Effect of magnesium on sodium borohydride synthesis from anhydrous borax

This paper describes the effect of magnesium (Mg) addition on sodium borohydride (NaBH4) synthesis from anhydrous borax (Na2B4O7) in the presence of the hydrogen atmosphere. NaBH4 synthesis has been investigated at a temperature of 550 °C and 25 bar hydrogen pressure experimentally. The reactions were carried out in a stainless steel batch reactor placed in a vertical furnace. The extent of reaction was monitored by observing pressure decrease in the system. Aqueous ammonia was used to extract NaBH4 from the reaction mixture. Highly pure sodium borohydride was obtained after evaporation of the solvent. Characterization of the product was made by the X-ray powder pattern studies. It was found that the amount of Mg plays an important role in NaBH4 formation. Increasing the amount of Mg resulted in appreciable increase in NaBH4 formation. The NaBH4 yield reached in the experiments was found to be 93% in a single batch process.

► Anhydrous borax is an important compound; it can be used to produce NaBH4.
► NaBH4 production has been investigated at a temperature of 550 °C and 25 bar hydrogen pressure experimentally.
► It was found that the amount of Mg plays an important role in NaBH4 formation.
► Characterization of the product was made by the X-ray powder pattern studies.
► Use of aqueous ammonia to extract NaBH4 from the reaction mixture is practical and efficient.