SU156938A1 - - Google Patents

Description

A known method for producing dicarboxylic acids, for example sebacic acid, by electrolysis of sodium salts of adipic acid monomethyl ester.

The proposed method is based on the fact that electrolysis is carried out in the anode space. This increases the conversion of the monoester and the process is intensified.

According to the proposed method, the electrolysis process is carried out in two stages with a high content of monoester salt in the initial electrolyte. At the same time, its concentration in the solution after electrolysis is adjusted to values that allow directing the solution after distilling off the alcohol directly to saponification.

In the first stage, the electrolysis process takes place in the electrolyzer without a diaphragm, under conditions for the electrosynthesis of sebacic acid. After practically only the salt of the monoether remains in the electrolyte, it translates the anode space of the electrolytic cell with a hemispherical diaphragm.

When electrolysis is carried out in this electrolysis cell, the transfer of alkali metal ions, such as sodium, into the cathode, the space and alkali accumulation occurs. The acid environment is maintained in the anode space and further electrosynthesis of the target product continues at the anode.

The salt concentration, therefore, is reduced to values that allow the direction of the solution after electrolysis and distillation of the alcohol and saponification.

Ho 156938-2 -

Consequently, the multistep process of returning the monoester salt is replaced by a single electrolysis step in a diaphragm electrolyzer. The alkali accumulated in the cathode space of the electrolyzer is returned to the stage of preparation of the initial electrolyte.

Example. 430 ml of a methanol solution containing 280 g of monomethyl dipipate, 82 g of sodium monomethyl dipinate, and 46 g of water are poured into a glass electrolyzer. The electrolysis is carried out with the continuous circulation of the electrolyte and the current density on platinum, titanium platinum or graphite anodes 5000-6000 a / m-. After the discharge of the theoretical amount of electricity, the electrolyte containing dimethyl sebacate, 82 g / l sodium monomethyl dipipate and 2-3 g / l monomethyl adipate, IB receives the anode space of a ceramic diaphragm electrolyzer, the cathode space of which is filled with 1% NaOH solution. After passing 7.5 hours of sodium monomethyl adipate in the anolyte as a result of the conversion of the platinum, titanium platinum or graphite anode into dimethyl sebacate and the transition of sodium ions into the cathode space, its content is reduced to 21.5 g / l, which is (in terms of monomethyl adipate) about 5% of the loaded. With further current transmission, even greater conversion of monomethyl adipate can be achieved. However, due to a strong fall in electrical conductivity, the cell on the electrolyzer rises and the current decreases. Depending on the nature of the anode used and the electrolysis conditions, the output of sebacic acid is 80-85 by substance, 65-70% by current.

Subject matter

The method of electrosynthesis of sebacic acid from adipic acid monoesters, characterized in that, in order to capture the conversion of the monoether and to intensify the process, electrolysis after passing the theoretical amount is carried out in the anode space.