SU1728226A1 - Method of nitromethane synthesis - Google Patents

Abstract

The invention relates to nitroaliphatic hydrocarbons, in particular, a method for producing nitromethane. which is used as a solvent. The goal is to increase output and simplify the process. Synthesis is carried out by the reaction of chloroacetic acid with sodium nitrite and soda, with decomposition of the sodium nitroacetic acid intermediate salt in an aqueous medium, with heating, with azeotropic release of the desired product. separation of the bulk of nitromethane. salting out the aqueous layer, adding to the bottom residue, repeated azeotropic distillation and separation of additional mass of nitromethane. The yield of 40- 43%. The method allows to increase the yield by 10%. reduce time and simplify the process.

Description

This invention relates to the chemistry of aliphatic nitro compounds. in particular, to a method for producing nitromethane. which is widely used in industry as a highly efficient solvent, reactive fuel. in biotechnology, and also as a component of non-aqueous electrolytes.

Existing methods for the preparation of nitromethane (by methylation of nitrous acid salts, nitration of paraffins) require sophisticated equipment and, sometimes, expensive starting materials.

Paraffin wiping requires sophisticated equipment associated with high pressure and elevated temperature. The chemical process is based on the use of aggressive nitrogen oxides and concentrated nitric acid. In addition, a mixture of different nitroparaffins is always formed as a result of the nitration of paraffins. which require additional rectification.

Closest to the proposed method is the Kolbe reaction.

The aqueous solution of chloroacetic acid is neutralized with soda (or alkali), an aqueous solution of sodium nitrite is added and, when heated, decompose the sodium salt of nitroacetic acid formed. Azeotrope is distilled. nitromethane is separated. and the aqueous layer is salted out with sodium chloride (per 100 parts by volume of water, 35 parts of sodium chloride are taken). The azeotrope is again distilled. fractions are combined. Yield 33%. The salting out of nitromethane from 100 ml of the aqueous layer takes 5-30 minutes.

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

The goal is achieved by those. that with the method of producing nitromethane. which includes treatment with soda, sodium nitrite in aqueous solution of chloroacetic acid, followed by decomposition of the nitroacetic acid sodium salt when the intermediate sodium salt is heated and the azeotrope is isolated from the aqueous layer, separating the nitromethane from the aqueous layer, salting out the nitromethane from the aqueous layer and re-stripping the azeotropy from the aqueous layer, removing the nitromethane from the aqueous layer, salting the nitromethane from the aqueous layer and re-stripping the azeotropy. The salting out of nitromethane is carried out by transferring the aqueous layer to the bottom residue after the first azeotropic distillation.

The yield of nitromethane rises from 33 to 40-43%. and the time of separation of nitromethane from the aqueous layer is reduced by 5-6 times. moreover, sodium salt is less than with the known method, and salting out goes most fully, which affects the increase in the yield of nitromethane.

Example. 14.1 kg (14.4 mol) of chloroacetic acid are dissolved in 30 l of water, neutralized with anhydrous soda (8 kg) to pH 8 (per litmus). Separately, dissolve 11.2 kg (14.4 mol) of sodium nitrite in 18 liters of water and pour 15 liters of it into the distillation still to 14.1 kg of an aqueous solution of sodium chloroacetate. The receiver is cooled in a bath with ice water. The cube is heated to 85 ° C. The remaining sodium nitrite solution is placed in a dropping funnel mounted on a still tank and poured in when the process begins.

Distillation cube per 100 l is filled with 75% of its volume. When the reaction mixture reaches 80 ° C, gas bubbles (C02) are released. heating stop. The decomposition of the nitroacetic acid sodium salt is self-heating. The temperature rises to 110 ° C (1.5 hours). At 45 ° C, the azeotrope is distilled off and collected in a receiver. When

the temperature drops to 95 ° C. the distillation cube is again heated to 110 ° C and the process is carried out until the release of nitromethane as an oily liquid (1.5 hours) is stopped. A total of 6 liters of azeotropic mixture of water and nitromethane was distilled off. Crude nitromethane (bottom layer) is separated from the aqueous layer in a separatory funnel (3.68 kg), dried over anhydrous CaCl2 (5% of the volume of nitromethane).

The aqueous layer (2.6 L) is transferred through the dropping funnel to the stills to the still bottoms and again distilled off (30-35 minutes), nitromethane (121 g) is separated and the fractions are combined. Yield 3.8 kg (43.4%), Bpd 101.1 ° C, 1.1381.

d4

The proposed method for the production of nitromethane from chloroacetic acid with the use of a vat residue in the separation of nitromethane from the aqueous layer increases the yield, greatly shortens the process time, and the ease of installation makes the method cost-effective on an industrial scale.

Claims (1)

Claims of Invention A method of producing nitromethane by treating chloroacetic acid with sodium nitrite and soda and by decomposing the sodium salt of nitroacetic acid in an aqueous medium, with heating, with azeotropic distillation and separation of the bulk of nitromethane. salting out of the water layer. azeotropic distillation and separation of additional mass of nitromethane. different in that. what. in order to simplify the process and increase the yield of the target product, salting out the aqueous layer is dried by adding to the bottom residue after distilling off the bulk of nitromethane.