DE1965001C3 - Process for the production of pivalolactone (a a-dimethyl- ß-propiolactone) - Google Patents

Description

characterized in that an ester of the general formula (2)

O CH ₃

CH ₃ COCH ₂ -C-COOR (2)

CH,

in which R is the methyl radical or the group
CH, O

ι ■ II

-CH ₂ -C-CH ₂ OCCH,

means, in the gas phase at temperatures of 150 _{1 (} > up to 350 ° C on crystalline aluminum silicates with uniform pore size in the form of molecular sieves, in which the alkali ions are replaced by protons or by alkaline earth ions.

2. The method according to claim 1, characterized in that a molecular sieve is used in which the ion exchange by protons in two stages, first with aqueous acids and then with aqueous ammonia, with the molecular sieve being heated to 500 to 700 ^° C. in the meantime has been made.

pionic acids by dehydrohalogenation with bases such as sodium carbonate or lead oxide with loss of the Produce halogen-alkylated j3-lactones.

Another method for the preparation of alkylated O-Lactc-nen is the conversion of ÄA-disubstituted /? - Hydroxycarboxylic acids with thionyl chloride in Pyridine, which only leads to low lactone yields (Journal of OrganieChemistry Bei. 25, p. 1812 [196O]).

Another possibility for the preparation of alkylated ^ -lactones consists in the implementation of substituted ketones with aldehydes or ketenes (US Pat. No. 30 00 906, 32 21 028). Difficulties this procedure lies in the preparation and handling of the ketenes.

Furthermore, there are various thermolytic processes for the production of alkylated ^ -lactones and using various supported catalysts, inter alia. also of various silicates, such as Aluminum sulicates known, e.g. B. from GB-PS 11 35 820, GB-PS 11 45 589, as well as FR-PS 15 14 662, however, a corresponding ^ -hydroxycarboxylic acid is used in aJJen these processes or /? - Acyloxycarboxylic acid used as starting material and no corresponding one Acid ester. However, the esters cannot be obtained by these processes, or only in low yields ^ -Thermolyse lactones.

There has now been a process for the preparation of pivalolactone of the formula (1),

The most common method for the production of 5- and 6-ring lactones is the elimination of water from γ- or o-hydroxycarboxylic acids, which in most cases fails to prepare 4-ring lactones (0-lactones) because the elimination of water leads from 9-hydroxycarboic acids to ^ - unsaturated acids (Holben-Weyl, Methods of Organic Chemistry, Georg Thieme Verlag, Stuttgart, 1963, Volume VI / 2, page 517). If, as in hydroxypivalic acid («, ix-dimethyl - /? - hydroxy-propioic acid), both hydrogen atoms in a ^ -hydroxycarboxylic acid are substituted by alkyl groups, no lactone is formed by elimination of water; instead, condensation to form low molecular weight polyesters and cleavage of the carbon bonds between the quaternary carbon atom on the one hand and the carboxyl group or primary alcohol group on the other hand take place. Other special production methods for alkylated ß-lactones are usually not very selective or have other disadvantages.

So you can after the German patents 1167 809 and 12 27 884, as well as the Belgian Patent 6 39 614 from alkylated / J-Halogenpro-

45

H ₃ CC CO

CH, O

(D

found, which is characterized in that an ester of the general formula (2)

CH,

ClI ₁ COCH ₂ (COOR

(2)

in which R is the methyl radical or the group
CH, O

I ■ Ii

-CH ₂ -C-CH ₂ -OCCH,
CH,

means in the gas phase at temperatures from 150 to 35O ° C of crystalline aluminum silicates with more uniform Pore size implemented in the form of molecular sieves, in which the alkali ions by protons or by Alkaline earth ions are replaced.

It was surprising that the acid esters of the formula (2) can also be cleaved thermolytically to pivalolactone by the process according to the invention. It is a considerable advantage that the ester di.ekt can be converted into pivalolactone in this way

can. In the case of / J-acetoxyneopentyi - /? - acetoxypivalate, the reaction proceeds according to the following equation:

CH ₃ CH ₃

CH ₃ COOCH ₂ -C-COO-CH ₂ -C-Ch ₂ OCOCH ₃

CH,

CH ₃

CH ₃ CH ₃

CH ₃ -CC = O + CH ₃ COOCH ₂ -C-CH ₂ OCOCh ₃

CH ₂ -O

The second cleavage product - Neopentytglykoldiacetat - can be either as such further use, or, ι s since it is also subject to Esterpyrolye and thereby partially breaks down into smaller fragments such as acetic acid, formaldehyde and isobutyraldehyde, reinsert} n the form of fission products for the production of the starting compound.

The process according to the invention for the preparation of pivalolactone is particularly recommended in the cases in which the respective starting ester emerges as an inevitable attack from otherwise interesting reactions. For example, in the representation of hydroxypivalaldehyde, formaldehyde and Isobutyraldehyde (as a result of disproportionation) of the hydroxyneopentyl ester of hydroxypivalic acid as a by-product. The reaction can also be directed so that this ester becomes the main product. the Esterification of the two terminal hydroxyl groups by known processes with acetic acid then leads to a starting ester of the formula (2).

The crystalline aluminum silicates to be used as catalysts in the form of molecular sieves with ^ a uniform pore size have the particle size of which is suitable for the fluidized bed or fixed bed for example 0.07-0.3 mm or powder form when used in inert high-boiling solvents and to increase the acidic properties and thus to increase the lactone selectivity, the monovalent ones Alkali ions using known exchange processes for protons or alkaline earth ions, such as Calcium ions have been exchanged. Particularly beneficial is the exchange of alkali ions for protons, if it takes place in stages, first with dilute aqueous acids and then with dilute aqueous ammonia, in the meantime the The molecular sieves concerned are heated to 500 to 700 ° C., preferably to 550 to 650 ° C., and then the Ion exchange continues.

Molecular sieves with a smaller or larger pore size can be used; Particularly favorable results are obtained with molecular sieves with a uniform pore size of 5 Å. _ss

The reaction with the catalyst to be used takes place at temperatures between 150 and 350 ° C. Particularly favorable results are obtained if the acetoxypivalic acid ester according to the general formula (2) is brought _{to reaction between 250 and 300 ° C. over the catalyst (, 0.} It can be added in liquid form directly or after dilution with an inert solvent such as benzene or xylene i, ~, is arranged either in a fixed bed or fluidized by the vaporized starting materials to a fluidized bed are vaporized and passed in the gas phase alone or together with inert gases over the catalyst.

CH ₃

Let out the fumes of the acetoxypivalic acid ester can also be fed into an inert high-boiling solvent in which the catalyst is in finely divided form is present.

It is expedient to use a reduced pressure, which depends on the boiling point of the acetoxypivalic acid ester used and the reaction temperature and is advantageously between 10 and 100 torr.

The reaction products are cooled and all condensable products are fractionally solidified. Educated Pivalolac'on is separated off and unconverted feedstock is fed back into the reaction. Pivalolactone is a valuable starting product for the production of linear polyesters, which are used as thermoplastics and used as fibers.

example 1

The catalyst was prepared as follows. Crystalline aluminum silicate of uniform pore size _{with an SiO 2 IAl 2} Oj ratio of approx Washed / oiger aqueous acetic acid at 80 ⁰ C, dried and calcined at 600 ° C for 3 hours. It is then washed with half-concentrated aqueous ammonia solution, dried and calcined for 3 hours at 300 ⁰ C.

25 ml of the above catalyst are heated to 275 ° C. in a fluidized bed reactor with the aid of an electric heater. At this temperature and a pressure of 12-14 torr, 10.3 g of iS-acetoxyneopentyl - ^ - acetoxypivalate and 0.3 l of nitrogen are passed into the reactor every hour via an evaporator and reacted on the swirling catalyst. The reaction product is condensed and in cold traps (-40 to -50 ⁰ C) was analyzed by gas chromatography. With a conversion of the / J-acetoxyneopentyl-jü-acetoxypivalate of 55 mol%, the pivalolactone yield is 55 mol%, based on the ester used. The unreacted ester is separated from the pivalolactone and the by-products formed by distillation and reused for the reaction. The pivalolactone obtained by distilling the condensate boils at a boiling point of 54.degree. According to GC analysis, it has a purity of> 99.9% by weight and is identical to a pivalolactone (according to GC and IR analysis) which was produced by another known process.

Example 2

The catalyst was prepared as follows: First, the Al!: Ali ions of the same X molecular sieve would be produced exchanged for ammonium ions as in Example 1 by treatment with Ammor.lumchloridlösung. This is done using 217 g (300 ml) of the molecular sieve within 4 hours with a solution of

265 g ammonium chloride in 620 g of water in a heatable column at 90-10O ⁰ C continuously charged. Subsequently, the molecular sieve is washed free from chloride ions, dried and caiciniert 3 hours at 300 ⁰ C. The H + form of the molecular sieve is obtained with the release of ammonia.

Under the same test conditions as in Example 1 is a conversion of / 3-acetoxyneopentyl - /} - acetoxypivalate using the catalyst prepared above of 85 mol% achieved with a pivaloiactone yield of 63 mol%.

Example 3

The procedure is as in Example 1, with the difference that a crystalline aluminum silicate with a uniform pore size of about 10 Å and an SiO2: Al2O; ratio of about 2.8 is used, which is commercially available as a Y-type molecular sieve and a grain size of 0.1 -0.3 mm has IBO ml of molecular sieve are in a heated column in 2 hours with a solution of 100 g of calcium chloride in 400 g of water at 90-100 ⁰ C continuously charged.

The molecular sieve changes into the calcium form. It is then washed free of chlorine ions, dried and caicinated for 3 hours at 300 ° C.

A 14% conversion of the α-acetoxyncopentyl - /} - acetoxypivalate is obtained an yield of 14 mol%

• .ο of pivalolactone.

Example 4

As described in Example 1, at 300 ⁰ C and 12-14 Torr and with the addition of 0.151 nitrogen per hour 10.3 g methyl-j? -Acetoxypivalat instead of the jS-Acetoxyneopentyl-Jae-acetoxypivalats reacted. With a 20% conversion of the ester, a 15 mol% yield of pivalolactone is obtained.

Claims (1)

Patent claims: 1. A process for the preparation of pivalolactone of the formula (1), CH,
H ₃ CC C = O I! CH, O (D