DE1909434C - - Google Patents

Description

The invention relates to a process for the transesterification of the methyl acetate / methanol obtained from the azeotropic mixture methyl acetate separated off by extractive distillation with water Acetic acid butyl ester.

There are known methods, according to which the transesterification of the methyl acetate by treatment with Butanol is carried out in the presence of 5% hydrochloric acid. These methods have the disadvantage on that they were the spontaneous evaporation of the methanol formed in the reaction and the unreacted Do not allow acetic acid methyl ester.

Furthermore, US Pat. No. 1,491,076 discloses a process for the transesterification of methyl acetate with Butanol known in the presence of sulfuric acid. This process requires the reaction product to be distilled and / or rectified further work up (see p. 1, Zeüe63ff., and p. 2, Line 19 of the patent specification. The reaction is carried out above equilibrium. More details about molecular ratios and the like are missing.

In contrast, the process according to the invention is characterized in that the methyl acetate in vapor form into the hot reaction medium consisting of butanol and 0.1 to 2.0% sulfuric acid is introduced in a molar ratio of methyl acetate to butanol = 3.5 to 5.5.

A preferred implementation of the process takes place at one temperature of the reaction medium from 95 to 105 C.. .

In this way, with the help of the reaction, it is possible to obtain a butyl acetate as a reaction product, which has the concentration usually required (Commercial concentration), without it being necessary as in the known method that Work up the reaction product further by distillation and / or rectification.

The method according to the invention has the following advantages:

The methanol is recovered in very high yields;

the costs for the technology according to the invention are very low;

the methyl acetate-methanol azeotrope is completely recycled.

In the following, the method according to the invention is explained in more detail by means of exemplary embodiments:

Azeotrope water table 1 Out Back Out crowd crowd prey won
ner prey at Received methyl game G Mole Methanol % ester % 465 0.83 99 G 98 651 0.92 G 98 381 98 1 930 1.20 87.4 99 539 99 2 121.0 765 3 171.0

The first two examples were made by evaporating the azeotrope amounts given in the table executed in a glass flask provided with a glass packing column; the water for the Extraction of the methanol was introduced in the middle of the column. The third example was in the same Apparatus carried out except that the water was introduced near the top of the column. The difference between the amount of azeotrope introduced and the sum of the methanol obtained and acetic acid methyl ester is based on the 3% water content of the column obtained on the Kopi uer Acetic acid methyl ester attributed.

The transesterification was carried out in a glass flask equipped with a dephlegmator, at temperatures carried out from 95 to 105 C, 0.1 to 2% sulfuric acid was used as a catalyst.

For transesterification, molar ratios of methyl acetate to butanol between 3.5 and 5.5 were used used. The methyl acetate was in vapor form in the butanol and sulfuric acid containing glass bulb initiated. During the entire transesterification process, this was ensured by the Methanol formed in the reaction was removed by distillation. The dephlegmator used guaranteed the permanent and complete reflux of the less volatile fractions (butanol and acetic acid butyl ester).

The results obtained are summarized in Table 2:

Table 2

example Butanol + vinegar
acid-methyl-
ester amount
G Molar ratio
Acetic acid methyl
ester to butanol Back
won
Acetic acid-
methyl ester
G yield
% Acetic acid-
butyl ester
β Acetic acid-
butyl ester
salary
% yield
% 1
2 1320
2600 4.5
4.2 847
1617 98
98 370
754 89 /
90.8 97.5
97.2

In column 5, the yields of recovered methyl acetate are based on the methyl acetate that was not converted in the reaction;

Acetic acid butyl ester in about 90% concentration (see column 7) and in column § the yields of 100% acetic acid butyl ester

Claims (2)

Patent claims: 1. Process for the transesterification of the azeotropic mixture of methyl acetate / methanol methyl acetate separated off by extractive distillation with water to give butyl acetate with butanol in the presence of sulfuric acid, characterized in that that the methyl acetate in Introduces IO vapor form into the hot reaction medium consisting of butanol and 0.1 to 2% sulfuric acid in a molar ratio of methyl acetate to butanol = 3.5 to 5.5 2 Process according to Claim 1, characterized in that the temperature of the reaction medium is 95 to 105 ^° C.