Elsevier, Catalysis Today, 1(178), p. 187-196
DOI: 10.1016/j.cattod.2011.08.003
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A series of non-periodic mesoporous silicas impregnated with both framework and nanocrystalline sulfated zirconia was prepared by a sol–gel process using an ionic liquid as a template. The physico-chemical properties of the mesoporous sulfated zirconia materials are described. Analysis of the new silicas indicates isomorphous substitution of silicon with zirconium and reveals the presence of extremely small (<10 nm) polydispersed zirconia nanoparticles in the materials with zirconium loadings of 28–41 wt.%. The materials with higher zirconium loadings catalyse the Meerwin–Ponndorf–Verley reductions of alde-hydes and ketones for substrates with hydrogen-bond basicities, pK HB > 1.10. In order to explain the catalytic activity, analysis of the acid sites of the materials using pyridine as a probe molecule reveals that in all cases the majority are Bronsted acid sites, with only a small number of Lewis acid sites present in those materials with low zirconium loadings.