Studies on synthesis and dehydrogenation behavior of magnesium alanate and magnesium-sodium alanate mixture

Magnesium alanate (Mg(AlH4)(2)) has been synthesized by mechanochemically activated metathesis reaction involving MgCl2 and NaAlH4. Its dehydrogenation kinetics and storage capacity has been Studied by using Sievert's type apparatus. We have obtained dehydrogenation capacity of 2.7 wt% H-2 from Mg(AlH4)(2)+2NaCl during the first decomposition step at 140 degrees C and 1.1 wt% H-2 during second step decomposition at 280 degrees C. Efforts were carried out to reduce NaCl content from the product using Soxhlet extraction technique. The Soxhlet extracted product gives the total dehydrogenation capacity of 4.7wt% H-2. To enhance the storage capacity, we have synthesized a complex hydride consisting of mixture: xMg(AlH4)(2)+yNaAlH(4) (0 < x < 1, Y >= 1). In the alanate mixture 0.5Mg(AlH4)(2)+NaAlH4, the dehydriding temperature of NaAlH4 gets lowered by similar to 50 degrees C (from 190 degrees C to 140 degrees C with 4 times faster desorption kinetics. The total hydrogen liberated in 180 min from NaAlH4+0.5Mg(AlH4)(2)(+NaCl) mixture at 140 degrees C has been observed to be 3.7 wt% H-2. (c) 2007 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.