Phase Composition and Catalytic Properties of MnNaW/SiO2 Oxide System in Oxidative Conversion of Methane

Abstract

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.