Methods for obtaining adipic acid. Obtaining adipic acid

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Adipic acid (Adipic acid, hexanedioic acid, 1,4-butanedicarboxylic acid) - belongs to the family of dibasic limiting carboxylic acids. It has good solubility in ethanol, and also limited solubility in ether, but hardly soluble in water. However, most of the salts (adipinates) formed by adipic acid are soluble in water. When dehydrated, adipinates are converted to adipamides. Adipic acid has all the chemical properties characteristic of the carboxylic acid family. It reacts with glycols to form polyesters.

Externally adipic acid is white or colorless crystalline substance with a density of approximately 1.36 g / cc. The melting point of adipic acid is about 153 °C, the decomposition temperature is about 220 °C (±20 °C), adipic acid boils at 260 °C.

The most common general method for the synthesis of adipic acid in industry is the oxidation of cyclic compounds (cyclohexane)

GOST 10558-80 distinguishes several grades of adipic acid. The table below shows the main characteristics and their compliance with GOST standards.

Name of indicator	Norma First grade	Norma Premium	Fact by party	Fact by party

			Top grade	Top grade
Appearance		white crystalline substance	Corresponds	Corresponds
Mass fraction of adipic acid, %, not less than
Color of the solution according to the platinum-cobalt scale, un. Hazen, no more
Melting point, ºС, not lower
Mass fraction of water, %, no more
Mass fraction of ash, %, no more
Mass fraction of nitric acid, %, no more
Mass fraction of iron, %, no more

Guaranteed shelf life of adipic acid is 1 year.

We offer to pay attention to such raw materials for coatings as Adipic acid. This substance is produced in full compliance with current standards and is a high-quality component for paints and varnishes.

The main place among the raw materials for coatings is occupied by film-forming substances. They provide the main qualities of the material: its strength, durability, resistance to external influences. Various resins (alkyd, acrylate, epoxy, etc.) and aqueous dispersions of polymers (acrylic, polyurethane) most often act as film-forming agents.

Various pigments are responsible for the final color of the coating. In addition to decorative qualities, pigments can give paintwork light resistance, electrical conductivity and others beneficial features. Pigments paintwork materials are divided into inorganic (titanium dioxide, zinc oxide, ocher, etc.) and organic (anthraquinone, phthalocyanine, etc.). To reduce the cost of coatings, special additives-fillers are added to the composition. As a rule, these are substances of natural origin, which, if properly formulated, can improve the quality of the coating.

If you want to give the final coating elasticity, plasticizers (phthalates, phosphates) are added to the composition of the coatings. To speed up the drying process, desiccants are added to the paints (true - salts of carboxylic acids and promoters - salts of barium, calcium, etc.).

a) In industry, adipic acid is obtained mainly by a two-stage oxidation of cyclohexane. At the first stage (liquid-phase oxidation with air at 142-145°C and 0.7 MPa), a mixture of cyclohexanone and cyclohexanol is obtained, separated by distillation. Cyclohexanone is used to produce caprolactam. Cyclohexanol is oxidized with 40-60% HNO 3 at 55°C (NH 4 VO 3 catalyst); the yield of adipic acid is 95%.

b) oxidation of cyclohexene with ozone or HNO 3 ;

c) from THF according to the scheme:

d) carbonylation of THF to adipic anhydride, from which the acid is obtained by the action of H2O.

Production method 1. (laboratory synthesis)

In a 5-liter round-bottom flask equipped with a mechanical stirrer, a thermometer and a 1-liter separatory funnel, 2100 g (16.6 mol) of 50% nitric acid (spec. weight 1.32; in fume hood). The acid is heated almost to boiling and 1 g of ammonium vanadate is added. Start the stirrer and slowly add 500 g (5 mol) of cyclohexanol through a separating funnel. First, 40-50 drops of cyclohexanol are added and the reaction mixture is stirred until the reaction begins (4-5 min.), which becomes noticeable by the evolution of nitrogen oxides (it is very important that the oxidation begin before a significant amount of cyclohexanol is added, otherwise the reaction may become violent Reaction must be carried out in a well functioning fume hood. The reaction flask is then placed in an ice bath and the contents of the flask are cooled until the temperature of the mixture reaches 55-60°C. Thereafter, cyclohexanol is added as soon as possible, maintaining the temperature within the limits indicated above. Toward the end of the oxidation (after 475 g of cyclohexanol had been added), the ice bath was removed; sometimes the flask even has to be heated in order to maintain the required temperature and to avoid cyclization of the adipic acid.

Stirring is continued for another 1 hour after the addition of the entire amount of cyclohexanol. The mixture is then cooled to 0°C, the adipic acid is suction filtered, washed with 500 ml ice water and air dry overnight.

The output of white crystals with so pl. 146-149°C is 395-410 g. By evaporating the mother liquors, another 30-40 g of product with m.p. 141-144°C (mixed with glutaric and succinic acids). Total yield of crude adipic acid: 425-440g, or 58-60% of theoretical yield. The resulting product is reasonably pure for most purposes; however, a purer product can be obtained by recrystallization of crude adipic acid from 700 ml of concentrated nitric acid sp. weight 1.42. Losses during cleaning are about 5%. Recrystallized adipic acid melts at 151-152 C.

Notes.

1. It is suggested not to use a catalyst if the temperature of the reaction mixture, after the start of the reaction, is maintained at 85-900 (Hartman, private communication).

2. Used technical cyclohexanol, practically free of phenol. More than 90% of the product boiled between 158-1630.

3. It is very important that the oxidation begin before a significant amount of cyclohexanol is added, otherwise the reaction may become violent. The reaction must be carried out in a well-functioning fume hood.

4. Nitric acid mother liquors contain significant amounts of adipic acid mixed with glutaric and succinic acids. It turned out that the separation of these acids by crystallization is practically impractical. However, if nitric acid is removed by evaporation, and the remaining mixture of acids is esterified with ethyl alcohol, then a mixture of ethyl esters of succinic (bp. 121-1260 / 20mm), glutaric (b.p. 133-1380 / 20mm) and adipic t can be obtained bale (142-1470/20mm) acid. These esters can be successfully separated by distillation.

5. The following modified recipe may give a better outcome. In a 3-liter flask equipped with a stirrer, reflux condenser and addition funnel, fixed in asbestos stoppers impregnated with liquid glass, place 1900 ml of 50% nitric acid (1262 ml of nitric acid sp. weight 1.42, diluted to 1900 ml) and 1 g of ammonium vanadate. The flask is placed on water bath, heated to 50-600, and very slowly, with the stirrer running, 357 g (3.5 mol.) of technical cyclohexanol are added so that the bath temperature is maintained at 50-600. This operation lasts 6-8 hours. The reaction is terminated by heating the water bath to boiling until the evolution of nitrogen oxides ceases (about 1 hour). The hot reaction mixture is siphoned off and allowed to cool. Yield of crude adipic acid: 372g (72% theoretical).

Asbestos plugs impregnated with liquid glass are prepared from a thin asbestos sheet cut into strips 2.5 cm wide. The strips are moistened with a solution of liquid glass and then wound, for example, on the front of a refrigerator until a cork is obtained. right size. After assembling the device, the corks are covered with liquid glass and left to harden overnight.

6. Nitric acid mother liquors after crystallization can replace part of the fresh acid in subsequent oxidation operations.

7. Adipic acid can also be recrystallized from 2.5 times (by weight) water or 50% alcohol. However, these solvents give less satisfactory results than nitric acid.

Adipic acid (there is another name for this substance - 1,4-butanedicarboxylic acid, the systematic name is hexanedioic acid) is a limiting dibasic carboxylic acid. Has the following chemical formula: HOOC(CH2)4COOH and gross formula C6O4H10. It has the same chemical properties as carboxylic acids. Forms salts, many of which are soluble in water (H2O). It is esterified to di- and monoesters. With glycols, hexanedioic acid forms polyesters.

Properties of adipic acid

4. When adipic acid is heated, their amides are formed.

5. Under the influence of SOCl2, adipic acid is converted into the corresponding acid chloride.

Esters of adipic acid

1. Methyl adipate is used for the electrochemical synthesis of dimethyl sebacate.

2. Diallyladipate is a curing agent polyester resins.

3. Ethyl adipate is used as an additive to increase its octane number.

4. Diethyl adipate is used as a plasticizer in the production of food films, shoes, PVC, faux leather, children's toys, linoleum, stretch ceilings.

5. Diisopropyl adipate is used as an ingredient in skin cosmetics.

Adipic acid (1,4-butanedicarboxylic acid, Hexanedioic acid, e355) is a dietary supplement of the antioxidant group - a dibasic saturated carboxylic acid (a class of organic compounds whose molecules contain one or more functional carboxyl groups - COOH).

Physiochemical properties.

Gross formula: C 6 H 10 O 4 .

Structural formula:

H O O O O H

Adipic acid has all the chemical properties characteristic of carboxylic acids. Appearance: correct form white crystals or powder. Melting point 152 °C. Boiling point 337.5 °C. Density 1.36 g/cm 3 . By its action on the human body is harmless. Adipic acid forms salts, most of which are soluble in water. Adipic acid is easily esterified to mono- and diesters, and forms polyesters with glycols. Adipic acid is a colorless crystalline powder. Decomposes when heated, releasing volatile vapors of valeric acid and other substances.

Application.

As a raw material in the production of synthetic fibers (polyamides) and polyurethanes;

As a plasticizer in the production of plastics;

In the printing industry for the production of high quality paper;

In the production of esters and dyes;

As a main component various means for descaling.

Adipic acid is used as a mild acidifier with low hygroscopicity and a sour taste that persists long time, for example: in chewing gum up to 3%; in desserts up to 0.6%; in mixtures for baking up to 0.4%; in dry mixes for drinks up to 1% (in terms of a ready-to-use product).

Permissible daily intake– 5 mg/kg of body weight per day in terms of adipate ion. MPC in water 2.0 mg/l, hazard class 3.

E355 is allowed in flavored dry desserts in amounts up to 1 g/kg of the product; in powder mixtures for the manufacture of beverages at home in an amount up to 10 g/kg; in fillings, finishing semi-finished products for rich bakery products and flour confectionery products, etc. in an amount of up to 2 g/kg alone or in combination with other adipates in terms of acid.

Health risks of adipic acid.

Inhalation: cough, shortness of breath, sore throat.

Skin: redness.

Eyes: redness, pain.

Adipic acid - low toxicity when ingested.

An explosion is possible if it is mixed with air in powder form. When dry, the substance can be electrostatically charged by swirling, pneumatic conveying, pouring, etc.

Receipt.

E355 is obtained by the oxidation of cyclohexane, which takes place in two stages. Also, the drug is obtained by the interaction of cyclohexane with nitric acid or ozone. Hydrocaronylation of butadiene is considered one of the promising ways of obtaining. The world produces 2.5 million tons of adipic acid per year.

Adipic acid is a nutritional supplement that belongs to the group of antioxidants. If we talk about it from a physical point of view, then the substance is a crystal that does not have color. From a chemical point of view, the additive has all the properties that are characteristic of carboxylic acids. It is capable of forming salts that have a high degree of solubility in water. This antioxidant may be of synthetic or natural origin. Adipic acid has the ability to protect food from spoilage, rancidity, and oxidation processes. What is the hazard class of adipic acid? The hazard class of adipic acid is the second.

Scope of application

Adipic acid is approved by the European Union as a food additive, which is approved for use in production. food products. However given substance has not yet been fully studied, and therefore the exact status is unknown. That is why its use in some countries is simply prohibited due to its possible harm to human health.

AT natural environment acid is found in sugar cane and sugar beet juice. For industrial purposes, it is obtained by chemical synthesis from cyclohexane. This method is one of the most popular.

Applications:

as a food additive under the number E355 in order to impart a sour taste to food products, including during the production of soft drinks;
as a raw material in the production of polyhexamethylene adipamide, its esters and polyurethanes;
in order to remove material residues that remain after filling the joints formed between ceramic tiles;
as the main ingredient in products that are designed to remove scale;
in order to obtain intermediate synthesis products;
in tint rinses and other hair coloring products;
as lubricating oils and plasticizers, since it has a high degree of esterification into di- and monoesters, it forms polyesters with glycols.

On the territory of states where this food additive is recognized as suitable for use, it is used as an acidity regulator during the manufacture of drinks, caramel sweets, and other food products in order to maintain the required level of pH. It is added to some types of flavored dry desserts, but only in a strictly prescribed amount, which should not exceed 1 g per kilogram of the finished product. In powder mixtures for the purpose of preparing drinks, up to four grams of acid per kilogram of product is allowed, in jelly-like desserts - no more than six grams per kilogram of product. It is often used as an additive in the filling for confectionery and bakery products.

Harm or benefit?

many among food additives, like any substance, if the allowable dose is exceeded, they can cause damage human health. And this fact does not require proof. The impact of various additives on a person is due to individual characteristics, the amount of the substance used. Studies that are being conducted in the field of the effect of an antioxidant on human body, not completed yet.