CS235679B1 - Method of technical 2,6-xylenol's chemical refining - Google Patents

Abstract

The invention relates to chemical scrubbing 2.6 xylenol from other alkylation products phenol. 2.6 xylenol is heated with formaldehyde or paraformaldehyde in the presence metal oxides outside alkaline metals soils and metal organic salts carboxylic acids, then water a unreacted formaldehyde decompose.

Description

The invention relates to a process for the chemical purification (refining) of crude 2,6-xylenol by heating it with paraformaldehyde or aqueous formaldehyde solution.

It is known that 2,6-xylelon is used to prepare polyphenoxide. A certain degree of purity is required for its polymerization.

The source of 2,6-xylonol is a phenol methylation reaction mixture containing predominantly methylphenols (e-, m- and p-cresels), di- and trimethylphenols. To a lesser extent, irrelevant from a quantitative point of view, also other phenol methylation products.

Depending on the reaction conditions of the methylation of the phenol, the reaction mixture contains a different ratio of o-cresol and 2,6-xylenol, depending on whether the main methylation product is to be o-cresel 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 derivative of the phenol, the individual o-, m- and p-cresols constitute 00-96% by weight of impurities.

From this mixture, 2,6-xylenol has been isolated and isolated by physical procedures such as rectification, crystallization, and respec. fractional crystallization, or a combination thereof.

All these processes are characterized by being very energy intensive, time consuming and requiring complex and costly equipment.

Chemical refining can be successfully carried out

2.6-xylenol by heating it with paraformaldehyde in the presence of Cs fatty acid salts. or with an aqueous solution of formaldehyde in the presence of the same Cs salts. 260842, or metal oxide (excluding alkali metal oxide) according to

Cs. of the author's certificate 252 834.

The present invention provides a process for the chemical refining of technical 2,6-xylenol containing, as impurities, other phenol methylation products as well as unreacted phenol having at least one free ortho position relative to the phenolic OH group by heating with paraformaldehyde in an amount of 5 to 200% by weight % by weight of impurities or with an aqueous formaldehyde solution in an amount of 10 to 500% by weight of formaldehyde

- 2. 235 679 impurities in the presence of metal oxides, other than alkali metal oxides, metal salts of organic carboxylic acids, in an amount of 0,01 to 50% by weight per technical xylenol used, in which the reaction is carried out in the presence of a catalytic system containing a mixture of metal oxides, except for alkali metals and metal salts of organic carboxylic acids in a ratio ensuring stabilization of the concentration of hydrogen ions in the range of pH 4 to 7.

The reaction of phenol with an aqueous formaldehyde solution takes place when the reaction mixture boils only in the presence of catalysts. At pH 4-7 of the reaction mixture and the use of a salt of, for example, zinc, magnesium, aluminum, manganese, cadmium, cobalt, lead, chromium, nickel and copper, mainly o-o'-isomers are formed. An excess of 15 to 30% by weight of ol leads almost exclusively to the o-o structure of the reaction products. Traces of acids give rise to β-β-isomers. As the pH of the reaction mixture increases (above pH 7), the selectivity of the ortho-condensation decreases, and the efficiency and yield of the refining of 2,6-xylenol also decreases.

The reaction products, in particular the impurities of phenolic cheracter with paraformaldehyde or aqueous formaldehyde solution, are characterized by a higher molecular weight. In the distillation of refined

2,6-xylenol does not flow with it and remains in the distillation residue.

The amount of paraformaldehyde used depends on the content of phenolic impurities. Usually it does not exceed the content of impurities by weight. Their substantial decrease also occurs with 25 to 50% by weight of this amount of paraformaldehyde.

The amount of aqueous formaldehyde used also depends on the content of phenolic impurities. As a rule, it does not exceed five times the impurity content (calculated on the anhydrous 100% formaldehyde). A smaller excess of formaldehyde requires longer reaction times. The concentration of aqueous formaldehyde solutions of commercial type is generally 36 to 40% by weight. However, other concentrations, preferably higher, or a mixture of aqueous formaldehyde with paraformaldehyde may also be used.

Of the metal oxides, other than alkaline, the most suitable oxides are: zinc, magnesium, aluminum, manganese, cadmium, lead, cobalt, chromium, nickel, copper or copper.

Of the organic carboxylic acid salts, the salts of the abovementioned oxides of the most readily available acids, such as acetic acid, lauric acid, stearic acid, oleic acid, citric acid, benzoic acid, phthalic acid, methacrylic acid and others are particularly suitable.

235 679 ”3“

The most suitable temperature for the chemical separation of industrial 2,6-xylenol with paraformaldehyde or aqueous formaldehyde is the boiling point of the reaction mixture. For paraformaldehyde, the boiling point of the reaction mixture depends on the impurity content and is in the range of 115 ° C to 175 ° C.

After distilling off the water and unreacted formaldehyde from the reaction mixture, the pre-distilled 2,6-xylene x is almost completely free of the above impurities, phenol derivatives containing at least one free ortho position relative to the phenolic OH group.

Compared to the same processes, but using separate salts of organic carboxylic acids ₉ of metal oxides other than alkaline metals, the reaction conditions can be adjusted to achieve the greatest effect of the refining process by using mixtures based on the different content and composition of the above-described impurities.

Another advantage of the use of a mixture of selective catalysts supporting the reaction of paraformaldehyde or formaldehyde solution, especially with the free ortho-position of the phenolic core, is the modification of the properties of the distillation residue according to further processing needs.

Characteristic features of this new process for the purification of technical 2,6-xylenol are the simplicity and speed of execution, the simplicity and the low-cost production equipment with considerable energy savings.

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

Example 1

In a 500 ml three-necked flask equipped with a stirrer, a thermometer and a reflux condenser, 305 g of industrial 2,6-xylenol containing 5.5% of other phenol methylderivatives resulting from methylation of phenol, 7 g of paraformaldehyde, 2.5 g of zinc oxide and 1, 5 g of cupric oxide. The mixture is heated to boiling for 4 hours. The reaction water was then distilled off and the 2,6-xylenol was distilled off under vacuum. 280 g of 2,6-xyl-phenyl of 0.7% impurity are obtained.

Example 2

The procedure of Example 1 was followed, except that the same amount of titanium dioxide was used instead of copper oxide. 284 g of 2,6-xylenol having an impurity content of 1.2% are obtained.

Example 3

The procedure is as described in Example 1, but the technical 2,6-xylenol used contains 16% impurities, paraformaldehyde is used 20 g

- * r 235 679 and the same amount of alumina is used instead of muscular oxide. 233 g of 2,6-xylenol with 1.3% impurity content are obtained.

Example 4

The procedure of Example 3 was followed, except that the same amount of calcium oxide was used instead of zinc oxide. It is obtained

236 g of 2,6-xylenol containing 1.7% impurities.

Example 5

The procedure of Example 3 was followed, except that the same amount of magnesium oxide was used instead of zinc oxide. It is obtained

237 g of 2,6-xylenol containing 2.3% impurities.

Example 6

The procedure of Example 3 is followed, except that only 2 g of zinc acetate are added to the zinc and alumina oxides. 231 g of 2,6-xyleneol having a content of 0.4% of impurities are obtained.

Example 7

The procedure of Example 3 was followed except that an equal amount of zinc acetate was used instead of alumina. 230 g of 2,6-xylenol are obtained with a content of 0.3% impurities.

Example 8

The procedure of Example 3 is followed, except that a mixture of 2 g of zinc acetate and 3 g of zinc stearate is used instead of zinc oxide. 229 g of 2,6-xylenol are obtained having a content of 0.2% impurities.

Example 9 ^Λ

The procedure of Example 3 is followed, except that a mixture of 2 g of copper acetate and 3 g of lithium laurate is used instead of zinc oxide. 230 g of 2,6-xylepol with 0.5% impurity content are obtained.

Example 10

The procedure of Example 3 was followed, except that a mixture of 1 g of magnesium oxide and 2 g of zinc acetate was used instead of alumina. 233 g of 2,6-xylenol having a content of 0.5% impurities were obtained. Example 11

Proceed as in Example 1, using only 50 ml of 37% aqueous formaldehyde instead of paraformaldehyde, 4 g of zinc stearate is used instead of copper oxide, the reaction mixture is heated at boiling for 6 hours and 260 g of unreacted formaldehyde are distilled off. 6-xylenol containing 0.8% impurities.

- 5 Example 12

235 679

The procedure of Example 11 is followed, but only 2 g of secondary sodium citrate and 1 g of secondary potassium phthalate are added to the mixture of zinc oxide and zinc stearate. 258 g of 2,6-xylenel with 0.4% impurity content are obtained.

Example 13

Following the procedure of Example 11, only 70 ml of an aqueous formaldehyde solution, 0.2 g of zinc oxide and 0.1 g of zinc acetate were used. 265 g of 2,6-xylenol were obtained with a content of 1.3% impurities.

Example 14

The procedure of Example 1 is followed, except that 10 g of paraformaldehyde is used, and zinc stearate is used instead of zinc and copper oxide. 278 g of 2,6-xylenol are obtained having a content of 0.2% impurities.

Example 15

The procedure of Example 14 was followed, except that 600 g of a 37% aqueous formaldehyde solution was used instead of paraformaldehyde. 259 g of 2,6-xylenol are obtained having a content of 0.2% impurities.

Claims (1)

The chemical refining process of the technical 2,6-xylenols comprises, as impurities, other phenol methylation products as well as unreacted phenol having at least one free ortho position relative to the phenolic OH group, by heating with paraformaldehyde in an amount of 5 to 20% by weight by weight of impurities or a formaldehyde aqueous solution in an amount of 10 to 500% by weight of formaldehyde per weight of impurities, in the presence of metal oxides, excluding alkali metal oxides, metal salts of organic carboxylic acids, in an amount of 0,01 to 50% by weight for the technical xylenol used characterized in that the reaction is carried out in the presence of a catalytic system comprising a mixture of metal oxides, other than alkali metals and metal salts of organic carboxylic acids, in a ratio ensuring stabilization of the concentration of hydrogen ions in the range of pH 4 to 7;