Impact of chemical and physical modification of zirconia on structure, surface state, and catalytic activity in oxidation of α-tetralol

Two series of ZrO 2 samples—pure ZrO 2 and ZrO 2 doped by 3% of Y 2 O 3 —prepared at 400, 500, and 600 °C were studied. The samples were characterized by powder XRD, TEM, SANS, IR spectroscopy, and nitrogen adsorption at 77 K. Monoclinic ZrO 2 was the dominating phase in the samples of pure zirconia, while Y-doped zirconia mainly consisted of tetragonal ZrO 2 . An increase in the calcination temperature led to the growth of the zirconia nanoparticle (NP) size and a decrease of the specific surface S BET . The size of Y-doped zirconia NPs (9–16 nm by XRD) was smaller compared to pure ZrO 2 (12–19 nm), synthesized at the same temperatures. The content of the surface defects in the tetragonal Y-doped ZrO 2 was estimated by analysis of IR spectra and other indicators and grew with the increase of the calcination temperature. The strength and content of the acidic surface sites were determined by potentiometric titration. The doping of ZrO 2 by Y 3+ led to the formation of the sites with lower pK a . The catalytic activity of ZrO 2 and Y-doped ZrO 2 in the reaction of α-tetralol oxidation by m -chloroperoxobenzoic acid was studied, and it was found that α-tetralone was the main product. The catalytic activity of the Y-doped zirconia samples in α-tetralol oxidation, expressed as conversion or turnover frequency (TOF) per 1 m 2 or ZrO 2 , increased with the increase of the total concentration of the surface acidic centers. Graphical abstract