PROCESS FOR MANUFACTURING AN AQUEOUS HYDROGEN PEROXIDE SOLUTION

Abstract

A process for manufacturing an aqueous hydrogen peroxide solution comprising the following steps:—hydrogenating a working solution which comprises an alkylanthraquinone and/or tetrahydroalkylanthraquinone and a mixture of a non-polar organic solvent and a polar organic solvent;—oxidizing the hydrogenated working solution to produce hydrogen peroxide; and—isolating the hydrogen peroxide, wherein the polar organic solvent is 5-methyl-2-isopropylcyclohexanecarbonitrile (C11F).

Claims

1.-14. (canceled)

15. A process for manufacturing an aqueous hydrogen peroxide solution comprising the following steps: hydrogenating a working solution which comprises an alkylanthraquinone and/or tetrahydroalkylanthraquinone and a mixture of a non-polar organic solvent and a polar organic solvent; oxidizing the hydrogenated working solution to produce hydrogen peroxide; and isolating the hydrogen peroxide, wherein the polar organic solvent is 5-methyl-2-isopropylcyclohexanecarbonitrile (C11F).

16. The process according to claim 15, said process having a production capacity of hydrogen peroxide of up to 100 kilo tons per year.

17. The process according to claim 15, said process being operated in a plant located at an industrial end user site.

18. The process according to claim 15, wherein the C11F has been obtained by reaction of menthol with mesyl or tosyl chloride followed by cyanation.

19. The process according to claim 15, wherein the C11F has been obtained by reaction of menthol with phosphorus tribromide (PBr3), phosphorus trichloride (PCl3), phosphorus triiodide (PI3), potassium iodide (KI) with acid catalysis, thionyl chloride (SOC12) or thionyl bromide (SOBr2), followed by cyanation.

20. The process according to claim 15, wherein the C11F has been obtained by an esterification reaction of menthol with an anhydride, an acid or an acyl chloride said anhydride, acid or acyl chloride bearing a trifluoromethyl group, followed by cyanation.

21. A method of manufacturing 5-methyl-2-isopropylcyclohexanecarbonitrile by an esterification reaction of menthol with an anhydride, acid or acyl chloride said anhydride, acid or acyl chloride bearing a trifluoromethyl group, followed by cyanation.

22. The method according to claim 21, wherein the esterification reaction uses TFAC (TriFluoroAcetylChloride), trifluoroacetic acid, triflic anhydride or trifluoromethyl acetic anhydride.

23. The method according to claim 21, wherein the esterification reaction medium comprises a solvent for the menthol.

24. The method according to claim 21, wherein the esterification reaction uses an acyl chloride and wherein the esterification reaction medium comprises a compound able to trap the acid released (HCl) like pyridine, triethylamine, DIPEA (Hunig's base), proton sponge, imidazole, any aromatic molecule containing a pyridine-like nitrogen able to react with HCl to give the corresponding chlorhydrate salt, inorganic bases.

25. The method according to claim 21, wherein the esterification reaction uses TFAC and either said TFAC is bubbling through the reaction mixture at atmospheric pressure, or the esterification reaction takes place in an autoclave at a pressure up to 10 bar.

26. The method according to claim 21, wherein the anhydride, acid or acyl chloride is recovered by distillation or selective extraction.

27. The method according to claim 21, wherein the cyanation involves the use of KCN and/or NaCN.

28. The method according to claim 27 wherein the cyanation takes place in a polar solvent.

29. The method of claim 28 wherein the polar solvent is selected from the group consisting of DMF, DMSO and sulfolane.

30. A method of manufacturing 5-methyl-2-isopropylcyclohexanecarbonitrile by reaction of menthol with phosphorus tribromide (PBr3), phosphorus trichloride (PCl3), phosphorus triiodide (PI3), potassium iodide (KI) with acid catalysis, thionyl chloride (SOCl2) or thionyl bromide (SOBr2), followed by cyanation.

Description

[0022] In a preferred embodiment, after its extraction, the crude aqueous hydrogen peroxide solution is washed several times i.e. at least two times consecutively or even more times as required to reduce the content of impurities at a desired level.

[0023] The term “washing” is intended to denote any treatment, which is well known in the chemical industry (as disclosed in GB841323A, 1956 (Laporte), for instance), of a crude aqueous hydrogen peroxide solution with an organic solvent which is intended to reduce the content of impurities in the aqueous hydrogen peroxide solution. This washing can consist, for example, in extracting impurities in the crude aqueous hydrogen peroxide solution by means of an organic solvent in apparatuses such as centrifugal extractors or liquid/liquid extraction columns, for example, operating counter-current wise. Liquid/liquid extraction columns are preferred. Among the liquid/liquid extraction columns, columns with random or structured packing (like Pall rings for instance) or perforated plates are preferred. The former are especially preferred.

[0024] In a preferred embodiment, a chelating agent can be added to the washing solvent in order to reduce the content of given metals. For instance, an organophosphorus chelating agent can be added to the organic solvent as described in the above captioned patent application EP 3052439 in the name of the Applicant, the content of which is incorporated by reference in the present application.

[0025] The expression “crude aqueous hydrogen peroxide solution” is intended to denote the solutions obtained directly from a hydrogen peroxide synthesis step or from a hydrogen peroxide extraction step or from a storage unit. The crude aqueous hydrogen peroxide solution can have undergone one or more treatments to separate out impurities prior to the washing operation according to the process of the invention. It typically has an H2O2 concentration within the range of 30-50% by weight.

[0026] The solvents of the invention make it is possible to achieve a higher solubility and thus there is less polar solvent needed to achieve a higher partition coefficient. With this higher partition coefficient it is possible to reduce the capex (capital expenditure) required for the extraction sector. The solvents of the invention are particularly suitable for the manufacture of hydrogen peroxide by the AO-process wherein said process has a production capacity of hydrogen peroxide of up to 100 kilo tons per year (ktpa). Preferably said process is a small to medium scale AO-process operated with a production capacity of hydrogen peroxide of up to 50 kilo tons per year (ktpa), and more preferably with a production capacity of hydrogen peroxide of up to 35 kilo tons per year (ktpa), and in particular a production capacity of hydrogen peroxide of up to 20 kilo tons per year (ktpa). The dimension ktpa (kilo tons per annum) relates to metric tons.

[0027] A particular advantage of such a small to medium scale AO-process is that the hydrogen peroxide can be manufactured in a plant that may be located at any, even remote, industrial end user site and the solvents of the invention are therefore especially suitable. It is namely so that since their partition coefficient is more favourable, less emulsion is observed in the process and a purer H2O2 solution can be obtained (namely containing less TOC) and this for a longer period of time compared to when solvents known from prior art are used. In a preferred sub-embodiment of the invention, the working solution is regenerated either continuously or intermittently, based on the results of a quality control, regeneration meaning conversion of certain degradates, like epoxy or anthrone derivatives, back into useful quinones. Here also, the solvents of the invention are favourable because the quality of the H2O2 solution can be maintained within the specifications namely in terms of TOC for a longer period of time.

[0028] As explained above, the main feature of the invention is the recourse to a mixture of a polar organic solvent and a non-polar organic solvent wherein the polar organic solvent is C11F. This compound (5-methyl-2-isopropylcyclohexanecarbonitrile or C11F) has namely been synthesized starting from menthol by Debra K. Dillner (2009), Syntheses of C-1 Axial Derivatives of 1-Menthol, Organic Preparations and Procedures International, 41:2, 147-152, DOI:10.1080/00304940902802008.

[0029] In the method described in this paper, menthol was first reacted with methanesulfonyl chloride (mesyl chloride) in dichloromethane (DCM) with the addition of triethylamine (to trap the HCl generated) and then, the mesylate so obtained was reacted with KCN in acetonitrile and in the presence of 18-crown-6 (a phase transfer agent—which complexes the K ion and improves the solubility of KCN in the organic phase and enhance the nucleophile strength of formula [C2H4O]6) to generate the compound C11F. This paper also makes reference to a previous method starting from menthyl tosylate with NaCN in DMSO.

[0030] Hence, in a first embodiment, the C11F used in the process of the invention has been obtained by reaction of menthol with mesyl or tosyl chloride followed by the cyanation of the obtained mesylate or tosylate, preferably with KCN and/or NaCN.

[0031] This synthesis method has the drawback that organic reactives are used, which generate organic effluents.

[0032] Hence, in a second embodiment, the C11F used in the process of the invention has been obtained by reaction of menthol with phosphorus tribromide (PBr3), phosphorus trichloride (PCl3), phosphorus triiodide (PI3), potassium iodide (KI) with acid catalysis, thionyl chloride (SOCl2) or thionyl bromide (SOBr2), followed by the cyanation of the obtained bromide, iodide or chloride, preferably with KCN and/or NaCN.

[0033] Although these methods work in practice, they might be improved by the use of other reactives including much more efficient reactive groups which hence imply shorter reaction times. Hence, in a third preferred embodiment, the C11F used in the process of the invention has been obtained by reaction of menthol with an anhydride, acid or acyl chloride bearing a trifluoromethyl group, followed by cyanation.

[0034] Since this synthesis route has never been reported up to date, the present invention also relates to a method of manufacturing 5-methyl-2-isopropylcyclohexanecarbonitrile or C11F by an esterification reaction of menthol with an anhydride, a carboxylic acid or an acyl chloride bearing a trifluoromethyl group, followed by cyanation, preferably with KCN and/or NaCN.

[0035] The preferred reactives for the esterification reaction with menthol are TFAC (TriFluoroAcetylChloride), trifluoroacetic acid, trifluoromethanesulfonyl (triflic) anhydride or trifluoromethyl acetic anhydride. The esterification reaction medium preferably comprises a solvent for the menthol, like for instance dichloromethane (DCM), or any other inert aromatic solvent like toluene, or aliphatic solvent like alkane. In the case of TFAC or of other acyl chlorides, the esterification reaction medium preferably also comprises a compound able to trap the acid released (HCl) like pyridine, triethylamine, DIPEA (Hunig's base), proton sponge, imidazole, or any aromatics containing a pyridine-like nitrogen able to react with HCl to give the corresponding chlorhydrate salt, inorganic bases like Na2CO3, sodium bicarbonate etc. The esterification reaction preferably takes place at a temperature from −20 to 50° C., preferably at ambient temperature. It also preferably takes place at atmospheric pressure. In the case of TFAC, which is a gas, said TFAC can either be bubbling through the reaction mixture at atmospheric pressure, or the reaction can take place in an autoclave at a pressure up to 10 bar.

[0036] The anhydride, acid or acyl chloride used in the esterification reaction is preferably recovered, preferably by distillation or selective extraction.

[0037] As to the cyanation, it generally involves the use of compounds like KCN, NaCN and the like. KCN and/or NaCN are preferred for an industrial process mainly for economic reasons. Cyanation preferably takes place in a polar solvent like DMF, DMSO or sulfolane. The reaction temperature preferably is from 50 to 150° C., preferably between 100 and 140° C., most preferably about 120° C. The reaction generally happens at a pressure from atmospheric pressure up till 10 bar, mots preferably at atmospheric pressure and until full conversion is reached.

[0038] The present invention also relates to a method of manufacturing 5-methyl-2-isopropylcyclohexanecarbonitrile or C11F by reaction of menthol with phosphorus tribromide (PBr3), phosphorus trichloride (PCl3), phosphorus triiodide (PI3), potassium iodide (KI) with acid catalysis, thionyl chloride (SOCl2) or thionyl bromide (SOBr2), followed by the cyanation of the obtained bromide, iodide or chloride, preferably with KCN and/or NaCN. This method has also never been reported in literature.