Catalytic activity of cobalt grafted on ordered mesoporous silica materials in N2O decomposition and CO oxidation

Abstract

Three different ordered mesoporous silica materials, such as MCM-41, Al incorporated into the silica framework MCM-41 (mass ratio Si/Al = 9) and SBA-15, were prepared. Furthermore, aluminum was grafted on the surface of MCM-41 (mass ratio Si/AI =16) and SBA-15 (mass ratio Si/Al= 23) by the molecular designed dispersion (MDD) method. In a next step, cobalt (Co =10-12 wt%), as an active metal for redox reactions, was introduced by the MDD technique. The prepared catalysts were characterized by atomic absorption spectroscopy, microwave plasma-atomic emission spectroscopy, N-2 physisorption, thermogravimetric analysis, X-ray diffraction, diffuse reflectance UV-vis spectroscopy, infrared and Raman spectroscopies, transmission electron microscopy, temperature programmed reduction by hydrogen and their catalytic properties were evaluated for two model reactions: N2O decomposition and CO oxidation. All prepared catalysts showed poor activity in the reaction of N2O decomposition and the use of reducing agent (carbon monoxide) improved it only little. Contrary to this, all catalysts were significantly more active for CO oxidation by oxygen. The highest activity was reached over the SBA + Co catalyst which is proposed to be due to the smallest size of tetrahedral Co(II) species on SBA-15 silica support.