DE1006848B - Process for the continuous production of acid-free esters of low molecular weight aliphatic carboxylic acids - Google Patents

Description

GERMAN

It is known that esters boiling higher than water and the alcoholic component are lower aliphatic carboxylic acids using acidic catalysts, e.g. B. sulfuric acid, p-toluenesulfonic acids or hydrochloric acid, phosphoric acid and thionyl chloride, and with simultaneous removal of the water formed during the reaction. Carrying out the continuous esterification makes difficulties because it is proportionate to achieve a substantial esterification of the carboxylic acid large amounts of esterification catalyst, e.g. B. 0.1 percent by weight sulfuric acid and more, required are. As a result, severe corrosion damage occurs in the column, which the apparatus prematurely to make something useless. Another disadvantage is that the crude ester obtained is before the distillation must undergo an alkaline wash, otherwise it leads to such a high acid concentration comes that disruptive side reactions occur and larger amounts of high-boiling distillation residue can be obtained.

It has now been found that esters which are higher than Water and the alcoholic component boil, from low molecular weight aliphatic carboxylic acids without let the disadvantages mentioned be produced continuously if one is under an esterification column Removal of the water formed in the reaction and recycling of the alcohol which has been distilled off Carboxylic acid, the alcohol and a maximum of 0.02 percent by weight sulfuric acid as a catalyst individually or as a mixture, the downward flowing reaction mixture in a connected to the column, provided with a distillation device and kept at at least the boiling point of the ester The vessel collects the crude ester, which is free of sulfuric acid, in vapor form from the distillation vessel and continuously draining the esterification residue at the bottom of the vessel.

Suitable low molecular weight aliphatic carboxylic acids, which are saturated or unsaturated, straight-chain or can be branched, are z. B. formic acid, acetic acid, propionic acid, α-methylpropionic acid, butyric acid, Valeric acid, isovaleric acid, acrylic acid, methacrylic acid, vinyl acetic acid and propiolic acid.

The alcohols used can be those of the aliphatic, araliphatic or cycloaliphatic series if the esters made from them boil higher than the alcohol and water used.

The process is particularly suitable for the production of esters of carboxylic acids and those alcohols which are not miscible with water and form azeotropically boiling mixtures with it, because then the separation and recycling of the reactant

for continuous production

of acid-free esters of low molecular weight

aliphatic carboxylic acids

Applicant:

Badische Anilin- & Soda-Fabrik Aktiengesellschaft, Ludwigshafen / Rhein

Dr. Walter Kölsch, Ludwigshafen / Rhine, and Dr. Hans Joachim Pistor, Mannheim,

have been named as inventors

tion water of distilling alcohol is particularly simple.

An example embodiment of the method is described in more detail with reference to the drawing. Through line 2, one leads into the esterification column 1, which can be filled with random packings A mixture consisting of a low molecular weight aliphatic carboxylic acid and an alcohol in excess, expediently 1 to 3 mol, based on 1 mol of carboxylic acid used, and a maximum of 0.02, advantageous 0.01 weight percent concentrated sulfuric acid. From the at the esterification temperature, z. B. the boiling temperature of the water or the azeotropic boiling alcohol-water mixture held The esterification column distills some of the water formed in the reaction overhead of the alcohol through line 3. In the condenser 4 and cooler 4 ° it is condensed and cooled and in the template 5 is collected with the vent 6. The fluid level is in the template indicated by the sight glass 9. After the alcohol has separated from the water, which is caused by the Sight glass 10 can be seen, it is at least partially through the line 7 as a reflux into the upper Column part returned, while a remaining part withdrawn through the drain valve 18, if desired can be. Line 8 is used to remove the water of reaction.

The ester-containing reaction mixture flows in the column 1 downwards into that immediately with the column connected still 11. It is kept at a temperature by a heater at which the crude ester is distilled off. The crude ester escapes from the conversion mixture immediately through the line

709 '506/427

Claims (1)

3 4 device 15 and cooler 16, while at the bottom of the vessel the hourly withdrawn from the drain valve 14- Via the cooler 13 and the drain valve 14 of the veins 38 g consist of the sulfur used esterification residue is continuously drained. acid, 93% isobutyl propionate, 5% isobuta- The sight glass 12 shows the liquid level in the nol, 1/10 propionic acid and 0.5% water.
Alembic on. 5 The overhead of column 1 in a mixture with Example isobutanol azeotropically distilled water is through ,,,. . . _ΛΤ ,,. , _, Taken from line 8. The hourly from line 18 It is passed into an esterification column 1 (see drawing amount of isobutanol withdrawn is 33.5 g.
nung) of 200 cm in length and 4 cm in diameter, the
filled with fillers and their lower end directly ₁₀ is connected to the still 11 by the claim
Line 2 hourly 1000 g of a mixture 39% propionic acid, 61% isobutanol (99%) and process for the continuous production of 0.01% concentrated sulfuric acid. The distilling acid-free esters of low molecular weight aliphatic vessel 11 is heated in such a way that a temperature of 89 to 95 ° that of the water and the alcoholic component is established at the top of the esterifying carboxylic acids, whose boiling points are higher than that of the water and alcoholic components, and the nente returned through line 7 , in an esterification column under Ver amount of isobutanol is about 800 g per hour. Using sulfuric acid as a catalyst and the distillation vessel 11, about 828 g of crude ester per hour are then distilled by piping with removal of the device 15 formed during the reaction. The alcohol distilled off at the hourly water, markedly withdrawn distillation residue, which is characterized by the fact that it is withdrawn from the column individually or in the drain valve 14, is 38 g. Mixture of the reactants and a maximum of the crude ester withdrawn from line 17 contains 0.02 percent by weight sulfuric acid, based on no sulfuric acid, is colorless and clear and the mixture that feeds has the following composition: ²⁵ reaction mixture in one with the column Isobutyl propionate 77.0 percent by weight connected, with a distillation device T _cri t., ₁₊ " _ri " i O ₁ ς see and at least the boiling temperature Propionic acid 0 5 esters held vessel collecting the Water ^ ¹ Q "sulfuric acid-free crude ester from the distillation '"' ³ ° vessel withdraws in vapor form and the esterification With the fine distillation it leaves no residue at the bottom of the vessel continuously stood on high-boiling by-products. drains. 1 sheet of drawings © 709506/427 4.57