Catalytic activity studies of vanadia/silica–titania catalysts in SVOC partial oxidation to formaldehyde : focus on the catalyst composition
Koivikko, Niina; Laitinen, Tiina; Mouammine, Anass; Ojala, Satu; Keiski, Riitta L. (2018-02-02)
Koivikko, N.; Laitinen, T.; Mouammine, A.; Ojala, S.; Keiski, R.L. Catalytic Activity Studies of Vanadia/Silica–Titania Catalysts in SVOC Partial Oxidation to Formaldehyde: Focus on the Catalyst Composition. Catalysts 2018, 8, 56.
© 2018 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).
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.
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