The synthesis of lithium dialuminate LiAl2(0H)7.2H20 by reaction at room temperature of solid lithium hydroxide, polycrystalline aluminum trihydroxide (bayerite), and water vapor is described. The aluminate prepared by this method has been characterized by chemical analysis, thermogravimetric analysis, infrared spectroscopy, and X-ray powder diffraction and appears to be identical with that prepared by precipitation from supersaturated aluminate solutions or by reaction of lithium salts with freshly precipitated aluminum hydroxide in aqueous solution. All current evidence suggests that the structure of lithium dialuminate is like that of hydrotalcite, [Mg6Al2(0H)i6]2+C032“-4H20, with neutral dioctahedral sheets of bayerite converted to positively charged trioc-tahedral layers by incorporation of lithium ion. Hydroxide ion and two water molecules reside between the layers and presumably approximate a plane of oxygen atoms stabilized by hydrogen bonding, as evidenced by a 2.81 (1) A increase in the bayerite lattice perpendicular to the dioctahedral layer. A more descriptive chemical formula for lithium dialuminate would be [LiAl2-(OH)6]+OH” 2H20. The imbibition of other lithium salts (LiX; X = CL, Br”, I”, N03”) was also studied. Thermal decomposition results in compounds, related to the transitional aluminas, with high specific surface area and porosity.
ASJC Scopus subject areas
- Physical and Theoretical Chemistry
- Inorganic Chemistry