Sodium Borohydride Synthesis by Reaction of Na_2O Contained Sodium Borate with Al and Hydrogen

摘要

In this paper, sequential experiments were designed to explore the possibility of sodium borohydride synthesis by reaction of sodium borates with Al and hydrogen. It was found that NaBH_4 cannot be formed by reaction of NaBO_2 with Al and hydrogen but can be formed by reaction of Na_4B_2O_5 with Al and hydrogen. NaBH_4 formation was confirmed by X-ray diffraction analyses and morphology observations. It was found that Na2O in Na_4B_2O_5 played an important role in NaBH_4 formation due to the depression of Al_2O_3 formation. The highest sodium borohydride yield (65.8%) was obtained by reaction of a mixture of Na_4B_2O_5, NaBO_2, and Na_2O with Al and hydrogen. However, NaBH_4 formation was dependent upon the physical state of sodium borates. When sodium borates melted, NaBH_4 formation was retarded due to the difficulty of hydrogen diffusion to Al surfaces.