DE1643688A1 - Process for the oxidation of olefins - Google Patents

Description

Process for the oxidation of olefins The invention relates to a process for the oxidation of olefins.

British patent specification 898 790 describes a method of manufacture of aldehydes, ketones and / or acids which correspond to the aldehydes, where a Hydrocarbon containing an olefinic double bond in a neutral one to acidic medium with molecular oxygen and / or an active oxidizing agent, Water and a salt of palladium, iridium, ruthenium, rhodium or platinum in Presence of a redox system is merged.

This patent specification also states in general terms: that quinones / hydroquinones of the benzene series belong to the suitable redox systems.

Taking palladium chloride as the typical catalyst and ethylene as the typical olefin for ease of illustration, the following reactions should occur using this system: PdOl2 + CH2 = CH2 + H20> Pd + 2HCl + CH3. CHO Pd + 2HCl + quinone> PdCl2 + hydroquinone Hydroohinone + 1/2 O2 quinone + H20 From this it can be seen that the quinone / hydroquinone system must be present in the chlorine standard at the beginning and is reduced to hydroquinone in the course of the reaction and then regenerated.

It should be noted that British patent specification 898 790 states that the process takes place in a neutral or acidic medium. This results Difficulties in regeneration because of the generally alkaline conditions are preferred for the oxidation of hydroquinones to quinones.

Since the olefin oxidation preferably takes place in a neutral or acidic Medium and the regeneration of the used quinone in an alkaline medium takes place, the hydroquinone would have to change from a neutral or acidic medium to an alkaline one Medium and the regenerated quinone from an alkaline to a neutral or acidic one Medium to be transferred. There are currently no economic procedures for this measure has been described.

In addition, there are many quinones, especially those in the o series, eo sensitive to further oxidation that the oxidation of hydroquinone must be run under precisely regulated conditions.

For these reasons, among other things, the use of the quinone / hydrochloride system was established not preferred. The syetem, which partly pre-soaks because of its easy regeneration is the copper (II) chloride / copper (I) chloride system. This system will despite preferred to the fact that it requires an extremely acidic and corrosive medium, in which handling problems arise only through the use of expensive metals or alloys can be dissolved The corrosive nature of the medium results from the acidity and the salts it contains. The system has the other Disadvantage that chlorinated Hydrocarbons as unexpected by-products are formed.

The previously preferred cupric chloride / cupric chloride system thus has the advantage of being easy to regenerate on the one hand, but on the other hand the disadvantages1 being extremely corrosive and forming chlorinated by-products, while the quinone / hydroquinone systems generally have the advantage that they do not are highly corrosive, but the flat parts make them difficult to regenerate and are very responsive.

Regardless of whether the redox system is copper (II) chloride / copper (I) chloride or quinone / hydroquinone is used, is described in British Patent 898 790 stated that the process was carried out at a temperature in the range of 50 to 1600C is carried out.

It has now been found that a selected group of o-hydroquinones of the general formula in which R1, R2, R3 and R4 stand for hydrogen atoms or alkyl radicals, at least two of the groups R1, R2, R3 and R4 being tertiary alkyl radicals which are oxidized in an alkaline, neutral or acidic, largely organic, non-corrosive medium that the quinones obtained are resistant to further oxidation beyond the ohinone stage, and that the system is a very suitable redox system for the regeneration of a catalyst which is used for the oxidation of olefins and that the oxidation can be carried out in an improved manner.

The redox system is more active than the well-known redox system, and this one Increased activity can be beneficial in one way or two ways be exploited. The regeneration of the olefin oxidation catalyst and the oxidation the olefins can be carried out at lower temperatures than before considered necessary, or the reaction rate may be normal Temperatures are increased. Of course, a lowering of the reaction temperature is necessary a slower response and vice versa, but by carefully approaching that Optimum it can be possible both eu lower reaction temperatures than auoh to arrive at higher reaction rates than in the known processes.

Each of these effects increases the purity of the olefin oxidation product increased as each the degree of olefin isomerization in relation to is reduced to the extent of olefin oxidation that normally occurs, so that consequently the breadth of the product spectrum is reduced. It may be that the quantities of the products of both olefin oxidation and isomerization increase, but the increase in the former is greater than the increase in the latter.

The invention accordingly relates to the oxidation of olefins to aldehydes or ketones by a process which is characterized in that the olefin is treated with a salt of a metal from Group VIII of the Periodic Table with an atomic number of 44 to 78 in the presence of an o-quinone the general formula in which R1 to R4 have the meaning already mentioned, an organic solvent and water are brought together, the o-quinone being reduced to the corresponding hydroquinone, the hydroquinone removed from the olefin oxidation zone, the hydroquinone in the presence of a salt and / or a complex of a Heavy metal and an organic solvent is oxidized to the corresponding quinone, the quinone is removed from the hydroquinone oxidation zone and the quinone is returned to the olefin oxidation zone.

The oxidation of the olefins can take place at a temperature in the range of 20 to 1800C and under a pressure in the range of t to 100 atmospheres will. The oxidation of the hydroquinone can be done by adding oxygen or an oxygen-containing gas at a temperature in the range from 20 to 1200C and a pressure in the range of 1 to 100 atmospheres, with higher Pressures in this range are preferred when gases containing oxygen, e.g. air, The hydroquinone can be used by extraction with a non-polar solvent, e.g. an aromatic or aliphatic hydrocarbon. Benzene is particularly suitable as a solvent. It may sometimes be necessary be to add water.

However, it is preferred as a solvent in which the olefin is oxidized an aqueous organic solvent is used that has a critical solution temperature in the range of 20 to 1000C. In this case, the olefin oxidation is at a Temperature made above the critical solution temperature. The critical one Solution temperature is the temperature below which the solvent turns into more separates as one phase, and above which the solvent is present as one phase. Below the critical solution temperature, the solvent separates at one Method ema! 3 this preferred feature of the Invention in two Phases, with the less polar phase taking up most of the o-benzohydroohinone contains, so that separation is possible.

Contains the aqueous organic solvent for olefin oxidation Water and a polar and a less polar organic liquid and has one critical solution temperature in the range from 20 to 100 ° C. As polar liquids lower alcohols, ketones, nitriles, amides, sulfoxides and carboxylic acids are suitable. Suitable less polar liquids are the aliphatic and aromatic hydrocarbons. The critical solution temperature is determined by the proportions of the components The system is determined below the critical solution temperature that divides Solvent in two phases, namely a polar layer and a less polar one Layer. The hydroquinone is mainly found in the less polar layer, while the Group VIII metal salt remains in solution in the polar layer.

According to a further feature, the invention thus relates to the oxidation of olefins to aldehydes or ketones by a process which is characterized in that a) the olefin is treated with a salt of a metal from Group VIII of the Periodic Table with an atomic number of 44 to 78 in Presence of an o-quinone of the general formula in which R1 - R4 have the meaning already mentioned. in an aqueous organic solvent which contains components of relatively high and low polarity and has a critical solution temperature in the range from 20 to 10,000, the oxidation of the olefin taking place at a temperature above the critical solution temperature of the solvent and the o -Chinon is reduced by the corresponding hydroquinone, b) the temperature of the solvent below the critical solution temperature sen @ t and it thereby separates into its more and less polar phases, c) the less polar, the hydroquinone-containing phase from the more polar phase @@ t, which contains the salt of the metal of group VIII, de cas oxidizes hydroquinone with oxygen or an oxygen-containing gas in the presence of a salt or complex of a heavy metal to the quinone and e) returns the regenerated quinene to the olefin oxidation zone.

The product of the olefin oxidation is preferably obtained from the reaction mixture separated before this is cooled below the critical solution temperature. Otherwise this product is divided into both phases, eo that two separation operations in place of just one. The separation can be carried out by customary methods take place.

After removal of the oxidation product and subsequent cooling of the solvent below the critical solution temperature, the two are formed Phases separated. The polar phase containing the Group VIII metal can be after Addition of regenerated quinone dissolved in the less polar solvent is> to be reused in the oxidation stage.

Preferably contain the tertiary alkyl groups in the above general formula 4 - 8 carbon atoms in the molecule, and the other alkyl radicals 1 - 4 carbon atoms in the molecule.

The most preferred quinone is 3,5-di-tert-butyl-oquinone.

Salts that are particularly useful as catalysts for olefin oxidation are the halides, especially the chirides. Other suitable salts are the salts of inorganic acids, e.g. the sulfates and nitrates, and the salts of organic acids, e.g. B. the acetates.

Palladium is preferred as the metal component of the salts.

The concentration of the Group VIII metal salt is preferably in the range from 0.5 to 50 g / l, preferably in the range from 0.5 to 5 g / l.

The amount of quinone submitted should be greater than that required for the reaction required amount, otherwise free Group VIII metal from the solution is precipitated and is lost to the reaction.

Hydroquinone can be oxidized by reacting it with oxygen or an oxygen-containing gas. Oxidation is useful in one Temperature in the range from 20 to 1200C, preferably in the range from 40 to 90 ° C, and carried out at a pressure in the range of 1 to 100 atmospheres. When oxygenated Gases such as air are used, higher pressures in this range are preferable.

Among the preferred catalysts for the oxidation of hydroquinone include salts or complexes of cobalt, copper, iron or manganese or their mixtures. The catalyst is expediently used in an amount of 0), 1 to 5 parts per 100 parts Hydroquinone used.

The weight ratio of solvent to hydroquinone is appropriate in the range from 1: 1 to 100: 1.

Preferably, the less polar one containing the hydroquinone Phase eu water and added to the polar solvent, the heavy metal catalyst contains, whereby a solvent system is formed, its critical Solution temperature is in the range of 20 to 100 ° C.

A mixture of polar liquids can be used as the polar solvent be used. The compounds already mentioned are suitable as polar liquids, d. H. lower alcohols, ketones, nitriles, amides, sulfoxides and carboxylic acids.

In this case the oxidation of the hydroquinone takes place at one temperature above the critical solution temperature of the aqueous organic solvent performed.

After the oxidation, the reaction mixture is brought to a temperature cooled below its critical solution temperature, whereupon it is in two phases separates, namely a less polar phase in which the oxidation product, the Quinone, and a polar phase that is the oxidation catalyst in solution contains. The less polar phase can be divided into the olefin oxidation zone and the polar one Phase be returned to the zone of hydroquinone oxidation.

Suitable for oxidation by a method according to the invention are olefins that contain terminal or internal double bonds. Suitable are olefins with 2 to 10 carbon atoms in the molecule, preferably those that Contain 2 to 8 carbon atoms in the molecule, e.g. B.

Ethylene, propylene, n-butenes, n-pentenes, 3-methylbutene-j, cyclopentene, n-hexenes, cyclohexene, n-heptene, cycloheptene, n-octenes, cyclooctene and isopentenes, Isohexenes and isoheptenes, as well as octenes, in which the carbon atoms are between which If the double bond is located, there are no carbon atoms on which a branch is made takes place. Alkyl-substituted cyclopentene, cyclobexene, cycloheptene and cyclooctene, in which the same conditions apply with regard to the double bond are also suitable.

The invention is described below in connection with the figure and described by the examples. In the figure is a flow sheet of a process shown according to the invention.

In this process, the olefinic feed is passed through line 1 fed to an olefin oxidation zone 2, where it is treated with a salt of the metal of the group VIII in the presence of a water-containing organic solvent which is an o-quinone of the type described above, at a temperature above the critical Solution temperature of the solvent is brought together. The product from the zone 2 passes through line 3 into a separator 4, in which the oxidation product, d. H. the aldehyde or the ketone, freed from the solvent and passed through line 5 is discharged. The solvent, the noble metal catalyst and the hydroquinone contains, passes through line 6 to a cooler 7 in which the solution is brought to a temperature is cooled below the critical solution temperature.

Here, two phases are formed, which through the line 10 into one Arriving separator ii, in which the two phases in a polar layer 8 and a less polar layer 9 are separated.

The polar layer 8, which contains the Group VIII metal salt in Solution contains is introduced through line 12 into line 25, which contains the solution of the regenerated chlorine from the stage of hydroquinone oxidation, which will be described later is returned. The mixture is in a heater 26 to a temperature above heated to the critical solution temperature of the system. The homogeneous solution obtained, which exits from the heater 26 is the olefin oxidation zone 2 through the line 27 supplied.

The less polar layer 9, which contains the fIyuroquinone in solution, leaves the separator 11 through line 13 and is introduced into line 24 and with the solution of a heavy metal catalyst in an aqueous polar solvent mixed. The one entering the heater 14 Mixture is on a Heated temperature above the critical solution temperature. The obtained homogeneous Solution is then introduced into hydroquinone oxidation zone 16 through line 15. Oxygen or an oxygen-containing gas is introduced into this zone through line 17.

The oxidation product is discharged from zone 16 through line 18 and introduced into a cooler 19, in which it is at a temperature below the critical Solution temperature of the solvent mixture is cooled. This creates two Phases. These phases flow through line 22 into a separator 23, where they into a polar layer 20 and a. less polar layer 21 are separated. the polar layer made up of polar organic solvent, water and the dissolved Heavy metal catalyst is discharged through line 24. The less polar layer containing the regenerated quinone is recycled through line 25 discharged in the Olefinoxidationezone.

Example 1 Ethylene was left for 10 minutes in an amount of 5 1 / hour. by a solution of 5.5 g of 3,5-di-tert-butyl-o-benzoquinone and 445 mg of PdCl2 in 50 ml of N-methylpyrrolidone, 20 ml of water and 30 ml of benzene pearls. The temperature was held at 600C.

Then 0.8 g of acetaldehyde were combined with by vacuum distillation get some water and benzene. which are returned to the solution. The solution was then cooled to 20 ° C, whereupon it separated into two phases, namely an upper one Layer I, the 3.4 g of 3,5-di-tert-butylbrenscatechol, 1.2 g of unreacted 3 * 5-di-tert-butyl-o-benzoquinone and benzene, and a lower layer II. the PdCl2, di-tert-butylpyrocatechol, 3, 5-di-tert-butyl-abovezoquinone and N-methylpyrrolidone contained.

The upper layer I was washed with 10 ml of water to remove residual Remove N-methylpyrrolidone and traces of PdCl2 after removing the water were returned to the olefin oxidation zone by evaporation.

The upper layer I was passed into a vessel containing 100 mg of Co (OOCCH3) 2.4 H202, 40 ml of N-methylpyrrolidone, 7 ml of benzene and 20 ml of water. Through the Solution was oxygen for 1 hour in an amount of 5 liters / hour. at 60 ° C ###### ### ###### headed. The benzene that escaped into a cold trap has been replaced. the Solution was then cooled to 20 ° C., whereupon it separated into two phases, viz an upper layer III, which contained 4.0 g of 3 * 5-di-tert-butyl-abovezoquinone and benzene, and a lower layer IV containing N-methylpyrrolidone and Co (OOCCH3) 2.

The upper layer III was washed with 10 ml of water and then with layer II mixed. By repeating the process of the first olefin oxidation 530 mg of aoetaldehyde were obtained after 10 minutes.

Example 2 By a solution of 11-1 g of 3 * 5-ii-tert-butylpyrocatechol and 200 mg Co (OOC.CH3) 2.4 H20 in a solvent * that consists of 100 ml of N-methylpyrrolidone, 60 ml of benzene and 40 ml of water, oxygen was left in an amount for 1 hour from 10 1 / h pearls. The temperature was kept at 600C. The solution then became cooled to 20 ° C, whereupon it separated into two phases, namely an upper layer I, the 10.0 g of 3,5-di-tert-butyl-o-quinone and mainly benzene as a solution contained * and a lower layer II, the Co (OOC.CH3) 2 and as a solvent mainly Contained N-methylpyrrolidone.

The upper layer I was placed in a vessel containing a solution of Contained 87 mg of PdC12 in 80 ml of N-methylpyrrolidone and 20 111 water. The mixture was heated to 600C and formed a homogeneous solution. Then left one ethylene for 20 minutes in an amount of 10 1 / hour. bead through. By vacuum distillation 1.6 g of acetaldehyde were obtained along with benzene and water, which were added to the reaction mixture were returned. The reaction mixture was then cooled to 20 ° C, whereupon it separated into two phases, namely an upper layer III, the 3,5-di-tert-butylpyrocatechol, some unreacted 3,5-di-tert-butyl-o-quinone and one mainly from benzene existing solvent contained, and a lower layer IV, the PdC12 and a mainly comprised of N-methylpyrrolidone solvent.

Example 3 A solution of 5.5 g of 3,5-di-tert-butyl-o-quinone and 445 mg of PdCl2 in 30 ml of dimethylformamide containing 5% by weight of water was prepared. The solution was left in an ethylene atmosphere under a pressure of 1 hour for one hour Atmosphere stirred at 200C. After this time, the next red solution faded, metallic palladium began to precipitate. At that point the response was ended 1.16 g of acetaldehyde were separated off from the reaction medium by distillation. When analyzed by gas-liquid chromatography, no by-products were found proven.

The addition of water and extraction with benzene gave 5.45 g of 3,5-di-tert-butylpyrocatechol obtained from the solution. The catechnine was then dissolved in 25 ml of dimethylformamide, containing 25 mg of cobalt acetate dissolved and in an oxygen atmosphere for 1 hour heated to 80 ° C under a pressure of 3.5 atmospheres. Crystallized on cooling 4.8 g of -3-5-di-tert-butyl-o-quinone that can be reused for olefin oxidation could.

Example 4 The experiment described in Example 1 was repeated with the difference that p-benzoquinone is used instead of 3,5-itert-butyl-o-quinone 1urde. The same yield of acetaldehyde was obtained.

However, no simple method could be found * to do this at the same time to win hydroquinone formed from the olefin oxidation solution or it in this Reoxidize solution to quinone.

Example 5 A solution of 8 * 5 g CuCl2.2 H20 and 445 mg PdCl2 in 30 ml of water was made. The solution was in an ethylene atmosphere under a A pressure of 1 atmosphere was stirred at 20 ° C. for 1 hour. After this time the reaction was canceled and the Acetaidehyd obtained by distillation. The formed crowd was only Q.06 g.

Example 6 A solution of 9.8 [beta] n-hepten-1, 22 g of 3, 3,5-di-tert-butyl-oquinone and 500 mg PdCl2 in 50 g N-methylpyrrolidone and 10 g water were 15 minutes in heated in a closed vessel. Then 7.65 g of heptanone were obtained by steam distillation won.

The experiments described in Examples 4 and 5 were not carried out according to the method according to the invention and clearly illustrate the superiority of 3,5-di-tert-butyl-o-quinone over p-quinone and copper chloride as redox systems under the reaction conditions used.

The experiment described in Example 6 does not illustrate a complete process according to the invention, however, it shows that higher olefins in the presence of Palla dium chloride and 3,5-di-tert-biityl-o-quinone can be oxidized. The subsequent regeneration of the 3,5-di-tert-butyl-pyrocatechol could be carried out in the manner described in Example 1.

Claims (11)

Claims 1.) Process for the oxidation of an olefin, characterized in that the olefin is mixed with a salt of one of the metals of Group VIII of the Periodic Table with atomic numbers 44 to 78 in the presence of an o-quinone of the general formula in which the groups R1, R2, R3 and R4 are hydrogen atoms or alkyl radicals in at least two of these groups are tertiary alkyl radicals, an organic solvent and water combine to form the hydroquinone corresponding to the quinone used and formed by reduction outside the olefin oxidation zone in the presence of a salt and / or a complex of a heavy metal and an organic solvent is oxidized again to the o-quinone and this is returned to the olefin oxidation zone. 2.) The method according to claim 1, characterized in that the Olefin oxidizes in the temperature range between 200 and 1000C. 3.) Method according to claim 1 or 2, characterized in that the olefin is oxidized in the pressure range between 1 and 100 atmospheres. 4.) Process according to claim l to 3, characterized in that one the hydroquinone by reaction with oxygen . or an oxygen-containing one Gas is oxidized in the temperature range between 200 and 1200C. 5.) Process according to claim 1 to 4, characterized in that one the hydroquinone by reaction with oxygen or an oxygen-containing gas oxidized in the pressure range between 1 and 100 atmospheres. 6.) Process according to claim 1 to 5, characterized in that one the olefin in an aqueous organic solution medium, the constituents with relative contains high and low polarity and a critical solution temperature in the area between 200 and 100 ° C, at temperatures above this critical solution temperature the solution is oxidized by means of reducing the o-quinone to the hydroquinone with lowering the temperature of the solvent below the said critical temperature, which is formed a less polar phase, which contains the hydroquinone, from the more polar, the Separating salts of the metals of group VIII of the Periodic Table containing phase, the hydroquinone with oxygen or an oxygen-containing gas in the presence of a Salt or complex of a heavy metal is reoxidized to o-quinone and this in recycling the olefin oxidation zone. 7.) Process according to claim 1 to 6, characterized in that one a. o-quinone used, the tertiary alkyl groups with 4 to 8 carbon atoms and others Contains alkyl groups with 1 to 4 carbon atoms. 8.) The method according to claim 7, characterized in that as o-quinone 3w5-di-tert-butyl-o-chlnone used. 9.) Process according to claim 1 to 8, characterized in that one a chloride is used as the salt of a metal of Group VIII. 10.) Method according to claim 1 to 9, characterized in that a palladium salt is used. 11.) The method according to claim 1 to 10, characterized in that a salt and / or a complex is used as a catalyst for hydroquinone oxidation used by cobalt, copper, iron or manganese.