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A series of WO3-SBA-15 materials with different Si/W ratios have been hydrothermally synthesized using tetraethyl orthosilicate (TEOS) as silica precursor, ammonium paratungstate as tungsten precursor, and EO20PO70EO20 (P123) as structure-directing reagent. After temperature-programmed carburization (TPC) in flowing CH4/H2 (20/80 v/v mixture), the materials were converted to the corresponding W x C-SBA-15 materials. The structure of the oxide and carbide materials has been characterized using X-ray diffraction (XRD), X-ray fluorescence (XRF), nitrogen adsorption−desorption measurements, 29Si magic-angle spinning (MAS) NMR spectroscopy, Fourier transform infrared (FTIR) spectroscopy, transmission electron microscopy (TEM), and thermogravimetric and differential scanning calorimetric analysis (TG-DSC) measurements. The results show that after hydrothermal synthesis using different amounts of tungsten and subsequent carburization, the materials retain the mesopore structure of SBA-15. When Si/W = 30−15, the majority of the tungsten is dispersed in the channels of SBA-15 with the remainder being incorporated into the framework of SBA-15 with the formation of Si−O−W bonds. The tungsten carbide exists as a single W2C phase after carburization. At higher tungsten content (Si/W = 7.5), the amount of tungsten in the framework of SBA-15 increases with the formation of both Si−O−W bonds and W−O−W bonds. The tungsten carbide formed after carburization exists as a mixture of W2C and WC phases. A model for the distribution of tungsten in SBA-15 is proposed involving three different tungsten species:  α-W inside SBA-15 channels, β-W embedded in the internal surfaces of the SBA-15 channels, and γ-W inside the framework of SBA-15. After temperature-programmed carburization, α-W sites are transformed into W2C, whereas β-W sites afford WC; in contrast, γ-W sites show little change after carburization.

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A series of WO3/SBA-15 materials with different Si/W ratios have been prepared by impregnating the host material SBA-15 with aqueous ammonium paratungstate solutions. After temperature-programmed carburization (TPC) in flowing CH4/H2 (20/80 v/v mixture), the materials are converted to the corresponding W2C/SBA-15 species. Both the oxide and carbide materials are characterized using X-ray diffraction, nitrogen adsorption-desorption, 29Si NMR spectroscopy, Fourier transform infrared (FTIR) spectroscopy, and TEM measurements. The XRD results show that after impregnation with different amounts of tungsten and subsequent carburization, the materials retain the mesopore structure of SBA-15. The nitrogen adsorption-desorption results indicate that a thin layer of W2C covers the internal walls of SBA-15. Quantitative 29Si single-pulse excitation MAS experiments and FTIR spectroscopy show that the incorporation of W2C in the channels of SBA-15 is correlated with the formation of Si-O-W bonds. Some Si-O-W bonds are transformed into Si-O-H bonds after carburization. The TEM results show that the thickness of the W2C thin layer is 1.7-1.9 nm in W2C/SBA-15. A model involving a discrete W2C thin layer in the channels of SBA-15 is proposed on the basis of the NMR data. The calculated thickness of the discrete W2C thin layer is consistent with value given by HRTEM.