SCALING OF THE SYNTHESIS PROCESS OF BENZO-15-CROWN-5 IN THE CONDITIONS OF PILOT PRODUCTION

Abstract

This article describes the development of a method for the synthesis of benzo-15-crown-5, a promising extractant of lithium isotopes that are widely used in various fields of nuclear technology. The synthesis of benzo-15-crown-5 was carried out by the method of two-component condensation of pyrocatechol and tetraethylene glycol dichloride in the presence of a template agent sodium hydroxide, followed by extraction of crown ether by hexane or isolation by vacuum distillation. Optimal synthesis conditions were determined, impurities were chromatographically identified, the technological reaction time was determined and methods of introducing raw materials into the reaction mass were investigated. The study showed that the drip addition of tetraethylene glycol dichloride leads to the fact that the content of benzo-15-crown-5 reaches 82.1% in the reaction mass. The optimal holding time of the reaction mass is 7 h at boiling point. The processes of isolation of the target product (hexane extraction, vacuum distillation) were selected and studied. The proven technique has been fully adapted to a pilot industrial plant for the synthesis of crown ethers, consisting of three mixing reactors, nutch filters, measuring tanks and a vacuum distillation unit. The developed installation allows to receive up to 25 kg of high-quality product per month. The product was identified using NMR and IR spectroscopy and elemental analysis. At the pilot plant, it was possible to obtain a product whose yield was 41%, compared with 48% at the laboratory plant, which is a very good indicator for scaling, without loss of quality of the synthesis product. The purity of benzo-15-crown-5 was more than 98% according to gas-liquid chromatography.