DE1793446A1 - Process for the preparation of dichloroacetyl chloride - Google Patents

Description

Dichloroacetyl chloride is an important compound that Used for the manufacture of intermediates in the manufacture of a number of important vinyl phosphate insecticides For example, U.S. Patent 2,956,073 Vinyl phosphates, which are useful as insecticides, by reacting halogenated acetophenones with trimethyl phosphite manufactured. According to US Pat. No. 3,102, halogenated acetophenones are produced by reacting dichloroacetyl chloride made with halogenated benzene and that

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obtained acetophenone with trimethyl phosphite to the above Insecticidal compounds implemented

Synthesis of halogenated acetophenone intermediate However, the prior art is not of particular commercial interest because of its high cost and its limitations Availability of dichloroacetyl chloride

It is known to oxidize trichlorethylene to dichloroacetyl chloride. Such methods are, for example. in the United States patents 1,976,265 and 2,292,129, but have them these processes have the disadvantage of long reaction times and there is a great loss of yield because of the formation of By-products · In this process the yield of dichloroacetyl chloride and trichlorethylene oxide is almost the same and there are also minor amounts of hexachlorobutylene, phosgene, carbon monoxide, hydrogen chloride, trichloroethylene polymers and other products of indefinite constitution obtained · The presence of trichlorethylene oxide is special undesirable because of its instability. The formation of such by-products in considerable quantities leads to a corresponding Loss of yield of dichloroacetyl chloride. In addition, the desired product must separate from the other products costly pricing procedures are separated what also leads to a loss of exploitation "

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According to U.S. Patents 1,976,265 and 2,292,129, can the trichlorethylene epoxide formed after the oxidation of trichlorethylene is converted into dichloroacetyl chloride by use secondary and tertiary amines are converted · Here, however, special mention is made that during the initial oxidation the trichlorethylene is free of secondary and tertiary Amines is said to be, since it is known that such amines are chlorinated hydrocarbons, such as trichlorethylene, against oxidation stabilize.

The two-step process according to the prior art, which involves the oxidation with subsequent conversion of the product with an amine to isomerize the trichlorethylene oxide exists, is moreover difficult to carry out on an industrial scale because of the expense of additional devices and the necessary work-up of the products from the two stages. In addition, the isomerization of the oxide is a strongly exothermic reaction which is difficult to control in the desired catfish can·

There is therefore a need for an industrial-scale process which allows trichlorethylene to be oxidized in one step to give pure dichloroacetyl chloride in high yield and in a short reaction time, with only negligibly small amounts of trichlorethylene oxide, phosgene and other undesirable by-products being formed.

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The disadvantages of the known methods are avoided by the method according to the invention. The process according to the invention for the preparation of dichloroacetyl chloride by oxidation of trichlorethylene in the presence of oxygen or an oxygen-containing gas at a temperature between 50 and 250 ^° C. in the presence of a catalyst is characterized in that the reaction takes place in the presence of a catalytic amount of an azo compound of the general formula

R. R. 1 t t R. R-C-N = N-C-R ι R.

in which at least one and preferably both carbon atoms bonded to the azo group are tertiary carbon atoms and in which R is a hydrogen atom, a cyano group, a calbalkoxy radical, an alkyl group with 1-6 carbon atoms or the group -R ¹ OCNH ₂ , in which R 'is an alkyl group with up to 6 carbon atoms, means, and is carried out in the presence of a catalytic amount of a secondary amine with up to 12 carbon atoms, a tertiary arylamine with up to Ik carbon atoms or a tertiary alkylamine with up to 18 carbon atoms.

The invention is in a one-step "process by reacting trichlorethylene in the liquid phase with a

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oxygen-containing gas carried out at elevated temperature in the presence of the catalysts and under the conditions mentioned. The gas can be pure oxygen, air, oxygen-enriched air, or an inert gas that contains significant amounts of molecular oxygen. The gas can be injected under pressure through a glass frit. The stoichiometric ratios in the reaction show that only 0.12 kg of oxygen is required per kg of trichlorethylene. Thus, complete oxidation is achieved, however, is the use of a stoichiometric excess of preferred amounts above 100 weight _o -? A excess of oxygen, based on trichlorethylene can without adverse effect be used on the yield · Under the superatmospheric pressure at which the reaction proceeds However, it is desirable to use air or another inert gas containing oxygen instead of pure oxygen. The reaction speed is considerably reduced, but the risk of explosions and fires is also considerably reduced. In addition, air is the most economical oxygen-containing gas source. The feed rate of the oxygen-containing gas is preferably such that about 0.1 mol to 0.6 mol of oxygen per hour per mole of trichlorethylene are introduced into the reaction mixture.

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The trichlorethylene is reacted with the oxygen-containing gas at an elevated temperature. The temperature range is between 50 and 250 ° C, the preferred temperatures between 60 and 130 ° C.

As already mentioned, the prior art particularly points out that the oxidation of trichlorethylene to dichloroacetyl chloride should be carried out under conditions in which no tertiary amines are present. This is because these amines are known to stabilize chlorinated hydrocarbons and therefore will cause the rate of oxidation to drop to the point that such a process is no longer feasible on an industrial scale. However, the known reactions produce equal amounts of dichloroacetyl chloride and the undesired by-product trichlorethylene oxide, as well as smaller amounts of chloral, phosgene and other undesirable products. The best previously known conversions of trichlorethylene are 60 % with a yield of 70 % of dichloroacetyl chloride and reaction times of 6 hours or more.

In view of the teaching of the prior art that secondary and tertiary amines in the oxidation of trichlorethylene chloride should be absent, it is very surprising

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and unexpectedly that the combination of an azo compound and a secondary or tertiary amine in the oxidation of Trichlorethylene to form essentially pure dichloroacetyl chloride leads, with the undesirable by-products in negligible small amounts are formed.

When carrying out the process according to the invention, it was found that a conversion of about 50-80 % of trichlorethylene to dichloroacetyl chloride with the formation of only 1-3 % of undesirable liquid by-products is possible in about 1-2 hours. Because of the very short reaction time and the fact that the trichlorethylene can easily be distilled off from the reaction mixture, this result is of considerable importance on an industrial scale. Accordingly, the remaining dichloroacetyl chloride can be purified by distillation or other purification methods. The unconverted trichlorethylene can be recycled through the process and converted again to dichloroacetyl chloride. Technically, it is of particular importance that a 90 % yield of pure dichloroacetyl chloride with a conversion of almost 100 % trichlorethylene can be achieved by recycling the unconverted trichlorethylene into the process. With each recirculation, fresh trichlorethylene can be fed into the reaction mixture and thus a continuous process can be obtained «

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In addition, the process according to the invention can be carried out batchwise, the trichlorethylene being reacted for about 3 hours and then the unconverted trichlorethylene being easily distilled off from the reaction mixture and the mixture containing chloroacetylchloride being purified as above. Again, a conversion can be achieved close to 100% trichlorethylene at a yield of about 90 ° / o Dxchloracetylchlorxd ·

The azo compounds used according to the invention have the general formula

R. R. t I. R-C-N ■ N-C-R I. t R. R.

in which at least one and preferably both carbon atoms bonded to the azo group are tertiary carbon atoms and R is a hydrogen atom, a cyano group, a carbalkoxy radical, an alkyl radical of 1 to 6 carbon atoms or the group -R ¹ CONH ₂ , in which R «is an alkyl group with up to to 6 carbon atoms is meant

In the case of the preferred azo compounds, both valences of the azo group -N = N- are on different tertiary carbon atoms

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bonded further to at least one of the groups -CN, -CONH or to a carbalkoxy radical having 2-7 carbon atoms are bound, the remaining valences are bound to CH_, as this is the most effective azo compounds are within the preferred temperature range of 60 - 130 C «

Examples of such azo compounds, in the formula of which R is a cyano group, a hydrogen atom or an alkyl group are the following:

s-> c, oc * -azobisisobutyronitrile,

oC fkJ ¹ -Azobis £ * - methylenanthonitril), cf-fl ^ -Azobis ££, ^ - dimethylvaleronitril), cc, CX - * - Azobis fcC-ethylbutyronitrile),

Azobis i ^ -methylbutyronitrile), o ^ jO ^ '- Azo-dicyclohexanecarbQnitril, and oC, oC ^f -Azobis- ££ _t ° ^' - cyclopropylpropionitril).

Examples of azo compounds, in the formula of which R is a carbalkoxy radical having 1-7 carbon atoms, a hydrogen atom and or is an alkyl group having 1-6 carbon atoms

Methyl ~ oC _t oC * -azodiisobutyrate, ot _t oL * -azobis (o £ ,, ^ f-dimethylvalerate), -azodiisobutyrate and -azodiisobutyrate.

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Examples of azo compounds in whose formula R is a hydrogen atom and / or the group R ^{1 is} CONH ₂ in which R ^{1 is} an alkyl radical having up to 5 carbon atoms

o ^ jot'-azodiisobutyramide and / pCjCpC'-Azobisioi-jT-dimethylcaproamide).

The most preferred azo compound is isobutyronitrile.

Dasoi-, oi -'- azobisisobutyronitrile becomes the reaction mixture added in catalytic amounts. The amount of azo compound required based on the weight of the reaction mixture is 20-2000 parts per million parts, with 100 to 1000 parts per million parts being preferred.

In the case of continuous recycling of the unconverted starting material and short reaction times, it is possible.

the azo compound as initiator continuously in the Reaction container entered. In the case of paragraph-wise Working, the azo compound need only be added at the beginning of the reaction. However, it can also be used during the Implementation can be added programmatically.

The oxidation of trichlorethylene with an oxygen containing inert gas at elevated temperature in the presence

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a catalytic amount of the azo initiator is carried out at atmospheric pressure to above atmospheric pressure. Superatmospheric pressures are preferred because the increased pressure forces more oxygen into the solution and thereby making more oxygen available for conversion. The Trichiοrät hy 1en can therefore selectively with high sales and be oxidized in a relatively short reaction time. Pressures of 1-100 atmospheres are generally used, where Pressures of 2-20 atmospheres are preferred. Particularly preferred are pressures of 3 - 12 atmospheres.

The secondary ones useful in the process of the invention Amines are alkylamines and cyclic amines with up to 12 carbon atoms such as dimethylamine, diethylamine, dihexylamine, Pyridine, picoline and piperidine.

Also usable according to the invention are tertiary arylamines with up to 14 carbon atoms, such as Ν, Ν-dimethylaniline, N, N ~ dipropylaniline, N-methyl-N-ethylaniline and N, N-dibutylaniline.

In the method according to the invention are particularly preferred tertiary alkylamines with up to 18 carbon atoms, such as Trimethylamine, tributylamine, trihexylamine and tri-n-propylamine.

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The amine can be in the reaction table in Mensen of between about 30 to 1,000 parts per million based on the weight of the reaction mixture can be added. the preferred amine concentration is between about 80-150 parts per million, with about 100 parts per million Parts are particularly preferred and triethylamine is the preferred amine.

Contamination of the reaction mixture in the case of the invention Procedures involving iron or copper should be avoided. It has been found that when the surface or the Lines of the reactor through which the reactants are passed contain metallic iron or copper, a considerable amount of chloral is formed, which reduces the rate of the reaction. This difficulty is solved, that the lines and reaction vessel D) made of other metals, such as nickel, or made with it are lined »Even non-metallic lined lines or reaction vessels, e.g. made of glass or ceramic materials or lined with them, are suitable

The new and unexpected improvements achieved by the process according to the invention are made possible by the The following examples are explained, with the proportions

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are given in parts by weight, unless otherwise stated _o ■

example 1

In the following Table I are some attempts at Oxidation of trichlorethylene (TCE) indicated, carried out in the absence of triethylamine * Another ^ b The experiment was carried out with the addition of 100 parts per million parts of triethylamine. The selectivity of oxidation was found by the ratio of trichlorethylene oxide (TCEO) to dichloroacetyl chloride (DCAC) that was found in the reaction product was expressed.

The reactions were carried out in a glass tube 2 cm in diameter carried out using 60 ml of trichlorethylene as a reactant and oxygen with a

■ · speed of 0.32 mol per hour was initiated,

which is dried over a 5 angstrom molecular sieve had been, the temperature was 80 ° C and the pressure i Atmosphere · The initiator used was, oC'-azobisisobutyronitrile (ABIN) used For comparison purposes, a batch with tert-butyl hydroperoxide, TBH, was also carried out.

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Table I - Effect of the amine

TCE selectivity Triäthylaeim initiator Halftime TCEO / DCAC ppm ppm t 1/2 hour 1.30 O 1000 2.6 1.06 0 1000 2.7 0.02 ιοα 1000 3.1 1.34 0 100 5.9 1.24 0 100 7.4 1.09 0 ioo ^b) 13th

a) Reaction time for the oxidation of half the amount of Triclilorät-hylen

b) tert-butyl hydroperoxide, TBH, instead of ABIN

As can be seen from Table I, if no triethylamine is used in the reaction, the trichlorethylene poxide is contained in a larger amount in the product and dichloroacetyl chloride in an amount of less than 50 %. However, when 100 ppm triethylamine was used for the reaction, the ratio TCEO / DCAC was 0.02, which means that TCEO was present in the product in a concentration below 1 % .

The experiments also show that the half-time of the reaction is not noticeably extended by the presence of triethylamine became when 1000 ppm ABIN as initiator at atmospheric pressure were present·

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A comparison of the half-life of trichlorethylene in that Experiment using tert-buty! Hydroperoxide as Initiator at half time in the experiments using the azo compound shows that the trichlorethylene is oxidized two to six times as fast in the presence of the azo compound.

Example 2

The following Table II shows the effect of varying amounts of ABIN as initiator and of the triethylamine catalyst according to the process according to the invention. The experiments were carried out according to a continuous process with recycling of unreacted starting material in a reactor with a capacity of 10 liters at elevated temperature and pressure. The rate of production of the continuous reaction is given in g / ^ e "hour, which means that this number of g / € hour was withdrawn from the reaction vessel and replaced with an equivalent amount of trichlorethylene. The product was analyzed by gas chromatography, with the results are given in Table II.

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After the first hour, the product was analyzed by gas chromatography. As can be seen from Table II, only 3-6% undesired by-products were produced, but 49-68% DCAC, the remainder being TCE, which can be recycled to the reaction vessel.

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Table II - Continuous oxidation of trxchlorethylene to dichloroacetyl chloride

Temp .. ⁰ C Pressure. Air injection ABIN- Triethyl Product Analysis% other TCE rCEO DCAC lid floor sung, Initiator, amine, operational Next to 127 119 10 Liters / hour ppm ppm dizzy * hosgen Products 47.29 0.92 49.10 125
125 120
122 10
10 2900 422 92 speed
g / hour It 5.8 43.18
40.90 0.6l
0.53 53.33
53.68 125 122 10 2900
2900 988
500 82
50 12,532 1.11 1.50
3.57 27.46 0.86 67.43 α
tC
CO
CS 125
125 122
122 10
10 1700 1359 136 8.331
11,000 1.36
1.32 2.71 27.59
37.69 0.63
1.73 67.85
57.68 CT 1700
2900 1133
500 113
50 3,963 1.53 2.34
1.46 -J
00
cn 4,986
11,000 1.54
1.44

Example 3

When trichlorethylene in the presence of oxygen too Dichloroacetyl chloride according to Example 1 in the presence of a catalytic amount, such as 100 ppmt ^, oO-Azobisirt-eiianthonitril) and a catalytic amount of dihexylamine at 100-1% 0C and pressures between 2-10 atmospheres can be implemented the unreacted trichlorethylene from the reaction mixture be distilled off after a reaction time of about 2 hours. The remaining reaction mixture consists mainly of Dichloroacetyl chloride, which can be further purified by distillation or other purification methods.

The relatively pure trichlorethylene which is distilled off from the reaction mixture can then be reintroduced into the process in a continuous manner. Further trichlorethylene can be added in the recycling to replace the dichloroacetyl chloride. According to this process, yields of up to 90 % dichloroacetyl chloride are achieved with a conversion of almost 100 % trichlorethylene.

Example 4

If trichlorethylene is oxidized intermittently to dichloroacetyl chloride in the presence of oxygen, in the presence of about lOOO ppm < ^{3 <} - _l ^ot - ^l -azobis (ci6 _t ^ '-. Dimethylvaleramide) and about 500 ppm tri-n-propylamine at a temperature of about

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140 ° C and a pressure of about 15 atmospheres, pure dichloroacetyl chloride is distilled off after a reaction time of about 3 - ^ hours. Yields of about 90 % dichloroacetyl chloride can be achieved with a conversion of trichlorethylene close to 100 % .

Example 5

If trichlorethylene is oxidized in the presence of oxygen by the continuous process of Example 2 in the presence of about 250 ppm methyl- ^ jOC'-azodiisobutyrate and about 3OO ppm piperidine at a temperature of about 150 ° C. and a pressure of about 3 atmospheres, pure Dichloroacetyl chloride can be distilled off after a reaction time of 2 hours.Yields of about 90 % dichloroacetyl chloride with a conversion of trichlorethylene close to 100 % can be achieved by returning unreacted trichlorethylene to the reaction vessel.

Patent claims

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Claims (7)

Claims 1 · Process for the preparation of dichloroacetyl chloride by Oxidizing trichlorethylene in the presence of oxygen or an oxygen-containing gas at a temperature between 50 and 250 C and in the presence of a catalyst, man
characterized in that / the reaction in the presence of a catalytic amount of an azo compound of the general formula R. R. 1 1 t R-C-N = N-C-R f R R in which at least one and preferably both carbon atoms bonded to the azo group are tertiary carbon atoms and R is a hydrogen atom, a cyano group, a carbalkoxy radical, an alkyl radical of 1-6 carbon atoms or the group -R ¹ OCNH, in which R 'is an alkyl group with up to 6 carbon Approx atoms is, means, as well as in the presence of a catalytic Amount of a secondary amine with up to 12 carbon atoms, a tertiary arylamine with up to 14 carbon atoms and / or a tertiary alkylamine with up to 18 carbon atoms performs. 10 9885/1786 2. The method according to claim 1, characterized in that an azo compound is used in whose formula R has a cyano group, a hydrogen atom or an alkyl group Is 1-6 carbon atoms. 3. The method according to claim 1 or 2, characterized in that that one uses as azo compound ^, <λ'-azobisisobutyronitrile . . k . Process according to Claims 1 to 3, characterized in that a temperature between 60 and 150 C is used. 5. The method according to claim 1 to 4, characterized in that that one works at a pressure between 2 and 20 atmospheres. 6. The method according to claim 1 to 5t, characterized in that that the implementation is carried out in an environment that is free of iron and copper is " 7. The method according to claim 1 to 6, characterized in that the reaction is carried out continuously in a time between 1 and 3 hours with removal of the dichloroacetyl chloride formed and returning the unreacted trichlorethylene to the reaction vessel. 109885/1786