Mechanism of complete n-hexane oxidation on silica supported cobalt and manganese catalysts

Mixed Co–Mn Oxide‐Catalysed Selective Aerobic Oxidation of Vanillyl Alcohol to Vanillin in Base‐Free Conditions

“…The MnCo-MO catalyst also showed a broad signal of Mn 2p 3/2 , which could be fitted satisfactorily to three major peaks and a satellite peak after deconvolution, as shown in Figure 2 c. The peaks at 640.4, 641.4 and 642.4 eV correspond to Mn 2 + , Mn 3 + and Mn 4 + , respectively, [9,34,35] whereas the small The manner in which oxygen is bonded to metals in metal oxides can be determined through XPS of oxygen. In this series, the O 1s spectrum was used to identify the types of metal oxides present in MnCo-MO catalyst.…”

“…[8] The catalytic properties of Mn-doped Co 3 O 4 catalyst are attributed to the ability of manganese to form oxides of different stoichiometries or mixed-valence compounds and their high oxygen storage capacity. [9] These metals (Co and Mn) are commonly used for oxidation reactions and also are more economical than noble-metal-based catalysts. Despite the large number of studies on single-component manganese [10][11][12] and cobalt oxides [13][14][15][16] and very few on mixed cobalt and manganese oxides for oxidation of volatile organic compounds (e.g., benzene and toluene), there is no single report addressing the catalytic properties based on the structural attributes of combinations of these two oxides for the aerobic oxidation of vanillyl alcohol, which is an industrially important phenolic starting compound.…”

Catalytic oxidation of volatile organic compounds (n-hexane, benzene, toluene, o-xylene) promoted by cobalt catalysts supported on γ-Al2O3-CeO2

“…Another factor to be considered is the mobility of the oxygen atoms present, which are able to perform the oxidation of the hydrocarbons under study. It has been reported that the presence of oxygen vacancies is an important factor that influences the activity of some heterogeneous catalysts and favors the oxidation process (Luo et al, 2008;Tian et al, 2012;Todorova et al, 2012). An increase in the amount of oxygen vacancies can result in an enhancement of the bulk and surface oxygen mobility, which is believed to play an important role in oxidation reactions (Liotta et al, 2005;Soykal et al, 2012a;Sun et al, 2008).…”

“…The higher oxygen mobility benefits the oxygen species migration across the catalyst structure, resulting in higher oxidation activity (Song et al, 2009). It has been shown that the reduction in cerium oxide (Ce +4 /Ce +3 ) is not due to a direct release of oxygen into the gas phase, but rather to the interaction which occurs between the surface of the catalyst and the hydrocarbon (Putna et al, 1999;Suresh et al, 2012;Todorova et al, 2009;Todorova et al, 2012). These reactions are driven by the increased capacity for the spontaneous release of oxygen from the Co 3 O 4 /CeO 2 system, even in the absence of a reducing agent.…”

“…The addition of cobalt in the CeO 2 structure reduces the lattice parameter, suggesting the incorporation of Co 3 O 4 by way of Co-O-Ce bonds (Kang et al, 2003;Murgida et al, 2012). It is well known that the oxidation of hydrocarbons promoted by solid oxide catalysts (including cerium oxide catalysts) can proceed via the Mars and van Krevelen mechanism in which the key steps are the supply of oxygen by the reducible oxide, the introduction of the oxygen species from the lattice oxide into the substrate molecule, and the re-oxidation of the reduced solid by the oxygen-containing gaseous phase, the rate-determining step of the reaction (Menezo et al, 1993;Todorova et al, 2012). According to Todorova et al (2009), the oxygen storage capacity of cerium oxide is associated with a fast Ce 4+ /Ce 3+ redox process, making more oxygen available for the oxidation process.…”