Mesoporous Core–Shell Fenton Nanocatalyst: A Mild, Operationally Simple Approach to the Synthesis of Adipic Acid

Abstract

Mesoporous nanoparticles composed of γ-Al2O3 cores and α-Fe2O3 shells were synthesized in aqueous medium. The surface charge of γ-Al2O3 helps to form the core–shell nanocrystals. The core–shell structure and formation mechanism have been investigated by wide-angle XRD, energy-dispersive X-ray spectroscopy, and elemental mapping by ultrahigh-resolution (UHR) TEM and X-ray photoelectron spectroscopy. The N2 adsorption–desorption isotherm of this core–shell materials, which is of type IV, is characteristic of a mesoporous material having a BET surface area of 385 m2 g(−1) and an average pore size of about 3.2 nm. The SEM images revealed that the mesoporosity in this core–shell material is due to self-aggregation of tiny spherical nanocrystals with sizes of about 15–20 nm. Diffuse-reflectance UV/Vis spectra, elemental mapping by UHRTEM, and wide-angle XRD patterns indicate that the materials are composed of aluminum oxide cores and iron oxide shells. These Al2O3@Fe2O3 core–shell nanoparticles act as a heterogeneous Fenton nanocatalyst in the presence of hydrogen peroxide, and show high catalytic efficiency for the one-pot conversion of cyclohexanone to adipic acid in water. The heterogeneous nature of the catalyst was confirmed by a hot filtration test and analysis of the reaction mixture by atomic absorption spectroscopy. The kinetics of the reaction was monitored by gas chromatography and 1H NMR spectroscopy. The new core–shell catalyst remained in a separate solid phase, which could easily be removed from the reaction mixture by simple filtration and the catalyst reused efficiently.

Core–shell nanoparticles: synthesis and applications in catalysis and electrocatalysis

“…379 The most common industrial process for its synthesis involves nitric acid oxidation of cyclohexanol or cyclohexanol-cyclohexanone mixtures. Bhaumik and co-workers have reported mesoporous, crystalline Al 2 O 3 @Fe 2 O 3 CSNs via a new synthetic approach in aqueous medium 381 utilizing the negative charges on the surface of g-Al 2 O 3 for the formation of the CSNs. Bhaumik and co-workers have reported mesoporous, crystalline Al 2 O 3 @Fe 2 O 3 CSNs via a new synthetic approach in aqueous medium 381 utilizing the negative charges on the surface of g-Al 2 O 3 for the formation of the CSNs.…”

Mesoporous materials: versatile supports in heterogeneous catalysis for liquid phase catalytic transformations

“…The advantage of choosing mesoporous silica as support for incorporating other foreign atoms or functionalities is the inertness of the inorganic silica walls, where tetravalent Si atom can be replaced by the other reactive metal centers retaining considerably good surface area and porosity. 10 Adipic acid is a industrially important dicarboxylic acid, which can be produced exclusively from catalytic oxidation of cyclohexane, cyclohexene or cyclohexanone over mesoporous materials like WO 3 /SiO 2 , 51 and core-shell Fenton catalyst (Fe 2 O 3 /Al 2 O 3 ), 52 respectively in presence of H 2 O 2 oxidant. In Figure 3 step by step formation of adipic acid from these hydrocarbons are shown.…”

Investigating the Role of Boron Doping in Enhancing the Catalytic Activityof Aematite for Fenton Oxidative Treatment of Tannery Wastewater:Parameters Optimisation through Response Surface Methodology

“…Thus Luo et al reported that the heterogeneous Fenton degradation rate of Rhodamine B using nano particle BiFeO 3 catalyst was about 20 times higher than that obtained with Fe 3 O 4 at pH of 5 at 25°C [12]. Xu and Wang [11] found that the removal rate of 4-chlorophenol in a heterogeneous Fenton reaction was 100% for CeO 2 /Fe 3 O 4 composite catalyst after 120 minutes at a pH of 3, compared with only 5% and 21% for CeO 2 and Fe 3 O 4 catalysts, respectively. Other metals that were incorporated into iron based Fenton catalysts include; Mo (Tian et al), Al (Patra et al) and Ti (Zhong et al) [13][14][15].…”

“…Having unique properties including high adsorptive and catalytic activities, iron oxides can be manipulated to achieve special physical and chemical structures in order to bring added advantages to the target reactions [9]. Many solid catalysts containing iron like Fe, Fe 2 O 3 , Fe 3 O 4 and FeOOH have demonstrated to be effective in heterogeneous Fenton treatment of various organic pollutants in water [10,11]. In order to enhance their catalytic abilities for decomposing H 2 O 2 to yield powerful radicals other elements are incorporated into iron-containing particles.…”