DE1768443A1 - Process for the preparation of olefin oxides from olefins - Google Patents

Description

New complete for the printing of the published patent application Registration documents - P 17 68 443.4

FARBENFABRIKENBAYERAG

L E V E R K U S E N - Bayerwerk Pitcnt department

Dz / CK November 21, 1969

Process for the production of olefin oxides? * Is Qlefinen

The invention relates to an electrochemical process for the production of olefin oxides from olefins.

It is known to produce olefin oxides from olefins by an electrochemical process in which chlorine is formed by electrolysis of an aqueous electrolyte containing a metal chloride and chlorine is formed in a system consisting of an anode, a Ksthode and a diaphragm located therebetween Chlorohydrin is unset, after which the chlorohydrin with the hydroxyl ions generated in the electrochemical system undergoes a dehydrochlorination sum olefin oxide and then the olefin oxide formed is separated from the electrolyte and the electrolyte is returned to the electrochemical system.

E3 has now been found that in the process for the preparation I of olefin oxides from olefins, in which in an electrochemical system consisting of an anode, a cathode and a diaphragm located between them, chlorine is formed by electrolysis of an aqueous electrolyte containing a metal chloride and with the water and the olefin to its chlorohydrin. is unset, after which the chlorohydrin with the hydroxyl ions generated in the electrochemical system ^{undergoes a dehydrochlorination 1} to the olefin oxide, whereupon the olefin oxide is separated from the electrolyte and the electrolyte is returned to the electrochemical system, in a particularly advantageous manner

Le A 11 456 _K.
; New UnLei luyun (Art. 7 fi-1. · .. ■ .. 2 1 <r. 1 i ^ _u j of the amendment ··. V.

109851/187 5

Can produce olefin oxides from olefins, when the electrolyte freed from the olefin oxide is treated with elemental chlorine ".

It is advantageous to take the treatment of the electrolyte with chlorine, for example, as in the electrochemical system Temperature before. The chlorine is expediently introduced into the electrolyte in gaseous form. In one embodiment of the In the process, for example, it is fed into a tower-like container through which the electrolyte flows upwards will. The chlorine is finely divided, for example, through nozzles, third parties or similar devices .in the lower part of the tower-like container. One can

ψ also treat the electrolyte with the chlorine in the tower-like container in countercurrent, ie introduce the electrolyte into the top of the tower and remove it from below. In general, it is not necessary to ensure mechanical agitation in the electrolyte, but it is possible, if necessary, to use agitator vessels with smaller volumes. In another embodiment of the method, the treatment of the electrolyte with chlorine is effected in that the electrolyte freed from propylenoiid is passed in a suitable manner through the anode compartment and optionally also the cathode compartment of an auxiliary electrolytic cell connected to the electrolyte circuit The chlorine developed in the anode of the auxiliary electrolysis is then also effective in the manner outlined. Care must be taken that the chlorine brought into contact with the electrolyte is completely absorbed by the electrolyte, primarily in the form of its hydrolysis products.

It has proven to be an expedient embodiment to carry out the treatment with elemental chlorine in the alkaline electrolyte immediately after the olefin oxide has been distilled off therefrom, where the electrolyte with a pH of 10 to 13 is available. However, it is also possible to carry out the chlorine treatment at lower electrolyte pH values, for example by first setting the pH Le A 11 456 - 2 - by adding hydrochloric acid.

109851/1873 BAD original

has lowered accordingly. ·

Ea is convenient to the electrolyte between treatments with chlorine and the introduction of the electrolyte into the electrochemical system, a residence time of 1 "to 30, It is advantageous to provide 5 to 15 minutes in advance.

The electrolyte introduced into the chlorine amount is Bweckuiäßigerweise about 0.5 to 10, advantageously 1 ^tis 5 t of the electrochemically active current.

The electrolyte treated with chlorine is returned to the anolyte of the electrochemical system.

When using this method, particularly constant results are also obtained with closed recirculation of the electrolyte over long operating times. In addition, there is no Pollution of the circulating electrolyte by undesired organic intermediates.

The method according to the invention is suitable for the most varied of embodiments suitable for the electrochemical production of olefin oxides from olefins. The following forms are exemplary here called the execution:

In the electrochemical system consisting of anode, diaphragm and cathode, the olefin to be converted is introduced in gaseous form into the anode compartment at the bottom, and the olefin is converted to olefin chlorohydrin as the olefin passes through the anode compartment. The electrolyte is passed through the anode compartment, passes through the diaphragm into the cathode compartment and returns to the anode compartment after it has been freed from the olefin oxide formed in the cathode compartment from the chlorohydrin by distillation . ■

I «A 11 456 . - 1 -

109SS W187 3

In another embodiment, you can remove your electrochemicals System part of the anolyte and uses the chlorine contained in it, generated by the electrolysis, or its hydrolysis products in a reaction room outside of the electrochemical system with the olefin to give the corresponding Chlorohydrin. Here, too, the electrolyte cycle described takes place, and the electrolyte freed from the olefin oxide formed returns to the electrochemical system in the manner described.

In a further embodiment, the with the chloshydrin loaded anolyte outside the electrochemical system reacted with .dem the catholyte containing the hydroxyl ions, wherein this reaction can advantageously be combined with distilling off the olefin oxide formed. The one from the olefin oxide Freed electrolyte can then be returned to the electrochemical system, advantageously evenly divided on anode and cathode compartment. In this case too, partial passage of the anolyte through the diaphragm into the Cathode compartment take place.

You can z. B. working in the electrochemical system with current densities of 2 to 50 ampere / dm anode surface, with voltages of 3-to 6 volts and with temperatures of 30 to 90 ⁰ C. It is advantageous to work at normal pressure, but it is also possible to work at elevated pressure, for example 1.2 to 5 Ata., And if necessary also at a slight negative pressure.

Particularly suitable starting materials for the production of the olefin oxides are gaseous monoolefins, such as ethylene, propylene and butylene, but also halogenated monoolefins, such as allyl chloride. The olefins can also contain inert constituents, such as, for example, ethane, propane or butane. The throughput pn olefin through the anode compartment can be selected, for example, so that about 5 to 95 v> are converted in a single pass. Eich has proven to be a particularly advantageous way of working to insert a gas-

Lt A 11 456 - 4 -

10885W1873

CRIÖINAi. IMSPECTEED

Shaped Gem! sell to be brought in from the to be implemented. Olefin and an inert grass, the concentration of the olefin in the gas mixture being 8 »B. 25 "to 65 Vol .- ^, advantageously 55" to 55 Vol .- #, and with a single passage of the gas mixture through the anode compartment 75 to 95, * ,. advantageously 80 to 90 #, of the introduced olefin umsras et time. Suitable inert gases are, for example, the gaseous paraffins corresponding to the olefin used.

The electrolyte can be, for. B. aqueous solutions of sodium or Use potassium chloride or mixtures thereof. The concentration of the salts in the electrolyte can be, z. B. 2 to 20 wt .- #, advantageous 3 to 15% by weight.

For example, the electrolyte with a throughput of 20

■ ζ ρ

up to 200 cm / minute and 1 dm anode area in circulation will. "

All anodes in the electrochemical system can be electrodes made of graphite, platinum, with noble metals such as platinum, but also with mixtures of platinum with other noble metals - in particular iriium and rhodium, coated litan, made of platinum-coated tantalum, magnetite or inert carriers coated with platinum, such as Polyethylene or polyfluorocarbons can be used. Anodes made from titanium and a cover layer made from oxides of one or more noble metals from the group of platinum, palladium, iridium, ruthenium and bhodiuin are particularly advantageous. Advantage-. way enough, the titanium core to the St@3.1en _s aa is the top layer is porous, which see a Sperrhaut- from ■ titanium oxide comparable J. The application of the Sdelraetalloxide- on the Titanicern can take place in such a way that they are wholly or partly in the mixed crystal with the titanium oxide.

The cathode in the e-lectroehealsehtn system described is advantageously used as wire meshes made of elsenic or stainless steel, the cathode advantageously having approximately the same surface as the anode. As a diaphragm for the present process are inert materials see, for example, may live wi®, PoIyfluorkohlenwasseratoffe _s polyolefins such. B, polyethylene, polypropylene, polybatylene, polystyrenes, polyaorylaitrile, polyvinyl compounds, like "1", Bolyrli ^ lelilorii © eier Miachpolymeri -

'108 * 51 /

im a H 456 ■

i-i-; c:; - i> BAD original

* 17F8443

aate of vinyl chloride and vinylidene chloride and others more. The' Materials can be used in the form of permeable or porous sheets or films or, as fibers, in the form of fabrics or fleece. You can also determine the pore size of suitable diaphragms - for example of fabrics made of polyacrylonitrile - still by a Reduce heat and / or pressure treatment, e.g. by calendering.

Example ι

a) An electrolytic cell with an anode of

2
1.75 dm of titanium sheet, which was provided with a circulation of ruthenium oxide ⁽¹ O g / m "). The anode was a wire mesh cathode made of stainless steel of the same surface at a distance of 6 mm from. As a diaphragm which rested the cathode was a Polypropylene fabric 0.4 mm thick was used. The electrolysis cell was filled with an 8.5% strength aqueous potassium chloride solution and a direct current flowed through the electrodes when a direct voltage of 5.0 volts was applied

an anodic current density of 34 3 Amp / dm. The temperature of the electrolyte in the cell was 59 ° C. The cell operated without pressure, every hour 63 liters of a C 1 fraction with a content of 94% by weight propylene, the remainder being essentially propane, were introduced into the anode compartment through a passage arranged below the anode. About 42 # of the propylene were converted, essentially with the formation of propylene chlorohydrin. The excess, unconverted gas left the anode compartment after the anolyte had been separated off. Every hour, 6 liters of the electrolyte were passed from the anode compartment through the diaphragm into the cathode compartment. In the cathode compartment, the propylene chlorohydrin contained in the electrolyte was dehydrochlorinated to form propylene oxide. From the cathode room '. an amount of catholyte corresponding to the amount of anolyte added was withdrawn, and the propylene oxide contained therein was dee.tillatively driven off. The remaining electrolyte then passed at a temperature of about 55 ⁰ C ir. Upflow a ■ burmartigen container of 400 cm content in which every hour 2.5 g of elemental chlorine are gaseous and fine particles introduced below, then the circle returned running electrolyte after leg pH -Value has been adjusted to 8 to 9 by adding hydrochloric acid.

ie A 114! ? t _{Λ 1AllI} .,

- «-———— BAD ORIGINM.

The over a period of, 4 hours, during the electrolysis The gaseous and liquid products finally leaving the cell were analytically recorded and used to calculate the current yields used. '

The test results are shown in the table below:

Reaction product yield in stream #

Propylene oxide 86.4

1 "2-Diciilorpropon 12.1"

Propanediol-1,2 1,5

Propylene chlorohydrin 0.5 other organic products 0.8

Oxygen 0.9

Carbon dioxide __ 0.7

102.9

b) If the procedure described in Example 1a) is carried out in the same, Well done, but without treatment of the electrolyte with chlorine after the propylene oxide has been removed, so comes it becomes harmful after only 1 yfoche of operation Contamination of the running electrolyte. I enrich it strongly colored organic compounds in the electrolyte, which give rise to an increase in the cell voltage and with continuation of operations to deposits, for example lead to the electrodes, with which the operation to er- · | come to lie.

Example 2

a) An electrolytic cell was used in which the plate-shaped anode and the cathode designed as a wire mesh faced each other in parallel. Both electrodes had a width of 100 mm and a height of 750 mn. The anode consisted of a titanium sheet coated with platinum, which

Ie A 11 456 - 7 - ■ '

108851/1873

1168443

Stainless steel cathode. The asbestos paper diaphragm between the two electrodes lay tightly against the cathode wire mesh. The distance between the anode and the diaphragm surface facing the anode was 6 mm. The cell was filled with a 8.5 followed by aqueous Kaliurachloridlösung. By applying an electrical direct voltage of 4.4 volts between the anode and the cathode, a direct current flowed with a current density of 12.3 amperes / dm anode surface. The temperature of the electrolyte was 59 ° C. The cell worked without pressure. Every hour, 95 liters of a fraction of Cp hydrocarbons with a content of 92% by weight of ethylene, the remainder being essentially ethane, were introduced finely divided into the anode compartment through a prite attached below the anode. About 45 # of the ethylene were converted. The excess, unconverted gas left the anode compartment of the cell after being separated from the anolyte. Every hour, 9.5 liters of the electrolyte were passed from the anode compartment through the diaphragm into the cathode compartment. In the cathode compartment, the ethylene chlorohydrin contained in the electrolyte was dehydrochlorinated to give ethylene oxide. An amount of catholyte corresponding to the access of anolyte was withdrawn from the cathode compartment and the ethylene oxide contained therein was separated off by distillation. The freed from ethylene oxide electrolyte then passed at a temperature of about 55 ⁰ C the anode compartment of an additional electrolytic cell is connected to the electrolyte circuit. This auxiliary electrolysis cell operated with a current load of 1.3 amperes, so that about 1.7 g of elemental chlorine per hour, finely divided, were introduced into the return electrolyte. The circulatory electrolyte then returned to the anode compartment of the cell after its pH had been adjusted to 9-10 by adding hydrochloric acid. The reaction products contained in the anode or cathode exhaust gas and in the catholyte were recorded analytically and used to calculate the current yields.

Le A 11 456 - θ -

109851/1873

BATH

Reaction product __ yield in stream j>

Ethylene oxide 82.9 "

1,2-dichloroethane 11.3

Ethylene glycol 1> 1

Ethylene chlorohydrin 4.2

other organic products. 0.9

Oxygen 0.5

carbon dioxide; 0.3

101.2

b) If the procedure described in Example 2 a) is the same

Sometimes carried out, but without that of ethylene oxide Free electrolyte from being returned to the electrolytic cell is treated with chlorine, the circulatory electrolyte becomes contaminated after just a few days. It Strongly colored organic compounds accumulate in the electrolyte, causing the cell voltage to increase and lead to deposits, for example on the electrodes, when the operation is ported, which brings operation to a standstill comes.

Example 3

a) The apparatus consisted essentially of an electrolysis {j cell and a Resktionsraum for the olefin conversion.

In the electrolysis cell there was an anode made of a massive, on the side facing the cathode covered with a noble metal oxide layer consisting of ruthenium oxide and a cathode made of a stainless steel wire mesh, each with an area of 1.75 dm, perpendicular to each other at a distance of 4 arranged opposite Kim. Between the electrodes there was a diaphragm made of a 0.14 mm thick polyethylene

Lo A 11 456 - 9 -

. "^{; A} " 109851/1873

Tissue that lay on the cathode and divided the cell interior into an anode and a cathode compartment. The reaction space for the. Olefin conversion consisted of a vertically arranged tube with a diameter of 26 mm, at the bottom of which a glass frit was arranged. This reaction space was connected to the anode space of the electrolysis cell by 2 horizontally running pipes, each ending above and below the anode. A gas separator was installed between the reaction chamber and the pipe connection to the anode chamber at the top, through which the gases contained in the electrolyte were almost completely removed. The electrolysis cell and reaction space were filled with an 8.5 # aqueous potassium chloride solution. When a direct voltage of 4.9 volts was applied to the electrodes, a direct current with an anodic current density of 32.8 amperes / dm flowed. The temperature of the electrolyte in the cell and reaction chamber was 59 ° C. The cell and reaction chamber operated without pressure. Every hour 61 liters of a fraction of C, hydrocarbons with a content of 94% by weight propylene, the remainder being essentially propane, were introduced through the glass frit into the electrolyte in the reaction space in such a way that the gas, filling this space, rose in finely divided form . Of the propylene, $ 43 were converted. The excess gas left the reaction space via the gas space arranged above the electrolyte level. The pipe connections between the gas-filled electrolyte in the reaction space and in the gas-free electrolyte in the anode space of the electrolytic cell resulted in an intensive electrolyte cycle in such a way that the gas-rich electrolyte rose in the reaction space, while the practically gas-free electrolyte in the anode space between the anode and the diaphragm flowed downwards. Every hour, 6 liters of the 8.5 aqueous potassium chloride solution were passed from the anode compartment through the diaphragm into the cathode compartment. The dehydrohalogenation of the propylene chlorohydrin contained in the anolyte to propylene oxide took place in the cathode compartment. An amount of catholyte corresponding to the access of anolyte was withdrawn from the cathode compartment and the propylene oxide contained therein was driven off by distillation. The electrolyte freed from propylene oxide then passed through a turin-like container of Ie A 11 456 - 10 - at a temperature of about 55 ° O in the downward flow.

109851/1873

BATH ORIGINAL

17 ^ 8443

400 cm x ⁵ content, into which 2 g of elemental chlorine per hour were introduced in gaseous and finely divided form. The circulatory electrolyte then returned to the anaenous space of the cell after its pH had been adjusted to 9-10 by the addition of hydrochloric acid.

The over a period of 4 hours during the electrolysis The gaseous and liquid products finally leaving the cell were recorded analytically and used to calculate the 'Electricity yields used. The results of the experiment are shown below. Table listed.

Reaction product yield in electricity JL

Propylene oxide 85.9

1,2-dichloropropane "12.3

Propanediol-1,2 1,4

Propylene chlorohydrin 0 _f 6

other organic products 0.8

Oxygen 0.8

Carbon dioxide 0.6

102.4

b) If the procedure described in Example 3 a) is the same Wise carried out, but without the freed of propylene oxide electrolyte before the Bückführung in the electrochemical J If the system is treated with chlorine, the circulatory electrolyte will be contaminated after a few days. Eioh strongly colored organic compounds accumulate in the electrolyte, which cause an increase in the cell voltage and in porting the operation to deposits, for example lead to the electrodes, with which the operation comes to a standstill.

Le A 11 456 -11-

109851/1873

Example 4

a) The experimental arrangement described in Example 3 was used for Example 4 added as follows:

The electrolysis cell and reaction space for the olefin conversion were retained, but a diaphragm made of asbestos paper with a thickness of 1.2 mm was used as the diaphragm of the electrolysis cell. The apparatus was supplemented by a dehydrochlorination column, filled with 4 mm glass Raschig rings, 120 cm high and 25 mm in diameter, which was equipped with a receiver cooled with brine and the bottom of which was indirectly heated. The electrolysis cell and reaction room were equipped with a 5 joigen. aqueous potassium chloride solution. Every hour 2 liters of this solution from the upper connecting line between the reaction chamber and the anode chamber or from the cathode chamber of the cell were passed gas-free into the middle of the column via pump lines and, after the volatile products had been separated from the column bottom, which was kept at the boiling point, a chlorine treatment and a pH -, a density and a temperature control are returned in equal parts to the cathode and anode area of the cell. To chlorine treatment freed of propylene oxide electrolyte happened to a temperature of about 55 ⁰ C in an upflow tower type container of 250 cm contents, was in which at the lower end 0.5 grams of elemental chlorine introduced h gaseous and dispersed /.

The pH control added hydrochloric acid to the electrolyte in such a way that the return electrolyte had a pH value had from 8-9. The density regulation was controlled by metering from water to the return electrolyte the potassium chloride content. The temperature control set the temperature of the return electrolyte in such a way that the electrolyte temperature in the electrolysis cell and reaction chamber was 59 ° C. cell and reaction chamber operated at atm. Pressure that dehydrohalo-

Le A 11 456 - 12 -

109851/1873

genierkolonne at 100 mm Hg Hourly 45 liters of a fraction of (were -.! hydrocarbons having 94 Gew.Jf propylene (Best introduced substantially propane) through the glass frit into the electrolyte in the reaction chamber such that the gas, this space fulfilling finely The excess unreacted gas left the reaction space via the gas space above the electrolyte level. The pipe connections between the gas-filled electrolyte in the reaction space and the gas-free electrolyte in the anode space of the electrolysis cell resulted in an intensive electrolyte cycle in such a way that the gas-rich Electrolyte rose in the reaction chamber, while the gas-free electrolyte flowed downward in the anode chamber. A direct voltage of 3.45 volts was applied to the electrodes of the electrolytic cell, so that a direct current with a current density of 11 _r 2 amperes / i dm anode area over a period of 4 Hours flowed in. The reaction space and the cathode space The liquid reaction products leaving the electrolytic cell in gaseous form and the liquid reaction products obtained in the receiver of the dehydrochlorination column or remaining in the electrolyte were analyzed. The test results are shown in the table below;

Reaction product

Yield in electricity j>

Propylene oxide 1,2-dichloropropane Propanediol-1,2 propylene chlorohydrin other organic products oxygen carbon dioxide

89.6 8.1

1.4 0.4 1.5 0.3 0.5 101.8

Le A 11 456

- 13 109851/1873

Claims (3)

Λ 17684 «Patent claims * 1) Process for the production of olefin oxides from olefins, "at which in an electrochemical system consisting of an anode, a cathode and one in between Diaphragm formed by the electrolysis of an aqueous electrolyte containing a metal chloride and chlorine Water and the olefin is converted to its chlorohydrin, after which the chlorohydrin with the in the electrochemical system Hydroxyl ions generated undergoes dehydrochlorination to the olefin oxide, whereupon the olefin oxide from the electrolyte separated and the electrolyte is returned to the electrochemical system, characterized in that the * treated electrolytes freed from olefin oxide with elemental chlorine. 2) Method according to claim 1), characterized in that the treatment of the electrolyte with chlorine approximately in the electrochemical System prevailing temperature is made. 3) Method according to claim 1) and 2), characterized in that that the electrolyte after treatment with chlorine only takes 1 to 30 minutes, advantageously 5 to 15 minutes, is introduced into the electrochemical system. A) Process according to claim 1 to 3, characterized in that the amount of chlorine to be introduced into the electrolyte is 0.5 to 10, advantageously 1 to 5 ° C., of the electrochemically active current. Le A 11 456 - 15 - 109551/1873 b) If the method described in Example 4 a) is the same Wise carried out, but without the freed from propylene oxide If the electrolyte is treated with chlorine before it is returned to the electrochemical system, it already follows a few days to contamination of the circulatory electrolytes. Strongly colored organic compounds accumulate in the electrolyte, which increases the cell voltage and lead to deposits, for example on the electrodes, when operating the operation comes to a standstill. Le A 11 456 - U - 109851/1873