DE1793065A1 - Process for the preparation of 1,2-dichloroalkanes - Google Patents

Description

Process for the preparation of 1,2-dichloroalkanes The preparation of 1,2-Dicüloralkanen by addition of chlorine to olefins is generally known. Here, gaseous olefin and gaseous or liquid chlorine are separated into introduced a liquid reaction medium, which preferably consists of the reaction product itself (1,2-dichloroalkane) or from inert solvents resistant to chlorine consists.

The heat of reaction released during the chlorination is either acted upon by aie reaction liquid by means of circulation via rr.-t cooling water Heat exchanger odei removed by evaporation of the dichloroalkane produced, wherein in the last-mentioned procedure, the 1,2-dienloroalkane obtained at the same time purified by distillation wirQ.

In previous processes, the chlorides of iron, aluminum, Antimony, chromium, copper and titanium (Canadian patent 689 991 and German Patent 640 827) proved to be useful chlorination catalysts.

Oxygen is added to the olefin to prevent undesired substitution reactions low (U.S. Patent 2,601,322).

For some of the catalysts mentioned, e.g. iron and aluminum chloride, is a decomposition of the dichloroalkane produced with the separation of tarry, carbon-rich ones Deposits are possible, especially when using elevated temperatures.

Another method is the reaction between olefin and Chlorine in the presence of aliphatic carboxamides (US Pat. No. 3,338,982) carried out. By the carboxamides the reaction between olefin and chlorine. selectively catalyzed and no carbon-rich deposits are formed. The disadvantage of these Oiganischen catalysts lies in their only relative poor stability and their sensitivity to hydrolysis, so that undesirable, low-boiling by-products arise.

The invention relates to a process for the preparation of 1,2-dichloroicans due to the addition of chlorine to olefins with 2 to 4 carbon atoms in the liquid phase. The process is characterized in that the chlorination is carried out in liquid, 1,2-dichloroalkane and in the presence of hexamethylphosphoric triamide and / or N-methylpyrrolidone Carries out as a catalyst, the catalyst solution optionally with the addition of olefin and chlorine is circulated.

By using the catalysts in an amount of 0.05 to 0.2% by weight, based on the 1,2-dichloroalkane used, succeeds at temperatures from OOC to 800C the addition of chlorine to olefins with 2 to 4 carbon atoms to be carried out in a targeted manner, so that the formation of by-products is largely avoided although hexamethylphosphoric triamide or

Capable of forming complexes with 1,2-dichloroalkanes (German patent specification 1 121 247).

The catalysts of the invention inhibit the formation of 1,1,2-trichloroethane in reinforced maggot and suppress the ethyl chloride formation Completely. This results in significantly higher yields of 1,2-dichloroalkanes.

In addition, the claimed catalysts are compared to the aliphatic Carboxamides far less sensitive to hydrolysis and more stable, which means that the low-boiling decomposition products that occur when carboxamides are used do not arise and thus a greater purity of the reaction product is achieved.

Furthermore, the new catalysts are easy to handle and good to dose. They bring no storage problems as well as no difficulties the separation.

The catalyst can be introduced directly into the reaction liquid or supplied with the olefin gas according to the tension.

To increase the catalytic effect, the catalyst can also used together with trace oxygen.

It has been found to be useful if the reaction takes place at a pressure from 0.5 to 6 ata is carried out absolutely.

The 1,2-dichloroalkane produced by the process according to the invention is not colored dark. Furthermore, there are no carbon-rich deposits to be observed, e.g. when using of ferric chloride. In contrast for the latter, the catalysts according to the invention do not cause any decomposition of 1,2-dichloroalkane in the heat. On the other hand, because of their high level, they remain Boiling point when the 1,2-dichloroalkane produced is distilled off directly in the reaction vessel. Since they also the reaction between olefin and chlorine even at higher temperatures catalyze selectively, it succeeds by utilizing the heat of reaction that is generated 1,2-dichloroalkane to be distilled off in a column immediately after the reaction, an additional purification of the reaction product is achieved. It remains the activity of the catalyst is fully preserved and there is no gumming 1,2-dichloroalkane.

The catalyst solution obtained in the distillation can be used successfully be circulated with the addition of olefin and chlorine. The relation between Olefin and chlorine can be adjusted to be stoichiometric, but it is preferred with a small olefin excess compared to chlorine of 1.05: 1 to 1.1: 1 worked.

Another advantageous property of the catalysts according to the invention consists in the fact that it is formed from the apparatus as a result of the action of chlorine Ability to bind iron chloride in a complex manner. When using the claimed catalysts it is therefore possible to carry out the chlorination of olefins in an iron reactor.

Example 1 It was in a glass bottle with about 5 ltr. Volume worked.

This glass reactor was fitted with a stirrer, thermometer and provided with a cooling jacket. After filling the reactor vessel with 1 ltr. 1,2-dichloroethane 50 l / h of ethylene and chlorine were fed into separate gas inlet nozzles with vigorous stirring introduced into the reaction medium via glass frits attached to the bottom of the glass bottle. Ethylene was present in a slight excess over chlorine. The temperature was kept at 300C by circulating cooling water through the cooling jacket. The analytical investigation of the reaction product was carried out on gas chromatography Ways. The yields were determined on the basis of the HCl and chlorine content in the reactor off-gas.

The chlorination of ethylene was carried out in the presence of 0.1% by weight of hexamethylphosphoric triamide (Experiment 1), 0.1 wt.% N-methylpyrrolidone (Experiment 2) and a mixture of 0.05 Weight

Hexamethylphosphoric acid triamide and 0.0% by weight of N-methylpyrrolidone (experiment 3), based in each case on 1,2-dichloroethane.

Furthermore, further experiments 4 and 5 were carried out with the above-mentioned catalysts driven in the presence of a trace of oxygen. The duration of the experiment was b in each case Hours.

The results of these tests are recorded in Table 1.

Table 1 Experiment no. Catalyst catalyst conc. Yield% by weight % By weight 1 hexamethylphosphoric acid 0.1 99.9 triamide 2 N-methylpyrrolidone 0.1 99.9 3 hexamethylphosphoric acid- 0.05 100 triamide + N-methylpyrrolidone +0.05 4 hexamethylphosphoric acid- 0.1 100 triamide and oxygen 5 N-methylpryrrolidone and 0.1 100 oxygen Comparative example In the same apparatus and under the same conditions as in Example 1 was if ferric chloride is used as a catalyst, also in a glass bottle approx. 5 ltr. Volume worked. When using 0.1% by weight of iron (III) chloride as Catalyst, based on 1,2-dichloroethane, was after 4 hours of reaction time in 99.0% yield obtained a dark-colored dichloroethane, which in addition to 0.11 % By weight of ethyl chloride contained 0.15% by weight of 1,1,2-trichloroethane as by-products.

Table 2 shows the purity of the 1,2-dichloroethane produced with ferric chloride compared with the 1,2-dichloroethane prepared according to Example 1. The concentration information are given on a ppm scale.

Table 2 Test number catalyst ethyl chloride 1,1,2-trichlorine. Table 1 ethane 4 hexamethylphosphorus 0 zC10 acid triamide 5 N-methylpyrrolidone 0 <10 comparison iron-III-chloride 1100 1500 example The values Table 2 show that the catalysts of the invention (Experiments 4 and 5) selectively catalyze the addition of chlorine to ethylene. By using this Catalysts produce a much purer 1,2-dichloroethane than when using Ferric chloride.

In game 2 the apparatus consisted of the same reactor that was in the Example 1 has been described, with the exception that the reaction vessel is made of Iron and was connected to a distillation apparatus. In the latter was the 1,2-dichloroethane produced is continuously distilled off from the catalyst and the incident Catalyst concentrate returned to the reaction.

By opening a tap in the connection line between the drain of the reactor and the distillation still was catalyst-containing 1,2-dichloroethane due to the natural gradient in the still. As both the reactor as well as the distillation apparatus under the same vacuum of 500 Torr were standing, the still pot was placed on one opposite by a heating mantle the reactor by 41OC higher temperature, so brought to {1 ° C, the 1,2-dichloroethane to bring to the boil in the bubble. Through an overflow with afterwards With a cooled siphon, the level of the filling level in the bladder was kept constant.

When using 0> 1% by weight of N-methylpyrrolidone, based on the amount used 1,2-dichloroethane, after 40 hours of operation neither soot was deposited nor To observe decomposition phenomena. The distillate consisted of 99.99% 1,2-dichloroethane, contaminated with traces of 1,1,2-trichloroethane. Xthyl chloride was not formed.

In contrast, when ferric chloride was used, there were signs of decomposition to be observed with the deposition of carbon-rich deposits, about 0.2% 1,1,2-trichloroethane and 0.11% by weight of ethyl chloride. similarly good results were also in the chlorination of propylene to 1,2-dichloropropane and of butylene to 1,2-dichlorobutane in the presence of 0.1% hexamethylphosphoric triamide, based on the amount used 1,2-dichloropropane or 1,2-dichlorobutane obtained.

Claims (4)

P a t e n t a n s ~ s r u c h e 1. Verrahren for the production of 1, 2-dichloialkanes due to the addition of chlorine to olefins with 2 to 4 carbon atoms in the liquid phase, d u r c h e k e n n -z e i c h n e t that one is the chlorination in liquid 1,2-dichloroalkane in the presence of hexamethylphosphoric triamide unaXoder Carries out N-methylpyrrolidone as a catalyst, optionally the catalyst solution is circulated with the addition of olefin and chlorine. 2. The method according to claim 1, d a d u r c h g e k e n n -z e i c h n e t that the catalyst in an amount of 0.05 to 0.2 wt.%, Based on the dichloroalkane used, is used. 3. The method according to claim 1 and 2 d a d u r c h g e -k e n n e i c h n e t that the reaction at temperatures from 0 ° C to 80 ° C of the dichloroalkane is carried out. 4. The method according to claim 1 to 5, d a d u @ c h g e -k e n n z e i c h n e t that the reaction is carried out at a pressure of 0.5 to δ ata absolute will.