NO152087B - DEVICE FOR TREATING SUBSTANCES IN LIQUID, SEMI-FLOATING OR PASTEFORM PHASE WITH ANOTHER PHASE - Google Patents

Description

Process for the production of trichlorethylene and tetrachlorethylene.

This invention relates to a method for producing trichlorethylene and tetrachlorethylene by a reaction

between copper chloride and acetylene.

Trichlorethylene and perchlorethylene are

compounds that have long been known, and

which is produced on an industrial scale,

usually with acetylene and chlorine as raw materials. The first step in the production of

trichlorethylene is the production of tetrachloroethane, which is obtained by addition chlorination

with chlorine. To obtain trichloroethylene, the tetrachloroethane is then treated with lime

or thermally cracked. As a byproduct gets

calcium chloride or hydrogen chloride, respectively.

Tetrachlorethylene is produced from trichlorethylene over pentachloroethane or by direct chlorination of acetylene in a gas reaction at 400-500°C.

It is known to chlorinate acetylene with

copper(II) chloride, e.g. from German patent no.

1 011 414, which relates to a process for the production of 1,1-dichloroethylene and trans-1,2-dichloroethylene by reaction between acetylene and hydrogen chloride in the presence of copper (II) and copper (I) ions in a ratio of from 1:4 to 1:9. It is also known to produce vinyl chloride, dichloroethylenes, mono-vinylacetylene etc. from acetylene, hydrogen chloride and copper chlorides. It is common to all these known methods that you work in strongly acidic solutions and with a high content of copper (I) ions in relation to copper (II) ions. It has now surprisingly been found that claw reaction of acetylene with copper (II) chloride gives high yields of trichlorethylene and tetrachlorethylene, if, according to the method according to the invention, one proceeds in such a way that acetylene is passed through a reaction solution containing copper (II) and copper (I) ions , where the copper (II) ions make up 50-100, preferably 70-100, mole percent of the total amount of copper, possibly chlorides of other metals, and have a pH value of 0 to 3, preferably 1 to 2.5, at a reaction temperature of at least 60°C. Other features of the method will appear from the following description.

pH is here a value measured with a gas electrode. For all pH measurements, a sample of the reaction solution was diluted with an equal amount of distilled water. Often the reaction solution has been so concentrated that a dilution has been necessary to carry out the measurement without the solution crystallising. It is obviously not correct to talk about the pH of a solution

which have ionic strengths as high as here, but the values obtained are well reproducible from one case to another.

In the reaction solution used, the monovalent copper can be oxidized to divalent with chlorine or with hydrogen chloride and oxygen, e.g. as described in German Patent No. 1,094,734 and Swedish Patent No. 178,849. The possibility of utilizing hydrogen chloride as a source of chlorine is valuable, as hydrogen chloride is obtained as a by-product in many chlorination reactions.

Trichlorethylene and tetrachlorethylene are formed at a rate that depends on the acidity of the solution and its content of copper(II) ions. In order to simultaneously achieve a high reaction rate and a satisfactory yield of tri- and tetrachloroethylene, it is preferable to work with a pH value of 1-2.5 and a content of copper(II) ions that is 70-100 mole percent of the total copper content of the reaction solution. The most favorable range for the formation of trichlorethylene seems to lie at 70-90, and for the formation of tetrachlorethylene at 85-100, calculated as mole percent copper (II) ions.

The reaction can be carried out batchwise as well as continuously.

It can be carried out in conventional equipment, e.g. in a vessel with a stirrer and a gas inlet, in a column or a tube reactor. The reaction solution is introduced into a reactor and the acetylene is introduced at a temperature of at least 60°C, suitably 80-130°C, in which case a pressure vessel is not necessary. The reaction rate can be increased by increasing the temperature above 100°C and carrying out the reaction in a pressure vessel. The reaction rate can be further increased by adding the acetylene at such a rate that a pressure is created in the reaction chamber that is higher than the pressure saturated steam has at the reaction temperature. The copper (II) chloride is reduced to copper (I) chloride while the acetylene is chlorinated. The reaction products eventually leave the reactor as vapors as they are formed.

Of particular interest is the possibility of carrying out the reaction continuously. It is then possible to use that area for the reaction, e.g. between a copper (II) ion content of 75-85 mole percent, where the reaction rate of the desired compound is highest. To ensure that the reaction compound does not crystallize due to the precipitated copper(I) chloride during possible cooling, it is appropriate to add chlorides of other metals, e.g. of ammonium, potassium, sodium, lithium, magnesium and calcium. These additives also in certain cases have an activating effect on the reaction. However, the additives limit the possibilities for working with very high copper chloride contents (more than 4 mol per litre). The latter may be desirable, when working continuously and in the area where the copper (II) ion content in relation to the copper (I) ion content is so high that the formed copper (I) chloride is kept in solution by the presence of chloride ions . It is thus important for the technical implementation of the reaction that the chloride content is high. Which cation is used to achieve this seems to be of less importance.

In the following, some examples of carrying out the reaction are described. The following abbreviations are used to indicate the reaction products formed: tri = trichloroethylene tetra = tetrachloroethylene 1,1- = 1,1-dichloroethylene cis- = cis-1,2-dichloroethylene trans- = trans-1,2-dichloroethylene

Example 1.

500 ml solution containing 255 g (= 1.5 mol) CuCl2. 2H 2 O and 102 g (= 1.5 mol) MgCl 2 . 6H2b is introduced into a one-liter retort equipped with stirrer, thermometer, gas inlet tube and cooler. The retort was placed in a heat bath to maintain the temperature at 98°C during the reaction. Carbon dioxide was introduced to drive air out of the apparatus, after which the reaction was started by introducing acetylene (10 liters per hour). The pH value of the solution was 2.3 at the start (the pH value fell to 0.9 during the reaction). The formed reaction products and the distilled water were collected in a tube in a cooling bath at h-60°C. The test tubes were replaced every 15 or 30 minutes and the reaction products were weighed and analyzed using a gas chromatograph and an IR spectrophotometer. The results are shown in the following table.

Example 2.

This experiment was carried out in the same apparatus and in the same way as in example 1, but the reaction solution contained only 510 g (= 3 mol) of CuCl, . 2H.,0. The pH value was 1.7 at the start. Acetylene was introduced at a rate of 20 liters per hour. The trial could only be continued up to a reduction rate of 40 per cent based on the added amount of CuCl2, as CuCl begins to precipitate at this reduction rate.

The total conversion of acetylene during the experiment was 45%, and the yield of trichlorethylene was 50% and of tetrachlorethylene 8%.

Example 3.

This experiment was carried out in a cylindrical

container with a gas distributor at the bottom through which the acetylene was supplied, and the resulting gases were led from the top of the container to a condenser where the reaction products were collected. After

a manometer and a reducing valve were connected to the condenser. 200 ml of water solution containing 3 mol of copper chloride and 6 mol of lithium chloride per litres. 7 mole percent of the total amount of copper was present as Cu (I) and the pH value of the solution was 1.8. At 120°C and an absolute pressure of 2.4 atmospheres, acetylene was introduced into the solution,

the reduction valve was regulated so that it emitted 1 liter of gas per hour from the device. After one hour, 8.5 g of product had been obtained in the condenser. The composition was 43% trichlorethylene, 2% tetrachlorethylene and 55% trans-1,2-dichloroethylene. In a similar experiment at 90°C and atmospheric pressure, a quantity of 3.3 g of product was obtained

with a composition of 59.3, 3.7 and 37.0 per cent respectively.

Example 4.

This experiment was carried out with continuous supply and removal of the reaction solution. The reaction vessel consisted of a glass tube with a length of 660 mm and a thickness of 50 mm and containing a heating coil. The acetylene was supplied through a gas distributor in the lower part of the vessel and the reaction products were allowed to distill off in the upper part of the tube. The fresh reaction solution was supplied at the bottom, and the reacted solution flowed out through an overflow in the middle of the tube. By regulating the supply rate for the solution and the amount of acetylene (5 liters per hour) it was possible to obtain 500 ml of the solution with a relatively constant degree of reduction in the vessel. The concentration of the solution was 3 mol CuCl2 per liter and 6 mol LiCl per litres. The pH value was 2.3.

The results are shown in the following table:

The conversion of acetylene during the experiment was approx. 45% and the yield of trichlorethylene 66% and of tetrachlorethylene 10%.

The conversion of acetylene during the experiment was 70% and the yield of trichlorethylene 67% and tetrachlorethylene 27%.

Example 6.

This experiment was carried out as in the example

3, but the spillway had been moved higher up like this

that the reaction vessel contained 750 ml of solution containing 6 mol of CuCl2 per litres. The pH value was 2.3.

The conversion of acetylene during the experiment was 40% and the yield of trichlorethylene 65% and of tetrachlorethylene 19%. In the reaction product formed, tri- and tetrachlorethylene are easily separated by distillation.

Example 7.

In this experiment, the volume of the reaction vessel was approx. 8 litres, and the apparatus was otherwise in principle the same as in examples 4-6. The continuously supplied water solution contained 6 mol of copper chloride per litres, 8 mole percent of the total amount of copper being present as Cu (I). The pH value of the solution was 1.8 and its temperature 100°C. Acetylene was supplied at a rate of 20 standard liters per hour and was converted to a product consisting of 81 percent (by weight) trichlorethylene, 12 percent tetrachlorethylene and 7 percent trans-dichloroethylene. The conversion of acetylene was 97 per cent.

Example 8.

The experiment was carried out continuously as in example 7, but the solution contained 4.5 mol copper chloride and 3 mol lithium chloride per litres. The amount of Cu (I) was 15 mole percent of the total amount of copper, the solution's pH value was 1.8 and its temperature 100°C. 20 standard liters per hour acetylene was practically completely converted to a product consisting of 76 per cent (by weight) trichlorethylene, 12 per cent tetrachlorethylene and 12 per cent trans-dichloroethylene, a total of 114 g per hour. The catalytic solution was then pumped to an oxidation column where it was oxidized with a mixture of approx. 60 standard liters of HCl gas and 30 standard liters of oxygen per hour.

The method can be carried out on a larger scale in an apparatus which is schematically shown in the drawing.

In principle, the apparatus consists of a reactor 1 with an inlet at the bottom for the chloride solution from a container 3a, an inlet for acetylene and an overflow for the solution. The reaction product is discharged at the top of the reactor together with unreacted gas and collected in a condenser 5. The spent solution is led to a container 6b from which it is pumped by means of a pump 4b to another container 3b. The copper (I) ions in the used solution are oxidized with HC1 and O, in an oxidation column 2 which is equipped with an inlet at the bottom for the solution from the container 3b and an overflow from which the solution flows to a container 6a, and the solution is pumped from there by means of a pump 4a to the container 3a. The oxidizing gases (HC1 and O2) are supplied to the column at the bottom and escape at the top.

Instead of using a separate oxidation column, the reoxidation can be carried out in a reactor equipped with separate inlets for acetylene and the mixture of oxygen and hydrogen chloride.

Claims (4)

1. Process for the production of trichlorethylene and tetrachlorethylene by a reaction between acetylene and copper chloride in a water solution, characterized in that acetylene is passed through a reaction solution containing copper (II) and copper (I) ions, where copper (II ) ions make up 50-100, preferably 70-100, mole percent of the total amount of copper, possibly chlorides of other metals, and have a pH value of 0 to 3, preferably 1 to "2.5, at a reaction temperature of at least 60 °C. 2. Method according to claim 1, characterized in that the total chloride ion content in the solution is from 4 gram atoms per liters up to a solution which is saturated at the reaction temperature. 3. Method according to claims 1-2, characterized in that the solution contains water-soluble chlorides of potassium, lithium, calcium, magnesium, aluminium, zinc or a mixture thereof. 4. Method according to one of the preceding claims, characterized in that the solution also contains ammonium chloride.