CS236128B1 - Method of 2,6-xylenol refining - Google Patents

Abstract

The invention relates to the purification of 2,6-xylenol from other ortho-position phenols. Crude 2,6-xylenol is heated under pressure at 140-190 ° C with paraformaldehyde in an amount of 5 to 200 wt weight of impurities and after distillation of the reaction water is 2,6-xylenol from the reaction mixture is isolated by distillation, pure 2,6-xylenol is useful as an intermediate in manufacture plastics, dyes and stabilizers.

Description

The present invention relates to a process for the chemical purification of 2,6-xylenol to be used as an intermediate in the manufacture of plastics * dyes and stabilizers *

The source of 2,6-xylenol is a phenol methylation reaction mixture containing predominantly methylphenols (o- »m- and p-cresols), di- and trimethylphenols. To a lesser extent, from the quantitative point of view, other phenol methylation products are irrelevant * According to the reaction conditions of the phenol methylation, the reaction mixture contains a different ratio of o-cresol and 2,6-xylenol. 6-xylenol * 2,6-xylenol remains the major and most important component of the reaction mixture after the o-cresol has been distilled off. O-, m- and p-cresols alone account for up to 95% of other phenol methyl derivatives

Until now, 2,6-xylenol has been isolated from this mixture and isolated by physical processes such as rectification, crystallization, fractional crystallization, or a combination thereof * All of these processes are characterized by * very energy intensive * lengthy and require 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 present invention provides a process for refining 2,6-xylenol containing, as impurities in varying proportions, 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, characterized in that The above phenolic mixture heated in a pressure vessel at 140 to 190 ° C by β paraformaldehyde in an amount of 5 to 200% by weight of impurities and after distilling off the reaction water ee 2,6-xylenol is isolated from the reaction mixture by distillation *

- 2 236 128

By-products) accompanying 2,6-xylenol, phenol derivatives having at least one free o-position relative to the phenolic OH-group can be virtually eliminated by heating this mixture with paraforraaldehyde at elevated pressure at temperatures of 140 to 190 ° C · The amount of paraformaldehyde used depends on the impurity content of phenolic character · Oako effective amount can be used 5 to 200% w / w paraformaldehyde content of above mentioned impurities · Use of larger amount of paraformaldehyde is uneconomical · The most effective amount is 20 to 60% w / w impurity content · Best temperature is usually 170 to 180 ° C pressure in the pressure reaction vessel arises spontaneously by depolymerization of paraformaldehyde and evaporation of lower-boiling substances ·

A characteristic feature of this new process for the purification of technical 2,6-xylenol is the simplicity and speed of manufacture, the simplicity and the low-cost of production equipment with considerable energy savings.

Another advantage of this process is that it works without catalysts, which do not have to be removed after cleaning.

In comparison with the same process carried out at atmospheric pressure, a higher refining efficiency is achieved in this case.

The following examples illustrate the invention ^ (% in the examples are by weight) ·

Example 1

To a 500 ml metal autoclave equipped with a stirrer and a thermometer, 305 g of industrial 2,6-xylenol containing 12% of other phenol methyl derivatives (resulting from phenol methylation) are added and 10.2 g of paraformaldehyde are added. ° C, then drained, the reaction water distilled off and 2,6-xylenol distilled off ·

254 g of 2,6-xylenol are obtained having a content of 0.5% impurities.

Example 2

The procedure of Example 1 is followed using only half the amount (5.1 g) of paraformaldehyde.

It yields 266 g of 2,6-xylenol with a content of 1.1% impurities ·

Example 3

Following the procedure of Example 1, only paraform _and ldehyde were used, 1.9 g.

294 g of 2,6-xylenol are obtained with a content of 8.5% impurities.

- 3 Example 4 236 ΐ2β

The procedure was as in Example 1 except that 36.6 g of paraformaldehyde was used.

245 g of 2,6-xylenol are obtained with a content of 0,2% impurities ·

Example 5

Proceed as in Example 1, except that the technical 2,6-xylenol used contains 6% impurities and paraformaldehyde is used 36 g ·

234 g of 2,6-xylenol containing 0,1% impurities are obtained.

Example 6

The procedure of Example 5 was followed, except that the reaction mixture was heated to 140 ° C.

An equal amount of 2,6-xylenol with 0.4% impurity content is obtained

The procedure of Example 1 was followed, except that the reaction mixture was heated to 190 ° C.

250 g of 2,6-xylenol are obtained with a content of 0,4% impurities ·

Claims (1)

SUBJECT OF THE INVENTION 236 128 i. Process for refining 2,6-xylenol _from impurities of 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, characterized in that the aforementioned mixture of phenolic substances is heated in a pressure vessel at a temperature of 140 to 190 ° C with paraformaldehyde in an amount of 5 to 200% by weight of impurities, and after distilling off the reaction water, 2,6-xylenol is isolated from the reaction mixture by distillation.