Adipic acid_Kain Industrial Additive

Adipic acid is also called “fat acid”. Chemical formula HOOC(CH2)4COOH. Molecular weight 146.14. Found in beet juice. White crystal or crystalline powder, odorless, sour taste, soft sour taste. The melting point is 152°C, the boiling point is 330.5°C, and the auto-ignition temperature is 420°C. It can sublime, does not absorb moisture, and is quite stable. Very soluble in boiling water, soluble in methanol, ethanol, soluble in acetone, slightly soluble in water, cyclohexane, slightly soluble in ether, insoluble in benzene and petroleum ether. The aqueous solution is acidic, pH=2.7 (saturated solution); pH=3.2 (0.1% aqueous solution). The dissociation constants K1=3.90×10-5 and K2=5.29×10-6. It has the chemical properties of carboxylic acid, such as esterification, and its characteristic reaction is heating decarboxylation to generate cyclopentanone. Industrially, it is produced from phenol, cyclohexane or tetrahydrofuran. Adipic acid is an important raw material for the synthetic fiber nylon 66 (polyhexamethylene adipamide). It can also be used to make plasticizers, synthetic lubricants and food additives.

chemical reaction

Adipic acid has the general properties of dibasic acids and can be esterified to form monoester or diester; under pressure and in the presence of a catalyst, it can be reduced to hexanediol; it can react with ammonia or amine to undergo ammonolysis to form hexanediol. Diamide; in the presence of a dehydrating agent, the amide is dehydrated to form adiponitrile; when heated to 210°C, it can be dehydrated to form unstable adipic anhydride, but it returns to linear polyanhydride when cooled to 100°C; heated When the temperature reaches above 300°C, adipic acid decarboxylates to form cyclopentanone.
Reacting with thionyl chloride can generate adipic acid chloride; reacting with hexamethylenediamine can generate nylon 66 salt (adipyl adipate); reacting with glycol can generate polyester, and further reacting with diol can generate polyester. Diisocyanate reaction can produce rubber; the diethyl ester of this product reacts with diethyl oxalate in the presence of sodium alkoxide to produce 2,3-dioxane-1,4-dicarboxydiethyl ester.

use

Acidity regulator, acidulant, compound leavening agent, neutralizer, spices. Adipic acid is mainly used in the manufacture of nylon 66. Also used in the manufacture of plasticizers, greases, and polyurethane foams. A small amount of it is used as an acidifier in food and in baking powder instead of tartaric acid. It can also be used to make pesticides and adhesives.
Adipic acid is an important raw material for fine chemicals, organic synthesis and polymer materials; it is related to multi-branched chains The esters produced by the reaction of alcohols are excellent lubricating oils, such as dioctyl adipic acid, didecyl ester, 2-ethylhexyl ester, 2-ethylbutyl ester and 2-butyloctyl ester; in addition, this It is also a raw material for manufacturing nylon (polyamide can be obtained by condensation with diamines), polyurethane foams, plasticizers, insecticides, adhesives, etc.; it is used as a precursor for dibasic nitriles and diamines in organic synthesis. Materials; raw materials for synthetic medicines and synthetic fragrances. Because the aqueous solution of this product has the lowest acidity among commonly used sour agents, the pH value changes very little within a wide concentration range, so it is widely used as a buffer, neutralizer, sour agent, pH regulator, and flavor enhancer for food. , when used as a buffer, it can effectively maintain the acidity within the range of 2.5 to 3.0. It is an edible acidity regulator allowed to be used according to China’s GB2760-1996; in addition, it can also effectively inhibit the browning of most fruits; used for Gelatin-containing powdered foods, egg whites and dairy products can change the foaming performance; improve the melting characteristics of cheese and cheese spreads; promote the gelling of artificial jams and imitation jelly; emulsify food flavors and fruit-flavored hard candies; Used as a sour agent in acidified hot-packed canned foods to soften the sourness and make the flavor lasting; combined with phytic acid, it can prevent oil deterioration and act as a polyvalent chelator to improve oil quality; used in beverages, wine pairings, and cheese Processing, cold drinks, pickles; when used in baked goods, it can replace tartaric acid; due to its low hygroscopicity, it can be used in solid powder juice.

Preparation

Cyclohexanol is oxidized with concentrated nitric acid, and cyclohexanone is prepared by air catalytic oxidation. Place 0.032 mole of 50% nitric acid and 0.1 g of ammonium vanadate in a beaker and heat to about 90°C. Under stirring, first add a few drops of cyclohexanol, and then add the remaining cyclohexanol (0.01 mol in total) at 60°C after the reaction starts. After about half an hour, cool to 0°C, filter, and wash the residue with ice water and dry. The yield of crude product is 58-60%. During purification, it is recrystallized with concentrated nitric acid and water in sequence. The melting point is 151-152°C.
Two-step method: oxidize cyclohexane with air in the presence of cobalt catalyst (or boric acid and boric anhydride) to obtain a mixture of cyclohexanone and cyclohexanol, without separation, in the presence of copper vanadium catalyst, It is oxidized under the action of nitrous acid to generate o-nitrosocyclohexanone, which is then oxidized by nitric acid (60%) to generate 2-nitro-2-nitrosocyclohexanone, which is hydrolyzed and ring-opened to generate 6- After decomposition, oxime-6-nitrocaproic acid can be obtained crudely. After separation, it can be decolorized and recrystallized for purification. This method is a series of two-stage reactors. Each ton of product consumes 1,200kg of cyclohexane and 1,600kg of nitric acid, with a yield of about 95%. The one-step method has been successfully developed.
One-step method: use cyclohexane as raw material, acetic acid as solvent, cyclohexanone as initiator, cobalt acetate as catalyst, and use air oxidation at a pressure of 2.0~2.5MPa and a temperature of 90~95°C. Cyclohexane, unreacted cyclohexane and catalyst are separated and recovered. The product is cooled and crystallized. After separation, crude adipic acid is obtained. The crude adipic acid can be decolorized by activated carbon and recrystallized to obtain a refined product. This method consumes 1233kg of cyclohexane, 453kg of acetic acid, 120kg of cyclohexanone, 5.73kg of cobalt acetate and 26kg of activated carbon per ton of product.

Toxicity and hygiene

This product has low toxicity, the oral LD50 of rats is 273 mg/kg; the oral LD50 of mice is 1900 mg/kg. GB 9685-2008 stipulates that plastics (PE, PP, PS, AS, ABS, PA, PET, PC, PVC, PVDC, UP), coatings and paper should be used in appropriate amounts according to production needs.

Scope and dosage of use

For jelly powder, it is 0.15g/kg. Practical reference: Used in gelatin-containing powdered foods, cake egg whites and dairy products to improve whipping and foaming performance. Used in artificial jams and jelly to promote their gelling effect.

Precautions for use

This product has small pH changes within a relatively large concentration range, has good pH adjustment buffering performance, and can effectively maintain the acidity within the pH range of 2.5 to 3.0. This product has a soft and long-lasting sour taste, especially suitable for products that are not suitable for immediate release of sour taste.