18O62]r-, wherein Y is for example selected from P, As, Ge, Si and mixtures thereof and wherein Z is selected from W, Mo and mixtures thereof. A Contant-Tézé wheel ion is based on an anion of the formula [Y8Z48O184]r-,wherein Y is for example selected from P, As, Ge, Si and mixtures thereof and wherein Z is selected from W, Mo and mixtures thereof. These named ions represent ligands for coordination of metal ions forming peroxo-polyoxometalates only if defects are present in the original structure. For a mono-lacunary coordination, one Z-atom and one O-atom (ZO depleted) are missing. A di-lacunary coordinated peroxo-polyoxometalate will be formed comprising an anion with two missing Z-atoms and three missing O-atoms (Z2O3 depleted) in comparison to the original full anion structure. Regarding the tri-lacunary coordinated peroxo-polyoxometalate three Z-atoms and six O-atoms (Z3O6 depleted) are missing forming defects, which provides a powerful ligand. These peroxo-polyoxometalates provide active catalysts, which catalyze oxidation reactions, especially from alicyclic alcohols and / or alicyclic ketones to carboxylic acids. Preferably, the method steps are performed subsequently in the named order. Preferably, the peroxo-polyoxometalate comprises following numbers of repeating units: a) m = 0, n = 1, o = 0, b) m = 4, n = 4, o = 0, c) (m + o) = 4, n = 0, wherein m and o are an integer number of 0 to 4, d) m = 17 or 18, n = 0, o = 0, e) (m + o) = 17 or 18, n = 0 wherein m and o are an integer number of 0 to 18 f) m = 1, n = 0, o = 0, or g) m = 0, n = 0, o = 1. In an optional embodiment, the peroxo-polyoxometalate comprises one of the following structures: ^ m = 0, n = 1, o = 0, wherein M is coordinated by a monolacunary Wells-Dawson ion, ^ m = 4, n = 4, o = 0 or (m+o) = 4, n = 4, wherein the repeating units A and B are alternately fused to each other and wherein the peroxo-polyoxometalate comprises a dilacunary Wells-Dawson ion, 202300115 4 ^ m = 17 or 18, n = 0, o = 0 or (m+o) = 17 or 18, n = 0 wherein the repeating units are fused to each other and wherein the peroxo-polyoxometalate comprises a trilacunary Keggin ion, wherein the repeating units especially form a spherical structure, ^ m = 1, n = 0, o = 0 or (m+o) = 1, n = 0 wherein the peroxo-polyoxometalate comprises a dilacunary Wells-Dawson ion, especially the repeating unit forms a linear structure. Optionally, in this structure the peroxo-polyoxometalate forms a sandwich-like structure, which means that A has a dilacunary Wells-Dawson ion on either side making A a sandwich. Preferably, the peroxo-polyoxometalate comprises one of the anions selected from the group of: ^ [M2(O2)2(Y2Z17O61)2]16-, wherein M is selected from Zr, Hf and Ce and Y is selected from P and As and Z is selected from W and Mo, ^ [M8(O2)12(Y2Z16O59)4]40-, wherein M is selected from Ce, Zr and Hf and Y is selected from P and As and Z is selected from W and Mo, ^ [M12(O2)18(O)4(YZ9O34)4]36-, wherein M is selected from Ce, Zr and Hf, preferably M is Ce, and Y is selected from Ge and Si and Z is selected from W and Mo, wherein [M12(O2)18(O)4(YZ9O34)4]36-optionally can occur as single or multiple peroxo-depleted structures, wherein one or more O22-is replaced each by mono- or di- OH-, ^ [M12(O2)17(OH)2(O)4(YZ9O34)4]36-, Ce, Zr and Hf, preferably M is Ce, and Y is selected from Ge and Si and Z is selected from W and Mo, wherein [M12(O2)17(OH)2(O)4(YZ9O34)4]36-optionally can occur as single or multiple peroxo-depleted structures, wherein one or more O22-is replaced each by mono- or di- OH-, ^ [M2(O2)(Y2Z16O59)2]18-, wherein M is selected from Ce, Zr and Hf and Y is selected from P and As and Z is selected from W and Mo. If the peroxo-polyoxometalate comprises more than one M-atom, it could be also the case that different metals are in one peroxo-polyoxometalate. This belongs also to Y and Z, this is due to the fact that certain elements are interchangeable in the synthesis of the peroxo-polyoxometalates. Optionally, [M12(O2)18(O)4(YZ9O34)4]36-and [M12(O2)17(OH)2(O)4(YZ9O34)4]36-,for example Na34K2[Ce12(O2)17(OH)2O4(SiW9O34)4], and Na34K2[Ce12(O2)18O4(GeW9O34)4], can have single or multiple peroxo-depleted structures, wherein one or more O22-is each replaced by mono- or di- OH- , wherein the structure with 0 O22-and 24 OH- being the fully peroxo-depleted structure with various intermediates possible in between, which can be referred to as intermediate peroxo-species or subsequent peroxo-species as termed in Duncan, D. C.; Chambers, R. C.; Hecht, E.; Hill C. L. Mechanism and Dynamics in the H3[PW12O40]-Catalyzed Selective Epoxidation of Terminal Olefins by H2O2. Formation, Reactivity, and Stability of {PO4[WO(O2)2]4}3-J. Am. Chem. Soc.1995, 117, 681-691. Especially, the peroxo-polyoxometalate comprises an anion selected from the group of: [Zr2(O2)2(P2W17O61)2]16-, [Hf2(O2)2(P2W17O61)2]16-, [Zr2(O2)2(As2W17O61)2]16-, [Hf2(O2)2(As2W17O61)2]16-, 202300115 5 [Ce12(O2)17(OH)2O4(SiW9O34)4]36-, [Ce12(O2)18O4(GeW9O34)4]36-, [Ce2(O2)(P2W16O59)2]18-or [Ce8(O2)12(P2W16O59)4]40-. Optionally, the peroxo-polyoxometalates comprise a cation selected from the group consisting of potassium, sodium, lithium, hydrogen, ammonium, alkyl ammonium, tetra-n-butyl ammonium, alkyl phosphonium or mixtures thereof. Optionally, the peroxo- polyoxometalate is selected from the group consisting of K16[Zr2(O2)2(P2W17O61)2]; K16[Hf2(O2)2(P2W17O61)2]; K16[Zr2(O2)2(As2W17O61)2]; K16[Hf2(O2)2(As2W17O61)2]; TBA10H5K[Zr2(O2)2(P2W17O61)2]; TBA11H5[Hf2(O2)2(P2W17O61)2]; Na34K2[Ce12(O2)17(OH)2O4(SiW9O34)4], Na34K2[Ce12(O2)18O4(GeW9O34)4], K12Li4Na2[Ce2(O2)(P2W16O59)2] and Na32(NH4)8[Ce8(O2)12(P2W16O59)4]. These peroxo-polyoxometalates comprise a high catalytic activity, especially in oxidation reactions using a peroxide as oxidant. Optionally, following structures of peroxo-polyoxometalates are excluded from the claimed invention: a) m = 0, n = 1, o = 0, wherein the peroxo-polyoxometalate comprises monolacunary Keggin ions and forms a linear structure. These peroxo-polyoxometalates especially comprise an anion formula of [M2(O2)2(YW11O39)2]12-, wherein M is Zr and / or Hf and Y is selected from Ge, Si, P. These structures are already published in “Mal, S. S.; Nsouli, N. H.; Carraro, M.; Sartorel, A.; Scorrano, G.; Oelrich, H.; Walder, L.; Bonchio, M.; Kortz, U. Peroxo-Zr / Hf- Containing Undecatungstosilicates and -Germanates. Inorg. Chem.2009, 49, 7–9.” and “Aoto, H.; Matsui, K.; Sakai, Y.; Kuchizi, T.; Sekiya, H.; Osada, H.; Yoshida, T.; Matsunaga, S.; Nomiya, K. Zirconium(IV)- and Hafnium(IV)-Containing Polyoxometalates as Oxidation Precatalysts: Homogeneous Catalytic Epoxidation of Cyclooctene by Hydrogen Peroxide. J. Mol. Catal. A: Chem.2014, 394, 224–231.” b) m = 0, n = 0, o = 6 (A’ with X = OH), wherein the repeating units are fused to each other together with dilacunary Keggin peroxo-polyoxometalates forming a cyclic structure of repeating units. These peroxo-polyoxometalates especially comprise an anion formula of [M6(O2)6(OH)6(YW10O36)3]18- -, wherein M is Zr and / or Hf and Y is Si. These structures are already published in “B. Bassil, B. S.; Mal, S. S.; Dickman, M. H.; Kortz, U.; Oelrich, H.; Walder, L.6-Peroxo-6-Zirconium Crown and Its Hafnium Analogue Embedded in a Triangular Polyanion: [M6(O2)6(OH)6(γ-SiW10O36)3]18−(M = Zr, Hf). J. Am. Chem. Soc.2008, 130, 6696–6697.” c) m = 3, n = 3, o = 0, wherein the repeating units are fused to each other and coordinated to form a dilacunary Keggin peroxo-polyoxometalate, wherein the repeating units form a cyclic structure. These peroxo-polyoxometalates especially comprise an anion formula of [Ce6(O2)9(GeW10O37)3]24–. This structure was already published in Qasim, H. M.; Ayass, W. W.; Donfack, P.; Mougharbel, A. S.; Bhattacharya, S.; Nisar, T.; Balster, T.; Solé-Daura, A.; Römer, I.; Goura, J.; Materny, A.; Wagner, V.; Poblet, J. M.; Bassil, B. S.; Kortz, U. Peroxo- 202300115 6 Cerium(IV)-Containing Polyoxometalates: [CeIV6(O2)9(GeW10O37)3]24–, a Recyclable Homogeneous Oxidation Catalyst. Inorg. Chem.2019, 58, 11300-11307. However, these excluded structures are less or even not catalytically active in comparison to the inventive structures. The amount of catalyst is not particularly limited, preferably it is selected from the range of usually 0.0001 to 20% by mol, more preferably 0.01 to 10% by mol based on the amount of alicyclic alcohol and / or alicyclic ketone. Although the catalyst to be used in the method comprises the claimed features, an auxiliary catalyst can be used, such as phosphoric acid, if necessary. Optionally, the mixture of b) can comprise further substances, such as stabilizers, which could be already comprised in the used peroxide. The mixture of method step b), comprising the alicyclic alcohol and / or the alicyclic ketone from step a) and a peroxide or peroxide providing reagent in the presence of a catalyst is called here reaction mixture. During reaction of the compounds the reaction mixture could also comprise the oxidation product, such as the corresponding carboxylic acid. In an optional embodiment the reaction mixture can comprise a solvent. Optionally, the solvent is a polar solvent such as water, acetic acid or iso-butyl alcohol. In an optional embodiment, the peroxo-polyoxometalate is fixed to a solid, which can be for example a silica material, preferably a mesoporous silica material. This provides a catalyst, which can be used as a heterogeneous catalyst in the reaction mixtures, even as a heterogeneous catalyst in mono or biphasic solutions. This procedure allows a good separation of the catalyst after completion of the reaction. The catalyst can be separated for example by filtration or centrifugation and used again for the next batch. In addition, such a heterogeneous catalyst, fixed to a solid can be used in continuous reaction procedures using for example a catalyst fixed bed. The mesoporous silica material fixes the catalyst safely to the solid and provides still good catalytic activity. Optionally, the solid is a (3-aminopropyl)triethoxysilane modified mesoporous silica support. This material enables a good heterogeneous catalyst. In an optional embodiment, the catalyst is recycled after step c) into step b). Alternatively or in addition, also the starting materials, such as the alicyclic alcohol, the alicyclic ketone, the peroxide 202300115 7 or a peroxide producing reagent and / or a potentially solvent can be recycled after separation step c). The addition of fresh starting material to the recycled starting material is also possible. Optionally, the reaction mixture comprising the alicyclic alcohol and / or alicyclic ketone, peroxide or peroxide providing reagent and catalyst is mixed. This could be for example done by stirring. Alternatively, if the catalyst is fixed to a fixed bed, the mixture of alicyclic alcohol and / or alicyclic ketone and peroxide is passed over the fixed bed and mixed during the flow of the mixture. In an optional embodiment the reaction is carried out at a temperature within the range of usually 30 to 120° C., preferably 30 to 100° C. The reaction pressure may be any of ambient pressure, pressurization and reduced pressure, but it is preferable to carry out the reaction under ambient pressure or with increased pressure during microwave reaction. Optionally, the catalyst and the peroxide or peroxide providing reagent is mixed prior the addition of the alicyclic ketone, the alicyclic alcohol or the mixture of an alicyclic ketone and an alicyclic alcohol to form the reaction mixture. Preferably, the peroxide, which reacts as an oxidizing agent, is selected from the group of aqueous hydrogen peroxide, peracetic acid, persulfate, any other active oxygen providing compound as peroxide providing reagent and mixtures thereof. These peroxides are highly active and allow a good yield of carboxylic acids obtained by the oxidation reaction method. Optionally, the used peroxide can be used in the form of an aqueous solution, such as aqueous hydrogen peroxide. The concentration of the aqueous peroxide is not particularly limited, because the oxidation reaction of alicyclic alcohol or alicyclic ketone proceeds in response to its concentration. Preferably the concentration of aqueous peroxide, especially aqueous hydrogen peroxide, is selected within the range of 1 to 80% by weight, preferably 30 to 60% by weight. In addition, the amount of the peroxide, especially aqueous hydrogen peroxide, is not limited, too, but it is selected within the range of 3.0 to 30.0 equivalents, preferably 3.3 to 8.0 equivalents, based on the alicyclic alcohol or alicyclic ketone. In an optional embodiment, the process is performed continuously. This allows the production of the corresponding carboxylic acid in industrial scale and high amounts. For example, the catalyst could be fixed to a fixed bed and mixture of a) is mixed with hydrogen peroxide and passed through fixed bed reactor in step b) before the mixture is separated from the fixed bed of catalyst in step c) of the production method. 202300115 8 Optionally, the mixture of step b), also called reaction mixture, which comprises an alicyclic ketone and / or alicyclic alcohol, hydrogen peroxide and the catalyst further comprises a solvent. Optionally, the reaction mixture is homogenous, wherein the solvent is nonpolar, or alternatively the mixture is heterogeneous, wherein the solvent is polar, for example water from aqueous hydrogen peroxide. The described peroxo-polyoxometalates catalysts catalyze oxidation reactions of named organic compounds using peroxide or a peroxide providing reagent as an oxidant, especially hydrogen peroxide. In an optional embodiment, the alicyclic alcohol is a compound represented by the following formula (1) or the alicyclic ketone is a compound represented by the following formula (2): wherein q is an integer of 1 to 18; and R1, R2, R3and R4, are the same or different and each is selected from the group of hydrogen atom, hydroxyl group, halogen atom, carboxyl group, alkyl group, alkoxy group, cycloalkyl group, an aryl group, aralkyl group, acyl group or an acyloxy group, or R1and R2, R1and R3, R1and R4, R2and R4or R3and R4may be taken together to form a carbon ring, which may be substituted with an alkyl group having from 1 to 4 carbon atoms, an alkoxy group having from 1 to 4 carbon atoms, an cycloalkyl group having 3 to 7 carbon atoms, an aryl group , an aralkyl group, a carboxyl group or a halogen atom. Examples of the alicyclic alcohol represented by formula (1) include cyclobutanol, cyclopentanol, cyclohexanol, cycloheptanol, cyclooctanol, cyclononanol, cyclodecanol, cycloundecanol, cyclododecanol, cyclotridecanol, cyclotetradecanol, cyclopentadecanol, cyclohexadecanol, cycloheptadecanol, cyclooctadecanol, cyclononadecanol, cycloicosanol, cycloheneicosanol, 1- methylcyclopentanol, 2-methylcyclopentanol, 1,2-dimethylcyclopentanol, 1,3- 202300115 9 dimethylcyclopentanol, 1,4-dimethylcyclopentanol, 2,3-dimethylcyclopentanol, 1,2,3- trimethylcyclopentanol, 1,2,4-trimethylcyclopentanol, 1,2,3,4-tetramethylcyclopentanol, 1- methylcyclohexanol, 2-methylcyclohexanol, 3-methylcyclohexanol, 1,2-dimethylcyclohexanol, 1,3- dimethylcyclohexanol, 1,4-dimethylcyclohexanol, 1, 5-dimethylcyclohexanol, 2,3- dimethylcyclohexanol, 2,4-dimethylcyclohexanol, 1,2,3-trimethylcyclohexanol, 1,2,4- trimethylcyclohexanol, 1,2,5-trimethylcyclohexanol, 1,3,4-trimethylcyclohexanol, 1,3,5- trimethylcyclohexanol, 2,3,4-trimethylcyclohexanol, 1,2,3,4-tetramethylcyclohexanol, 1,2,3,5- tetramethylcyclohexanol, 1,2,4, 5-tetramethylcyclohexanol,1,2,3,4,5-pentamethylcyclohexanol, 1- methylcycloheptanol, 1-methylcyclooctanol, 1-methylcyclononanol, 1-methylcyclodecanol, 1- methylcycloundecanol, 1-methylcyclododecanol, 1-methylcyclotridecanol, 1- methylcyclotetradecanol, 1-methylcyclopentadecanol, 1-methylcyclohexadecanol, 1- methylcycloheptadecanol, 1-methylcyclooctadecanol, 1-methylcyclononadecanol, 1- methylcycloicosanol, 1-methylcycloheneicosanol, 1-phenylcyclohexanol, 1-benzylcyclohexanol, 1,2-cyclohexanediol, 1-chlorocyclopentanol, 1-bromocyclopentanol 1-chlorocyclohexanol, 1- bromocyclohexanol, cyclopentanol-1-carboxylic acid, cyclohexanol-1-carboxylic acid,1- acetylcyclopentanol, 1-acetylcyclohexanol. The alcohol preferably used as an alicyclic alcohol according to formula (1) is cyclopentanol or cyclohexanol and derivates thereof. Examples of the alicyclic ketones represented by formula (2) include cyclobutanone, cyclopentanone, cyclohexanone, cycloheptanone, cyclooctanone, cyclononanone, cyclodecanone, cycloundecanone, cyclododecanone, cyclotridecanone, cyclotetradecanone, cyclopentadecanone, cyclohexadecanone, cycloheptadecanone, cyclooctadecanone, cyclononadecanone, cycloicosanone, cycloheneicosanone, 1-methylcyclopentanone, 2-methylcyclopentanone, 1,2- dimethylcyclopentanone, 1,3-dimethylcyclopentanone, 1,4-dimethylcyclopentanone, 2,3- dimethylcyclopentanone, 1,2,3-trimethylcyclopentanone, 1,2, 4-trimethylcyclopentanone, 1,2,3,4- tetramethylcyclopentanone, 1-methylcyclohexanone, 2-methylcyclohexanone, 3- methylcyclohexanone, 1,2-dimethylcyclohexanone, 1,3-dimethylcyclohexanone, 1,4- dimethylcyclohexanone, 1,5-dimethylcyclohexanone, 2,3-dimethylcyclohexanone, 2,4- dimethylcyclohexanone, 1,2,3-trimethylcyclohexanone, 1,2,4-trimethylcyclohexanone, 1,2,5- trimethylcyclohexanone, 1,3,4-trimethylcyclohexanone, 1,3,5-trimethylcyclohexanone, 2,3 ,4- trimethylcyclohexanone, 1,2,3,4-tetramethylcyclohexanone, 1,2,3,5-tetramethylcyclohexanone, 1,2,4,5-tetramethylcyclohexanone, 1,2,3,4,5- pentamethylcyclohexanone, 1-methycycloheptanone, 1-methylcyclooctanone, 1-methylcyclononanone, 1-methylcyclodecanone, 1- methylcycloundecanone, 1-methylcyclododecanone, 1-methylcyclotridecanone, 1- methylcyclotetradecanone, 1-methylcyclopentadecanone, 1-methylcyclohexadecanone, 1- methylcycloheptadecanone, 1-methylcyclooctadecanone, 1-methylcyclononadecanone, 1- methylcycloicosanone, 1-methylcycloheneicosanone, 1-phenylcyclohexanone, 1- benzylcyclohexanone, 1-hydroxycyclohexanone, 1,2-cyclohexanedione, 1-chlorocyclopentanone, 1-bromocyclopentanone, 1-chlorocyclohexanone, 1-bromocyclohexanone, cyclopentanone-1- carboxylic acid, cyclohexanone-1-carboxylic acid, 1-acetylcyclopentanone, 1-acetylcyclohexanone. The ketone preferably representing formula 1 is cyclopentenone, cyclohexanone, cycloheptanone, cyclooctenone and derivatives thereof. 202300115 10 Preferably, the obtained carboxylic acid obtained using the described production method is a dicarboxylic acid represented by the following formula (3): (3) wherein q is an integer of 1 to 18; and R1, R2and R3, are the same or different and each is selected from the group of hydrogen atom, hydroxyl group, halogen atom, carboxyl group, alkyl group, alkoxy group, cycloalkyl group, an aryl group, aralkyl group, acyl group or an acyloxy group, or R1and R2, R1and R3, R2and R3may be taken together to form a carbon ring, which may be substituted with an alkyl group having from 1 to 4 carbon atoms, an alkoxy group having from 1 to 4 carbon atoms, an cycloalkyl group having 3 to 7 carbon atoms, an aryl group , an aralkyl group, a carboxyl group or a halogen atom. A dicarboxylic acid according to formula (3) can be obtained from an above-described alicyclic alcohol of formula (1) or an above-described alicyclic ketone of formula (2) wherein R4is a hydrogen atom, a hydroxyl group or a halogen atom. Optionally, the obtained dicarboxylic acid is glutaric acid or adipic acid or derivatives thereof. Optionally, when the R4in the above-described alicyclic alcohol according to formula (1) or the above-described alicyclic ketone according to formula (2) is a group other than a hydrogen atom, a hydroxyl group or a halogen atom, it is possible to obtain keto-carboxylic acid represented by the following formula (4): (4) wherein q is an integer of 1 to 18; and R1, R2and R3are the same or different and each is selected from the group of hydrogen atom, hydroxyl group, halogen atom, carboxyl group, alkyl group, alkoxy group, cycloalkyl group, an aryl group, aralkyl group, acyl group or an acyloxy group, and R4represents a carboxyl group, an alkyl group, optionally having from 1 to 4 carbon atoms, an alkoxy group, optionally having from 1 to 4 carbon atoms, a cycloalkyl group, optionally having from 3 to 7 carbon atoms, an aryl group, an aralkyl group, an acyl group or an acyloxy group, or R1and R2, R1and R3, R1and R4, R2and R4or R3and R4may be taken together to form a carbon ring, which may 202300115 11 be substituted with an alkyl group having from 1 to 4 carbon atoms, an alkoxy group having from 1 to 4 carbon atoms, an cycloalkyl group having 3 to 7 carbon atoms, an aryl group , an aralkyl group, a carboxyl group or a halogen atom. Examples of the obtainable carboxylic acids using the method of the present invention include succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecanedioic acid, brassylic acid, tridecanedioic acid, tetradecanedioic acid, pentadecanedioic acid, hexadecanedioic acid, heptadecanedioic acid, octadecanedioic acid, nonadecanedioic acid, icosanedioic acid, heneicosanedionic acid, 5-oxohexanoic acid, 2-methylglutaric acid, 4-methyl-5- oxohexanoic acid, 3-methyl-5-oxohexanoic acid, 2-methyl-5-oxohexanoic acid, 2,3-dimethylglutaric acid, 3,4-dimethyl-5-oxohexanoic acid, 2,4-dimethy 1-5-oxohexanoic acid, 2,3-dimethy 1-5- oxohexanoic acid, 2,3,4-trimethyl-5-oxohexanoic acid, 6-oxoheptanoic acid, 2-methyladipic acid, 3- methyladipic acid, 5-methyl-6-oxoheptanoic acid, 4-methyl-6-oxoheptanoic acid, 3n-methyl-6- oxoheptanoic acid, 2-methyl-6-oxoheptanoic acid, 2,3-dimethyladipic acid, 2,4-dimethyladipic acid, 4,5-dimethy-1-6-oxoheptanoi c acid, 3 ,5-dimethy 1-6-oxoheptanoic acid, 2,5-dimethyl-6- oxoheptanoic acid, 2,3-dimethyl-6-oxoheptanoic acid, 3,4-dimethyl-6-oxoheptanoic acid, 2,4- dimethyl-6-oxoheptanoic acid, 2,3,4-trimethyladipic acid, 3,4,5-trimethyl-6-oxoheptanoic acid, 2,4,5- trimethyl-6-oxoheptanoic acid, 2,3,4-trimethyl-6-oxoheptanoic acid, 2,3,5-trimethyl-6-oxoheptanoic acid, 2,3,4,5-tetramethyl-6-oxoheptanoic acid, 7-oxooctanoic acid, 8-oxononanoic acid, 9- oxodecanoic acid, 10-oxoundecanoic acid, 11-oxodode-canoic acid, 12-oxotridecanoic acid, 13- oxotetradecanoic acid, 14-oxopentadecanoic acid, 15-oxohexadecanoic acid, 16- oxoheptadecanoic acid, 17-oxooctadecanoic acid, 18-oxononadecanoic acid, 19-oxoicosanoic acid, 20-oxoheneicosanoic acid, 21-oxodocosanoic acid, 6-phenyl-6-oxohexanoic acid, 7-phenyl-6- oxoheptanoic acid and derivatives. Preferably, the carboxylic acid produced by the described method is selected from the group of glutaric acid, adipic acid or derivates thereof. According to the method of the present invention, the oxidation product, which is a carboxylic acid, can be obtained in high yield and high selectivity after completion of the described oxidation reaction. Separation of the oxidation product from the catalyst can be done by optionally concentrating the mixed solution containing the formed carboxylic acid, alternatively or additionally separating and purifying the oxidation product by usual methods such as recrystallization, distillation, and sublimation. The present invention will now be explained in more detail with reference to examples. 202300115 12 EXPERIMENTAL PART The invention is further illustrated in detail hereinafter with reference to examples and comparative examples, without any intention to limit the scope of the present invention. Abbreviations K-ZrP K16[Zr2(O2)2(P2W17O61)2]·23H2O K-HfP K16[Hf2(O2)2(P2W17O61)2]·26H2O K-ZrAs K16[Zr2(O2)2(As2W17O61)2]·26H2O·KCl K-HfAs K16[Hf2(O2)2(As2W17O61)2]·26H2O K-As2W17 K10[α2-As2W17O61]·21H2O K-P2W17 K10[α2-P2W17O61]·20H2O Na-P2W15 Na12[α-P2W15O56]·24H2O K-P2W12 K12[α-H2P2W12O48]·24H2O Na-SiW9 Na10[α-SiW9O34]·xH2O Na-GeW9 Na10[α-GeW9O34]·18H2O KLiNa-Ce2P2W16 K12Li4Na2[CeIV2(O2)(P2W16O59)2]·26H2O NaNH4-Ce8P2W16 Na32(NH4)8[CeIV8(O2)12(P2W16O59)4]·113H2O NaK-Ce12SiW9 Na34K2[CeIV12(O2)17(OH)2(O)4(SiW9O34)4]·43H2O NaK-Ce12GeW9 Na34K2[CeIV12(O2)18(O)4(SiW9O34)4]·79H2O POM polyoxometalate TBA tetra-n-butylammonium TBA-ZrP TBA10H5K[Zr2(O2)2(P2W17O61)2] TBA-HfP TBA11H5[Hf2(O2)2(P2W17O61)2] SBA15 Santa Barbara Amorphous 15 apts (3-aminopropyl) triethoxysilane ZrP-apts-SBA15 [Zr2(O2)2(P2W17O61)2]16-supported on apts modified SBA15 Methods and Examples The hydrated potassium salts of the monolacunary Wells-Dawson precursors K10[α2- P2W17O61]·20H2O (K-P2W17) and K10[α2-As2W17O61]·21H2O (K-As2W17), trilacunary Wells-Dawson precursor Na12[α-P2W15O56]·24H2O (Na-P2W15), hexalacunary Wells-Dawson precursor K12[α- H2P2W12O48]·24H2O (K-P2W12) and trilacunary Keggin precursors Na10[α-SiW9O34]·xH2O (Na-SiW9) and Na10[α-GeW9O34]·18H2O (Na-GeW9) were synthesized according to the published procedures – published in a) Ginsberg, A. P. Inorganic Syntheses, Vol.27. and b) Contant, R.; Thouvenot, R. Hétéropolyanions de type Dawson.2. Synthèses de polyoxotungstoarsénates lacunaires dérivant de l'octadécatungstodiarsénate. Étude structurale par RMN du tungstène-183 des octadéca(molybdotungstovanado)diarsénates apparentés. Can. J. Chem.1991, 69, 1498-1506. All other chemicals were purchased and used without further purification. Cyclohexanol (99% from Riedel-de Haën), Cyclohexanone (>99.5% from Sigma Aldrich), Cyclohexene (>99% from Fluka Chemicals), H2O2 (33% w / v from AppliChem) were used as purchased. Deionized water has been used. 202300115 13 NMR Analysis.13C NMR was used to analyze the catalytic products. The chemical shift values are reported with respect to TMS in aqueous solution as reference. All the measurements were single- pulse proton decoupled with an acquisition time of 0.744 s and relaxation delay set to 10 s. GC-analyses. Performed on a Shimadzu GC 2010 equipped with a FID detector. Infrared Spectroscopy. The FTIR spectra were recorded on a Nicolet iS20 FT-IR spectrophotometer. FTIR spectra of the samples in the solid state were recorded using the KBr pellet technique in the wavenumber range from 1200 to 400 cm−1with 32 scans and 4 cm−1resolution. Nuclear Magnetic Resonance Spectroscopy. The31P NMR spectra were recorded on a 400 MHz JEOL ECX instrument at room temperature in 5 mm NMR tubes with a resonance frequency of 16.688 MHz in H2O / D2O or CH3CN / CD3CN, respectively. The chemical shift values are reported with respect to 85% H3PO4 in aqueous solution as reference. Thermogravimetric Analysis. TGA was performed on a TA Instruments Model SDT Q600 thermobalance under nitrogen flow. The temperature was ramped from room temperature to 400 °C at a rate of 5 °C / min. X-Ray Diffraction. For single-crystal X-ray diffraction experiments, the crystals were mounted on a Hampton cryoloop in light oil for data collection at 100 K on a Bruker D8 SMART APEX II CCD diffractometer. Data were measured using ω-scans of 1° per frame using Mo Kα radiation (λ = 0.71073 Å). Data integration and routine processing were performed using the SAINT software suite. Absorption corrections were applied using the SADABS program (Sheldrick, G. M., SADABS, Program for Empirical X-ray Absorption Correction; Bruker-Nonius, 1990). The structures were solved by direct methods (SHELXS97) and refined by the full-matrix least-squares method (Σw(Fo2 – Fc2)2) according to Sheldrick, G. M., SHELXL97, Program for Crystal Structure Refinement; University of Göttingen, Göttingen, Germany, 1997. Sorption Measurements. N2-adsorption (physisorption) measurements for surface area and pore size analysis were performed at 77 K on a Quantachrome NOVA 4000e surface area and pore size analyzer and a Quantachrome Autosorb-1 analyzer. Samples were placed in 9 mm Quantachrome cells and degassed under vacuum at 100 °C for 16 hours prior to measurements. The surface area was estimated using the Brunauer–Emmett–Teller (BET) theory and pore size was determined using Barrett-Joyner-Halenda (BJH) method. Example 1 Synthesis of K16[Zr2(O2)2(P2W17O61)2]·23H2O (K-ZrP). ZrOCl2·8H2O (0.040 g, 0.124 mmol) was dissolved in 6 mL of water at 60 °C and K-P2W17 (0.614 g, 0.124 mmol) was added. To this cloudy solution 1 mL (8.8 mmols) 30% H2O2 was added dropwise under stirring. The solution was 202300115 14 maintained at 60 °C and stirred for a further 30 minutes. The clear yellow solution was allowed to cool down to room temperature and then left to crystallize in an open vial at room temperature. Pale-yellow cube-shaped crystals were collected after a week (yield 0.36 g, 60%). IR peaks in cm-1(KBr pellet): 1084 (s), 1059 (w), 1020 (w), 945 (s), 889 (w), 793 (s,b), 530 (w). Elemental analysis (%) calcd: W 65.0, P 1.29, Zr 1.90, K 6.5; found: W 65.7, P 1.22, Zr 1.98, K 6.0. Example 2 Synthesis of K16[Hf2(O2)2(P2W17O61)2]·26H2O (K-HfP). The same synthetic procedure as for K- ZrP was followed but using 0.040 g (0.124 mmol) of HfCl4. Yield 0.26 g, 42%. IR peaks in cm-1(KBr pellet): 1085 (sh), 1022 (w), 945 (s), 791 (s), 528 (m). Elemental analysis (%) calcd: W 63.5, P 1.26, Hf 3.63, K 6.36; found: W 62.4, P 1.23, Hf 3.65, K 6.43. Example 3 Synthesis of K16[Zr2(O2)2(As2W17O61)2]·26H2O·KCl (K-ZrAs). The same synthetic procedure as for K-ZrP was followed but using 0.622 g (0.124 mmol) of K10[α-As2W17O61]·21H2O. Yield 0.25 g, 38%. IR peaks in cm-1(KBr pellet): 955 (sh), 882 (w), 880 (w), 782 (sh), 527 (s), 422 (s). Elemental analysis (%) calcd: W 63.0, As 3.02, Zr 1.84, K 6.70, Cl 0.36; found: W 62.3, As 3.22, Zr 1.87, K 6.36, Cl 0.36. Example 4 Synthesis of K16[Hf2(O2)2(As2W17O61)2]·26H2O (K-HfAs). The same synthetic procedure as for K- HfP was followed but using 0.622 g (0.124 mmol) of K10[α-As2W17O61]·21H2O. The crystalline product was collected after 2 weeks (yield 0.22 g, 32%). IR peaks in cm-1(KBr pellet): 955 (m), 886 (s), 863 (s), 779 (s), 526 (m) 492 (m). Elemental analysis (%) calcd: W 62.4, As 2.99, Hf 3.56, K 6.25; found: W 62.6, As 2.77, Hf 3.52, K 6.15. Crystal data and structure refinement for K-ZrP, K-HfP, K-HfAs are given in Table 1. Table1. Crystal data and structure refinement for K-ZrP, K-HfP, K-HfAs K-ZrP K-HfP K-HfAs Empirical H46K16O149P4W34Zr2 ClH52Hf2K16O152P4W34 As4H52Hf2K16O152W34 formula Formula weight, 9613.19 9877.22 10017.57 g / mol Crystal system triclinic triclinic triclinic Space group P P P a, Å 12.2196(9) 12.2345(9) 12.1983(9) b, Å 12.8154(10) 12.8282(10) 12.8847(9) c, Å 29.138(2) 29.112(2) 29.033(2) α, deg 88.716(2) 88.801(3) 88.517(2) β, deg 80.073(2) 80.273(3) 80.075(2) 202300115 15 γ, deg 62.651(2) 62.404(3) 62.3389(18) Volume, Å33983.9(5) 3982.4(5) 3973.5(5) Z 1 1 1 Dcalc, g / cm34.007 4.118 4.186 Absorption coeff 25.118 26.318 27.146 F(000) 4198.0 4309.0 4364.0aR = Σ||Fo| − |Fc|| / Σ|Fo|.bRw = [Σw(Fo2− Fc2)2 / Σw(Fo2) Example 5 Synthesis of TBA10H5K[Zr2(O2)2(P2W17O61)2] (TBA-ZrP).1.00 g (0.104 mmol) of K-ZrP was dissolved in 30 mL water and the pH was adjusted to 4 with 0.25 M HNO3 solution. Then 1.00 g (0.036 mol) tetra-n-butyl ammonium chloride (TBACl) was added, leading to the formation of a white precipitate. After vigorous stirring for 10 min the precipitate was isolated by filtration. The crude product was dispersed in 30 mL water, and the pH was adjusted to 3 with 0.25 M HNO3, and then again 1.00 g (0.036 mol) TBACl was added. After vigorous stirring, the white precipitate was isolated by filtration and washed with ca 200 mL water. Yield 0.90 g, 86%. IR peaks in cm-1(KBr pellet): 2961 (sh), 2874 (sh), 1483 (m), 1384 (sh), 956 (sh), 916 (m), 794 (sh), 530 (s). Elemental analysis (%) calcd: W 56.6, P 1.12, Zr 1.65, K 0.4, C 17.4, H 3.33, N 1.27; found: W 56.5, P 1.02, Zr 1.65, K 0.5, C 17.9, H 3.44, N 1.29. Example 6 Synthesis of TBA11H5[Hf2(O2)2(P2W17O61)2] (TBA-HfP). The same procedure as for TBA-ZrP was followed but using 1.00 g (0.100 mmol) K-HfP (yield 0.81 g, 81%). IR peaks in cm-1(KBr pellets): 2961 (sh), 2874 (sh), 1539 (s), 1484 (sh), 1384 (sh), 1090 (sh), 956 (sh), 913 (m), 794 (w), 529 (s). Elemental analysis (%) calcd: W 54.7, P 1.08, Hf 3.13, C 18.50, H 3.54, N 1.35; found: W 55.2, P 0.99, Hf 2.98, C 18.74, H 3.35, N 1.41. Example 7 ZrP-apts-SBA15 Catalyst Preparation. SBA-15 was synthesized and (3-aminopropyl) triethoxysilane (apts)-surface modified according to the published procedures (a) Zhao, D.; Feng, J.; Huo, Q.; Melosh, N.; Fredrickson, G. H.; Chmelka, B. F.; Stucky, G. D.; Triblock Copolymer Syntheses of Mesoporous Silica with Periodic 50 to 300 Angstrom Pores. Science, 1998, 279, 548–552. (b) Chen, L.; Hu, J.; Mal, S. S.; Kortz, U.; Jaensch, H.; Mathys, G.; Richards, R. M. Heterogeneous Wheel-Shaped Cu20-Polyoxotungstate [Cu20Cl(OH)24(H2O)12(P8W48O184)]25−Catalyst for Solvent-Free Aerobic Oxidation of n-Hexadecane. Chem. Eur. J.2009, 15, 7490-7497. For the immobilization of K-ZrP thereon, the obtained SBA- 15–apts (500 mg) was mixed with 100 mL water, and 2M HCl was added to adjust the pH to about 2. Then, the K-ZrP(100 mg) was added so that the weight% of ZrP loaded to the support is ~16%, and the mixture was stirred overnight. The solids were filtered-off and dried. ZrP incorporation onto the support was confirmed by the FTIR spectroscopy showing characteristic peaks of K-ZrP in the range 400-1000 cm-1and surface area and pore volume reduction from 486 m2 / g and 0.712 cc / g to 202300115 16 228 m2 / g and 0.680 cc / g respectively confirmed by Brunauer-Emmett-Teller (BET) surface area measurement of the catalyst immobilized apts-SBA-15. This procedure was performed accordingly using the respective polyoxometalate salts for the synthesis of ZrAs-apts-SBA15, HfAs-apts-SBA15 and HfP-apts-SBA15. Example 8 Cyclohexanol Oxidation. ZrP-apts-SBA15apts (100 mg,), 33% aqueous hydrogen peroxide (7 ml, 68 mmol) and cyclohexanol (1.4 ml, 13.3 mmol) were mixed and stirred at 80 ⁰C in a microwave reactor for 4 hours (18 hours for conventional heating). The reaction mixture was centrifuged to remove the catalyst and the resultant solution was cooled to room temperature. When the mixture was allowed to stand overnight at 0 ⁰C, white crystals of adipic acid precipitated. The solution was analyzed using1H and13C NMR to obtain adipic acid (68%) and 6-hydroxyhexanoic acid (32%). Example 9 KA-Oil Oxidation. ZrP-apts-SBA15apts (100 mg,), 33% aqueous hydrogen peroxide (6.3 ml, 61 mmol) and KA oil (1.4 ml, 13.3 mmol) were mixed and vigorously stirred at 80 ⁰C in a microwave reactor for 6 hours. The reaction mixture was centrifuged to remove the catalyst and the resultant solution cooled to room temperature. When the mixture was allowed to stand overnight at 0 ⁰C, white crystals of adipic acid precipitated. The solution was analyzed using1H and13C NMR to obtain adipic acid (approx.80%) and 6-hydroxyhexanoic acid (approx.20%). Example 10 Cyclohexene Oxidation. ZrP-apts-SBA15apts (100 mg,), 33% aqueous hydrogen peroxide (7.6 ml, 74 mmol) and cyclohexene (1.4 ml, 14.8 mmol) were mixed and stirred at 80 ⁰C in a microwave reactor for 6 hours. The reaction mixture was centrifuged to remove the catalyst and the resultant solution cooled to room temperature. The solution was analyzed using1H and13C NMR to obtain adipic acid (approx.60%) and cyclohexane diol (approx.40%). Example 11 The peroxo-POM, [CeIV2(O2)(P2W16O59)2]18-(Ce2P2W16) was synthesized in aqueous medium starting with a CeIIIsalt and building up {P2W16O59} from [H2P2W12O48]12-and Na2WO4 at suitable pH. K-P2W12(788 mg, 0.200 mmol) was dissolved in 10 mL 1 M LiCl. To this, a solution of Na2WO4·2H2O (264 mg, 0.8 mmol) dissolved in 1 mL water was added and stirred for 2 minutes at room temperature. The pH of the resultant solution is approx.7.5. A solution of Ce(NO3)3·6H2O (174 mg, 0.400 mmol) in 400 μL 2 M acetic acid was prepared and slowly added to the above solution dropwise. The pH of the resultant solution was adjusted to 5 with 33% H2O2 and stirred at 60 °C for 15 minutes. This solution was filtered at room temperature. The precipitate formed next day was filtered off again and the clear solution was kept for crystallization. Orange needle crystals were formed after 1 week. (Yield: 140 mg, 17%). IR peaks in cm-1(KBr pellet): 1117 (s), 1077 (s), 1022 (m), 943 (w), 922 (w), 841(w), 793 (w), 737 (w), 627 (w), 495 (b). Elemental analysis (%) 202300115 17 calcd: W 63.4, P 1.34, Ce 3.02, K 5.06, Na 0.50, Li 0.30; found: W 62.5, P 1.30, Ce 4.73, K 5.14, Na 0.48, Li 0.32 Ce2P2W16 was crystallized out as a mixed K+, Li+and Na+salt with the formula K12Li4Na2[CeIV2(O2)(P2W16O59)2]·26H2O (KLiNa-Ce2P2W16). Table 2. Crystal data for KLiNa-Ce2P2W16Formula weight, g / mol 8902.21 Crystal system triclinic Space group P a, Å 12.748(3) b, Å 15.323(3) c, Å 20.442(4) α, deg 75.256(6) β, deg 73.593(6) γ, deg 77.660(6) Volume, Å33660.82(130) Z 1 Example 12 (NH4)2Ce(NO3)6(137 mg, 0.25 mmol) was dissolved in 6 mL water and stirred at 60 °C for 5 minutes. To this 1.55 g (0.35 mmol) Na-P2W15 was added and stirred until solution turned clearer.1 mL 33% H2O2 was subsequently added, and solution was continued stirring for another 1 hour at 60 °C. The dark red solution was then cooled down and kept for crystallization where dark red crystals of mixed Na+, NH4+salt with a formula of [CeIV8(O2)12(P2W16O59)4]40-(Ce8P2W16) start to appear in 2 days. (Yield: 0.36 g, 60%). IR peaks in cm-1(KBr pellet): 1089 (s), 1040 (m), 1010 (m), 950 (w), 926 (w), 873(w), 819 (w), 759 (m), 599 (w), 517 (m). Elemental analysis (%) calcd: W 58.22, P 1.23, Ce 5.55, Na 3.64, N 0.55, H 1.29; found: W 58.0, P 1.23, Ce 5.35, Na 3.77, N 0.52, H 1.12. Ce8P2W16crystallizes out as a mixed sodium-ammonium salt, Na32(NH4)8[CeIV8(O2)12(P2W16O59)4]·113H2O. The structure of NaNH4-Ce8P2W16comprises of four dilacunary {P2W16O59} POMs which have their two WO6 octahedra removed from the cap and those positions occupied by CeIV. The four POM units are arranged in such a way that the total eight cerium in the structure forms a square-like core and all the ceriums are interconnected to each other via alternating double and single peroxo-bonds. Hence the transition metal-peroxo core of the structure is formed by 8 CeIVand 12 peroxygens. The four dilacunary Wells-Dawson POM units are 202300115 18 spatially directing to one side of the plane of CeIVmaking the total structure look like bowl-shaped and reducing its symmetry to C2v. Table 3. Crystal data for NaNH4-Ce8P2W16 Formula weight, g / mol 5729.51 Crystal system triclinic Space groupPa, Å 21.687 b, Å 28.183 c, Å 28.795 α, deg 90.77 β, deg 91.80 γ, deg 91.26 Volume, Å317585 Z 2 Example 13 Ce8P2W16-apts-SBA15 Catalyst Preparation. SBA-15 was synthesized and (3-aminopropyl) triethoxysilane (apts)-surface modified according to procedure explained example 7. For the immobilization of NaNH4-Ce8P2W16 thereon, apts-SBA-15 (500 mg) was mixed with 100 mL water, and 2M HCl was added to adjust the pH to about 4. Then, NaNH4-Ce8P2W16(100 mg) was added so that the weight% of POM loaded to the support is ~16%, and the mixture was stirred overnight. The solids were filtered-off and dried. POM incorporation onto the support was confirmed by N2- adsoprtion isotherm from BET surface area measurement. The surface area shows a reduction from 486 m2 / g to 231 m2 / g and the pore volume from 0.712 cc / g to 0.621 cc / g after POM immobilization confirming the successful immobilization of the POM onto the support SBA15-apts. Example 14 Biphasic Catalysis. A comparative study between homogeneous and heterogeneous biphasic catalysis was done using the NaNH4-Ce8P2W16catalyst. In a typical homogeneous reaction, the substrate (~10 mmol) forms the organic layer, and the catalyst (4.5 μmol) dissolved in 33% H2O2 (75 mmol) forms the aqueous layer. Catalysis was done in a microwave reactor with temperature control and the products were analyzed using Gas Chromatography and13C NMR. The same procedure was repeated for heterogeneous biphasic system where the modified-SBA15-apts supported Ce8P2W16-apts-SBA15 (100 mg; 0.83 μmol POM) was used instead as the catalyst, forming a third, heterogeneous phase. 202300115 19 Benzyl alcohol as a model substrate for alcohol oxidation in homogeneous biphasic system exhibited a conversion of 80% with an increased aldehyde selectivity of 59% compared to acid (41%) and at a temperature of 70 ⁰C for a reaction time of 6 hrs. Whereas the same reaction conditions in the heterogeneous biphasic system showed an increased selectivity towards benzoic acid (53% when kept for 10 h) but at a lower conversion rate. The same reaction at 90 ⁰C showed similar conversion to that of the homogeneous system Alkene epoxidation was compared for two model but with a very evident selectivity towards benzoic acid (65%) rather than to benzaldehyde (35%). Alkene epoxidation was compared for two model substrates: 1-octene and cyclooctene. Heterogeneous catalysis was evidently better with respect to conversion and acid selectivity whilst homogeneous catalysis yielded low conversion rates with oxidation stopping at epoxides or diols for the same reaction conditions. In the case with heterogeneous catalysis, a primary alkene was oxidized to its corresponding alkane diol and mono carboxylic acid with acid having slightly more selectivity. Cyclic alkene, on the other hand, was preferentially converted to alkane dicarboxylic acid by C-C bond cleavage along with small amounts of epoxide. Substrate Homogeneous Biphasic Heterogeneous Biphasic Conversion Selectivity Conversion Selectivity (%) (%) Benzyl alcohol 80 59 41 83 35 65 (aldehyde) (acid) (aldehyde) (acid) 1-octene 29.6 98 2 56.5 42 58 (diol) (acid) (diol) (acid) cyclooctene 21 100 - 51 21 79 (epoxide) (epoxide) (diacid) Example 15 Synthesis of Na34K2[CeIV12(O2)17(OH)2(O)4(SiW9O34)4]·43H2O (NaK-Ce12SiW9): CeCl3·7H2O (130 mg, 0.35 mmol) was dissolved in 10 mL H2O. To this solution POM precursor Na-SiW9 (973 mg, 0.35 mmol) was added. The solution turns turbid orange. Stir this solution for 5 minutes at 50 °C before bringing down the pH to 7 with 33% H2O2. The solution turns clear dark red on the addition of H2O2 and was continued stirring at the same temperature for 30 minutes. The final pH of the solution is again adjusted to 8.0 with 33% H2O2.4 drops of 0.25 M KCl was added as a crystallizing agent. Dark red needle crystals were formed overnight. (Yield: 77 mg, 29%). %). IR peaks in cm-1(KBr pellet): 999 (m), 956 (w), 934 (m), 889 (m), 843 (m), 794 (w), 752 (m), 660 (w), 540 (w), 522 (m). Elemental analysis (%) calcd: W 51.45, Si 0.87, Ce 13.07, Na 6.08, K 0.61; found: W 52.0, Si 0.514, Ce 14.2, Na 5.57, K 0.68. Example 16 Synthesis of Na34K2[CeIV12(O2)18(O)4(GeW9O34)4]·79H2O (NaK-Ce12GeW9): The same synthetic procedure for NaK-Ce12SiW9 was followed but with Na-GeW9 POM precursor (875.4 mg, 0.35 202300115 20 mmol). (Yield: 37%). IR peaks in cm-1(KBr pellet): 961 (s), 911 (w), 885 (w), 848 (w), 797 (m), 723 (m), 610 (w), 518 (m), 468 (m), 441 (w), 417 (w). Elemental analysis (%) calcd: W 48.35, Ge 2.12, Ce 12.28, Na 5.71, K 0.57; found: W 47.0, Ge 3.9, Ce 13.2, Na 3.4, K 0.625. Table 4. Crystal data for NaK-Ce12SiW9 and NaK-Ce12GeW9 NaK-Ce12SiW9 NaK-Ce12GeW9 Crystal system orthorhombic orthorhombic Space group Cmcm Cmcm a, Å 32.9844(5) 33.2487(5) b, Å 30.2903(4) 30.4981(4) c, Å 27.2227(3) 27.8761(3) α, deg 90 90 β, deg 90 90 γ, deg 90 90 Volume, Å327198.4(6) 27668.7(6) Z 4 4 Comparative Example 1 Patent No. CN108262073A. The catalyst H3PW12@UiO66 was prepared according to described published procedure described in Feng, J.; Li, M.; Meng, X. Green Oxidation of Cyclohexanone to Adipic Acid over Phosphotungstic Acid Encapsulated in UiO-66. Catal. Letters 2019, 149, 1504– 1512. In a typical reaction, catalyst (500 mg), 33% aqueous hydrogen peroxide (16 ml, 154 mmol) cyclohexanol (2.9 ml, 31 mmol) and oxalic acid (55.4 mg, 0.44 mmol) were stirred in a round- bottom flask at 90 ⁰C for 8 hours. We observed the following products by1H and13C NMR: cyclohexanone (approx.75%), 6-hydroxyhexanoicacid (approx.20%) and adipic acid (approx.5%). The conversion remained the same even with prolonged reaction time (up to 24 hours). This result shows that the inventive catalyst has a higher catalytic activity and conversion rate in comparison to the state of the art. Comparative Example 2 Patent No. EP1544190B1. In a typical reaction, H2WO4 (1.33 mmol, 332.5 mg), 33% aqueous hydrogen peroxide (60 ml, 585 mmol) and cyclohexanol (12.4 ml, 133 mmol) were stirred and refluxed in a round-bottom flask at 90 ⁰C for 20 hours. Insoluble H2WO4 in the presence of hydrogen peroxide was noted to form soluble peroxo-tungstate and was dissolved in the solution as a homogeneous system. When the mixture was allowed to stand overnight at 0 ⁰C, white crystals of adipic acid precipitated (isolated yield 51%).13C NMR of the solution showed the presence of adipic acid and 6-hydroxy hexanoic acid as the products. 202300115 21 This result shows that the inventive catalyst has a higher catalytic activity and conversion rate in comparison to the state of the art.

Claims

202300115 22 CLAIMS 1. A method for producing a carboxylic acid, which comprises following reaction steps: a) providing an alicyclic ketone, an alicyclic alcohol or a mixture of an alicyclic ketone and an alicyclic alcohol, b) reacting the alicyclic alcohol and / or the alicyclic ketone from step a) with a peroxide or peroxide providing reagent in the presence of a catalyst to an oxidation product, c) separating the oxidation product from the catalyst, wherein the catalyst comprises a peroxo-polyoxometalate, wherein the peroxo- polyoxometalate comprising a repeating unit selected from A, A’ or B, wherein the units A, A’ and B consist of the following formula:wherein M is a metal ion selected from a group of Zr, Hf, Rf, Ce, Th, Nb, Ta, Re and any transition metal ion with a coordination number ≥ 8, wherein the repeating units A, A’ and / or B can be fused directly to each other via a common metal atom M or linked via an oxo, hydroxo or hydroperoxo group connecting two metal atoms M of two repeating units A, A’ and / or B, wherein the peroxo-polyoxometalate comprises m repeating units A, n repeating units B and o repeating units A’, wherein n, m and o are integer numbers selected from 0 to 20, wherein m, n and o cannot simultaneously be equal to 0, wherein M is coordinated to polyoxometalate (POM), wherein the coordination number of each M is at least 8, wherein the peroxo-polyoxometalate comprises a ligand based on mono-, di-, tri- lacunary Keggin or Wells-Dawson ions or wheels and its derivatives, wherein the peroxo-polyoxometalate has a linear, cyclic or spherical structure.

2. A method for producing a carboxylic acid according to claim 1, wherein the peroxo- polyoxometalate comprises following combinations of repeating units: ^ m = 0, n = 1, o = 0, ^ m = 4, n = 4, o = 0, ^ (m + o) = 4, n = 0, ^ m = 17 or 18, n = 0, o = 0,202300115 23 ^ (m + o) = 17 or 18, n = 0 ^ m = 1, n = 0, o = 0, or ^ m = 0, n = 0, o = 1.

3. The method for producing a carboxylic acid according to claim 1 or 2, wherein the peroxo- polyoxometalate comprises one of the anions selected from the group of: ^ [M2(O2)2(Y2Z17O61)2]16-, wherein M is selected from Zr, Hf and Ce and Y is selected from P and As and Z is selected from W and Mo, ^ [M8(O2)12(Y2Z16O59)4]40-, wherein M is selected from Ce, Zr and Hf and Y is selected from P and As and Z is selected from W and Mo, ^ [M12(O2)18(O)4(YZ9O34)4]36-, wherein M is selected from Ce, Zr and Hf, preferably M is Ce, and Y is selected from Ge and Si and Z is selected from W and Mo, wherein [M12(O2)18(O)4(YZ9O34)4]36-optionally can occur as single or multiple peroxo-depleted structures, wherein one or more O22-is replaced each by mono- or di- OH- ^ [M12(O2)17(OH)2(O)4(YZ9O34)4]36-, Ce, Zr and Hf, preferably M is Ce, and Y is selected from Ge and Si and Z is selected from W and Mo, wherein [M12(O2)17(OH)2(O)4(YZ9O34)4]36-optionally can occur as single or multiple peroxo- depleted structures, wherein one or more O22-is replaced each by mono- or di- OH- or ^ [M2(O2)(Y2Z16O59)2]18-, wherein M is selected from Ce, Zr and Hf and Y is selected from P and As and Z is selected from W and Mo.

4. The method for producing a carboxylic acid according to one of the preceding claims, wherein the peroxo-polyoxometalate comprises an anion selected from the group of: [Zr2(O2)2(P2W17O61)2]16-, [Hf2(O2)2(P2W17O61)2]16-, [Zr2(O2)2(As2W17O61)2]16-, [Hf2(O2)2(As2W17O61)2]16-, [Ce12(O2)17(OH)2O4(SiW9O34)4]36-, [Ce12(O2)18O4(GeW9O34)4]36-, [Ce2(O2)(P2W16O59)2]18-or [Ce8(O2)12(P2W16O59)4]40-.

5. The method for producing a carboxylic acid according to one of the preceding claims, wherein the peroxo-polyoxometalate is fixed to a solid.

6. The method for producing a carboxylic acid according to claim 5, wherein the solid is a silica material, preferably a mesoporous silica material.

7. The method for producing a carboxylic acid according to one of the preceding claims, wherein the catalyst is heterogeneous in a reaction mixture in step b).

8. The method for producing a carboxylic acid according to one of the preceding claims, wherein d) the catalyst is recycled after step c) into step b).202300115 24 9. The method for producing a carboxylic acid according to one of the preceding claims, wherein the peroxide is selected from the group of aqueous hydrogen peroxide, peracetic acid, persulfate, any other active oxygen providing compound and mixtures thereof.

10. The method for producing a carboxylic acid according to one of the preceding claims, wherein the process is performed continuously.

11. The method for producing a carboxylic acid according to claim 1, wherein the mixture of step b), which comprises an alicyclic ketone and / or alicyclic alcohol, hydrogen peroxide and the catalyst further comprises a solvent.

12. The method for producing a carboxylic acid according to one of the preceding claims, wherein the alicyclic alcohol is a compound represented by the following formula (1) or the alicyclic ketone is a compound represented by the following formula (2):wherein q is an integer of 1 to 18; and R1, R2, R3and R4, are the same or different and each is selected from the group of hydrogen atom, hydroxyl group, halogen atom, carboxyl group, alkyl group, alkoxy group, cycloalkyl group, an aryl group, aralkyl group, acyl group or an acyloxy group, or R1and R2, R1and R3, R1and R4, R2and R4or R3and R4may be taken together to form a carbon ring, which may be substituted with an alkyl group having from 1 to 4 carbon atoms, an alkoxy group having from 1 to 4 carbon atoms, an cycloalkyl group having 3 to 7 carbon atoms, an aryl group , an aralkyl group, a carboxyl group or a halogen atom.

13. The method for producing a carboxylic acid according one of the preceding claims, wherein the carboxylic acid is selected from the group of glutaric acid, adipic acid or derivatives thereof.

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