CZ328491A3 - process for preparing industrial 2-ethylhexanoic acid - Google Patents

Abstract

A process of preparing industrial 2-ethylhexanoic acid by oxidation of 2-ethylhexanol and/or 2-ethylhexanol by air or gas containing 5 to 40 % by weight of oxygen in the presence of 0.01 to 0.15 mol/l of alkaline or cobalt salts of lower fatty acid with two to ten carbon atoms in a chain, at a temperature of 30 to 100 degrees C. Oxidation is subjected to a fraction boiling at a maximum of 154 degrees C from the distillation of hydrogenate in the process of preparing 2-ethylhexanol and oxidation takes place in the presence of 0.1 to 15 % by weight of water, related to the total mass of the mixture.

Description

Process for preparing industrial 2-ethylhexanoic acid

Technical field

2-Ethylhexanoic acid is used in many special industrial organic chemistry applications and related fields. Its esters are used, for example, in cosmetics or as special lubricants or as additives for plastics. High purity acid prepared from pure raw materials is needed for this purpose. Much of the 2-ethylhexanoic acid is processed into salts used eg in the paint industry. Cobalt (II) salt of 2-ethylhexanoic acid is used as a catalytic precursor of carbonylation reactions.

BACKGROUND OF THE INVENTION

2-Ethylhexanoic acid by methods. The first is the oxidation of 2-ethylhexanal, which is produced in principle by two

2-ethylhexanol, the second oxidation obtained by aldolization of butanol and selective hydrogenation of the initially formed 2-ethyl 1-2-rhexanal. Oxidation of 2-ethylhexanol is usually carried out in an alkali hydroxide melt (Pat. NDR 226875, 1986) or under vigorous conditions with oxygen usually containing ozone (USSR 557566, 1977). optionally electrochemically (USSR 1177288, 1985). However, all these syntheses are energy intensive and mostly high temperatures, sometimes at higher pressure.

At atmospheric pressure and catalysis of cobaltic acid (Čechina et al .: Neichimimia

2-ethylhexanol, characterized by fairly extending beyond the fatty salt

1984, 24, 63) is a long induction period of oxidation

(up to several hours), which is somewhat shortened by increasing the cobalt concentration, but not completely removed. To achieve a satisfactory reaction rate, higher temperatures (at least 90 ° C) are required at which cobalt and some other metals catalyze the formation of 2-ethylhexanoic acid esters by the biscuit reaction and thereby impair the selectivity of the oxidation.

Oxidation of 2-ethylhexanal is carried out mostly in the liquid phase at low pressure and temperatures. The catalysts are usually salts of manganese (J. Appl. Chem. 20, 274, 1970) or other heavier metals (Jap. Kokkai 7522017, 1975). The use of alkali metal or alkaline earth metal formates as catalysts is also known. Alone

However, 2-ethylhexanal is a rather expensive raw material because it has to be obtained in a technically demanding way - selective hydrogenation

2-ethyl-2-hexenal.

SUMMARY OF THE INVENTION

The process according to the invention provides economic advantages over the cited procedures. In accordance with the process of the present invention, it is possible to obtain, in accordance with the present invention, 2-ethylhexanoic acid technical grade in a quality suitable for some applications even from less expensive feedstock.

Process for the preparation of 2-ethylhexanal Q of the technical acid O 2-ethylhexanol

% 2-ethylhexane by air or by oxidation with a gas containing 5 to 40 wt. of oxygen in the presence of 0-10 to 0.15 moles of an alkali or cobalt salt of a lower fatty acid having two to ten carbon atoms in the chain at a temperature of 30 to 100 ° C according to the invention consists in subjecting the oxidation to fractions boiling at most 154C from the distillation of hydrogenate in the 2-ethylhexanol production and oxidation process is carried out in the presence of 0.1 to 15 wt. water, based on the total weight of the mixture.

Thus, 2-ethylhexanoic acid is obtained by oxidation of the waste low-boiling fraction obtained by distillation of the crude hydrogenation product in the process of producing 2-ethylhexanol by hydrogenation.

2-ethyl-2-hexanal, which is commonly part of the oxo-synthesis units. This fraction contains acid oxidizable components

2-ethylhexane, i.e. 2-ethylhexanal and 2-ethylhexanol. Butanol and 2-methylpropanol are present as further major components. Surprisingly, it has now been found that this fraction can be oxidized at a satisfactory rate and high acid yield under mild conditions with air or other mixed gas containing 5 to 40 vol% oxygen in the presence of alkali or cobalt salts of lower fatty acids and a small amount of water. This catalytic system effectively eliminates the initial induction period that is common in oxidation of a similar type.

According to the process of the invention, 2-ethylhexanoic acid can be prepared from said waste fraction with satisfactory selectivity by suppressing the formation of higher-boiling products, especially esters. The process according to the invention makes it possible to utilize a multi-component waste mixture containing inter alia. C4 oxygen compounds, in particular butanol, without significant formation of lower fatty acids, so that the resulting solution of 2-ethylhexanoic acid can be used directly without purification for some technical applications such as the preparation of metal soaps and the like.

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The oxidation product is a solution of 2-ethylhexanoic acid in a mixed solvent consisting mainly of butanols and 2-ethylhexanol. In this form, it is readily applicable to certain technical applications, eg for the preparation of metal soaps or cobalt (II) 2-ethylhexanoate solution, which is useful as a catalyst precursor for hydroformylating olefins or other types of carbonylation reactions. This also belongs to the advantages of the process according to the invention.

The process of the present invention is illustrated in more detail by the following examples.

DETAILED DESCRIPTION OF THE INVENTION

Example 1

The oxidation of the light fractions from the distillation of 2-ethylhexanol was carried out in a vertical glass column without packing, internal diameter 50 mm, 2 m high. The column had a double jacket (duplicator) and was equipped with a reflux condenser. At the bottom of the column was an ore, which served as a distributor of the supplied air. The sampling tube was sealed 15 cm above the air inlet. Water kept at the set temperature by a laboratory thermostat was circulated through the column jacket.

The column was charged with 300 ml of light distillates

2-ethylhexanol containing 30.8 wt. 2-ethylhexanal and 11.3 wt. 2-ethylhexanol. Sodium 2,8-ethyl 2-ethylhexanoate (mol ratio Na: 2-ethylhexanal = 0.283: 1) dissolved in 5.5 ml of water was then added. After tempering to 35 ° C, the air supply was started at a speed of 150 dm ³ / h. The temperature was maintained at 40 ° C during the oxidation. After 4 hours of oxidation, the product contained 31.7 wt.

% of 2-ethylhexanoic acid and 0.15 wt. C4 acids (butyric acid + isobutyric acid). The oxidation resulted in a 9.6% weight reduction due to evaporation and degradative oxidation.

The oxidation product described was used to prepare an organic solution of cobalt 2-ethylhexanoate as follows: 120 ml of the oxidation product was placed in a 2 liter flask placed in a thermostat. 236 ml of pure toluene was added. Then, 33 mL of 25 N aqueous NaOH solution was added. The mixture was heated to 80 ° C and stirred for 15 minutes, leaving most of the acid

2-ethylhexane was converted to the sodium salt. Then 81 ml of a solution containing 0.0626 moles of Co (NO 3) ₂ and 0.135 moles of nitric acid were added. The mixture was stirred for 40 minutes, then the layers were separated and the organic layer was washed at 80 ° C with a small amount of water (250 ml). 350 ml of an organic solution of cobalt 2-ethylhexanoate having a Co concentration of 8.2 g / dm ^{3 was obtained} .

The oxidation column described in Example 1 was charged with 300 ml of a low-boiling distillation fraction, the so-called light fractions from the industrial production of 2-ethylhexanol, containing 47.6% by weight. 2-ethylhexanal a

10.2 wt. 2-ethylhexanol. 3.56 g (0.0201 mol) was added in ...

cobalt acetate and 10 ml of water. The oxidation was carried out at 35 ° C with an air flow rate of 150 dm ³ / h. The oxidation product after 5 hours contained 41.3% by weight. 2-ethylhexanoic acid.

Example 3

500 ml of light fractions from the production of 2-ethylhexanol with the same content of active components as in Example 2 were fed to the column described in Example 1. 1.2 g (0.0072 mol) was added.

Sodium 2-ethylhexanoate by air (air supply clock. Product of 2-ethylhexanoic oxidation.

and 30 ml of water. The oxidation of 200 dm ³ / h) at 60 contained 44.1 was carried out ° C for 4 wt.

acid

PHklad 4

500 ml of the 2-ethylhexanol production fraction of the same composition as in Example 1 was charged to the oxidation column used in the previous examples, 2.9 g (0.035 mol) of sodium acetate and 50 ml of water were added. The oxidation at 50 ° C and the air feed rate of 160 dm ³ / h lasted 4.5 h. After this time the product contained 27.6 wt. 2-ethylhexanoic acid.

Ing.

Květuáe Petrášová οχ i dac ί

PATENT CLAIMS

Claims (2)

PATENT CLAIMS Process for preparing industrial 2-ethylhexanoic acid % Of 2-ethylhexanol of 2-ethylhexanol with air or gas containing 5 to 40 wt. oxygen in the presence of 0.01 to 0.15 lower alkali or cobalt salts of two to ten carbon atoms in the chain, at a temperature of 30 to 100 ° C, characterized in that fractions boiling up to 154 ° C from distillation are subjected to oxidation % hydrogenate in the process of producing 2-ethylhexanol and the oxidation is carried out in the presence of 0.1 to 15 wt. water, based on the total weight of the mixture. Litvínov, 7 December 1992 Ing. Květuše Petrášová ANNOTATION Process for the preparation of industrial 2-tylhexanoic acid it Process for the preparation of industrial 2-ethylhexanoic acid by oxidation 4 / nefcp / % Of 2-ethylhexanal or 2-ethylhexanol / air or a gas containing from 5 to 40% by weight of 2-ethylhexanol; for oxygen / presence of 0.01 to 0.15 mol / ^{^:;} alkaline or cobalt salts, lowering the fatty acids, with two to ten carbon atoms in the chain, at a temperature of 30 to 30 ° C. 100 ° C consists in oxidizing the irradiation with boiling; up to 154 ° C from hydrosrenate distillation in the production process 2-ethylhexanol and the oxidation is carried out in the presence of 0.1 to 15% by weight of n-iodide, based on the total weight of the residue; ’