FI101472B - Process for the preparation of monoesters of 1,3-diols - Google Patents

Description

101472

Process for the preparation of monoesters of 1,3-diols

The present invention relates to a process according to the preamble of claim 1 for the preparation of monoesters of 1,3 to 5 diols.

According to such a method, a hydrogen-containing aldehyde in the alpha position is contacted with a basic catalyst of the general formula I

10 R1 H R1 R1

III I

H-C-C-C-CH- -O-C-C-H

III II! ω r2 oh R2 o R2 15 and Π R1 H R1, respectively

! I I

H-C-C-C-CH - OH

20 II! R2 o r2 I ai) c = o 25 for the preparation of monoesters according to Rt - ch - r2 and the corresponding 1,3-diols. In formulas I and Π I, the substituents R 1 and R 2 are the same or different and denote lower alkyl.

30

Numerous methods are known for the preparation of 1,3-glycols and their monoesters from aldehydes. The reaction usually takes place at an elevated temperature, i.e. from about 40 to about 180 ° C, in the presence of catalysts. After the reaction, unreacted aldehyde is separated from the reaction mixture and recycled. The product is typically purified by vacuum distillation. The processes can be continuous or batch processes.

Examples of prior art include the 5 solutions disclosed in U.S. Patent Nos. 3,291,821 and 4,225,726 and DE Application Nos. 3,833,033, 3,024,496 and 3,447,029. These known processes use, for example, sodium hydroxide, alkaline earth metal hydroxide, metallic tin or tin oxide as catalysts.

There are significant drawbacks to the known solutions. Thus, the heat of reaction generated by an exothermic reaction makes it difficult to control the reaction in many processes. Another important problem is that basic catalysts, e.g., sodium hydroxide, are used as dilute aqueous solutions, leaving low conversion of the starting material (e.g., processes according to U.S. Patent Nos. 3,291,821 and 4,225,726). On the other hand, the solutions I know also have problems in making the process continuous (DE application publication 3 024 496).

15

As such, a rather preferred process is described in EP-A-0 367 743, in which a two-component catalyst solution (15-40% NaOH + phase transfer catalyst) and isobutyraldehyde (isobutanal, IBAL) are fed simultaneously to the reactor. Said process can be applied to both batch reactors and continuous reactors. However, the conversion is quite low, leading to high circulating currents. In addition, the use of two catalysts makes purification of the reaction solution difficult.

GB-A-2 008 097 describes a one-step process for the preparation of 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate, in which isobutyraldehyde is introduced into an alkali metal hydroxide, after which the reaction is allowed to proceed for about an hour before the product is separated from the reaction mixture. According to the reference, the alkali metal hydroxide is used in solid form, as a concentrated aqueous solution having a concentration of at least 20% (usually 20 to 60%) or as a mixture of a solid and a concentrated aqueous solution of a solid. With this solution, the amount of water in the reaction medium can be reduced. At the same time, however, the use of a concentrated catalyst rapidly raises the temperature of the reaction medium at the beginning of the reaction and makes it difficult to control the reaction. The concentrated catalyst also decomposes the desired monoester final product into the corresponding undesired diol.

3 101472

Alkali metal hydroxides are mentioned in GB application 2,008,097 as sodium hydroxide, potassium hydroxide and lithium hydroxide. According to the publication, sodium hydroxide is the most catalytically active and economical of these hydroxides.

The object of the present invention is to obviate the drawbacks associated with the prior art and to provide a completely new process for the preparation of 1,3-glycol monoesters.

The invention is based on the surprising finding that - contrary to what is claimed in GB application-10 008 097 - lithium hydroxide is quite active as a catalyst when the aldehyde reacts with itself if it is used as a dilute aqueous mixture. By "dilute aqueous mixture" is meant an aqueous solution or suspension in which the concentration of lithium hydroxide in weight percent is less than 20%, preferably less than 15% and particularly preferably less than about 12% by weight. Lithium hydroxide has proven to be so active that no phase transfer catalysts are required in the dilute catalyst mixture, but lithium hydroxide can form the main catalyst component of the solution alone or in a mixture with at least one other alkali metal hydroxide or alkaline earth metal hydroxide.

More specifically, the method according to the invention is mainly characterized by what is set forth in the characterizing part of claim 1.

The invention provides considerable advantages. Thus, the heat production of the reaction is controlled, making the process safer. The invention increases the selectivity of the process with respect to the 1,3-glycol monoester, i.e. the conversion to the monoester is improved, thereby reducing the amounts of circulating currents. This is mainly due to the fact that lithium hy-; the hydroxide is very active as a catalyst. In addition, because the basic catalyst mixture containing hydroxyl ions is dilute, the monoester does not decompose to a significant extent into a diol. When lithium hydroxide is used in a mixture with one or more other hydroxides, sufficient conversion is obtained at a reasonable catalyst cost. No phase transfer catalyst is required.

«

The invention will now be examined in more detail with the aid of detailed description 4 101472 and a few application examples.

The invention relates to the general formulas I 5 R1 H R1 R1

lii I

H - C - C - C - CH2-O-C-C-H

II! M! ® R2 oh r2 o r2 10 and Π R1 H R1, respectively

I I I

15 H-C-C-C-CH2-OH

I I I

R2 0 R2 (II)

C = O

20 R1 - CH - R2

monoesters and the corresponding general formula HI

R1 H r1 25 III- H 'C “C - c CH2-OH (III)

I I I

r2 oh r2 30, wherein in formulas I to III R1 and R2 are the same or different and represent lower alkyl.

101472 "Lower alkyl" in the present invention preferably means a straight or branched alkyl group having 1 to 4 carbon atoms, such as methyl, ethyl, n-propyl, i-propyl, n-butyl, i-butyl or t-butyl.

Particularly preferably, 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate (TMPDMIB) is prepared, which is a monoester mixture whose components are monoesters of the formulas I and Π. In these formulas, and R 2 both represent methyl. This product is thus generally a mixture of two isomers, namely 1-hydroxy-2,2,4-trimethylpentyl-3-isobutyrate and 3-hydroxy-2,2,4-trimethylpentyl-1-isobutyrate. The product typically also contains some 2,2,4-trimethyl-1,3-pentadiol as a by-product. However, the amounts of this are lower than in products prepared according to known methods.

1,3-Glycol monoester is prepared by reacting R2 HCl of formula IV with C * O (IV)

I I

20 R1 H

aldehyde in contact with the catalyst under stirring. In formula IV, Rx and R2 have the same meaning as above. Depending on the desired end product, several different aldehydes with one alpha hydrogen atom can be used as starting materials. Examples are isobutyraldehyde (IBAL), 2-methylbutyraldehyde, 2-ethylbutyraldehyde, 2-: ethylpentaldehyde, 2-ethylhexaldehyde, 2-propylpentaldehyde, 2-propylhexaldehyde and 2-butylhexaldehyde. Isobutyraldehyde is used in the preparation of TMPDMIB. Corresponding esters are obtained from other aldehydes. Thus, by way of example, 2-methylbutyraldehyde reacts to 3-hydroxy-2-ethyl-2,4-dimethylhexyl-2-methylbutyrate and 1-hydroxy-2-ethyl-2,4-dimethylhexyl-3- (2-methyl) -butyraa-carbonate.

6 101472

The invention is based on the reaction of an aldehyde with itself, whereby a proton is removed from the alpha position of the aldehyde by the action of a basic catalyst, after which the enolate ion formed reacts with the carbonyl group of another aldehyde molecule. An aldol (aldehyde-di-alcohol) is formed which is capable of reacting with the third aldehyde molecule to give a trimer of the starting aldehyde. This trimer forms the desired monoester as a by-product of the corresponding diol.

The process of the invention is a one-step reaction, meaning that the reaction is carried out without isolating the intermediates. Typically, the final product is formed without substantially changing the reaction conditions, e.g., changing the catalyst, during the reaction. However, the temperature may vary to some extent.

The following describes the implementation of the process in a batch reactor as a half-batch process, but the invention can also - with obvious modifications to a person skilled in the art - be carried out as a batch process or as a continuous process. The batch reactor is equipped with efficient agitation and, if desired, the aldehyde feed tube can be brought close to the bottom of the reactor to mix the lighter organic material with the aqueous phase as efficiently as possible after feed.

According to a preferred embodiment of the present process, an aqueous solution of the catalyst is first fed to the reactor, the temperature of which is set to the desired value, after which the aldehyde of the general formula IV is gradually fed to the stirred solution at a constant rate. At the end of the feed, the mixture can be allowed to react further. After the reaction step, the phases are allowed to separate and the aqueous phase is decanted off. The reaction product is washed 1-5 times with water. The reaction product is further purified by decomposing the EBAL trimer into IBAL and distilling the IBAL and any light by-products. The final product is recovered: the desired monoester obtained by distillation and the corresponding diol as a by-product.

According to the invention, an aqueous mixture of lithium hydroxide having a concentration of about 0.1 to 19.9% by weight, preferably about 0.2 to 19% by weight, of lithium hydroxide is used as a catalyst in the reaction.

15% by weight, particularly preferably about 0.4 to 12% by weight. The amount of lithium hydroxide based on the amount of aldehyde, calculated by weight, is typically about 0.1: 100 to 20: 100, preferably about 0.2: 100 to 10: 100. Because the saturated aqueous lithium hydroxide solution 7 101472 typically has a concentration of about 12% by weight, more concentrated lithium hydroxide-water mixtures contain an aqueous lithium hydroxide solution and an aqueous lithium hydroxide suspension (slurry). Lithium hydroxide is so active as a catalyst that it is not necessary to increase the concentration of its aqueous mixture to more than 10% by weight, whereby all the lithium hydroxide used is still S soluble.

Lithium hydroxide can be fed to the aqueous phase of the catalyst in the form of lithium hydroxide monohydrate (LiOH * H 2 O). In the examples below, a LiOH monohydrate solution having a concentration of 3 to 10% by weight, corresponding to a concentration of lithium hydroxide 10 of about 1.7 to 5.5% by weight, has been used. Compared to sodium hydroxide solutions with the same concentration, lithium hydroxide achieves up to more than 20 percentage points of the highest yields for TMPDMEB. For the other 1,3-glycol esters, the improvements in conversions are at the same level.

The aqueous mixture of lithium hydroxide may also contain another alkali metal hydroxide, i.e. in practice sodium and / or potassium hydroxide, the total concentration of hydroxide compounds being less than 50% by weight, preferably less than 20% by weight. Even a small addition of lithium hydroxide improves the activity of the alkali metal hydroxide solution. Particularly preferred are aqueous NaOH / LiOH solutions in which the weight ratio of NaOH / LiOH is 1: 100 to 100: 1, preferably 1:50 to .50: 1, particularly preferably about 1:10 to 10: 1. According to a preferred embodiment, an aqueous solution containing about 2 to 10% by weight of sodium hydroxide and about 0.1 to 6% by weight of lithium hydroxide is used, with an aqueous solution containing about 3 to 6% by weight of sodium hydroxide and 0.2 to 2% by weight of lithium hydroxide. All the above percentages are based on the weight of the aqueous mixture / solution.

: Mixtures of potassium hydroxide and lithium hydroxide can be used in the above weight ratios. In addition, if desired, mixtures of potassium hydroxide, sodium hydroxide and lithium hydroxide can be used, in which the weight proportions of alkali metal hydroxides are mainly 1 to 100: 1 to 100: 1 to 100, preferably 10 to 100:10. ..100: 1 ... 10.

In addition to the alkali metal hydroxides mentioned above, alkaline earth metal hydroxides such as calcium, barium or strontium hydroxide can also be used. The amounts of these hydroxides are typically about 0.1 to 5% by weight, preferably about 0.5 to 3% by weight of the aqueous mixture.

The reaction temperature of the one-step condensation reaction according to the invention may be about 40 to 150 ° C, preferably about 20 to 80 ° C, particularly preferably about 40 to 75 ° C. Because aqueous catalyst solutions are used in the reaction, it is necessary to use an overpressure to reach a temperature above 100 ° C. Thus, it is typically operated at an absolute pressure of 0.8 to 4 atm, with normal atmospheric pressure being preferred. Preferably, the reaction temperature is maintained at a constant value during the addition of the aldehyde and during the subsequent reaction, typically to an accuracy of ± 2 to ± 10 ° C. The boiling point of isobutyraldehyde is about 64.5 ° C, so it is preferable to feed IBAL to a catalyst mixture having a temperature of about 60 ° C.

After the reaction, the organic phase is separated off and the aqueous phase is allowed to separate, after which the aqueous phase containing the base and optionally alkali metal and / or alkaline earth metal salts of isobutyric acid is removed by decantation.

After the reaction step, the organic phase is washed with water (1-5 times), the IBAL trimer is decomposed into IBAL by heating and the product is purified by distillation.

20

The following examples relate to 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate. tin manufacture, illustrate the invention. In all examples, a standard procedure was followed, in which a catalyst solution was first added to the reactor, the temperature was set at 20 to 80 ° C, and isobutyraldehyde was fed to the stirred reactor at a constant rate. - at the end of the feed, the mixture was allowed to react further and, after the reaction step, the phases were allowed to separate and the aqueous phase was decanted off.

30

Examples 1 and 2 are comparative examples in which only sodium hydroxide has been used as a catalyst, Examples 3 to 8 are in accordance with the present invention. Examples 3-5 use mixtures of sodium hydroxide and lithium hydroxide and Examples 6-8 use lithium hydroxide alone.

Example 1 i 5 Following the standard procedure described above, the desired 1,3-glycol ester was prepared using the following amounts and following the conditions below:

Catalyst: 10% by weight NaOH solution, 50 g IB AL: 80 g

10 Temperature 60 ° C

Feed time: 2.5 hours Total reaction time: 5.5 hours

The typical distribution of the product was as follows: IBAL 12% by weight, IBAL trimer 14 15% by weight, TMPDMIB 54% by weight, 2,2,4-trimethyl-1,3-pentadiol 14% by weight, other products 6% by weight.

Example 2 20 Following the standard procedure described above, the 1,3-glycol ester was prepared using the following amounts and following the conditions below:

Catalyst: 5% by weight NaOH solution, 50 g IB AL: 80 g

25 Temperature 45 - 70 ° C

Feed time: 2.5 hours J Total reaction time: 4 hours «

Typical product distribution: IBAL 22% by weight, IBAL trimer 26% by weight, 30 TMPDMIB 41% by weight, 2,2,4-trimethyl-1,3-pentadiol 4% by weight, other products 7% by weight -%.

10

Following the standard procedure described above, the 1,3-glycol ester was prepared according to the invention as follows:

Example 3 101472 5

Catalyst: 5% w / w NaOH solution with 1.4% w / w LiOH monohydrate, 250 g (equivalent to about 2 g LiOH)

IB AL: 400 g Temperature 60 ° C

10 Feed time: 2 hours

Total reaction time: 5 hours

Typical product distribution: IBAL 12% by weight, IBAL trimer 14% by weight, TMPDMDL 61% by weight, 2,2,4-trimethyl-1,3-pentadiol 7% by weight, other products 6 15% by weight .

Example 4

Following the standard procedure described above, the 1,3-glycol ester of the invention was prepared as follows:

Catalyst: 4% by weight. NaOH solution with 1.1% by weight of LiOH monohydrate, 250 g (corresponding to about 1.5 g of LiOH) IB AL: 400 g

25 Temperature 50 - 65 ° C

Feed time: 2.5 hours Total reaction time: 4.5 hours i

Typical product distribution: IB AL 20% by weight, IBAL trimer 28% by weight, 30 TMPDMIB 44% by weight, 2,2,4-trimethyl-1,3-pentadiol 2% by weight, other products 6 weight-%.

Following the standard procedure described above, a 1,3-glycol ester was prepared according to the invention as follows: 11

Example 5 101472 5

Catalyst: 5% w / w NaOH solution with 0.8% w / w LiOH monohydrate, 250 g (equivalent to about 1.1 g LiOH)

IB AL: 400 g Temperature 50 - 70 ° C

10 Feed time: 1 hour 45 minutes

Total reaction time: 5 hours 15 minutes

Typical product distribution: IBAL 18% by weight, IBAL trimer 15% by weight, TMPDMIB 54% by weight, 2,2,4-trimethyl-1,3-pentadiol 5% by weight, other products 8 15% by weight -%.

Example 6

Following the standard procedure described above, the 1,3-glycol ester of the invention was prepared as follows:

Catalyst: 3% by weight LiOH monohydrate solution, 50 g (= 0.84 g LiOH)

IB AL: 80 g Temperature 60 ° C

25 Feed time: 2 hours

Total reaction time: 5.5 hours

Typical product distribution: IBAL 16% by weight, EBAL trimer 29% by weight, TMPDMIB 48% by weight, 2,2,4-trimethyl-1,3-pentadiol 2% by weight, other products 5 30% by weight -%.

Example 7

Following the standard procedure outlined above, the 1,3-glycol ester was prepared according to the invention as follows: 12 101472 5

Catalyst: 5% by weight LiOH monohydrate solution, 50 g (= 1.4 g LiOH) IB AL: 80 g Temperature 55 ° C Feed time: 2 hours 10 Total reaction time: 5 hours

Typical product distribution: IBAL 10% by weight, IBAL trimer 17% by weight, TMPDMIB 63% by weight, 2,2,4-trimethyl-1,3-pentadiol 5% by weight, other products 5% by weight %.

15

Example 8

Following the standard procedure described above, the 1,3-glycol ester was prepared according to the invention as follows: 20

Catalyst: 10% by weight LiOH monohydrate solution, 50 g (= 2.8 g LiOH) IBAL: 80 g Temperature 55 ° C Feed time: 2 hours 25 Total reaction time: 5 hours

Typical product distribution: IBAL 6% by weight, IBAL trimer 3% by weight, TMPDMIB 71% by weight, 2,2,4-trimethyl-1,3-pentadiol 16% by weight, other products 4% by weight %.

30

Comparing the above examples, it can be seen that a small addition of LiOH to NaOH solution increases the yield of 1,3-glycol ester by 20 percentage points (e.g. 3 / Comparative Example 2) and 13 101472 with the same or less amount gives more than 20 percentage points better conversion with LiOH. than with NaOH (e.g. 8 / Comparative Example 2).

Claims (11)

A process for the preparation of monoesters of the general formula I R1 H R1 R1 III H-C-C - C - CH 2 - o - c - c - h (I) II! Il! Process according to claim 1, characterized in that the concentration of lithium hydroxide is less than 20% by weight. 15 Process according to claim 2, characterized in that the concentration of lithium hydroxide is about 1-12% by weight. 4. A process according to claim 1, characterized in that the aqueous solution of lithium hydroxide also contains another alkali metal hydroxide, wherein the total concentration of hydroxide compounds is less than 50% by weight, preferably less than 20% by weight. Process according to claim 4, characterized in that the aqueous solution of lithium hydroxide contains sodium and / or potassium hydroxide, wherein the weight ratio of The LiOH in relation to the other hydroxide (s) is 1: 100 ... 100: 1. 5 I HC - C = O (IV) I! R 1 H% 10 is reacted with an alkali hydroxide catalyst, characterized as such as an alkali hydroxide catalyst, a dilute aqueous solution of lithium hydroxide is used. 6. Process according to claim 4, characterized in that an alkaline metal hydroxide catalyst is used as a weak aqueous solution containing about 2-10% by weight sodium hydroxide and about 0.1-6% by weight lithium hydroxide. 30 101472 Process according to claim 6, characterized by low water aqueous solution containing about 3 to 6% by weight of sodium hydroxide and 0.5 to 2% by weight of lithium hydroxide. 5 A process according to any of the preceding claims, characterized in that the compound of general formula IV is successively added to the lithium hydroxide-containing aqueous solution which is subjected to stirring during the administration of said compound. 9. A process according to any of the preceding claims, characterized in that the aqueous solution of lithium hydroxide also contains an alkaline earth metal hydroxide, preferably calcium, barium and / or strontium hydroxide. Process according to any of the preceding claims, characterized in that the reaction is carried out in a batch reactor. 15 10 R2 0H R2 0 R2 respectively. the general formula II R 1, H 1, R 11 111 HCCC-CH 2 -OH III R 2 O R 2 (II) c = 0.10 O R - CH - R 2 and / or for the preparation of diols of the general formula III R H R1 III- HCCC - CH2-0H (ΙΠ) III R 2 is OH the same or different and is substituted for a lower alkyl, according to which process an aldehyde of formula IV * 2 A process according to any of the preceding claims, characterized in that a monoisobutyrate of 2,2,4-trimethyl-1,3-pentanediol is prepared. «