MnNaW/SiO 2 oxide system based on a mesoporous silica matrix synthesized using tetraethoxysilane and cetyltrimethylammonium bromide as precursors were prepared and characterized by SEM/EDS, XRD, EPR, N 2 adsorption-desorption measurements and studied in the oxidative conversion of methane (OCM). It is shown that MnNaW/SiO 2 catalyst consists of MnO x , Na 2 WO 4 , MnWO 4 , and SiO 2 phases. At the reaction temperature of 750-850°C the molten Na 2 WO 4 phase covers the surface of crystalline SiO 2 , and the interaction of MnO x , Na 2 WO 4 and SiO 2 matrix forms "liquid glass". It is assumed that Na 1-y MnO x particles formed as a result of the interaction of the system components during catalyst formation and characterized by the presence of ion-radical lattice oxygen are catalytically active sites in the OCM process.
The well-known MnNaW catalysts based on SiO2 for oxidative condensation of methane (OCM) were synthesized by various methods, characterized by X-ray diffractometry (XRD), scanning electron microscopy with energy dispersive elemental analysis (SEM/EDX), electron magnetic resonance (EMR) spectroscopy, N2 adsorption-desorption measurements, and tested as OCM catalysts at atmospheric pressure to convert into a mixture of ethylene + carbon oxides for further hydroformylation to propylene. The structural and catalytic features of the synthesized systems are discussed. The necessity of using mainly X-ray diffraction, Raman, and EMR methods for studying catalysts in situ mode in combination with online MS analysis of gasphase reaction products to establish the nature of catalytically active phases, centers, their mechanism of functioning, activation of CH4 with the formation of C-C bond for the synthesis of hydrocarbons C2 and C2+ is considered. Keywords: oxidative conversion of methane, NaMnW/SiO2 catalyst, ethylene-carbon monoxide mixture, magnetic, texture properties
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