Physiochemical Pathway for Cyclic Dehydrogenation and Rehydrogenation of LiAlH4

• Published in: Journal of the American Chemical Society Vol. 128; no. 17; pp. 5949 - 5954
• Main Authors: Wang, Jun, Ebner, Armin D, Ritter, James A
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 03.05.2006
• Subjects: Chemistry; Exact sciences and technology; Inorganic chemistry and origins of life; Kinetics and mechanism of reactions; Alkali metal Compounds; Kinetic control; Organic solvent; Thermodynamic control; Catalytic reaction; Lithium Tetrahydroaluminates; Dehydrogenation; Transition metal Compounds; Reaction mechanism; Titanium chloride; Experimental study; Catalyst
• ISSN: 0002-7863; 1520-5126
• DOI: 10.1021/ja060045l

A five-step physiochemical pathway for the cyclic dehydrogenation and rehydrogenation of LiAlH4 from Li3AlH6, LiH, and Al was developed. The LiAlH4 produced by this physiochemical route exhibited excellent dehydrogenation kinetics in the 80−100 °C range, providing about 4 wt % hydrogen. The decomposed LiAlH4 was also fully rehydrogenated through the physiochemical pathway using tetrahydrofuran (THF). The enthalpy change associated with the formation of a LiAlH4·4THF adduct in THF played the essential role in fostering this rehydrogenation from the Li3AlH6, 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 LiAlH4 at ambient temperature and pressures of 4.5−97.5 bar.