Abstract
A set of cerium–manganese–copper oxide catalysts with various foreign metal contents was prepared via the solution combustion synthesis (SCS). The catalysts were characterized by complementary techniques such as N2 physisorption at − 196 °C, X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), H2-temperature-programmed reduction (H2-TPR), O2-temperature-programmed desorption (O2-TPD) and X-ray photoelectron spectroscopy (XPS). Their catalytic activity was tested towards the VOC oxidation using ethylene and propylene as probe molecules. As a whole, it has been observed that the Ce55Mn45 sample (Mn 45 at.%), containing MnOx clusters interacting with the ceria phase, was the most active catalyst for propylene oxidation, exhibiting a complete conversion at 250 °C. On the other hand, the ternary oxide catalyst (Ce55Mn22.5Cu22.5 with Mn = 22.5 at.% and Cu = 22.5 at.%) has exhibited the best results for the oxidation of ethylene. These findings suggest that the co-presence of different active phases on the catalytic surface may have a beneficial (multiplicative) role on the whole reactivity. Finally, the most active powder catalysts were wash-coated in a SiC monolith and tested in a bench-scale reactor. As a whole, the catalyzed monoliths performed the complete oxidation of either ethylene or propylene at lower temperatures (550 and 450 °C, respectively) than those required to thermally decompose these molecules.Graphic
Highlights
Volatile organic compounds (VOCs) include any organic substance having a boiling point equal or lower than 250 °C at standard pressure (i.e. 101.3 kPa)
The diffraction peaks correspond to the fluorite structure of cerium (IV) oxide, with a face-centered-cubic-structure containing octahedral and hexahedral holes filled with oxygen ions [17]
In the diffractograms of the binary and ternary oxides with 45% metal content were observed the peaks corresponding to pure oxides of copper or manganese (CuO ref. code 00-045-0937; M n2O3 ref. code 01-078-0390) and mixed copper-manganese oxide (Cu1.5Mn1.5O4 ref. code 01-070-0260), suggesting the presence of extra-framework species from the lattice
Summary
Volatile organic compounds (VOCs) include any organic substance having a boiling point equal or lower than 250 °C at standard pressure (i.e. 101.3 kPa). Since the MvK mechanism occurs through oxygen species from the solid, the “redox-flexibility” of the material becomes a key factor for the catalytic oxidation reaction Both the electronic and structural changes caused by the introduction of foreign metals in the ceria lattice seem to be beneficial toward the VOC oxidation reactions. The catalysts were characterized by the N2 physisorption at − 196 °C, X-ray diffraction analysis, X-ray photoelectron spectroscopy, H2 temperature-programmed reduction, O2 temperature-programmed desorption and field emission scanning electronic microscopy Their catalytic activity was tested towards VOC oxidation reactions, using ethylene and propylene as probe molecules. The catalyzed monoliths were tested for the VOC oxidation in a bench-scale reactor
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