WO2015071371A1

WO2015071371A1 - Process for preparing bis(alkanesulfonyl) peroxide by oxidation

Info

Publication number: WO2015071371A1
Application number: PCT/EP2014/074514
Authority: WO
Inventors: Timo Ott; Ingo BIERTÜMPEL; Klaus Bunthoff; William Robert Hugh WRIGHT; Alan Richards
Original assignee: Grillo Chemie Gmbh
Priority date: 2013-11-13
Filing date: 2014-11-13
Publication date: 2015-05-21

Abstract

A process for preparing bis(alkanesulfonyl)peroxide of the formula (I) in which ALK represents an alkyl group, by the oxidation of alkanesulfonic acids, characterized in that said oxidation is effected by electrolysis in which the formation of ozone is reduced or prevented.

Description

Process for Preparing BisfalkanesulfonyO peroxide by Oxidation

The present invention relates to a process for preparing bis(alkanesulfonyl) peroxide by oxidation. Bis(alkanesulfonyl) peroxide can be used, in particular, as an oxidant and free- radical initiator. In particular, applications in free-radical polymerization are to be pointed out. The production of free radicals is preferably effected thermally, photolytically, metal-catalyzed, or induced by microwaves. Applications as an organic reagent for introducing the alkylsulfonic acid group and the peroxoalkylsulfonic acid group are also possible. Also, applications as an explosive can be conceived .

It has been found that using a classical electrolytic cell for sulfonyl-peroxide- production leads to non-pure products. It has been discovered that - similar to literature reported reactions (DE69106972T2) - ozone is generated during the electrolysis of sulfonic acids which contain traces of water. Since ozone is a very reactive agent many different by-products were formed . Some of them are the highly toxic and cancerogenic alkyl-sulfate derivatives. For many new applications it is necessary to use very pure bis(alkanesulfonyl) peroxide to avoid side-reactions and the formation of toxic compounds (e.g . high-tech materials, starter for very sensitive radical reactions, applications in synthesis for pharmaceutical compounds).

EP 0 273 097 Al discloses that bis(alkanesulfonyl) peroxide (RSO₂-0-0-0₂SR) is prepared in a continuous process by electrolyzing the corresponding alkanesulfonic acid at an elevated temperature (to keep the peroxide product in solution ) in a continuous-flow electrolysis cell, removing the solution from the electrolytic cell, cooling the solution to precipitate the peroxide product, and recycling the supernatant alkanesulfonic acid back to the cell .

US 2,619,507 A discloses that di(methanesulfonyl)peroxide, CH₃S0₂-0-OS0₂CH₃, is prepared by the electrolysis of methanesulfonic acid, CH₃S0₂OH in water. The compound is a more active catalyst for the polymerization of vinylidene chloride at low temperatures than other peroxides heretofore employed for that purpose.

Christopher J. Myall and Derek Pletcher, in J . Chem. Soc, Perkin Trans. 1, 1975, 953-955 report about a simple, safe, and high yield preparation of bismethylsulphonyl peroxide by constant current oxidation of a solution of sodium methanesulphonate in anhydrous methanesulphonic acid . The reactions of bismethylsulphonyl peroxide with benzene, naphthalene, and other aromatic hydrocarbons are briefly considered .

R. N. Haszeldine et al .in J. Cehm. Soc, Part A 1. Jan. 1964, pp 4901-4907 report about properties and reactions of dimethansulphonyl peroxide.

One important representative of the bis(alkanesulfonyl) peroxide class of compounds

is its methyl derivative bis(methanesulfonyl) peroxide with the CAS number 1001- 62-3 and the CAS name methanesulfonic acid methylsulfonyloxy ester. Its IUPAC name is methylsulfonyloxy methanesulfonate, and it has the following formula :

It is the object of the present invention to provide a simple process for preparing bis(alkanesulfonyl) peroxide compounds that enables the preparation of the compound in high purity and high yield . The object of the invention is achieved by a process for preparing bis(alkanesulfonyl) peroxide of the formula

in which ALK represents an alkyl group, by the oxidation of alkanesulfonic acids, characterized in that said oxidation is effected by electrolysis in which the formation of ozone is reduced or prevented by using inert, oxygen- free conditions.

According to the process according to the invention, the electrolysis of the alkanesulfonic acid, especially of an anhydrous alkanesulfonic acid, is typically performed under inert and/or anhydrous conditions or a solution of it in a non- reactive solvent. It is advantageous that the complete apparatus is purged with non-reactive protective/inert gasses like noble gasses or nitrogen. In particular, reaction conditions free of oxygen-, water and carbondioxide are employed which lead to a very pure product. No by-products as the highly toxic alkanesulfates could be determined by standard analytical methods (NMR, IR, UV, MS). Further- more, inert materials, such as glass, ceramics and Teflon prohibit the formation of unwanted products.

The group ALK in the general formula represents, in particular, a methyl, ethyl, propyl or butyl group.

According to the invention, the inert conditions can be produced by a protective gas, especially dry nitrogen. Other protective gases, such as noble gases, are also considered .

In the electrolysis during the process according to the invention, a current of from 5 A to 20 A is to be used . It is clear to the skilled person that voltage and amperage are dependent on each other. In particular addition of an inert conducting salt increases the amperage at the same current and results in shorter reaction times (Fig . 2, Chart 3, Table 1).

During the electrolysis according to the process of the invention, a voltage of from 1 V to 10 V, especially from 3 V to 5 V, is to be applied . It has been discovered that the amount of by-products increases when higher voltages are used . (Fig . 1)

Typically, the electrolysis according to the invention is performed for a period of from 3 h to 12 h.

In another embodiment of the process according to the invention, the alkanesulfonic acid is supplied to the electrolysis continuously from a reservoir vessel temperature-controlled at from -5 °C to 10 °C.

The invention is further illustrated by the following Example relating to the preparation of bis(methanesulfonyl) peroxide.

Fig . 1 : Measurement of DMSP synthesis with alternative power inputs.

Experimental details : Approximately 1.5 kg MSA (98%) was used in each reaction . Reaction temperature was maintained between 25 °C and 30 °C. N₂ was bubbled through the MSA during the reaction . DMSP concentration was measured using NaI/Na₂S₂0₃ titrations and using N MR to analyse the purity

Fig . 2 : Measurement of Conductivity vs Amps

Evidently, to enable more efficient DMSP synthesis, strategies must be developed to prevent the MSA conductivity from decreasing . With this goal in mind, a range of additives, have been added to MSA prior to electrolysis (Fig . 3).

Fig 3 : Electrolysis of MSA containing NaC SCH^using the flow cell

Initially, small amounts of Na0₃SCH₃ were added to MSA (1.5 kg) during electrolysis at 5 volts (blocks). Addition of between 5 mg and 575 mg of Na0₃SCH₃ did not result in an increase in current, which remained at 8.75 amps. However, at the end of the experiment, 10 g of Na0₃SCH₃ was added to the reaction mixture. This resulted in an increased current of 9.3 amps, and a slight increase in the rate of DMSP synthesis. Hence, the reactions were repeated, but with significantly higher Na0₃SCH₃ loadings of 3.9 wt% and 6.0 wt% (diamonds and triangles). The use of such additives resulted in significantly increased DMSP yields. By using 3.9 wt% Na0₃SCH₃, a solution with approximately 54 g/kg (or approx. 80 g/L) was pro- duced, significantly more than that obtained without an additive.

Table 1 : Additives used to enhance DMSP synthesis

Example:

An electrolytic cell with a temperature-control jacket is charged with 100 ml of methanesulfonic acid . A platinum sheet is used as the anode, and a stainless steel sheet is used as the cathode. Electrolysis is performed for 5 hours with 5 V and 12 A, maintaining the temperature of the solution at about 10 °C. A solution containing about 80 g of bis(methanesulfonyl) peroxide per liter is obtained .

The solution can be employed as such, or the bis(methanesulfonyl) peroxide can be obtained as an insoluble white explosive solid by cooling and adding water. As alternatives to the platinum sheet, electrodes made of other materials are also possible, especially platinum-plated metals (e.g ., platinum-plated titanium, iron or any other metal, alloy or conductive material) and other precious metals (e.g . , palladium, iridium, rhodium, ruthenium).

Claims

C L A I M S :

1. A process for preparing bis(alkanesulfonyl) peroxide of the formula

in which ALK represents an alkyl group, by the oxidation of alkanesulfonic acids, characterized in that said oxidation is effected by electrolysis in which the formation of ozone is reduced or prevented.

2. The process according to claim 1, characterized in that the electrolysis of the alkanesulfonic acid, especially of an anhydrous alkanesulfonic acid, is performed under inert and/or anhydrous conditions.

3. The process according to claim 1 or 2, characterized in that ALK is a methyl, ethyl, propyl or butyl group.

4. The process according to claim 2, characterized in that said inert conditions are produced by a protective gas, especially dry nitrogen.

5. The process according to at least one of claims 1 to 4, characterized in that a current of from 5 A to 20 A is used in the electrolysis.

6. The process according to at least one of claims 1 to 5, characterized in that a voltage of from 1 V to 10 V, especially from 3 V to 5 V, is applied during the electrolysis.

7. The process according to at least one of claims 1 to 6, characterized in that the electrolysis is performed for a period of from 3 h to 12 h. The process according to at least one of claims 1 to 7, characterized in that said alkanesulfonic acid is supplied to the electrolysis continuously from a reservoir vessel temperature-controlled at from -5 °C to 20 °C.