DE1215173B - Process for the preparation of crystalline sodium salicylate - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Int. α .:

C07c

German class: 12 q - 29/03

Number: 1215 173

File number: D 36313IV b / 12 q

Filing date: June 12, 1961

Opening day: April 28, 1966

Processes for the preparation of alkali salicylate are described in British Patents 384,619 and 774,837 described. Alkali phenolates and carbon dioxide are used as starting materials. It is there to use a reaction time of at least 15 and more hours at atmospheric pressure, or for a shorter reaction time of about one hour, a pressure of 50 to 200 atmospheres and more required.

It is also known to mix dry, anhydrous sodium phenolate with carbon dioxide with vigorous stirring implement, but in the known procedures, the reaction takes place in the absence of phenol. the Disadvantages of this method of operation are, inter alia, that they are not converted in the reaction Phenolates can only be extracted from the product with a special effort. Around To avoid these disadvantages, one has to convert the phenolate with the carbon dioxide carried out in a thin film evaporator.

In a known way of working (US Pat. No. 2,824,892), as in the case of the working method, the Invention also an anhydrous mixture of sodium phenolate and phenol at an elevated temperature and increased pressure reacted with carbon dioxide, but here the reaction takes place in the presence an aliphatic alcohol. The known method requires a pure product to be obtained many and laborious steps. It is here the reaction mixture with water and sulfuric acid added and after the separation of the layers to the separated aqueous solution containing the sodium salicylate Layer still more sulfuric acid added, whereby the salicylic acid precipitates, which is then filtered off will.

It has now been found that it is possible in far shorter reaction times and without it being necessary to use such high pressures, by reacting anhydrous sodium phenolate-phenol mixtures with carbon dioxide at 140 to 175 ^° C. and 2 to 11 atmospheres under vigorous Stir to obtain crystalline sodium salicylate. The procedure according to the invention is characterized in that the reaction is carried out with solutions of 1 mole of sodium phenolate in 3 to 9, preferably 5 to 6 moles of phenol, the sodium salicylate is separated off from the reaction mixture by settling or filtration and, if necessary, washed with a solvent.

According to the procedure according to the invention, it is possible, for example, at a pressure of only 5 atmospheres and a reaction time of one hour to obtain sodium salicylate of high purity.

Process for the production of crystalline
Sodium salicylate

Applicant:

The Dow Chemical Company,

Midland, me. (V. St. A.)

Representative:

Dipl.-Ing. F. Weickmann,

Dr.-Ing. A. Weickmann,

Dipl.-Ing. H. Weickmann

and Dipl.-Phys. Dr. K. Fincke, patent attorneys,

Munich 27, Möhlstr. 22nd

Named as inventor:
Floyd Llewellyn Beman,
Midland, me. (V. St. A.)

Claimed priority:

V. St. v. America June 17, 1960 (36 747) - -

In the process of the invention, pure crystalline sodium salicylate is obtained in almost quantitative yields separated off from the reaction mixture in a simple manner by settling or filtering and obtained in great purity, especially if for the separation of phenolate and traces of Phenol with a solvent such as toluene, xylene, chlorobenzene, dichlorobenzene or mixtures of these Fabrics are rewashed.

The filtrate obtained during washing is advantageously used as a fresh one as the starting material using phenol-phenolate solution added again. That contained in the filtrate (washing liquid) Solvent can serve as an azeotropic agent for the water contained in the phenol-phenolate mixture.

It is z. B. Sodium hydroxide reacted with phenol in a ratio of 1 mole of hydroxide per 4 to 10 moles, so as to obtain a mixture of 3 to 9 moles of phenol per mole of phenolate. But it can also be the hydroxide and the phenol are reacted in a molar ratio of 1: 1 to then obtain the Phenolate to dissolve in 3 to 9 moles of phenol. The obtained phenolate solution in phenol becomes part distilled or otherwise treated in order to

609 560/486

i 215173

to separate available water. The dry phenolate dissolved in phenol is preferably continuous added to a reaction device which simultaneously supplied carbon dioxide under pressure will. The temperature is maintained at 140 to 175 ° C. The reaction mixture is continuously taking vigorous stirring. The process product separates out in the form of crystals and becomes out removed from the reaction mixture by filtration or settling. The crystals come with a Solvents, e.g. B. toluene, xylene, chlorobenzene or dichlorobenzene, washed to phenol and phenolate, but not salicylate. The remaining filtrate, which is still small amounts of phenol and not contains converted phenolate, is advantageously reused in the cycle. If that's for washing The solvent used is water azeotropic, it is also used in the cycle.

Although 3 to 9 moles of phenol can be used per mole of phenolate, one is preferred work with 5 to 6 moles per mole of phenolate, since you then have a pumpable solution of the phenolate and the Sodium salicylates in phenol.

The pressure ranges from 2 to 11 atmospheres.

Using higher pressures would require more equipment.

A special procedure is to add phenol and 50% sodium hydroxide to a mixing tank in such a ratio that a mixture of 1 mole of sodium phenolate per 6 to 7 moles of phenol is obtained. This mixture, with or without a water-azeotropic agent, is fed to a distillation column which operates under such conditions that water contained in the solution is removed as an azeotrope with phenol or, if another azeotropic agent is present, the water is removed together with this, and so on at the bottom of the column, an anhydrous mixture of phenol and phenolate with a ratio of 6 moles of phenol per mole of phenolate can be obtained. The anhydrous phenolate mixture is fed continuously to a reaction device in which there is a carbonic acid pressure of 2 to 11 atmospheres. The mixture is heated to 140 to 175 ^° C. and stirred vigorously during the reaction. The reaction product is allowed to run through a filter or a centrifuge to separate the sodium salicylate crystals. After washing the crystals with chlorobenzene, toluene or another solvent for phenol, a product with a degree of purity of 99.5% is obtained. The salicylate obtained represents about 90% of the phenolate used. The filtrate and the washing liquid are preferably recirculated to the mixing tank, to which phenol and hydroxide are additionally added in order to produce the required phenolate-phenol ratio Subjected to distillation to separate the water azeotropic agent such as chlorobenzene and some phenol, the phenol is recycled and the solvent is used to wash the filter cake.

example

A completely anhydrous solution of 25 parts by weight of sodium phenolate in 75 parts by weight Phenol (obtained by azeotropic distillation of sodium phenolate in phenol in the ratio of 1: 3.5 mol) is at 165 ° C with continuous feed of carbon dioxide under a pressure of 5 at hour in a reaction device with a shovel: agitator treated. The reaction product obtained is washed with chlorobenzene. The party-

ao product is sodium salicylate with a purity of 99.5%.

Claims (3)

Patent claims: 1. Process for the preparation of crystalline sodium salicylate by reacting anhydrous Sodium phenolate-phenol mixtures with carbon dioxide at 140 to 175 ° C and 2 to 11 atm with vigorous stirring, characterized that the reaction is carried out with solutions of 1 mole of sodium phenolate in 3 to 9, preferably 5 to 6, moles of phenol, separating the sodium salicylate from the reaction mixture by settling or filtering and if necessary, washes with a solvent. 2. The method according to claim 1, characterized in that the reaction is carried out continuously performs. 3. The method according to claim 1, characterized in that the solvent used is toluene, Xylene, chlorobenzene, dichlorobenzene or mixtures of these substances are used. 4. The method according to claim 1 and 3, characterized in that the washing of the The filtrate obtained from salicylates is added to the phenol-phenolate solution. Considered publications: German Auslegeschrift B- 32101 IVb / 12q, (published on June 14, 1956); U.S. Patent No. 2,824,892; Chemisches Zentralblatt 1956, p. 12627; Ullmann's Encyclopedia of Industrial Chemistry, 2nd Edition, Vol. 2, pp. 237, 238 and 3rd Edition, Vol. 13, P. 85. 609 560/486 4.66 © Bundesdruckerei Berlin