A procedure for the regeneration of ammonia borane from BNH-waste products

Ammonia borane BH3NH3BH3NH3 has attracted considerable interest in the last years as a hydrogen source material due to its high hydrogen content of 19.6 wt%. The release of hydrogen from solid ammonia borane leads to the formation of polymeric waste products. In order to make ammonia borane a promising material for applications in the hydrogen economy, an energy-efficient procedure for the regeneration of BH3NH3BH3NH3 from these waste products should be developed. A concept for such a procedure is outlined. The proposed recycling strategy is described by a self-contained reaction scheme, in which only BNH-waste and molecular hydrogen are consumed. The key step in this strategy is the hydrodechlorination of a BCl3·BCl3·base adduct with molecular hydrogen in the presence of the base in excess. The base used is only an auxiliary reactant and can be recovered in principle by the thermal decomposition of the obtained base··HCl adduct. The criteria for a proper selection of the base, which is the critical parameter for the development of an energy-efficient regeneration procedure, are discussed.