DE1270548B - Process for the dehydrochlorination of chlorinated hydrocarbons - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Int. Cl .:

C 07c

D 061

German class: 12 o-19/02
"8i-5

Number: 1270 548

File number: P 12 70 548.5-42

Filing date: December 20, 1966

Opening day: June 20, 1968

The invention relates to a process for the dehydrochlorination of chlorinated hydrocarbons by heating the same in the presence of alkyl and / or aryl phosphine and / or their hydrochlorides or Quaternary phosphonium chlorides as a catalyst at temperatures between 100 and 250 ° C and distilling off the cleavage products and the hydrogen chloride, which is characterized in that one the dehydrochlorination is carried out at pressures between 2 and 21, preferably 2 and 11, ata.

The dehydrochlorination can be especially chlorinated hydrocarbons with aliphatically bound chlorine and subject to hydrogen, which may optionally be substituted by an aryl group. at aliphatic chlorohydrocarbons with 2 to 18, preferably 2 to 4 carbon atoms are split off of hydrogen chloride run particularly smoothly. For example, you can 1,2,3-trichlorobutane, optionally in a mixture with tetrachlorobutanes, to a substantial extent of 1,2-dichlorobutene- (2), 1,3-dichlorobutene- (2) and 2,3-dichlorobutene- (l) existing mixture dehydrochlorinate, which in turn a is an important starting product for the further dehydrochlorination to 2-chlorobutadiene- (l, 3). Farther can be split off from 1,4-dichlorobutene- (2) and / or 3,4-dichlorobutene- (l) hydrogen chloride, whereby mixtures of 2-chlorobutadiene (1,3) and 1-chlorobutadiene (1,3) are obtained, which are known in the art Versatile use as monomers and co-monomers as well as diene or dienophilic components have found. Furthermore, you can 1,1,2,2-tetrachloroethane to trichlorethylene, one in the »Chemical Cleaning «dehydrochlorination of solvents that have been tried and tested many times and are also suitable for degreasing metals.

Trialkylphosphine or triarylphosphine and alkylphosphines with 4 are particularly suitable as catalysts up to 18 carbon atoms per alkyl group. You can, for example, 0.1 to 20, preferably 0.5 to 15 parts by weight Use catalyst per 100 parts by weight of chlorinated hydrocarbons.

The following alkyl radicals are suitable, for example, as “alkyl” in the alkylphosphines: η-butyl, isobutyl, n-pentyl, n-hexyl, n-heptyl, n-octyl, n-nonyl, n-decyln-undecyl, n-dodecyl (Lauryl), palmityl or stearyl. The di- and trialkylphosphines can also contain various alkyl groups. Particularly suitable arylphosphines are triphenylphosphine, which is easy to handle because of its good resistance to atmospheric oxygen, but also the various tritolyl- or trixylylphosphines. The alkyl or aryl phosphines or their hydrochlorides or processes for the dehydrochlorination of
Chlorinated hydrocarbons

Applicant:

Knapsack Aktiengesellschaft, 5033 Knapsack

Named as inventor:
ίο Dipl.-Chem. Dr. Herbert Baader,

5030 Hermülheim;

Dipl.-Chem. Dr. Kurt Sennewald,

5033 Knapsack;
Helmut Reis, 5030 Huerth;

Günther Vierling, 5040 Brühl

Quaternary phosphonium chlorides behave in the process according to the invention as real catalysts, and each molecule of the catalyst causes dehydrochlorination of many molecules of chlorocarbon-hydrogen. The inventive method can

a5 can be carried out by adding the reaction mixture only a suitable tertiary phosphine is added, with hydrochloride and quaternary phosphonium chlorides Form by themselves in the presence of hydrogen chloride or chlorinated hydrocarbons.

Although it is in some hydrochlorofluorocarbons even to a small extent below 100 ° C using triphenylphosphine elimination of Chlorwasserstofffeststellbar, should higher to obtain catalyst performances gap temperatures between 130 and 25O ⁰ C, preferably, set 140 to 210 ⁰ C.

The rate of dehydrochlorination depends on the amount of catalyst (e.g. triphenylphosphine, Tributylphosphine, trilaurylphosphine, trip-tolylphosphine etc.), which can be changed accordingly. Maximum sales are often already included only 0.5 parts by weight of catalyst per 100 parts by weight of chlorinated hydrocarbon, e.g. B. 1,2,3-trichlorobutane, obtain. As the reaction rate increases, with about 4 to 8 parts of catalyst, the respective maximum sales achieved. Conversions are still good with 32 parts of catalyst, but with increasing amount of catalyst polymerization, because then more than 1 mole of hydrogen chloride per mole 1,2,3-trichlorobutane is split off.

By increasing resin formation when more than about 25 weight percent catalyst is used

809 560/519

the yield of the desired dichlorobutenes is reduced, d. that is, the selectivity of the catalyst is lost. Defined as "catalyst performance" the amount of cleavage products (e.g. dichlorobutenes) in grams which, with 1 g of catalyst, dissolved in 11 chlorinated hydrocarbons (e.g. 1,2,3-trichlorobutane) can be obtained per hour, it is the case that the catalyst performance increases with increasing Reduced catalyst concentration.

In technology, it is therefore necessary to work with solutions that are as dilute as possible in order to obtain the catalyst to use optimally and to obtain good yields. However, this requires large reaction vessels, in order to be able to convert as much chlorinated hydrocarbon as possible in the unit of time. The processing of the large amounts of liquid cause additional costs.

These disadvantages can be eliminated by increasing the catalyst performance, so that one can without enlargement the apparatus receives a multiple of the hourly produced amount of fission products without that the yield would thereby be reduced.

For this purpose, it is necessary according to the invention to carry out the elimination of hydrogen chloride at elevated pressure. For example, the chlorinated hydrocarbons can be ^{heated at temperatures between 140 and 210 °} C. in a closed reaction tube. On the other hand, it is also advantageous to adjust the pressure and temperature so that the chlorinated hydrocarbon just boils with elimination of hydrogen chloride. As a result, the olefins formed are driven off more easily.

A simple test arrangement for this is z. B. a pressure distillation, which is very easy with a valve regulate the amount of gaseous hydrogen chloride to be discharged and thus the desired amount Can adjust pressure in the bladder and the column. On the other hand, you can also use the dehydrohalogenated Chlorinated hydrocarbon along with the dissolved catalyst under pressure through a flow reactor lead, the reaction mixture relax immediately after the reactor and the further expansion

carry out the work by distillation under normal pressure. The resulting swamp, the containing dissolved catalyst is mixed with fresh chlorinated hydrocarbon and returned to the reactor returned.

The increase in catalyst performance through the application of pressure is due, among other things, to that with the Increase in pressure associated with an increase in the boiling temperature. Despite higher gap temperature and higher pressure, however, no increased formation of polymers or Resins. Incidentally, the increase in catalyst performance under hydrogen chloride pressure is surprising because at dehydrochlorination increases the number of moles:

1 mole of chlorinated hydrocarbon

- > 1 mole of olefin + 1 mole of HCl

The increase in the catalyst performance now makes it possible either to use smaller amounts of catalyst or to use smaller reactors. In addition, you save costs for heating, cooling and pumping of chlorinated hydrocarbons, since there is more dehydrochlorinated in the same reactor volume Fission product in the unit of time, is able to produce.

example

1,2,3-trichlorobutane, which is still about 8 percent by weight Containing 2,2,3,3-tetrachlorobutane, was continuously in a half-filled 4-1 bladder one Initiated pressure distillation apparatus in which there were 134 g of triphenylphosphine. It sat down the 1,2,3-trichlorobutane to a mixture of 1,2-dichlorobutene- (2), 1,3-dichlorobutene- (2) and 2,3-dichlorobutene- (l) um, the overhead together with the not convertible 2,2,3,3-tetrachlorobutane was removed. The pressure distillation was carried out at about 3 ata.

The table shows a comparison of two

Experiments carried out in the same apparatus with 134 g triphenylphosphine at different pressures became.

pressure
(ata) Bladder temperature
( ⁰ Q Head temperature
( ⁰ Q Operating time
(Hours) Deployed
Trichlorobutane
(G) Received
Dichlorobutene mixture
(G) Catalyst performance
(g dichlorobutene
mix per hour
and g triphenyl
phosphine) 1
3 165
195 130
158 34
32 20.931
32.240 14.625
22.011 3.2
5.1

Claims (3)

Patent claims: 1. Process for the dehydrochlorination of chlorinated hydrocarbons by heating them in Presence of alkyl and / or aryl phosphine and / or their hydrochlorides or quaternary Phosphonium chlorides as a catalyst at temperatures between 100 and 250 ° C and distilling off the cleavage products and the hydrogen chloride, characterized in that the Carries out dehydrochlorination at pressures between 2 and 21, preferably 2 and 11, ata. 2. The method according to claim 1, characterized in that the dehydrochlorination is carried out at temperatures between 140 and 210 ⁰ C in a closed reaction tube. 3. The method according to claim 1, characterized in that the dehydrochlorination in the Performs boiling point of the chlorinated hydrocarbon. 809 560/519 6.68 © Bundesdruckerei Berlin