Nanodispersed Co/SiO2 catalyst: preparation and characterization

Silicon cobalt mixed oxide samples, with three different molar compositions: 10Co∙90SiO2 (10Co), 20Co∙80SiO2 (20Co) and 30Co∙70SiO2 (30Co), were synthesized using a modified sol-gel method. The materials were characterized by DTA measurements, X-ray diffraction (XRD), N2 adsorption/desorption isotherms, TPR measurements and FTIR spectra of samples exposed to NO. It was found that the nature of cobalt oxide species and their interactions with silica matrix depended on the cobalt content. No cobalt oxides were observed in 10Co sample, while Co3O4 was present as a segregated phase in the samples at higher cobalt loadings. TPR showed that 10Co sample was reduced in negligible amount, while the 20Co and 30Co gave different signals due to the presence of Co3O4 and Co2+ species more strongly bonded to silica. FT-IR spectra recorded after NO adsorption at different temperatures showed two types of weak Lewis acid sites due to surface Co2+ and probably Co3+.N2 adsorption-desorption measurements indicated that micropore and mesopore volumes were affected by the Co content