CA1041117A - Production of salts of chlorinated acetic acids - Google Patents

Abstract

PRODUCTION OF SALTS OF CHLORINATED ACETIC ACIDS

ABSTRACT OF THE DISCLOSURE:

Production of alkali metal, ammonium or alkaline earth metal salts of chlorinated acetic acids by reacting said chloroacetic acids with suitable bases and salt-forming derivatives thereof. The salts are produced by reacting the chloroacetic acid and the basic compound at temperatures within the range 20 and 150°C by introducing them into a fluidized bed reactor, the bed being prepared from resulting salt and being fluidized by means of an inert gas or in an inert liquid, and resulting readily flowable salt is discharged from the fluidized bed reactor continuously or intermittently, at the same rate as it is being formed.

Description

104111~ -Salts of chlorinated acetic acids, especially the sodium salts of monochloroacetic acid and trichloroacetic acid, respectively, have gained considerable commercial interest. The compounds can be made by various pro-cesses which substantially comprise neutralizing chlorinated acetic acids with suitable bases. The starting materials used therein are the pure acids, which may be used in solid form, in the form of a melt or an aqueous solu-tion, and the hydroxides or carbonates of alkali metals or alkaline earth metals or ammonium. The basic compounds are used in substance, in aqueous solution or in suspension. In these processes, it is necessary for the re-action conditions to be selected so that secondary reactions of the result-ing chloroacetic acid salts are substantially avoided. These compounds are, however, known to be highly hydrolyzable so that it is necessary to even avoid local superheating of the reaction mixture which may be sufficient for .
them to commence hydrolysis, especially in the presence of water, to sodium chloride and polyglycolides, for example, in accordance with the following equation:
ClCH2-COONa ~aC1 + 1 (CH2-COO)n.

In the presence of sufficient water, the hydrolysis occurs to an increasing extent alone with increasing temperatures as shown, e.g. by the following equation:
C13C-COONa + H20 ~C13CH + NaHC03-Propoaala have already been made to avoid auch decompo~ition re-actions, which provide: for the starting materials to be used in admixture with reduced quantities of water or for the water added to be removed at once together with the water of neutralization, for the reaction to be ef-fected at temperatures as low as possible during short periods, or for a certain pH-range to be maintained during the neutralization in aqueous medi-um.
German Patent Specifications 860 354 and 871 890, for example, disclose processes which take place as shown by the following equation

2 ClCX2-COOH + ~a2C03 - ~ 2 ClCH2-COO~a + C02 + H20 ~0~
wherein stoichiometric proportions of crystalline or molten monochloroacetic acid and anhydrous alkali metal carbonates are mixed together and the re-sulting mixture, which is ground for some prolonged time at low temperatures to complete the reaction, is either introduced into a solvent, preferably into the molten liquor of the particular alkali metal chloroacetate, or rapidly and extensively reacted at about 70 C and dehydrated thereby. This has been shown in German Patent Specification 871 890 to result, after about 30 minutes, in the formation of an alkali metal chloroacetate containing 1 weight % of water and 0.24 weight % of NaCl.
United States Patent Specification 2 613 220 or British Patent Specification 706 440, which substantially corresponds thereto, describes a process for making trichloroacetic acid salts, wherein calcined sodium car-bonate, for example, is reacted at 60 C within 1 hour with commercial trichloroacetic acid (cf. Examples VI in each of these two specifications).
The product obtained as shown by the following equation 2 C13C-COOX + Na2C03 -~ > 2 C13C-COONa + C02 + H20 contains 1.96 weight % of NaCl and 0.82 weight % of water.
A further process, which provides for the contact periods to be shortened, whereby it is naturally made possible to use higher temperatures, has been described in British Patent Specification 782 479, wherein a melt of monochloroacetic acid is neutralized in a spray tower by means of concen-trated sodium hydroxide or sodium carbonate, which may take the form of finely pulverulent material or the form of a concentrated solution or SU8-pension. As disclosed in Example 5 of that specification, sodium carbonate is sprayed together with hot air of 100C and Jointly with molten mono-chloroacetic acid into the spray tower. The resulting salt, which has not been tested for its content of water, contains 0.4 weight % of chloride or o.66 weight % of NaCl.
German published Specification "Auslegeschrift" 2 225 867 de-scribes a process, wherein aqueous solutions of alkaline liquors and mono-chloroacetic acid are mixed together, contacted with one another for a period of less than 10 seconds, preferably less than 1 second, and sprayed - 2 - ~ ~

,.'' ~;' ,':' under reduced pressure with the resultant formation of salt suspensions.
A still further process for making trichloroacetic acid salts has been described in German Patent Specification 1 113 450, wherein a free or carbonic acid base, preferably an anhydrous base, is neutralized by means of 88 - 94 weight % aqueous trichloroacetic acid with the resultant formation of a crystalline magma, which is maintained at a pH-value within the range .
6 and 8. The 94 weight % anhydrous pulverulent sodium trichloroacetate so ..: ,. .
obtained is said to have an apparent density (bulk density) of less than 1 and non-coalescent properties, once it has been dried at 60 C under reduced pressure, and pulverized.
Those processes, which are carried out substantially in the ab- ;
sence of moisture or which provide for the moisture to be rapidly expelled as, e.g. in a spray drying process, normally give fine-powdered material which tends to coalesce. On the other hand, it is highly desirable for the .
chloroacetic acid salts to present a given particle size, particle size dis-tribution and flow properties, as these are factors which critically deter-mine the ease of handling, and the solubility of, the salts during process-~ .
ing.
Looking to the prior art in this field, it would scarcely appear possible to provide a commercially really attractive process producing highyields of chlorinated acetic acid salts containing little water and impuri-ties from secondary reactions, and having good flow properties.
In clear contrast with these adverse aspects, the present inven-tion now unexpectedly provides a fully satisfactory process for making alka-li metal, ammonium or alkaline earth metal salts of chlorinated acetic acids by reacting the chloroacetic acids with suitable bases and/or salt-forming deriv~tives thereof, which comprises reacting the chloroacetic acid and the basic compound at temperatures within the range 20 and 150 C by introducing them into a fluidized bed reactor, the bed being prepared from resulting salt and fluidized by means of an inert gas or liquid; and discharging re-sulting readily flowable fresh salt from the fluidized bed reactor continu-ously or intermittently at the same rate as it is being formed.

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104i~17 Further preferred embodiments of the present invention provide:
a) for liquid or dissolved chloroacetic acid to be introduced into the fluidized bed reactor, b) for the chloroacetic acid to be sprayed into the fluidized bed re-actor;
c) for a chloroacetic acid melt to be introduced in vapor form by means of an inert gas into the fluidized bed reactorj d) for the basic compound to be introduced in substance, in solution or suspension into the fluidized bed reactor, e) for the basic compound to be an oxide, hydroxide, carbonate or a~monia;
f) for the fluidized bed to be formed at the onset of the reaction by fluidizing the solid basic compound with an inert gas or in an inert liquid;
g) for air, nitrogen or carbon dioxide to be used as the inert gas;
h) for a chlorinated aliphatic hydrocarbon to be used as the inert liquid;
i) for the reaction to be effected at temperatures within the range 50 and 120 C; and ~) for the starting materials to be introduced into the fluidized bed reactor continuously and at the same rate as readily flowable final salt is continuously di~charged therefrom.
It is an advantage of the pre~ent invention that it ls possible for it to be carried out at relatively high temperatures as the neutraliza-tion is always accompanied by the evolution of heat, for which it i~ then necessary to be dissipated to some reduced extent, by cooling. The rapid heat exchange, which occurs within the bed of fluidized material, enables the phenomenon of local superheating as well as undesirable secondary reac-tions to be inhibited, for example the formation of polyglycolides referred to hereinabove. The important heat transfer coefficients make it possible for the reaction temperature to be regulated without difficulty.
The process described in Germ~n Patent Specification "Auslegeschrift" 2 225 867 is carried out in two stages and compares un-_ 4 -lir~favorably in this respect with the present invention. The first stage com-prises pre-heating, and the second stage comprises drying the material, nat-urally with considerable expenditure of energy. In clear contrast with -, this, reaction water in the present process is eliminated by means of the heat set free during neutralization. While the present and the prior art :
processes do substantially not differ from each other in respect of the ex-penditure necessary for the exhaustion of C02 and steam, the fact remains that the prior art methods, wherein motor-driven mixer sets series-connected to mixers are used, entail considerable expenditure of mechanic energy.
The nature and quality of the resulting chloroacetates are sub-stantially not affected by the starting materials, irrespective of whether they are reacted intermittently or continuously.
Loss of material, ~hich may be caused by volatile reactants, can be avoided by circulating the fluidization inducing agent. In this event, it may be necessary for it to be freed from undesirable components, e.g.
water contained therein.
The process of the present invention can be used for fluidizing all those chloroacetic acid salts which have a particle size admitting the formation of a fluidized bed. It is also possible, however, in an apparatus conformed to the process of the present invention to use a solid ba~ic com-pound, e.g. an aIkali metal carbonate, and to effect the process continu-ously or intermittently therein.
Irrespective of whether the process is carried out continuously or batchwise, it provides for the fluidized bed to be modified in known manner so as to form a flow bed. In this event, depending on the particular case, an inert liquid, which preferably is a chlorinated Pliphatic hydrocarbon, e.g. CHC13, CC14 or trichloroethane, may be substituted for, or used togeth-er with, the inert gas (inert with respect to the starting material and re-action product).
A particular advantage associated with the present process resides in the fact that the relatively long contact times do not affect its econ- ~
omy. The Muidization technique enables the process to be carried out in an ~ -..~
. ~... . .

1041~17 apparatus substantially of whatever dimensions, awaiting little maintenance and repair. In other words, individual reactors may be arranged so as to form a plurality of stages or may be grouped together. In this event, the process can be effected under even more attractive conditions as it is then possible, for example, for a series of grouped reactors to be arranged down-stream of each other, with respect to the gas flowing therethrough. It should be added that reactors which are so arranged can be operated at rel-atively low working costs.
Purity and particle size are the factors which critically deter-mine the nature of the resulting chloroacetic acid salts. Products which contain relatively high proportions of water and high proportions of fines (within the spectrum of the particles) tend to cake together. Agglomerated salt is in fact capable of absorbing water, but it dissolves ver~ reluc-tantly therein, whereby processing is rendered difficult. In other words, during the long periods necessary for agglomerated material to dissolve, the material is subject to partial hydrolysis which occurs prior to its dissolu-tion being complete. Needless to say, the yield of secondary products is impaired thereby.
It is therefore advantageous for the well flowable salts of the present invention to contain less than 0.5 weight % of water, less than 0.5 weight %, preferably less than 0.2 weight %, of alkali metal, alkaline earth metal or ammonium chlorides, and to present the following particle siæe dis-tribution, in mm, more than 0.40 less than 20 %
0.40-0.20 20-40 %
0.20-0.063 50-70 %
less than 0.063 less than 10 %
The present invention is also of interest for its variability. It admits of wide variations relative to the reaction conditions and relative to the starting materials (e.g. mono-, di- or trichloroacetic acid for use as acid components, and oxides, hydroxides or carbonates of alkali metals, -alkaline earth metals or ammonium for use as basic components), which may be .
-' 1041~17 used e.g. in substance (solid, liquid or gaseous) in aqueous solution or in water or another liquid).
The present invention will now be further described by way of the following examples and with reference to the accompanying drawings, in which:
Figure l is a diagrammatic representation of a commercial plant, in side elevation, for the production of sodium monochloroacetate, Figure 2 is a diagrammatic representation of a laboratory appara-tus, in side elevation, for the discontinuous production of sodium mono-chloroacetate, Figure 3 is a diagrammatic representation of a modified form of the apparatus in Figure 2 for the continuous production of sodium mono-chloroacetate, and Figure 4 is a diagrammatic representation of apparatus, in side elevation, for the discontinuous production of sodium monochloroacetate in suspension.
EXAMPLE 1: (cf Figure 1) Production of sodium monochloroacetate in a commercial plant.
A fluidized bed reactor 1 (glass or enamelled steel) which was 4 m long and 250 mm wide was supplied with a stream of air (about 40 cubic meter/h). The air coming from a conduit 3 and conveyed through a heater 4 was in~ected into the reactor l, having a perforated bottom 2. ~he material to be fluidized was about 12 kg of sodium monochloroacetate. 3.3 Kg/h of liQuid monochloroacetic acid containing about 20 weight % of water was in-~ected through conduit 5 and sprayed on to calcined sodium carbonate, of which 1.5 kg/h coming from a reservoir 6 was introduced into reactor 1, by means of a screw conveyor 7. Particulate solid matter from reactor l was found to settle in a calming~zone 8 conically enlarged to reduce the veloc-ity of flow, and to drop back into reactor 1. Fines carried along with the stream of air were delivered through a conduit 9 to a cyclone separator 10 and separated therein. ~he off-gas (air and C02) issued from the apparatus through a conduit ll. The fines collected in cyclone separator 10 were added discontinuously, through a lock 12, to sodium carbonate flowing through .. . .. . .. .. . . ...

10~1~17 conduit 13. The fluidized bed reactor 1 was heated to the optimum reactiontemperature of about 90 C. Over its entire length, the reactor was provided with altogether 14 temperature and pressure control means. A heat carrier was circulated in conduit 16 and delivered by means of pump 17 to a heat ex-changer 15 to provide for the dissipation of the heat of neutralization, if desired or necessary. Circulation conduit 16 was also used for preheating the material to undergo reaction, prior to the start-up. ~he solid material to be fluidized (about 12 kg), which consisted initially of sodium carbonate and later, after about a 4 hour starting period, of final product, had a temperature of about 90 C. It was maintained at that temperature by means of the heat exchanger system (15-19) (this was controlled with the aid of temperature sensitive elements 14) and kept in motion by the air injected.

3.2 kg of sodium monochloroacetate was discharged continuously through out-let 20.
The product was obtained substantially in quantitative yield. It was analyzed and the following result was obtained:
Sodium monochloroacetate: about 99 weight %
Sodium chloride 0.3 weight %
Water 0.2 weight %
Monochloroacetic acid 0.2 weight %
pH 5-8 EXAMPLE 2:
Preparation of sodium monochloroacetate in a laboratory device.
a) Discontinuous operation (cf. Figure 2) The experimental apparatus of Figure 2 was used. It corresponded substantially to the apparatus of Figure 1, but its principal element was a ~acketed heatable glass tube which served as fluidized bed reactor 21. ~he tube was 1 m long, had an internal diameter of 50 mm and was provided with a frit inlet 22 sealed therein. Placed above reactor 21 was the conically en-larged calming zone 8, in which fine particulate material was separated and returned back to the reactor 21. Fines were discharged through dust col-lector 10 placed downstream thereof.

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: ' 10411~
Sodium monochloroacetate was made batchwise. To this end, reactor 21 was supplied with 410 g of anhydrous sodium carbonate, which was fluid-ized at 80-100 C by means of 2.2 cubic meter of nitrogen as the inert fluid-izing gas flowing through conduit 23. The receiver 24 containing 1150 g of molten monochloroacetic acid was maintained at 80 C and the resulting acid in vapor form was injected together with the fluidizing gas into reactor 21.
The reaction was terminated after about 8 hours. As a result of such grad-ual reaction, the fluidized material was no longer sodium carbonate. It consisted almost completely of pure sodium monochloroacetate, which was dis-charged (850 g) under the pressure of the nitrogen gas, through outlet 30 arranged upstream of frit 22. 400 g of monochloroacetic acid was retained in the receiver.
In Figure 2, the reference numerals 8-12 and 14 have the same meanings as in Figure 1.
b) Continuous operation (cf. Figure 3) Monochloroacetic acid was reacted continuously with calcined sodi- ;
um carbonate. To this end, it was necessary for the experimental apparatus described under a) above with reference to Figure 2 to be modified so as to substantially correspond to the apparatus shown in Figure 1. The modified apparatus (cf. Figure 3) was more particularly provided with an inlet open-ing into the upper portion of the heated fluldized bed reactor 21. 40 g/h of sodium carbonate coming from reservoir 6 wa~ introduced by means of screw conveyor 7 into reactor 21 through the said inlet, and freshly formed sodium monochloroacetate (86 g/h) was continuously discharged, through outlet 30.
The material to be fluidized was 600-800 g of sodium monochloroacetate, e.g.
that produced in the apparatus described under a) above. 73 g/h of mono-chloroacetic acid was consumed. It was replaced by the introduction of a corresponding quantity of fresh acid into receiver 2~.
In Figures 1 and 2, respectively, the reference numerals 6-14 and 21-25 and 30 identify identical parts.
The products obtained as described under a) and b) above were rel-atively coarse, yet readily flowable material. They had an apparent density _ g _ .. . . .

~0411~7 ~ -o~ about 0.8 kg/1 and the following particle size distribution:
> 0.4 mm 11.7 % 0.2-0.063 mm 59.9 %
0.4-0.2 mm 26.2 % < 0.063 mm 2.2 %
The products were obtained in almost quantitive yields, based on monochloroacetic acid. The final products were analyzed and had the follow-ing mean composition:
sodium monochloroacetate: 99 weight %
Sodium chloride< 0.2 weight %
Water < 0.1 weight %
pH 6.8 EXAMPLE 3: (cf. Figure 4) Production of sodium monochloroacetate in suspension (discontin-uous operation).
A heatable fluidized bed reactor, such as that shown in Figure 4, having a capacity of about 2 1 and provided with a by-pass conduit 32, was supplied with a suspension of 159 g of anhydrous sodium carbonate in 1800 cc of carbon tetrachloride, 285 g of molten monochloroacetic acid dissolved in 300 cc of warm carbon tetrachloride was added dropwise thereto, through in-let 33 within 2-3 hours, while about 200 cc/h of carbon tetrachloride was ~
simultaneously distilled off through line 34, together with the bulk of re- !
action water. After condensation in cooler 35, the water was separated ~rom the specifically heavier carbon tetrachlorid0, through conduit 36. Metered quantities of carbon tetrachloride were recycled through conduit 37 into re-actor 31 80 as to maintain the liquid at a level above the highest level of conduit 32. Steam (water and CC14) and reaction gas (C02) enabled the ma-terial to be maintained under circulation and the fluidized bed to be main-tained in liquid phase. ~he off-gas issued through conduit 38. In order to ~;
complete the reaction, 200 cc/h of carbon tetrachloride was distilled off over a period of a further 2 hours and condensate was refluxed to make up for the 108s of material. Following this, the suspension was discharged through outlet 39. Carbon tetrachloride was separated, the material was dried and 348 g of sodium monochloroacetate was obtained in a yield of 99 %.

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., ,: ., ~411~7 ~

The product contained 0.2 weieht % of sodium chloride and 0.1 weight % of water. It had good flow properties.
EXAMPLE 4:
Production of potassium trichloroacetate (discontinuous operation).
An apparatus such as that shown in Figure 4 was used and a suspen-sion of 69 g of potassium carbonate in lôOO cc of carbon tetrachloride was reacted therein with a solution of 170 g of trichloroacetic acid in 300 cc of carbon tetrachloride, in the manner described in Example 3. Carbon tetrachloride was separated, the material was dried and 191 g of potassium trichloroacetate was obtained in a yield of about 95 %. The product showed an alkaline reaction (pH 9.2) as it still contained 0.5 weight % of potas-sium carbonate, less than 0.1 weight % of potassium chloride and traces of water.
EXAMPLE 5:
Production of ammonium monochloroacetate (continuous operation).
An apparatus such as that shown in Figure 4 was provided at its bottom portion with a gas inlet opening thereinto and used for making am-monium salts of chloroacetic acid therein. Ammonium monochloroacetate was made. To this end, a suspension of 220 g of that compound in 2 liter of carbon tetrachloride was introduced into reactor 31. 30 l/h of NH3 was added continuously at 20-50 C together with a solution of 95 g o~ molten monochloroacetic acid in 1 liter of warm carbon tetrachloride, which was added dropwise, while a proportionate quantity of salt suspension was dis-charged from the apparatus, through outlet 39. The resulting product was flltered and dried, and a~monium monochloroacetate was obtained almost in quanbitative yield. To achieve this, it was necessary to recycle the ammo-nia in excess. The final product had good flow properties and contained less than 0.1 weight % of ammonium chloride.

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Claims (12)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A process for making a substance selected from the group con-sisting of alkali metal, ammonium and alkaline earth metal salts of chlori-nated acetic acids by reacting said chloroacetic acids with at least one member selected from suitable bases and salt-forming derivatives thereof, wherein the chloroacetic acid and the basic compound are reacted at tempera-tures within the range 20 and 150 C by introducing them into a bed prepared from resulting salt and fluidized by means of an inert gas or in an inert liquid, and resulting readily flowable salt is discharged from the fluid-ized bed zone continuously or intermittently, at the same rate as it is being formed.

2. The process as claimed in claim 1, wherein liquid chloroacetic acid is introduced into the zone of the fluidized bed.

3. The process as claimed in claim 1, wherein dissolved chloro-acetic acid is introduced into the zone of the fluidized bed.

4. The process as claimed in claim 1, wherein the chloroacetic acid is sprayed into the zone of the fluidized bed.

5. The process as claimed in claim 1, wherein a melt of chloroacetic acid is introduced in vapor form by means of an inert gas into the zone of the fluidized bed.

6. The process as claimed in claim 1, wherein the basic compound is introduced in substance, in solution or suspension into the zone of the fluidized bed.

7. The process as claimed in claim 1, wherein the basic compound is a member selected from the group consisting of oxides, hydroxides, carbon-ates and ammonia.

8. The process as claimed in claim 1, wherein the fluidized bed is formed at the onset of the reaction by fluidizing the solid basic compound by means of an inert gas or in an inert liquid.

9. The process as claimed in claim 1, wherein the inert gas is a member selected from the group consisting of air, nitrogen and carbon diox-ide.

10. The process as claimed in claim 1, wherein a chlorinated ali-phatic hydrocarbon is used as the inert liquid.

11. The process as claimed in claim 1, wherein the reaction is ef-fected at temperatures within the range 50 and 120°C.

12. The process as claimed in claim 1, wherein the starting materi-ale are introduced into the zone of the fluidized bed continuously and at the same rate as readily flowable salt is discharged therefrom.