Influence of the host oxide of sulfated-titania catalysts on partial oxidation methanol reaction

A series of sulfated binary titania-based (MxOy–TiO2–SO42−, Mx = Cr, Mn, Fe, Co or Mo) catalysts were prepared by co-precipitation and tested for partial oxidation of methanol. The structural properties were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The acidic and redox properties were examined using ammonia adsorption calorimetry and temperature-programmed reduction coupled with mass spectrometry (TPR–MS) techniques, respectively. The surface Mx species were essentially 100% dispersed on catalysts, as confirmed by XRD and Raman spectroscopy characterization. XPS results indicated the oxidation state of surface Mx species. In addition, Ti and S species were present in their fully oxidized states for all the samples. The results of ammonia adsorption calorimetry showed a surface reaction between chromium oxide and ammonia. The addition of MxOy host oxide not only enhanced the redox properties of sample TiS but also brought changes in the sulfate reduction process, as investigated by TPR–MS. The best catalytic performance was obtained for sample MoO3–TiO2–SO42− with high activity. Furthermore, the distribution of reaction products was examined to provide information about the surface acidity and redox properties simultaneously.

Figure optionsDownload high-quality image (80 K)Download as PowerPoint slideResearch highlights▶ SO2 and H2S identification during TPR analysis of sulfated catalysts. ▶ DMM selectivity scale for different sulfated oxide catalysts: VTiS > MoTiS > CrTiS > FeTiS > MnTiS > CoTiS.