Waste eggshells to valuable Co3O4/CaCO3 materials as efficient catalysts for VOCs oxidation

Abstract

Transition metal oxides have excellent catalytic activities for the oxidation of VOCs, in which it is necessary to find new catalysts/supports with cheap and environmentally-friendly properties. Herein, Co3O4 nanoparticles decorated eggshell catalysts were firstly synthesized via impregnation method, where the waste eggshell is used as an effective hard template and an excellent support with porous structure. A series of Co3O4/Eggshell catalysts were synthesized by changing the different concentration of precursors (different Co3O4 loadings), which were defined as Co3O4/Eggshell-1 (33.1 %), Co3O4/Eggshell-2 (16.7 %) and Co3O4/Eggshell-3 (9.1 %) catalysts. Among of them, the Co3O4/Eggshell-2 exhibited the best activity with the temperature T90 % = 256 ℃, which is about 90 °C lower than Co3O4/oyster shell-2 (benzene catalytic oxidation). And the catalytic activity of Co3O4/Eggshell is remarkably improved as compared to commercially pure Co3O4 nanoparticles and commercially CaCO3. The excellent activity can be attributed to the unique structure of the eggshell and the interaction of CaCO3 and Co3O4. In addition, the catalyst has also showed long-term stability. Moreover, the reaction mechanism of benzene catalytic oxidation was further revealed by in-situ FTIR studies.