Regeneration of Spent-NaBH4 Using a Combined Process of Azeotropic Distillation and Schlesinger Method

Among various hydrogen storage materials, chemical hydrides such as sodium borohydride are of the most potential candidates. Unfortunately, the cost of using sodium borohydrides based on per unit of energy is still quite expensive than fossil fuels. That is, cost-down of such materials is critical to its successful applications. We aim to regenerate sodium borohydride (NaBH₄) from its spent product, i.e. sodium metaborate (NaBO₂), to reduce its cost and to ease any environmental concern on disposal of waste. In this study, we successfully convert NaBO₂ into an intermediate as trimethyl borate (B(OCH₃)₃) with an acid catalyzed esterification reaction and using an azeotropic distillation process, which was confirmed with GC-MS and FT-IR analyses. Subsequently, the Schlesinger method was employed successfully to convert trimethyl borate further to sodium borohydride verified with the evidence of NMR analysis. As high as a yield of 60% revealed from the iodimetry analysis data was obtained.

Keywords: hydrogen storage; regeneration; chemical hydride; sodium borohydride; sodium metaborate; trimethyl borate; Schlesinger method; azeotropic distillation.