CS233464B1 - A method of continuously producing esters - Google Patents

Abstract

Invention of a method of continuous production of esters of organic acids. The essence of the method of continuous production of esters according to the invention is to use esters with the number of carbons in the molecule from 6 to 12 from organic acids and alcohols, and that the raw materials are sucked into the esterification system, preferably as a mixture, without water and/or with an aqueous phase from the distillation of the ester in an amount of 2 to 90% by mass. water for raw materials, preferably according to the amount of water in the distillate reduced by the amount of water absorbed by ostoirrigation.

Description

233464 2

The invention encompasses a process for the continuous removal of esters of organic acids, in particular in the range of 6-12.

For the preparation of esters from organic acids and alcohols and using catalytic nocatalytic procedures (Beilstein: Handbuch dar organischen Chemie, 4th edition, tretloplnok, dlel II. 234, Springor Verlag. Berlin 1960). Both discontinuous and continuous preparation procedures are known. In the discontinuous production process, the acid / alcohol / acid catalyst mixture is metered into the column of the excess alcohol column. After one hour of refluxing with total reflection, the azeotropic distillation of the water is started so rapidly that the acid concentration in the aqueous phase exceeds 0.5% by weight. The aqueous layer is detached and organic is added as reflux to the head. Tern, water, alcohol and ester are distilled from koldny. When the water is no longer distilled, the ester is terminated and the mixture is discarded after neutralization. Continuous esterification takes place in a mixture of acid, excess alcohol, and catalyst in addition to the pool, which is generally continuous. Water is taken off as azetrop tern water, the alcohol, the ester at the top of the column, coalesces the crude ester from the bottom of the column. Crude estersa is neutralized after neutralization (German Patent Publication 2,756,748). This process is used for acids with 1 to 8 carbon atoms in the molecule and aliphatic or cycloaliphatic alcohols with 3 to 10 carbon atoms. In the meantime, the amount of heat required for the distillation of the azeotrope is coupled in one case to the vapor pressure in the column, in other cases the resulting product.

There is also a known method where regulation is made according to the amount of water produced (SSAAA Certificate 509 577). Other continually processes for the preparation of esters are acid-alcohol-consuming products. The unreacted alcohol is removed as an azeotrope alcohol ester, and the residue containing a mixture of ester, acid and water without alcohol is fractionated. (German Patent Publication No. 2,904,822). In another continuous process, the feedstock, alcohol, and acid are metered into a digester of an esterification column in which the inorganic acid is the most common sulfuric acid catalyst.

The ester formed together with water and a portion of the alcohol such as ternary is continuously distilled off. Separating the organic phase from the aqueous portion of the water aside from the refluxing of the enriching portion of the column while the organic phase is neutralized, dried and distilled to obtain a high-concentrated ester and an ester-alcohol blend. (V. V. Beregovych, V. S. Tlmofeev, O. V. Vaeiljeva, L. A. Serafimov: Chim. Prom. No 3, 189 (1973)). In the first process, i.e. by using an excess of acid to prepare ester esters, there is considerable loss of acid which is removed from the product chemically, ie by neutralization, as well as by the spinning of the column (NSR Pat. No. 2,756,748), at the second spd-eobe, ie, when using an excess of alcohol, the required portion of distilled water is, after dividing the ternary azeotrope, returned to the column so that the composition of the feed distillate does not shift. In this case, a plurality of vapor permeaters are required to be coupled to the feed column and the amount of steam required for distillation by means of control devices. This method is difficult to measure and control (USSR Certificate 451 679, V. Brit.pat. 1 438 410, USSR Certificate 619 910, 509 577).

The above drawbacks are eliminated by the continuous production of esters of the present invention, with the number of carbon atoms in the molecule of 6 to 12, of organic acids and alcohols, so that the esterification system is supplied, preferably as a mixture, with raw materials with water and / or with an aqueous phase from distillation of the ester in an amount of 2 to 90 wt. raw materials, preferably according to the amount of water in the distillate reduced by the amount of water produced by esterification 3 233464

Said method improves the overall process, since it allows precise dosing of the individual components, i.e., the maintenance of the desired ratio of components, which is independent of the variation of the total flow rate of the mixture. This system makes it possible to simplify the whole batching and regulating the flow of raw materials, thereby stabilizing the esterification process, the composition of the esterification mixture and thus ensuring stabilization of the rectification conditions of the composition of the distillate composition.

The method of preparing the raw material mixture depends on the type of acids and alcohols used. In the case of esterification of n-butanol with acetic acid, we feed both raw materials in a molar ratio close to one, e.g. 1.00 to 1.05 to one. Since the azeotropic ester mixture, water boils at 90.2 ° C and has a composition of 73.3% by weight. % ester and 26.7 wt. water, while only 13.4 wt. of water, it is necessary to add the amount of water together with raw materials, about 17 wt. in the mixture. In such a ratio, the components of the mixture, i.e., acetic acid, butanol, and water are mutually acceptable and thus can be prepared into a dispensing container and dispensed together into an esterification apparatus.

The esterification apparatus used is a conventional esterification column with a cooker in which the catalyst is an inorganic acid, most often sulfuric acid, or a mixture thereof, or other known esterification catalysts with a corrosion inhibitor and the like. Due to the fact that various iron, calcium, magnesium ions, for example in the form of salts with an acid, tend to be soluble in small amounts in raw materials, some of the acid catalyst is drained from the reaction. For these reasons, it is desirable to add a small amount of catalyst directly to the feedstock and to continuously feed it into the feed apparatus or make the feed of the catalyst periodically. If an isobutanol ester and an acetic acid ester are prepared with a lower water content in the distillate of about 20%, it is necessary to add a lower amount of water of about 7% by weight to the raw materials. In the case of the use of propyl and n-propyl alcohol, the azeotrope contains 23 wt. % water, causing only 13.4% by weight of the reaction to \ t 10% by weight of water, i.e. with raw materials. water. In the case of amyl acetate preparation, the azeotrope has a water content of 41%, i.e. 29% water is required to be injected.

Since the use of acids and alcohols with higher molecular weights is already considerably limited in water, in these cases it is necessary to ensure constant mixing of the mixture in the reservoir, e.g. by circulating the entire mixture with a powerful pump. Alternatively, in addition to the acid / alcohol mixture, the water is separately fed to the reactor, while the ratio between water and the esterification mixture must be maintained. Known measured azeotropic mixtures, i. j. with ohXad for water content is only indicative and needs to be specified for each type of raw material used.

While the mixture is added to the dispenser from pure raw materials, or from the ester separation, water is most suitably used after separation of the organic phase from the esterification product, most often distillate. A portion of the precondensate, or a suitable fraction of the further distillate ester, may be used as reflux for the chucucolones.

For the preparation of the esters of the present invention, it is suitable to use such acids and alcohols, the esters of which with water form azeotropes in which the water content is extracted as the reaction water-borne amounts. Especially esters having a carbon number of 6 to 12 are preferred. The advantages as well as the method of operation are evident from the examples which, however, do not exhaust all possible uses. 233464 4 Example

We were fed to the digester of the laboratory esterification column. a continuous mixture of acetic acid, butanol and water of 36.5% by weight, acetic acid, 46.2% by weight, butanol and 17.3% by weight. water. A 300 g 45% wt. acetic acid, 5 wt. % butanol, 13 wt. % water and 37 wt. butyl acetate. Sulfuric acid 0.5% by weight was used as the catalyst. for the shaft. The feed of the feedstock was 170 g / h, the reboiler heating was chosen so that the boiling level was constant. During the 100 h continuous period, the composition of the digester and distillate was virtually unchanged, and the distillate contained in the organic phase 90 to 95% butyl acetate, 5 to 7% of butanol, less than 0.1% by weight. % acetic acid and 1.5 wt. water. In this case, 1 g of sulfuric acid was added to the container for 4.5 kg of the mixture of powder. The water phase content of the distillate was 27.5% by weight. Example 2

The procedure of Example 1 was modified in such a way that only butanol, oetic acid and water with catalyst were pre-packed at the end of the experiment. The content of the mixture in the mixture was as follows: acetic acid 61 wt%, butanol 29 wt%, 9.8 wt%. % water and 0.2 wt. p-toluene sulfonic acid. After 30 minutes of refluxing the mixture at total reflux, we started with feedstock feed, gravity with a reservoir of constant pressure liquid at the outlet valve. The feed consisted of a 1: 1.0 molar scavenger of acetic acid and butanol. The water content of the feed was varied from 15 to 22% by weight, while the ash was used by the water-lashing agent. During the spraying, we monitored the compound and distillate. Most preferably, in terms of the stability of the individual component concentration, the water content of the feed appears to be 17 to 17.5% by weight. After dispensing 5 kg of feed, a single gram of sulfuric acid was introduced into the digester. Example 3, as in Example 1, we prepared lsobutyl acetate by esterifying isobutyl alcohol with acetic acid. A mixture of 180 g of acetic acid, 82 g of isobutyl alcohol, 6 g of water and 1 g of sulfuric acid and 0.5 g of copper (II) sulphate was added to the digester. We used a mixture of isobutyl alcohol with acetic acid in a molar ratio of 1.02 to 1.00 with the addition of 7.5% by weight. water to the shaft. Under these conditions, the distillate cooker 1 was approximately the same during the 100 h reaction, with the distillate containing about 95 wt. isobutyl acetate. To the 5 kg mixture was added 1 g of acid sulphate. Example 4

A mixture of isoamyl alcohol and propionic acid containing 68% by weight propionic acid and 32% alcohol and 0.2 wt. % p-toluenesulfonic acid as catalyst and 0.2 wt. of copper (II) sulphate as an inhibitor of kordsia. After refluxing for 1 hour under total reflux, a mixture of propionic acid and isoamyl alcohol (54.5% by weight) was not injected into the digester mixture. % of an isoamyl alcohol and a further reservoir of distillate water fuss in an amount of 72% by weight. to the injected mixture of alcohol and acid. From the top of the column, a distillate of 95-97% by weight was collected. isoamyl propionate and 2 to 5 wt. isoamylalcohol in organic phase.

Claims (1)

1. The preparation of esters, in particular esters having a carbon number of 6 to 12, from organic acids and alcohols, in the presence of acid catalysts, characterized in that the esterification system is fed to the esterification system, preferably as a mixture, with water and % or with an aqueous phase from ester distillation in an amount of 2 to 90 wt. water to feedstock, preferably by the amount of water in the distillate reduced by the amount of water produced by esterification