EP1856086A1

EP1856086A1 - Continuous method for the production of a dioxirane

Info

Publication number: EP1856086A1
Application number: EP06708576A
Authority: EP
Inventors: Mathieu Chabanas; Joaquim Henrique Teles; Gunnar Heydrich; William Ronald Sanderson
Original assignee: BASF SE
Current assignee: BASF SE
Priority date: 2005-03-02
Filing date: 2006-03-01
Publication date: 2007-11-21
Also published as: DE102005009468A1; US20080177092A1; CN101133044A; WO2006092403A1

Abstract

Disclosed is a continuous method for producing a dioxirane in a liquid phase in a reactor by oxidizing a ketone with a solution containing active oxygen in the presence of a buffer substance and stripping out the contained dioxirane with the aid of a stripping gas. The ketone, the solution containing active oxygen, the buffer substance, and the stripping gas are continuously fed to the reactor while a gas flow containing the dioxirane and a liquid flow are continuously withdrawn from the reactor. The inventive method is characterized in that the reactor is operated with a dwelling time of the liquid phase ranging between 1 min and 4 h and a standard condensate mass flow rate of at least 500 g/mol of the active oxygen used.

Description

Continuous process for the preparation of a dioxirane

The invention relates to a continuous process for the preparation of a dioxirane.

Dioxiranes, the simplest cyclic peroxides, are often used as neutral, highly reactive, and highly selective oxidants in organic chemistry. They have a number of advantages over other oxidizing agents, for example peracids: short reaction times, high yields, tolerance to hydrolysis-sensitive groups or simplified workup.

Dioxiranes as oxidizing agents can either be generated in situ or used as a solution in the starting ketone of the oxidation to dioxirane, the latter variant having the widest range of applications. Frequently solutions with a maximum of 1 to 1, 5 wt .-% dioxirane in the corresponding starting ketone, often acetone, used.

Dioxiranes are prepared by oxidation of ketones with solutions containing active oxygen, in particular solutions containing hydrogen monopersulfate, in the presence of a buffer substance. Dioxirane solutions are obtained from the reaction mixture by distillation in the starting ketone and / or by stripping with an inert gas, in particular helium, argon or nitrogen.

Publications by Murray (J. Org. Chem. 1985, 50, 2847), Eaton (J. Org. Chem. 1988, 53, 5353) or Adam (Chem. Ber. 1991, 124, 2377) describe the recovery of dimethyldioxirane. Solutions under semibatch conditions. While the stripping gas is often metered in continuously, at least one of the three reaction components of hydrogen monopersulfate, acetone and buffer substance is charged discontinuously. These processes have, inter alia, the following disadvantages: low dioxirane yields of not more than 5%, based on the hydrogen monopersulfate (in the above-cited publication by Adam) and complex process steps: monohydrogen persulfate is metered in as solid, the reaction mixture is heterogeneous, the reactor must be rinsed between two reactions.

WO 93/08144 describes an improved process for the preparation of dioxiranes, according to which the starting ketone is used in the gas phase with the stripping gas, and the oxidizing agent is an aqueous NaHSO ₅ solution (prepared by neutralization of Carscher acid with NaOH). Although these measures lead to a simplification and cheapening of the overall process, the yields of dimethyldioxirane based on the hydrogen monopersulfate are still unsatisfactory (about 5%, based on H ₂ SO ₅ ). It was accordingly an object of the invention to provide an improved continuous process for the preparation of dioxiranes, which in particular has a significantly higher yield based on the solution containing active oxygen and which is thus suitable for industrial use.

The solution consists in a continuous process for preparing a liquid phase dioxirane in a reactor by oxidation of a ketone with an active oxygen-containing solution in the presence of a buffer substance and stripping the resulting dioxirane with a stripping gas, the ketone containing the active oxygen-containing solution. solution, the buffer substance and the stripping gas are continuously fed to the reactor and continuously withdrawn from the reactor, a gas stream containing the dioxirane and a liquid stream, which is characterized in that the reactor with a residence time of the liquid phase between 1 min and 4 h and with a normalized condensate mass flow of at least 500 g / mol of active oxygen used.

It has been found that it is essential for the efficient implementation of the process for the preparation of dioxiranes, on the one hand a residence time of the liquid phase in the reactor between 1 min and 4 h, preferably between 20 min and 1 h, more preferably between 30 and 40 min at the same time to operate the reactor in such a way that the normalized condensate mass flow is at least 500 g / mol of active oxygen used.

The residence time of the liquid phase in the reactor designates, in a known manner, the volume of the liquid in the reactor, divided by the total volume flow of all liquid starting materials.

The normalized condensate mass flow is defined by the following equation:

Normalized condensate mass flow (g I mol) = - p "" ^{g of active} amino acid employed (mol Ih)

wherein M condensate (g / h) denotes the mass flow in g / h of the condensate, which can be obtained by condensing all condensable components from the gas stream withdrawn from the reactor, as condensable components all components having a boiling point above minus 20 ^0th C be understood at normal pressure,

and F _{emetztter Aktιver Sauterstoff (mol / h)} the amount flow in mol / h of the active oxygen used. Active oxygen is understood to mean all peroxide oxygen atoms detected by iodometric titration. Thus, 1 mol / h of potassium hydrogen peroxide or 1 mol / h of sodium hydrogen monopersulfate or 1 mol / h of hydrogen peroxide means 1 mol / h of active oxygen.

Instead of a single reactor, an arrangement with multiple reactors can be used. In this case too, the above definition applies to the normalized condensate mass flow, the condensate comprising the condensable fractions from all gas streams withdrawn from all the reactors forming the system and the mass flow of the active oxygen used as the sum of all the reactors forming the system active reactant-containing Eduktströme are to be used.

The normalized condensate mass flow can be controlled in particular via the process conditions of temperature, pressure, mass flow and composition of the feeds as well as mass flow of the stripping gas.

It has been found that increased yields are obtained when the normalized condensate mass flow at least 500 g of condensate / mol of active oxygen, preferably between 1000 and 10,000 g condensate / mol of active oxygen, particularly preferably between 2000 and 4000 g condensate / mol of active oxygen, is.

By the process according to the invention are educts - ketone, active solution containing oxygen and buffer substance - and the stripping gas supplied as fluid streams continuously.

In the present case, ketone is understood as meaning an aliphatic, aromatic, araliphatic, cyclic or acyclic compound or a mixture of aliphatic, aromatic, araliphatic, cyclic or ae cyclic compounds having at least one ketone function. This compound or mixture of compounds may also contain other functional groups, for example halogens, in particular chlorine or fluorine, hydroxyl groups, etc.

The ketone is preferably a substance or a mixture of substances having a boiling point below 100 ^° C. under normal pressure, in particular selected from the following list:

Acetone, 1,1,1-trifluoroacetone, butanone, diethyl ketone, cyclopentanone and cyclohexanone.

The ketone is particularly preferably acetone or 1,1,1-trifluoroacetone, in particular acetone. - A -

The ketone can be used as a pure compound in organic or aqueous solution or in the gas phase, as a mixture with the stripping gas.

The ketone acts both as a starting material and as a solvent for the product.

In particular, the active oxygen-containing solution is an aqueous or organic solution containing a hydrogen monopersulfate species or a precursor thereof.

The hydrogen monopersulfate species is in particular one or more substances selected from the following list: lithium, sodium, potassium, rubidium, cesium, tetraalkylammonium hydrogen monopersulfate, preferably sodium hydrogen monosulfate or potassium hydrogen monopersulfate.

As precursors for monohydrogen persulfate species it is possible to use compounds which are formed by reaction of peroxides with sulfuric acid, in particular Caro's acid and its salts or peroxodisulfuric acid and salts thereof.

Preferred solutions containing hydrogen monopersulfate are, for example, aqueous triple salt solutions, where triple salt is understood as meaning the salt [2 KHSO ₅ KHSO ₄ K ₂ SO ₄ ], known under the trade names Oxone®, Caroate® or Curox®, for adjusting the pH may be mixed with an acid or a base or aqueous, partially neutralized Caro's acid solutions, as described in WO 93/08144. The car- bonic acid can be prepared either in situ or ex situ, for example from sulfuric acid and hydrogen peroxide, in a H ₂ SO ₅ generator.

The concentration of the hydrogenmonopersulfate-containing solution is preferably> 10 ^{~ 5} mol of HSO ₅ VI, more preferably> 10 ^{~ 3} mol of HSO ₅ VI, in particular> 10 ^{~ 2} mol of HSO ₅ VI.

The buffer substance used is a basic compound, in particular a hydroxide, carbonate, bicarbonate, phosphate or hydrogen phosphate of alkali metals or alkaline earth metals, or mixtures thereof, particularly preferably sodium hydroxide, sodium bicarbonate or potassium bicarbonate.

Preferably, the buffer substance is added in a concentration and a mass flow, such that the ratio of base equivalent to active oxygen in the active

Oxygen-containing solution is between 0.25 and 5 mol / mol, preferably between 1 and 3 mol / mol. The composition and mass flow of the buffer substance solution can also be adjusted in a pH-dependent manner, in particular in such a way that the pH in the liquid phase in the reactor is between 4 and 12, preferably between 6 and 10, particularly preferably between 7 and 9 , The educts and the stripping gas are metered in continuously by the process according to the invention. The addition of educts, mixtures of educts and the stripping gas in portions is also understood to be continuous. The addition of educts, mixtures of educts or stripping gas in portions can be carried out simultaneously or sequentially. Two of the three educts ketone, active solution containing oxygen and buffer substance, or else all three educts can be supplied premixed, for example in a static mixer.

For the continuous performance of the process, all starting materials are advantageously supplied in liquid form. The concentrations of the educts are advantageously chosen so that there is no separation of solids in the reactor.

The process may be carried out in all types of reactors or combinations of reactor types which can continuously contact a liquid phase and a gas phase and provide mass transfer between gas phase and liquid phase. Preferred reactors are bubble columns (upright or horizontal), columns with packing or trays, it does not matter which phase is the continuous phase, also thin film or falling film evaporator and continuously operated stirred tank with gas inlet or loop reactors.

The operating temperature of the reactor or reactors may be between minus 50 ⁰ C and 100 ⁰ C, preferably between minus 10 and 70 ° C, more preferably between 0 and 30 ° C and the operating pressure between 0.1 mbar absolute and 50 bar absolute, preferably between 1 mbar absolute and 5 bar absolute, more preferably between 0.1 bar absolute and 1, 5 bar absolute and more preferably between 0.3 bar absolute and 1, 2 bar absolute, are selected.

The contact between liquid phase and gas phase in the reactor can take place in direct current, countercurrent or crossflow.

The withdrawn from the reactor gas stream can be partially or completely recycled to the reactor.

Also, the withdrawn from the reactor liquid can be partially or completely recycled into the reactor.

It is also possible to use any combination of reactors in a dioxirane production unit. Here, too, the standardized condensate mass flow from the entire production unit must be at least 500 g / mol of active oxygen. The withdrawn from the reactor or reactors dioxirane-containing gas phase can be further processed directly, for example, fed to another reactor.

In a preferred embodiment, however, the dioxirane-containing gas phase is partially condensed to obtain a dioxirane-containing solution and an exhaust gas, which is preferably at least partially recycled as stripping gas. In this case, the fraction of the recycled exhaust gas is preferably selected such that the oxygen concentration in the exhaust gas after the reactor does not exceed 12% by volume, preferably 9% by volume.

In one embodiment, the educts a defoamer which is inert under the reaction conditions, preferably a longer-chain alkane, especially n-dodecane, n-tridecane, n-tetradecane or a mixture thereof, single chain alcohols or silicone oils, particularly preferably n-dodecane together with the Added ketone.

In principle, all known defoamers (foam inhibitors) can be used. The amount of defoamer used is preferably at most 5 wt .-% of the ketone used, in particular at most 1 wt .-% of the ketone used.

Suitable stripping gas are all gaseous and inert substances or substance mixtures under reaction conditions. Preference is given to components or mixtures of components of the air, in particular nitrogen or nitrogen / oxygen mixtures.

In an advantageous embodiment of the method, the water content of the dioxirane-containing gas stream is reduced by distillation. Here, a water content of the claimed partial condensation of the components from the gas stream having a boiling point above obtained of from -20 ⁰ C liquid stream from below 1 wt .-%, preferably below 0.5 wt .-%, particularly preferably from 0.01 below Wt .-%, based on the total weight of the liquid stream achieved.

For this purpose, it is possible to introduce the gas stream directly into a corresponding distillation column, or else initially to feed it to a partial condensation, which is preferably carried out in two stages. Here, advantageously, a first capacitor (main capacitor) is operated by means of cold water at temperatures above 0 ⁰ C, and a post-condenser with brine at temperatures between -10 and -30 ⁰ C. Advantageously, the post-condensor can be placed directly on the main capacitor, so that the cold condensate of the post-condenser flows to the main capacitor and thus supports its effect.

In the partial condensation of the withdrawn from the reactor, dioxirane-containing gas stream, a solution of dioxirane in the starting ketone is obtained, which is a distillate onskolonne for the purpose of water depletion is supplied and non-condensable fractions, which are discharged as exhaust gas. From the distillation column, a top stream is withdrawn, containing the desired product dioxirane after partial condensation of the components having a boiling point above -20 ° X, a liquid stream having a water content <1 wt .-%, preferably <0.5 wt .-%, particularly preferably <0.01% by weight.

The distillation column is preferably designed in such a way that the stripping section has more than three, in particular 3 to 10 theoretical plates and the reinforcing section more than 10, in particular 10 to 25 theoretical plates.

In the process variant in which the withdrawn from the reactor, dioxirane-containing gas stream is introduced directly into the distillation column for the purpose of water removal, the withdrawn from the distillation column overhead stream is partially condensed, preferably in two stages, operated in a water above 0 ⁰ C main condenser and a Brine at -10 to -30 ° C operated after-condenser, to obtain a solution of the dioxirane in the starting ketone and wherein the non-condensable fractions are discharged as exhaust gas.

In this process variant, the distillation column is designed as a buoyant column, preferably with at least 5 theoretical plates. Higher levels increase the separation. So 10 to 20 theoretical plates are to be preferred. The working pressure in the column does not differ significantly from the pressure at which the reactor is operated. In order to keep the loss of ketone small, it is therefore necessary to operate the condenser at the top of the column at low temperatures, preferably at temperatures below 0 ⁰ C, preferably at temperatures between minus 10 and minus 30 ⁰ C.

A particularly cost-effective operation can be achieved if it is condensed with at least two capacitors at different temperature levels. For example, the first condenser can be operated with cold water at temperatures above 0 ° C, and a downstream condenser with brine at temperatures down to -30 ⁰ C. The post-condenser can be placed directly on the main condenser, so that the cold condensate from the post-condenser first capacitor flows and supports its effect.

Regardless of the process variant, there are basically no restrictions with regard to the usable separation-active internals in the distillation column. For this purpose, both random packings and also ordered packings or trays are suitable.

In order to keep the pressure loss in the distillation column low, packed beds, but also ordered sheet or tissue packings, preferably with a specific surface of 100 to 750 m ² / m ³ , particularly preferably from 250 to 500 m ² / m ³ , particularly suitable.

In a particularly advantageous variant of the method, not only is the dioxirane-containing gas stream from the reactor worked up by distillation, but also the liquid discharge from the reactor is fed to a stripping column which has the task of separating off any product of value present therein and a large part of the starting ketone and separating the product Reactivate reactor for the production of dioxirane. The stripping column can have a bottom evaporator which is operated so that the starting ketone evaporates and acts as a stripping gas, but it can also be operated with an inert gas as the stripping gas. The stripping column should have at least 5, preferably 5 to 15 theoretical plates.

From the stripping column, a stream of dioxirane and largely of starting ketone is withdrawn, which is discharged into the wastewater. The vapor stream from the stripping column is preferably recycled uncondensed into the reactor for the preparation of the dioxirane.

In an advantageous embodiment, the distillation column for Wasserabrei- chung and the stripping column may be formed as a single apparatus, wherein the distillation and the Strippteil are separated from each other by a liquid collecting tray. The liquid collecting on the liquid collecting tray is advantageously recycled into the reactor for the production of dioxirane.

The collecting bottom has suitable devices, in particular chimneys, via which the vapor can rise from the stripping part into the distillation part.

In a further preferred embodiment of the process, the dioxirane-containing gas or liquid stream, which has preferably been depleted in water, is fed to an oxidation reactor in which a substrate having at least one oxidizable functional group is preferably continuously oxidized by the dioxirane, this reducing to the starting ketone is separated from the oxidized substrate, for example, by distillation in a falling film evaporator or a distillation column and in the reactor for the production of the dioxirane is recycled. There are no restrictions with regard to the reactor type or the combination of reactors for the oxidation reaction with dioxirane. Particularly suitable are continuously operated stirred tanks or tube reactors, if the dioxirane is used as a liquid solution after partial condensation. If the dioxirane-containing gas stream is used directly, without partial condensation, bubble columns are particularly suitable. Oxidizable substrates may generally be compounds having at least one oxidizable functional group. Preference is given to substrates having carbon-carbon double bonds, such as alkenes, enolates, acyl, alkyl or silyl enol ethers. Further preferred are substrates with sulfur, nitrogen or phosphorus-containing functional groups, such as sulfides, sulfoxides, amines, amides, hydroxylamines, phosphenes or phosphites.

The substrates mentioned can be used as a pure compound, as a mixture or as a solution in a suitable solvent.

The invention will be explained in more detail below with reference to a drawing and exemplary embodiments.

The single figure shows the schematic representation of a preferred system for carrying out the method according to the invention.

A reactor R for the preparation of dioxirane is a ketone or ketone / water mixture (stream 1), potassium hydrogen monopersulfate solution (stream 2) and sodium bicarbonate solution (stream 3) and fed via a frit stripping gas (stream 4). From the reactor, a gaseous overhead stream 5a is withdrawn, containing the dioxirane, stripping gas, ketone and water, and introduced into the lower region of a distillation column D. The bottom effluent, stream 5b, from the distillation column D, is recycled to the reactor R. In addition, a water-rich liquid stream 6 is withdrawn from the reactor R, containing water, salts, residues of ketone and traces of the desired product dioxirane. Stream 6 is introduced into a stripping column D3 for the removal of the residues of the ketone. From the stripping column D3, a ketone-containing vapor stream 14 is withdrawn, containing the stripping gas, ketone, traces of dioxirane and traces of water, which is recycled in the illustrated preferred embodiment as stream 16 in the reactor R. From the stripping column D3, a bottom stream 15 is withdrawn, containing water and salts, which is discharged into the wastewater.

From the distillation column D, a dehydrated, dioxirane-containing vapor stream 7a is withdrawn, comprising stripping gas, ketone and dioxirane, condensed in a condenser K, partly as reflux 7b re-applied to the distillation column D and otherwise as dehydrated dioxirane-containing liquid stream 8, containing ketone and dioxirane , are introduced into the oxidation reactor R2 for the oxidation of a substrate 10, optionally in the presence of a solvent. The non-condensable gas stream 9 from the condenser K is partially discharged from the process (stream 18) and otherwise recycled to the stripping column D3 for the separation of the ketone residues. The effluent from the oxidation reactor R2, stream 11, is separated in an apparatus D2, which may be a distillation column or a falling film evaporator, into a crude product 12 containing the oxidized one Substrate and optionally solvent and a top stream 13 containing the ketone, which is recycled to the reactor R to produce the dioxirane.

example 1

One operated at 20 ⁰ C and 0.3 bar absolute bubble column with an inner diameter of 40 mm, a height of 630 mm and an empty tube volume of about 0.79 I, the following components were continuously added separately to the lower third of the bubble column:

1) a 9.75 wt .-% aqueous potassium hydrogen monopersulfate solution with a mass flow of 95.2 g / h, corresponding to 0.061 mol / h of hydrogen monopersulfate, prepared from the triple salt [2 KHSO ₅ KHSO ₄ K ₂ SO ₅ ] and water .

2) 158.7 g / h of a 7.06% by weight aqueous sodium bicarbonate solution,

3) 414.2 g / h of a 57 wt .-% acetone solution in water containing 400 ppm of n-dodecane as an antifoam and

4) via a frit 180 Nl / h of nitrogen.

The potassium hydrogen monopersulfate content of the aqueous solution was determined shortly before use by iodometric titration. 478 g / h of a water-rich liquid and a dioxirane-containing gas phase were continuously withdrawn from the bubble column. This gas phase was run through a very efficient, operated at -30 ⁰ C cooler. The cooler was dimensioned so that components with a boiling point above - 20 ° C could be almost completely condensed. After the condensation, 173.5 g / h of a dioxirane-containing solution containing 0.69% by weight of dimethyldioxirane and 8.3% by weight of water and a gaseous phase were obtained.

The Dimethyldioxiran yield was 26.5%, based on the hydrogen monopersulfate.

The content of liquid in the bubble column was measured at the end of the experiment and was 60% by volume. this corresponds to a residence time of the liquid phase in the reactor of about 43 min.

The normalized condensate mass flow was about 2844 g of condensate / mol of active oxygen. Example 2

The same bubble column as described in Example 1 were subjected to the same conditions of temperature and pressure

1) 90.0 g / h of a 5.74 wt .-% aqueous potassium hydrogen monopersulfate solution, corresponding to 0.034 mol / h of hydrogen monopersulfate, in the same manner as under

Example 1 was prepared,

2) 155.7 g / h of a 3.53% strength by weight aqueous sodium bicarbonate solution,

3) 413.8 g / h of a 57% strength by weight aqueous acetone solution containing 400 ppm of Dodecane as defoamer and

4) via a frit 180 Nl / h of nitrogen.

472.7 g / h of a water-rich liquid and a dioxirane-containing gas phase were continuously withdrawn from the bubble column. This gas phase was partially condensed as described in Example 1 to obtain 172.7 g / h of a Dimethyldioxiran enthal- containing solution with 0.46 wt .-% Dimethyldioxiran and a gas phase.

This corresponds to a dimethyldioxirane yield of 31.5%, based on hydrogen monopersulfate.

The proportion of liquid in the bubble column was measured at the end of the experiment with 62 vol .-%, corresponding to a residence time of the liquid phase in the reactor of about 45 min.

The normalized condensate mass flow was in his example about 5080 g condensate / mol of active oxygen.

Example 3

The following components were metered in continuously at the upper end of the bubble-cap tray column to a glock-bottom column operated at 25 ° C. and 1 bar absolute with 8 plates, a height of 800 mm and an internal diameter of 50 mm:

1) 23.9 g / h of a 9.59% by weight aqueous solution of potassium hydrogen monopersulfate corresponding to 0.015 mol / h of hydrogen monopersulfate prepared in the same manner as in Example 1, 2) 39.5 g / h of a 7.06 wt .-% aqueous sodium bicarbonate solution and

3) 85.6 g / h of a 57% by weight aqueous acetone solution.

At the same time, 200 Nl / h of nitrogen was metered in at the lower end of the bubble-cap tray column.

96.8 g / h of a water-rich liquid and from the upper region thereof a di-oxirane-containing gas phase were taken continuously from the bottom of the bubble tray. The gas phase was passed through a condenser according to Example 1 to give 44.1 g / h of a dimethyldioxirane-containing solution, corresponding to 0.56% by weight of dimethyldioxirane, and a gas phase. The dimethyldioxirane yield based on potassium hydrogen monopersulfate was 22%.

In this example, the normalized condensate mass flow was about 2940 g of condensate / mole of active oxygen.

Example 4

On the upper part of the bubble column described in Example 1, a distillation column having an inner diameter of 30 mm, a height of 370 mm, filled with 5 x 5 mm Glasraschigringen placed. The reflux ratio was controlled by the temperature of a cooler on the top of the column (-10 ⁰ C). The reaction was carried out under the same operating conditions as described in Example 1, that is to say at 20 ^° C. and 0.3 bar absolute.

At the lower third of the bubble column, the following components were continuously fed:

1) a 9.84 wt .-% aqueous potassium hydrogen monopersulfate solution with a mass flow of 94.8 g / h, corresponding to 0.0613 mol / h of hydrogen monopersulfate, prepared from the triple salt [2 KHSO ₅ KHSO ₄ K ₂ SO ₅ ] and water,

2) 157.3 g / h of a 7.06% by weight aqueous sodium bicarbonate solution,

3) 414.9 g / h of a 57% strength by weight acetone solution in water containing 400 ppm of dodecane and

4) via a frit 180 Nl / h of nitrogen. 152.0 g / h of a water-rich liquid and a dioxirane-containing gas phase were continuously withdrawn from the bubble column. The gas phase was run over the same cooler as described in Example 1. After partial condensation in the condenser, 173.5 g / h of a dimethyldioxirane-containing solution containing 0.72% by weight of dimethyldioxirane (determined by iodometric titration) and 0.6% by weight of water (determined by standard Karl Fischer titration), and a non-condensable constituent-containing gas phase.

The dimethyldioxirane yield was 24%, based on the hydrogen monopersulfate used.

The liquid fraction in the bubble column was measured at the end of the experiment and was 64% by volume; this corresponds to a residence time of the liquid phase in the reactor of about 46 min.

The normalized condensate mass flow was about 2490 g condensate / mol active oxygen.

Comparative example

In a semi-batch process, 635 g of water, 380 g of acetone and 145 g of sodium bicarbonate were placed in a 4L four-necked flask.

The heterogeneous (liquid / solid) mixture was cooled to 0 to 5 ° C.

At this temperature, the triple salt [2 KHSO ₅ KHSO ₄ K ₂ SO ₅ ], 300 g, corresponding to about 0.976 mol of hydrogen monopersulfate as a solid was added slowly and in portions over a solids feeder.

The mixture was warmed to room temperature and then distilled off with vigorous stirring at 100 mbar and 25 ° C a dimethyldioxirane-containing solution.

The dimethyldioxirane solution was isolated by means of a series of cold traps cooled to -78 ° C.

Within 80 minutes, 292.1 g of solution could be isolated after combining the fractions obtained. The iodometric titration of this solution gave 0.93% by weight of dimethyldioxirane, corresponding to a total of 0.0367 mol of dimethyldioxirane. This corresponds to a dimethyldioxirane yield based on the hydrogen monopersulfate used of about 3.8%. The comparative example was prepared analogously to the instructions of Adam in Chem. Ber. 1991, 124, 2377. The mean normalized condensate mass flow was 299 g of condensate / mol of active oxygen.

Claims

claims

1. A continuous process for the preparation of a dioxirane in a reactor (R) by oxidation of a ketone (1) with an active oxygen-containing solution (2) in the presence of a buffer substance (3) and stripping the resulting dioxirane with a stripping gas (4), wherein the ketone (1), the active oxygen-containing solution (2), the buffer substance (3) and the stripping gas (4) are continuously fed to the reactor (R) and from the reactor (R) continuously a gas stream (5) containing the Dioxirane, as well as a liquid stream (6) are deducted, characterized in that the reactor (1) is operated with a residence time of between 1 min and 4 h and with a normalized condensate mass flow of at least 500 g / mol of active oxygen used.

2. The method according to claim 1, characterized in that the normalized condensate mass flow is between 1000 and 10,000 g of condensate per mole of active oxygen, preferably between 2000 and 4000 g of condensate per mole of active oxygen.

3. The method according to claim 1 or 2, characterized in that the ketone (1) is an aliphatic, aromatic, araliphatic, cyclic or acyclic compound or a mixture of aliphatic, aromatic, araliphatic, cyclic or a-cyclic compounds having at least one ketone function ,

4. The method according to claim 3, characterized in that the ketone (1) is a substance or a mixture of substances having a boiling point of below 100 ⁰ C at atmospheric pressure, in particular selected from the following list: acetone, 1,1,1- Trifluoroacetone, butanone, diethyl ketone, cyclopentanone and cyclohexanone.

5. The method according to claim 4, characterized in that the ketone (1) is acetone.

6. The method according to any one of claims 1 to 5, characterized in that the active oxygen-containing solution (2) is an aqueous or organic solution containing a hydrogen monopersulfate species or a precursor thereof.

7. The method according to claim 6, characterized in that the hydrogen monopersulfate species one or more substances selected from the following list: lithium, sodium, potassium, rubidium, cesium, Tetraalkylammoni- umhydrogenmonopersulfat, preferably sodium hydrogen monopersulfate and potassium - hydrogen monopersulfate.

8. The method according to claim 6, characterized in that as precursors for hydro gen-monopersulfate species compounds are used which are formed by reaction of peroxides with sulfuric acid, in particular Caro's acid and its salts, peroxodisulfuric acid and salts thereof.

9. The method according to any one of claims 6 to 8, characterized in that the concentration of hydrogenmonopersulfathaltigen solution of hydrogen monopersulfate species> 10 ^{~ 5} mol / l, preferably> 10 ^{~ 3} mol / l, more preferably> 10 ^{~ 2} mol / l, is selected.

10. The method according to any one of claims 1 to 9, characterized in that as buffer substance (3) a basic compound, especially a hydroxide, carbonate, bicarbonate, phosphate or hydrogen phosphate of an alkali or alkaline earth metal, or mixtures thereof, more preferably sodium hydroxide, sodium - Hydrogen carbonate or potassium bicarbonate is used.

11. The method according to claim 10, characterized in that the buffer substance (3) is added in a concentration and a mass flow, such that the ratio base equivalent to active oxygen in the active oxygen-containing solution between 0.25 and 5 mol / mol, preferably between 1 and 3 mol / mol.

12. The method according to claim 10 or 11, characterized in that the composition and the mass flow of the buffer substance (3) are adjusted pH-dependent, in such a way that the pH in the liquid phase in the reactor (R) between 4 and 12, preferably between 6 and 10, more preferably between 7 and 9, is located.

13. The method according to any one of claims 1 to 12, characterized in that the reactor (R) at a pressure between 0.1 mbar absolute and 5 bar absolute, preferably between 0.1 and 1.5 bar absolute, more preferably between 0 , 3 and 1, 2 bar absolute and a temperature between -50 and + 100 ° C, preferably between -10 and 70 ⁰ C, more preferably between 0 and 30 ⁰ C, is operated.

14. The method according to any one of claims 1 to 13, characterized in that as stripping gas (4) a component or a mixture of components of the air, in particular nitrogen or nitrogen / oxygen mixtures are used.

15. The method according to any one of claims 1 to 14, characterized in that the reactor (1) is a bubble column, a column with packing or trays, a thin film or falling film evaporator, a stirred tank or a loop reactor.

16. The method according to any one of claims 1 to 15, characterized in that from the reactor (1) withdrawn dioxirane-containing gas phase (5) is partially condensed, wherein all components condensed with a boiling point above minus 20 ⁰ C at atmospheric pressure from the gas phase to obtain a dioxirane-containing solution (15) and an exhaust gas (11), which is preferably recycled as stripping gas (4).

17. The method according to any one of claims 1 to 16, characterized in that the part of the stripping gas (4), which is recycled, is selected so that in the exhaust gas (11) after the partial condensation, an oxygen content of <12 vol .-% , preferably <9 vol.%, remains.

18. The method according to any one of claims 1 to 16, characterized in that the oxidation of the ketone (1) with the active oxygen-containing solution (2) in the presence of a defoamer, in particular a longer-chain n-alkane, preferably n-dodecane, n- Tridecane, n-tetradecane, or a mixture thereof, a longer-chain alcohol or silicone oil.

19. The method according to any one of claims 1 to 18, characterized in that the dioxirane-containing gas stream (5a) from the reactor (R) directly in a distillation column (D) is introduced, from which a top stream (7a) containing the Value product dioxirane is withdrawn, which after partial condensation of the components having a boiling point above minus 20 ° C results in a liquid stream (8) containing less than 1 wt .-% water, preferably less than 0.5 wt .-% water, particularly preferred contains less than 0.01% by weight of water, based on the total weight of the liquid stream.

20. The method according to any one of claims 1 to 19, characterized in that the liquid stream (6) from the reactor (R) in a stripping column (D3), preferably in the upper region, is introduced, wherein the stripping column (D3) at least 6th , preferably 5 to 15 theoretical plates, and that from the stripping column (D3), a bottom stream (15) is separated, which is largely free of Ausgangske- ton, and is discharged into the wastewater and a top stream (14), which preferably uncondensed is recycled to the reactor (R) to produce the dioxirane.

21. The method according to claim 19 or 20, characterized in that the dioxirane-containing overhead stream (7a) is preferably partially condensed in two stages to give a liquid solution (8) of the dioxirane in the starting ketone and wherein the non-condensable portions of the top stream (7a) partially as Discharged exhaust gas (18) and recycled as stream (9) in the stripping column (D3) otherwise.

22. The method according to any one of claims 1 to 18, characterized in that the dioxirane-containing gas stream (5a) from the reactor (R) is first condensed preferably in two stages, to obtain a liquid solution of the dioxirane in the starting ketone, that of a distillation column (D) is supplied, from which a top stream

(7a) is withdrawn, containing the desired product dioxirane and wherein by partial condensation of the components from the overhead stream having a boiling point above minus 20 ° C, a liquid stream (8) having a water content of <1 wt .-%, preferably <0.5 wt .-%, particularly preferably <0.01 wt .-%, based on the total weight of the liquid stream is recovered.

23. The method according to claim 22, characterized in that the distillation column (D) has a stripping section with at least 3, preferably 3 to 10 theoretical plates and a reinforcing section with at least 10, preferably 10 to 25 theoretical plates.

24. The method according to any one of claims 19 to 23, characterized in that the dioxirane-containing gas stream (7a) is fed directly or after partial condensation of an oxidation reactor (R2) in which a substrate having at least one oxidizable dable functional group by the dioxirane preferred is continuously oxidized, wherein the dioxirane is reduced to the starting ketone, which is separated from the oxidized substrate and recycled to the reactor (R).