Control of the Interphases Formation Degree in Co3O4/ZnO Catalysts

ZnO supported Co3O4 nanoparticles are highly active in the transformation of renewable materials through carbonylation of glycerol with urea. The activity of the nanoparticles is modulated by their interaction with the ZnO support, which remarkably depends on the impregnation method. One catalyst series was impregnated by conventional impregnation of a ZnO support with an aqueous solution of Co(NO3)26(H2O), while the second set was obtained using a novel room-temperature low-energy dry nanodispersion method. This work focuses on the characterization and catalytic activity of both series of catalysts and describes the nature of the active sites required for the carbonylation of glycerol with urea. Raman spectroscopy and HRTEM were used to proof the nature of the interphase interaction between ZnO and Co3O4 particles in both catalyst series. Thus, it was verified such interphases are present in the catalysts prepared through the dry mixing method. Co3O4/ZnO system prepared with the dry mixing method at room temperature exhibited a catalytic behavior in the production of glycerol carbonate reaching conversion values up to 69% in 4h affording nearly total selectivity. There was a clear correlation between the amount of the phase and the catalytic activity. Therefore, the catalytic activity can be tuned by controlling interphase formation in Co3O4/ZnO catalysts. Upon thermal treatment, both series rearranged into inactive phases such as ZnxCo1-xCo2O4, decreasing the number of free Co3O4 related sites, which decreased the catalytic activity. Therefore, the preparation stage of the Co3O4/ZnO catalysts played an important role in the formation of this phase.