SK287959B6 - Process for the preparation of hydroxypivalic acid - Google Patents

Abstract

Process for the preparation of hydroxypivalic acid (3-hydroxy-2,2-dimethylpropionic acid) by oxidizing hydroxypivaldehyde with hydrogen peroxide. The oxidation is conducted in the presence of (2,2,6,6-tetramethylpiperidine)oxyl or its derivatives substituted in position 4 or precursors thereof. The oxyls are used in a catalytic amount, wherein their presence in the course of the oxidation significantly increases the amount of isolated hydroxypivalic acid.

Description

Technical field

The invention relates to a process for the preparation of hydroxypivalic acid (3-hydroxy-2,2-dimethylpropionic acid) by oxidation of hydroxypivalaldehyde with hydrogen peroxide.

BACKGROUND OF THE INVENTION

According to the earliest data, hydroxypivalic acid was prepared by oxidation of neopentyl glycol with potassium permanganate (Wessely: Monatshefte 22, 66) or Cannizzar reaction from hydroxypivalaldehyde using potassium hydroxide solution (Wessely: Monatshefte 21, 222). The disadvantage of both methods was the low yield and therefore they were industrially unattractive.

It is also known to oxidize neopentyl glycol with air or oxygen on a Pd / C or Pt / C catalyst [US 3,799,977; JP 53/77 010 (1978)]. U.S. Pat. No. 3,799,977 lacks data on yields. Mitsui Toatsu Chemicals (JP 53/077 010) prepares hydroxypivalic acid from neopentyl glycol in neutral and resp. a weakly alkaline solution with oxygen in the presence of a Pd catalyst. Pd is deposited on activated carbon or alumina at a concentration of 0.5 to 10% by weight. and the oxidation is carried out at a temperature of up to 150 ° C and a pressure of up to 1.0 MPa.

Oxidation of hydroxypivalaldehyde with hydrogen peroxide was first described in Monatshefte fur Chemie, 95 (1964), 410 and a revised variant in JP 43/24 888 (1968). The disadvantages of the processes are the preparation of impure hydroxypivalic acid and low yield of pure acid (65-68%).

According to more recent information (patents of Bayer AG DE 19 632 922 and DE 19 632 924), hydroxypivalic acid is produced by oxidizing hydroxypivalaldehyde with hydrogen peroxide at a temperature of 60 to 80 ° C. The concentration of hydrogen peroxide in the reaction solution is maintained by dosing it to a concentration of 4% by weight until the concentration of hydrogen peroxide falls below 1% by weight. While the yield of hydroxypivalaldehyde is 89.5% after aldolization, the yield of hydroxypivalic acid is 74% after oxidation of the aldehyde. Isolation after distilling off the water with n-butyl acetate-cyclohexane gave crystalline hydroxypivalic acid in 49.5% yield on the isobutyraldehyde used (DE 19 632 924).

SUMMARY OF THE INVENTION

The present invention provides a process for the preparation of hydroxypivalic acid by oxidation of hydroxypivalaldehyde with hydrogen peroxide, wherein the oxidation is carried out in the presence of a catalytic amount of 2,2,6,6-tetramethylpiperidine or its 4-substituted derivatives or precursors thereof.

Said substances are used in catalytic amounts, the presence of which during the oxidation substantially increases the amount of hydroxypivalic acid isolated. Oxidation can also be carried out with the raw materials from which in situ oxyly can be prepared, namely, 2,2,6,6-tetramethylpiperidine, 2,2,6,6-tetramethyl-4-hydroxy-, respectively. 2,2,6,6-tetramethyl-4-oxo-piperidine.

The entire process of the invention is evident from the examples given.

EXAMPLES

Example 1 - Comparative

Condensation of 25% formaldehyde (Fd) with 99.5% isobutyraldehyde (IBA) was carried out in a 1.0 L flask equipped with a reflux condenser, stirrer, thermometer and dosing funnel, at a molar ratio of 1.17 mole Fd per mole of IBA using triethylamine (TEA) in an amount of 0.05 mole / 1 mole of IBA catalyst at 55 ° C maintained by a water bath.

After reaction at 55 ° C for 3 h, the mixture was heated to 85 ° C for 1 h and then cooled to 70 ° C. To the mixture at this temperature for 2h charged with hydrogen peroxide (H ₂ O ₂₎ at a concentration of 50%, using 0.74 pier peroxide to 1 mole of isobutyraldehyde.

In the reaction solution, the hydroxypivalic acid (HPA) content was determined on a gas chromatograph to obtain an acid yield of 54.5% calculated on the isobutyraldehyde to be metered. From this solution after distilling off the water at 106 ° C and then using a vacuum rotary evaporator at a bath temperature of 80 ° C and a pressure of 13 to 1.3 kPa, a product having a purity of 97.1% was obtained after cooling the solution in n-butyl acetate-cyclohexane. yield 53% calculated on hydroxypivalic acid present in the solution. The overall yield on IBA was 33.7%, t. j. 0.55 kg HPA per 1.0 kg dosed isobutyraldehyde.

Example 2

The aldolization of formaldehyde with isobutyraldehyde was repeated under the same conditions (apparatus and procedure) as in Example 1.

The oxidation of the aldolization mixture was additionally carried out with the addition of 3.6 millimoles of 2,2,6,6-tetramethylpiperidine oxy to 1 mole of isobutyraldehyde under the same conditions as in Example 1. Similarly, the reaction mixture was treated to yield 0.87 kg HPA at a concentration of 98% per kg of dosed IBA. This yielded an increase in yield of 58.2% compared to Example 1.

Example 3

In the apparatus of Example 1, but using the same molar amount of trimethylamine calculated as isobutyraldehyde, condensation of formaldehyde with isobutyraldehyde was performed under otherwise unchanged reaction conditions.

Subsequently, oxidation with hydrogen peroxide in the presence of 7.2 millimoles / 1 mole of IBA 2,2,6,6-tetramethyl-4-oxo-piperidinoxyl was carried out under the same technological conditions, similar to the isolation of the product.

This procedure resulted in a conversion of 0.65 kg of HPA per 1.0 kg of 99.0-metered IBA to be metered in

%.

Example 4

Condensation was carried out in the apparatus of Example 1 but using dimethylethanol-amine in the same molar amount to isobutyraldehyde, under unchanged reaction conditions.

Hydrogen peroxide oxidation was carried out with a precursor 2,2,6,6-tetramethyl-4-hydroxypiperidinoxy in an amount of 1.8 millimoles per mole of IBA, under the conditions of Example 1. The reaction solution was worked up as well.

Under these conditions, 0.68 kg HPA per kg IBA was obtained with a purity of 99.5% determined by titration.

Example 5

In the apparatus of Example 1, but using dimethylcyclohexylamine in the same molar ratio to IBA as in Example 1, condensation of Fd with IBA was performed. Condensation was carried out under the same conditions as in Example 1.

Subsequently, oxidation was carried out with hydrogen peroxide in the presence of 2,2,6,6-tetramethyl-4-hydroxypiperidine in an amount of 10 mmol per 1 mol of IBA under the same oxidation conditions as well as treatment of the solution as in Example 1.

Under these conditions, 0.65 kg HPA per kg IBA was obtained.

Industrial usability

Hydroxypivalic acid is suitable for the production of esters, polyesters, polyurethanes, for use as a viscosity regulator for aqueous detergent suspensions, for the manufacture of powders, cosmetics, lubricating oils, paints, paint thinners or as a rinse aid alone - to prevent staining on dishwashers, detergent additive and the like.

Claims (1)

Process for the preparation of hydroxypivalic acid by oxidation of hydroxypivalaldehyde with hydrogen peroxide, characterized in that the oxidation is carried out in the presence of a catalytic amount of 2,2,6,6-tetramethylpiperidine oxides or of the 4-substituted derivatives thereof or precursors thereof.