DE1142357B - Process for the preparation of 2, 3-dihalopropene (1) - Google Patents

Description

Process for the preparation of 2,3-dihalopropene- (l) The invention refers to the halogenation of propadiene-allene (CH2 = C = Chia) in the gas phase at elevated temperatures. In the following, under the expression * halogenation4 Understood chlorination and bromination.

It has been found that with such a halogenation of propadiene Form 2, 3-dihalopropene (l), where after the above "halogen" "chlorine" or "Brom-" means.

It was also found that in the chlorination of propadiene 2, 3-dichloropropene- (1) (CH2 = CCI-CHZCI) is formed as the main product, namely, calculated on the chlorine consumed, under optimal conditions the yield approx 80 ° / 0, the reaction mixture of about 85 ° / 0 2, 3-dichloropropene (1) besides smaller amounts of propargyl chloride (CH2CI-C ~ --- CH), monochloropropadiene (CHCI = C = CH2) and compounds with a higher boiling point (mainly 1, 2, 3-trichloropropene (2) or CH2CI-CCI = CHCI).

Experiments were carried out with nitrogen as the diluent; 15 parts by volume of nitrogen with 1 or 2 parts by volume of chlorine gas were added to one Heated temperature as required for the reaction with propadiene, and then then passed through a vertical tube, in the lower end of which 2 parts by volume Propadiene gas were blown.

The time required for the mixture to react became through Regulation of the flow rate of the gases and according to the dimensions of the Reaction zone set. The gas mixture obtained was then passed through washing towers with soda lime filling led to the excess chlorine and hydrogen chloride formed to be deposited. As a result, a further reaction of the chlorine with 2,3-dichloropropene (l) and thus the formation of 1, 2, 2, 3-tetrachloropropane (CH2Cl-CCl2-CH2Cl).

The washed mixture was cooled to -80 ° C to remove the chlorinated Products and that not implemented Separate propadiene from nitrogen. By increasing At this temperature, the propadiene was finally evaporated from the liquefied mixture and the liquefied residual products by fractional distillation separated.

The chlorinated products were analyzed and in the infrared spectrum and identified by determining the chlorine content.

The unreacted propadiene can be returned to the cycle will. The results of the various experiments are in the table below summarized.

Table 1 Conversion rate, distribution of the reaction products Test volume ratio temperature contact time calculated in the resulting mixture in ° / No. on Cl2 on C3H4 I II III IV V N2: C3H4: Cl2 ° C seconds%% I. R 54 15: 2: 1 360 0, 2 34 13 8 0 57 35 0 R 44 15: 2: 1 420 0.5 67 31 5 2 83 0 10 R 39 15: 2: 1 538 0, 2 65 30 10 4 76 0 10 R 42 15: 2: 1 590 0, 2 67 30 13 6 66 0 15 R 46 IS: 2: 1 420 1, 0 80 37 3 1 | 87 0 9 Table 1 (continued) Conversion rate, distribution of the reaction products Experiment volume ratio temperature contact time calculated in the resulting mixture in No. on cl2 on C3H4 I II III IV V N2: C3H4: Cl2 ° C seconds%% ... R 55 15: 2: 1 420 2.0 84 40 5 1 85 0 8 R 59 15: 2: 1 420 4, 4 78 37 4 1 88 0 7 R 48 15: 2: 2 420 I 69 583 2 72 0 23 R 49 15: 1: 1 420 1 76 66 4 1 76 0 19 I = propargyl chloride. III = 2,3-dichloropropene- (l) V = 1, 2, 3-trichloropropene- (2) -unknown compounds and with II = monochloropropadiene. IV = 1, 2, 2, 3-tetrachloropropane. the experiments at 420 ° C a little 1, 2, 2, 3-tetrachloropropane.

The influence of temperature can be seen from experiments no. R 54, R 39 and R 42. At 700 ° C a considerable amount of soot is noticeable.

The experiments No. R 44, R 46, R 55 and R 59 show the influence of Contact time, d. H. the time during which the starting mixture at the specified Temperature is maintained. At about a second and more, the results are in essentially the same as when the contact time is longer than 5 seconds.

Experiment No. R 48 shows the influence of lowering the Solution with nitrogen. In the distribution of the reaction products is not essential Change can be observed, but there is a slight formation of non-gaseous Products in the reaction zone. A comparison of experiment R 49 with experiment R. 46 shows that by changing the ratio of chlorine to propadiene of 1: 2 to 1: I the formation of products with a higher boiling point increases.

Very good results are obtained when the temperature is between about 360 and 600 ° C and the contact time is between 0.5 and about 0.2 seconds emotional.

The ratio of nitrogen to propadiene can be in a wide range vary.

A typical example of a good yield of 2,3-dichloropropene (I) with little formation of by-products and a good amount of remodeling (Speed) is shown according to example R 46.

It has also been found that when propadiene is brominated 2, 3-dibromopropene- (l) (CHQ = CBr-CH2Br) is formed as the main product; under under certain conditions, the implementation amount 80 ° lo, calculated on the consumed Bromine, the reaction mixture consisting of approximately 98% of 2,3-dibromopropene- (1). Experiments were carried out using nitrogen as a diluent.

A mixture of 15 parts by volume of nitrogen with 1 part by volume Bromine gas and, on the other hand, 30 parts by volume of nitrogen with 2 parts by volume of bromine gas separately heated to a temperature required for reaction with propadiene, and then passed through a vertical pipe, in the lower end of which 2 parts by volume of propadiene gas blows in. The time required for the mixture to react is determined by the regulation the flow rate of the gases in relation to the dimensions of the reaction zone certainly. The gas mixture formed is passed through washing towers with soda lime are filled, whereby the excess of bromine and hydrogen bromide formed is removed will. This prevents any further reaction of bromine with 2,3-dibromopropene- (1) and thus the formation of 1, 2, 2, 3-tetrabromopropane (CH2Br-C (Br) 2-CH2Br).

The washed mixture is cooled to at least -80 ° C to the to deposit brominated products; the unreacted propadiene is liquefied by the Mixture is evaporated and the remaining liquefied brominated products become separated by fractional distillation.

The brominated products are analyzed and identified by infrared spectrum theory by determining the bromine content. Unreacted propadiene can be recycled. The results are shown in the table below: Table II Conversion rate, distribution of products in the received Test volume ratio temperature contact time calculated mixture in% No. on Br2 on C3H4 I II III IV V VI N2: C3H4: Br2 ° C seconds%% S 1 15: 2.1: 1.2 420 1 69.4 40.4 0 0 0 93.9 0 6 1 S 3 15: 2, 1: 1.3 420 4.26 75.2 49.4 2.3 3.0 0.4 80.6 1, 6 12, 1 S 6 15: 2.2: 1.4 520 9.32 67.5 47 7.6 5.2 0 73.2 0 14.0 S 8 15: 2.1: 1.3 220 1.07 83.1 48.1 0 0 0 68.1 17.5 14.3 S 9 15: 2.1: 1.3 320 0.38 81.2 49.8 0 0 0 83.9 3.9 12.1 S 10 15: 2.1: 1.3 320 0.096 90.8 40.7 0 0 0 34.3 56.1 9.6 S 12 15: 2.1: 1.3 420 0.042 81.9 53.7 0 0 0 25.1 25.1 15.5 S 13 15: 2.1: 1.3 320 4.3 80 54.8 0 0 0 97.7 0.5 1.8 S 16 30: 2.1: 2.1 320 1.1 79.1 75.1 0 0 0 75.8 15.1 8.9 S 17 30: 2.1: 2.2 320 4.5 84.0 60.5 0 0 0 50.8 10.4 38.9 S19 15: 2, 0: 1, 3 220 6, 4 83, 8 56, 4 0 0 0 86, 5 2, 8 10, 7 I = propargyl bromide. III = 2-bromopropene. V = tetrabromopropane.

II = monobromium propadiene. IV-2,3-dibromopropene- (I). VI = substances unknown composition.

It is possible to start the reaction of propadiene and bromine in the gas phase to be carried out at temperatures of around 550 ° C in connection with the contact time, that practically only 2,3-dibromopropene (l) is formed.

The distribution and amount of the various compounds in the resulting If the other conditions are the same, the reaction mixture depends on the contact time from, d. H. the time during which the respondents at the specific Temperature are maintained.

At 420 ° C and a contact time of 0.04 seconds you get a substantial amount of 1, 2, 2, 3-tetrabromopropane; with a contact time of 1 second 2,3-Dibromopropene- (I) is practically the only product and for an even longer one Contact time one finds small amounts of monobromine compounds.

At 320 ° C and a short contact time (0.1 seconds) forms a substantial amount of tetrabromopropane, but this changes in favor of Formation of 2,3-dibromopropene- (l) when the contact time is increased; at 4.3 seconds practically only 2,3-dibromopropene (I) are found. At 320 ° C there are no monobromine compounds found.

On the other hand, one observes one at 520 ° C (Experiment 36) increased formation of monobromine compounds.

It is also possible at a much lower temperature to work ; at 220 ° C and 6.4 seconds of contact time are mainly found 2,3-dibromopropene- (l).

A comparison of the experiments No. S 16 and S 17 with other experiments at 320 ° C shows the influence of changing the ratio of bromine to propadiene from about 1: 2 to about 1: 1. With a slightly longer contact time (4.5 seconds) there is a loss of some 2,3-dibromopropene- (I) through the formation of unknown compounds on ; a shortening of the contact time leads to the formation of a substantial amount of tetrabromopropane.

In general, the formation of tetrabromopropane is favored by short contact times. An increase in temperature leads to a decrease in formation of tetrabromopropane.

Monobromium compounds are used with longer contact times and higher Temperatures found.

Typical examples of a good yield of 2,3-dibromopropene (I) with little byproduct formation and a good amount of conversion show the experiments No. S 1, S 13, S 19 and S 16.

It should be noted that in the bromination of propadiene in the case A substantial amount of tetrabromopropane is formed in a very short contact time. stands, whereas in the chlorination of propadiene with a very short contact time one significantly lower formation of tetrachloropropane can be observed.

It is convenient to use an inert diluent gas such as nitrogen use, because in undiluted systems the reaction to uncontrollability tends.

The examples were carried out on a laboratory scale, in which If it is expedient to use the largest possible ratio of solvent gas to reactants applies. In a process on an industrial scale, on the other hand, there are better means to regulate the contact time and other conditions available so that when Working on a large scale the ratio of diluent gas to reactants can be modified, especially more in favor of the reactants.

The 2,3-dihalopropene (l) are advantageous intermediates for chemical syntheses and otherwise effective as such against certain organic ones Pests, e.g. B. against nematodes.

Claims (8)

PATENT CLAIMS: 1. Process for the production of 2,3-dihalopropene (I), characterized in that one propadiene with a halogen from the group Reacts chlorine and bromine in the gas phase at elevated temperatures and the resulting 2,3-dihalopropene (l) isolated. 2. The method according to claim 1, characterized in that one propadiene and chlorine is converted to 2,3-dichloropropene (I) at elevated temperatures. 3. The method according to claim 2, characterized in that reaction temperatures between 360 and 600 ° C can be used. 4. The method according to claim 3, characterized in that the Mixture of propadiene and chlorine allowed to react for 0.5 to 2.0 seconds. 5. The method according to claim 1, characterized in that one propadiene and converts bromine at elevated temperatures to 2,3-dibromopropene- (I). 6. The method according to claim 5, characterized in that reaction temperatures between 200 and 550 ° C can be used. 7. The method according to claim 6, characterized in that the Mixture of propadiene and bromine allowed to react for 0.1 to 10 seconds. 8. The method according to claim 1, characterized in that the halogenation is carried out in the presence of an inert diluent gas.