Abstract
In this work, silica–titania supported catalysts were prepared by a sol–gel method with various compositions. Vanadia was impregnated on SiO2-TiO2 with different loadings, and materials were investigated in the partial oxidation of methanol and methyl mercaptan to formaldehyde. The materials were characterized by using N2 physisorption, X-ray diffraction (XRD), X-ray fluorescence spectroscopy (XRF), X-ray photoelectron spectroscopy (XPS), Scanning transmission electron microscope (STEM), NH3-TPD, and Raman techniques. The activity results show the high importance of an optimized SiO2-TiO2 ratio to reach a high reactant conversion and formaldehyde yield. The characteristics of mixed oxides ensure a better dispersion of the active phase on the support and in this way increase the activity of the catalysts. The addition of vanadium pentoxide on the support lowered the optimal temperature of the reaction significantly. Increasing the vanadia loading from 1.5% to 2.5% did not result in higher formaldehyde concentration. Over the 1.5%V2O5/SiO2 + 30%TiO2 catalyst, the optimal selectivity was reached at 415 °C when the maximum formaldehyde concentration was ~1000 ppm.
Highlights
Silicon dioxide SiO2 and titanium dioxide TiO2 support materials are used extensively in academic research and in industrial applications
The results indicate that the good performance of single oxide Si or Ti supported catalysts requires requires an oxidation temperature over 500 °C—which we did not test—since lower temperatures an oxidation temperature over 500 ◦ C—which we did not test—since lower temperatures are more are more interesting from an energy point of view, and because vanadium pentoxide as the catalyst interesting from an energy point of view, and because vanadium pentoxide as the catalyst material material sets some limits to the activity testing
V2 O5 catalysts supported on SiO2 -TiO2 have been characterized and tested in the oxidation of methanol and methyl mercaptan to formaldehyde
Summary
Silicon dioxide SiO2 and titanium dioxide TiO2 support materials are used extensively in academic research and in industrial applications. Mixed SiO2 -TiO2 materials have attracted many researchers, because it has been shown that mixed SiO2 -TiO2 materials can provide certain advantages over single oxides. Benefits such as stronger metal–support interactions, higher acidity compared to single oxides, better resistance to sintering, and resistance against sulfur poisoning have been observed in earlier studies [1,2,3,4,5,6,7]. The sol–gel preparation steps include sol (colloid suspension) preparation, alkoxysilane hydrolysis, and condensation of silica and titania precursors. This leads to a structure where Ti is homogeneously dispersed in the silica matrix, which often results in better activity in oxidation applications. Due to the advantages of silica–titania supports, they are used as supports for vanadia-containing catalysts in different applications [10,11,12,13,14,15,16,17,18]
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