DD238232A1 - PROCESS FOR PREPARING 2,2-DIMETHYL-4-METHYLOL-1,3-DIOXOLANE - Google Patents

Abstract

2,2-dimethyl-4-methylol-1,3-dioxolane is used as a component of skin care agents, as an antioxidant for synthetic oils, as a synthesis component for pharmaceuticals, insecticides, transparent adhesive systems and the like. a. versatile needed. It is the object of the invention to produce the preparation of 2,2-dimethyl-4-methylol-1,3-dioxolane in rapid reaction with the least possible technical and energy expenditure from acetone and glycerol. According to the invention, the two components, preferably in a molar ratio of 1: 1, are mixed with an acidic soluble catalyst such as toluenesulfonic acid, HCl, H 2 SO 4 at a temperature preferably in the range between 20 ° C and 50 ° C and the catalyst is finished in fractions of a minute up to a few minutes Reaction inactivated by neutralization. The components are separated by distillation. The conversion to 2,2-dimethyl-4-methylol-1,3-dioxolane is about 45%. Repeated use of recovered in the distillation units unreacted feedstock products, a total conversion of about 95% is achieved for glycerol.

Description

Field of application of the invention

The invention relates to a process for the preparation of 2,2-dimethyl-4-methylol-1,3-dioxolane, which is a constituent of main care agents, as an antioxidant for synthetic lubricants, as a synthesis component for pharmaceuticals, insecticides, surfactants, transparent poiymerisationsfähige adhesive systems u.a. has versatile uses.

Characteristic of the known technical solutions

The reaction of glycerol and acetone is the almost only economically viable way to produce 2,2-dimethyl-4-methylol-1,3-dioxolane.

CTU CH-CJ-UOH + CH ₀ -CO-CH-, -> CH-CH ₀ -CH OH ₀ + H ₀ O dd 3 3 2 s 2 d

₀ -CO-CH-, -> CH ₀ -CH-CH ₀ 3 3 ι 2 s 2

OH OH 0, 0

As catalysts for the reaction have been proposed:

Hydrogen chloride (E. Fischer, E. Pfähler: Ber.dt.ehem.Ges.53 (1920) 1027, JC Irvine et al .: J.ehem.Soc / London / 107 (1915) 343), toluenesulfonic acid (MS Newman, M. Renoll: J.am.chem.Soc.67 (1945) 1621), sulfuric acid (R.Aldo Macchi, T. Crespo: Rev. Argent, Grss. Aceitas S [2] [1972] 9) They dissolve in the reaction mixture ,

In order to achieve the highest possible conversion, in many cases water is bound either with the aid of sodium sulfate (see E. Fischer, E. Pfähler, R. Aldo Macchi, T.Crespo) or phosphorus pentoxide (at the same time as a catalyst) and yields of 77 -80 ⁰ C based on glycerol achieved. The spent desiccant is by-product of the reaction. The reaction takes a long time with sodium sulfate (12-18 hours). For the removal of the water, distillation with water separation with petroleum ether (see MS Newman, M.Renöl I) or chloroform (J.Chechniki, J.Gyganska, H.Grynberg: Poin, Pat., 63323 [1967]) is also used These processes require a lot of time (43 h for petroleum ether), because large amounts of petroleum ether or chloroform must be distilled to tow the water reasonably completely, and therefore require correspondingly high technical and energy costs., However, they result in sales of over 90% to the glycerine submitted in deficit.

The disadvantages of the known technical solutions for the preparation of 2,2-dimethyl-4-methylol-1,3-dioxolane from glycerol and acetone are that a group of the methods have significant consumption of desiccant and a considerable reaction time, the spent desiccants lost as a waste product. Another group of methods requires considerable technical and energy expenditure for the lengthy distillative removal of the water with the aid of entrainers and also require considerable safety-technical effort in the use of petroleum ether due to the high risk of fire and explosion.

Object of the invention

The aim of the invention is the preparation of 2,2-Dimethyi-4-rnathylol-1,3-dioxolane from glycerol and acetone with the least possible technical, energetic and economical effort.

Explanation of the essence of the invention

The invention has for its object to develop a method that allows to produce 2,2-dimethyl-4-methylol-1,3-dioxolane from acetone and glycerol at low reaction time and waiving desiccant or additional entrainer.

It has been found that the reaction of glycerol and acetone to 2,2-dimethyl-4-methylol-1,3-dioxolane and water using soluble acid catalysts, at temperatures in the range

from ^{0 0} C and the boiling point of the acetone and stirring in just a few minutes to a fraction of a minute practically to equilibrium expires. While acetone and glycerin are only miscible with each other to a limited extent, a homogeneous system is formed during the course of the reaction. This can, as hitherto disregarded, be advantageously separated by distillation, technically and economically, if the soluble acidic catalyst is inactivated with a basic medium before distillation. In order to produce a required amount of 2,2-dimethyl'-4-methylol-1,3-dioxolane, it is necessary in this way to distil off a significantly smaller amount of easily evaporating components than in the case of a distillation distillation, so that the technical and energetic and consequently the economic outlay is reduced. Desiccant is not needed in this process.

According to the invention, glycerol and acetone, preferably anhydrous or with low water content, in a ratio of 5: 1 to 1: 5, but preferably 2: 1 to 1: 2, together with a soluble acidic catalyst, preferably a small amount of an inorganic known per se Acid, such as HCl, H ₂ SOa, or organic acid, such as toluenesulfonic acid, acetic acid, oxalic acid, combined at a temperature in the range of 0 ° C and boiling temperature of the acetone with mixing until the slight increase in temperature is terminated by the reaction. Thereafter, the acid catalyst is inactivated by the addition of a basic medium, preferably sodium hydroxide or soda, according to the inventive method. Inactivation is detected by means of neutralization indicators, eg phenolphthalein or a p _H electrode. The mixture is then separated by distillation in a conventional manner. By applying rectification, it is possible to recover a large part of the unreacted acetone almost anhydrous. This is followed by rectification water. Further distillation in vacuo gives pure 2,2-dimethyl-4-methylol-1,3-dioxolane. The remaining, discolored residue is glycerol in the main cluster and, like the recovered acetone, can be reused, achieving a total glycerol conversion of about 95%.

embodiment

Technical acetone with a water content of less than 0.5% by mass and glycerol, which has been substantially freed of water by heating in vacuo, is in the volume ratio 1: 1 (equivalent to about one mole ratio 1: 1) with about 30 g Toluensulfonsäure. related to 101 mixture as a catalyst at 25 ° C with stirring, which covers the entire reaction mass mixed. The reaction approximately reaches the equilibrium after about 6 minutes with a temperature increase of about 8K. The mixed Li ng is mixed with the required amount of sodium hydroxide solution for neutralizing the toluenesulfonic acid, so that mixture mixed with phenolphthalein as an indicator just turns red. The mixture is separated by rectification under atmospheric pressure and distillation under vacuum. 2,2-Dimeihyl-4-methylol-1,3-dioxolane distilled at a pressure of 26.7 mbar and 98 ⁰ C. It is obtained depending on the water content of the starting components with a Urnsatz of 30-45% based on one of the two components. When using backglycerol and acetone, the conversion reaches about 45%. For glycerol, a total conversion of about 95% is achieved by repeated use

 The advantages of the method according to the invention are that

In comparison with the known processes which use desiccant, e is a short reaction time,

β no desiccant is needed and

β eliminates the accumulation of spent desiccant as a by-product,

- Compared to the known processes of the entrainer distillation

ο the amounts to be distilled to obtain a required amount of product are considerably lower and

Thus, the apparatus and energy costs considerably reduced, the separation of acetone and water by rectification is easily possible, while the separation of chloroform

and water due to residual solubilities can be mechanically incomplete, β the high risks are reduced when using petroleum ether and ο also high overall sales can be achieved despite low partial sales.

Claims (3)

Invention claim: 1. A process for the preparation of 2,2-dimethyl-4-methylol-1,3-dioxolane by reacting glycerol and acetone, characterized in that the components in the ratio 5: 1 to 1: 5 together with a small amount of a soluble Acid catalyst at a temperature above 0 ⁰ C with mixing, which covers the entire reaction mass, as long as combined until the slight increase in temperature is about completed, neutralized the acidic catalyst with a basic medium and the mixture is separated by distillation in a conventional manner. 2. The method according to item 1, characterized in that glycerol and acetone are preferably used in a molar ratio of 2: 1 to 1: 2. 3. The method according to item 1 and 2, characterized in that as a soluble acidic catalyst is preferably a known per se inorganic acid such as HCl, H ₂ SO ₄ , H ₃ PO ₄ OdUr organic acid such as toluenesulfonic acid, acetic acid, oxalic acid is used , 4. The method according to item 1, 2 and 3, characterized in that the reaction is preferably carried out in the temperature range between 2O ⁰ C and 50 ° C. 3. The method according to item 1 to4, characterized in that for neutralization of the catalyst with a basic medium, preferably an alkali or soda is used.