Synthesis, Characterization of Magnetic Composites and Testing of Their Activity in Liquid-Phase Oxidation of Phenol with Oxygen

Abstract

The development and improvement of methods for the synthesis of environmentally friendly catalysts based on base metals is currently an urgent and promising task of modern catalysis. Catalysts based on nanoscale magnetite and maghemite have fast adsorption–desorption kinetics and high chemical activity. The purpose of this work is to obtain magnetic composites, determine their physicochemical characteristics and verify their activity in the process of liquid-phase oxidation of phenol with oxygen. Magnetic nanocomposites were obtained by chemical co-deposition of salts of ferrous and trivalent iron. The synthesized magnetic composites were studied by X-ray diffractometry, energy dispersive X-ray fluorescence and Mössbauer spectroscopy, IR-Fourier spectroscopy and elemental analysis. To increase the catalytic activity in oxidative processes, the magnetite surfaces were modified using cobalt nitrate salt. Further, CoFe2O4 was stabilized by adding polyethylenimine (PEI) as a surfactant. Preliminary studies of the oxidation of phenol with oxygen, as the most typical environmental pollutant were carried out on the obtained Fe3O4, CoFe2O4, CoFe2O4/PEI catalysts. The spectrum of the reaction product shows the presence of CH in the aromatic ring and double C=C bonds, stretching vibrations of the C=O groups of carbonyl compounds; the band at 3059 cm−1 corresponds to the presence of double C=C bonds and the band at 3424 cm−1 to hydroquinone compounds. The band at 1678 cm−1 and the intense band at 1646 cm−1 refer to vibrations of the C=O bonds of the carbonyl group of benzoquinone. Peaks at 1366 cm−1 and 1310 cm−1 can be related to the vibrations of C–H and C–C bonds of the quinone ring. Thus, it was demonstrated that produced magnetic composites based on iron oxide are quite effective in the oxidation of phenol with oxygen.

Catalysts Based on Nanoscale Iron and Cobalt Immobilized on Polymers for Catalytic Oxidation of Aromatic Hydrocarbons: Synthesis, Physico-Chemical Studies, and Tests of Catalytic Activity

“…The X-ray diffraction pattern of the synthesized Fe 3 O 4 (Figure 2a) proves the crystal structure of magnetite, and the peaks in the diffraction pattern at 35 • /43 • /57 • /63 • /74 • correspond to the lattice planes (311), (400), ( 422 Also, a detailed description of the methodology for obtaining catalysts and equipment for physical and chemical research is described in our previous articles [16,45].…”

“…The synthesized nanocomposites of composition, Fe 3 O 4 , CoFe 2 O 4 and CoFe 2 O 4 /PEI, were tested in the oxidation reaction of phenol with oxygen (C phenol = 0.003 mol/L) [45]. The UV spectrum of the sample during the reaction and the IR spectra of phenol and reaction products after oxidation with oxygen showed a favorable prognosis for the use of such catalysts in the production of oxygen-containing compounds using the catalytic reaction of oxidation with oxygen.…”

“…The formation of magnetite occurs through an intermediate stage of formation of ferrihydrite. The advantages of this method are high product yield, narrow distribution of nanoparticles in size, and resistance to aggregation and sedimentation [13,23,32,[39][40][41][42][43][44][45][46][47][48]. Co-precipitation occurs in two stages: first, the nucleation of crystals (when critical supersaturation is reached) occurs; the second stage is the slow growth of embryos through the process of diffusion of dissolved substances to the crystal surface.…”

“…The wavelength can vary in the range from 190 to 1100 nm. Also, a detailed description of the methodology for obtaining catalysts and equipment for physical and chemical research is described in our previous articles [16,45].…”

Catalysts Based on Iron Oxides for Wastewater Purification from Phenolic Compounds: Synthesis, Physicochemical Analysis, Determination of Catalytic Activity

“…Therefore, it is quite difficult to ensure highly effective purification from phenol compounds in most enterprises. The search for catalysts for the oxidation of organic substances in aqueous solutions is an urgent task [40][41][42][43][44][45][46][47][48][49][50][51][52][53][54][55].…”