SU789501A1 - Method of purification of synthetic aliphatic carboxylic acids - Google Patents

Description

one

The invention relates to a method for the purification of organic compounds, in particular synthetic fatty carboxylic acids, which are widely used in the industry of basic organic synthesis.

Synthetic fatty carboxylic acids obtained in the industry by the oxidation of paraffinic hydrocarbons contain impurities of carbonyl compounds, mainly ketocarboxylic acids, hydroxycarboxylic acids and other compounds containing secondary and tertiary hydroxyl groups. The increasing consumer demands for the quality of carboxylic acids are forcing them to find ways to obtain and purify them from by-products.

Extraction methods are known for purifying acids from impurities by various solvents p. .

However, these methods are complex in hardware design, have low yields of useful acids due to fuzzy separation of impurities and, consequently, the formation of waste, high specific consumption of solvents. Extraction processes using organic solvents require adherence to special safety requirements. The industry seeks, where possible, to replace extraction processes with others.

5 The closest to the proposed technical essence and the achieved result is the method of purification of synthetic fatty carboxylic acids by neutralization with acid-caustic

About potassium or sodium, hydrogenation of the obtained soap at 100–200 ° C and a pressure of 7–35 atm over a nickel catalyst to reduce the carbonyl groups of impurities present to hydroxyl, dehydration of the hydrogenated soap at 200–350 ° C and 0.1– 30 atm in the presence of alumina-based dehydrating catalysts and rehydrogenation of the product with

20 100-200 ° C and 7-35 atm over a nickel catalyst. The aqueous product is acidified with mineral acid, the fatty acids are separated and purified by distillation 2.

25 The disadvantage of this method is cumbersome, since it is required to convert the fatty acids into soaps, and then again to extract acids from the soaps. The yield of purified acids is less than

30 80%.

The purpose of the invention is to simplify the process.

The goal is achieved by the fact that the method of purification of synthetic fatty carboxylic acids with the use of catalytic hydrogenation at 100–20 ° C, followed by dehydration of the product obtained at 200ZOZ and repeated catalytic hydrogenation at 100–200 s, the catalytic hydrogenation of the initial fatty acids / a As a dehydration catalyst, a catalyst containing 20% by weight of magnesium sulphate and 80% by weight of alumina is used.

The starting carboxylic acids containing carbonyl compounds or carbonyl compounds as impurities in admixture with compounds containing secondary or tertiary hydroxy groups are directly subjected to catalytic hydrogenation on nickel-containing catalysts at 150-180 ° C and a pressure of 20-50 atm to convert carbonyl groups into hydroxyl groups (ketones and aldehydes into alcohols, keto acids into hydroxy acids), followed by selective dehydration, secondary hydroxy groups (with preservation of primary alcohols) on the catalyst consisting of magnesium sulphate deposited on granular active alumina at 300-360 ° C to form unsaturated compounds. In some cases, the content of unsaturated compounds in the products is desirable. If necessary, the unsaturated compounds are readily converted to hydrophilicated ones.

In the apparatus with a working mixer at 50-60 ° C, 10 kg of synthetic fatty acids (FFA) of CrCl0 fraction and 0.03 kg of nickel catalyst are suspended on kieselguhr of a fraction of 0.14-0.3 {l Through a tube lowered from the top to the bottom of the apparatus, the slurry is continuously fed from the bottom into the 1 liter hydrogenation reactor at a rate of 0.4 l / h. The hydrogenation reactor is equipped with a mega-linker, which makes 400 rpm and is electrically heated. Purification of acids with hydrogen j coming under the layer of the reaction mass is carried out at a temperature of 170 ° C and a pressure of 40 at.

The results of the hydrogenation are presented in table. one.

The hydrogenated fatty acids, together with the catalyst and hydrogen, are withdrawn from the top of the reactor, passed through a filter, where the catalyst is separated.

and fed to a separator to separate the hydrogen.

The filtration results are presented in table. 2

The fatty acids obtained after hydrogenation are supplied by a dosing pump to the dehydration reactor from above. The dehydration reactor is an electrically heated tube with a diameter of 30 1 F1 and a height of 800 mm, filled with a catalyst; the catalyst is magnesium sulfate on active alumina with a content of components of 20 and 80%, respectively. The dehydration is carried out at a volume flow rate of fatty acids O, 7 l / l cat. 4 at a flow rate of the purge gas 5 l / h. The dehydration products are withdrawn from the bottom of the reactor, a separator is passed to separate the inert gas and enter the apparatus with a stirrer to prepare a suspension with a hydrogenation catalyst.

The results of dehydration are presented in table. 3

Re-hydrogenation is carried out similarly to the original, only hydrogenation products, mine filters, enter the separator to separate the hydrogen.

The results of the rehydrogenation are presented in table. four.

The resulting saturated synthetic fatty acids C-j-Cr Q together with the catalyst are loaded into a distillation still to separate the nickel soaps.

The results of the distillation are presented in Table. five.

The yield of purified acids is 94.6%.

Qualitative indicators of products at the stages of processing are presented in Table. b, the composition of the products in the processing process in table. 7

The proposed method allows, with minimal losses (almost without loss), the purification of synthetic fatty carboxylic acids from impurities of carbonyl compounds and secondary and tertiary hydroxy groups.

The unpleasant smell disappears in the purified acids and the color is improved; such acids are more stable when stored in a heated state. It is not necessary to convert the original fatty acids into alkali metal salts for purification, thereby saving minerals, acids and alkalis. In addition, the yield of purified synthetic fatty acids is increased.

Table

Table

Acid number, mg KOH / g Essential number, mg KOH / g Iodine number, g iodine / 100

Carbonyl number, mg KOH / g

Secondary content

hydroxyl groups

(by IR spectroscopy),%

210

209 3.1

44.8 3.2 11.3 92.9 0.7

1,3

89.7

2.4 100

Table 7

Claims (2)

Claim 1. The method of purification of synthetic fatty carboxylic acids using hydrogenation at a temperature of ** 5 100 ~ 200 ° C in the presence of a hydrogenation catalyst followed by dehydration of the obtained product at a temperature of 200-350 ° C in the presence of a catalyst based on alumina and 50 catalytic hydrogenation at a temperature of 100-200 ° C, characterized in that, in order to simplify the process technology, the initial fatty acids are directly subjected to catalytic hydrogenation, and using dehydration catalyst coziness magnesium sulfate on alumina. 2. The method according to claim 1, with the fact that ·, a catalyst containing 20 wt.% Magnesium sulfate and 80 wt.% Alumina is used as a dehydration catalyst. · 'Sources of information taken into account during the examination 1. USSR Copyright Certificate No. 215381, cl. C 07 C 51/42, 10.19.62. 2. US patent No. 3413323, CL 260-413, published. 11.26.68 (prototype).