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 degrees 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.