Single stage production and hydrolysis of sodium borohydride

Abstract

In the present study, a single stage sodium borohydride (SBH) synthesis process from anhydrous borax without the use of sodium metal was developed. The effects of process parameters namely temperature, reaction time and hydrogen pressure on the efficiency of SBH production were investigated in an autoclave type fixed bed reactor (V = 1000 cm(3)). The optimum range of operating conditions was T = 550-560 degrees C, P-H2 = 40-50 bar and t = 4-6 h. Under these conditions, the production efficiency of SBH was 85-90% by mole and purity was determined as 97-99%. It was observed that SBH efficiency was highly influenced by synthesis conditions while its purity was not. For the hydrolysis of SBH, different effective heterogeneous catalysts were prepared. Hydrolysis tests have been performed at ambient temperature over a range of sodium hydroxide concentration (2.5-15 wt%) and sodium borohydride concentration (5-40 wt%) in the presence of a selected Ni(20%)-Fe(20%)/gamma-Al2O3 catalyst. The basic principles for SBH hydrolysis were also outlined for PEM fuel cell applications. Copyright (C) 2011, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.