Kinetics of Sodium Borohydride Hydrolysis in Comparison with Ammonia Borane Using Cobalt Catalysts

The kinetics of sodium borohydride catalytic hydrolysis with cobalt catalysts Co₃O₄/ZnO, Co/ZnO, Co₃O₄/zeolite, Co/zeolite, Co(OH)₂, Co₃O₄, and Co–B was studied, and the kinetic characteristics of the process were compared with the same characteristics of the catalytic hydrolysis of ammonia borane. The concentrations of sodium borohydride and NaOH in aqueous solution in all cases were 0.064 and 0.06 M, respectively. The apparent activation energy and the rate of hydrogen evolution during the sodium borohydride hydrolysis in the temperature range of 35–80°C were determined in each case. The kinetic data were processed using zero-order, first-order, and Langmuir–Hinshelwood reaction models. The apparent activation energies for the sodium borohydride hydrolysis ranged from 37.0 for Co₃O₄ to 72.6 kJ/mol for Co₃O₄/ZnO. These values exceeded similar values for the ammonia borane hydrolysis, which were in the range of 26.0–47.4 kJ/mol. A higher rate of hydrogen evolution was observed during the sodium borohydride hydrolysis compared to ammonia borane when using these catalysts, except for Co–B and Co/ZnO catalysts. The maximum rates of hydrogen evolution 3510 and 3140 mL of H₂ (g cat)^–1 min^–1 were observed when using Co(OH)₂ and Co–B catalysts, respectively.