CS250949B1 - A method for recovering mother liquors after oxidative polycondensation of 2,6-xylenol - Google Patents

Abstract

The solution relates to a method for the regeneration of copper after oxidative polymerization of 2,6-xylenol. Mother liquors containing polyphenylene oxide oligomers, aromatic solvent, alcohol amines and copper chlorides are extracted with an extractant insoluble in aromatic hydrocarbons and both phases, heavy polar and light non-polar, are treated by evaporation.

Description

The invention relates to a process for the recovery of copper from mother liquors after oxidative polymerization of 2,6-xylenol and isolation of polyphenylene oxide.

In the oxidative polycondensation of 2,6-xylenol to polyphenylene oxide (PFO), the catalytic system used has the greatest influence among many factors. Therefore, the prevalence of attention in the study of the course of catalytic oxidation is devoted to the selection of catalyst complexing agents. Catalyst systems based on monovalent copper salts and tertiary amines, complexes of monovalent copper compounds with primary or secondary amines, divalent copper compounds with tertiary amines and divalent copper compounds with primary or secondary single alkylamines or ammonia have been proposed.

In technical practice, the polymerization medium for the oxidative polymerization of 2,6-xylenol consists of a mixture of an aromatic hydrocarbon with an alcohol, for example benzene or toluene, in combination with ethyl alcohol or methanol. The most commonly used catalyst system is a copper (II) or copper (I) chloride complex with an amine such as morpholine, cyclohexylamine and the like.

The precipitated polymer (polyphenylene oxide - PFO) is usually isolated from the polymerization medium by filtration. The filtrate (mother liquors) containing the oligomers of PFO, aromatic hydrocarbon, alcohol, cuprous or cuprous chloride with amine is then subjected to separate processing.

The treatment of the mother liquor filtrates so far consists in injecting them into a film rotary evaporator or other type of evaporator and separating all volatile fractions on suitable rectification columns and returning them for reuse. A mixture of oligomers and the decomposition products of the catalyst system remains in or out of the continuously working evaporator. In order to improve the flow properties of the effluents, liquefiers, for example, oil, which is part of the feed of the mother liquor into the evaporator, are sometimes added.

Isolation of copper from the evaporator thus obtained is very demanding and uneconomical. The possibility of practical use of this evaporator, especially if it contains a liquefying agent, is very problematic and, in terms of quantity, represents a significant economic item.

SUMMARY OF THE INVENTION The present invention provides a process for the regeneration of mother liquors after oxidative polycondensation of 2,6-xylenol catalyzed by copper-amine complexes containing aromatic hydrocarbons, alcohols and alkanolamines. hydrocarbons such as water, ethylene glycol, glycerin, monoethanolamine, diethanolamine and the phases obtained, heavy polar and light non-polar, are treated by evaporation.

The regeneration process of the present invention results in two phases, a light phase comprising toluene or benzene together with a low molecular weight moiety - polyphenylene oxide oligomers and a heavy phase consisting of a polar compound containing an alcohol and a copper or cupric chloride complex with an amine. The lower layer is concentrated by distillation and the separated copper metal is isolated by filtration or decantation. In this way, copper recovery is practically quantitative.

Of the aromatic hydrocarbons, benzene or toluene are most commonly used. Always mixed with ethanol or methanol.

The composition of the mother liquor is approximately: 40 to 45% by volume of the aromatic hydrocarbon, 55 to 60% by volume of alcohol, 0.5 to 2.0% by volume of water, 0.5 to 2.5% by volume of amines and 0.05 to 5% by weight of chloride copper or copper.

Of the polar compounds, water, ethylene glycol, glycerine, monoethanolamine, diethanolamine, i.e. water-soluble but insoluble in benzene or toluene, are suitable for extraction. Polar compounds disperse with mother liquors extract alcohol and cuprous and cuprous chloride or amines from them and form two phases from the system - light hydrocarbon and heavy, containing almost quantitatively a copper-amine complex.

Separation of the heavy layer and its thickening - distillation of alcohol and amine leads to the excretion of copper in metallic form practically in quantitative amount (by decomposition of the complex), which is then isolated by sedimentation or filtration.

The advantage of this process is that the copper used in the form of cuprous chloride or cuprous chloride hydrate is obtained in a process for the recovery of solvents in metallic form in virtually quantitative yield, pure, free from oligomers.

In addition to the discontinuously operating extractors, continuous countercurrent extractors coupled to separators may also be advantageously used.

The bottom layer can be concentrated by distilling off the volatiles at atmospheric pressure or even under vacuum. Continuously operating evaporators can also be used.

A further advantage of this process is the possibility of treating the light toluene or benzene phases on a film rotary evaporator without the use of liquefiers and obtaining a mixture of oligomers with copper-free p-diphenoquinone as secondary raw materials for various organic synthesis purposes and thereby organizing PFO production as waste.

Claims (1)

EXAMPLE 7 The procedure of Example 1 was followed except that the mother liquors contained the same amount of benzene instead of toluene and the same amount of ethyl alcohol instead of methanol. The same amount of copper is obtained. EXAMPLE 8 The procedure of Example 1 was followed except that the mother liquors contained the same amount of cyclohexylamine instead of morpholine. The same amount of copper is obtained. OBJECT OF THE INVENTION Process for regenerating mother liquors after oxidative polycondensation of 2,6-xylenol with copper complexes with amines containing aromatic hydrocarbons, alcohols and alkanolamines, characterized in that the mother liquors are subjected to liquid extraction using an insoluble extraction agent in aromatic hydrocarbons such as water, ethylene glycol, glycerin, monoethanolamine, diethanolamine and the obtained phases, heavy polar and light nonpolar, are subjected to evaporation. Severógrafia, n. P., MOST Price 2,40 Kcs