Influence of the Preparation Procedure of Vanadium-Containing SiBEA Zeolites on Their Catalytic Activity in Propene Epoxidation

Two series of V-containing BEA zeolite catalysts, VxSiBEA(I) and VxSiBEA(II), were prepared by a two-step postsynthesis preparation procedure which consists, in the first step, in the dealumination of TEABEA zeolites by a treatment with nitric acid solution to obtain SiBEA zeolites with a Si/Al atomic ratio of 1000 and then, in the second step, in bringing SiBEA into contact with an aqueous NH4VO3 solution with different concentrations at a pH of 2.7. After 3 days, the solids were recuperated from the reaction mixtures: (1) on a sinter funnel and washed several times with distilled water to obtain the VxSiBEA(I) series and (2) in a rotating evaporator under vacuum via a membrane pump to obtain the VxSiBEA(II) series. The combined use of H2-temperature-programmed reduction, diffuse reflectance (DR) UV–vis, Fourier transform infrared (FTIR), 51V magic-angle spinning (MAS) NMR, electron paramagnetic resonance (EPR), and X-ray photoelectron spectroscopy allows determining the nature and environment of vanadiu...