DE1162824B - Process for the production of pentaerythritol and dipentaerythritol by condensation of formaldehyde and acetaldehyde. - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Boarding school Class: C 07 c

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German class: 12 ο-5/03

M 51501 IVb / 12 ο
January 19, 1962
February 13, 1964

In the production of pentaerythritol and dipentaerythritol by condensation of formaldehyde and acetaldehyde, it has been found that using a higher molar ratio between formaldehyde and acetaldehyde a very good analytical yield, in practical terms Working up, however, in no way results in a correspondingly high analytical yield of pure pentaerythritol achieved.

Furthermore, it would be interesting and desirable for a number of reasons to be involved in the manufacture of of pentaerythritol by condensation of formaldehyde and acetaldehyde the desired product in the most concentrated form possible; this is forbidden according to the previous knowledge in practice by itself, since the analytical yield can be good, but the attempt, the pentaerythritol isolating from solution consistently gives poor results. It also results in both when working with higher concentrations as well as a high excess of formaldehyde Product of inferior quality and lower melting point, so that attempts in this direction namely, to obtain the highest possible concentration of pentaerythritol thrite solution was not worthwhile, although it was Advantages of such a procedure would be impressive; because a much smaller apparatus - both for condensation like the abortion of formaldehyde - and a very heavy weight Falling steam savings are advantages that should be exploited for economic reasons were.

This problem has been taken up and whether there is a bridge between these disadvantages has been investigated there, which could be the reason to remedy them.

The decisive finding was that the decrease in the yield of pure isolated product on the one hand and the deterioration of the product on the other hand when working with more concentrated Solutions or higher molecular weight ratios have a certain interdependence demonstrate; also revealed the investigation of the cause that led to the discrepancy between the analytical and real yield leads to the fact that in this process a particularly high proportion of by-products accrues, in which it is almost exclusively formaldehyde acetals of pentaerythritol and in small amounts Amounts of dipentaerythritol is what - as it is known per se - in pentaerythritol or dipentaerythritol and formaldehyde can be split.

From this the inventive knowledge was drawn that the obvious view that one must use the Ent process for the production of pentaerythritol and dipentaerythritol by condensation of formaldehyde and acetaldehyde

Applicant:

Company Josef Meissner,

Cologne-Bayenthal, Bayenthalgürtel 16-20

Named as inventor:

Dr. Karl Wilhelm Zwenger, Köhi-Marienburg - -

Avoid standing of these pentaerythritol formaldehyde acetals as much as possible in their opposite can be transformed if one consciously uses such processes in the production of pentaerythritol uses, in which a lot of formaldehyde acetals of pentaerythritol are formed, and these then in pentaerythritol converts. We have found that a high content of pentaerythritol formaldehyde acetals is always present when the total yield of pentaerythritol and pentaerythritol formaldehyde acetals is high.

This gave the opportunity to deal with the consequences described at the beginning, which were previously perceived as disadvantages To convert measures into advantages, namely a higher overall yield of pentaerythritol, and this also practically completely free of by-products of the type such as pentaerythritol formaldehyde acetals keep, also to be able to work with smaller equipment and a significant energy saving to achieve.

The present invention consists in the fact that pentaerythritol in the course of the process on various Way is obtained, in a manner known per se, first directly as a condensation product with pentaerythritol formaldehyde acetals and additionally as a cleavage product of pentaerythritol formaldehyde acetals, those condensation conditions being used which are irrespective of a high Direct yield of pentaerythritol, yes, accepting a lower direct yield of pentaerythritol, provide the highest possible proportion of pentaerythritol and pentaerythritol formaldehyde acetals, so that after the cleavage, the total yield of pure, ie formaldehyde-acetal-free, pentaerythritol is essential is increased or about 90% and above.

409 508/443

This procedure becomes economically interesting. These and other features of the invention go

already with pentaerythritol condensation solutions with from the diagram shown in the drawing a content of 5 mole percent of bound and the examples given below. Formaldehyde, but more interesting for pentaerythritol- Because of the variety of pentaerythritol condensate

Condensation solutions with a content of 7.5 mol- 5 cation resulting Pentaerythrhformaldehydaeetele percent and above of bound formaldehyde. is intended to be the analytical determination of the bound Under bound formaldehyde, the pentaery formaldehyde is used as the basis for calculation, Thrite and dipentaerythritol bound like an acetal - The diagram shown reveals the dependency

To understand aldehyde, here with condensation of the amount of pentaerythritol formaldehyde solutions formed expressed in mole percent per mole of one-io acetals per mole of acetaldehyde from the increase in the set acetaldehyde or, in the case of solids, in the molar ratio of formaldehyde to acetaldehyde of one percent by weight bound formaldehyde. on the one hand and the concentration of water on the other;

With such a procedure, the mole percentage is obtained on the ordinate initially a lower direct yield of pentaery to bound formaldehyde (100 mol percent = 30 g thrit, but this disadvantage is caused by the 15 formaldehyde) per mole of acetaldehyde and on the Invention, the abscissa downstream of the manufacturing process is the molar volume (i.e. volume per Graiam cleavage process not only balanced again, but moles of acetaldehyde) applied, there will be a higher overall yield of isolatable This diagram shows that on the one hand.

Pentaerythritol achieved, as was the case up to now, with a decreasing water content or with an increasing amount of kesder This way was possible because such a procedure a 20 concentration of the content of Pentaerythritfonmaide · - provides additional yield of pure pentaerythritol. hydacetalen increases, e.g. B. in a single Micbes

In order to achieve these advantages, one can use an increased concentration of the reaction mixture work, for example between 50 and 80% water and / and a higher molar ratio between formaldehyde and acetaldehyde, about 5 to 8: 1 and above, inevitably reducing the direct yield of pentaerythritol, but an increase in the pentaerythritol-formaldehyde acetal proportions occurs, so that the decrease the direct yield of pentaerythritol by increasing the content of pentaerythritol formaldehyde acetals is overcompensated.

It should be recognized that proposals have already been made in the manufacture of pentaerythritol or other higher alcohols from a more concentrated solution or the molar ratio by 4: 1, however, these procedures were used

Molar ratio 6: 1 formaldehyde to acetaldehyde:

at a molar volume of 1600

= 11.3 percent by weight of bound formaldehyde,

at a molar volume of 1300
= 15.1 Met- of bound formaldehyde

percent,
at a molar volume of 1100

= 17.3 mol of bound formaldehyde

percent,
at molar volume 750

= 25.7 mol percent of bound formaldehyde.

On the other hand, it can be seen that with a constant molar volume, but with an increasing molar ratio

always accepting the formaldehyde to acetaldehyde caused by this, the pentaery content. and the disadvantages outlined above. thritformaldehyde acetals also increases, 2. B,

The conversion of the pentaerythritol formaldehyde- 40 molar volume 1100 cm *: acetals into pentaerythritol can take place differently
walk. The excess is first distilled
Formaldehyde off, acidifies the solution containing the pentaerythritol formaldehyde acetals and undergoes
this a cleavage process in which the pentaery 45
thritformaldehyde acetals are broken down into formaldehyde and pentaerythritol.

But it is also possible to drive off the formaldehyde, to add the practically aldehyde-free solution
concentrate and then the pentaerythritol 50
split formaldehyde acetals; it is also possible
the formaldehyde-containing pentaerythritol in the usual
Isolate species by crystallization and then
to subject the cleavage process and to cleave the pentaerythritol formaldehyde acetals in the mother liquors to 55 either by increasing the molar ratio and thereby gain additional yield of isolable formaldehyde to acetaldehyde or increasing the barem pentaerythritol.

The processes according to the invention can be carried out either continuously or batchwise will. In the continuous process, however, the overall yield is somewhat higher than in the batch process.

The cleavage of the pentaerythritol formaldehyde acetals is possible in different ways. At the

Molar ratio 5: 1

= 11.9 mol percent of bound formaldehyde,

Molar ratio 5.5; 1
= 14.2 mol of bound formaldehyde

percent,
6: 1 molar ratio

= 17.3 mol percent of bound formaldehyde,
Molar ratio 8; 1

= 27.0 mol percent of bound formaldehyde.

The teaching given by the invention lets you see

Concentration, but to a particularly high degree achieve 1 combination of these two possibilities.

example 1

In a reaction vessel of 1 l capacity, which is provided with stirring and cooling, was a pro Hour continuously in a steady stream

Ants but also vinegar are best for this, 65 -dosed: 28.6 kg 30 weight percent formaldehyde, Oxalic, benzoic or benzenesulfonic acids or acids 1.62 kg 98 weight percent acetaldehyde, 3.85 kg with these water, which is similar in terms of splitting, and 7.61: 5, .68xnolar sodium hydroxide solution (Moiver properties. ratio 1: 8, Molyolumen 1100

The condensation can be carried out in one, but also in several vessels; in the present example two downstream vessels of the same type were used.

The temperature in both reaction vessels was kept at 42 ° C.

With the above dosage of 40 liters per hour, the residence time per reactor was ₂ ^{minutes per 1} ½ minutes.

After the second reaction vessel, the solution ran through a coil of polyethylene pipes 70 m long and 15 mm inside. The temperature was maintained at 45 ⁰ C. The residence time in the queue was 18Va minutes.

After leaving the queue, the solution passed a mixing vessel in which it was added neutralized or weakly acidified by acid (formic acid) (pH 5 to 6.5).

This solution contained 4.55 kg per hour of a mixture of pentaerythritol, pentaerythritol formaldehyde acetals and dipentaerythritol, corresponding to an overall yield of 93%. based on the used Acetaldehyde; this contained 13 mol percent bound formaldehyde.

It was then removed from excess formaldehyde by steam distillation under pressure freed.

The pentaerythritol condensation solution freed from formaldehyde was then acidified (Formic acid) brought to a pH of 3.8 and then a cleavage process in a tray column subject. For this purpose, 60 liters of solution were added every hour at the top of the column, while one at the same time passed directly through 12 kg of steam of 15atü. At the bottom of the column, the now practically freed from bound formaldehyde Pentaerythritol solution removed, while at the top of the column about 12 kg per hour of a formaldehyde / steam mixture were discharged.

The pentaerythritol can be obtained in pure form from the column bottom product together with dipentaerythritol Gain shape.

The solution flowing out of the column contained - based on the acetaldehyde used - 90% pure pentaerythritol and about 2% dipentaerythritol and practically no bound formaldehyde.

Example2

An aqueous solution prepared from crude pentaerythritol containing 143 g of crude pentaerythritol with 1.7% bound Formaldehyde and 4 g dipentaerythritol per liter, was using formic acid on a Brought pH of 4.0 and then subjected to a cleavage process in a tray column. These were at the top of the column every hour 501 solution, while at the same time from the bottom 12 to 15 kg of steam of 15 atü passed through. At the bottom of the column was that of pentaerythritol formaldehyde acetals largely freed pentaerythritol solution collected, while hourly at the top of the column about 14 kg of a formaldehyde-water vapor mixture were removed.

The analysis of the pentaerythritol freed from pentaerythritol formaldehyde acetals gave a content of bound formaldehyde of only 0.04% and a pentaerythritol of 96.8% purity with a 2.73% dipentaerythritol content.

Example 3

A higher concentration is used when an aqueous solution prepared from crude pentaerythritol g pentaerythritol with 1.7% bound formaldehyde and 12 g dipentaerythritol per liter. she was brought to a pH of 4.0 by means of formic acid and then in a tray column the Subject to division. Then proceed as in Example 2.

The analysis of the pentaerythritol formaldehyde acetals freed from pentaerythritol gave a content of bound formaldehyde of only 0.04% and a pentaerythritol of 96.8% purity with a 2.73% dipentaerythritol content.

Claims (6)

Patent claims: 1. Process for the production of pentaerythritol and dipentaerythritol by condensation of Formaldehyde and acetaldehyde, being a mixture of pentaerythritol, dipentaerythritol and formaldehyde acetals is obtained and then converted the formaldehyde acetals into pentaerythritol are, characterized in that the condensation promotes the formation of formaldehyde acetals known conditions, e.g. B. high concentration of the reaction mixture and / or high formaldehyde excess, is carried out, so that the largest possible overall yield Pentaerythritol, dipentaerythritol and formaldehyde acetals is obtained. 2. The method according to claim 1, characterized in that at a concentration of the reaction mixture 50 to 80% water is used. 3. The method according to any one of claims 1 or 2, characterized in that with a higher Molar ratio of formaldehyde to acetaldehyde is worked as 5: 1. 4. The method according to any one of claims 1 to 3, characterized in that the excess Formaldehyde distilled off after the condensation, containing the pentaerythritol formaldehyde acetals Solution acidified and this is subjected to the cleavage process in which the pentaerythritol formaldehyde acetals can be broken down into pure pentaerythritol and formaldehyde. 5. The method according to any one of claims 1 to 3, characterized in that the practically aldehyde-free Solution is concentrated and then the pentaerythritol formaldehyde acetals are cleaved. 6. The method according to any one of claims 1 to 3, characterized in that the cleavage only takes place after the isolation of the crude pentaerythritol. Considered publications:
German Patent No. 919 889;
German Auslegeschrift No. 1034 611;
U.S. Patent No. 2,629,746. 1 sheet of drawings 409 508/443 2.64 © Bundesdruckerei Berlin