Structure–activity correlation in aerobic cyclohexene oxidation and peroxide decomposition over Co_xFe_3−xO₄ spinel oxides

Abstract

Nanoparticulate CoxFe3-xO4 (0 ≤ x ≤ 3) catalysts were prepared by spray-flame synthesis and applied in liquid phase cyclohexene oxidation with O2 as oxidant. The catalysts were characterized in detail...

LaCo1–xFexO3 Nanoparticles in Cyclohexene Oxidation

“…The LaCo 1– x Fe x O 3 nanoparticles are used for cyclohexene oxidation leading to moderate degrees of conversion between 30 and 35% after 8 h for the LaCoO 3 and LaCo 0.5 Fe 0.5 O 3 samples, whereas the LaFeO 3 samples exhibit only low cyclohexene conversions of about 10%, which is comparable to the blank activity in the absence of any catalyst, which is shown in Figure (conversions and product selectivities are provided in Supporting Information Table S7). Thus, LaFeO 3 samples do not show a catalytic activity toward cyclohexene oxidation, and the substitution of Fe by Co strongly accelerates the reaction as expected from other studies of liquid-phase oxidation reactions. , Mass transfer limitations were excluded by additional experiments with different stirring speeds as shown previously. ,, For all samples, the reactor temperature during the synthesis of the nanoparticles does not have a strong effect, as similar degrees of cyclohexene conversion were obtained for all catalyst pairs.…”

“…40,41 Mass transfer limitations were excluded by additional experiments with different stirring speeds as shown previously. 20,42,43 For all samples, the reactor temperature during the synthesis of the nanoparticles does not have a strong effect, as similar degrees of cyclohexene conversion were obtained for all catalyst pairs. The nanoparticles are collected after the aerobic cyclohexene oxidation, and their transition metal-edge spectra are recorded again (EXAFS spectra and Fourier transformed spectra are provided in the Supporting Information Figures S12 and S13).…”

Concepts of Heterogeneously Catalyzed Liquid‐Phase Oxidation of Cyclohexene with tert‐Butyl Hydroperoxide, Hydrogen Peroxide and Molecular Oxygen

“…Herein, the proposed heterolytic activation of O 2 and the consecutive homolytic decomposition of the formed hydroperoxide intermediate over Co 2+ /Co 3+ redox pairs can be assumed (Scheme 2). This assumption can also be supported by several studies on Co‐containing oxide nanocatalysts by Peng and coworkers, [10a,19,20,26] in which Co 3+ species were found to be the active sites for O 2 activation, [26] whereas Co 2+ cations were essential for the catalytic decomposition of 2‐cyclohexene‐1‐hydroperoxide [9] . These Co‐based catalysts enabled moderate to high cyclohexene conversions between 62 and 79 % with moderate product selectivities of 27 to 47 % to the main product 2‐cyclohexene‐1‐one (Figure 1, green columns) and leaching of the active Co species was excluded by ICP‐MS measurements identifying the reaction to occur heterogeneously [9] .…”

“… Comparison of the catalytic activity of different transition metal‐based catalysts towards heterogeneously catalyzed cyclohexene oxidation using molecular O 2 as oxidizing agent [7,10a,13–25] . The degree of cyclohexene conversion is shown as columns, while the obtained selectivity to the main product of the reaction is presented as black square.…”

Cobalt ferrite magnetic nanoceramics as an efficient nanocatalyst for the oxidation of olefins in the presence of molecular O2 as an environmentally safe oxidant

“…[3][4][5][6][7][8] Among magnetic nanoceramics, spinel ferrites, especially cobalt and iron compounds, are of great catalytic importance. 9,10 The spinel ferrites play a significant role in many reactions, such as oxidative hydrogenation of hydrocarbons, selective oxidation of carbon monoxide, decomposition of alcohols, and oxidation of olefins. 11 The catalytic properties of ferrospinels are related to the expansion of the cation among the tetrahedral and octahedral sites of the spinel structures.…”