DE2154387A1 - Process for the preparation of uncolored esters - Google Patents

Description

dr. W. Schalk dipl.-ing. P. Wirth- dipl-ing. G. Dannenberc DR. V. SCH M I ED-KOWARZ I K DR.P. WEINHOLD DR. D. GUDEL

6 PRANKFORT AM

GR. ESCHENHEIMER STRASSE 39

3K / EK 12SÖ / 7D - [115E / 71} LJgine Kuhlmann S..A ..

10 R you practice! Genera! Paris, France

Process for the preparation of -arnngsf ^ ariitar esters

The present invention relates to an improved process for the production of uncolored esters, which in particular can be used as _a non-natural product.

These esters are grounded in the known manner from mono- or polycarboxylic acids and -anhydrides, such as phthalic, sebacic, adipic acid, etc., and alcohols with up to to 20 hydrocarbons, preferably primary C ^, to C ^ alcohols, erhalran. The structure of the esters obtained in this way can correspond to the nature of the starting materials and the manufacturing process can be very complex. The esterification reaction is usually catalyzed by acids, especially strong acids, v / ie sulfuric acid, p-toluenesulfonic acid, etc.

One works by adding a substance with low to the reaction medium Adds boiling point which the water can remove by forming an azeotrope, win e.g. hexane, benzene; if appropriate, the alcohol used for esterification can be used even be used if his leagues qualify for the z «.. issssr.

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The esterification leads, especially if the catalyst is a strong acid, «De sulfuric acid, is to discolored products that are used to produce clearer and lighter, softer masses are unsuitable.

To reduce the discoloration, attempts were made to apply to the various dis To act esterification-determining parameters. In particular, it was proposed:

the use of a large excess of alcohol in relation to the acid or anhydride used;

reducing the amount of acid catalyst; the reduction in the esterification temperature;

avoiding a prolonged reaction beyond the normal time

by respective limitation of the conversion value;

the use of catalysts with a weak oxidizing power, such as p-toluenesulfonic acid;

The use of additives such as copper chloride, formamide, acetamide, potassium

tetrahydroboride; and

carrying out the reaction under an inert atmosphere (nitrogen, co).

The ester produced can also be subjected to a final decolorization treatment subject. The ester can be mixed with ozone, potassium permanganate, sodium bisulfite, Activated carbon or absorbent soils.

ORIGINAL INSPECTED 2 0 9 8 2 7/1 1 U

_ 3 -

In another, described in French patent specification 1,055,454 Process one achieves the discoloration and improvement of the thermal Stability of the plasticizers through a hydrogenation treatment at elevated temperatures and pressures in the presence of a nickel catalyst. The addition 63 620 for the French patent specification 1 055 454 shows the decisive one Role of the catalyst, and the description illustrates certain advantageous ones Method by using copper instead of nickel. The main patent specification mentions, among other things, that excellent results are obtained, when considering the catalytic hydrogenation treatment in the course of manufacture applied to a mixture.

All of these methods, regardless of their mode of operation, are unsatisfactory and make further investigations necessary. ..... '

In addition, the impurities that lead to discoloration of the ester can be introduced by the reactants. In particular the presence of carbonyl or ethylenic groups in trace amounts in the used Alcohols lead to discoloration. These impurities can also form in the course of the esterification. For example, oil hydrocarbons can be used form by dehydration of alcohols; the acidic catalyst reacts with certain of these olefins and gives colored products.

It is therefore advantageous to neutralize the impurities present in the starting materials or their formation in the course of the reaction.

Surprisingly, it was found that there were significant improvements Results are achieved when the reaction medium in which the esterification

takes place,
/ from the moment the medium is mixed by the reactants

is formed until the end of the esterification of a catalytic

subject to lytic hycration treatment and as a catalyst under

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-A-

certain working conditions a metal of the platinum series, especially platinum or palladium is used.

The aim of the present invention is therefore a process for the production of uncolored Esters, which can be used in particular as plasticizers, by reacting at least one alcohol and a mono- or polycarboxylic acid or an anhydride in a hydrogenation medium and in the presence of one Hydrogenation catalyst, which is characterized in that the hydrogenation treatment from the moment the reactants come into contact are brought and carried out during the entire esterification process,

(Period) that a hydrogenation catalyst from the 5th and 6th series / the elements of Group VIII of the Periodic Table and the reaction practically table at atmospheric pressure.

The active element of the catalyst used in the present invention is a metal of the platinum series, such as platinum or palladium on an inert carrier applied the type commonly used for hydrogenation catalysts is. Suitable carriers are e.g. activated carbon, strongly calcined clay, silica, Barium sulfate and other carriers which are inert in the reaction medium.

. The amounts of the catalytic metal are around 0.1 g / kg, based on the weight of the reaction mixture; according to the invention, they are completely sufficient and, for economic reasons, the catalyst weight does not need to be increased above the stated fourth.

The main advantages of using the catalysts of the invention, in particular of the catalysts based on platinum or palladium are:

- 4a -

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(ΐ) Qer catalyst is not going to catalyze through the in the mixture Strong acids such as sulfuric acid introduced during the esterification reaction are attacked. One can thus use strong acids or very active and economical ones Use advantageous proton donors from the standpoint.

(2) The hydrogenation reaction occurs at atmospheric and not superatmospheric Pressure, which simplifies the device and reduces costs brings with it. Uit the catalysts based on NicteL or copper pressure of 10-25 kg / cm was necessary in practice.

(3) The complete absence of side effects (e.g. hydrogenation of benzene - kernes in the case of phthalates) allows working under conditions at which esterification is faster; the elevated temperature goes up to the reflux temperature of the alcohol at atmospheric pressure and one works with a strong concentration of sulfuric acid. With nickel or copper catalysts the maximum temperature that can be used in practice was not more than 140 ° C.

(4) The amount of catalyst used is very small (0.1 g / kg) while with Nickel or copper this amount necessarily reached 200 g / kg. This feature is essential because the catalyst must be separated from the ester product after treatment.

(5) In many cases, the catalyst can be reused without regeneration; this simplifies the separation of the catalyst after the reaction, so that part of the ester can be recycled with the catalyst. In contrast for this purpose, under the working conditions preferred according to the invention, it is impossible to use the nickel or copper catalysts again, since they are used during attacked in response.

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(ö) As a reaction participant, one can use impure alcohols, such as those found in common Use alcohols that remain after esterification. Furthermore, only a small excess of alcohol needs to be used.

(7) The esterification time can be determined without any noticeable change in color lengthen to achieve significantly increased conversions.

(B) It is only necessary to use a small amount of hydrogen, only ensuring that there is intimate contact between the hydrogen and the esterification mixture. This is done with any suitable means to bring the gaseous hydrogen with the liquid mixture, which is kept under stirring% and contains solid particles of the metal catalyst on a support in contact. A simple measure consists in the introduction of hydrogen into the reaction medium, the hydrogen being introduced through a tube extending into the medium.

(9) The esters obtained by the process according to the invention are according to simple, usual after-treatments thermally stable.

The following examples illustrate the present invention without it to restrict. »· '

Example 1

"This example is done by a known process (without hydrogenation)

conducted comparison test.

The phthalates of the following alcohols were successively produced were selected because of their poor quality:

~ ° 7-Β-9

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These were in an electrically heated, with Dean-Stark trap, cooler and Stirrer-equipped reactor introduced the following materials: 1 mol

as

Phthalic anhydride, 2 mol alcohols excess of 5 ^c / o, 0.5% sulfuric acid, based on the total weight of anhydride and alcohol, and an entrainer for water, such as heptane or benzene.

The temperature was brought to 135 ° C. with stirring and by regulation of the imported water entrainer (a variable according to Art of the treated alcohol) is kept at this value. The esterification took 3 hours. The water was extracted as it was formed.

After the procedure was completed, the reactor was cooled to room temperature. The APHA coloration of the crude phthalate was measured in accordance with ASTM 1209 and the residual acidity was determined by titration.

The results of these measurements are shown in Table 1 below;

Alconol esters

^C 8

^C 10 ^C 13 ° 7-8 ^C B-9 ^C 7-8-9 " ^C 9-10-11

* ~ Acidity index Mg KOH / g

Table 1 ¹ A * APHA staining residual acid;
Milliequivalents
per kg 1.96 500 35 2.35 350 42 2.24 150 40 1.90 500 34 2.07 175 37 2.24 400 40 2.24 250 40

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example

Example 1 was repeated, except that at the beginning of the experiment, reactor 0, Co g of palladium on a pulverized barium sulfate carrier and hydrogen in bubbles by means of a tube immersed in the reaction medium let through. After completion of the reaction, the metal catalyst was from

separated crude ester by filtration.

The measurement results are listed in the following table 2:

Table 2 alcohol esters

^C 7-8

^C 8-9

^C 7-8-9

^C 9-10-11

example

residual acid; milli-
equivalents per kg ¹ A APHA discoloration of the
Esters 33 - 1.85 5 26th 1.45 10 40 '2.24 5 35 1.96 5 35 1.96 5 40 2.24 5 40 2.24 5

Example 2 was repeated with the same mixture of C _{Q o} alcohols, the temperatures being based on three successive experiments 3a, 3b and 3c

135 ° C. _f 150 ° C. and 170 ° C. were brought.

The test results with the raw star are shown in the following table 3:

Table 3

Vers. Temp.; ° C. residual acid; milli-

equivalents per kg

APHA discoloration of the ester

3a 135
3b 150
3c 17Ü

56 57 53

3.14
3.19
2.97

5 5 5

q ■ -.) '7 / ι -ι ι

Example 4_

Example 2 was repeated with the same Coo alcohol mixture, but with an excess of alcohol was introduced in the three modified experiments Yi 4a, 4b and 4c. Conditions and test results are in the following Table 4 listed:

Table 4

Verse. Alcohol excess
shot; ⁰ yo residual acid; milli-
equivalents per kg 5 ¹ A APHA discoloration of the
Esters 4a 5 56 3.15 5 4b 2.5 55 3, OB 5 4c 1 65 3.64 5 at s ρ i el

Example 2 was repeated with the same Cqq alcohol mixture, with Experiments 5a and 5b the esterification time was modified. Working conditions and results are shown in Table 5 below:

Table 5

Vers. Esterification residual acid; Milli- τ APHA discoloration of the

equivalents per kg of A ester

2.24 5 0.5 15

Example 2 was made with the same Co_g alcohol mixture at a temperature of 150 C. and repeated with an esterification time of 2 hours. The catalyst was separated by decantation or centrifugation and reappeared without regeneration in a series of 45 consecutive attempts used. The results are shown in Table 6 below:

duration j std ClL) U 6th 40 5a 3 9 5b 8th B e i s ρ i e 1

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Table 6

after trying APHA discoloration of the ester

1. 5

10. 5

20 10

30. 10

40. 10

45.10

Example 7

This example demonstrates the suitability of the method for treatmen _k development of the alcohol obtained after numerous Veresterungszyklen, the one EP ·

has a high content of color-forming impurities (derived from Carboxyl compounds, ethylenic compounds, sulfur, iron and oxygen containing compounds etc;) So were. E.g. the bad repatriation alcohol from an industrial esterification plant used to produce corresponding data for the method of operation according to Example 1 (experiment 1) and for the method of operation according to Example 2 (according to the invention; Experiment 2). The results are shown in Table 7 below:

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Table 7

Alcohol used number d.Koh- APHA lenstoffatame coloring

Esterification conditions

according to Belsp. 1 duration or 2 hours

^u 7-6-9 mainly branched - kuttig

40

huuptsächl. ruler ^

1 2 remaining acidity, milli eqii / alents per k g

APHA staining of the
raw ester

5 30th 1
2 3
3.5 58
53 3.25
2.97 2400
5 C ₇ 100 1
2 3
3.5 53
55 2.97
3, ÜÜ 2500
40 B5 1
2 3
4.5 ai
55 4.54
3, oa 600
70 ^C 9 GO 1
2 3
4.5 71
57 3.97
3.19 800
15th Ii ' ¹ 20th 1
2 3
7th 115
73 6.44
4.09 '400
40 ^ι Ί3 10 1
2 3 ■
2.75 70
53 3.92
2.97 800
5

3 54 2.3 4000 3 43 3.02 5 3 54 2.41 2400 2.75 3.02 5

Claims (1)

Claims 1, - Process for the production of undyed esters, in particular usable as plasticizers, by reaction of at least one alcohol and a mono- or polycarboxylic acid or anhydride in a hydrogenation medium and in the presence of a hydrogenation catalyst, characterized in that the curing treatment is started from the point in time , on which ^ _n brings the reactants into contact, carried out and continued throughout the esterification, using a hydrogenation catalyst composed of elements of the 5th and 6th series (period) of Group VIII of the Periodic Table and carrying out the reaction at practically atmospheric pressure . 2. - Method according to claim 1, characterized in that the active element of the hydrogenation catalyst is platinum or palladium. 3.- The method according to claim 1 and 2, characterized in that the catalyst in conjunction with an inert carrier, particularly in powdered form Shape, is used. 4. - Method according to claim 1 to 3, characterized in that the amount of the catalytic metal at about 0.1 g / kg, based on the weight of the Reaction mixture, lies. 5, - Process according to claim 1 to 4, characterized in that the esterification under severe reaction conditions, especially at increased speed, performs. 6, - Method according to claim 1 to 5, characterized in that one in known Way uses an esterification catalyst, which can be a strong acid such as sulfuric acid. 2 0 9 8 2 7/1 1 1 Λ ? .— Method according to claims 1 to 6, characterized in that it has been proven that impure alcohols, vde they are recycled from the esterification reaction Alcohols with an increased content of color-forming impurities are used. 8, - The method according to claim 1 to 7, characterized in that the Hydrogenation catalyst reused in successive processes without intermediate regeneration. 9. The use of the esters prepared according to claims 1 to 8 as plasticizers. The patent attorney: 209827 / 11U