DE1201326B - Process for the partial dehalogenation of di- and / or trihaloacetic acid - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Int. α .:

Number:
File number:
Registration date:
Display day:

C07c

German class: 12 ο -12

K51697IVb / 12o
December 21, 1963
September 23, 1965

In the production of monochloroacetic acid, e.g. through direct chlorination of acetic acid, are formed known as by-products, di- and trichloroacetic acid. One can see the formation of these byproducts for example in the continuous industrial production of monochloroacetic acid by keeping about 10 to 15% of the chlorination liquid ("concentric liquid") removed from the circuit. This liquid, in addition to di- and trichloroacetic acid Contains monochloroacetic acid and unreacted acetic acid, can be completely eliminated by chlorination be converted to trichloroacetic acid, from which z. B. prepared the corresponding sodium salt can be. However, since the need for trichloroacetic acid is relatively small, the main amount is of the liquid mentioned is a waste product that must be destroyed.

In the German patent specification 910 778 a way has already been shown to dispose of the worthless chlorination liquid thereby working up beneficially that they are in the vapor state at a temperature passes from 180 to 250 ° C in the presence of hydrogen over a suitable hydrogenation catalyst. The mixture is almost completely converted into acetic acid, which can be used in many ways is. Apart from the fact that the need for acetic acid can be met in other ways can, this process has the disadvantage that the catalyst used after about 14 days Operating time becomes inactive due to heavy gumming. He must then burn off the resinification polymerisation products causing the regeneration. Experience has shown that this regeneration Carry out only once or twice, then the resinification has progressed so far that the catalyst is completely destroyed when burning, so that the comparatively expensive noble metal catalyst only has a short service life.

A more gentle method of converting the chlorination liquid into a technically valuable product in terms of catalyst wear is described in German patent specification 1072 980, which describes the production of monohaloacetic acid by partial dehalogenation of di- and / or trihaloacetic acids, i.e. a mixture that is identical to the above-mentioned chlorination liquid is concerned. The process consists essentially in that di- and / or trihaloacetic acid by passing in the vapor state together with hydrogen over a hydrogenation catalyst in a Tem process for the partial dehalogenation of
Di- and / or trihaloacetic acid

Applicant:

Knapsack Aktiengesellschaft, Huerth-Knapsack

Named as inventor:

Dr. Wolfgang Opitz, Knapsack near Cologne

temperature between 60 and 140 ° C partially dehalogenated. If you work in the range from 100 to 140 ° C, the result is mainly monohaloacetic acid, while in the temperature range from 60 to 100 ° C the formation of dihaloacetic acid is preferred. To at the relatively low Dehalogenation temperatures to ensure sufficient conversion, it is necessary to evaporate the To supply chlorination liquid as quickly as possible to the catalyst, which is done with the help of an inert Carrier gas or with the hydrogen used for hydrogenation is effected. The required for this The amount of gas is about 30 times the amount of hydrogen theoretically required for dehalogenation.

When carrying out this process it has now been shown that the use of an inert Carrier gas or hydrogen in the amount mentioned is technically disadvantageous and in particular uneconomical is because once the substances participating in the dehalogenation reaction are too dilute Stroke state over the catalyst, so that the one-time passage of the gas over the The amount passed through the catalyst is too small and this leads to the separation of the highly diluted Condition occurring reaction products causes great difficulties. Furthermore, it cannot be avoided that parts of the resulting reaction products, especially those with relatively high partial pressure, such as B. acetic acid or especially the hydrogen chloride, deposited imperfectly and thus escape to the outside with the carrier gas. After all, the in high dilution of the hydrogen chloride contained in the carrier gas when the gas is washed out with water only a low concentration acid, which may have to be concentrated.

509 688/471

It has now been found that the disadvantages of the aforementioned methods, in particular the Method of the German patent specification 1072 980, overcome and on the application of large amounts a carrier gas can be dispensed with if the haloacetic acids to be hydrogenated or the Cholating liquid in finely divided droplet form as a mist together with the hydrogen conducts the catalyst.

The process according to the invention for the partial dehalogenation of di- and / or trihaloacetic acid by passing over di- and / or trihaloacetic acid or a corresponding solution of these acids, especially one in the halogenation of acetic acid to monohaloacetic acid resulting as a by-product and called "concentricity liquid" with hydrogen via a hydrogenation catalyst applied to a support elevated temperature, is characterized in that the preheated starting product in the presence atomized by hydrogen to a fine liquid mist, this by a with a Hydrogenation catalyst filled contact furnace passes, in which a temperature of 60 to 140 ° C is maintained is, whereupon the reaction mixture emerging from the contact furnace in a following Separator by cooling in the dehalogenation mixture on the one hand and gaseous components on the other hand, which are drawn off over the top of the separator, separates.

For the atomization of the starting product, which advantageously has previously been applied to that prevailing in the contact furnace Temperature is preheated, it is expedient to use a nozzle through which the Starting product either by means of a hydrogen stream or a mixture of hydrogen and an inert gas, such as. B. nitrogen or carbon dioxide, is atomized into the contact furnace. The liquid mist flowing out of the nozzle is dehalogenated when it is passed over the catalyst, so that from the contact furnace the dehalogenated mixture together with hydrogen halide and excess hydrogen or inert gas escapes. The known ones are used for dehalogenation Hydrogenation catalysts, such as. B. the metals of Group VIII of the Periodic Table, preferably Metals of the platinum group, individually or in a mixture or as an alloy, are suitable, these Metals in the form of their salts, which are deposited on a suitable carrier, e.g. B. silica gel applied are to be used. The dehalogenation process itself can take place under atmospheric pressure or be carried out under reduced pressure, the work being carried out in vacuo, for example colorlessness at a pressure between about 20 mm Hg to below atmospheric pressure of the end product has a beneficial effect.

The reaction mixture emerging from the contact furnace is recovered in the following separator Prior cooling separated into liquid and gaseous components, the latter drawn off overhead and a renewed gradual cooling, for example to a temperature between about +50 and + 3 ° C. The liquid components of the Depending on the reaction temperature, reaction mixtures consist predominantly of mono- or dihalogen- acetic acid, which contains small amounts of acetic acid and hydrogen chloride. From the separator leaving gases or vapors, the hydrogen halide can be removed by washing with water, so that the remaining residual gas for reuse in the contact furnace or for atomization of the Starting product is available.

An example embodiment of the method of the invention is shown schematically in the drawing

ίο shown, in which 1 means a storage vessel, from which the starting product to be hydrogenated via line 2 after prior heating in Heater 3 is fed to the contact furnace 4 by spraying. The atomization of the starting product takes place through a nozzle 5 by means of hydrogen, which flows into the nozzle via line 6. in the Contact furnace is maintained at a temperature of 60 to 140 ° C. The ones in the starting product The contained di- and trihaloacetic acid is when passing through the contact in the presence of hydrogen almost completely dehalogenated to monohaloacetic acid with formation of hydrogen halide. The liquid mist and vapors escaping from the contact furnace pass via line 7 with simultaneous cooling in the cooler 8 in the separator 9, in which the liquid monohaloacetic acid can be collected and removed via line 10. Above the top of the separator the gaseous constituents of the reaction mixture are drawn off through line 11 and for post-condensation in a cooling unit 12, optionally equipped with a brine cooler, in stages post-cooled. The gas, which has been cleaned of liquid components in this way, is passed through the Line 13 introduced into the lower part of the washing tower 14 and in countercurrent with water that the Washing tower 14 is supplied via line 15, washed out. According to the applied Amount of wash water can be a hydrohalic acid at the bottom of the wash tower 14 via line 16 of any concentration. The one purified from hydrogen halide Exhaust gas, which still contains excess hydrogen and possibly inert gas, is removed from the scrubbing tower 14 withdrawn via line 17 and after previous drying together again via line 6 Introduced into the contact furnace 4 with fresh hydrogen.

The method of the invention has the advantage of the good ones over the known working methods Dosability of the starting product as well as the renouncement of the use of large quantities of one Carrier gas, which avoids losses in the end product. Furthermore, the space-time yield increased and by working in the liquid phase overheating and resinification of the catalyst avoided. Finally, there is no need to add special solvents to the starting product, as is customary when working in the gas phase, and the hydrogen halide obtained as a by-product can be converted into a corresponding aqueous acid of any concentration without special measures be transferred.

g example

In the contact furnace, which contained 1000 ml or 390 g of granulated silica gel, onto which 8 g of palladium chloride were applied as a catalyst

250 g of starting material per hour of the composition:

40.4% monochloroacetic acid, 54.8% dichloroacetic acid, 1.0% trichloroacetic acid, 3.6% acetic acid,
0.1% hydrogen chloride,

injected with 751 hydrogen. A temperature of 114 to 118 ° C was maintained in the contact furnace. It was worked at normal pressure. The end product obtained in the separator had the following composition:

89.6% monochloroacetic acid,

4.6% dichloroacetic acid,

5.6% acetic acid,

0.1% hydrogen chloride.

20th

The yield of the above end product and the hydrogen chloride contained in the concentrated hydrochloric acid, based on the starting material used and the hydrogen consumed 98.8%.

Example 2

In the contact furnace, which contained 1000 ml of the catalyst used in Example 1, were each Hour 250 g starting material of the composition:

62.4% dichloroacetic acid, 27.6% monochloroacetic acid, 1.2% trichloroacetic acid, 9.1% acetic acid,
0.1% hydrogen chloride,

injected with 501 hydrogen. A temperature of 116 to 117 ° C and maintain a pressure of 300 mm Hg. The end product obtained in the separator had the following Composition:

84.7% monochloroacetic acid,

5.3% dichloroacetic acid,

9.7% acetic acid,

0.1% hydrogen chloride.

The yield of the above end product and the hydrogen chloride contained in the concentrated hydrochloric acid, based on the starting material used and the hydrogen consumed .99.3%.

Example 3

In the contact furnace, which contained 1000 ml of the catalyst used in Example 1, were 250 g per hour of a chloroacetic acid mixture obtained by chlorinating acetic acid and having the following composition:

25.6% monochloroacetic acid, 34.2% dichloroacetic acid, 34.8% trichloroacetic acid, 5.0% acetic acid,

35 injected with 351 hydrogen. The temperature in the contact furnace was 70 ° C. It was worked at atmospheric pressure. The end product obtained in the separator had the following composition: 28.4% monochloroacetic acid,
61.3% dichloroacetic acid,

4.1% trichloroacetic acid,

5.6% acetic acid.

The yield of the above end product and the hydrogen chloride contained in the concentrated hydrochloric acid, based on the starting material used and the hydrogen consumed 98.1%.

Example 4

There were 300 g per hour of a bromoacetic acid mixture obtained in the bromination of acetic acid the composition:

58.2% monobromoacetic acid,
32.1% dibromoacetic acid,
9.4% acetic acid,

injected by means of 30 1 of hydrogen under a pressure of mm Hg into the contact furnace, the one the example 1 had corresponding catalyst filling. A temperature of Maintain 80 ° C. The end product obtained in the separator had the following composition:

89.0% monobromoacetic acid,
0.5% dibromoacetic acid,
10.1% acetic acid.

The yield of the above end product and hydrogen bromide formed, based on the amount used Material and hydrogen consumed, was 98.3%.

Claims (6)

Patent claims: 1. Process for the partial dehalogenation of di- and / or trihaloacetic acid by passing over di- and / or trihaloacetic acid or a corresponding one Solution of these acids, especially one in the halogenation of acetic acid to monohaloacetic acid as a by-product and called "concentricity liquid" together with hydrogen via one. Hydrogenation catalyst supported on a support is applied, at an elevated temperature, characterized in that the Preheated starting product in the presence of hydrogen to form a fine liquid mist atomized, this passes through a contact furnace filled with a hydrogenation catalyst, in which a temperature of 60 to 140 ° C is maintained, whereupon you get that out of the Contact furnace exiting reaction mixture in a following separator by cooling in the dehalogenation mixture on the one hand and gaseous components on the other hand, which about Head of the separator to be withdrawn, separates. 2. The method according to claim 1, characterized in that the atomization of the starting product through a nozzle using water substance or a mixture of hydrogen and an inert gas, such as nitrogen or carbon dioxide, performs. 3. The method according to claim 1 and 2, characterized in that the starting product under a pressure between about 20 mm to below atmospheric pressure over the catalyst directs. 4. The method according to claim 1 to 3, characterized in that there is used as the hydrogenation catalyst Metals of group VIII of the Periodic Table, preferably metals of the platinum group individually or in a mixture or as an alloy applies, these metals in the form of their salts, e.g. B. on silica gel, be applied as a carrier can. 5. The method according to claim 1 to 4, characterized in that the separator removes the hydrogen halide from leaving gases or vapors by washing with water and the remaining hydrogen-containing residual gas is returned to the contact furnace. 6. The method according to claim 1 to 5, characterized in that the starting product the corresponding chloroacetic or bromoacetic acids are used. 1 sheet of drawings 509 688/471 9.65 © Bundesdruckerei Berlin