Synthesis and Physicochemical and Catalytic Properties of Composites in the SiO2–ZrO2 System

Abstract

Using coprecipitation, a sol–sol method, and molecular layering, we have synthesized SiO2–ZrO2 composites with SiO2 : ZrO2 ratios from 1 : 1 to 9 : 1 and a large specific surface area, which increases with growth silicon-containing component concentration. Using adsorption of Hammett indicators, we have assessed the concentration of acid–base centers in the pK range 1.3–9.6, which has been shown to vary from 68 to 160 μmol/g. Elemental analysis and IR spectroscopy data have demonstrated the presence of not only water but also nitrate ions and carbon dioxide on the surface of the samples. It has been shown that the use of nanoparticulate SiO2–ZrO2 oxides as heterogeneous catalysts—promoters for (2S,4R)-4-hydroxyprolyl-(S)-1-phenylethylamine trifluoroacetate, a chiral inducer in the asymmetric Biginelli reaction, makes it possible to raise ee (enantiomeric excess) from 39 to 68% and the reaction yield from 29 to 55%.