RU2119486C1 - Method of medicinal ascorbic acid producing - Google Patents

Abstract

FIELD: chemical technology, vitamins. SUBSTANCE: invention relates to a method of producing medicinal ascorbic acid from solution of technical ascorbic acid by multistep crystallization. Mother liquors formed at medicinal ascorbic acid crystallization are treated preliminary with sodium-containing alkaline compound, for example, NaOH, Na₂CO₃, NaHCO₃, or hydrochloric acid to pH 2.2-2.4. Method ensures to decrease process time by 4-5-fold and diminish product loss by 2-3%. EFFECT: improved method of producing. 2 cl, 6 ex, 1 tbl

Description

 The invention relates to the production of ascorbic acid, in particular to a method for producing ascorbic acid of pharmacopoeial quality.

 A wide industrial application has found a way to obtain medical ascorbic acid by multistage crystallization (Schneidman L.O. "Production of vitamins" M., Pishchev. Prom., 1973, S. 288 - 290). This method consists in dissolving technical ascorbic acid, purification with activated carbon, crystallization within 6-8 hours and the release of medical ascorbic acid. The amount of the selected target product after the first crystallization is 65 - 70% of the entered technical ascorbic acid.

 The remaining 30–35% of the acid is contained in the mother liquor 1, which is collected, evaporated in a vacuum apparatus and fed to the second crystallization within 12–16 hours. The isolated product is centrifuged, washed and sent to recrystallization in the first stage.

 The mother liquor 2 is collected, evaporated in vacuo and fed to a third crystallization within 24 to 28 hours.

 The isolated product is centrifuged, washed and sent to recrystallization sequentially in the 2nd, then the 1st stage.

 The mother liquor 3 is collected, evaporated in vacuo and fed to the fourth crystallization within 48 to 72 hours. The isolated product is centrifuged, washed and sent to recrystallization sequentially in the 3rd, 2nd, 1st stage. The mother liquor 4 is collected and removed from the manufacturing sector.

 Isolation of medical ascorbic acid from mother liquors according to the described technology is long (100 - 120 hours), which leads to inevitable losses of the target product due to prolonged exposure to aqueous solutions and requires high energy costs.

 The total yield of medical ascorbic acid, taking into account the allocation of it from the mother liquor, is 92 - 94%. 6 - 8% of the target product is irretrievably lost.

 The disadvantage of this method is the duration of the process and significant losses of the target product when it is isolated from the mother liquor.

 To eliminate these drawbacks in the proposed method, the mother liquors formed during crystallization of medical ascorbic acid, in contrast to the known one, are pretreated with a sodium-containing alkaline compound or hydrochloric acid to a pH of 2.2 - 2.4, followed by its concentration, crystallization, recrystallization of the resulting product, and the release of medical ascorbic acid.

 Bringing the pH of the mother liquors to values of 2.2 - 2.4, the neutralization of impurities inevitably present in solutions to readily soluble salts is achieved, which during the crystallization process not only easily separates with the mother liquor, ensuring the quality of precipitating ascorbic acid crystals, but also play the role of a salting out agent what is achieved by increasing the product yield and reducing crystallization time.

In the case of pH> 2.4, mother liquors are treated with hydrochloric acid. At pH <2.2, acidity is reduced by adding one of the alkaline agents NaOH, Na ₂ CO ₃ , NaHCO ₃ to the mother liquor.

 The proposed method is illustrated by the following examples.

 Example 1

300 g of technical ascorbic acid, in a 100% calculation of the basic substance, were dissolved in 320 ml of distilled water, heated to 70 ^o C, 12 g of activated carbon were added, kept for 3 minutes, carbon was filtered off, and after 6– from the clarified filter crystals of medical ascorbic acid (MAK), which were washed with 50 ml of distilled chilled water and 40 ml of chilled ethyl alcohol, were separated by hourly crystallization upon cooling to 0 ^° C. After drying, 206.4 g of MAK was obtained with a content of 99.8% and a yield of 68%.

The first mother liquor combined with washing water in an amount of 420 ml with an ascorbic acid (AK) content of 220.2 g / l (total 92.41 g), pH 3.0 was acidified with hydrochloric acid to pH 2.4, after which concentrated to a solids content in the solution of 81% and crystallization was carried out with stirring and cooling to 0 ^o C for 6 hours. Received 76.1 g of AK-2 with a content of 98.8% (100% - 75.18 g).

94 ml of mother liquor 2 after cooling AK-2 with an AK-2 content of 184 g / l (17.23 g total) was concentrated to a solids content of 80% and crystallized under stirring and cooling to 0 ^° C. for 10 hours. 14.58 g of yellow crystals were obtained in AK-3 with a content of 97.6% (14.23 g), which, together with AK-2, were purified and recrystallized similarly to TAC recrystallization. Received 61 g of MAA with a content of 99.5% (60.79 g).

 The 3rd mother liquor containing 1.9 g of AK, heavily contaminated with tarry impurities and unidentifiable salts, was sent to the dump.

 The mother liquor after recrystallization of AK-2 and 3 (mother liquor 1) in an amount of 150 ml, with a content of AK of 186.6 g / l was treated similarly to the treatment of mother liquor 1. An additional 26.36 g of MAA with a content of 99.4% was obtained. A total of 291.0 g of 100% ascorbic acid was obtained with a yield of 97%.

 The resulting ascorbic acid meets all the requirements of FS 42-2668-89.

 Examples 2 to 6 are presented in the table.

 Examples 2 to 4 - in the conditions of the claims, examples 5 to 6, in the conditions of the prototype.

 Thus, the examples of the proposed method confirm the possibility of reducing the total crystallization time to 28 hours, which is 4 to 5 times less than in the known one. The yield increases by 1 - 3% and is 95 - 97%. In addition, the operation of processing the third mother liquor due to the maximum extraction of ascorbic acid from the first and second mother liquors is excluded.

Claims (2)

 1. A method of obtaining medical ascorbic acid, including purification of a solution of technical ascorbic acid, crystallization, separation of crystals of medical ascorbic acid, concentration and crystallization of mother liquors, isolation of crystalline mother liquors, their purification and recrystallization to medical ascorbic acid, characterized in that the mother liquors, formed during crystallization of medical ascorbic acid, pre-treated with a sodium-containing alkaline compound or with hydrochloric acid to a pH of 2.2 - 2.4. 2. The method according to claim 1, characterized in that NaOH, or Na ₂ CO ₃ , or NaHCO _{3 is} used as the alkaline compound.

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