Synthesis of magnesium hydride and sodium borohydride at low temperatures

Abstract

In this study, experimental conditions for production of magnesium hydride and sodium borohydride by low temperature grinding are investigated. In the first set of experiments, it was attempted to confirm the information presented in the literature that magnesium hydride could be produced by heating at 350oC for 24 hours under 10 atmospheres of pressure. The results obtained in this study indicated that even a higher temperature heating at 400oC under 10 bar hydrogen pressure was insufficient for magnesium hydride formation. Heating and grinding time were selected as the most effective parameters by which a full-factorial experimental design methodology was implemented. Statistical analysis results indicated that a combination of grinding and a 50oC heating was most effective. Hence, grinding was identified as the most significant factor effect on the production of magnesium hydride. Two different mills were used, in this study, and it was found that disc mill was more effective than ball mill. Different combinations of dehydrated borax, sodium carbonate, magnesium, hydrogen gas, sodium hydride and sodium metaborate were tested without success to produce sodium borohydride. In the final set of experiments, sodium borohydride could be successfully produced by using trimethyl borate and sodium hydride in a disc mill at 50oC under 10 bars hydrogen pressure.