DD235631A1 - PROCESS FOR THE PREPARATION OF CHLOROPROPENES FROM 1,2-DICHLORPROPANE - Google Patents

Abstract

The invention relates to a process for the preparation of chloropropenes by elimination of hydrogen chloride from 1,2-dichloropropane under simple apparatus conditions and with a high degree of conversion. The process is characterized in that 1,2-dichloropropane is passed in gaseous form in the temperature range from 373 to 573 K, preferably from 423 to 483 K, over a catalyst. The catalyst used is an iron oxide / activated carbon combination.

Description

Title of the invention

Process for the preparation of chloropropenes from 1,2-dichloropropane

Field of application of the invention

The invention relates to a process for the preparation of chloropropenes, which are obtained by elimination of hydrogen chloride in the presence of a catalyst of 1,2-dichloropropane.

Characteristic of the known technical solutions

It is already known that a dehalogenation of 1,2-dichloropropane to Chlorpropen ^ can be targeted by means of catalysts. The metals copper, gold, silver, iron, nickel, cobalt, which have been applied to a silica gel, split off hydrogen chloride from the corresponding chlorinated propanes, for example 1, 2-dichloropropane, and the chloropropene is produced in high yields (US Pat. PS 2,115,640). The disadvantage of this method is that after a short period of the metal catalyst, a significant drop in selectivity is recorded and a reduction in sales is measured, since the catalyst is poisoned by the split chlorine.

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In DE-PS 1,029,368 a process for the preparation of Ch orprop en en (ice-1-Chlorprop en, trans-1-Chlorprop s and 2-chloropropene) by elimination of hydrogen chloride from dichloropropane duc.cn the action of alkalis such as Sodium hydroxide or potassium hydroxide in organic solvents, such as. As methanol, ethanol or butanol * described.

In DE-OS 2,633,459 Chlorpropene is closed before a gen 'to produce by the reaction of 1,2-dichloroprop with Na triumbuty at I and butanol as the solvent. However, both methods involve the disadvantage that the organic solvent is not reusable after the reaction, but must be worked up in an additional process step. For the preparation of Na triumbuty 1ats an additional system is required, from which the metered addition to the reaction vessel. When using the low-boiling alcohols, methanol, ethanol and propanol, the target product chloroprene is contaminated by solvent residues, so that a subsequent purification is required.

Furthermore, a process for the preparation of chloropropenes is known in which aliρ ha ti se he dichloroalkanes (eg dichloropropane) with sodium hydroxide solution and an aliphatic hydroxy ether or an aliphatic polyalcohol are reacted as a reaction medium (US Patent 2,543,048). The disadvantage of this method is that the reaction mixture contains unreacted dichloroalkane and therefore the solvent used can be recovered only with great effort due to the relatively high boiling point.

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WP 203183 and WP 209184 describe the preparation of chloropropenes from dichloropropane in the presence of catalytic amounts of quaternary ammonium salts. The reaction is carried out with alkali metal hydroxide in liquid dichloropropane. This method also still has a significant defect. The eluted hydrogen chloride is completely bound by the alkali hydroxide. The utilization of the alkali chloride formed is difficult, since the separation of the toxic chlorinated hydrocarbons is possible only with great effort.

The catalytic or thermal pyrolysis of dichloropropane leads predominantly to allyl chloride. Bismuth salts and acids with heteropolymeric metal ions are used as catalyst (DP-PS 22302-79).

Allyl chloride is also formed upon laser irradiation of 1,2-dichloropropane (Japanese Patent No. 59073531).

At normal temperature is already the dechlorination of '1, 2-dichloropropane under the katalyti see influence of pure titanium instead. In this reaction, a mixture of propene and chloropropene is formed in a ratio of 9 to 1 (N. Levy 3. Chem. Soc. 1103/1946). The chlorine adsorbed on the catalyst surface contaminates the activated metal surface by the formation of titanium chloride, whereby stepwise deactivation occurs. The effect of the catalyzer is thus limited.

By means of an electrochemical dechlorination of perchloralkanes on the metal cathode in the presence of electrolytes, chloroalkenes can be deposited. The process is characterized by low conversion (SU-PS 702,702).

Object of the invention

The aim of the invention is to enable the conversion of 1,2-dichloropropane to chloropropane under simple apparatus conditions with a high degree of conversion of 1,2-oichloropropane, the final product should be obtained in the required purity and no further oxidizing starting materials be used.

Explanation of the essence of the invention The technical task

The invention has for its object to develop a process for the preparation of chloropropenes by elimination of hydrogen chloride from 1, 2-dichloroprop, in which no difficult to remove inorganic chlorides are formed and no reprocessed solvents used who need to.

Features of the invention

According to the invention, the object is achieved by passing the 1,2-dichloropropane in gaseous form over a catalyst in the temperature range from 373 to 573 K, preferably from 423 to 483 K. The catalyst used is an iron oxide-activated carbon combination which has been prepared by impregnating activated carbon with a suspension of iron oxides and / or iron oxide hydrates and then drying at temperatures of 353 to 473 K., preferably at 373 K. The iron occupancy of the catalyst must be 4 to 30% by mass, preferably 8 to 5% by mass.

Surprisingly, it has been found that under the conditions of the invention in high yields of chloroprene is formed and no poisoning of the catalyst or whether he surface occurs. The catalyst can be operated continuously without regeneration. The resulting chlorine water s t o -f f is separated from the chloropropene by conventional methods.

embodiments

Example 1 - -

The reaction of 1,2-dichloropropane is carried out with 200 ml of iron oxide catalyst on a Ak tivkohleträger with an occupancy of 27 % by mass in an apparatus consisting of a nickel tube reactor, metering for Dichlorprop on Di chi orpropane evaporator, washing device for the gaseous reaction product and measuring and control devices. The reaction mixture was washed after leaving the reactor of hydrogen chloride for egg and analyzed by gas chromatography.

Example 2

The experiment in Example 1 was repeated, except that an iron oxide catalyst with an iron occupancy of 11 % by weight was used.

The experimental conditions and the composition of the reaction gases are summarized in Table 1.

Table 1

Reaction retention reaction product temperature time 1-chloro-1-chloro ·

(K) (see) propen prop . ' ice trans

Example 1 423 7 S ₁ I 59.8

423 7 S ,1 473 7 10 , 5 483 8th 12 2 473 - 7. 7 ,8th 433 6 9 .2

Example 2 473 7 7.8 43.4

Claims (3)

He finder entitlement . 1. A process for the preparation of 1-chloropropenes by elimination of hydrogen chloride from 1, 2-dichloropropane in the presence of a catalyst, characterized in that i, 2-dichloro or propane is passed in gaseous form in the temperature range from 373 to 573 K over an iron oxide catalyst , 2. The method according to item 1, characterized in that the catalyst is an iron oxide activated carbon combination having a content of 4 to 30 mass % iron, preferably from 8 to 15 mass %, is applied. 3. The method according to item 1, characterized in that in the temperature range 423 to 483 K is worked.