Key points are not available for this paper at this time.
Early transition metal oxides, TiO 2, ZrO 2, and Nb 2 O 5, were studied as heterogeneous catalysts for the Meerwein–Ponndorf–Verley (MPV) reduction of cyclohexanone in 2-propanol. Despite a small amount of Lewis acid sites and weak Lewis acid strength, ZrO 2 was clearly superior to TiO 2 and Nb 2 O 5 with respect to reaction rate. Fourier transform infrared spectroscopy (FT-IR) and temperature-programmed-desorption (TPD) measurements revealed that ZrO 2 has large amounts of base sites that activate the methylene groups in 2-propanol bonded to Lewis acid sites. Various analyses, including experiments using isotopic 2-propanol, suggest that efficient MPV reduction over ZrO 2 is due not only to Lewis acid strength and density, but also to a synergistic effect of base and Lewis acid sites.
Komanoya et al. (Mon,) studied this question.