RU2176998C2 - Method of preparing levulinic acid - Google Patents

Abstract

FIELD: perfume, pharmaceutical, metal-working industries, and organic synthesis. SUBSTANCE: levulinic acid is prepared by hydrolysis of hexose-containing stock with diluted hydrochloric acid in the presence of manganese dioxide in amount of 0.19-0.3 % of weight of hexose- containing stock for 30-35 h at atmospheric pressure and at temperature of 105-107 C. EFFECT: greater yield of the desired product and simplified process. 2 cl, 3 ex, 2 tbl

Description

 The invention relates to the chemistry of organic compounds, and in particular to a method for producing levulinic (4-oxo-pentanoic) acid, which is used to produce pesticides, adhesive compositions for polypropylene, in the perfumery, pharmaceutical, metalworking industries, and also as an intermediate for organic synthesis.

A known method of producing levulinic acid (LC) by hydrolysis of diluted hydrochloric acid sucrose at atmospheric pressure and a temperature of 105-107 ^o C for 24 hours. [Preparative Organic Chemistry, under. ed. N. S. Wulfson, L.-M.: Chemistry, 1964, p. 784]. The disadvantage of this method is the use of scarce raw materials and a low yield (43%, calculated on the assumption that LA is obtained only from the fructose sucrose fragment) of the target product.

The closest to the feedstock and the results achieved is a method for producing LA by hydrolysis of diluted hydrochloric acid of spruce sawdust at a temperature of 190 ^o C. [US Pat. 3258481 USA, 06/28/66]. The disadvantage of the latter method is the low yield (36%) of the target product and the use of equipment designed for pressure 15195 - 19247 hPa, which creates technical difficulties for the organization of industrial production of drugs and requires special safety measures.

 The purpose of the invention is to increase the yield of the target product and simplify the process.

 This goal is achieved by obtaining LC by hydrolysis at atmospheric pressure of a hexose-containing feed heated to boiling with dilute hydrochloric acid in the presence of manganese dioxide. Carrying out the reaction at atmospheric pressure allows to simplify the process, and the use of manganese dioxide allows to increase the yield of the target product to 56%.

A distinctive feature of the invention is the use of manganese dioxide in an amount of 0.19 - 0.30% by weight of the raw material and the process for 30 - 35 hours at a temperature of 105-107 ^o C and atmospheric pressure.

 The invention is illustrated by the following examples.

 Example 1

43.2 g of dry wood sawdust, 215 ml of water, 140 ml of hydrochloric acid ρ = 1.17) and 0.08 g of manganese dioxide are charged into the flask. The reaction mixture is heated to 105-107 ^o C and maintained at this temperature and atmospheric pressure (960 - 1013 hPa) for 35 hours. The cooled reaction mass is filtered under vacuum. The filter residue is washed with 50 ml of hot water, the washings are combined with the filtrate and evaporated in vacuo (26.6 - 39.9 hPa). The residue after evaporation is distilled under vacuum (5.32 - 8 hPa), collecting the fraction with T. bale. 123 - 127 ^o C. After re-distillation obtained 7.7 g of LA with T. pl. 30 - 31 ^o C. The yield is 50% of theoretical, considering the 50% content of cellulose in sawdust. The indicated yield of the LC was obtained from sawdust of coniferous wood.

 According to the results of independent experiments, the optimal reaction time (Table 1) was established, which is 35 hours and the optimal amount of manganese dioxide (Table 2), which is 0.28 - 0.30% by weight of sawdust.

 Example 2

67.5 g of cellulose, 270 ml of hydrochloric acid (ρ = 1.17), 60 ml of water are charged into the flask and incubated for two days at room temperature. Then, 0.16 g of manganese dioxide and 400 ml of water are added to the flask. The flask is heated to 105 - 107 ^o C and maintained at this temperature and atmospheric pressure (960 - 1013 hPa) for 30 hours. The cooled reaction mass is filtered under vacuum, the residue is washed with 100 ml of hot water. Wash water is combined with the filtrate. Further processing, as in example 1. Received 24.8 g of LC with T. pl. 30 - 31 ^o C. Yield 50% of theoretical. The specified yield was obtained using cellulose brand HB-7 (sulfate, bleached from coniferous species, GOST 9571-84).

 According to the results of 76 independent experiments, the optimal reaction time was found to be 30 hours and the optimal ratio of the main components of cellulose: hydrochloric acid: water, which is (by weight) 1: 6.2: 6.8, respectively. The optimal amount of manganese dioxide is 0.23% by weight of cellulose.

 Example 3

68 g of sucrose, 32 ml of hydrochloric acid (ρ = 1.17), 136 ml of water and 0.16 g of manganese dioxide are charged into the flask. The reaction is carried out as in example 2. The product is isolated, as in example 1. Received 15.3 g of LK with T. pl. 30 - 31 ^o C. The yield of 31.1% of theoretical, based on sucrose.

 The proposed method allows to increase the yield of the target product through the use of manganese dioxide and to simplify the process by conducting the reaction at atmospheric pressure.

Claims (1)

A method of producing levulinic acid by hydrolysis of hexose-containing raw materials with dilute hydrochloric acid at elevated temperature, characterized in that the process is carried out in the presence of manganese dioxide taken in an amount of 0.19-0.30% by weight of hexose-containing raw materials for 30-35 hours at atmospheric pressure and a temperature of 105-107 ^o C.

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