Incorporation of clusters of titanium oxide in Beta zeolite structure by a new cold TiCl4-plasma process: physicochemical properties and photocatalytic activity

Abstract

A new post-synthetic approach, involving cold plasma treatment, was employed for the preparation of TiO₂–Beta zeolite. Zeolite Beta nanoparticles were first subjected to plasma induced deposition of TiCl_y (with y ≤ 3), which were further converted into TiO_x (with x ≤ 2) upon O₂-plasma treatment. Different steps of the new elaborated plasma approach were monitored using in situ FTIR spectroscopy. D₂O isotopic exchange was used in order to shed light on the formation of Si–O–Ti bonds induced by TiCl₄-plasma followed by O₂-plasma treatments. The obtained TiO₂–Beta materials were studied by a set of complementary characterization techniques including FTIR, TEM, SEM-EDS, XRD, N₂ sorption, NMR and UV-Vis. The silanol content and the acidic properties of TiO₂–Beta composites were also studied. The elaborated materials were tested as photocatalysts for methanol photooxidation in the gas phase. TiO₂–Beta presents a methanol photooxidation rate 8 times higher than a conventional P25-TiO₂ catalyst under UV irradiation.