Catalytic Activity Studies of Vanadia/Silica–Titania Catalysts in SVOC Partial Oxidation to Formaldehyde: Focus on the Catalyst Composition

Abstract

Abstract:In this work, silica-titania supported catalysts were prepared by a sol-gel method with various compositions. Vanadia was impregnated on SiO 2 -TiO 2 with different loadings, and materials were investigated in the partial oxidation of methanol and methyl mercaptan to formaldehyde. The materials were characterized by using N 2 physisorption, X-ray diffraction (XRD), X-ray fluorescence spectroscopy (XRF), X-ray photoelectron spectroscopy (XPS), Scanning transmission electron microscope (STEM), NH 3 -TPD, and Raman techniques. The activity results show the high importance of an optimized SiO 2 -TiO 2 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%V 2 O 5 /SiO 2 + 30%TiO 2 catalyst, the optimal selectivity was reached at 415 • C when the maximum formaldehyde concentration was~1000 ppm.

On the Activity and Selectivity of CoAl and CoAlCe Mixed Oxides in Formaldehyde Production from Pulp Mill Emissions

“…Based on the results (see Reactions 1 and 2) one can observe that formaldehyde formation starts when the temperature is above 160 • C. The maximum formaldehyde concentration (≈500 ppm) was reached at 380 • C with the CoAlCe catalyst and at 410 • C with the CoAl catalyst. Compared to our previous studies, the optimal formaldehyde formation temperature was lower or very similar with these mixed oxides and vanadium catalysts [53,58]. With our vanadium catalyst supported on titania-silica, alumina, zirconia and hafnia, the maximum formaldehyde concentration was achieved at 400-500 • C depending on vanadium loading and composition of the support [38,53,58].…”

“…Compared to our previous studies, the optimal formaldehyde formation temperature was lower or very similar with these mixed oxides and vanadium catalysts [53,58]. With our vanadium catalyst supported on titania-silica, alumina, zirconia and hafnia, the maximum formaldehyde concentration was achieved at 400-500 • C depending on vanadium loading and composition of the support [38,53,58]. However, even though the results look promising, the maximum concentration of formaldehyde stayed at a lower level with the Co containing mixed oxides than with the earlier tested vanadium catalysts.…”

“…Based on previous studies [58,63], it can be concluded that formaldehyde production requires an acidic catalyst. However, increasing the total acidity of the sample does not directly lead to better formaldehyde production [58,64]. According to the literature [65], weak acidic and basic sites enhance the selective oxidation of methanol to formaldehyde.…”

Synthesis of a high-surface area V2O5/TiO2–SiO2catalyst and its application in the visible light photocatalytic degradation of methylene blue

“…The reported materials have lower surface areas. 35,36 It is known that pure VO, porous titanosilicate or their chemical mixture produce negligible catalytic activity at room temperature for C-H oxidation and C-C bond breakage. However, they demonstrate the above activity in the gas phase or at higher temperatures, which require special reaction setups.…”

Editorial: Special Issue “New Concepts in Oxidation Processes”

“…The second paper, combining experiments and theory, emphasizes the degradation of commercial acetaminophen [2]. The use of heterogeneous catalysts is then highlighted in the frame of total oxidation of industrial VOCs using a CoAlCeO mixed-oxides catalyst as an alternative to precious-metal-based materials [3], but also for partial oxidation of sulfur-containing volatile organic compound (SVOC) using vanadia-based catalysts, proving the significant role of the composition of the support in the catalytic behavior [4].…”