Selective glycerol conversion to lactic acid on Co3O4/CeO2 catalysts

Cerium oxide supported Co3O4 particles obtained through using the deposition-precipitation or impregnation methods and calcination at 400 degrees C, are used as catalysts on the glycerol oxidation in aqueous basic medium at 250 degrees C for obtaining lactic acid. The results demonstrate that Co3O4/CeO2 catalysts are active on the selective conversion of glycerol to lactic acid. The glycerol conversion and lactic acid selectivity are significantly dependent on the preparation method of the Co3O4/CeO2 catalyst, reaching a lactic acid selectivity of 79.8% at a glycerol conversion of 85.7% on the catalyst obtained using the impregnation method, while on the catalyst obtained using the deposition-precipitation method, 69% lactic acid selectivity at 74.4% glycerol conversion are reached. Characterization of the Co3O4/CeO2 catalysts using XRD, TEM, EDX and Raman spectroscopy indicates that Co3O4 particles obtained through using the impregnation method are highly dispersed and rather homogeneously distributed on the support surface while for the deposition method, TEM and EDX analyses show that Co3O4 particles can be observed separated from the support surface. The SEM-EDS analyses show the presence of no uniform sized Co3O4 particles on the CeO2 surface of both catalysts. TPR characterization suggests that Co3O4 particles interaction with CeO2 surface depends on the preparation method. The characterization of the catalysts indicates that highly dispersed crystalline cobalt oxide particles in close interaction with the CeO2 support surface might create a synergetic effect for selectively oxidizing glycerol to lactic acid.