DE1253700B - Process for the production of olefins - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Int. Cl .:

C07c

German class: 12 ο - 19/01

Number: 1253 700

File number: F 31069IV b / 12 ο

Filing date: April 23, 1960

Opened on: November 9, 1967

It is known that olefins with a terminal double bond can be obtained from α, / ί-dihaloalkanes by cleavage of the halogen atoms with metals, for example with zinc.

Furthermore, the production of olefins is of the general formula

Ri
R ₂ - C - CH = CH ₂

R ₃

where Ri, R ₂ and R _{3 are} lower aliphatic hydrocarbon radicals, have been described several times in the literature. Saturated compounds of the formula are used here

Ri
R ₂ - C - CH - CH ₃

R ₃ X

from, in which X is a negative radical, for example halogen, hydroxyl, etc., and splits off HX in the presence of catalysts at higher temperatures. For example, 3,3-dimethylbutene- (l) can be prepared from 3,3-dimethyl-2-hydroxy-butane in the presence of aluminum oxide, quartz, pottery shards, aluminum sulfate, etc. at temperatures between 300 and 500 ^° C. with elimination of water . Instead of the free hydroxyl compound, you can also use its acetic acid or xanthogenic acid ester, in which case acetic acid or xanthogenic acid (the latter in the form of its decomposition products) are split off.

You can also use olefins of the formula given above, in which Ri is also hydrogen and that terminal methylene carbon atom can carry a chlorine atom, also by splitting off HX under the above conditions from compounds of the type

Ri

R2 C - CH2 - CH2
R ₃ X

produce. So you get by heating 3,3-dimethyl-l, l-dichloro-butane in the presence of Process for the production of olefins

Applicant:

Farbwerke Hoechst Aktiengesellschaft

formerly Master Lucius & Brüning,

Frankfurt / M.

Named as inventor:

Dr. Lothar Hörnig, Frankfurt / M.-Schwanheim;

Dr. Rudolf Wirtz, Göggingen;

Dr. Otto Probst, Frankfurt / M.-Höchst

at

450 ° C

3,3-dimethyl-1-chloro

Calcium chloride
buten- (l).

It is also known from 3-methylpentanol-l-acetate the formula

CH ₃ - C - CH ₂ - CH ₂ - O - COCH ₃

CH ₃

Acetic acid thermally at temperatures between 500 and 510 ° C with the formation of 3-methylpentanol-1 split off. The starting compound subjected to thermal cleavage, however, has a carbon atom starting from the side chains only a tertiary carbon atom, with which the risk that it to the starting point is undesirable Experience has shown that rearrangements are not given or only to a minor extent.

Finally, it has already been described, Nonylacetate with quaternary carbon atom on thermal Ways to convert into 2-neopentyl-1,3-butadiene. However, rearrangements occur here at the quaternary C atom on.

The invention now relates to a process for the preparation of olefins of the general formula

Ri Zi

R ₂ - C - CH = C
R _{3 line 2}

where Ri, R ₂ and R _{3 are} each an alkyl radical and Zi and Z2 are each a hydrogen, chlorine, bromine

709 «7/431

or fluorine atom, characterized in that from saturated compounds of the general formula

Ri Zi

2 ^ - ^ rl 2 * - Λ.

R _{3 line 2}

where Ri, R2, R3, Zi and Z2 have the meaning given above and where X is chlorine or bromine, but also, if both Zi and Z2 are hydrogen, a hydroxyl or alkoxy group or a carboxylic acid radical R4 - CO - O - may mean, in the gas or vapor phase with the exclusion of catalysts ^{, HX is split off exclusively by thermal means at temperatures between 350 and 800:} C and with a residence time not exceeding 5 seconds. It is surprising here that thermal cleavage takes place so smoothly in the desired direction, although it was to be expected that undesired rearrangements would occur at the quaternary carbon atom of the starting compounds.

Preferred saturated starting compounds here are those in which Ri, R2 and R3 each Represent methyl or ethyl groups. Ri also preferably denotes a methyl or ethyl group. For X, chlorine is preferred in many cases.

Depending on the nature of the substituent X, the saturated compound will be thermally treated Splitting off water, alcohol, carboxylic acid or hydrogen halide. The thermal cleavage is preferably at temperatures between 500 and 700 ° C and with an average residence time in Cleavage reactor of less than 2 seconds, in particular less than 1 second, carried out.

HX can be split off under normal pressure, if appropriate also under increased pressure. In particular, when HX is hydrogen chloride or hydrogen bromide, it is 10 to 40 atmospheres, preferably 20 to 30 atm.

It is expedient to preheat the saturated starting compound in an evaporator upstream of the cleavage reactor, but only to the extent that practically no cleavage of the compound takes place in the evaporator. The temperature in the evaporator is located, for example, about 100 to 300 ⁰ C below the dissociation temperature.

Evaporation and cleavage of the saturated starting compound are expedient in a tube furnace or running coils, which are made of corrosion-resistant material and one possible Ensure a defined average residence time in the evaporation and cleavage zone.

It is advantageous to break up the reaction mixture as quickly as possible after it has left the cleavage zone to cool or quench a temperature that does not require further cleavage or change, for example Isomerization, which allows products contained in the reaction mixture and which is preferred is below the temperature in the evaporation zone.

The inventive method is characterized in that the main products of the thermal Cleavage of unsaturated compounds of the general formula given at the outset can be obtained.

However, if HX is split off at longer than the average residence times given above and / or in the presence of catalysts that are used in thermal cleavage, such as Aluminum oxide, quartz, pottery shards, aluminum sulfate, etc., thus attained the speed of the said Side reactions considerable values. The formation of the isomeric by-products known as Contact isomerization (I ρ a t j e w) is known from the literature and is based on a migration of alkyl groups is based on a change in the carbon structure, then becomes the main reaction, which results in that the process products falling under the above formula only to a small extent or not be formed at all. For example, 2,2-dimethylbutene- (3) is used in the presence of aluminum sulfate almost quantitatively converted into tetramethylethylene and 2,3-dimethylbutene- (3) at about 300C.

The unreacted saturated saturates contained in the reaction mixture obtained according to the invention The starting substance is advantageously recirculated to the preheater in the circuit after it has been isolated Cleavage zone fed. When converting saturated compounds in which the substituent X is a chlorine or bromine atom, or an alkoxy or a Ri - CO - O group, is expedient a second circuit is connected, in which the hydrogen halide, alcohol, obtained at the same time or the carboxylic acid is isolated in the gaseous, vaporous or liquid state and for recovery of starting materials for the preparation of the saturated feed is used, the can then in turn also be fed back to the preheater and the cleavage zone. the Saturated starting compounds can easily by methods described in the literature, for example by condensation of a compound of the general formula

^Rl \ _c / ^X
R ₂ '^ R ₃

with an unsaturated compound of the general formula

Z2

in the presence of Friedel-Crafts catalysts, such as aluminum chloride or iron (III) chloride, etc., obtained will.

The olefins prepared according to the invention are valuable intermediates and are suitable for Polymerization and copolymerization.

example 1

a) 0.25 mol of 1-chloro-3,3-dimethylbutane was evaporated hourly in a 30 cm long steel coil with an internal diameter of 4 mm at 300 ^° C. and in an adjoining cleavage zone thermally at a temperature of 570 ^° C. in the absence of catalysts exposed. The cleavage zone consisted of a 240 cm long tube made of temperature-resistant, corrosion-resistant steel with an internal diameter of 2 mm.

The hot reaction mixture leaving the cleavage zone was cooled by means of a 30 cm long air cooler Made of steel with an inner diameter of 4 mm and an intensive cooler condensed and in one Cutter caught. A total of 23.2% of the saturated chlorine-containing substance used was used implemented.

The reaction product consisted of 90% of the desired unsaturated main product 3,3-dimethylbutene- (l) and only about 3.5% from the unsaturated isomeric by-products 2,3-dimethylbutene- (l) and 2,3-dimethylbutene- (2). Unreacted feedstock was after separation recycled from the olefins and subjected to a renewed reaction. The one at the Anhydrous hydrogen chloride resulting from the reaction was added to isobutylene by known processes tert-butyl chloride reacted, which in turn in the presence of aluminum chloride with ethylene in 1-chloro-3,3-dimethylbutane was implemented.

At the same time, the thermal cracking produced about 0.5 l of exhaust gas per hour, essentially consisted of ethylene and isobutylene, which may also be used to obtain the feedstock in the Can be returned to the cycle.

b) On the other hand, if one worked in an apparatus which corresponded to that specified under a) with the only difference that the cross-section of the cleavage zone was not 2 mm. but was 3 mm, and were introduced per hour instead of 0.25 mole only 0.14 MoI l-chloro-3,3-dimethylbutane after evaporation at 300 ° C in the reaction zone, the thermal cracking at 500 ⁰ C and passed through if the hot reaction mixture leaving the cleavage zone cooled in the manner indicated under a), only 16.3% of the saturated chlorine-containing substance used were converted. In this case, the reaction product consisted of only 37% of the desired 3,3-dimethylbutene- (1), on the other hand 55% of the undesired isomerization products 2,3-dimethylbutene- (1) or - (2). The desired main reaction has become a secondary reaction because the mean residence time is considerably longer than under the conditions given under a).

45 Example 2

267 g of 3,3 - dimethylbutanol - (I) - essigsäureester were evaporated at 250 ⁰ C and cleaved thermally at 600 ° C in 3,3-Dimethylbuten- (l) and acetic acid. The residence time in the tubular reactor, which had a length of 550 mm and an internal cross section of 6 mm, was 1 second. The total conversion of the cleavage was 85% (measured on the acetic acid split off). The amount of olefin equivalent to acetic acid consisted practically quantitatively of 3,3-dimethylbutene- (I), which was obtained by fractional distillation (boiling point 41.2 ^: C).

60

Example 3

In the manner described in Example 1 a) Experimental Apparatus hourly 0.25 mol l-chloro-3,3-dimethylpentane (Kp 15O'C / 76Omm) were. Introduced evaporates the chlorinated hydrocarbon at 32O ⁰ C and 55O ⁰ C in thermally at Treated absence of catalysts in the cleavage zone.

The cleavage conversion was 17.5% (based on the hydrochloric acid split off). That of hydrochloric acid equivalent amount of olefin consisted practically quantitatively of 3,3-dimethylpentene- (l), which by fractional distillation (b.p. 77 ° C / 760mm) was obtained.

Example 4

0.66 mol of l, l-dichloro-3,3-dimethylbutane per hour were evaporated in a heated at 200 ⁰ C vessel and thermally cracked in a subsequent quartz tube at a temperature of 520 ° C and a residence time of 4.3 seconds. The hot reaction mixture leaving the cleavage zone was condensed by means of a condenser and collected in a separator. The conversion was 67% and the yield of the desired 1-chloro-3,3-dimethylbutene-l was 83%, based on the amount converted

., 1-dichloro-S ^ -dimethylbutane.

The 1-chloro-3,3-dimethylbutene-1 could be separated into the cis and trans isomers not previously described by fractionation. The ice compound boils at 99 to 100 ⁰ C, the trans-compound at 105 to 107 ⁰ C (umkorrigiert). The ratio of the trans compound to the cis compound was

5.2: 1.

Claims (6)

Patent claims: 1. Process for the preparation of olefins of the general formula Ri Z, C-CH = C
R3 line ₂ in which Ri, Ro and R ₃ each denote an alkyl radical and Zi and Z) each denote a hydrogen, chlorine, bromine or fluorine atom, characterized in that one of saturated compounds of the general formula Ri R ₂ -C- CH ₂ - C - X
R _{3 line 2} where Ri, R ₂ , R3, Zi and Z _{2 have} the meaning given above and where X is chlorine or bromine, but also, if both Zj and Z2 are hydrogen, a hydroxyl or alkoxy group or a carboxylic acid radical R ₄ - CO - O - can mean in the gas or. The vapor phase with the exclusion of catalysts is split off exclusively by thermal means at temperatures between 350 and 800 ° C. and with a residence time HX not exceeding 5 seconds. 2. The method according to claim 1, characterized in that the saturated starting compounds used are those in which Ri and Ro and R _{3 are} alkyl groups having 1 to 2 carbon atoms. 3. Process according to Claims 1 and 2, characterized in that the saturated starting compounds used are those in which X is chlorine or the acetic acid residue CH ₃ - CO - O -. 4. Process according to Claims 1 to 3, characterized in that the thermal cleavage in the Temperature range between 500 and 700C is carried out. 5. Process according to Claims 1 to 4, characterized in that the thermal cleavage at a dwell time of less than 2 seconds is carried out. 6. The method according to claims 1 to 5, characterized in that in the thermal cleavage accruing hydrogen halide, alcohol or formed carboxylic acid in the circuit for the production development of compounds of the general formula Ri R ₃ used, in turn, as the starting material serve to obtain the saturated starting compounds. Publications considered: J. Org. Chem., 24 (1959), pp. 1399 ff .; J. Am. Chem. Soc, 74: 4073 (1952); 61: 231 (1939); 55: 3721 (1933); 62: 2448 (1940); 58 (1936), pp. 373, 374; 70: 381 (1948); Chemical Reports, 46, p. 246. 709 687/431 10.67 θ Bundesdruckerei Berlin