NL7907067A - PROCESS FOR THE CONTINUOUS PREPARATION OF OCTACHLOROCYCLOPENTES. - Google Patents

Description

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Hoeehst Aktiengesellschaft Frankfort a / d Main Federal Republic of Germany • j

Process for the continuous preparation of octachlorocyclopentene.

The present invention relates to a process for the continuous preparation of octacl-cyclopentene by a single-stage chlorination of cyclopentadiene in inert diluents at elevated pressure. The reaction proceeds according to the equation: C ^ Hg + J Clg = Ο ^ ΟΙβ + 6 HCl.

Qctachlorocyclopentene is used as an intermediate for dyes, plastics and insecticides. It is particularly suitable as a starting material for the recovery of hexachlorocyclopentadiene (U.S. Pat. No. 2,7-2,506) from which cyclodiene insecticides can be prepared.

Since the first preparation of octachlorocyclopentadiene in 1877, a series of synthesis methods have been published, of which only the chlorination of aliphatic and cyclic hydrocarbons has acquired a certain technical significance (Chenu Rev. 58, 289 (1958)).

For example, according to U.S. Pat. No. 2,71h, chlorinated C 15 coal, substances with at least 2 chlorine atoms in the molecule are converted to octachlorocyclopentene with porous surfactant catalysts containing chlorine at 280-500 ° C. Preferred starting materials are polychlorinated pentanes with more than 5 chlorine atoms, which are first photochlorinated by pentanes, e.g. according to U.S. Pat. No. 2,1 * 73,162.

A likewise two-stage process is described in U.S. Pat. No. 2,900,120, in which a product mixture designated as tetrachlorocyclopentane is first recovered by chlorination of cyclopentadiene in the liquid phase at -50 to + 80 ° C. This is then converted into octachlorocyclopentene with further chlorine at reaction temperatures increasing from 170 to 275 ° C. By adding catalysts such as arsenic III oxide, e.g. using 0.7-0.8 kg of tetrachlorocyclopentane, the reaction time can be reduced from 39 to 11 hours. To increase the chlorine concentration% 7907067 2 f in the liquid phase, pressures up to 35 tar are recommended. In this patent it is stated explicitly in colline 6, lines 30-6U, that the subdivision in the conversion of cyclopentadiene with chlorine into octachlorocyclopentene in two steps is absolutely necessary. The first stage, the chlorination of cyclopentadiene to tetrachlorocyclopentane. is highly exothermic. Therefore, in order to avoid side reactions, the temperature should be kept below 80 ° C by cooling. This is also possible without disadvantage, because the reaction proceeds very quickly even at 0 ° C. On the other hand, the reaction rate of the subsequent chlorination of tetrachlorocyclopentane to octachlorocyclopentene is also relative to the boiling temperature of the organic mixture of initially 160 ° C. minor. A combination of these steps at very different temperatures for the continuous preparation of octachlorocyclopentene is difficult and expensive.

A further two-stage synthesis process is presented in U.S. Patent No. 3T23.2T2. The first stage consists of a thermal cleavage of dicyclopentadiene to cyclopentadiene and the conversion thereof, after dilution by chlorinated cyclopentanes, with an excess of chlorine, preferably 60-120 ° C, with or without 1 UV-light to a polychlorocyclopentane. with ^ -5 chlorine atoms per molecule. In the second stage, this product is chlorinated to octachlorocyclopentene under irradiation with UV light at 160 ° C.

A process for the continuous preparation of octachloro-cyclopentene from cyclopentadiene and chlorine has now been found, comprising cyclopentadiene, an inert diluent and an at least stoichiometric amount of chlorine at 20-300 bar and temperatures of the three liquid components of at most 60 ° C and limits the maximum temperature of the subsequent exothermic reaction to 200-500 ° C.

Organic starting material for the present process is cyclopentadiene. In principle, cyclopentene and cyclopentane can also be used, but these are not available as raw materials to the same extent as cyclopentadiene and do not offer any advantages in this process compared to cyclopentadiene.

7907067 «3 3

Chlorine is used in at least stoichiometric amounts. However, in order to eliminate the risk of soot formation, one generally works with 110-800% of the stoichiometric amount of chlorine, preferably with 110-200% and in particular with 110-200%.

The cyclopentadiene is reacted in the presence of one or more diluents with chlorine to avoid the formation of carbonization products and the strongly exothermic reaction. Preferably, the diluent should not react with cyclopentadiene, because otherwise the yields of octachlorocyclopentene will decrease on the one hand and disturbing by-products will be formed on the other hand. In addition, the diluent should preferably also be inert to chlorine, so as not to further increase the total exempted enthalpy of reaction and chlorine consumption. These requirements meet h.v. perchlorinated hydrocarbons such as tetrachloromethane and octachlorocyclopentene.

The latter can be used in pure form, but also, particularly economically, in the form of a crude product substantially free of chlorine, of the present process. The weight ratio of diluent to cyclopentadiene is usually 6θ: 4θ to 99: 1, preferably 70:30 to 99: 1, most preferably 80:20 to 99: 1 * 20 Cyclopentadiene and the diluent are mixed individually or already at 20-300 bar with at least a stoichiometric amount of chlorine, all three components being liquid and their temperatures between their melting points and + 60 ° C. Preferably, cyclopentadiene with melting point 25 -9 ° C and chlorine with melting point -101 ° C is used at temperatures between -50 and + 30 ° C, most preferably between -30 and + 10 ° C. These two components spontaneously react with each other when combined, while heating the reaction mixture at high temperatures. However, since chlorolysis of the C1-ring to tetrachloromethane, hexa-chloroethane and hexachloro-hutadiene is progressively increasing above 500 ° C, the reaction temperature must not exceed this value anywhere in the reactor. On the other hand, the interior temperature of the reactor should not be below 200 ° C everywhere. The adjustment of the maximum reactor interior temperature between 200 and 500 ° C is preferably effected by using an appropriate excess of chlorine, which is then used as a coolant 790 7 0 67 1+ ΐ. Naturally, under otherwise equal conditions for setting, a maximum temperature of 200 ° C requires a larger excess of chlorine than for setting the temperature of 500 ° C. The total amount of chlorine for the reaction and cooling is a maximum of 5 800/5 of the stoichiometric amount. Almost this adiabatic mode of operation, however, there is also the possibility, the excess reaction enthalpy via a. heats the exchanger to an external cooling medium.

In the present process, catalysts are unnecessary, as are energy-rich radiation, such as UV light. As a result, no problems arise through separation and regeneration of the catalytic substances or. by a soot separation. the windows of the light sources.

The conversion is carried out at 20-300 bar, the range between 50 and 250 bar being preferred.

The present process proceeds despite dilution of the cyclopentadiene with space-time yields up to 30 kg of octachlorocyclopentene per liter of reaction space and per hour. As a result, the reactor for this continuous process can be made very small.

The selectivity to octachlorocyclopentene is usually considerably above 90%. Small by-products of tetrachloromethane, hexachloroethane, hexachlorobutadiene and hexachlorobenzene are formed as by-products, but no chlorinated cyclopentadiene oligomers, which according to the literature (J.Appl.Chem. (USSR) Uo, 1536 (1967)) in fairly large quantities when chlorinated of cyclopentadiene 25, in the liquid phase above 50 ° C should be expected.

As a difference with. The above multistage chlorinations in the present process result in all hydrogen chloride from the reaction of cyclopentadiene with. single stage chlorine under elevated pressure. At elevated pressure, hydrogen chloride can more easily be separated than chlorine and octachlorocyclopentene at atmospheric pressure and isolated in a pure dry form so that it can be used directly in hydrochlorination, oxychlorination, or HCl electrolysis processes. Likewise, the excess chlorine can be recovered under pressure in an easy to liquefy form and re-used for chlorination of cyclopentadiene without further ado. The work-up is preferred for the reaction mixture at elevated pressure, but it is also feasible at normal pressure.

The present process is thus excellently suited for the continuous preparation of octachlorocyclopentene from cyclopentadiene 5 and chlorine. Particularly favorable for commercial application are the fact that work is done in a staircase, the very height-space-time yields and the relatively simple separation of the pressurized products.

A high-pressure tube with a nickel-coating has proved advantageous as the construction of the reactor, the inlet of which is provided with a two-jet nozzle for intensive mixing of the reaction partners. However, the reactor and the mixer can also be reshaped.

The following examples further illustrate the invention.

15 Examples

The chlorination of cyclopentadiene was carried out in a vertical high pressure tube of heat resistant stainless steel. equipped with a nickel coating, executed. This tube had a length of 2200 mm, an outer diameter of U8 mm, an inner diameter of 25 mm and was closed with nickel lenses at the ends. This reactor was brought to an internal temperature of 200 ° C with four jacket heatings before the start of the reaction. Thereafter, the dilute cyclopentadiene and the chlorine were introduced in the liquid form with membrane pumping at the temperatures shown in the table through a two-jet nozzle at the bottom of the reactor. The maximum internal temperature of the reactor was determined by sliding a thermocouple in a stainless steel tube coated with nickel tube (outer diameter 10 mm), which protruded into the reactor from above over a length of 2100 mm. The said temperature was adjusted by varying the amount of chlorine.

The jacket heaters were switched off after reaching the desired maximum reactor interior temperature of 30 ha. The products were relaxed at atmospheric pressure in a high pressure valve at the top of the reactor, to determine the selectivity and the space-time yields of octachlorocyclopentene, with the exception of a recovery of hydrogen chloride and chlorine. To this end, the product mixture was 7907067 - / 6. passed through a separator cooled with butanol dry ice, from which essentially only hydrogen chloride and part of the chlorine escaped uncondensed. The condensate was freed from chlorine by distillation and was finally analyzed. The calculation of the space-time yields was calculated with a free reactor volume of 0.9 liters. Soot formation was not observed.

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7907067

Claims (3)

Process for the continuous preparation of octachlorocyclopentene from cyclopentadiene and chlorine, characterized in that cyclopentadiene, an inert diluent and an at least stoichiometric amount of chlorine at 20-300% and temperatures of the three liquid components of at most 60 ° C and limits the maximum temperature of the subsequent exothermic reaction to 200-500 ° C. 2. Process according to claim 1, characterized in that the maximum reaction temperature is measured with. chlorine using an appropriately selected excess. Process according to claims 1 or 2, characterized in that the diluent used is tetrachloromethane or octachlorocyclopentene. i m 790 70 67