Abstract
Polyoxometalates (POMs) are useful catalysts in both redox and acid catalysis reactions since its catalytic features can be controlled at a molecular level. We investigated POM (POM = H3PW12O40) on tantalum pentoxide (Ta2O5) via hydrolysis of tantalum pentachloride (TaCl5) in the presence of POM using the sol-gel method for acid catalytic reaction. All obtained amorphous materials have been characterized by inductively coupled plasma atomic emission spectroscopy (ICP-AES), Fourier transform infrared (FT-IR) spectra, Raman scattering spectroscopy, 31P magic-angle spinning (MAS) NMR, field emission scanning electron microscopy (FESEM), and nitrogen adsorption/desorption analysis, in order to confirm the structure integrity of the Keggin unit in as-prepared composites and investigate the morphology and surface textural property of the composites. Catalytic activity of the catalysts has been evaluated for esterification of acetic acid with ethanol as a model reaction with different catalytic reaction parameters such as POM loading, reaction time, catalyst dose, molar ratio of the reactants, etc. The conversion of ethanol reached 87.4 % and the turnover frequency (TOF) was 2.9×103.Meanwhile, it is easy to separate and recover POM/Ta2O5 from the reaction system.
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Funded by the National Natural Science Foundation of China (No.51002111), the Fundamental Research Funds for the Central Universities (No.2012-IV-085)
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Xu, L., Guo, Y., Ma, H. et al. Heterogeneous acid catalytic esterification by porous polyoxometalate-tantalum pentoxide nanocomposites. J. Wuhan Univ. Technol.-Mat. Sci. Edit. 28, 580–585 (2013). https://doi.org/10.1007/s11595-013-0734-1
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DOI: https://doi.org/10.1007/s11595-013-0734-1