Preparation and characterization of porous (Si$_{1-x}$Ti$_{{x}}$)$\hbox {O}_{\mathrm {{2}}}$ (x $\le$ 0.25) prepared by sol–gel hydrothermal process

Abstract

An experimental strategy was developed to obtain ($\hbox {Si}_{1-x}\hbox {Ti}_{x})\hbox {O}_{\mathrm {2}}$ ($x \le 0.25$) porous materials via the sol–gel hydrothermal process. The sol was prepared from Si(OEt)$_{\mathrm {4}}$ (TEOS), Ti(OBu)$_{\mathrm {4}}$ (OBu: $\hbox {OCH}_{\mathrm {2}}\hbox {CH}_{\mathrm {2}}\hbox {CH}_{\mathrm {2}}\hbox {CH}_{\mathrm {3}})$, anhydrous ethanol, deionized water and nitric acid. The reagents were mixed at room temperature (293 K) to obtain a homogeneous colourless liquid which was subjected to a hydrothermal process at 473 K using a stainless steel container. Finally, the material obtained was treated at 873 K in air. The surface area of the treated solids was determined by $\hbox {N}_{\mathrm {2}}$ adsorption/desorption isotherms. The corresponding average pore diameter was evaluated using the Barret, Joiner and Halenda and Horváth-Kawazoe methods. Porous structures were obtained, in which the average pore diameter of the microporous ones was 1.4 nm. The characterization techniques employed were Fourier transform infrared spectroscopy (FTIR), X-ray diffraction, Raman spectroscopy, scanning electron microscopy, thermal gravimetric analysis, differential scanning calorimetry and UV–Vis diffuse reflectance spectroscopy. The Si–O–Ti bonds were detected by FTIR.