Thermal properties of 2,2′-bipyridine-6,6′-dicarboxylic acid bis(N-ethyl-4-hexylanilide), an extractant for radioactive waste components

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Thermal properties of 2,2′-bipyridine-6,6′-dicarboxylic acid bis(N-ethyl-4-hexylanilide) (DYP-7) were studied by DSC-TG with the aim of evaluating its fire and explosion hazard. Heating at a rate of 1 K min^–1 is accompanied by exothermic effects with the onset temperatures of 202, 312, and 432°С for the initial extractant and 62, 297, and 412°С for the extractant saturated with nitric acid. The presence of extracted nitric acid decreases the self-ignition point of DYP-7 by at least 20°С. The onset temperatures of the exothermic effects tend to increase with increasing heating rate. The extractant thermolysis products characteristic of the exothermic effect with the onset temperature of 202°C were identified by GC-MS. These are the deethylation product, 2,2′-bipyridine-6,6′-dicarboxylic acid N,N′-bis(4-hexylphenyl)amide, and product of further dearylation/reduction, 6′-formyl-N-(4-hexylphenyl)-2,2′-bipyridine-6-carboxamide.