Kinetic studies of reaction between sodium borohydride and methanol, water, and their mixtures

This paper reports the kinetics of hydrogen generation from the reaction between sodium borohydride and methanol, water, and their mixtures over a temperature range between -20 and + 50 degrees C. Hydrogen generation was found to obey a first- order rate law with respect to sodium borohydride concentration for each of the four reacting mixtures of methanol, "nearly dry" methanol (2:1 water to sodium borohydride mole ratio), "wet" methanol (10:1 water to sodium borohydride ratio), and water, with activation energies of 53.0 +/- 3.4, 52.3 +/- 9.5, 36.1 +/- 2.8, and 86.6 +/- 8.0 kJ/ mol, respectively. Methanolysis of sodium borohydride was shown to be a feasible method for low- temperature hydrogen generation. However, this noncatalytic reaction system exhibited large lag time and slow reaction kinetics at low temperatures. Our study indicates that the reaction system based on sodium borohydride and the nearly dry methanol can be a potential high gravimetric density hydrogen storage system.