Heat of reaction measurements of sodium borohydride alcoholysis

On-board hydrogen storage has been identified as one of the most challenging technical barriers to the transition from gasoline to hydrogen powered vehicles. The Hydrogen-On-Demand (TM) system patented by Millenium Cell Inc. uses sodium borohydride and water to generate hydrogen when needed. The system has many advantages over other types of storage methods such as compressed hydrogen, liquid hydrogen and metal hydrides. Nevertheless, the cost of making and regenerating sodium borohydride is too high. A recently filed patent indicates that sodium borohydride alcoholysis (e.g. using ethylene glycol) may offer some advantages over the aqueous system in terms of regeneration, which may significantly reduce the cost to regenerate sodium borohydride. To begin evaluating the energy efficiency of this new approach, this work experimentally characterizes the heat of reaction of sodium borohydride with ethylene glycol. The heat of reaction was measured to be approximately 220 kJ/mol (exothermic). For the sodium borohydride and water reaction, two different heat of reaction values have been reported in prior literature. The present work shows that the heats of reaction for both sodium borohydride hydrolysis and alcoholysis are both near 220 kJ/mol exothermically.