An investigation on the reaction pathway between LiAlH4 and LiNH2 via gaseous ammonia

Interactions between LiAlH4 and LiNH2 through a gaseous ammonia intermediate have been investigated. LAlH4 and LiNH2 powders with a molar ratio of 1:1 were separated in two containers inside a reactor and heated from room temperature to 350 degrees C at a heating rate of 1 degrees C/min. The results showed that LiNH2 would decompose into Li2NH and NH3 to certain extent even at a relatively low temperature. Ammonia then reacted with Al and LiH that decomposed from LiAlH4, whereupon the chemical equilibrium of the system was altered and the initial reaction temperature was lowered. Ammonia decomposed from LiNH2 acted as an intermediate. A pathway for the thermal decomposition of the system was proposed as: [GRAPHICS] The heating rate and initial molar ratio of reactants will affect the value of m, thus the final resultants vary. The theoretical hydrogen desorption capacity of the system was calculated to be in the range of 7.39-7.88 wt.% and a total desorption capacity of 7.37 wt.% was obtained by thermal decomposition. (C) 2009 Elsevier B.V. All rights reserved.