DE2335307A1 - METHOD OF MANUFACTURING ESTERS - Google Patents

Description

PATENT FANWALTS & ÜRO TlEDTKE - BüHLlNG - KlNNE

TEL. (0811) 539653-56 TELEX: 524845 tipat CABLE ADDRESS: Germaniapatent Munich

8000 Munich 2

Bavar! Arlng4 n. _Ju ii ₁₉₇₃ P.O. Box 202403 q ο q CO Π "7

B 5 * 97

Imperial Chemical Industries Limited Londor (Great Britain)

Process for the production of esters

The invention relates to an esterification process and, more particularly, to a process for the esterification of high boiling points organic acids with volatile alcohols.

Standard methods of esterification include heating an alcohol with an organic acid, usually in Presence of an esterification catalyst, for example an inorganic acid or its acid salt. In the case of volatile Alcohols make it difficult for the reaction to progress to completion because of their relatively low levels Temperature at which a mixture of the alcohol and an organic acid will boil and because of the difficulty of removal of the water formed in the reaction. In the case of dicarboxylic acids, for example, the product often contains

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Deutsche Bank (Munich) Account 51/81070 Dresdner Bank (Munich) Account 3939844 Postscheck {Munich) Account 87043-804

borrowed proportions of monoester, so that a further esterification stage is required to obtain the diester. There are Various tools have been used to overcome these difficulties. For example, a large excess of alcohol can occur may be used, however, it is economically undesirable or a substantial amount of one can be used Dehydrating agents such as concentrated sulfuric acid are present be, but this brings difficulties in the work-up procedure with it, since alkali washes are required with the resulting risk of hydrolysis of the esters. In some cases it can be a liquid, especially one Volatile hydrocarbons, such as benzene, can be added to form an azeotrope with the water formed during the esterification to form or to form an entrainment agent for the water formed during the esterification, which then by distillation Will get removed. However, this method does not work in the case of methanol because its boiling point is too low.

A method has been found, which essentially a complete esterification of high-boiling organic Acids with volatile alcohols when carried out in one stage.

The invention relates to a process for the preparation of esters of high-boiling or non-volatile organic compounds Acids with volatile alcohols, which consists in the

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Alcohol in liquid or vapor form in the heated organic Acid in liquid form containing an esterification catalyst, initiate and water formed during the esterification from the reaction mixture in vapor form together with to remove excess alcohol vapor, but with volatilized Ester is returned to the reaction mixture until the organic acid is substantially fully esterified and the reaction mixture is substantially free of water and Alcohol is.

A high-boiling or non-volatile organic acid is understood in particular to be one that is not boils below 2OO ° C at atmospheric pressure. Too non-volatile Acids include those that do not boil before they begin to decompose when heated. Particularly suitable organic acids are carboxylic acids and in particular dicarboxylic acids and other polycarboxylic acids, as well as monocarboxylic acids relatively high molecular weight. The dicarboxylic acids include aliphatic, cycloaliphatic and araliphatic Dicarboxylic acids. The aliphatic dicarboxylic acids include the alkanedicarboxylic acids, especially those with 3 to 12 carbon atoms, for example succinic acid, Glutaric acid, adipic acid, suberic acid, azelaic acid, sebacic acid and traumatic acid. The cycloaliphatic dicarboxylic acids include compounds such as cyclohexane-1,2-dicarboxylic acids and to the araliphatic dicarboxylic acids such compounds

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fertilize, such as pbenylene-1,2-bis-acetic acid. High boilers or Non-volatile monocarboxylic acids are in particular the higher molecular weight fatty acids, in particular those with a molecular weight higher than .200, for example the Alkanm ^ pnocarboxylic acids with at least 12 carbon atoms, in particular those with 12 to 22 carbon atoms.

A volatile alcohol is understood to mean, in particular, one which has a boiling point below 100 ° C. at atmospheric Has pressure. Such alcohols are, for example, methanol, ethanol, n-propanol and isopropanol. Methanol is of particular importance.

As the esterification catalyst, any known esterification catalyst such as one can be used inorganic acid such as sulfuric acid or phosphoric acid or their salt, for example sodium or potassium hydrogen sulfate.

To carry out the reaction, the organic acid is heated to a temperature at which it is liquid, the esterification catalyst is added and the alcohol is introduced into the liquid in liquid or vapor form. The reaction temperature is normally within the range of 70 ° to 300 ⁰ C, although a reaction temperature is preferably from 100 ° to 200 ⁰ C. The organic acid must be melted at the chosen reaction temperature, with the temperature

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likewise must not be lower than the boiling point of the alcohol at the pressure present. Although the reaction at Printing can be carried out above or below atmospheric pressure, it is an advantage of the method of the invention that it can be carried out successfully at atmospheric pressure. The reaction is carried out in such a way that that the water formed during the esterification is removed from the reaction mixture as water vapor. This will be expedient by introducing more alcohol vapor than the stoichiometric amount required for esterification and by using it reached by excess alcohol vapor to remove the water vapor. At the same time, everyone should be more volatile Esters are returned to the reaction mixture. This can be achieved, for example, by a Reflux condensers or a fractionation column connected to the reaction vessel can be provided and so on are adapted that volatilized ester is condensed and returned to the reaction mixture, but the alcohol and water vapor flow past and condensed separately. The alcohol can of course be removed from the water by appropriate means Funds can be ceded and reused.

In practice, depending on the efficiency the fractionation method escapes smaller amounts of ester, which are returned to the reaction mixture and together can be condensed with alcohol and water. It is

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possible to obtain this small amount of ester, for example by distilling off alcohol and water, e.g. in a rotary evaporator at relatively low temperatures and Pressure. The ester can then be associated with the hatred of the ester.

The reaction is continued until the esterification is essentially complete, i.e. up to at least 90% by weight the acid have been converted to the ester. At the same time, the reaction mixture should essentially be at the end of the esterification Be free of water and alcohol, i.e. until the proportion of both is less than 1% by weight.

The product in the reaction vessel is therefore essentially entirely ester and for use as such with only minor pretreatments to remove esterification catalysts and possibly smaller amounts of unesterified ones Acid suitable for use. This can be achieved, for example, by making the product a quick Subjected to distillation and the volatile ester is condensed. Alternatively, the ester product can be mixed with water or with can be washed with diluted alkali.

The process of the invention is particularly valuable for the esterification of the mixture of dicarboxylic acids which are by-produced in the production of adipic acid in the

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Obtained nitric acid oxidation of cyclohexanol or cyclohexanone is, or for the esterification of a frequently referred to as KA technical mixture of the two components. The main components of the by-product mixture are adipic acid, Glutaric acid and succinic acid, and the mixture is often referred to as AGS acid. Sales of AGS acid to the mixed diesters in question, especially the mixed dimethyl esters, is a common first step in utilizing the mixed acids. The mixed dimethyl esters of AGS acid can, for example, by fractional distillation from one another be separated. The mixed dimethyl esters are also available for conversion to other mixed esters, for example the esters with higher alcohols which can be obtained by ester interchange reactions and which can be used, for example, as a lubricant, suitable.

The invention will now be further illustrated by the following examples, in which parts and percentages are based on weight aind.

example 1

Volatile methanol was released at a rate of 24 parts per hour fed to an evaporator at 100 ° to 120 °, and the steam was directed to the bottom of a reactor containing 100 parts of AGS acid (a crude mixture, containing

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15 to 20 % adipic acid, 50 to 55 % glutaric acid and 25 to 30 % succinic acid) and 0.7 parts of concentrated sulfuric acid and was kept at 130 to 150 ⁰ G and stirred at 1000 revolutions per minute. Vapor from the reactor was passed through a reflux condenser, the jacket was kept at 100 C and then passed to a condenser in which methanol, water and small amounts of esters were condensed Product in the reactor less than 0.2 % water and a trace of methanol. The product was rapidly distilled by being passed at a rate of 50 parts per hour to a still which was kept at 140 ^° C. at a pressure of 60 mercury. A colorless distillate of mixed dimethyl esters was obtained in an overall yield of 92 % , calculated on the equivalent weight of d-ar mixed acid used as starting material. The acid equivalent was 11 mg KOH / g and the water content below 0.1%.

Example 2

Liquid methanol was pumped at a rate of 21.85 parts ie hour in an evaporator was maintained at a temperature of 100 to 120 ⁰ C and the vapor was conducted to the bottom of a reactor containing 100 parts of adipic acid (purity 99.8 %) and 0.7 parts of concentrated sulfuric acid, and kept at 160 to 180 ° C as well

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was stirred at 1000 revolutions per minute. Vapor from the reactor was passed through a column, and via the head temperature of the vapor was maintained at 80 to 105 ⁰ C. This steam was then condensed to produce methanol, water and minor amounts of esters. After condensing the methanol in this manner for 4 hours, equivalent to 87 »38 parts of methanol, the reactor product contained less than 0.2% water and a trace of methenol. The product was added to a still at a rate of 40 parts per hour , which was kept at 190 ⁰ C and a pressure of 55 nm mercury, distilled quickly. A total of 113 parts of colorless product were distilled at an overhead temperature of 148 ° C. and 4.58 parts of the product were recovered from the methanol / water / ester distillate, an overall yield of 99% calculated on the adipic acid introduced . The product had an acid equivalent of 1.16 mg KOH / g and the water content was less than 0.1 %. The methanol losses amounted to 3% »calculated on the methanol input.

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Claims (1)

Patent claims Λ j Process for the preparation of esters of high-boiling or non-volatile organic acids with volatile alcohols by heating the acid and the alcohol in the presence of an esterification catalyst, characterized in that the alcohol in liquid or vapor form is passed into the heated organic acid in liquid form and the water formed in the esterification is removed from the reaction mixture in vapor form, however, volatilized ester is returned to the reaction mixture until the organic acid is essentially fully esterified and the reaction mixture is essentially free of water and alcohol. 2, method according to claim 1, characterized in, that the reaction is carried out at atmospheric pressure. 3. The method according to claim 1 or 2, characterized in that the ester product from the catalyst by Fast distillation separates. 309885/1476