Physiochemical Pathway for Cyclic Dehydrogenation and Rehydrogenation of LiAIH_4

摘要

A five-step physiochemical pathway for the cyclic dehydrogenation and rehydrogenation of LiAlH_4 from Li_3AlH_6,LiH,and Al was developed.The LiAlH_4 produced by this physiochemical route exhibited excellent dehydrogenation kinetics in the 80-100 degC range,providing about 4 wt % hydrogen.The decomposed LiAlH_4 was also fully rehydrogenated through the physiochemical pathway using tetrahydrofuran (THF).The enthalpy change associated with the formation of a LiAlH_4 centre dot 4THF adduct in THF played the essential role in fostering this rehydrogenation from the Li_3AlH_6,LiH,and Al dehydrogenation products.The kinetics of rehydrogenation was also significantly improved by adding Ti as a catalyst and by mechanochemical treatment,with the decomposition products readily converting into LiAlH_4 at ambient temperature and pressures of 4.5-97.5 bar.