Synthesis of lithium octahydrotriborate and investigation on its thermal decomposition

Octahydrotriborates are found to be key intermediates in the dehydrogenation of many borohydrides. In this work, LiB3H8 center dot 1.5THF is synthesized via the reaction between lithium amalgam and BH3 center dot THF. The structure is confirmed by B-11 NMR and FT-IR spectrometry. The synthetic reaction of LiB3H8 center dot 1.5THF is monitored by using B-11 NMR. Some boron hydrides, LiB2H7 and LiB4H9, are found to be possible intermediates in this reaction. Thermal dehydrogenation analyses including TPD/MS and TG suggest 6 successive decomposition steps upon heating to 500 degrees C. The compound emits THF, diborane, pentaborane(9) and hydrogen simultaneously below 170 degrees C and emits almost pure hydrogen at elevated temperature. LiBH4 is formed at 170 degrees C as one of the products and disappears at 400 degrees C. At least two kinds of other intermediates are found in the decomposition reaction, with one of them suspected to be Li2B12H12. Copyright (C) 2015, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.