Layered and nanosheet tantalum molybdate as strong solid acid catalysts

Layered and nanosheet aggregates of HTaMoO6 were examined as solid acid catalysts. The HTaMoO6 aggregated nanosheets were formed by soft chemical processing of layered HTaMoO6 using tetra (n-butylammonium) hydroxide. The catalytic activity and acid properties of the HTaMoO6 compounds were compared with those of layered HNbMoO6 and a range of conventional solid acids. The catalytic activity of HTaMoO6 for Friedel-Crafts alkylation with benzyl alcohol, hydrolysis of disaccharides, and esterification of acetic acid and lactic acid increased after exfoliation and aggregation, consistent with the acid strengths determined by NH3 temperature-programmed desorption and P-31, magic-angle spinning nuclear magnetic resonance spectroscopy measurements. HTaMoO6 nanosheets possess additional strong acid sites on the oxide formed by exposure of a single layer, along with strong acid sites within the interlayer of the layered aggregate structure, resulting in higher acid catalytic activity than that of the original layered oxide. (C) 2009 Elsevier Inc. All rights reserved.