Cerium–Copper–Manganese Oxides Synthesized via Solution Combustion Synthesis (SCS) for Total Oxidation of VOCs

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 Abstract

Catalytic Abatement of Volatile Organic Compounds and Soot over Manganese Oxide Catalysts

“…Accordingly, the results demonstrate the key role played by active O α -species and catalyst reducibility in the elimination of ethene. In fact, according to the literature, a number of these species may promote VOC catalytic oxidation at lower temperatures in conjunction with low-temperature reducibility [ 20 , 21 , 27 , 40 ]. Overlooking the catalytic behavior observed during the abatement of the VOCs, it was evident that catalysts that belong to the same group or family could present different catalytic performances according to the abated molecule.…”

Direct Decomposition of NO over Co-Mn-Al Mixed Oxides: Effect of Ce and/or K Promoters

“…The decreasing total volume of pores (Table 2) can confirm this idea. their composition, as surface area decreases with increasing K concentration in the catalysts [14]. In the pore size distributions, one can observe some differences.…”

“…All catalysts revealed a broad, monodisperse pore structure with the diameter w max of the peak ranging from 11 to 5 nm. The textural properties of the catalysts obviously reflect their composition, as surface area decreases with increasing K concentration in the catalysts [14]. In the pore size distributions, one can observe some differences.…”

“…Some authors studied the effect of cerium in transition mixed oxides on their activity in various catalytic reactions [14][15][16][17][18][19]. Ceria (CeO 2 ) has demonstrated effectiveness in catalysis due to its redox properties and oxygen storage capacity [14] as well as its ability to approve the Mars-Van Krevelen mechanism of reaction. Since this mechanism occurs through oxygen species from the solid, the mobility of oxygen becomes an important factor for the catalytic reaction.…”

“…Since this mechanism occurs through oxygen species from the solid, the mobility of oxygen becomes an important factor for the catalytic reaction. Thus, both the electronic and structural changes caused by the introduction of foreign metals in the ceria lattice seem to be advantageous toward the volatile organic compound oxidation reactions [14]. Interaction between CeO 2 and transition metals leads to the increased mobility of lattice oxygen atoms of CeO 2 [15], which are mobile, rapidly change the state of surface oxygen vacancies, and enhance the reducibility of the adjacent metal particles.…”