DE2717371A1 - Fluid sodium or potassium phenyl-glycine salt prepn. - by saponifying nitrile deriv. with mother liquors from alkali hydroxide and amide melts - Google Patents

Abstract

Fluid alkyl metal salts of phenylglycine and of phenylglycine-o-carboxylic acid are prepd. by (a) the stepwise saponification of the corresponding nitriles with aq. alkaline waste mother liquors, in the presence of aniline, at between 50 degrees C and b.pt. and (b) evaporation of the reaction mixt. The mother liquors are obtd. from alkali hydroxide/alkali amide melts and contain (by wt. wrt mother liquor) 7-30% NaOH/KOH mixt., 20% Na2CO3/K2CO3 and opt. 10% other components, in addition to smaller quantities of coloured components and organic decompsn. prods. The phenylglycine salt is used as the raw material for indigo prepn. Fluid, mixed phenylglycine salts are obtd. which form less dust in use than Na salts, prepd. by saponifying with NaOH solutions. Use of waste solutions reduces environmental pollution.

Description

Process for the production of free-flowing alkali metal salts

of phenylglycine and phenylglycine-o-carboxylic acid The invention relates to a process for the production of free-flowing alkali metal salts Phelylglycins and the phenylglycine-o-carboxylic acid by stepwise saponification of the corresponding dinitriles with waste mother liquors.

Phenylglycine salt is the starting material for the production of indigo. The salts are according to the information in the DT-PS 120 105 or in BIOS Final Report NrO 986, page 312 or GB-PS 1 119 256 by saponification of phenylglycine nitrile made with aqueous alkali hydroxide. Because the phenylglycine salt is out of solution must be isolated by evaporation to dryness, is used as alkali hydroxide usually 50 Ges .; Alkali hydroxide solutions.

It has now been found that free-flowing alkali salts of phenylglycine can be used or the phenylglycine-o-carboxylic acid by stepwise saponification of the corresponding Nitriles with aqueous alkaline solutions in the presence of aniline at temperatures between 500C and the boiling point and evaporation of the reaction mixture obtained when mother liquors are used for the saponification, in the case of alkali hydroxide / alkali amide melts incurred and the - based on the mother liquor - 7 to 30 wt.% sodium / potassium hydroxide mixture, up to 20% sodium / potassium carbonate and possibly up to 10 genes; Further Components in addition to smaller amounts of colored components and organic decomposition products contain.

As mother liquors occurring in alkali hydroxide / alkali amide melts, comes mainly after the oxidation of the indoxyl to indigo during the separation of the indigo formed and that of the production of 2,4-dioxyquinoline resulting mother liquor into consideration.

The mother liquor produced during the production of indigo is due to flavindine dyes yellow or colored green by decomposition products as indoxyls. The ones involved in the production of dioxyquinoline Waste liquor produced contains decomposition products and saponification products from the manufacture used N-acetylanthranilic acid.

These waste eyes usually contain 7 to 30% by weight of sodium / Potassium hydroxide, up to 20% by weight of carbonate, and optionally up to 10 total; Anthranilic acid or dioxyquinoline as further components, also metal oxides such as Iron oxide (the contents refer to the waste eye). Also included these waste eyes still have smaller amounts of colored ingredients and organic Decomposition products.

Since the waste eyes contain a mixture of sodium and potassium hydroxide, when isolating the saponification products, corresponding mixed salts are obtained Phenylglycine. Such mixed salts have advantages in the sodium-potassium hydroxide-sodium amide melt according to Heumann-Pfleger for the production of indigo. Since these melts also after the By adding the phenylglycine mixed salt, the amount of potassium / sodium hydroxide can remain fluid can be reduced by 10 to 15% in the melt.

The saponification of the Phenylglycinnitril can both with the stoichiometric required amount of alkali hydroxide, or with a 0.1 to 10 win under- or excess alkali hydroxide of the waste liquor. In the case of the With an excess of hydroxide, part of the saponification takes place through the alkali metal carbonate present.

Whether an excess of alkali hydroxide, the stoichiometrically required Amount or alkali hydroxide is used in deficit, depends on the material, from which the saponification kettle consists.

The saponification is carried out in an iron apparatus with an excess carry out from 0.1 to 10, preferably from 4 to 7% of alkali hydroxide. At a Insufficient alkali metal hydroxide are formed during saponification Carbaminates from the ammonia released during saponification, which are strong against iron have a corrosive effect. In contrast, stainless steel is not attacked, so that in stainless steel apparatus, the saponification of the phenylglycine nitrile with a deficit of alkali metal hydroxide can be carried out.

The process is generally carried out so that the phenylglycine nitrile is entered in the form of the solution in aniline in the waste liquor and the saponification is started initially at 40 to 700C. After an hour at this temperature the reaction mixture is then heated to boiling until all the nitrile has been saponified. The saponification takes place according to the information in GB-PS 1 119 256. After Cooling, the aniline is extracted with toluene and the aqueous phenylglycine salt solution evaporated to dryness in the usual way.

The phenylglycine mixed salt obtained by the process according to the invention dusts considerably less than that obtained by saponification with pure sodium hydroxide solution Sodium salt. In addition, the mixed salt obtained by the process according to the invention is excellent free-flowing, which is why this salt is easy to dose into the melt leaves.

In addition, the inventive method because of the recovery of Waste eyes have great environmental benefits.

The process of the invention is illustrated by the following examples further explained Example 1 2,487 kg of phenylglycine nitrile, which is converted into 2,100 kg of aniline is dissolved, 1 mother liquor from indigo production is introduced into 3,990.

The mother liquor contains 1,000 kg of sodium-potassium hydroxide mixture, 120 kg of soda and 10 kg of anthranilic acid. The nitrile becomes accordingly example 1 of GB-PS 1 119 256 initially stirred for 1 hour at 50 ° to 650 ° C., with some of the nitrile is saponified. Then the saponification is completed at the boiling point guided. Duration: 5 hours.

After cooling to room temperature, the phenylglycine salt solution extracted with toluene to remove the aniline and the aqueous solution to dryness evaporated.

Yield 30464 kg of sodium / potassium salt of phenylglycine.

Purity: 94.5.9 The yield is: 96; the theories example 2 The procedure is as in Example 1 with the difference that for saponification the Mother liquor from the 2,4-dioxyquinoline production used for the saponification of 2o487 phenylglycine nitrile become 3,200 l of the red-brown colored mother liquor, d = 1.26, used where 050 kg of sodium-potassium hydroxide mixture, 100 kg of soda, 25 kg Alkali salts of anthranilic acid, 3 kg alkali salts of 2,4-dioxyquinoline and 1 kg Contains aniline in addition to staining impurities.

The work-up is carried out as in Example 1. The same is obtained Yield as in Example 1 with the difference that the phenylglycine salt is somewhat has more yellow color, the quality of the salt mixture is the same as in the salt mixture obtained according to Example 1.

Claims (1)

Claim process for the production of free-flowing alkali salts of phenylglycine and phenylglycine-o-carboxylic acid through stepwise saponification the corresponding nitriles with aqueous alkaline solutions in the presence of aniline Temperatures between 50 ° C and the boiling point and evaporation of the reaction mixture, characterized in that mother liquors are used for the saponification, which at Alkali hydroxide / alkali amide melts are incurred and - based on the mother liquor - 7 to 30% by weight sodium / potassium hydroxide mixture, up to 20% by weight sodium / potassium carbonate and optionally up to 10% by weight of further constituents in addition to smaller amounts Contains colored components and organic decomposition products.