The Processing of NaBH₄ from Na₂B₄O₇ by Mechano-chemical Synthesis and Its Catalytic Dehydrogenation

Abstract

Sodium borohydride (NaBH₄) is a specialty reducing agent used in fuel cell systems. Feasible NaBH₄ production techniques are required to reduce the costs of NaBH₄, making its usage attractive. At present, anhydrous borax (Na₂B₄O₇) is a promising reactant in NaBH₄ synthesis. However, further improvements to optimize the yield of the NaBH₄ production process operating with MgH₂ and Na₂B₄O₇ in ball milling are necessary. In order to obtain optimum reaction conditions, experiments were performed under inert atmosphere. First, we attempted to compensate Na insufficiency with the addition of Na, NaH, and Na₂CO₃. Next, the reaction period and stoichiometric ratio of our experiments were studied with Na₂B₄O₇ and MgH₂. Reaction times were varied from 200 to 600 min, and regulated the excess MgH₂ addition at 0, 10, 30, 50, and 70%. The synthesized products were characterized by FT-IR and XRD analysis and checked our results using iodimetry and dehydrogenation tests. We were able to achieve yield levels of approximately 84% of NaBH₄ in certain purification processes with ethylene diamin after 400 min of reaction time and at excess MgH₂ levels of 10% or more.

Keywords:

• Borax
• dehydrogenation
• hydrogen energy
• mechanochemical synthesis
• sodium borohydride