DE2261515C3 - Process for the production of 1.2.3-trichloropropene - Google Patents

Description

30th

1,2,3-Trichloropropene is used as an intermediate in the manufacture of certain pesticides and other chemical products use.

So far, 1,2,3-trichloropropene has been produced on an industrial scale by initially adding 2,3-dichloropropene converted into 1,2,2,3-tetrachloropropene via a liquid phase chlorine addition reaction and then the desired 1,2,3-trichloropropene was obtained by elimination of hydrogen chloride.

The implementation of this batch process, which requires two conversions, is complex and relatively expensive.

There is therefore a great need for a process that is simple and economical Obtaining 1,2,3-trichloropropene permitted.

The invention thus provides a process for the production of 1,2,3-trichloropropene, which thereby is characterized in that a mixture of 2-chloropropene and 2,3-dichloropropene in the weight ratio from about 0.2: 1 to 0.6: 1 in the gas phase at 460 to 500 ° C and a residence time of about 0.2 to 0.4 Reacts with chlorine for seconds, the weight ratio of chlorine to the chloropropene mixture being about 0.1: 1 up to 0.3: 1, the resulting chloropropene mixture is fractionated, the 1,2,3-trichloropropene is separated off and the return unreacted 2-chloropropene and 2,3-dichloropropene to the reaction.

In a preferred embodiment of the process according to the invention, a mixture is exposed 2-chloropropene and 2,3-dichloropropene in a weight ratio of about 0.4: 1 to 0.5: 1. Preferred a weight ratio of chlorine to chloropropene mixture of about 0.2: 1 to 0.25: 1 is used.

According to a further preferred embodiment of the process according to the invention, this is used Reaction mixture at 480 to 490 ° C and a residence time of about 0.25 to 0.35 seconds with chlorine urn.

The exact optimal weight ratio of that consisting of 2-chloropropene and 2,3-dichloropropene Mixture naturally depends, within the ranges given above, on the reaction conditions used.

That is, considering the weight ratio the amount of 2,3-dichloropropene, which from the existing 2-chloropropene under the intended Reaction conditions is formed, is selected. For the method according to the invention it is essential that the 2,3-dichloropropene component of the mixture in a quantitative equilibrium state without increase or Deficit is accepted. To achieve this, the amount of 2,3-dichloropropene should be in the effluent from the reactor must be exactly as much larger than in the inlet stream that those caused by distillation and circulation Losses are offset. In general, an excess of 2 to 3% is sufficient to compensate for this Losses.

It is generally dependent on availability advantageous to use 2-chloropropene as the sole raw material for the process. In this case it will 2-chloropropene first passed through the process stages and the 2,3-dichloropropene formed together with the unreacted 2-chloropropene is then fed back in a circuit to a mixing zone to after Need to be mixed with more 2-chloropropene.

As the liquid mixture is formed, it is fed to an evaporator for conversion into the vapor phase. The vapors of the chloropropene mixtures are then fed to a preheater before being mixed with gaseous chlorine. Since chlorine is usually added rapidly by the olefin compounds when they are brought into contact at relatively low temperatures, it is necessary, if an addition reaction is to be essentially avoided, to bring the reactants together at an elevated temperature. The preheating temperatures are not critical; however, it is necessary that they be sufficiently high to prevent addition reactions from occurring. It has been found that temperatures of about 280 to 400 ° C. are generally sufficient.

After passing through the preheater, the hot chloropropene vapors are mixed with chlorine in the way mixed that the weight ratio of chlorine to chloropropene mixture in the range of about 0.1: 1 to 0.3: 1 and preferably from 0.2: 1 to 0.25: 1. The conditions described above are critical insofar as as a relatively low concentration of chlorine results in decreased conversion, while a higher concentration leads to excessive degradation of the desired product.

After the chloropropene gases have been mixed with the chlorine, it is particularly desirable that the reaction mixture be allowed to reach reaction temperatures as soon as possible in order to keep the formation of by-products as low as possible. The gaseous mixture thus is introduced immediately into a reactor which is maintained at a temperature of 460-500 ⁰ C, preferably 480-490 ⁰ C. It was found that ^{chlorine addition reactions are suppressed at reaction temperatures above about 460 °} C. in favor of chlorine substitution. However, it is desirable not to let the temperatures rise above 500 ° C., because decomposition reactions and carbonization of chloropropene then occur.

The halogen substitution reaction is exothermic and considerable heat is liberated in the process. This increases the temperature of the reaction mixture from that required during preheating brought the desired height in the reactor. To keep the reactor temperature at the desired level automatic control devices are of course required.

The residence time at reaction conditions should be in the range of about 0.2 to 0.4 seconds, with about 0.25 to 0.35 seconds are usually preferred. Residence times in the reactor of less than about 0.2 seconds provide one excessive chlorine flow, during time intervals longer than about 0.4 seconds to excessive coke formation, Clogging of the reactor and / or formation of fire.

It is advantageous to remove the entire effluent from the reactor, with the exception of the hydrogen chloride formed and unreacted chlorine - if present - to condense by the fact that the effluent is a Feeds cooler below the boiling point of the lowest boiling chloropropene reactant is cooled. The hydrogen chloride formed in the reaction and the unreacted chlorine are passed through run the cooler and feed it to a washer for further use.

The condensate from the condenser is subjected to a fractional distillation to remove the 1,2,3-trichloropropene of unreacted 2-chloropropene, the 2,3-dichloropropene formed during the reaction and various to separate off reaction by-products formed in small amounts. 1,2,3-trichloropropene is collected as the product and 2-chloropropene and 2,3-dichloropropene become the initial stage of the process fed back

A significant advantage of the method according to the invention is that it is possible to use pipe materials directly into the desired 1,2,3-chloropropene can convert a reaction that lends itself well to a continuous operation. In addition, the Formation of undesired by-products to less than about 10%, based on the total product, restricted.

example

A liquid mixture was prepared by mixing 2-chloropropene (83.9 kg, 91.5 liters) with 2,3-dichloropropene (192 kg, 160.2 liters) to form a mixture of 2-chloropropene and 2,3- Dichloropropene in a weight ratio of 0.44 ·. 1 mixed. The liquid mixture was evaporated and passed through a Vorerhitzungsröhre, in which the temperature of the mixture was brought to about 35O ⁰ C. The hot vapors from the preheater were then intimately mixed with chlorine (67.5 kg) to form a reactive mixture having a weight ratio of 0.245: 1 (chlorine to chloropropene mixture). This chlorine-containing mixture was immediately fed to an isolated reactor which was kept at 480 ^° C., the residence time being 0.3 seconds.

The reactor, which contained a temperature control device set at 480 ° C., was spherical in shape with an exit to a cooler in the bottom hemisphere and a feed injection protrusion approximately in the center of the sphere. A thermocouple was installed in the output and was used to regulate the temperature of the preheater to about 35O ⁰ C. The exothermic reaction caused a temperature rise in the reactor up to 480 ° C at a feed temperature of about 35O ⁰ C.

After the reaction, the effluent from the reactor was passed to a condenser and the hydrogen chloride formed and let the unreacted chlorine run through a scrubber. The condensate (307.5 kg) had the following composition:

Compound weight%

2,3-dichloropropene

2-chloropropene

ice-1,2,3-trichloropropene

trans-1,2,3-trichloropropene

By-product mixture

62.5

13.3

8.3

6.7

9.2

After distilling the condensate under atmospheric conditions through a 20-plate column 45.8 kg of 1,2,3-trichloropropene were in the fraction at a steam temperature between 130 and 150 ° C collected. At steam temperatures of up to 125 ° C, a low-boiling fraction (235 kg) was the following composition collected.

connection

Wt%

2-chloropropene

1,2-dichloropropene

2,3-dichloropropene

1,2,2-trichloropropene

2,3,3-trichloropropene

17.1
1.1

80.4
0.8
0.6

This low boiling distillate was with 42.1 kg of 2-chloropropene to form a mixture of 2-chloropropene and 2,3-dichloropropene mixed in a weight ratio of 0.44: 1 and the process cycle fed back.

Claims (4)

Patent claims: I. A process for the preparation of 1,2,3-trichloropropene, characterized in that a mixture of 2-chloropropene and 2,3-dichloropropene in a weight ratio of about 0.2: 1 to 0.6: 1 in the gas phase 460 to 500 ⁰ C and a residence time of about 0.2 to 0.4 seconds with chlorine, the weight ratio of chlorine to the chloropropene mixture is about 0.1: 1 to 0.3: 1, the resulting chloropropene mixture is fractionated, the 1st , Separates 2,3-trichloropropene and returns the unreacted 2-chloropropene and 2,3-dichloropropene to the reaction. 2. The method according to claim I, characterized in that there is a mixture of 2-chloropropene and 2,3-dichloropropene in a weight ratio of about 0.4: 1 to 0.5:! begins. 3. The method according to claim I and 2, characterized in that there is a weight ratio used from chlorine to chloropropene mixture of about 0.2: 1 to 0.25: 1. 4. The method according to claim 1 to 3, characterized in that the reaction mixture is reacted ^{with chlorine at 480 to 490 0} C and a residence time of about 0.25 to 0.35 seconds.