CS240893B1 - Process for refining 2,6-xylenol - Google Patents

Abstract

The solution relates to the refining of 2,6-xylenol by selective orthocondensation with paraformaldehyde or formaldehyde. The reaction mixture is freed from 2,6-xylenol residues by steam stripping.

Description

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DESCRIPTION OF THE INVENTION

FOR COPY CERTIFICATE (61) (23) Exhibition Priority (22) Registered 14 06 84 (21) PV 4496-84 (40) Published 16 07 85 (45) Published _{01 01 88} (11) (Bl) (51) Int Cl ?

OJ C 07 C 39/06

LOTS OF EDUARD ing.CSc., *

KUCA JOSEF ing.CSc .; ELEFANTOVA DAGMAR, *

ČERVINKA BOHUMIL, BRNO, ZADADLO ZDENĚK, ŽIDLOCHOVICE;

MACHÁČEK OTAKAR, BRNO, * POLÁČEK KAREL, TESANÝ, * happy milan ing.csc.

ČIERNIK JÁN ing., CSc., ´ AICBROS DUŠAN ing.CSc., BARTÁŠKOVÁ PAVLA ing .;

Process for refining 2,6-xylenol

The present invention relates to the refining of 2,6-xylenol by selective orthocondonation with paraformadehyde or formaldehyde. The reaction mixture was freed of 2,6-xylenol residues by steam evaporation.

240,893 _x 240,893

The invention relates to a process for refining 2,6-oxylenol and isolating pure 2,6-xylenol.

The source of xylenol is the reaction mixture after the methylation of phenol, which contains mainly methylphenols (o-, m- and p-cresols), di- and trimethylphenols. To a lesser extent, irrelevant from a quantitative point of view, also other phenol methylation products. According to the phenol methylation reaction conditions, the reaction mixture contains a different ratio of o-cresol and 2,6-xylenol, depending on the requirement whether the main methylation product should be o-cresol or 2,6-xylenol. After o-cresol has been distilled off, 2,6-xylenol remains the major and most important component of the remainder of the reaction mixture. Of the other methyl derivatives of phenol, the o-, m- and β-cresols themselves account for up to 95% by weight of impurities.

Until now, 2,6-xylenol has been isolated from this mixture and isolated by physical procedures such as rectification, crystallization, and crystallization. fractional crystallization or a combination thereof. All these processes are characterized by being very energy intensive, time consuming and requiring complex and costly equipment.

It is known that technical 2,6-xylenol can be successfully removed from the above impurities by reaction with paraformaldehyde or aqueous formaldehyde in the presence of catalysts.

The most suitable catalysts are metal oxides (divalent and polyvalent), fatty acid salts of divalent and polyvalent metals. In the presence of these catalysts, paraformaldehyde or aqueous formaldehyde solution preferably reacts with compounds having at least one free ortho-position to a phenolic OH group, such as unreacted phenol and especially methylation products, especially cresols.

To isolate 2,6-xylenol, the reaction water is first distilled off from the reaction mixture together with any excess unreacted aqueous formaldehyde solution and then 2,6-xylenol.

In the isolation of 2,6-xylenol from the reaction mixtures after chemical treatment

240 893 by vacuum distillation refining, a process equipment for separating the reaction water containing about 11-13% by weight of 2,6xylenol and a vacuum system to achieve a vacuum of less than 20 kPa, which is easily clogged and clogged with volatile 2,6-xylehol, is required. This prolongs the isolation of pure 2,6-xylenol _from and thus reduces its efficiency.

The present invention relates to a process for the refining of 2,6-xylenol containing as impurities phenol methylation products consisting of phenol derivatives having at least one free ortho position to the phenolic hydroxyl group as well as unreacted phenol by heating with paraformaldehyde or aqueous formaldehyde, optionally in the presence of catalysts or a 2,6-xylenol-containing residue thereof introduces water vapor or or adds water and 2,6-xylenol is exhaled by water vapor.

The 2,6-xylenol from the reaction mixture or its residue is volatilized with water vapor and the distillate in the form of a vapor by cooling forms a condensate of two phases, aqueous and 2,6-xylenol. The two phases can still be separated in liquid form or after solidification of the 2,6-xylenol by cooling.

From the 2,6-xylenol water mixture, 2,6-xylenol can be extracted with an aromatic hydrocarbon such as benzene, toluene, xylene and others to obtain a solution of 2,6-xylenol in the aromatic hydrocarbon of the desired concentration. This also significantly reduces the 2,6-xylenol content of the effluent water.

If water is used instead of water vapor added to the reaction mixture or the remainder of the reaction mixture containing 2,6-xylenol, the distilled water-2,6-xylenol-containing distillate can be returned to the next reaction mixture or the remainder of the reaction mixture containing 2,6-xylenol. This avoids the discharge of waste water containing traces of 2,6-xylenol and does not require purification.

Particularly preferably in this way, the residue of 2,6-xylenol is obtained from the reaction mixture from which 2,6-xylenol has been distilled off under vacuum, but under normal vacuum distillation operating conditions, the residue of the reaction mixture still contains about 20 to 25% by weight.

2,6-xylenol to be removed by vacuum distillation is extremely difficult - and requires a substantial increase in the temperature of the reaction mixture to 180 to 200 ° C and vacuum of 4 _F 00 - 4.65 psi. By exaggerating the remainder of the reaction mixture with this residual 2,6-xylenol content (20-25%).

240 893% by weight of steam, practically all 2,6-xylenol can be obtained and, depending on the time of steaming, a distillation residue containing less than 1% by weight of 2,6-xylenol.

If necessary, from aromatic hydrocarbon solutions

2,6-xylenol is isolated by distillation.

The following examples illustrate the invention. % in the examples are by weight.

Example 1

To a 1.500 ml sulfonation flask equipped with a stirrer, a thermometer and a reflux condenser was charged 1.002 g 2,6-xylenol containing 4.63% impurities, 20 g paraformaldehyde, g zinc stearate, and the mixture was heated at reflux for 3 hours. Water vapor is then introduced into the reaction mixture and the mixture of chemically refined 2,6-xylenol together with water vapor is collected through a condenser into a flask in which 900 g of toluene is introduced. After shaking the mixture, 1.890 g of a 2,6-xylenol toluene solution containing 902 g of 2,6-xylenol containing 0.4% impurities are obtained.

Example 2

The procedure of Example 1 is followed, except that water is admitted to the reaction mixture while stirring and boiling instead of introducing water vapor.

An equal amount of 2,6-xylenol toluene solution is obtained containing the same amount of 2,6-xylenol with the same impurity content. Example 3

Following the procedure of Example 2, only the flask into which the 2,6-xylenol-water mixture was collected and the toluene-free mixture was finally cooled, the resulting 2,6-xylenol was separated and the water was used again for the next repeated operation. The precipitated 2,6-xylenol is then treated with toluene according to Example 1. An equal amount of toluene solution of 2,6-xylenol with the same impurity content is obtained.

Example 4

The procedure of Example 1 was followed, but only after heating the reaction mixture for 3 hours, 2,6-xylenol was distilled off in vacuo to a content of 23% of 2,6-xylenol in the distillation residue. Thereafter, the distillation residue is steam-treated to give an equal total amount of toluene solution of 2,6-xylenol with the same impurity content.

Example 5 240 893

The procedure of Example 4 is followed, except that water is added gradually to the distillation residue at a temperature of 16 ° C. An equal amount of toluene solution of 2,6-xylenol with the same impurity content is obtained.

Example 6

The procedure of Example 1 was followed, using 263 g of a 37% aqueous formaldehyde solution instead of paraformaldehyde. An equal amount of toluene solution of 2,6-xylenol with the same impurity content is obtained.

Example 7

The procedure of Example 1 was followed except that the same amount of benzene was used instead of toluene. An equal amount of benzene solution of 2,6-xylenol with the same impurity content is obtained.

Claims (1)

SUBJECT OF THE INVENTION 240 893 Process for refining 2,6-xylenol containing as impurities methylene phenol products consisting of phenol derivatives having at least one free ortho-position to the phenolic hydroxyl group as well as unreacted phenol by heating with paraformaldehyde or aqueous formaldehyde solution, optionally in the presence of catalysts, characterized in that The reaction mixture or a residue thereof still containing 2,6-xylenol is introduced with water vapor and / or water, and the 2,6-xylenol is overflowed with water vapor.