A series of tetrabutyl ammonium (TBA) salts of V-included Keggin-type polyoxoanions with W (TBA₄PW₁₁V₁O₄₀ and TBA₅PW₁₀V₂O₄₀) and Mo (TBA₄PMo₁₁V₁O₄₀ and TBA₅PMo₁₀V₂O₄₀) as addenda atoms were prepared using a hydrothermal method. These synthesized materials were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), UV-Vis diffuse reflectance (DRS UV-Vis), thermogravimetric analysis (TGA), CHN elemental analysis (EA), inductively coupled plasma spectrometry (ICP-MS), and N₂ physisorption techniques to assess their physicochemical/textural properties and correlate them with their catalytic performances. According to FT-IR and DRS UV-Vis, (PV_XW(Mo)_12−XO₄₀)^(3+X)− anions are the main species present in the TBA salts. Additionally, CHN-EA and ICP-MS revealed that the desired stoichiometry was obtained. Their catalytic activities in the liquid-phase aerobic oxidation of benzyl alcohol to benzaldehyde were studied at 5 bar of O₂ at 170 °C. Independently of the addenda atom nature, the catalytic activity increased with the number of V in the Keggin anion structure. For both series of catalysts, TBA salts of polyoxometalates with the highest V-substitution degree (TBA₅PMo₁₀V₂O₄₀ and TBA₅PW₁₀V₂O₄₀) showed higher activity. The maximum benzyl alcohol conversions obtained were 93% and 97% using (TBA)₅PMo₁₀V₂O₄₀ and (TBA)₅PW₁₀V₂O₄₀ as catalysts, respectively. In all the cases, the selectivity toward benzaldehyde was higher than 99%.

Magnetic materials based on Keggin heteropolyacids immobilized on mesoporous silica-coated magnetite particles with a core-shell structure were synthesized. The activity of the catalyst was studied in the esterification reaction of levulinic acid with n-butanol, and its kinetics was studied by the systematic variation of several reaction parameters, such as stirring speed, catalyst loading, molar ratio of reactants, and temperature. It was also seen that the reaction was free from any external mass transfer as well as intraparticle diffusion limitations and was intrinsically kinetically controlled. A second-order kinetic equation was found to be consistent with the experimental data. Also, an experimental activation energy of 17 kcal/mol was found. A solvent-free condition for this reaction has also added the green chemistry perception to the reaction. In addition, the resulting catalyst can be used repeatedly without significant decrease in activity.