DE1264428B - Process for the preparation of 1-chloro-1-fluoroethane and 1, 1-difluoroethane - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Int. CL:

C07c

German class: 12 ο -2/01

Number: 1264 428

File number: M 61138IV b / 12 ο

Filing date: May 26, 1964

Opening day: March 28, 1968

The synthesis of these compounds by reacting vinyl chloride with hydrofluoric acid is known. According to German patent specification 859 887, this reaction is carried out, for example, in an autoclave Pressure by heating a liquid mixture of hydrofluoric acid and vinyl chloride for a few Hours performed at about 100 ° C. According to another described in U.S. Patent No. 2,495,407 Process can be the Reaktioa in an analogous manner at lower temperatures in the presence <n Considerable amounts of tin chloride are used as a catalyst.

This process essentially requires batch operation and use of expensive devices that deal with both the pressure and the corrosive effects of hydrofluoric acid withstand, provided that good conversions of vinyl chloride to 1-chloro-1-fluoroethane with not too high overall yields - because of the formation of larger amounts of by-products Polymerization of vinyl chloride - are to be achieved.

From the Italian patent 631 594 a process is known according to which mixtures of hydrofluoric acid and vinyl chloride in the gas phase at higher temperatures (e.g. at about 300 ° C) in The presence of suitable catalysts for the formation of 1-chloro-l-fluoroethane and 1,1-difluoroethane reacted will.

However, the benefits achieved by these methods are limited by various factors. The catalysts used, in which aluminum oxide with heavy metal salts, such as chromium, cobalt, Zirconium salts, soaked, have the major disadvantage that they quickly become inactive, they therefore often have to be regenerated.

It also occurs because of the high temperatures required in the reaction between vinyl chloride and hydrofluoric acid in the gas phase cause a large number of side reactions, often pyrolytic and lead to the formation of carbon, hydrogen, ethylene, acetylene and other undesirable by-products.

Heretofore it was believed that the addition of hydrofluoric acid to a vinyl halide and also the replacement of a halogen atom in a fluorinated haloethane by fluorine represent reactions that can only be carried out with great difficulty.

In fact, until now it has only been possible to carry out such reactions either in the liquid phase, using high temperatures and pressures.

Process for the production of
1-chloro-l-fluoroethane and 1,1-difluoroethane

Applicant:

MONTECATINI Societä Generale per

rindustriä Mineraria'e Chimica, Milan

(Italy)

Representative:

Dipl.-Ing. Dipl.-Chem. Dr. phil. Dr. techn.
J. Reitstötter and Dr.-Ing. W. Bunte,
Patent Attorneys, 8000 Munich 15, Haydnstr. 5

Named as inventor:

Dario Sianesi,

Giuseppe Nelli,

Renzo Föntanelli, Milan (Italy)

Claimed priority:

Italy of June 4, 1963 (11691)

and also in the presence of catalysts or in the gas phase at high temperatures in the presence to carry out specific catalysts.

It has now been found that the reaction between hydrofluoric acid and vinyl chloride for the purpose of producing 1-chloro-1-fluoroethane and 1,1-difluoroethane can be carried out in a continuous and surprisingly simple manner if gaseous vinyl chloride is continuously converted into liquid anhydrous hydrogen fluoride at -15 to +19 ⁰ C under normal pressure.

In an advantageous modification of the process of the invention, the reaction rate between vinyl chloride and liquid hydrofluoric acid can be increased at -15 to +30 ⁰ C under otherwise identical working conditions, if the anhydrous hydrofluoric acid is sulfuric acid, oleum, sulfuric acid hydride, phosphoric acid, phosphoric anhydride, perchloric acid, formic acid, acetic acid , Trichloroacetic acid or trifluoroacetic acid added. These compounds are somewhat catalytic. They can be used in amounts of up to 50 parts by weight, preferably in amounts of 5 to 25 parts by weight, based on 100 to 50 parts by weight of liquid anhydrous hydrofluoric acid.

809 520/687

3 4

The said compounds also cause a diluent and the hydrofluoric acid noticeable decrease * in the vapor pressure of the fluorine-containing, so that the gaseous mixture has the highest hydroic acid. It is therefore possible to have either the lowest level of the desired product and the lowest level of hydrofluoric acid in the lowest level of hydrofluoric acid. To lower the gases exiting the reactor or to carry out the re-5 The fluorine action consumed in the course of the reaction at temperatures above the hydrochloric acid, the reaction vessel can be the continuous boiling point of the hydrofluoric acid (19 ⁰ C). The upper limit of the reaction temperature can be kept constant in the liquid level therein. The extended under these conditions up to 3O ⁰ C catalyst or diluent may kontiwerden. ^! . '. can be added regularly or periodically.

According to the process of the invention, the gas stream leaving the reactor may contain

liquid hydrofluoric acid various inert 1-chloro-l-fluoroethane and 1,1-difluoroethane as well as not Substances that are miscible with it and a higher level of converted vinyl chloride and hydrofluoric acid. Boiling point than hydrofluoric acid, -The composition of such a gas mixture

can be added. 15 varies widely depending on the

Although these have no particular activity, working conditions of which, for example, the Such substances can affect the - vapor tension of the feed rate of the vinyl chloride for a Lower hydrofluoric acid and in this way the given volume of the acidic, liquid phase that Amount of hydrofluoric acid produced in the absence and concentration of a catalyst flow of the gas is entrained, limit. ao or diluent and the temperature at which

The presence of water in larger amounts the reaction zone is kept to be called (in amounts of more than 10 percent by weight of the should.

Hydrofluoric acid) should be in the reaction zone. The content of the gas mixture that the reactor avoids since * water allows the addition reaction, for 1-chloro-l-fluoroethane is 5 to 95 volumes between Hydrofluoric acid and vinyl halide 25 percent, usually 20 to 90 percent by volume. 1,1-divergence can. fluoroethane is available in quantities of up to 20 percent by volume,

The amount of that which occurs in the method of the invention is between 0.1 and 10 percent by volume 1,1-Difiuorethans can be increased, act.

when the contact time des.Vinylchlorids and the fluorine The 1-chloro-l-fluoroethane (boiling point 16.5 ⁰ C)

Hydrochloric acid can easily be removed from vinyl chloride by distillation under the same conditions is lengthened. the hydrofluoric acid are separated.

In the practical implementation of the method The method of the invention is essentially one

According to the invention, the vinyl chloride is carried out in gas fans than the previously known formers Drive the state of the reaction vessel at it.

Soil too, on which a liquid phase of water 35 Even with continuous operation over a From free hydrofluoric acid or from mixtures of longer periods of time, the losses of vinyl chloride remain hydrofluoric acid with a catalyst or relatively small that other side reactions could occur due to polymerization or diluents of the type described above, finds. Those producible by the method of the invention

It is advisable to use the vinyl chloride with a gel 40 compounds are valuable intermediates for speed from 1 to 200 l / h per liter of liquid · the synthesis of various other fluorine-containing acids To let phase flow in. Preferably holds bonds, especially 1-chloro-l-fluoroethane, to a flow rate of 10 to 100 l / h production of vinyl chloride, a. The following examples serve to explain the

The liquid 45 of the present invention contained in the reaction vessel, is kept at the chosen reaction temperature.

After a certain time, which is usually pretty exemplary

is short, the outflowing gases reach a constant Composition, which is quite a long time un- In a reactor, which is made up of a cylindrical ironchanged remain. '"" 50 vessel with an inner diameter of 12 cm and

The unreacted vinyl chloride can from. to the . 2.51 capacity and an attached reaction product or the products easily, for example flanged attachment with a gas inlet pipe, which is separated by distillation, and again reaches 1 cm above the bottom, and a gas outlet pipe reaction zone are introduced. The fluoro-hydrofluoric acid flowing out of the reactor as well as a thermometer sheath contains 1.5 kg of gases, the hydrofluoric acid can be separated off and again at a temperature of ⁰ ° C. washing with water or alkali solutions is kept away, 30 Nl / h will be dry vinyl chloride. continuously fed into the reactor.

In order to increase the conversion of the vinyl chloride into 1-chloro-60 The outflowing gases are first 1-fluoroethane with water and 1,1-difluoroethane and then washed with a 10% KOH solution to reduce the contact time between the reactants. After dewatering by passing through a core, different reactions can be carried out. 65 is applied lent, cooled to -78 ⁰ C.

The various reaction vessels can be opened. After about 3 hours, a sample of the gas is prepared

different temperatures are maintained and the condensation analyzed, with a content of different concentrations of the catalyst or 38 percent by volume of 1-chloro-l-fluoroethane and 2%

1,1-difluoroethane was determined, while the rest consisted solely of unreacted vinyl chloride.

After 8 hours of continuous reaction, the content of 1-chloro-l-fluoroethane in the from the Reactor coming gases 39 volume percent.

Asymmetric difluoroethane is present in amounts of about 3 percent by volume.

After 8 hours of total reaction, 680 g of products with an average molar composition are obtained of 38.5% 1-chloro-l-fluoroethane and 2.5% 1,1-difluoroethane condensed at low temperature and caught. The rest consists entirely of vinyl chloride. Yield of 1-chloro-1-fluoroethane (Mol per 100 mol of vinyl chloride used): 75%; 1,1-difluoroethane: 5%.

Example 2

Using the same apparatus and procedure as in the previous example, except that 0.20 kg of 98% H ₂ SO _{4 was} added to 1.5 kg of hydrofluoric acid at 0 ° C., the gas flowing out of the reaction vessel contains 53 percent by volume 1-chloro-l-fluoroethane and 1.5% asymmetric difluoroethane, while the remainder consists essentially of vinyl chloride. This composition remains practically unchanged during a 15 hour continuous reaction.

The amount of hydrofluoric acid which under these conditions by the gas stream from the Reactor exit is reduced to about a third compared to the passage in the previous example.

Example 3

A similar experiment is carried out as in the previous example, with the exception that that 50 Nl / h vinyl chloride instead of 30 Nl / h are fed.

After about an hour, with normal working conditions being reached, a level of 44 mole percent 1-chloro-l-fluoroethane determined in the outflowing gas.

Example 4

An experiment with the device described in Example 1 was carried out. After introducing 1.4 kg of anhydrous hydrofluoric acid and 0.40 kg of 98% strength H ₂ SO ₄ , 30 standard l / h of vinyl chloride were fed to the reaction vessel at a temperature of 18 ° C.

After about half an hour there is 1-chloro-l-fluoroethane in the outflowing gases Quantity of 63 percent by volume.

1,1-Difluoroethane is present in amounts of 4.5 percent by volume.

This composition remains practically unchanged after a reaction time extended to 15 hours.

Example5

An iron vessel with an inner diameter of 13 cm and 101 capacity with a flanged Extension tube up to 2 cm above the floor for the inlet of vinyl chloride and hydrofluoric acid, a gas outlet, a thermometer sheath and a measuring device for the internal liquid level is used in this example.

In the reactor lkg oleum with 25 ° / ₀ free SO ₃ and 5.5 kg of water-free hydrofluoric acid is added. While the liquid acid mixture is kept at a temperature of 13 to 15 ° C., 150 standard l / h of anhydrous vinyl chloride are continuously introduced into the reactor. The escaping gases are first washed with water and then with a 10% KOH solution and then collected in a gas container.

After half an hour, the 1-chloro-l-fluoroethane is in the gases coming out of the reactor an amount of 70 percent by volume present, while 1,1-difluoroethane is present at 2.5 percent by volume and the remainder consists entirely of vinyl chloride.

During this time the liquid level is increased by periodic additions of anhydrous hydrofluoric acid kept constant, whereupon the rate of the vinyl chloride feed increased to 300 standard l / h will.

The average composition of the gas emerging from the reaction vessel is according to a very short period of time 63 percent by volume 1-chloro-fluoroethane and 2.3 percent by volume 1,1-difluoroethane.

This composition remains practically unchanged for a further 48 hours if the procedure is continuous; during this time the liquid level of the acid mixture in the reaction vessel is increased periodically Additions of anhydrous hydrofluoric acid kept constant. Yield of 1-chloro-l-fluoroethane: 83%; 1,1-difluoroethane: 3%.

Claims (2)

Patent claims: 1. Process for the preparation of 1-chloro-fluoroethane and 1,1-difluoroethane, thereby characterized in that gaseous vinyl chloride is continuously converted into liquid anhydrous Introduces hydrogen fluoride at -15 to + 19 ° C under normal pressure. 2. Modification of the method according to claim 1, characterized in that the reaction in the presence of up to 50 parts by weight of sulfuric acid, oleum, sulfuric acid hydride, phosphoric acid, phosphoric anhydride, perchloric acid, formic acid, acetic acid, trichloroacetic acid or trifluoroacetic acid, based on 100 to 50 parts by weight of liquid anhydrous hydrogen fluoride, at -15 to + 3O ⁰ C executes. 809 520/687 3. 68 © Bundesdruckerei Berlin