Morphology dependent effect of γ-Al2O3 for ethanol dehydration: nanorods and nanosheets

Abstract

Boehmite (γ-AlOOH) nanorods and nanoplates were hydrothermally fabricated with the aid of tetrapropylammonium bromide (TPABr) by modifying the pH values of solutions. Under acidic conditions, the adsorption of anions such as Br⁻ or NO₃⁻ on (001) and (100) surfaces may promote the heterogeneous nucleation of boehmite, leading to rod-like boehmite. While under basic solutions, the adsorption of TPA⁺ cation on the (010) surface inhibits the growth of boehmite along the [010] direction and generates nanosheets. The as-synthesized γ-AlOOH precursors were calcined at 873 K and transformed into γ-Al₂O₃ nanorods and nanosheets. The obtained γ-Al₂O₃ samples presented a clear morphology-depended effect for ethanol dehydration; nanorods gave the improved selectivity of C₂H₄ due to the exposure of {100} facets.