Support effect in Co3O4-based catalysts for selective partial oxidation of glycerol to lactic acid

Co3O4 supported on CeO2, ZrO2 and TiO2, were used as catalysts in glycerol partial oxidation to lactic acid. The aim was to establish the influence of the support on the cobalt-derived catalysts activity. The most active catalyst based on TOF followed the order: Co3O4/CeO2 (1.2 × 10−1 s−1) > Co3O4/ZrO2 (8.3 × 10-2 s−1) > Co3O4/TiO2 (3.0 × 10-2 s−1), with lactic acid selectivity at comparable glycerol conversion (53.5 ± 5.5 %) being higher when using CeO2 support, Co3O4/CeO2 (90 %) > Co3O4/ZrO2 (78 %) > Co3O4/TiO2 (68 %). These results indicated that the support type not only influenced activity but also selectivity to lactic acid. The Co3O4/CeO2 catalyst with less exposed cobalt species at the surface enriched in Co3+ ions, a more homogeneous composition of cobalt species being reduced at low temperatures, with acid sites of middle strength and lower density of acidic sites, is at the origin of a greater selectivity towards lactic acid, in addition this catalyst was active in 4 catalytic cycles.