Thermoanalytical and NMR investigation of NaBH₄·2H₂O thermolysis process

The article describes the thermolysis process of sodium borohydride dihydrate in thermoanalytical experiments. The reaction was carried out without solid catalyst and with catalyst as cobalt boride Co₂B. It has been found out that in both cases the process starts after the peritectic reaction of the starting compound and forms a liquid phase. The enthalpy of peritectic reaction is ΔH_react = 19 ± 2 kJ mol⁻¹. When thermolysis proceeds in acetonitrile solution without a catalyst intermediate hydroxyborohydride NaBH₃OH and/or Na(BH₃)₂OH is formed according to the NMR experiment data. The formation of similar complexes in the solid phase is confirmed by experiments on the oxidation of the thermolysis products. Thermolysis process with solid catalyst proceeds with an intense exothermic effect at lower temperatures. The kinetics of the non-catalytic process is described by the model of two consecutive reactions, and reaction with the solid catalyst model is approximated by two parallel reactions.