CN1057996C

CN1057996C - N-phenyl-acetate preparing process

Info

Publication number: CN1057996C
Application number: CN97104054A
Authority: CN
Inventors: 李明威
Original assignee: Individual
Current assignee: Individual
Priority date: 1997-04-23
Filing date: 1997-04-23
Publication date: 2000-11-01
Anticipated expiration: 2017-04-23
Also published as: CN1197061A

Abstract

The present inventions relates to a new technology for preparing an intermediate (N-phenyl acetate) of a synthetic dye (indigo), which belongs to the field of refining chemical industry. In the present invention, aniline, sodium cyanide and formaldehyde are used to generate N-phenylacetonitrile under the existence of magnesium salts (magnesium chloride or magnesium sulfate), and then the N-phenylacetonitrile is used to prepare N-phenyl acetate by alkaline hydrolysis. The present invention has the advantages of high yield, low cost and no pollution.

Description

Process for preparing N-phenylamino acetate

The invention relates to a new process for preparing an intermediate of synthetic dye Indigo (for dyeing denim), namely N-phenylamino acetate (N-phenylglycine), and belongs to the field of fine chemical engineering.

N-phenylamino acetate is also called phenylglycinate, is an important intermediate for synthesizing indigo, and the annual domestic dosage exceeds 1 million tons. The existing production process comprises the following steps:

1. german method (BIOS 986, PB77764) comprises mixing 100% excess aniline with formaldehyde and sodium cyanide, introducing carbon dioxide under pressure, reacting at 85-90 deg.C to obtain phenylaminoacetonitrile (also known as omega cyanomethylaniline) and sodium bicarbonate, separating oily nitriloamine mixture, and hydrolyzing with aqueous solution of caustic alkali at 110 deg.C to obtain N-phenylaminoacetate. The product purity is high, and the theoretical yield is 95-96%. The disadvantages are excessive aniline, complex recovery process and generation of waste liquid containing sodium bicarbonate.

2. British patent method (Brit 1119256) comprises reacting aniline 30-50% in excess with 47% hydroxy acetonitrile water solution at 100 ℃ and 110 ℃ to produce phenylaminoacetonitrile, cooling, adding caustic alkali water solution, heating to boil, and hydrolyzing. Extracting the surplus aniline with pure benzene to obtain N-phenylamino acetate. The theoretical yield is 96.3-97.0%. Its advantages are simple operation, high output rate and no generation of waste water. The disadvantages are that the raw material of the hydroxyacetonitrile is not easy to obtain and is unstable in storage and transportation.

3. The presorted method (Amitoff, the chemistry and technology of intermediate and dye) takes aniline, monochloroacetic acid, sodium hydroxide and ferrous sulfate to react, firstly generates ferrous N-phenylaminoacetate precipitate, then carries out double decomposition with caustic alkali solution after filtration and washing, separates out dilute N-phenylaminoacetate solution, and finally concentrates. The process has low yield of about 70-80%, and produces a large amount of waste water containing sodium chloride and ferric salt and a large amount of iron mud, so the pollution is serious.

The invention aims to overcome the defects of the existing production process and provides a pollution-free production process method of N-phenylamino acetate, which is simple and convenient to manufacture.

The content of the invention is as follows: aniline, formaldehyde, sodium cyanide and magnesium salt (magnesium chloride or magnesium sulfate) are reacted in the presence of a phase transfer catalyst to obtain phenylaminoacetonitrile: then adding hydrochloric acid for neutralization to neutrality:

and (3) separating out a water phase after standing, wherein the water phase contains magnesium chloride and sodium chloride, and recovering the magnesium chloride for recycling after evaporation and concentration. The phenylaminoacetonitrile is hydrolyzed with caustic solution by routine method to obtain N-phenylaminoacetate. The yield is about 100 percent by sodium cyanide and is more than or equal to 98 percent by aniline.

The molar ratio of aniline, formaldehyde, sodium cyanide and magnesium salt is 1.00-1.10: 1.00-1.05: 0.95-1.00: 0.45-0.5, and the reaction temperature is 80-100 ℃.

The molar ratio of the phenylaminoacetonitrile to the caustic alkali is 1.00: 1.05-1.10, and the hydrolysis temperature is 100 ℃ and 110 ℃ (or kept boiling).

The phase transfer catalyst is used in 0.02-0.05 mol/mol aniline, and may be quaternary ammonium type, crown ether type or polyethylene glycol.

Summarizing the invention: the process for preparing N-phenylamino acetate is characterized by that under the existance of magnesium salt (magnesium chloride or magnesium sulfate), aniline, sodium cyanide and formaldehyde are used to produce N-phenylamino acetonitrile, then alkaline hydrolysis is carried out to obtain N-phenylaminoacetate, that is, when N-phenylamino acetonitrile and N-phenylamino acetate or one of them is produced, the magnesium salt is added.

The invention has the advantages and effects that: the new process has high yield, low cost, no three wastes, 40-50% lower material cost than available process, and no harmful waste water and waste slag.

Two examples are given below:

example 1: 99 g of technical-grade aniline is taken and stirred, phase transfer catalyst and 163.5 g of 30% sodium cyanide aqueous solution are added, after the addition, the temperature is kept between 20 and 30 ℃, and solution prepared by 85 g of 37% formaldehyde, 106 g of magnesium chloride and 50 to 100 ml of water is slowly added. After the addition, the temperature is raised to 50-60 ℃, the reaction is carried out for 2 hours under the condition of heat preservation, and then the temperature is raised to 80-90 ℃, the reaction is carried out for 1 hour until the end point is reached. The reaction is completed, the reaction is cooled to 40-50 ℃ under stirring, 120-125 g of 30% hydrochloric acid is slowly added until the pH value is 6.0-6.5, and simultaneously, the water is correspondingly clear and transparent until no suspended magnesium hydroxide is precipitated. Standing for layering, and carefully separating out oily substances, namely the phenylaminoacetonitrile, wherein the weight of the phenylaminoacetonitrile is about 135-140 g, and the yield of the phenylamine is more than or equal to 98%. (NaCN conversion 100%).

Example 2: 60.5 g of 93% caustic potash was dissolved in 100 ml of water, and 135-140 g of fresh phenylaminoacetonitrile oil was added with stirring, and the mixture was kept boiling and hydrolyzed until no ammonia gas was generated. Cooling and solidifying to obtain the N-phenylamino potassium acetate with theyield of about 100 percent.

Claims

1. The manufacturing process of the N-phenylamino acetate is characterized in that: in the presence of a phase transfer catalyst, aniline, formaldehyde, sodium cyanide and magnesium chloride are reacted to obtain phenylaminoacetonitrile: then adding hydrochloric acid for neutralization to neutrality:

standing, separating out a water phase containing magnesium chloride and sodium chloride, evaporating and concentrating, and recovering magnesium chloride for recycling; the phenylaminoacetonitrile is hydrolyzed with caustic alkali solution by a routine method to finally obtain N-phenylaminoacetate,

the mol ratio of aniline, formaldehyde, sodium cyanide and magnesium chloride is 1.00-1.10: 1.00-1.05: 0.95-1.00: 0.45-0.50, and the reaction temperature is 80-100 ℃;

the mol ratio of the phenylaminoacetonitrile to the caustic alkali is 1.00: 1.05-1.10, and the hydrolysis temperature is 100-;

the dosage of the phase transfer catalyst is 0.02-0.05 mol per mol of aniline, and quaternary ammonium type, crown ether type or polyethylene glycol is adopted.