Optimization of Mn‐Mg‐Al Mixed Oxides Composition on their Activity towards the Total Oxidation of Aromatic and Oxygenated VOCs

Abstract

A series of mixed oxides (Mn-Mg-Al) is prepared by coprecipitation via a hydrotalcite route with different manganese ratios. Structural, textural, and redox properties are studied by XRD, N 2 -sorption, H 2 -TPR, and XPS techniques. Mn x Mg 6-x Al 2 -O mixed oxides (with 0 � x � 6) are tested in the total oxidation of ethanol and toluene, two probe molecules representing respectively oxygenated and aromatic VOCs. Catalysts with higher manganese contents have shown the best catalytic performance for the oxidation of both ethanol and toluene. The surface activity of the materials is mainly related to the presence of manganese species in three different oxidation states (+ II, + III, and + IV) in the bulk and on the material's surface. Since high Mn-content catalysts showed similar physicochemical properties and catalytic activity, Mn 4 Mg 2 -O is selected as the optimal composition of these materials. Furthermore, its aging test is compared to that of noble metalbased commercial catalysts (Pd/γ-Al 2 O 3 ).

Synthesis of Gold Nanoparticles over CoAl Mixed Oxide for Ethanol Oxidation Reaction

“…First of all, the reduction profile of all samples showed some similar behavior, with two reduction steps: the first one at low temperature (T < 400 °C), corresponding to a reduction in the Co3O4 phase to Co 0 , and the second one at higher temperature, with a reduction in Co-Al spinel phases (CoAl2O4 and Co2AlO4). This reduction is well documented in the literature [14,[26][27][28][29][30]. Concerning the gold-based catalysts, it was observed that the 1Au/CoAl HT (A) showed the first reduction zone at higher temperature compared to the Au/CoAl HT (B) samples, while the presence of gold did not influence the position of the second peak, which remained centered at around 750 °C.…”

“…Looking at the hydrogen consumption (Table 2), it is worth noting that the 1Au/CoAl HT (A) exhibited the highest values for both peaks at both low and high temperature, whereas the hydrogen consumed by all the catalysts prepared with method (B) was the First of all, the reduction profile of all samples showed some similar behavior, with two reduction steps: the first one at low temperature (T < 400 • C), corresponding to a reduction in the Co 3 O 4 phase to Co 0 , and the second one at higher temperature, with a reduction in Co-Al spinel phases (CoAl 2 O 4 and Co 2 AlO 4 ). This reduction is well documented in the literature [14,[26][27][28][29][30]. Concerning the gold-based catalysts, it was observed that the 1Au/CoAl HT (A) showed the first reduction zone at higher temperature compared to the Au/CoAl HT (B) samples, while the presence of gold did not influence the position of the second peak, which remained centered at around 750 • C. The reduction in the active Co 3 O 4 phase at lower temperature for Au catalysts prepared with method (B) can be explained by the strong interaction between Au nanoparticles and Co 3 O 4 species [31][32][33].…”

“…The principal by-products observed were acetaldehyde, methanol, ethylene, and, in lesser quantities, acetic acid, formic acid, diethyl ether, and ethyl acetate. The formation of acetaldehyde can either be formed from partial oxidation or by dehydrogenation at high temperatures of ethanol [26,27]. Traces of diethyl ether is formed by the dimerization of two ethanol molecules, while ethylene is produced by the dehydration of ethanol.…”

Catalytic Ozonation of Ethyl Acetate with Assistance of MMn2O4 (M = Cu, Co, Ni and Mg) Catalysts through In Situ DRIFTS Experiments and Density Functional Theory Calculations

“…At around 210 • C, the conversion of EA reached nearly 100% for the activation of abundant oxygen vacancies. Moreover, it has been discovered that the synergistic effects of composite oxides contribute to the significant enhancement of catalytic activities, such as Cu-Mn-O [17], Co-Mn-O [18], Ni-Mn-O [19] and Mg-Mn-O [20]. Due to its lower working temperature and higher selectivity to CO 2 , catalytic ozonation has become one of the popular methods for VOC degradation in recent years.…”

Total Catalytic Oxidation of Ethanol over MnCoAl Mixed Oxides Derived from Layered Double Hydroxides: Effect of the Metal Ratio and the Synthesis Atmosphere Conditions

“…Moreover, in our recent work [21], we tested the ethanol oxidation over Mn x Mg (6−x) Al 2 -O (x = 0-6) catalysts obtained by LDH thermal decomposition. It was established that the ethanol transformation was influenced by the metal ratio, and the Mn 4 Mg 2 Al 2 -O catalyst exhibited superior activity compared to the supported metal Pd/γ-Al 2 O 3 .…”