DEST008534MA - - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

Registration date: July 29, 1954. Advertised on November 29, 1956

GERMAN PATENT OFFICE

CLASS 12 0 GROUP INTERNAT. CLASS C07c

St 8534 IVb / 12 ο

have been named as inventors

and carbon dioxide

Addendum to patent 942

In the main patent 942 987 is a process for the production of carboxylic acids from olefins and carbon monoxide in the presence of at least 90% sulfuric acid, anhydrous hydrogen fluoride alone or below Addition of boron trifluoride in the liquid phase initially described without the addition of water, the The reaction product is then taken up in water and worked up in a known manner. The implementation can be carried out under a pressure of up to 100 atm.

It has now been found that by increasing the carbon oxide pressure certain rearrangements of the olefins pushed back and preferably "normal", i. H. carboxylic acids formed without rearrangement in a simple way Way can be made. By increasing the carbon monoxide pressure, 1. the migration the methyl group is suppressed, through which it leads to the formation of tertiary in place of »normalcc secondary Carboxylic acids come, and 2. the dimerization of the olefins is suppressed by the otherwise higher molecular weight Carboxylic acids are formed.

The methyl group migration occurs preferentially with unbranched olefins; H. with those who at of the double bond do not bear any branching. at

609 709/403.

St 8534 IVb / 12 ο

Dimerization plays no role in this class of olefins, whereas olefins branched on the double bond have a strong tendency to dimerize , and they do not migrate methyl groups.

Using the example of the implementation of two isomeric pentenes, a) the unbranched pentene-2 and b) the one at the Double bond branched 2-methylbutene-2, the course of the reaction is particularly clear.

a) The "normal" reaction products from pentene-2 would be the two secondary Cg-carboxylic acids, ct-methylvaleric acid (Methylpropylacetic acid) and α-ethylbutyric acid (diethyl acetic acid).

H ₃ C-CH ₂ -CH = CH-CH ₃ -I-CO + H ₂ O

As a result of the migration of methyl groups, however, a tertiary acid is also formed, possibly even preferably, namely a, ez-dimethylbutyric acid (dimethylethyl acetic acid).

CH ₃

CH ₃ -CH ₂ -C-COOH

.. ■. ■: ^■■: ch ₃

b) The reaction product of the pentene isomer 2-methylbutene-2, which is branched at the double bond, contains only the uniform tertiary a, ct-dimethylbutyric acid _{as C 6 -carboxylic acid.} At low carbon oxide pressure, however, dimerization to a branched decene takes place, which then reacts with carbon oxide and _{gives a mixture of C n} -carboxylic acids.

The process according to the invention succeeds in eliminating these rearrangements, which are undoubtedly undesirable in many cases, the z. B. as a result of the methyl group migration at 100 at about 42% and as a result of dimerization at 100 at still be 38%, to be suppressed as far as possible. The rearrangements are essentially suppressed within the pressure range between 100 and 600 at, preferably within one Pressure range between 100 and 300 at.

example 1

In two test series with penten-2 as the starting

olefin was investigated to what extent by increasing the carbon oxide pressure substantially over 100 at, the migration of methyl groups and thus the formation of the tertiary carboxylic acid is suppressed will. The tests ... of series a) were carried out on a

, ■ temperature of + 5 ° carried out, while in test series b) a temperature of -5 ^{0 was} maintained. The other test conditions were the same for all approaches. The molar ratio of olefin to concentrated sulfuric acid (97%) was 1:10,

_c r the duration of the experiment in each case 20 hours, and the pentene-2 was diluted with 2.5 times the amount of n-pentane, applied. A V4A extra autoclave with magnetic stirring with a capacity of 2 1 served as a reaction vessel, which was filled with 0.5! concentrated sulfuric acid charged

- C-H η

C Hg C H2

C Ho - C Ho

; cH — coöH

CH-COOH

CH,

and already had the desired carbon oxide pressure before the olefin was injected with the aid of a pressure feed pump. After the uptake of carbon dioxide had ended, the reaction product was decomposed with ice water and the carboxylic acids formed were separated off from the organic layer floating on top by means of their alkali metal salt solutions. The fatty acids set free from this were broken down by fine fractionation using a rotating band column, whereby a separation of the lower-boiling tertiary acid formed by rearrangement from the two secondary acids formed without methyl group migration could be achieved. The 'identification of the carboxylic acids present in the various fractions was carried out on the basis of the physical constants and additionally by recording the infrared spectra. The tertiary acid was a, cc-dimethylbutyric acid (b.p. ₂₀ = 96 °, np ° = 1.4142), while the secondary acids were a mixture of a-methylvaleric acid (b.p. ₂₀ = 102.5 , w ^ ° = -1.4138) and a-ethylbutyric acid (bp ₂₀ = 101, nf = 1.4133).

Test series a), temperature + 5 °

° / ₀ -Ausbeuten of carboxylic acids of that tertiary Carbon dioxide secondary Acids pressure (at) Acids 73 total 27 42 50 9 ¹ 58 19th IOO 93 8l 600 93

Test series b), temperature - -5 ^C of that tertiary secondary Acids Carbon dioxide ° / ₀ -Ausbeuten of carboxylic acids Acids 48.0 pressure (at) 52.0 33.0 67.0 29.0 50 total 71.0 21.5 IOO 89.5 78.5 ■■■ 14.0 200 95, o 86.0 3OO 99.0 600 99.0 99, o

709/403

St 8534 IVb / 12 ο

Example 2

Under the test conditions chosen in Example 1 the conversion of pentene-i was investigated as a function of the carbon oxide pressure, whereby likewise a strong suppression of the migration of methyl groups leading to the tertiary carboxylic acid was established. The results are summarized in the table below:

Verse.- "/ (, - yield of carboxylic acids of that tertiary Carbon dioxide Temp. (° C) secondary Acids pressure (at) Acids 64.0 ■ +5 total 36.0 41.5 50 +5 82.0 58.5 46.5 150 (Jl 89.5 53.5 24.0 50 5 8o, O 76.0 200 87.0

The carboxylic acids obtained from pentene-i were found to be identical to the compounds formed from pentene-2. While in Examples 1 and 2, the methyl group migration is suppressed the olefins pentene-1 and pentene-2 not branched at the double bond by using a The following Examples 3 show the carbon oxide pressure which is increased significantly above 100 at and 4 the inhibitory effect of the increased carbon oxide pressure on the dimerization of the at the double bond branched olefins.

Example 3

Isobutene was reacted with carbon monoxide at a temperature of ⁰ -f 5 in the presence of 97 ° / _o sulfuric acid. The molar ratio of olefin to sulfuric acid was 1: 7 and the test lasted 15 hours. A 2 l V4A extra autoclave with magnetic stirring, in which 0.5 l of the concentrated sulfuric acid had been placed and into which the isobutene was injected at the desired carbon oxide pressure, again served as the reaction vessel. The reaction products were worked up and the carboxylic acids were isolated using the procedure described in Example 1. The main compounds obtained were trimethyl _{acetic acid (boiling point 2o} = 76.5 °, melting point = 35.5 °) and a mixture of ^ -carboxylic acids derived from the dimer of isobutene. Besides . Small amounts of carboxylic acids with a different carbon number were found, which were formed by disproportionation of the diisobutene. The following table contains the test results obtained at 50, 100 and 200 atmospheres of carbon dioxide pressure. When the carbon oxide pressure was increased from 100 to 200 atm, the proportion of C ₉ carboxylic acids was reduced from 38 to 9%.

"/ (, - yield of carboxylic acids of that C ₀ carbon Carbon dioxide Trimethyl acid pressure (at) total acetic acid 44 ■ 56 38 50 75 62 9 100 90 9 ¹ 200 92

Example 4

Served as the starting 2-methyl-i, the at with carbon monoxide at a pressure between 50 and 600 in the presence of o, 7 ° / ₀ sulfuric acid was reacted. The molar ratio of olefin to sulfuric acid was 1: 9; Otherwise, the execution of the experiment and work-up proceeded analogously to the conversion of isobutene in Example 3. A , a-dimethylvaleric acid ( _{boiling point 20} = 10 °, η ² £ = 1.4210) was obtained as a main product of the reaction. The second main product consisted of a mixture of C ₁₃ carboxylic acids which were formed by dimerization of 2-methylpentene-i. In addition, small amounts of carboxylic acids with a different carbon number had formed as a result of disproportionation reactions. The results summarized in the table below clearly show that the formation of the C ₁₃ carboxylic acids due to the dimerization is strongly suppressed by the increase in the carbon oxide pressure to well above 100 atm.

° / ₀ yield of carboxylic acids of that C ₁₃ carbon Carbon dioxide α, α-dimethyl pressure (at) valeric acid total 52 50 71 70 130 83 85 200 81 89 acid 600 82 48 30th 15th II

Claims (1)

Claim: Process for the preparation of carboxylic acids from olefins and carbon monoxide in the presence of at least o, o% sulfuric acid, anhydrous hydrogen fluoride alone or with the addition of boron trifluoride as a catalyst, the reaction initially in liquid form without the addition of water Phase carried out and the reaction product then taken up in water and known in Way is worked up, according to patent 942 987, characterized in that the implementation at a pressure between 100 and 600 at, preferably between 100 and 300 at, is carried out. © 609 709/403 11.56