Thermochemical transformations in 2MNH(2)-3MgH(2) systems (M = Li or Na)

TitleThermochemical transformations in 2MNH(2)-3MgH(2) systems (M = Li or Na)
Publication TypeJournal Article
Year of Publication2010
AuthorsDolotko O, Paulson N, Pecharsky VK
Journal TitleInternational Journal of Hydrogen Energy
Volume35
Pages4562-4568
Date Published05/01
ISBN Number0360-3199
Accession NumberISI:000278418700013
Keywordsamides, complex hydrides, destabilization, h system, hydrides, hydrogen release, hydrogen storage-system, imides, mg3n2, temperature programmed dehydrogenation, x-ray diffraction
Abstract

Thermochemical reactions between alkali metal amides and magnesium hydride taken in 2:3 molar ratios have been investigated using pressure-composition-temperature, X-ray powder diffraction and residual gas analysis measurements. The thermally induced reactions in both title systems are stoichiometric and proceed as a following solid state transformation: 2MNH(2)+ 3MgH(2) -> Mg3N2 + 2MH + 4H(2)up arrow. A total of 6.45 wt.% of hydrogen is released by the 2LiNH(2)-3MgH(2) system beginning at 186 degrees C, and a total of 5.1 wt.% H-2 is released by the 2NaNH(2)-3MgH(2) system starting at 130 degrees C. Combined structure/property investigations revealed that the transformation in the lithium containing system proceeds in two steps. In the first step, lithium amide reacts with MgH2 to form Li2Mg(NH)(2) and hydrogen. In the second step, reaction between Li2Mg(NH) and MgH2 leads to the formation of the Mg3N2 nitride, lithium hydride and additional gaseous hydrogen. The transformation in the sodium containing system appears to proceed through a series of competing solid state processes with formation of Mg(NH2)(2) and NaMgH3 intermediates. Partial rehydrogenation in 190 bar hydrogen pressure leading to formation of the MgNH imide was observed in the dehydrogenated 2NaNH(2)-3MgH(2) system at 395 degrees C. (C) 2010 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved.

URL<Go to ISI>://000278418700013
DOIDoi 10.1016/J.Ijhydene.2010.02.104