DE1232129B - Process for the continuous production of monochloroacetic acid - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Int. Cl .:

C07c

German class: 12 ο-12

Number: 1232129

File number: U 7630IV b / 12 ο

Filing date: December 6, 1960

Opened on: January 12, 1967

The invention relates to a continuous process for the production of monochloroacetic acid by chlorination of a mixture of acetic acid and acetic anhydride or acetyl chloride at a temperature of 90 to 140 ⁰ C under pressure, which is characterized in that liquid or gaseous chlorine is continuously added to the mixture to be chlorinated 90 to 140 ° C, preferably at 110 to 130 ⁰ C, under a pressure of 2 to 6 atmospheres, preferably 3 to 5 atmospheres, in such a proportion that the liquid mixture continuously withdrawn from the reaction vessel at least 5%) preferably 8 to 20, advantageously not more than 15 percent by weight of acetic acid and its content of acid chlorides and acid anhydrides in the hydrolysis corresponds to a water consumption of 1.5 to 3.5, preferably 2 to 3 percent by weight, while the vapor mixture leaving the reaction vessel is washed with fresh acetic acid, which is then fed back into the reaction mixture .

The process according to the invention ensures a very high reaction rate. This is special essential, since the chlorination mixture of acetic acid is highly corrosive. A high rate of chlorination namely has the advantage that a comparatively small device can be used. Another object of the invention The process is to achieve a high yield with very low losses of acetic acid and chlorine. In addition, the end product should contain a comparatively low dichloroacetic acid content.

The production of monochloroacetic acid by chlorination of a mixture of acetic acid and acetic anhydride or acetyl chloride at a temperature of 90 to 140 ° C under pressure is known per se, but the earlier processes did not aim to achieve the highest possible reaction rate in relation to the size of this The equipment used is respected and, instead, the aim is to achieve the highest possible purity of the end product. So you get z. B. in the chlorination of acetic acid with chlorine and phosgene at a temperature of 100 to 120 ° C a yield of monochloroacetic acid of over 95% in a purity of 99%> ^a over the reaction rate is the formation of about 50 g of monochloroacetic acid per hour and per liter of reaction mixture.

In contrast, the process according to the invention is based on the finding that with a suitable combination of the chlorination conditions using chlorine as the only chlorinating agent, that is to say without using the toxic phosgene, with a process for continuous production
of monochloroacetic acid

Applicant:

Uddeholme Aktiebolag, Skoghall (Sweden)

Representative:

Dr. H. H. Willrath, patent attorney,

Wiesbaden, Hildastr. 18th

Named as inventor:

Sven Helmer Persson,

Per Torsten Akerström,

Per Erik Larberg,

Sven Erik Leonard Nord, Skoghall (Sweden)

Claimed priority:

Sweden of 7 December 1959 (11521),

dated December 12, 1959 (11522),

dated January 22, 1960

Minimum amount of 100 g of chlorine per hour and liter of reaction mixture can be worked and it actually does it is possible to reduce the amount of chlorine fed in to more than 1000 g per hour and liter of reaction mixture to increase. A ratio of 300 to 1000 g of chlorine per hour and liter of reaction mixture is preferably fed in. On the other hand, avoid that Process according to the invention also overcome the difficulties in the chlorination of acetic acid in the presence of Anhydride or acetyl chloride resulting from the hydrogen chloride gas escaping from the reaction vessel still a considerable number of valuable compounds, primarily acid chlorides, contains. The process of the invention also enables these compounds to be recovered.

It is already known that acetic acid can easily be mixed with acetic anhydride or acetyl chloride can be chlorinated. So it is for example from the British patent specification 621531 (corresponding to the U.S. Patent 2,503,334) known to add a mixture of acetic acid and a small amount of anhydride

609 757/425

chlorine, but this small amount is not enough for an unexpectedly quick and effective chIo-

in order to achieve the above-mentioned goals, because this is the ration. That is why the chlorine content in the

at least 15% anhydride (or the equivalent escaping vapors low, even if

Percentage acetyl chloride) is introduced into the chlorine to be chlorinated at high speed.
Mixture are required. 5 One might have expected that the increased pressure

The German patent specification 638 117 describes one under which the method of the invention is carried out

Process for the chlorination of a mixture of vinegar, to an increased formation of dichloroacetic

acid with up to 30 percent by weight acetic anhydric acid, but surprisingly it is

drid low at elevated temperature and a low content of dichloroacetic acid in the end product.

Overpressure, but the meaning of the io was not

Maintaining a certain percentage of the method according to the invention is carried out as above

unchlorinated acetic acid in the mixture during the mentioned, chlorine in an amount of at least 100,

entire course of the reaction and a pressure preferably 300 to 1000 g per hour and liter of reac-

recognized by at least 2 or 3 atmospheres. mishap too. It is also useful that

Other methods that use acetic anhydride than 15 run the reaction so that 15 to 30, preferably

use a single reaction promoter, 20 to 30 parts by weight of acetic anhydride or acetic acid

British patents 682 282 and 793 912 tyl chloride to 85 to 70, preferably 80 to 70,

(according to US Pat. No. 2,539,238 parts by weight of acetic acid are added,

and 2,826,610). With these batch-wise the vapors escaping from the reaction vessel Process should contain such a pure monochloroacetic acid, as already mentioned above, hydrogen chloride,

can be obtained that this directly without further cleaning acetic acid and other volatile compounds, such as

can be processed further. However, here z. B. acetyl chloride and chloroacetyl chloride. To

Firstly, a high degree of chlorination and, secondly, to avoid loss of these compounds

low formation of dichloroacetic acid aimed at. the vapors with acetic acid, which are then

These targets are either re-fed by application of a 25 tion vessel, washed,

high percentage anhydride (which, however, is from Swedish patent specification 138 864

is equally expensive and although known to be a volatile loss, such losses by cooling the

Reactants or products leads) or by chlorination exhaust gases and to reduce the acetic acid

Achieved using a long chlorination time. to be used as a washing liquid. The washed

However, the monochloroacetic acid gas produced by this process still contains a considerable amount of

However, acid is not sufficiently pure for many purposes, chlorination products. It is also known that

but must ζ. B. by recrystallization to wash purified chlorination waste gas in two stages, and

will. first with acetic acid and then with

In contrast to these known chlorination acetic anhydride. But also this two-step process If the method of operation according to the invention offers a method leads to a loss of valuable products Advantage of a quick process, which is due to the fact that the chlorine soft only a small percentage of hydrogen acetic acid in the exhaust gas with the acetic anhydride under it requires anhydride and leads to an end product, formation of acetyl chloride reacts, which a which only has a low content of dichloroacetic acid and therefore has a higher vapor pressure contains. 40 escapes with the washed gases.

In the process according to the invention from the washing of the reaction vessel, the acid chlorides and the chlorination off-gas with the acetic acid, preferably hydrides, are then expediently hydrolyzed by adding in such a way that the water in the reaction vessel is hydrolyzed to the corresponding acids. Leaving vapors with acetic acid in three stages, before-It has been found that when the content of acid-45, preferably treated in a column in countercurrent, chloride and anhydride is less than 1.5%, the formation of the vapors in the first Cooled stage, in which dichloroacetic acid rises and the reaction - second stage through washing of the organic speed decreases. If, on the other hand, more components are freed and acetic anhydride is added in the third stage than a requirement for saturation of acetic acid with hydrogen chloride of 3.5% water for hydrolysis, then 50 takes place, while the acetic acid saturation does not increase, among other things Partial pressure of the acetyl required hydrogen chloride between scrubbing and saturating chloride in the escaping gas is removed from the system in one step,
The saturation of acetic acid with hydrogen chloride leads to the saturation of the acetic acid with hydrogen chloride, even if the escaping gas can be washed in the upper part of the washing column or in an acetic acid. 55 saturators arranged separately from the column

It was also found that the presence of follow. A suitable device is a so-called 5 to 20 percent by weight, preferably 8 to 15 Ge liquid film cooler. For saturation, weight percentage is used, non-chlorinated acetic acid react preferably only such an amount of hydrogen chloride tionsgemiseh an extensive formation of dichloro used, as for the production of a practically with acetic acid prevents, even if acetic acid is required among such 60 saturated hydrochloric acid Conditions are operated under which otherwise one is, so that the gas leaving the column is substantially increased Formation of dichloroacetic acid in the final product is borrowed free of hydrogen chloride. However, it is too would take place. More than 20 percent by weight of vinegar - possible, the process with an acetic acid through-acid however, cause an undesirable increase in feed, which is not complete with chlorinated water Reaction volume. 65 is saturated, but then there is an increased loss

The applied pressure of 2 to 6 atmospheres causes acetic acid to be expected.

a low content of acetic acid in the from the The process according to the invention is intended in the following

Reaction chamber escaping vapors and are explained in more detail with reference to the drawing.

5 6

This is not possible with a stirrer, not shown, boiling points. Therefore, the further

See reaction vessel 1, for example, has a fast work-up in a known manner by crystallization

Solving power of Im ³ reaction mixture. Through sation.

line 13 becomes acetic anhydride or acetyl chloride. The process according to the invention is described below

and fed through line 15 chlorine. The vinegar 5 further explained through several exemplary embodiments, acid can be added to the vessel 1 to be explained later

Way in whole or in part by way of example 1
Column 3 are fed. A device according to the drawing, however, consisted of a part of the acetic acid also fed through the tube 13 to a reaction vessel with a capacity. The line 14 is used for the continuous flow of 9001 and a washing column with a thorough discharge of the reaction mixture into the knife of 250 mm and a height of 3 m. Vessel 1 reaction vessel was continuously formed with 38 kg of acetic acid so that the reaction introduced acid anhydride per hour at one pressure. Chlorine was carried up to 6 atmospheres. continuously at a speed of 180 kg

The liquid from the phase in the reaction vessel 15 corresponds i _n hour fed. The reaction mixture was

softening vapors are passed through the line 2 to a temperature of 120 ⁰ C under a pressure

Bottom of the absorption column 3 led, which kept about 3 atmospheres. A quantity of 135 kg of acetic acid

a height of 3 m and a diameter of 0.2 was placed on top of the washing column every hour.

up to 0.3 m. It is used for absorption and given by the cooler 6 to a temperature

usable chlorination products by acetic acid, which is cooled to 20 by 20 ° C.

is fed through line 4, and to saturate it. The reaction mixture obtained consisted of about hydrogen chloride. In the upper part of the column there is 75% monochloroacetic acid, 10% acetyl chloride and there is a cooler6, eg a liquid film - chloroacetyl chloride and 15% acetic acid and became cooler. Gas that is precipitated in this way also escapes continuously in this way from the reaction vessel through the line 5. Below the cooler is 25 that in this a constant liquid is a gas outlet 7 for the hydrogen chloride, which has not been maintained in quantity. The reaction resulted in the saturation of acetic acid being used. The further a vapor phase, the hydrogen chloride (90 kg / lower part of the column 3 is divided into two sections 8a hours), organic components such as acetic acid, acetyl and 8b and contains either a pack of chloride and chloroacetyl chloride in an unknown amount Packings or bottom plates of known type. In 30 and unreacted chlorine in a small amount the section 8b are contained from the reaction. This vapor phase was cooled down in the column in vessel 1 through line 2 incoming vapors countercurrent to the downward flowing acetic acid. For this purpose, the line 10 is passed downwards.

by means of the pump 11 washing liquid from the bottom of the A quantity of 1000 kg washing liquid per hour was drawn off through the cooler 12 and in 35 was pumped through the cooler 12, the upper part of the section 8b being controlled again in the cooling column so that the Steam fed into the The ascending from the reactor column after passage through the zone 8b vapors are therefore had by washing the cooled temperature of 25 ⁰ C. During the subsequent liquid, which mainly consists of passage through zone 8 a, which contains hydrogen chloride, where the more saturated acetic acid consists, it is cooled. From here, the same washing took place, the temperature of the cooled vapors entering section 8a of the vapor was further reduced to 20 ° C and this was also a column where the usable chlorination products dissolved the temperature of that withdrawn through outlet 7 in acetic acid will. Hydrogen chloride. The latter still contained acetic acid,

The vapors coming out of the reaction vessel according to the saturation pressure at a temperature

are therefore in countercurrent to the temperature of 20 ° C through line 4 45, in small amounts and extremely low

pure acetic acid fed to the column. Amounts of other organic compounds and chlorine.

After they in section 8 a of their usable part of the hydrogen chloride was by the

Constituents are freed, the outlet 7 continues to rise is not withdrawn, but it was left open-

Lowing gas consisting essentially of hydrogen chloride and flowing into the cooler 6 downwards. This crowd was

of this, such a proportion is chosen as it is for saturation 50 so that there is a saturated HCl solution in the

the acetic acid is required, formed in countercurrent to the acetic acid applied at the top of the column,

the latter passed through the cooler 6, while only an insignificant amount escaped as a result

excess gas is withdrawn through line 7. Hydrogen chloride through outlet 5, and from

The resulting saturated solution of hydrogen chloride cooler 6 to zone 8 a had acetic acid flowing

in acetic acid flows through sections 8a and 8b 55 temperature of 20 ° C and was with hydrogen chloride

downwards, the saturated from the reaction vapors decreases.

washed chlorination products and flows In the following examples, a reaction

back through line 9 into reaction vessel 1. The vessel with a capacity of 1.51 and

Gas outgoing through lines 5 and 7 consists of an overflow 14 used at such a height

from almost pure hydrogen chloride. 60 that in the vessel about 11 liquid is retained

The chlorination mixture obtained in vessel 1 was. The vessel had a stirrer and cooling jacket

which is provided in addition to monochloroacetic acid and dichloroacetic acid and connected to a washing column, in

also contains a small amount of trichloroacetic acid, which the reaction gas in countercurrent with acetic acid in the

is withdrawn through line 14. From it the three-step process described was washed,

the acetic acid easily, e.g. B. by distillation, 65.

distant, while a separation of monochloroacetic- Example 2

acid, dichloroacetic acid and trichloroacetic acid through The reaction vessel was filled with a mixture

Distillation because of the closely spaced 366 kg of acetic anhydride and 300 g of acetic acid each

Hour, the wash column with 606 g of acetic acid per hour were charged, and the reaction mixture per hour were fed 1250 g chlorine, where it was held atm to 13O ⁰ C and a pressure of. 4 The liquid mixture leaving the reaction vessel contained, in addition to monochloroacetic acid, 10 percent by weight acetic acid and about 2.5% dichloroacetic acid. The chlorine content of the escaping vapors was only about 1 percent by volume. The liquid reaction mixture was passed via the overflow to a separate hydrolysis vessel which was under the same pressure as the reaction vessel. Here 3.2 percent by weight of water was added to it. Anhydride and acid chlorides reacted very quickly with the water with hydrolysis. Air was bubbled through the hydrolysis mixture to remove hydrogen chloride. When the above-described procedure was carried out at a pressure of 1 atm, a large amount of chlorine flowed through the reaction solution without reacting.

Example 3

920 g of acetic acid, 330 g of acetic anhydride and 1350 g of chlorine were continuously introduced into the reaction vessel per hour. The reaction was ^{carried out at 120 °} C. and 3 atm. The outgoing reaction product contained 5 percent by weight acetic acid. For the hydrolysis of the anhydrides and acid chlorides, 2.9% water, based on the reaction product, was consumed. The content of dichloroacetic acid was about 3% ^an d the content of monochloroacetic acid was 75% · T ^he chlorine content of the escaping vapors was about 1 volume percent. The loss of acetic acid due to the escaping steam was insignificantly higher than could be calculated theoretically from pressure and temperature, ie volatile acid chlorides were effectively washed out.

Example 4

40

1220 g of acetic acid, 250 g of acetyl chloride and 1150 g of chlorine were continuously introduced into the reaction vessel per hour. The conversion was ^{carried out at ICO 0} C and 5 atm. On leaving the reaction vessel, the reaction product contained 20% acetic acid, about 2.5% dichloroacetic acid and 60% monochloroacetic acid. In order to hydrolyze the acid chlorides and anhydrides of the reaction product, the addition of 2.8% water was found to be necessary.

Example 5

280 g of 99.6% strength acetic acid, 50 g of acetic anhydride and 30 g of chlorine were continuously introduced into the reaction vessel every hour. The reaction was ^{carried out at 100 °} C. and 2 atm. The outgoing reaction product contained 15 percent by weight acetic acid, and 1.6 percent by weight of water, calculated on the reaction product, was used for the hydrolysis of the anhydrides and acid chlorides. The dichloroacetic acid content was about 3.5 percent by weight and the monochloroacetic acid content was about 72 percent by weight. The chlorine content in the escaping vapors was around 2 percent by volume.

Example 6

240 g of acetic acid, acetic anhydride and 268 g of chlorine were continuously introduced into the reaction vessel per hour. The reaction was ^{carried out at 120 °} C. and at. The reaction product leaving the reaction vessel contained, in addition to monochloroacetic acid, 10 percent by weight acetic acid and 4 percent by weight dichloroacetic acid. 1 percent by weight of water was required to hydrolyze the anhydrides and acid chlorides. The escaping steam contained 8 percent by volume of chlorine.

Claims (5)

Patent claims: 1. A process for the continuous production of monochloroacetic acid by chlorination of a mixture of acetic acid and acetic anhydride or acetyl chloride at a temperature of 9C to 140 ° C under pressure, characterized in that continuously liquid or gaseous chlorine at 90 to 14O ^{0 in the mixture to be chlorinated} C, preferably at 110 to 130 ° C, under a pressure of 2 to 6 atmospheres, preferably 3 to 5 atmospheres, in such a proportion that the liquid mixture continuously withdrawn from the reaction vessel at least 5, preferably 8 to 20, expediently no longer contains than 15 percent by weight acetic acid and its content of acid chlorides and acid anhydrides in the hydrolysis corresponds to a water consumption of 1.5 to 3.5, preferably 2 to 3 percent by weight, while the vapor mixture leaving the reaction vessel is washed with fresh acetic acid, which is then added to the reaction mixture is fed. 2. The method according to claim 1, characterized in that the withdrawn from the reaction vessel Acid chlorides and anhydrides by adding water to the corresponding acids be hydrolyzed. 3. The method according to claim 1, characterized in that there is chlorine in an amount of at least 100, preferably 300 to 1000 g per hour and liter of reaction mixture is fed. 4. The method according to claim 1 and 2, characterized in that the reaction mixture 15 to 30, preferably 20 to 30 parts by weight of acetic anhydride or acetyl chloride to 85 to 70, preferably 80 to 70 parts by weight of acetic acid feeds. 5. The method according to claim 1, characterized in that one leaves the reaction vessel Vapors treated with acetic acid in three stages in a countercurrent column, whereby the vapors are cooled in the first stage, in the second stage by washing with acetic acid organic components, such as acetyl chloride and chloroacetyl chloride, are freed and in the third stage a saturation of acetic acid by hydrogen chloride takes place, during which to saturation the acetic acid not required hydrogen chloride between the washing and saturation stage from the column is discharged. Considered publications:
German Patent Nos. 860 355, 865 739;
U.S. Patent No. 2,809,214. 1 sheet of drawings 609 757/425 1.67 © Bundesdruckerei Berlin